Patent Publication Number: US-2023157727-A1

Title: Systems and methods for joint replacement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation from U.S. patent application Ser. No. 17/112,016, filed Dec. 4, 2020, which is a continuation from U.S. patent application Ser. No. 16/229,477, filed Dec. 21, 2018, which is a continuation from U.S. patent application Ser. No. 15/794,351, filed Oct. 26, 2017, which is a continuation from U.S. patent application Ser. No. 15/402,574, filed Jan. 10, 2017, which is a divisional of U.S. patent application Ser. No. 14/949,525, filed Nov. 23, 2015, which is a continuation from U.S. patent application Ser. No. 14/570,889, filed Dec. 15, 2014, which is a continuation from U.S. patent application Ser. No. 12/626,162, filed Nov. 25, 2009, which is a continuation from U.S. patent application Ser. No. 12/509,414, filed Jul. 24, 2009, which claims benefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 61/102,754, filed Oct. 3, 2008, U.S. Provisional Patent Application No. 61/135,863, filed Jul. 24, 2008, U.S. Provisional Patent Application No. 61/102,767, filed Oct. 3, 2008, U.S. Provisional Patent Application No. 61/155,093, filed Feb. 24, 2009, U.S. Provisional Patent Application No. 61/104,644, filed Oct. 10, 2008, U.S. Provisional Patent Application No. 61/153,268, filed Feb. 17, 2009, U.S. Provisional Patent Application No. 61/153,257, filed Feb. 17, 2009, U.S. Provisional Patent Application No. 61/153,255, filed Feb. 17, 2009, U.S. Provisional Patent Application No. 61/173,158, filed Apr. 27, 2009, U.S. Provisional Patent Application No. 61/187,632, filed Jun. 16, 2009, and U.S. Provisional Patent Application No. 61/173,159, filed Apr. 27, 2009, each of which is incorporated in its entirety by reference herein. 
    
    
     BACKGROUND OF THE INVENTIONS 
     Field of the Inventions 
     The present application is directed to systems and methods for joint replacement, in particular to systems and methods for knee joint replacement which utilize a surgical orientation device or devices. 
     Description of the Related Art 
     Joint replacement procedures, including knee joint replacement procedures, are commonly used to replace a patient&#39;s joint with a prosthetic joint component or components. Such procedures often use a system or systems of surgical tools and devices, including but not limited to cutting guides (e.g. cutting blocks) and surgical guides, to make surgical cuts along a portion or portions of the patient&#39;s bone. 
     Current systems and methods often use expensive, complex, bulky, and/or massive computer navigation systems which require a computer or computers, as well as three dimensional imaging, to track a spatial location and/or movement of a surgical instrument or landmark in the human body. These systems are used generally to assist a user to determine where in space a tool or landmark is located, and often require extensive training, cost, and room. 
     Where such complex and costly system are not used, simple methods are used, such “eyeballing” the alignment of rods with anatomical features, such as leg bones. These simple methods are not sufficiently accurate to reliably align and place implant components and the bones to which such components are attached. 
     SUMMARY OF THE INVENTIONS 
     Accordingly, there is a lack of devices, systems and methods that can be used to accurately position components of prosthetic joints without overly complicating the procedures, crowding the medical personnel, and/or burdening the physician of health-care facility with the great cost of complex navigation systems. 
     In accordance with at least one embodiment, a surgical orientation device for use in a total knee arthroplasty procedure having an associated three-dimensional coordinate reference system can comprise a portable housing configured to connect to a knee bone by way of one or more orthopedic fixtures, a sensor located within the housing, the sensor configured to monitor the orientation of the housing in the three-dimensional coordinate reference system, the sensor further configured to generate orientation data corresponding to the monitored orientation of the surgical orientation device, and wherein the sensor comprises a multi-axis accelerometer. The surgical orientation device can further comprise a display module configured to display one or more angle measurements corresponding to an offset from a flexion-extension angle or a varus-valgus angle of a mechanical axis of the knee joint, and wherein the sensor can be oriented relative to the housing at an acute angle to maximize the sensitivity of the sensor when coupled to a tibia or a femur. 
     In accordance with another embodiment, an orthopedic orientation system for use in a joint procedure can comprise an orthopedic fixture adapted to be coupled with a knee bone and to be adjustable in multiple degrees of freedom, and a surgical orientation device having an associated three-dimensional coordinate reference system. The device can comprise a portable housing configured to connect to a knee bone by way of the orthopedic fixtures, and a sensor located within the housing, the sensor configured to monitor the orientation of the housing in the three-dimensional coordinate reference system, the sensor further configured to generate orientation data corresponding to the monitored orientation of the surgical orientation device. The surgical orientation device can further comprise an output device configured to inform a user of the orientation of the device relative to a reference plane corresponding to a mechanical axis of the joint, and wherein the sensor can be configured for optimum sensitivity in the range of motion of the orthopedic fixture. 
     In accordance with at least one embodiment, an orthopedic system for orienting a cutting plane during a joint replacement procedure can comprise a base member attachable to an anterior face of a tibia, at least one adjustment device connected to and moveable relative to the base member, and at least one probe for referencing a plurality of anatomical landmarks, the anatomical landmarks referencing a mechanical axis of the leg. The at least one adjustment device can be moveable in at least one degree of freedom so as to orient a cutting guide relative to a proximal feature of the tibia, such that the cutting guide is oriented at a selected angle relative to the mechanical axis. 
     In accordance with at least one embodiment, an interactive user interface for aiding a user in performing an orthopedic procedure can be provided, wherein the user interface is displayed on a display associated with a surgical orientation device configured to monitor the orientation of the surgical orientation device in a three-dimensional coordinate reference system and wherein the user interface is configured to perform acts comprising showing the user steps to be performed in the identified orthopedic procedure and guiding the user in performance of the steps. Guiding the user can comprise displaying one or more instructive images related to a first step to be performed in the identified orthopedic procedure, prompting the user to press a user input after performing the first step of the identified orthopedic procedure, receiving a confirmation from the user that the first step of the identified procedure has been performed, and displaying one or more instructive images related to the second step to be performed in the identified orthopedic procedure. 
     In accordance with another embodiment, a monitoring system can be provided for monitoring an orientation of a surgical orientation device having an associated three-dimensional coordinate reference system during an orthopedic procedure, the orientation system comprising a display having a window and an on-screen graphic, displayed in the window and representing one or more orientation measurements corresponding to an orientation of the surgical orientation device about one or more axes of the three-dimensional coordinate reference system, the one or more orientation measurements generated by a processor. 
     In accordance with at least one embodiment, a method for preparing a proximal portion of a tibia for receiving a knee implant can comprise coupling an orthopedic fixture with a proximal feature of the patient&#39;s leg, connecting a portable surgical orientation device to an adjustment device that is connected to the orthopedic fixture and moveable relative to the leg, moving the adjustment device to move the portable surgical orientation device in response to a prompt from the portable surgical orientation device to orient the orthopedic fixture relative to a mechanical axis of the leg. 
     In accordance with another embodiment, a method for performing total knee arthroplasty on a knee joint of a patient can comprise preparing a proximal portion of a tibia for receiving a knee implant, including coupling an orthopedic fixture with a proximal portion of the patient&#39;s tibia, connecting a portable surgical orientation device to a moveable portion of the orthopedic fixture, moving the moveable portion of the orthopedic fixture to move the portable surgical orientation device in response to a prompt from the portable surgical orientation device to orient a cutting guide at an intended orientation relative to a mechanical axis of the leg, and resecting the proximal tibia along the cutting guide to define a tibial plateau. The method can further comprise preparing a distal portion of a femur for receiving a knee implant, including coupling an orthopedic fixture and the portable surgical orientation device with an anterior surface of a distal portion of the femur, moving at least one of the femur and the tibia in response to a prompt from the portable surgical orientation device to align the femur with the mechanical axis of the leg, securing a cutting guide with an anterior feature of the femur such that the guide is substantially perpendicular to the mechanical axis, and resecting the distal femur. 
     In accordance with another embodiment, a method of performing an orthopedic procedure can comprise coupling an orthopedic fixture and the portable surgical orientation device with a distal portion of a limb that comprises a portion of a ball-and-socket joint, the portable surgical orientation device including a housing enclosing a sensor and a microprocessor. The method can further comprise activating the sensor within the portable surgical orientation device, such that the sensor outputs a signal indicative of orientation, collecting positional information of the portable surgical orientation device; and determining the location of the mechanical axis of the limb based on the positional information collected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows a representation of a human leg, identifying the femoral head, knee joint, femur, tibia, and ankle; 
         FIG.  2 A  is a perspective view of a tibial preparation system according to one embodiment that can be used in connection with preparation of an aspect of a knee joint during a knee joint replacement procedure; 
         FIG.  2 B  is a perspective view of another tibial preparation system according to one embodiment that can be used in connection with preparation of an aspect of a knee joint during a knee joint replacement procedure; 
         FIG.  3 A  is a perspective view of a first arrangement of another tibial preparation system according to one embodiment that can be used in connection with preparation of an aspect of a knee joint during a knee joint replacement procedure; 
         FIG.  3 B  is a perspective view of a second arrangement of the tibial preparation system of  FIG.  3 A ; 
         FIG.  4 A  is a perspective view of a first arrangement of another tibial preparation system according to one embodiment that can be used in connection with preparation of an aspect of a knee joint during a knee joint replacement procedure; 
         FIG.  4 B  is a perspective view of a second arrangement of the tibial preparation system of  FIG.  4 A ; 
         FIG.  5    is a perspective view of femoral preparation system according to one embodiment that can be used in connection with preparation of an aspect of a knee joint during a knee joint replacement procedure; 
         FIG.  6    is a perspective view of a femoral preparation and knee distraction system according to one embodiment that can be used in connection with preparation of an aspect of a knee joint during a knee joint replacement procedure; 
         FIG.  7    is a perspective view of a surgical orientation device according to one embodiment that can be used for orienting a resection plane or planes; 
         FIG.  8    is a back view of the surgical orientation device of  FIG.  7   ; 
         FIG.  9    is a perspective view of the surgical orientation device of  FIG.  7   ; 
         FIG.  10 A  is a top view of the surgical orientation device of  FIG.  7   ; 
         FIG.  10 B  is a bottom view of the surgical orientation device of  FIG.  7   ; 
         FIG.  11    is a block diagram of an electrical system of the surgical orientation device of  FIG.  7   ; 
         FIGS.  12 A- 12 C  illustrate operation of accelerometers according to embodiments that can be used as sensors in the electrical system of  FIG.  11   ; 
         FIG.  12 D  is a perspective view of interior components of the surgical orientation device of  FIG.  7   ; 
         FIG.  12 E  is a flow chart of an embodiment of an orientation measurement process performed by the surgical orientation device of  FIG.  7   ; 
         FIG.  12 F  is a side view of a left leg of a patient illustrating an orientation reference frame; 
         FIG.  13    is a perspective view of a surgical orientation device according to another embodiment; 
         FIG.  14    is a perspective view of a coupling device according to one embodiment that can be used to connect the surgical orientation device of  FIG.  7    to other components; 
         FIG.  15    is a perspective view an outer housing of the coupling device of  FIG.  14   ; 
         FIG.  16    is a perspective view of interior components of the coupling device of  FIG.  14   ; 
         FIG.  17    is a plan view of the coupling device of  FIG.  14   ; 
         FIG.  17 A  is an exploded view a coupling device according to another embodiment; 
         FIG.  18    is a perspective view of an orthopedic fixture according to one embodiment which can be used as a universal jig; 
         FIG.  19    is an exploded view of the orthopedic fixture of  FIG.  18   ; 
         FIG.  20    is a perspective view of a set of target probes according to one embodiment which can be used in conjunction with the orthopedic fixture of  FIG.  18   ; 
         FIG.  21 A  is a perspective view of the tibial preparation system of  FIG.  2 A  attached to the tibia; 
         FIG.  21 B  is a perspective view of a tibial preparation system, as modified from the tibial preparation system of  FIG.  2 A , emitting laser light onto a target probe; 
         FIG.  22 A  is a perspective view of the tibial preparation system of  FIG.  2 B ; 
         FIG.  22 B  is a side view of the tibial preparation system of  FIG.  2 B ; 
         FIG.  22 C  is a perspective view of the tibial preparation system of  FIG.  2 B , without a surgical orientation device attached; 
         FIG.  23 A  is a perspective view of a tibial preparation system, as modified from the tibial preparation system of  FIG.  2 B , showing measuring devices; 
         FIG.  23 B  is a perspective view of the tibial preparation system of  FIG.  23 A  being used to reference an anatomical landmark; 
         FIG.  24    is a perspective view of a landmark acquisition assembly according to one embodiment that can be used in the tibial preparation system of  FIG.  3 A ; 
         FIGS.  25 A-B  are perspective views of a primary and secondary rod of the landmark acquisition assembly of  FIG.  24   ; 
         FIG.  26    is a front view of a connecting element of the landmark acquisition assembly of  FIG.  24   ; 
         FIG.  27    is a perspective view of the second arrangement of the tibial preparation system of  FIG.  3 B , showing an extramedullary alignment guide according to one embodiment that can be used along the anterior side of the tibia; 
         FIGS.  28  and  29    are perspective views of the first arrangement of the tibial preparation system of  FIG.  3 A  during a knee joint replacement procedure; 
         FIGS.  30 - 36 B  are perspective views of the second arrangement of the tibial preparation system of  FIG.  3 B  during a knee joint replacement procedure; 
         FIG.  37    is a perspective view of a cutting block and a cutting tool being used to resect a portion of the proximal tibia; 
         FIG.  38    is a perspective view of the tibial preparation system of  FIG.  4 B  during a knee joint replacement procedure; 
         FIG.  39    is a perspective view of a the second arrangement of the tibial preparation system of  FIG.  4 B   
         FIG.  40    is a perspective view of an orthopedic fixture according to one embodiment which can be used in the femoral preparation system of  FIG.  5   ; 
         FIG.  41    is an exploded view of the orthopedic fixture of  FIG.  40   ; 
         FIG.  42    is a perspective view of the femoral preparation system of  FIG.  5    during a stage of a knee joint replacement procedure; 
         FIG.  43    is a perspective view of the femoral preparation system of  FIG.  5    during another stage of a knee joint replacement procedure; 
         FIG.  44    is a perspective view of a distraction device according to one embodiment which can be used in the femoral preparation system of  FIG.  6   ; 
         FIG.  45    is a side view of the distraction device of  FIG.  44   ; 
         FIG.  46    is a top view of the distraction device of  FIG.  44   ; 
         FIG.  47    is a partial perspective view of a portion of the distraction device of  FIG.  44   ; 
         FIG.  48    is a perspective view of a portion of the distraction device of  FIG.  44   ; 
         FIGS.  49 A-B  are anterior views of the femoral preparation system of  FIG.  5    being used to distract a knee joint with visual guidance using a visual indicator, such as a laser; 
         FIG.  50 A  is an anterior view of the femoral preparation system of  FIG.  5    after the knee has been distracted; 
         FIG.  50 B  is an anterior view of the femoral preparation system of  FIG.  5    after the knee has been distracted; 
         FIG.  51 A  is a perspective view of a first pin being inserted into an opening in the femoral preparation system of  FIG.  5   ; 
         FIG.  51 B  is a perspective view of a second pin being inserted into an opening in the femoral preparation system of  FIG.  5   ; 
         FIG.  52    is a perspective view of a cutting block and a cutting tool being used to resect a portion of the distal femur; 
         FIG.  53    is an anterior view of the femoral preparation system of  FIG.  5    being used to distract a knee joint with visual guidance using a visual indicator, such as a laser; 
         FIG.  54    is an anterior view of the femoral preparation system of  FIG.  5    being used to distract a knee joint with visual guidance using a visual indicator, such as a laser; 
         FIG.  55    is an anterior view of the femoral preparation system of  FIG.  5    being used to distract a knee joint with visual guidance using a visual indicator, such as a laser; 
         FIG.  56    is a perspective view of the femoral preparation system of  FIG.  5    after the knee has been distracted; 
         FIG.  57    is a perspective view of a cutting block which can be used to resect the distal femur; 
         FIGS.  58 A- 61 K  show screen displays generated by one embodiment of the interactive user interface of the surgical orientation device of  FIG.  7   . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although certain preferred embodiments and examples are disclosed below, it will be understood by those skilled in the art that the inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention, and to obvious modifications and equivalents thereof. Thus it is intended that the scope of the inventions herein disclosed should not be limited by the particular disclosed embodiments described below. Thus, for example, in any method or process disclosed herein, the acts or operations making up the method/process may be performed in any suitable sequence, and are not necessarily limited to any particular disclosed sequence. For purposes of contrasting various embodiments with the prior art, certain aspects and advantages of these embodiments are described where appropriate herein. Of course, it is to be understood that not necessarily all such aspects or advantages may be achieved in accordance with any particular embodiment. Thus, for example, it should be recognized that the various embodiments may be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may be taught or suggested herein. 
     In addition, in the following description of the invention, a “module” includes, but is not limited to, software or hardware components which perform certain tasks. Thus, a module may include object-oriented software components, class components, procedures, subroutines, data structures, segments of program code, drivers, firmware, microcode, circuitry, data, tables, arrays, etc. Those with ordinary skill in the art will also recognize that a module can be implemented using a wide variety of different software and hardware techniques. 
     The following sections describe in detail systems and methods for a total knee joint replacement procedure. The knee joint often requires replacement in the form of prosthetic components due to strain, stress, wear, deformation, misalignment, and/or other conditions in the joint. Prosthetic knee joint components are designed to replace a distal portion or portions of a femur and/or a proximal portion or portions of a tibia. 
       FIG.  1    illustrates a femur F and tibia T, with the distal portion of the femur F and proximal portion of the tibia T forming the knee joint. To provide the reader with the proper orientation of the instruments and to assist in more fully understanding the construction of the instruments, a small chart is included on many of the figures. The charts indicate the general directions—anterior, posterior, medial, and lateral, as well as proximal and distal. These terms relate to the orientation of the knee bones, such as the femur and tibia and will be used in the descriptions of the various instruments consistent with their known medical usage. Additionally, the terms varus/valgus and posterior/anterior are used herein to describe directional movement. Varus/valgus is a broad term as used herein, and includes, without limitation, rotational movement in a medial and/or lateral direction relative to the knee joint shown in  FIG.  1   . Posterior/anterior is a broad term as used herein, and includes, without limitation, rotational movement in a posterior and/or anterior direction (e.g. in a flexion/extension direction) relative to the knee joint shown in  FIG.  1   . 
     Prior to replacing the knee joint with prosthetic components, surgical cuts commonly called resections are generally made with a cutting tool or tools along a portion or portions of both the proximal tibia and distal femur. These cuts are made to prepare the tibia and femur for the prosthetic components. After these cuts are made, the prosthetic components can be attached and/or secured to the tibia and femur. 
     The desired orientation and/or position of these cuts, and of the prosthetic components, can be determined pre-operatively and based, for example, on a mechanical axis running through an individual patient&#39;s leg. Once the desired locations of these cuts are determined pre-operatively, the surgeon can use the systems and methods described herein to make these cuts accurately. While the systems and methods are described in the context of a knee joint replacement procedure, the systems and/or their components and methods can similarly be used in other types of medical procedures, including but not limited to shoulder and hip replacement procedures. 
     I. Overview of Systems and Methods 
       FIGS.  2 - 6    show various systems which can be used in orthopedic procedures, such as joint replacement procedures. Such systems can include a tibial preparation system  10 , a femoral preparation system  510 , and a knee distraction and femoral preparation system  610 . As described below, each of these systems can be embodied in a number of variations with different advantages. 
     II. Tibial Preparation Systems and Methods 
     A number of different tibial preparation systems are discussed below. 
     These systems are useful for modifying the natural tibia to enable it to have a prosthetic component securely mounted upon it. 
     A. Tibial Preparation System with Target Probes 
     With reference to  FIG.  2   a   , a tibial preparation system  10  can comprise a surgical orientation device  12 , or other measuring device, which can be used to measure and record the location of anatomical landmarks of use in a total knee procedure, such as the location of the mechanical axis of the leg. The mechanical axis of the leg, as defined herein, generally refers to an axial line extending from the center of rotation of a proximal head of a femur (e.g. the center of the femoral head) through the center of the knee, to a center, or mid-point, of the ankle (see, for example,  FIG.  1   ). Generally, an ideal mechanical axis in a patient allows load to pass from the center of the hip, through the center of the knee, and to the center of the ankle. The tibial preparation system  10  also can include a coupling device  14 , a universal jig  16 , and target probes  18   a ,  18   b.    
     As used herein, the term “universal jig” is a broad term and includes, without limitation, orthopedic fixtures that are adapted to be connected to or coupled with, directly or indirectly, an anatomical structure, such as a bone, a limb, a portion of a joint, and to be moveable in one or more degrees of freedom, and in some cases is multiple degrees of freedom. As discussed further below, the universal jig  16  can be one form of an orthopedic fixture that can be used to couple the surgical orientation device  12  with a bone adjacent to a knee joint. In certain techniques discussed below the surgical orientation device  12  is used with a plurality of orthopedic fixtures. The coupling device  14  advantageously enables the surgical orientation device  12  to be quickly coupled and decoupled with a variety of orthopedic fixtures during the procedure. This enables the surgical orientation device  12  to be used in a modular fashion, with a variety of orthopedic fixtures at one or more stages of a procedure. 
     1. Surgical Orientation Device for Verifying Alignment of Orthopedic Fixtures 
     A surgical orientation device can be provided which can be used for verifying an alignment of an orthopedic fixture or fixtures, or a cutting plane or planes, during an orthopedic procedure. Surgical orientation device is a broad term as used herein, and includes, without limitation, devices which can be used alone or in conjunction with an orthopedic fixture or fixtures to orient a cutting plane during an orthopedic procedure or to otherwise identify or track a relative position of one or more surgical devices or anatomical structures, and can encompass any of the embodiments shown in the drawings and as described herein. For example,  FIG.  7    shows an embodiment of a surgical orientation device  12 . The surgical orientation device  12  can comprise a compact, generally hand-held and/or portable device for use in orienting a cutting guide or other surgical tool in a joint replacement procedure. The surgical orientation device  12  can be used to locate a portion of the mechanical axis that extends through the lower tibia or a portion thereof. Also, the surgical orientation device  12  can be used to locate a portion of the mechanical axis that extends through the femur or a portion thereof. In certain techniques discussed below, the surgical orientation device  12  is used to locate one, two, or more planes intersecting the mechanical axis. The surgical orientation device  12 , as described herein, can be used alone or in conjunction with other devices, components, and/or systems. 
     In a preferred arrangement, the surgical orientation device  12  can comprise a generally rectangular-shaped, box-like structure having an outer housing  20 . The outer housing  20  can be portable. The outer housing  20  can be comprised, at least in part, of plastic including but not limited to ABS, polycarbonate, or other suitable material. The surgical orientation device  12  can be configured for hand-held use. 
     With continued reference to  FIG.  7   , a front side  22 , or a portion of the front side  22 , of the surgical orientation device  12  can comprise a display  24 . The display  24  can be a separate component from the outer housing  20  or can be integrated on or within the outer housing  20 . The display  24  can comprise an output device. For example, the display  24  can comprise a liquid crystal display (“LCD”) or Ferroelectric Liquid Crystal on Silicon (“FLCOS”) display screen. The display screen can be sized such that a user can readily read numbers, lettering, and/or symbols displayed on the display screen while performing a medical procedure. In an embodiment, the display  24  comprises a Quarter Video Graphics Array (“QVGA”) Thin Film Transistor (“TFT”) LCD screen. Other types of display screens can also be used, as can other shapes, sizes, and locations for the display  24  on the surgical orientation device  12 . 
     The surgical orientation device  12  can further comprise at least one user input device  26 . The at least one user input device  26  can comprise a plurality of buttons located adjacent the display  24 . The buttons can be activated, for example, by a finger, hand, and/or instrument to select a mode or modes of operation of the device  12 , as discussed further below. In a preferred arrangement, the at least one user input comprises three buttons located underneath the display  24  as illustrated in  FIG.  7   . In other embodiments, the user input device  26  is a separate component from the housing  20 . For example, the user input device  26  can comprise a remote input device coupled to the surgical orientation device  12  via a wired or wireless connection. In yet other embodiments, the user input device  26  comprises a microphone operating in conjunction with a speech recognition module configured to receive and process verbal instructions received from a user. 
     As discussed below in connection with Figures ***, the surgical orientation device  12  includes a user interface with which a clinician can interact during a procedure. In one embodiment, the display  24  and at least one user input  26  can form a user interface. The user interface allows a surgeon, medical personnel, and/or other user to operate the surgical orientation device  12  with ease, efficiency, and accuracy. Specific examples and illustrations of how the user interface can operate in conjunction with specific methods are disclosed further herein. 
       FIGS.  8  and  9    show a back side  27  of the surgical orientation device  12 . The back side  27  can include an attachment structure or structures  28 , as well as a gripping feature or features  29  for facilitating handling of the surgical orientation device  12 . The attachment structures  28  can facilitate attachment of the surgical orientation device  12  to another device, such as for example the coupling device  14 . In a preferred arrangement, the attachment structures  28  comprise grooves, or channels  30 , along a portion of the back side of the surgical orientation device  12 . 
     The attachment structures  28  can be formed, for example, from protruding portions of the back side of the surgical orientation device  12 , and can extend partially, or entirely, along the back side of the surgical orientation device  12 . The attachment structures  28  can receive corresponding, or mating, structures from the coupling device  14 , so as to couple, or lock, the coupling device  14  to the surgical orientation device  12 .  FIGS.  10 A and  10 B  show top and bottom sides  31   a ,  31   b  of the surgical orientation device  12 . The surgical orientation device  12  can comprise optical components  32  that can be located on the top side  31   a , the bottom side  31   b , or the top and bottom sides  31   a ,  31   b  of the surgical orientation device  12 . The optical components  32  can comprise transparent windows  34  integrated into the surgical orientation device  12 . The optical components  32  can be windows that permit visible light (e.g. laser light) to emit from the top side  31   a , the bottom side  31   b , or both the top and bottom sides  31   a ,  31   b  of the surgical orientation device  12 . While the embodiment illustrated in  FIGS.  10   a  and  10   b    shows two windows  34  for transmitting light, other numbers are also possible. Additionally, while the optical components  32  are shown located on the top and bottom of the surgical orientation device  12 , in other embodiments the optical components  32  can be located in other positions and/or on other portions of the surgical orientation device  12 . 
       FIG.  11    illustrates a high-level block diagram of an electrical system  1100  of the surgical orientation device  12 . The electrical system  1100  comprises an electronic control unit  1102  that communicates with one or more sensor(s)  1104 , one or more visible alignment indicators  1106 , a power supply  1108 , a display  1110 , external memory  1112 , one or more user input devices  1114 , other output devices  1116  and/or one or more input/output (“I/O”) ports  1118 . 
     In general, the electronic control unit  1102  receives input from the sensor(s), the external memory  1112 , the user input devices  1114  and/or the I/O ports  1118  and controls and/or transmits output to the visible alignment indicators  1106 , the display  1110 , the external memory  1112 , the other output devices  1116  and/or the I/O ports  1118 . The electronic control unit  1102  can be configured to receive and send electronic data, as well as perform calculations based on received electronic data. In certain embodiments, the electronic control unit  1102  can be configured to convert the electronic data from a machine-readable format to a human readable format for presentation on the display  1110 . The electronic control unit  1102  comprises, by way of example, one or more processors, program logic, or other substrate configurations representing data and instructions, which operate as described herein. In other embodiments, the electronic control unit  1102  comprises controller circuitry, processor circuitry, processors, general purpose single-chip or multi-chip microprocessors, digital signal processors, embedded microprocessors, microcontrollers and/or the like. The electronic control unit  1102  can have conventional address lines, conventional data lines, and one or more conventional control lines. In yet other embodiments, the electronic control unit  1102  comprises an application-specific integrated circuit (ASIC) or one or more modules configured to execute on one or more processors. In certain embodiments, the electronic control unit  1102  comprises an AT91SAM7SE microcontroller available from Atmel Corporation. 
     The electronic control unit  1102  can communicate with internal memory and/or the external memory  1112  to retrieve and/or store data and/or program instructions for software and/or hardware. The internal memory and the external memory  1112  can include random access memory (“RAM”), such as static RAM, for temporary storage of information and/or read only memory (“ROM”), such as flash memory, for more permanent storage of information. In some embodiments, the external memory  1112  includes an AT49BV160D-70TU Flash device available from Atmel Corporation and a CY62136EV30LL-45ZSXI SRAM device available from Cypress Semiconductor Corporation. The electronic control unit  1102  can communicate with the external memory  1112  via an external memory bus. 
     In general, the sensor(s) can be configured to provide continuous real-time data to the surgical orientation device  12 . The electronic control unit  1102  can be configured to receive the real-time data from the sensor(s)  1104  and to use the sensor data to determine, estimate, and/or calculate an orientation or position of the surgical orientation device  12 . The orientation information can be used to provide feedback to a user during the performance of a surgical procedure, such as a total knee joint replacement surgery, as described in more detail herein. 
     In some arrangements, the one or more sensors  1104  can comprise at least one orientation sensor configured to provide real-time data to the electronic control unit  1102  related to the motion, orientation, and/or position of the surgical orientation device  12 . For example, the sensor module  1104  can comprise at least one gyroscopic sensor, accelerometer sensor, tilt sensor, magnetometer and/or other similar device or devices configured to measure, and/or facilitate determination of, an orientation of the surgical orientation device  12 . In some embodiments, the sensors  1104  can be configured to provide measurements relative to a reference point(s), line(s), plane(s), and/or gravitational zero. Gravitational zero, as referred to herein, refers generally to an orientation in which an axis of the sensor is perpendicular to the force of gravity, and thereby experiences no angular offset, for example tilt, pitch, roll, or yaw, relative to a gravitational force vector. In other embodiments, the sensor(s)  1104  can be configured to provide measurements for use in dead reckoning or inertial navigation systems. 
     In various embodiments, the sensor(s)  1104  comprise one or more accelerometers that measure the static acceleration of the surgical orientation device  12  due to gravity. For example, the accelerometers can be used as tilt sensors to detect rotation of the surgical orientation device  12  about one or more of its axes. The one or more accelerometers can comprise a dual axis accelerometer (which can measure rotation about two axes of rotation) or a three-axis accelerometer (which can measure rotation about three axes of rotation). The changes in orientation about the axes of the accelerometrs can be determined relative to gravitational zero and/or to a reference plane registered during a tibial or femoral preparation procedure as described herein. 
     In certain embodiments, a multi-axis accelerometer (such as the ADXL203CE MEMS accelerometer available from Analog Devices, Inc. or the LIS331DLH accelerometer available from ST Microelectronics.) detects changes in orientation about two axes of rotation. For example, the multi-axis accelerometer can detect changes in angular position from a horizontal plane (e.g., anterior/posterior rotation) of the surgical orientation device  12  and changes in angular position from a vertical plane (e.g., roll rotation) of the surgical orientation device  12 . The changes in angular position from the horizontal and vertical planes of the surgical orientation device  12  (as measured by the sensor  1104  can also be used to determine changes in a medial-lateral orientation (e.g., varus/valgus rotation) of the surgical orientation device  12 . 
     In some arrangements, the sensors  1104  comprise at least one single- or multi-axis gyroscope sensor and at least one single- or multi-axis accelerometer sensor. For example, the sensor module  1104  can comprise a three-axis gyroscope sensor (or three gyroscope sensors) and a three-axis accelerometer (or three accelerometer sensors) to provide positional and orientational measurements for all six degrees of freedom of the surgical orientation device  12 . In some embodiments, the sensors provide an inertial navigation or dead reckoning system to continuously calculate the position, orientation, and velocity of the surgical orientation device  12  without the need for external references 
     In some embodiments, the sensors  1104  comprise one or more accelerometers and at least one magnetometer. The magnetometer can be configured to measure a strength and/or direction of one or more magnetic fields in the vicinity of the surgical orientation device  12 . The magnetometer can advantageously be configured to detect changes in angular position about a horizontal plane. In other embodiments, the sensors  1104  comprise one or more sensors capable of determining distance measurements. For example a sensor located in the surgical orientation device  12  can be in electrical communication (wired or wireless) with an emitter element mounted at the end of a measurement probe. In certain embodiments, the electrical control unit can be configured to determine the distance between the sensor and emitter (for example, an axial length of a measurement probe corresponding to a distance to an anatomical landmark, such as a malleolus). 
     In other embodiments, the one or more sensors  1104  comprise a temperature sensor to monitor system temperature of the electrical system  1100 . Operation of some of the electrical components can be affected by changes in temperature. The temperature sensor can be configured to transmit signals to the electronic control unit  1102  to take appropriate action. In addition, monitoring the system temperature can be used to prevent overheating. In some embodiments, the temperature sensor comprises a NCP21WV103J03RA thermistor available from Murata Manufacturing Co. The electrical system  1100  can further include temperature, ultrasonic and/or pressure sensors for measuring properties of biological tissue and other materials used in the practice of medicine or surgery, including determining the hardness, rigidity, and/or density of materials, and/or determining the flow and/or viscosity of substances in the materials, and/or determining the temperature of tissues or substances within materials. 
     In certain embodiments, the sensors  1104  facilitate determination of an orientation of the surgical orientation device  12  relative to a reference orientation established during a preparation and alignment procedure performed during orthopedic surgery. Further details regarding the operation of the sensors in conjunction with a total knee replacement surgery will be discussed below. 
     The one or more sensors  1104  can form a component of a sensor module that comprises at least one sensor, signal conditioning circuitry, and an analog-to-digital converter (“ADC”). In certain embodiments, the components of the sensor module  1104  are mounted on a stand-alone circuit board that is physically separate from, but in electrical communication with, the circuit board(s) containing the other electrical components described herein. In other embodiments, the sensor module is physically integrated on the circuit board(s) with the other electrical components. The signal conditioning circuitry of the sensor module can comprise one or more circuit components configured to condition, or manipulate, the output signals from the sensor(s)  1104 . In certain embodiments, the signal conditioning circuitry comprises filtering circuitry and gain circuitry. The filtering circuitry can comprise one more filters, such as a low pass filter. For example, a 10 Hz single pole low pass filter can be used to remove vibrational noise or other low frequency components of the sensor output signals. The gain circuitry can comprise one or more operational amplifier circuits that can be used to amplify the sensor output signals to increase the resolution potential of the sensor. For example, the operational amplifier circuit can provide gain such that a 0 g output results in a midrange (e.g., 1.65 V signal), a +1 g output results in a full scale (e.g., 3.3 V) signal and a −1 g output results in a minimum (0 V) signal to the ADC input. 
     In general, the ADC of the sensor module can be configured to convert the analog output voltage signals of the sensor(s)  1104  to digital data samples. In certain embodiments, the digital data samples comprise voltage counts. The ADC can be mounted in close proximity to the sensor to enhance signal to noise performance. In certain embodiments, the ADC comprises an AD7921 two channel, 12-bit, 250 Kiloseconds per Sample ADC. In an arrangement having a 12-bit ADC can generate 4096 voltage counts. The ADC can be configured to interface with the electronic control unit  1102  via a serial peripheral interface port of the electronic control unit  1102 . In other embodiments, the electronic control unit  1102  comprises an on-board ADC that can be used to convert the sensor output signals into digital data counts. 
     With continued reference to  FIG.  11   , the visible alignment indicators  1106  can comprise one or more lasers, which can be configured to project laser light through the optical component or components  32  described above. For example, the visible alignment indicators  1106  can comprise a forward laser and an aft laser. The laser light can be used to project a point, a plane, and or a cross-hair onto a target or targets, including but not limited to an anatomical feature or landmark, to provide alternative or additional orientation information to a surgeon regarding the orientation of the orientation device  12 . For example, laser light can be used to project a plane on a portion of bone to indicate a resection line and a cross-hair laser pattern can be used to ensure alignment along two perpendicular axes. In certain embodiments, the visible alignment indicators  1106  can be used to determine a distance to an anatomical feature or landmark (for example, a laser distance measurement system). For example, the electronic control unit  1102  can project laser light to a target and a sensor  1104  within the surgical orientation device can sense the laser light reflected back from the target and communicate the information to the electronic control unit. The electronic control unit  1102  can then be configured to determine the distance to the target. The lasers can be controlled by the electronic control unit  1102  via pulse width modulation (“PWM”) outputs. In certain embodiments, the visible alignment indicators  1106  comprise Class  2 M lasers. In other embodiments, the visible alignment indicators  1106  comprises other types of lasers or light sources. 
     The power supply  1108  can comprise one or more power sources configured to supply DC power to the electronic system  1100  of the surgical orientation device  12 . In certain embodiments, the power supply  1108  comprises one or more rechargeable or replaceable batteries and/or one or more capacitive storage devices (for example, one or more capacitors or ultracapacitors). In other embodiments, power can be supplied by other wired and/or wireless power sources. In preferred arrangements, the power supply  1108  comprises two AA alkaline, lithium, or rechargeable NiMH batteries. The surgical orientation device  12  can also include a DC/DC converter to boost the DC power from the power supply to a fixed, constant DC voltage output (e.g., 3.3 volts) to the electronic control unit  1102 . In some embodiments, the DC/DC converter comprises a TPS61201DRC synchronous boost converter available from Texas Instruments. The electronic control unit  1106  can be configured to monitor the battery level if a battery is used for the power supply  1108 . Monitoring the battery level can advantageously provide advance notice of power loss. In certain embodiments, the surgical orientation device  12  can comprise a timer configured to cause the surgical orientation device  12  to temporarily power off after a predetermined period of inactivity and/or to permanently power off after a predetermined time-out period. 
     As discussed above, the display  1110  can comprise an LCD or other type screen display. The electronic control unit  1102  communicates with the display via the external memory bus. In certain embodiments, the electronic system  1100  comprises a display controller and/or an LED driver and one or more LEDs to provide backlighting for the display  1110 . For example, the display controller can comprise an LCD controller integrated circuit (“IC”) and the LED driver can comprise a FAN5613 LED driver available from Fairchild Semiconductor International, Inc. The electronic control unit  1102  can be configured to control the LED driver via a pulse width modulation port to control the brightness of the LED display. For example, the LED driver can drive four LEDs spaced around the display screen to provide adequate backlighting to enhance visibility. The display can be configured to display one or more on-screen graphics. The on-screen graphics can comprise graphical user interface (“GUI”) images or icons. The GUI images can include instructive images, such as illustrated surgical procedure steps, or visual indicators of the orientation information received from the sensor(s)  1104 . For example, the display can be configured to display degrees and either a positive or negative sign to indicate direction of rotation from a reference plane and/or a bubble level indicator to aid a user in maintaining a particular orientation. The display can also be configured to display alphanumeric text, symbols, and/or arrows. For example, the display can indicate whether a laser is on or off and/or include an arrow to a user input button with instructions related to the result of pressing a particular button. 
     With continued reference to  FIG.  11   , the user input device(s)  1114  can comprise buttons, switches, a touchscreen display, a keyboard, a joystick, a scroll wheel, a trackball, a remote control, a microphone, and the like. The user input devices  1114  can allow the user to enter data, make selections, input instructions or commands to the surgical orientation device  12 , verify a position of the surgical orientation device  12 , turn the visible alignment indicators  1106  on and off, and/or turn the entire surgical orientation device  12  on and off. The other user output devices  1116  (i.e., other than the display  1110 ) can comprise an audio output, such as a speaker, a buzzer, an alarm, or the like. For example, the audio output can provide a warning to the user when a particular condition occurs. The output devices  1116  can also comprise a visible output, such as one or more LED status or notification lights (for example, to indicate low battery level, an error condition, etc.). The audio output can comprise different patterns, tones, cadences, durations, and/or frequencies to signify different conditions or events. In other embodiments, output from the electronic control unit  1102  can be sent to external display devices, data storage devices, servers, and/or other computing devices (e.g., via a wireless network communication link). 
     The I/O ports  1118  of the electronic control unit  1102  can comprise a JTAG port and one or more serial communication ports. The JTAG port can be used to debug software installed on the electronic control unit  1102  during testing and manufacturing phases. The JTAG port can be configured such that it is not externally accessible post-manufacture. The serial communication ports can include a Universal Serial Bus (“USB”) port and/or one or more universal asynchronous receiver/transmitters (“UART”) ports. At least one of the UART ports can be accessible externally post-manufacture. The external UART port can be an infrared (“IR”) serial port in communication with an infrared (“IR”) transceiver. The IR serial port can be used to update the software installed on the electronic control unit  1102  post-manufacture and/or to test the operation of the electronic control unit  1102  by outputting data from the electronic control unit  1102  to an external computing device via an external wireless connection. Other types of I/O ports are also possible. 
     As described above, the sensor(s)  1104  can comprise one or more accelerometers. Accelerometers can measure the static acceleration of gravity in one or more axes to measure changes in tilt orientation. For example, a three-axis accelerometer can measure the static acceleration due to gravity along three orthogonal axes, as illustrated in  FIG.  12 A . A two-axis accelerometer can measure the static acceleration due to gravity along two orthogonal axes (for example, the x and y axes of  FIG.  12 A ). The output signals of an accelerometer can comprise analog voltage signals. The output voltage signals for each axis can fluctuate based on the fluctuation in static acceleration as the accelerometer changes its orientation with respect to the gravitational force vector. In certain embodiments, an accelerometer experiences static acceleration in the range from −1 g to +1 g through 180 degrees of tilt (with −1 g corresponding to a −90 degree tilt, 0 g corresponding to a zero degree tilt, and +1 g corresponding to a +90 degree tilt. The acceleration along each axis can be independent of the acceleration along the other axis or axes. 
       FIG.  12 B  illustrates a measured acceleration along each of the three axes of a three-axis accelerometer in six different orientation positions. TOP and BOTTOM labels, as well as a circle indicating Pin  1  of the accelerometer, have been included to aid in determining the various orientations. A gravitational force reference vector is illustrated as pointing straight down toward the Earth&#39;s surface. At positions A and B, the x-axis and the y-axis of the accelerometer are perpendicular to the force of gravity and the z-axis of the accelerometer is parallel to the force of gravity; therefore, the x and y acceleration components of static acceleration due to gravity at positions A and B are 0 g and the z component of static acceleration due to gravity at positions A and B is +1 g and −1 g, respectively. At positions C and E, the x-axis and the z-axis of the accelerometer are perpendicular to the force of gravity and the y-axis is parallel to the force of gravity; therefore, the x and z acceleration components of static acceleration due to gravity at positions C and E are 0 g and the y component of static acceleration due to gravity at positions C and E is +1 g and −1 g, respectively. At positions D and F, the y-axis and z-axis are perpendicular to the force of gravity and the x-axis is parallel to the force of gravity; therefore, the y and z acceleration components of static acceleration due to gravity at positions D and F are 0 g and the x component of static acceleration due to gravity at positions D and F is +1 g and −1 g, respectively. A dual-axis accelerometer operates in the same manner but without the z component. In certain arrangements, a three-axis accelerometer can be used as a tiltmeter to measure changes in orientation about two axes. 
     Multi-axis accelerometers can be conceptualized as having a separate accelerometer sensor for each of its axes of measurement, with each sensor responding to changes in static acceleration in one plane. In certain embodiments, each accelerometer sensor is most responsive to changes in tilt (i.e., operates with maximum or optimum accuracy and/or resolution) when its sensitive axis is substantially perpendicular to the force of gravity (i.e., when the longitudinal plane of the accelerometer sensor is parallel to the force of gravity) and least responsive when the sensitive axis is parallel to the force of gravity (i.e., when the longitudinal plane of the accelerometer sensor is perpendicular to the force of gravity).  FIG.  12 C  illustrates the output of the accelerometer in g&#39;s as it tilts from −90 degrees to +90 degrees. As shown, the tilt sensitivity diminishes between −90 degrees and −45 degrees and between +45 degrees and +90 degrees (as shown by the decrease in slope). This resolution problem at the outer ranges of tilt motion makes the measurements much less accurate for tilt measurements over 45 degrees. In certain embodiments, when the mounting angle of the surgical orientation device  12  is known, the sensor(s)  1104  can be mounted to be offset at an angle such that the accelerometer sensors can operate in their more accurate, steeper slope regions. For example, for use during the knee surgery preparation procedures described herein, the sensor(s)  1104  can be mounted at approximately a 22-degree angle relative to the anterior-posterior axis of the surgical orientation device  12  to account for a predetermined range of motion of the surgical orientation device  12  about the flexion/extension axis during the procedures. It should be appreciated by one of ordinary skill in the art that the accelerometer can be mounted at acute angles other than approximately 22 degrees. In other arrangements, the sensor(s)  1104  can be mounted to be offset to account for a predetermined range of motion about other axes of rotation as well. In yet other arrangements, for example, when a three-axis accelerometer is used, the accelerometer sensor(s) can be mounted in parallel with the anterior-posterior axis of the surgical orientation device  12 . In one three-axis accelerometer arrangement, a handoff system can be incorporated to ensure that the accelerometer sensors with the most accurate reading (e.g., &lt;45 degrees) are being used at each orientation position. The handoff system can employ hysteresis to avoid “bouncing” phenomena during the handoffs between the accelerometer sensors. 
       FIG.  12 D  illustrates the inside of the surgical orientation device  12 , according to an embodiment of the invention. The surgical orientation device  12  can comprise one or more circuit boards and/or other circuitry capable of installation within the surgical orientation device  12 . As illustrated, the surgical orientation device  12  can comprise a sensor board  36 A and a main board  36 B. The components of the sensor module (including the sensor(s)  1104 ) can be mounted on the sensor board  36 A and the other components of the electrical system  1100  are mounted on the main board  36 B. The sensor board  36 A can comprise one or more sensors  40  (e.g., sensor(s)  1104  as described above). In alternative embodiments, the sensor board  36 A and the main board  36 B can be combined into a single circuit board. The sensor board  36 A and the main board  36 B can comprise rigid or flexible circuit boards. The sensor board  36 A and the main board  36 B can be fixedly or removably attached to the outer housing  20 . 
     As illustrated, the sensor board  36 A is mounted at an approximately 22-degree angle relative to a plane extending longitudinally through the housing  20 , which can be parallel to or correspond to an anterior-posterior axis of the main board  36 B. As described above, mounting the sensor board  36 A at an offset angle can enable the one or more sensors to operate in the regions of maximum or optimum sensitivity, accuracy and/or resolution. The particular mounting offset angle can be selected based on a range of motion of the surgical orientation device  12  during a particular orthopedic procedure. For example, during the tibial preparation procedures described herein, the surgical orientation device  12  can be aligned with the coronal plane of the tibia with the leg in flexion and during the femoral preparation procedures described herein, the surgical orientation device  12  can be aligned to the leg in extension. Accordingly, the mounting offset angle is set at approximately 22 degrees to keep the orientation of the sensors from getting too close to the less accurate, low resolution range when the surgical orientation device  12  is positioned in the two flexion/extension orientations. As shown in  FIG.  12 D , the surgical orientation device  12  can include two AA batteries  38  as the power supply  1110  for providing power to the surgical orientation device  12 . The surgical orientation device  12  also can include lasers  42  as the visible alignment indicators  1106  described above. 
       FIG.  12 E  is a high-level flowchart of an exemplary conversion process for converting an analog voltage output signal of a multi-axis accelerometer into an angle degree measurement for presentation on the display  24 . Although the steps are described as being implemented with hardware and/or software, each of the steps illustrated in  FIG.  12 E  can be implemented using hardware and/or software. It should be appreciated that a similar conversion process can be performed for any other type of sensor or for multiple separate sensors without departing from the spirit and/or scope of the disclosure. 
     For each axis of rotation measured (e.g., pitch and roll), the multi-axis accelerometer can continuously output an analog voltage signal. At Block  1205 , the signal conditioning circuitry of the sensor module can filter the analog output voltage signal (e.g., with a low pass filter) to remove noise from the signal that may be present due to the high sensitivity of the multi-axis accelerometer. At Block  1210 , the signal conditioning circuitry amplifies, or boosts, the output voltage signal, for example, via the gain circuitry described above. 
     At Block  1215 , the ADC can convert the continuous analog voltage signal into a discrete digital sequence of data samples, or voltage counts. In certain embodiments, the ADC can sample the analog voltage signal once every two milliseconds; however, other sampling rates are possible. In certain embodiments, the analog voltage signal is oversampled. At Block  1220 , the electronic control unit  1102  can generate a stable data point to be converted to an angle measurement. The electronic control unit  1102  can apply a median filter to the sampled data to eliminate outliers (e.g., spikes) in the data. For example, the electronic unit  1102  can use an 11-sample median filter to generate the middle value from the last 11 samples taken. The output of the median filter can then be fed into a rolling average filter (for example, a  128  sample rolling average filter). The rolling average filter can be used to smooth or stabilize the data that is actually converted to an angle measurement. The electronic control unit  1102  can implement Blocks  1215  and  1220  using a finite impulse response (“FIR”) or an infinite impulse response (“IIR”) filter implemented in a software module. 
     At Block  1225 , the electronic control unit  1102  can convert the voltage count data to an angle measurement in degrees. In performing the conversion, the electronic control unit  1102  can be configured to apply a calibration conversion algorithm based on a calibration routine performed during a testing phase prior to sale of the surgical orientation device  12 . The calibration conversion can be configured to account for unit-to-unit variations in components and sensor placement. The calibration routine can be performed for each axis being monitored by the multi-axis accelerometer. The calibration conversion can comprise removing any mechanical or electrical offsets and applying an appropriate gain calibration for a positive or negative tilt. 
     As described above, the ADC can comprise an ADC with 12-bit resolution, which provides 4096 distinct voltage counts, wherein a −90 degree tilt corresponds to 0 counts (−2048 signed counts), a zero degree tilt corresponds to 2048 counts (0 signed counts), and a +90 degree tilt corresponds to 4096 counts (+2048 signed counts). The tilt angle for each axis (e.g., pitch and roll) of the multi-axis accelerometer can be calculated from the voltage count data based on standard trigonometric relationships as the arcsin of the acceleration component in each particular axis. In arrangements in which the electronic control unit  1102  applies the calibration conversion, the tilt angle for each axis can be calculated as follows: 
     
       
         
           
             
               
                 
                   
                     ANGLE 
                     = 
                     
                       a 
                       ⁢ 
                           
                       
                         sin 
                         [ 
                         
                           
                             
                               
                                 ( 
                                 
                                   
                                     SignedADC 
                                     ⁢ 
                                         
                                     Counts 
                                   
                                   + 
                                   OFFSET 
                                 
                                 ) 
                               
                               × 
                               GAIN 
                             
                             ) 
                           
                           2048 
                         
                         ] 
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   12.1 
                   ) 
                 
               
             
           
         
       
     
     where OFFSET corresponds with a zero offset of the surgical orientation device  12  determined during the calibration routine and GAIN corresponds with a ratiometric value determined during the calibration routine, with one GAIN value being used for negative tilt angles and a different GAIN value being used for positive tilt angles. 
     Also at Block  1225 , in arrangements where a dual-axis accelerometer is used, the electronic control unit  1102  can be configured to adjust the pitch angle (x axis) calculation to account for the mounting offset angle (described above) of the dual-axis accelerometer relative to the outer housing  20  of the surgical orientation device  20 . The result of Block  1225  is an absolute angle for each axis of rotation (e.g., pitch, roll) being monitored by the dual-axis accelerometer. The absolute pitch and roll angles can be used to calculate orientation measurements of the surgical orientation device  12 , such as a flexion-extension angle and a varus/valgus angle (as described in more detail below). 
     Orientation measurements for the surgical orientation device  12  can be determined based on a wide variety of reference frames in conjunction with any of a variety of surgical procedures. For example, when used in conjunction with a total knee replacement arthroscopic procedure, a reference frame can be established as shown in  FIG.  12 F . 
     As illustrated in  FIG.  12 F , the reference frame  1200  comprises three orthogonal axes (labeled x, y and z) having a point of origin at the center of a patient&#39;s knee joint when the patient&#39;s left leg is in flexion. The x-axis is illustrated as extending out of the page (in a lateral direction from the knee parallel to the horizon). The y-axis is illustrated as extending along a coronal plane of the tibia. The z-axis is illustrated as extending straight out from the knee at an offset of 90 degrees from the coronal plane of the tibia. As described herein, a flexion/extension rotation, or posterior-anterior pitch rotation, corresponds to rotation about the x-axis of the reference frame  1200  and a varus/valgus rotation, or a medial-lateral rotation, corresponds to rotation about the z-axis of the reference frame  1200 . A roll rotation, as described herein, corresponds to rotation about the y-axis of the reference frame  1200 . During the performance of alignment procedures in which the leg is fully extended, the x-axis maintains the same orientation and the y and z axes rotate toward the mechanical axis of the leg about the x axis. 
     As described above, a sensor  40  (e.g., a multi-axis accelerometer) can be configured to measure changes in angular position from a horizontal axis (e.g., pitch) and a vertical axis (e.g., roll). In performing the methods described herein, the surgical orientation device  12  can be mounted such that the pitch measurement of the sensor  40  corresponds to rotation about the x axis (e.g., flexion/extension rotation) of the reference frame  1200  and such that the roll measurement of the sensor  40  corresponds with rotation about the y axis of the reference frame  1200 . 
     In arrangements employing the use of the tibial preparation system  310 , the flexion/extension angle is calculated according to formula 12.1 above. In arrangements where a dual-axis accelerometer is used, the calculated flexion/extension angle can be adjusted to account for a mounting offset angle or can be compared to a reference flexion/extension orientation plane to generate a relative angle measurement. A relative flexion/extension angle can be generated by subtracting a reference flexion/extension angle stored in memory from the absolute measured flexion/extension angle. In certain embodiments, the reference flexion/extension angle corresponds with the orientation of the coronal plane of the tibia. 
     In arrangements employing the use of the tibial preparation system  310 , the varus/valgus angle can be derived based on the assumption that the pitch angle of the accelerometer, which corresponds with the flexion/extension angle of the surgical orientation device  12 , is fixed and known (e.g., the surgical orientation device  12  is mounted to an extramedullary alignment guide  314  that can only be rotated laterally or medially on a plane of fixed pitch) and on the assumption that the rotation angle of the roll sensor of the accelerometer was substantially zero degrees when the fixed pitch angle measurement (e.g., the reference flexion/extension angle) was registered, or recorded. Based on these two assumptions, the varus/valgus angle can be calculated as follows: 
     
       
         
           
             
               
                 
                   
                     Varus 
                     / 
                     Valgus 
                     ⁢ 
                         
                     Angle 
                   
                   = 
                   
                     arcsin 
                     [ 
                     
                       
                         sin 
                         ⁡ 
                         ( 
                         rollangle 
                         ) 
                       
                       
                         sin 
                         ⁡ 
                         ( 
                         fixedpitchangle 
                         ) 
                       
                     
                     ] 
                   
                 
               
               
                 
                   ( 
                   12.2 
                   ) 
                 
               
             
           
         
       
     
     where the roll angle is the current absolute roll angle being measured by the roll sensor of the accelerometer. A relative varus/valgus angle can be generated by subtracting a reference varus/valgus angle stored in memory from the absolute measured varus/valgus angle. In certain embodiments, the reference varus/valgus angle corresponds with the orientation of the sagittal plane of the tibia. 
     In arrangements where the tibial preparation systems  410  and  610  are used, the flexion/extension angle and the varus/valgus angle can be calculated as follows: 
     
       
         
           
             
               
                 
                   
                     Varus 
                     / 
                     Valgus 
                     ⁢ 
                         
                     Angle 
                   
                   = 
                   
                     arctan 
                     [ 
                     
                       
                         sin 
                         ⁡ 
                         ( 
                         rollangle 
                         ) 
                       
                       
                         sin 
                         ⁡ 
                         ( 
                         pitchangle 
                         ) 
                       
                     
                     ] 
                   
                 
               
               
                 
                   ( 
                   12.3 
                   ) 
                 
               
             
             
               
                 
                   
                     
                       
                         Flexion 
                         / 
                         Extension 
                         ⁢ 
                             
                         Angle 
                       
                       = 
                       
                         arcsin 
                         [ 
                         
                           
                             sin 
                             ⁡ 
                             ( 
                             rollangle 
                             ) 
                           
                           
                             sin 
                             ⁡ 
                             ( 
                             
                               Varus 
                               / 
                               ValgusAngle 
                             
                             ) 
                           
                         
                         ] 
                       
                     
                     ] 
                   
                   , 
                 
               
               
                 
                   ( 
                   12.4 
                   ) 
                 
               
             
           
         
       
     
     where the roll angle is the current absolute roll angle being measured by the accelerometer and the pitch angle is the current absolute pitch angle being measured by the accelerometer. As discussed above, these calculations can also be adjusted based on a calibration conversion or a mounting offset angle. 
     In certain embodiments, the above calculations can be performed by software modules executed by the electronic control unit  1102 . In other embodiments, the electronic control unit  1102  can generate the angle measurements using data stored in one or more look-up tables (“LUT”s). In other embodiments, other calculations can be derived based on the type of sensor or sensors used, the procedure being performed, and/or the reference frame being employed. 
     In certain embodiments, the electronic control unit  1102  can perform a stabilization routine, process, or algorithm to assess or determine the stability, or reliability, of the calculated angle measurements. For example, the electronic control unit  1102  can keep a history of the last 100 ms of calibrated sample data for each axis being monitored by the sensor(s)  40 . Each time a new sample is added to the 100-sample history, a maximum and minimum value is determined for the 100-sample data set. The electronic control unit  1102  can then determine a delta difference between the maximum and minimum values. The electronic control unit  1102  can then compare the delta difference between the maximum and minimum values to a threshold. If the delta difference is lower than the threshold, then the data is considered to be stable and it is stored in memory (e.g., external memory  1112 ) and time-stamped. If the delta difference is greater than the threshold, then the data is considered to be unstable. When retrieving an angle reading to display to the user, the electronic control unit  1102  can be configured to transmit the last stable data reading (assuming it is not too old) to the display  1110  instead of the current unstable reading. If the last stable angle exceeds a time threshold, the unstable angle reading can be displayed along with a visual indication notifying the user that the angle reading is unstable. For example, a red “shaky hand” icon or graphical user interface image can be displayed on the display screen. 
     2. Surgical Orientation Device with a Disposable Portion which Allows Inner Components to be Reused in a Sanitary Manner 
     In one embodiment, a surgical orientation device can be provided with a disposable housing. This arrangement can maximize reuse of internal components while maintaining the cleanliness of the device.  FIG.  13    shows an embodiment of a surgical orientation device  12   a  which comprises a disposable outer housing  21 . The disposable outer housing  21  can include, or be releasably attached to, a cover  44 . The cover  44  can be in the form of a latch, flap, zipper, plastic-zip fastener, or other similar structure which covers and/or seals an opening in the disposable outer housing  21 . The cover  44  can be pivotally connected to a portion of the disposable outer housing  21 , such that when the cover  44  is swung open or removed, visual inspection and removal/insertion of interior, reusable components (e.g. the electronic control unit  1102 , display  24 , optical components  32 ) of the surgical orientation device  12   a  is provided. 
     The disposable outer housing  21  can be manufactured and packaged in a sterile state and can provide a sterile barrier between the reusable components inside the surgical orientation device  12  and their outside environment. Thus, once the surgical orientation device  12  has been used, the disposable outer housing  21  can be discarded or destroyed, and the interior, reusable components can be used again. 
     The disposable outer housing  21  can also be manufactured such that it engages and/or receives one or more interior reusable components of the surgical orientation device  12 . Preferably these components are received within the housing  21  without the interior reusable components contacting any outside surface of the disposable outer housing  21 , thereby protecting the outside surfaces of the disposable outer housing  21  from contact with the interior reusable components. A separate, sterile shield can provide a temporary barrier between the sterile housing and non-sterile surgical orientation device  12  during insertion to prevent accidental contact between the surgical orientation device  12  and outside surfaces of the housing. Once the surgical orientation device  12  is inserted the shield can be removed and discarded allowing the door to be closed. 
     The disposable outer housing  21  can contain slots or grooves on one or more interior walls of the disposable outer housing  21  to enable the interior reusable components, or a combined set of interior reusable components in the form of a reusable assembly, to be positioned or set within the disposable outer housing  21 . For example, the reusable components or assembly can contain slots or grooves which mate with the slots or grooves of the disposable outer housing  21 . This mating arrangement can minimize contact between more delicate features of the reusable components (e.g. a circuit board) and the inside surfaces of the disposable outer housing  21 . In some embodiments the inside of the disposable outer housing  21  and the outside of the interior reusable components or assembly can be tapered to allow easy, low precision insertion of the interior reusable components or assembly but provide secure mating once the disposable outer housing  21  and the reusable interior components or assembly are fully engaged. Electrical contact between the surgical orientation device  12  and housing can be provided by spring loaded probes and conductive contacts. The disposable housing  21  can include touch screen for user interface. (e.g. an LCD display can still be part of the SOD). The disposable housing  21  can be packaged with disposable batteries so users don&#39;t have to deal with recharging of batteries. 
     In yet other configurations, the interior reusable components, assembly, and/or disposable outer housing  21  of the device can contain other mating features, including but not limited to clamps or adaptors, which facilitate sanitary handling of the surgical orientation device  12 . 
     The disposable outer housing  21  can also contain one or more sheets of material, such as a thin plastic layer, temporarily affixed to one or more of its outside surfaces (for example by a weak adhesive), sufficient to protect the disposable outer housing  21  from contamination by the reusable interior components or assembly during the process of engaging the disposable outer housing  21  to the reusable interior components or assembly. The sheets of material temporarily affixed to the disposable outer housing  21  can be removed following the engagement of the disposable outer housing  21  to the reusable interior components or assembly. 
     In a preferred arrangement, the disposable outer housing  21  can include a transparent section or sections (e.g. a thin plastic membrane) which covers both the display  24  and user inputs  26 . This section or sections of the disposable housing  21  can be manufactured to allow the user to manipulate the user interface elements by pressing against this section or sections of the disposable housing  21 . For example, the disposable outer housing  21  can include a touch-sensitive overlay which covers the display  24  to enable the display  24  of the surgical orientation device  12  to be operated as a touch screen. The surgical orientation device  12  can include an electrical interface, for example probes or sliding contacts, between the disposable and re-usable elements of the touch screen (i.e. the transparent sections of the disposable outer housing  21  and the display  24 ) to enable the transfer of information, electricity and/or other energy between the disposable outer housing  21  and the display  24 . 
     With continued reference to  FIGS.  12  and  13   , the batteries  38  can be in either or both of the reusable and disposable portion or portions of the surgical orientation device  12 . If the batteries  38  are contained in the disposable outer housing  21 , the surgical orientation device  12  can contain one or more transmission media, connectable between the reusable interior elements or assembly and the disposable outer housing  21 , capable of conducting power from the batteries in the disposable outer housing  21  to the reusable interior components or assembly that requires power for the surgical orientation device&#39;s operation. 
     3. Device for Coupling a Surgical Orientation Device to Orthopedic Fixtures 
     A device can be provided which can be used to couple a surgical orientation device to one or more orthopedic fixtures. For example,  FIGS.  2  and  14    show a coupling device  14 . The coupling device  14  can comprise a housing  46 , cam mechanism  48 , and a surgical orientation device attachment mechanism  50 . The coupling device  14  can be used generally to attach two surgical instruments and/or components together. For example, in the tibial preparation system  10 , the coupling device  14  can be used to couple the surgical orientation device  12  to the universal jig  16 . 
       FIG.  15    shows the housing  46 , which can be made out of plastic or other suitable material including but not limited to polypropylene or PET. The housing  46  can include openings and/or slots  52  for insertion of the cam mechanism  48  and surgical orientation device attachment mechanism  50 . The housing  46  can further include an elongate portion  54 , which can be inserted into the grooves or channels  30  along the back portion of the surgical orientation device  12  described above. 
       FIG.  16    shows the cam mechanism  48 , which can comprise a handle  56  with an off-center cam  58  at one end. The off-center cam  58  can be pivotally attached to an arm  60 . The arm  60  can include a pin or pivot mechanism which is insertable into an opening  52  of the housing  46 . 
       FIG.  17    shows the coupling device  14  fully assembled. The coupling device  14  can be used to frictionally engage and hold onto a surgical instrument or component. For example, as the handle  56  is rotated, the arm  60  can swing into a position such that an end  62  of the arm  60  is frictionally engaged with or clamps onto a portion of a surgical instrument or component extending through the opening  64 . The surgical instrument or component can extend between structures  77  of the housing  46 . such that as the arm  60  swings, the end  62  can contact the surgical instrument or component and press it firmly against the structure  77 , thereby at least partially locking the surgical instrument or component to the coupling device  14 . 
     With reference again to  FIG.  16   , the surgical orientation device attachment mechanism  50  can comprise a knob  66 . The knob  66  can be attached to an arm  68 . The arm  68  can be attached to a rotatable structure  70 . The rotatable structure  70  can comprise a pin  72  which can be inserted into an opening  62  of housing  46 . The rotatable structure  70  can also comprise a protrusion  74 . As the knob  66  is pushed, and/or turned, the protrusion  74  can pivot about the pin  72 . 
     With reference to  FIGS.  8 ,  9 ,  14 , and  16   , the surgical orientation device  12  can be securely attached to the coupling device  14 . To attach the surgical orientation device  12  to the coupling device  14 , the elongate portion  54  of the coupling device  14  can be inserted into the grooves or channels  30  along the back of the surgical orientation device  12 . Once a portion of the elongate portion  54  is inside the grooves or channels  30 , the surgical orientation device attachment mechanism  50  can be used to secure the surgical orientation device  12  to the coupling device  14 . For example, the knob  66  can be pulled, and/or turned, such that the protrusion  74  pivots about the pin  72 , and moves into a groove  76  shown in  FIGS.  8  and  9   . Once inside the groove  76 , the protrusion  74  can inhibit the surgical orientation device  12  from slipping off of and/or becoming removed from, the coupling device  14 . In some embodiments, the knob  66  and/or protrusion  74  can be biased by a compressive member (e.g. spring) housed in the housing  46  to facilitate attachment of the coupling device  14  to the surgical orientation device  12 . For example, the protrusion  74  can be biased towards a locking position in which the protrusion is moved towards the groove  76  shown in  FIGS.  8  and  9   . In some embodiments, the knob  66  can be pushed and/or turned to release the surgical orientation device  12  from the coupling device  14 . 
     While the coupling device  14  described above can be used to attach and/or couple the surgical orientation device  12  with the universal jig  16 , other methods and devices for attaching and/or coupling the components of the tibial preparation system  10  are also possible. 
       FIG.  17   a    shows another embodiment of a coupling device  14 ′. The coupling device  14 ′ can be similar to the coupling device  14  described above, and can include an elongate protrusion  54 ′, a handle  56 ′, an arm  60 ′, and a knob  66 ′. The knob  66 ′ can comprise a lever-like structure which can pivot in order to lock and unlock a portion of the coupling device. 
     4. Orthopedic Fixture for Orienting a Surgical Orientation Device in Multiple Degrees of Freedom 
     An orthopedic fixture can be provided which can have a moveable portion or portions which are used to orient a surgical orientation device. The surgical orientation device can be oriented in multiple degrees of freedom. For example,  FIGS.  2 ,  18 , and  19    show an orthopedic fixture in the form of a universal jig  16 . The universal jig  16  can comprise a base member  78 , a posterior/anterior adjustment block  80 , a varus/valgus adjustment block  82 , and a cutting block  84  (e.g. an anterior block for placement or attachment along an anterior surface of the tibia). These components provide for multiple degrees of freedom of operation of a moveable portion of the jig  16  such that devices coupled therewith (e.g., the surgical orientation device  12 ) can be moved to a variety of orientations during the procedure. 
     a. Base Member for Providing an Anchored or Fixed Initial Position of an Orthopedic Fixture 
     A base member can be provided that anchors an orthopedic fixture and/or provides a fixed initial position of a moveable orthopedic fixture. For example, a base member  78  can comprise a structure that is rigidly and/or fixedly attached to an anatomical structure. The base member  78  can be attached to an anterior surface of a patient&#39;s tibia. In a preferred arrangement, the base member  78  can comprise at least one base member attachment opening  86 . For example, the base member  84  can comprise two base member attachment openings  86 . Attachment openings, apertures, and/or holes as described herein with respect to tibial preparation system  10  and other systems described herein, can comprise bores, non-threaded holes, threaded holes, and/or other types of holes or openings which extend partially or entirely through a structure. 
     For example, the base member attachment openings  86  can extend entirely through the base member  78 . Each of the base member attachment openings  86  can be configured to receive a fastening device, such as for example a screw, to anchor the base member  78  into a bone or other anatomical structure and fix the base member  78  relative to the bone or anatomical structure. 
     The base member  78  can further comprise a base member receiving opening  88 . The receiving opening  88  can be located along an anterior side of the base member  78 , and can be sized and shaped so as to receive a pin of the varus/valgus adjustment block  82 . The receiving opening  88  can extend entirely or partially through the base member  78 , and in some embodiments can be partially or entirely threaded. 
     The base member  78  can further comprise a base member pin  90 . Pins, as described herein with respect to tibial preparation system  10  and other systems described herein, can be solid, threaded, formed of plastic, metal, or other material, comprise linear bearings, and/or have shapes sizes, and configurations other than those shown and/or described. 
     The pin  90  can extend through an opening or openings  91  of the base member  78 , and can be sized and shaped so as to be inserted through a cut-out  95  of the posterior/anterior adjustment block  80 . The pin  90  can be partially or entirely threaded, and can include a knobbed portion  90   a  on one end which can be gripped and turned by a user. 
     The base member  78  can further comprise an elongate base member rod  92 . The elongate base member rod  92  can extend distally beneath the pins  90 ,  96 , and can include a brace-like structure  94  on a distal end thereof. The brace-like structure  94  can be curved, and used to brace and/or hold the universal jig  16  against the patient&#39;s skin overlying the tibia during the knee replacement procedure. The base member rod  92  and structure  94  can provide a stabilizing force against a portion of the tibia. For example, the structure  94  can be placed around, or wrapped, against the skin near a proximal portion of the tibia. The universal jig  16  can, while being anchored or moved as described herein, experience a force or forces which can tend to cause the universal jig  16  as a whole to twist or rotate. The structure  94  can at least partially absorb these forces by bracing itself against the tibia. For example, the structure  94  can minimize a torquing motion of the universal jig  16  while an anchoring pin or pins are being inserted through the base member and into the tibia. Also, once the universal jig  16  is locked in position for resection it can resist torquing during resection caused by pressure of a cutting tool in a slot of the cutting block  84 . This can improve accuracy of resection. The base member rod  92  and structure  94  can be adjusted accordingly to account for these forces. For example, the structure  94  can be rotated about the end of the base member rod  92 , and/or be made of material capable of withstanding anticipated forces. Additionally or alternatively, the base member rod  92  can be configured to adjust distally so as to extend or shorten, depending on a desired location for the structure  94 . 
     b. Device for Adjusting a Posterior/Anterior Slope of a Cutting Block 
     A device can be provided which can be used to adjust the orientation in a sagittal plane of a surgical orientation device and/or cutting block. For example, and with continued reference to  FIGS.  2 ,  18 , and  19   , the posterior/anterior adjustment block  80  of universal jig  16  can comprise a structure which is moveable (e.g. rotatable) in at least one of a posterior and anterior direction. 
     The posterior/anterior adjustment block  80  can comprise a cutout  95 . The cutout  95  can be sized and shaped so as to generally receive and/or surround the base member pin  90 . The cutout  95  can extend entirely through the posterior/anterior adjustment block  80 , and can generally form a cut-out portion of the block  80 . 
     The posterior/anterior adjustment block  80  can further comprise a posterior/anterior adjustment pin  96 . The pin  96  can extend through an opening  97  of the posterior/anterior adjustment block  80 . One end of the pin  96  can be sized and shaped so as to contact and/or be inserted within an opening  97   a  of the varus/valgus adjustment block  82 . The pin  96  can be partially or entirely threaded, and can include a knobbed portion  96   a  on one end which can be gripped and turned by a user. 
     The posterior/anterior adjustment block  80  can further comprise posterior/anterior adjustment block hinge openings  98 . The hinge openings  98  can be sized and shaped to receive a pin-like structure. The posterior/anterior adjustment block  80  can pivot about the pin-like structure and/or about an axis extending through the hinge openings  98  when the knob  96   a  on the end of the posterior/anterior adjustment block pin  96  is turned. 
     The posterior/anterior adjustment block  80  can further comprise an opening  105  and/or structure which can receive and/or affix a portion of the cutting block  84  (e.g. rod  104 ) to the posterior/anterior adjustment block  80 . By affixing the posterior/anterior adjustment block  80  to the cutting block  84 , movement of the posterior/anterior adjustment block  80  and cutting block  84  can be linked such that movement of the posterior/anterior adjustment block  80  can cause similar or identical movement of the cutting block  80 . 
     The posterior/anterior adjustment block  80  can further comprise a posterior/anterior adjustment block guide rod  99 . The guide rod  99  can extend from the posterior/anterior adjustment block  80 , and can be sized and shaped to receive and/or couple with the surgical orientation device  12 , or coupling device  14 . 
     c. Device for Adjusting a Varus/Valgus Slope of a Cutting Block 
     A device can be provided which can be used to adjust the orientation in a coronal plane of a surgical orientation device and/or cutting block. For example, and with continued reference to  FIGS.  2 ,  18 , and  19   , the varus/valgus adjustment block  82  of universal jig  16  can comprise a structure which is moveable (e.g. rotatable) in at least one of a varus/valgus direction. 
     The varus/valgus adjustment block  82  can comprise a varus/valgus adjustment block pin  100 . The pin  100  can extend through a portion or portions of the varus/valgus adjustment block  82 . The pin  100  can be received within the base member receiving hole  88 , and in some embodiments can be partially or entirely threaded. In some embodiments the pin  100  can be unthreaded. The pin  100  can include a pin opening  100   a . The pin opening  100   a  can receive the same pin-like structure received by the hinge openings  98  described above. 
     When the base member pin  90  is turned, the varus/valgus adjustment block  82  can pivot about the pin  100 , such that the varus/valgus adjustment block  82  pivots in at least one of a varus and valgus direction. 
     The varus/valgus adjustment block  82  can further include an opening  103  along a side surface  101  of the varus/valgus adjustment block  82 , which can receive the base member pin  90 . In some embodiments the opening  103  can be threaded or structured in a manner such that turning the knob  90   a  on the end of the pin  90  in either a clockwise or counterclockwise direction can cause movement of the varus/valgus adjustment block  82 . 
     With continued reference to  FIGS.  2  and  18   , movement of the varus/valgus adjustment block  82  can cause movement of the posterior/anterior adjustment block  80 . For example, a portion or portions of the varus/valgus adjustment block  82  can rest within and/or be contacted on either side by portions of the posterior/anterior adjustment block  80 , such that any movement of the varus/valgus adjustment block  82  in a varus or valgus direction likewise causes similar or identical movement of the posterior/anterior adjustment block  80 . 
     d. Cutting Block which can be Oriented in a Posterior/Anterior, and/or a Varus/Valgus, Direction for Bone Resection 
     A cutting block, or other orthopedic fixture, can be provided for bone resection. The cutting block can be oriented with the aid of a surgical orientation device, an orthopedic fixture, or a surgical orientation device and an orthopedic fixture. For example, and with continued reference to  FIGS.  2 ,  18 , and  19   , the cutting block  84  can comprise at least one opening  102 . One opening  102  can comprise, for example, an elongate slit along a width of an upper, or proximal, portion of the cutting block  84  for receiving and guiding a saw, blade, or other cutting tool. Other openings  102   a  can extend from an anterior face  84   a  of the cutting block  84  towards a posterior face  84   b  thereof, and can comprise holes for insertion of an anchoring pin or pins. In various techniques, such pins are extended through the openings  102   a  and into an anterior face of the tibia. The cutting block  84  can also include a probe  84  for aiding in referencing an anatomical landmark. 
     As described above, the posterior/anterior adjustment block  80  can be coupled to the cutting block  84  such that movement of the posterior/anterior adjustment block  80  causes similar or identical movement of the cutting block  84 . For example, the cutting block  84  can comprise a cutting block guide rod  104 . The guide rod  104  can extend from the upper, or proximal, portion of the cutting block  84 , and can be sized and shaped so as to be received within the opening  105  of the posterior/anterior adjustment block  80 . The opening  105  can extend through the posterior/anterior adjustment block  80  adjacent the posterior/anterior adjustment block hinge holes  98 . This opening can receive the cutting block guide rod  104 , and couple the anterior/posterior adjustment block  80  to the cutting block  84  to link movement between the posterior/anterior adjustment block  80  and cutting block  84 . The cutting block  84 , as well as other cutting blocks described herein, can in some embodiments be removably attachable to one or more components of an orthopedic fixture, and can be attached or removed at various stages of an orthopedic procedure. 
     5. Target Probes which can be Used to Identify Anatomical Planes or Axes 
     Target probes can be provided for identifying anatomical planes and/or axes. For example, and with reference to  FIGS.  2  and  20   , the at least one target probe  18   a ,  18   b , or other targets or devices, can comprise a structure for contacting an anatomical landmark and serving as a target for an emitted laser beam or beams from the surgical orientation device  12 . For example, in a preferred arrangement, the at least one target probe  18   a ,  18   b  can comprise an elongate member  106  with an anatomical contact portion  107  and a target portion  108 . 
     The anatomical contact portion  107  can comprise an end of the elongate member  106  or other structure configured to contact an anatomical feature, such as for example the lateral malleolus. The anatomical contact portion  107  can be held against the anatomical feature by hand, can be drilled into the anatomical feature, or can be held against and/or coupled with the anatomical feature in some another fashion. 
     The anatomical contact portion  107  can be connected to or integrally formed with the target portion  108 . The target portion  108  can comprise an area on the target probe  18   a ,  18   b  which, as described further herein, is configured to indicate whether the target probe  18   a ,  18   b  is aligned with the surgical orientation device  12  and/or cutting block  84 . For example, the target portion  108  can comprise one or more target shapes  110 , in the form of markings, slits, or other structures. The target shapes  110 , if for example in the form of slots, can be wide enough to allow a beam of laser light, such as for example a beam in the form of a plane or a cross-hair beam, to pass through the target shapes  110 .  FIG.  20    illustrates an embodiment of a target probe  18   b  with a target shape  110  in the form of a single slot, and a target probe  18   a  with two slots in the form of a cross, for example formed as two perpendicular lines or slots 
     The target portion  108  can additionally be adjustable, such that as the anatomical contact portion  107  is held in place against the anatomical landmark, the target portion  108  can be moved relative to the anatomical landmark. For example, the target portion  108  can comprise a screw or other element which can be adjusted in order to change the length of the target probe  18   a ,  18   b . In one embodiment, a device is provided to enable the position of the target portion  108  on the elongate member  106  to be adjusted. The device enables the target portion  108  to be moved closer to or away from the contact portion  106 . Such adjustment provides one technique for aligning an orthopedic fixture, a surgical orientation device, or an orthopedic fixture and surgical orientation device, with a coronal or sagittal plane. 
     The target probes  18   a ,  18   b  can further include a marking or markings which indicate a current length of the target probe  18   a ,  18   b , and/or indicate the degree or amount of adjustment which has been made to the target probe  18   a ,  18   b . For example, the target portion  108  can comprise millimeter markings or other visual indicia corresponding to lengthwise offset along a length of the target portion  108 , indicating adjustments in the length of millimeters. 
     In some embodiments, the target probes  18   a ,  18   b  shown in  FIG.  20    can comprise the same target probe. Thus,  FIG.  20    can illustrate opposite sides of the same target probe. For example, one side of the target probe can have a cross-hair target  110 , and the other side of the target probe can have a single slot target  110 . 
     6. Additional Sensors for Relative Movement 
     While the embodiment of the tibia preparation system  10  described above is described as having a sensor or sensors  40  located entirely within the surgical orientation device  12 , in other embodiments the tibia preparation system  10 , or other systems used for joint replacement and/or resection (e.g. for hip and shoulder), can include an additional sensor or sensors  40 . These additional sensors  40  can be located on other surgical components and/or anatomical landmarks. U.S. Pat. No. 7,559,931 discloses examples of sensors on multiple surgical components and/or anatomical landmarks, and is herein expressly incorporated by reference and made a part of this disclosure. In one embodiment, the tibia preparation system  10  can include an additional sensor  40  located on the base member  78 , or on the proximal tibia. The additional sensor  40  can include a microcontroller and/or communication device (e.g. infrared or other wireless technology (e.g. Bluetooth™)) which can relay information from the additional sensor  40  to the electronic control unit  1102  of the surgical orientation device  12 . This additional sensor or sensors  40  can detect changes in movement of the tibia and/or leg during a knee replacement procedure, so as to verify whether the patient&#39;s leg (which typically is securely held in place during the procedure) has inadvertently or unintentionally moved in a varus/valgus, posterior/anterior, and/or other direction. 
     The electronic control unit  1102  can be configured to receive the information from this additional sensor or sensors  40 , and/or the sensor&#39;s communications device, and combine that information with information from the sensor or sensors  40  located within the surgical orientation device  12  to calculate an overall, or aggregate, movement and orientation of the surgical orientation device  12  relative to an axial line or plane. The electronic control unit  1102  can correct for changes in position of this axis or plane, and the display  24  can indicate to the user an appropriate varus/valgus and/or flexion/extension angle for resection, based on the actual location of the mechanical axis or plane. 
     Additionally, this additional sensor or sensors  40  can be located in a device. The device can be constructed such that the device is autoclavable and reusable, and can allow insertion and removal of a disposable battery. The additional sensor or sensors  40  can be incorporated with any of the systems and/or methods described herein, and can be placed on any of the components of the systems described herein. 
     B. Acquiring Orientation Information Using a Visible Indicator and Target Probes 
     1. Pre-Operative Planning 
     Pre-operative planning can be used to prepare for a joint replacement procedure. For example, in a knee replacement procedure, the user can assess a desired varus/valgus angle and flexion/extension angle for resection of the tibia along a proximal portion of the tibia. This assessment can be made, for example, by clinical inspection (e.g. x-rays or manual visual inspection) of the knee prior to surgery. The pre-operative planning will usually determine what angle or angles of resection will be appropriate prior to attachment of the prosthetic knee component or components to the tibia. 
     The leg can then be secured by placement in a leg holder, and the knee can be exposed using a standard surgical procedure. Osteophytes on the proximal tibia can be removed, and a resection depth of the tibia can be determined by using a stylus or other instrumentation. For example, depth of resection can be determined by aligning the stylus length-wise, parallel with the tibia, with the depth of resection being determined by the point of contact between the tip of the stylus and the lowest point of a medial condyle of the proximal tibia. This resection depth can provide an indication to the user of what size prosthetic component or components to use, as well as how far to cut into the tibia with a cutting tool (e.g. saw blade). 
     2. Registering the Coronal and Sagittal Planes 
     After pre-operative planning for a joint replacement procedure, the tibial preparation system  10  described above can be used to identify the location and orientation of an axial line, as well as to orient a cutting block relative to the axial line. 
     For example, once the desired varus/valgus and posterior/anterior angles for resection have been determined pre-operatively, the tibial preparation system  10  can be assembled. The surgical orientation device  12 , coupling mechanism  14 , and universal jig  16  can be coupled together, and the tibial preparation system  10  can be positioned adjacent the proximal tibia on an anterior side of the tibia (i.e. front of the leg). 
     In a preferred arrangement, the tibial preparation system  10  can be positioned and/or moved until the surgical orientation device  12  is generally centered with the insertion of an anterior cruciate ligament and a medial tibial insertion of the patella tendon in a patient&#39;s knee. To achieve this centering, the surgical orientation device  12  can emit a laser beam or beams proximally from one of its optical components  32 . This laser beam or beams can illuminate a portion of the knee joint, and the tibial preparation system  10  can be moved until the laser beam is aligned with at least one of the insertion of the anterior cruciate ligament and the medial tibial insertion of the patella tendon (e.g. the medial third of the tibial tuberosity). For example, if the optical component  32  emits a cross-hair beam, centering can be verified with a vertical portion (e.g. one which is parallel to or coincident with a sagittal plane extending through the leg) of the beam being aligned with both the insertion of the anterior cruciate ligament and the medial tibial insertion of the patella tendon. 
     With reference to  FIG.  21   a   , once centering has been achieved, the base member  78  of the universal jig  16  can be coupled to or otherwise secured adjacent to a proximal portion of the tibia T. Preferably, the coupling securement is such that the base member  78  has zero or substantially zero degrees of freedom relative to the tibia T. In one technique, the base member  78  is pinned, which comprises placing at least one pin or other anchoring device through the holes  102   a  described above and into an anterior face of the tibia. 
     The user can then pick up and adjust locations of the target portions  108  of the target probes  18   a ,  18   b . For example, the lengths of the target probes  18   a ,  18   b  can be adjusted to take into account a distance, which exists after attachment of the universal jig  16  to the tibia, between the optical element  32  of the surgical orientation device  12  and a mechanical axis of the leg. 
     In a preferred arrangement, a stylus, marker pin, or other measuring device can be used to measure the distance between an A/P point on the proximal tibia and a plane parallel to a coronal plane containing the mechanical axis. This distance can be measured, for example, by referring to analogous numbering systems labeled on both the target probe  18   a ,  18   b  and the measuring device. For example, a  FIG.  21   b    shows a tibial preparation system  10 ′. The tibial preparation system  10 ′ is similar to the preparation system  10  described above, and includes the surgical orientation device  12  and a universal jig  16 ′. The measuring device  109 , as shown in  FIG.  21 A , can be located proximal the cutting block  84  in a system  10  or  10 ′. The measuring device  109   a  can comprise etchings, or markings, to measure distance. The measuring device  109   a  can be moved, for example, until a tip  109   b  of the measuring device  109   a  is resting over the insertion point of the anterior cruciate ligament in the knee (for example as shown in  FIG.  21 B ), and/or a soft point on the top of the tibia commonly referred to as the A/P point of the mechanical axis. This point is located along a tibial spine on top of the tibia, and generally marks the location of a point along the mechanical axis of the leg. 
     The user can use the measuring device  109   a  to measure the distance between the coronal plane containing the mechanical axis (including the A/P point) and, for example, the location of the optical element  32  on the surgical orientation device  12 . Once this distance is known, the length of the target probes  18   a ,  18   b  can be adjusted until the target portions  108  are approximately the same distance anterior of a coronal plane containing the mechanical axis as is optical element  32  on the surgical orientation device  12 . 
     In another embodiment, the distance between the optical element  32  of the surgical orientation device  12  and the coronal plane containing the mechanical axis can be measured directly with the target probe  18   a ,  18   b  itself (for example, using a target probe  18   a ,  18   b  that contains an adjustable marker), such that a desired length of the target portion  108  on the target probe  18   a ,  18   b  can be set directly. 
     Once the length of the target probe  18   a ,  18   b  is set, the user can palpate adjacent to a distal feature of the patient&#39;s tibia, such as for example the ankle, to find a location of the lateral malleolus. Once this location is found, the user can hold, couple, and/or affix a first target probe  18   a  adjacent to a distal feature of the patient&#39;s tibia, such as for example onto the lateral malleolus as shown in  FIG.  21 B . 
     The laser  42  can then be activated.  FIG.  21   b    shows the tibial preparation system  10 ′ with its laser  42  turned on. For example, an optical element  32  on the surgical orientation device  12  can be activated by pressing one of the user inputs  26  on the surgical orientation device  12 , and can emit a crosshair laser beam distally toward the ankle, and toward the first target probe  18   a.    
     With at least one cross-hair laser beam pointing towards the ankle, the knobs on the universal jig  16  can be adjusted until the laser beam illuminates a target shape  110  on the target portion  108  of target probe  18   a . As described above, the target shape  110  can be a cross-shaped object, slot, cross mark, T-shaped, L-shaped, or some other shape containing perpendicular lines that meet or intersect. The user can adjust the position of the universal jig  16  until the crosshair beam of the laser beam lines up in both directions along or through the target shape  110 . 
     In some embodiments, the target probe  18   a ,  18   b  can contain a sensor to detect feedback from the cross-hair beam of the laser and can be configured to emit noise or other feedback to confirm that the cross-hair beam of the laser has been positioned correctly on the target portion  108  of target probe  18   a ,  19   b.    
     Once the cross-hair beam of the laser is aligned with the target shape  110 , the user can input the orientation of the surgical orientation device  12  (and simultaneously cutting block  84 ), into the surgical orientation device  12  as a first reference position. For example, the user can press one of the user inputs  26  on the surgical orientation device  12 , and the surgical orientation device  12  can register and/or calculate the current orientation of the surgical orientation device  12  based on data collected from the sensor or sensors  40 . The orientation of the surgical orientation device  12  in this first reference position can be used to identify the orientation of a coronal plane that contains the mechanical axis of the leg. In one technique, data collected from the sensor  40  in connection with the probe  18   a  can also be used to determine a first reference point for identifying the location and/or orientation of a sagittal plane containing the same mechanical axis. 
     The user can then position a second target probe or probes  18   b  on the medial malleolus, the location of which may be determined by again palpating the ankle. Once the location of the medial malleolus is identified and the second target probe or probes  18   b  are held in place, the universal jig  16  can be adjusted until a beam of the cross-hair laser beam illuminates a desired target shape  110  on a second target probe  18 . 
     Once the second target probe  18   b  has been positioned properly, the surgeon can again press one of the user inputs  26  on the surgical orientation device  12 , and the surgical orientation device  12  can register and/or calculate the current orientation of the surgical orientation device  12  in the second reference position based on data collected from the sensor or sensors  40  inside the surgical orientation device  12 . The orientation of the surgical orientation device  12  in this second reference position can be used to identify the orientation of a plane extending through the tibia which contains the mechanical axis of the leg, and/or can be used to locate a second reference point for identifying the location and/or orientation of a sagittal plane containing the mechanical axis. 
     When using the surgical orientation device  12  to determine the first and second reference positions, output of the sensors  40  in the surgical orientation device  12  can be monitored after light is directed to the selected location in a manner that minimizes error in the reading. For example, a transient phase can be eliminated in the output of the sensors  40  to arrive at an accurate estimation of the given anatomical landmark and/or target probe  18 . The electronic control unit  1102  can be configured to perform stabilization algorithms or methods to minimize or substantially remove erroneous output caused by vibrational or other movements, as described above. 
     With continued reference to  FIGS.  21   a  and  21   b   , once information about both the first and second reference positions has been acquired and registered in the surgical orientation device  12 , the user can direct the surgical orientation device  12  to calculate the location of a desired point between the lateral malleolus and the medial malleolus. This desired point can lie within the aforementioned sagittal plane containing the mechanical axis. The desired point can vary, depending on the user&#39;s medical training and experience. For example, the desired point can be located midway between the lateral malleolus and medial malleolus, or 55% toward the medial malleolus from the lateral malleolus, or at some other predetermined location. 
     The user can use one or more user inputs  26  to provide commands to direct the surgical orientation device  12  to calculate the location of this desired point and to calculate the location and/or orientation of the sagittal plane containing this desired point. Once the surgical orientation device  12  has calculated where this desired point is, the surgical orientation device  12  can provide location feedback to the user, for example in the form of a visual signal or signals on the display  24 , indicating that the location of this desired point, and/or the location of the sagittal plane, has been calculated. 
     In some embodiments, two target probes  18   a  can be used, each with a cross target  110 . One of the target probes  18   a  can first be used to identify a coronal plane containing the mechanical axis, and both the target probes  18   a  can then be used to identify a sagittal plane containing the mechanical axis. Since the coronal plane can be registered by the first target probe  18   a  with a cross target  110 , the user can line up a vertical portion of the cross-hair laser beam (e.g. one which is parallel or coincident with a sagittal plane extending through the leg) with the vertical portion of the second target probe  18   a , and the location of the sagittal plane can be calculated. This alignment can be made without lining up both the horizontal and vertical portions of the cross-hair laser beam on the second target probe  18   a , since doing so can cause the orientation of the surgical orientation device  12  to deviate from the already registered coronal plane. 
     3. Adjusting an orthopedic fixture to set a cutting block orientation 
     Once the location of the coronal and sagittal planes containing the mechanical axis has been acquired and registered by the surgical orientation device  12 , the surgical orientation device  12  can calculate and store the location and orientation of the mechanical axis of the leg. Based on this stored information, the surgical orientation device  12  can be used to adjust the cutting block  84  in order to obtain a desired orientation for resection of the proximal tibia. For example, the universal jig  16 ,  16 ′ can be adjusted to move the surgical orientation device  12 . 
     With reference to  FIG.  2   , both a varus/valgus angle and posterior/anterior angle of the cutting block  84  can be set by the user. In order to adjust these angles of the cutting block  84 , the user can turn the knobs  90   a ,  96   a  on the ends of pins  90  and  96  on the universal jig  16 . Turning these knobs can change the angle and/or orientation of the varus/valgus adjustment block  82 , and posterior/anterior adjustment block  80 , respectively. As the varus/valgus adjustment block  82  and posterior/anterior adjustment block  80  are moved (e.g. rotated), the cutting block  84  can also be moved, along with the surgical orientation device  12 . 
     As the cutting block  84  is moved (e.g. swung) in a varus/valgus direction, the surgical orientation device  12  can provide a reading or readings on its display  24  indicating whether the surgical orientation device (and likewise the cutting block  84 ) is aligned with the sagittal plane containing the mechanical axis, or whether the cutting block  84  is angled at some degree relative to the sagittal plane containing the mechanical axis. For example, the surgical orientation device  12  can indicate on its display  24  a difference in degrees between the current orientation of the cutting block  84 , and an orientation of the cutting block  84  in which the cutting block  84  is aligned substantially or exactly parallel to (or exactly on) the sagittal plane containing the mechanical axis. 
     Similarly, as the cutting block is moved (e.g. swung) in a posterior/anterior direction, the surgical orientation device  12  can provide a reading or readings on its display  24  indicating whether the surgical orientation device (and likewise the cutting block  84 ) is aligned with the coronal plane containing the mechanical axis, or whether the cutting block  84  is angled at some degree relative to the coronal plane containing the mechanical axis. For example, the surgical orientation device  12  can indicate on its display  24  a difference in degrees between the current orientation of the cutting block  84 , and an orientation of the cutting block  84  in which the cutting block  84  is aligned substantially or exactly parallel to the coronal plane containing the mechanical axis. 
     In some embodiments, the cutting block  84 , or other cutting blocks described herein, can be attached to a universal jig after the universal jig has been adjusted. Thus, the final position of the cutting block can be adjusted, and the cutting block can then be attached, as opposed to being attached during the entire adjustment process. 
     The surgical orientation device  12  can further be useful in setting and/or confirming a resection depth of the tibia once the varus/valgus and posterior/anterior angles have been determined. For example, in a preferred arrangement, the user can activate the laser  42  (e.g. a proximal cross-hair beam laser) on the surgical orientation device  12  by pressing one of the user inputs  26 , and can hold or attach a device for confirming a cut line or plane, for example a mirror  226  as shown in  FIG.  22 A  of the system  210 . The mirror  226  can be coupled to or integrally formed with the universal jig  16  or other surgical component. The mirror  226  can be held or attached at a certain angle such that a horizontal beam of the cross-hair beam, extending, for example, parallel to a coronal plane, is reflected through an opening  102  on the cutting block  84  and onto the tibia, illuminating an area on the tibia which a cutting saw would cut through if moved through the cutting block  84 . The points of bone on the tibia which prevent the passage of the laser beam (and which are therefore illuminated by the laser) across the tibia are those which would be resected by the cutting saw. In the event that a different depth of the resection is desired, the user can adjust the cutting block  84  and reconfirm depth of resection. 
     C. Tibial Preparation System with Mechanical Referencing of a Distal Landmark 
     A tibia preparation system can be provided which uses a moveable orthopedic fixture with a probe to reference one ore more anatomical landmarks mechanically. The probe can comprise a mechanical swing arm. For example,  FIGS.  2   b    and  22 - 23  illustrate a tibial preparation system  210 . Tibial preparation system  210  is a variation on the tibial preparation system  10  described above, and can comprise the surgical orientation device  12  described above, as well as a universal jig  212 . The tibial preparation system  210  can differ from the tibial preparation system  10 , for example, in that the system  210  can utilize a mechanical structure or structures to locate anatomical landmarks adjacent the distal tibia, as opposed to using a target or targets with a light source as described above. 
     1. Orthopedic Fixture for Orienting a Surgical Orientation Device and/or Cutting Block in Multiple Degrees of Freedom 
     An orthopedic fixture can be provided for orienting a surgical orientation device and/or cutting block. For example, the universal jig  212  can be similar to the universal jig  16  described above. With reference to  FIGS.  22 A-C , the universal jig  212  can comprise a base member  214  operatively coupled to a posterior/anterior adjustment block  216 , and/or a varus/valgus adjustment block  218 . 
     a. Base Member for Providing an Anchored or Fixed Initial Position of an Orthopedic Fixture 
     A base member can be provided which anchors an orthopedic fixture and/or provides a fixed initial position of a moveable orthopedic fixture. For example, the base member  214  can comprise a structure which is rigidly and/or fixedly attached to an anatomical structure, such as a bone. In a preferred arrangement, the base member  214  can comprise a proximal mounting structure, such as for example at least two base member attachment openings (not shown) which are in the form of holes extending through the base member  214 . Each of the base member attachment openings can be configured to receive a fastening device, such as for example a screw, to anchor the base member  214  into a bone or other anatomical structure and fix the base member  214  relative to the bone or anatomical structure. For example, the base member  214  can be mounted on a proximal portion of the tibia. 
     The base member  214  can further comprise an elongate base member rod  220 , similar to rod  92  described above. The elongate base member rod  220  can extend distally from an upper, or proximal, portion of the base member  214 , and can include a brace-like structure  222  on its distal end, similar to structure  94  described above. The brace-like structure  222  can be curved to better conform to the curvature of the anatomy. The brace-like structure  222  can be used to brace and/or hold the universal jig  212  against the patient&#39;s skin overlying the tibia during the knee replacement procedure. For example, and as described above, the brace-like structure  222  can provide a stabilizing force. 
     Similar to the system  10 , the base member  214  can be operatively connected to a cutting block  224 , as described further herein. The cutting block  224  can be located proximal the base member  214 , and can move relative to the base member  214 . 
     The base member  214  can further comprise a device for confirming a cut line or plane, as described above. For example, the base member can comprise a mirror  226 . The mirror  226  can be formed as part of the cutting block  224 , or other surgical component. The mirror  226  can comprise a 45 degree (or other angle) reflective surface, which can reflect a light beam or beams along the surface of an anatomical feature. For example, and as described above, the mirror  226  can be angled and/or fixed such that a beam of a cross-hair laser beam is reflected through an opening  102  on the cutting block  224  and onto the tibia, illuminating an area on the tibia which a cutting saw would cut through if moved through the cutting block  224 . 
     b. Device for Adjusting a Posterior/Anterior Slope of a Cutting Block 
     An adjustment device can be provided which can be used to adjust the orientation of a surgical orientation device and/or cutting block. For example, and with continued reference to  FIGS.  22  and  23   , a posterior/anterior adjustment block  216  can comprise a structure that is moveable (e.g. rotatable) in at least one of a posterior and anterior direction. For example, the universal jig  212  can include at least one knob  228 . When the knob  228  is turned, the posterior/anterior adjustment block  216  can rotate about a hinge, pin, or other structure, such as for example pin  229 , in the universal jig  212  to change a posterior/anterior angle of the cutting block  224 . As discussed further below, the surgical orientation device  12  can be coupled to the adjustment block  216  for movement therewith. Thus, movement of the adjustment block  216  can also change the plane angle of the surgical orientation device  12 . 
     The posterior/anterior adjustment block  216  can further comprise a connector  230 . The connector  230  can comprise a structure which operatively connects the posterior/anterior adjustment block  216  to the surgical orientation device  12 . For example, the connector  230  can comprise a structure which facilitates translational movement of the surgical orientation device  12  relative to the posterior/anterior adjustment block  216 . The connector  230  can comprise a channel  231 . The channel  231  can facilitate movement of an upper, or proximal, portion  232  of the posterior/anterior adjustment block  216  relative to the connector  230  (e.g. sliding movement). 
     With reference to  FIGS.  22   b    and  23 , the connector  230  can comprise, or be attached to, a clamp  233 . The clamp  233  is a coupling device similar to the coupling device  14  described above. For example, the clamp  233  can be secured to the back side of the surgical orientation device  12  to couple the surgical orientation device  12  to another structure or structures. In the tibia preparation system  210 , the clamp  233  can be used to couple the surgical orientation device  12  to the posterior/anterior adjustment block  216 . 
     With reference to  FIGS.  22 - 23   , the connector  230  can further comprise, or be attached to, a swing arm  234 . The swing arm  234  can comprise a landmark acquisition device which can be used to locate and/or identify specific landmarks, such as for example landmarks adjacent the distal tibia. The swing arm  234  can comprise an elongated structure or structures, such as for example a metal rod or rods, which can extend from a proximal portion of the tibia (e.g. near the knee joint) to a distal portion of the tibia (near the ankle). The swing arm  234  can extend generally vertically (e.g. in a proximal to distal direction) behind the surgical orientation device  12 , and/or can be hinged, such that at least one of a distal portion  236  and proximal portion  238  of the swing arm  234  can swing and/or rotate relative to the other proximal or distal portion  236 ,  238 . For example, the distal and proximal portions  236 ,  238  can comprise elongate structures connected by a hinge portion  239  located between the distal and proximal portions  236 ,  238 . The hinge portion  239  can permits relative movement of the distal portion  236  with respect to the proximal portion  238 . In other embodiments the swing arm can comprise more than one hinge portion  239 . The hinge portion or portions  239  can be located at other locations than that shown in  FIGS.  22   a ,  22   b   , and  23 . The swing arm  234  can also comprise a distal end  240 . The distal end or tip  240  can comprise a pointed structure or structures, and/or a distal mounting structure, which can contact and/or couple with an anatomical landmark. For example, the hinge portion  239  of the swing arm  234  can be moved or swung until the tip  40  is in contact with, or is coupled to, an anatomical landmark adjacent the distal tibia. 
     Similar to the universal jig  16  described above, the posterior/anterior adjustment block  216  of universal jig  210  can be operatively connected to the cutting block  224 . Movement of the posterior/anterior adjustment block  216  and cutting block  224  can be linked (e.g. by pins, hinges, etc.) such that movement of the posterior/anterior adjustment block  216  can cause similar or identical movement of the cutting block  224 . Movement of the cutting block  224  can, at the same time, cause similar or identical movement of the surgical orientation device  12 . 
     While the swing arm  234  is described as forming part of the posterior/anterior adjustment block  216 , the swing arm  234  can alternatively be formed as part of the base member  214  and/or varus/valgus adjustment block  218  described below. Similarly, while the base member  214  is described as being separate from the posterior/anterior adjustment block and varus/valgus adjustment block  218 , the base member can, in at least some embodiments, refer generally to a combination or combinations of the posterior/anterior adjustment block  216 , swing arm  234 , and/or varus/valgus adjustment block  218 . 
     c. Device for Adjusting a Varus/Valgus Slope of a Cutting Block 
     An adjustment device can be provided which can be used to adjust the orientation of a surgical orientation device and/or cutting block. For example, and with continued reference to  FIGS.  22 A-C , the varus/valgus adjustment block  218  can comprise a structure which is moveable (e.g. rotatable) in at least one of a varus/valgus direction. For example, the universal jig  212  can include at least one knob  242 . When the knob  242  is turned, the varus/valgus adjustment block  218  can rotate about a hinge, pin, or other structure in the universal jig  212  to change a varus/valgus angle of the surgical orientation device  12 , as well as the cutting block  224 . 
     Movement of the varus/valgus adjustment block  218  can correspond to or result in movement of the posterior/anterior adjustment block  216 . For example, a portion or portions of the varus/valgus adjustment block  218  can rest within and/or be contacted on either side by portions of the posterior/anterior adjustment block  216 , such that any movement of the varus/valgus adjustment block  218  in a varus or valgus direction likewise causes similar or identical varus/valgus movement of the posterior/anterior adjustment block  216 . 
     d. Cutting Block which can be Oriented in a Posterior/Anterior, and/or a Varus/Valgus, Direction for Bone Resection 
     A cutting block, or other orthopedic fixture, can be provided for bone resection. The cutting block can be oriented with the aid of a surgical orientation device, an orthopedic fixture, or a surgical orientation device and an orthopedic fixture. The cutting block  224 , as described above, can comprise at least one opening  102 . For example, one opening  102  can comprise an elongate slit along a width of an upper, or proximal, portion of the cutting block  224  for receiving and guiding a saw, blade, or other cutting tool. Other openings  102   a  (not shown) can comprise holes for insertion of an anchoring pin or pins, or other structures. 
     2. Modified Orthopedic Fixture 
     The system  210  described above can be modified. For example,  FIGS.  23 A and  23 B  show a system  210 ′. The system  210 ′ is a modification of system  210 , and can comprise a universal jig  212 ′ similar to the jig  212  described above. The system  210 ′ can also comprise a surgical orientation device  12 . The universal jig  212 ′ can be adjusted by moving (e.g. pivoting) a swing arm  234 ′ by hand about a proximal portion  212   a  of the universal jig  212 ′, rather than adjusting knobs by hand. The proximal portion  212   a  can comprise a varus/valgus adjustment device (such as the one described above), a posterior/anterior adjustment device (such as the one described above), and/or a pivot pin or pins. Knobs can be included for locking the swing arm  234 ′ in place. In some embodiments the universal jig  210 ′ can comprise knobs for fine-tune adjusting. In one embodiment, the swing arm  234 ′ can comprise an extendable portion that enables a distal portion thereof to be extended away from a base portion. The distal portion can include a moveable rod extendable from another member (e.g., a hollow rod) that is fixed to the base. The distal portion can be fastened in any of a range of positions relative to the fixed, proximal portion. The distal portion preferably can be clamped in a range of positions. In one embodiment a distal portion of the swim arm  234 ′ can be coupled with a block to enable adjustment of a tip into contact with anatomical landmarks. In some embodiments, the jig  212 ′ can be coupled with a proximal tibia and the arm  234 ′ is adapted to contact lateral or medial malleolus. In some embodiments, the jig  212 ′ can be coupled with a distal femur and the arm  234 ′ is adapted to contact a structure corresponding to a femoral head, a lesser trochanter or a greater trochanter, as discussed herein. 
     With reference to  FIG.  23 A , the modified system  210 ′ can comprise a measuring device  109   a , and a measuring device  109   c . As described above with respect to system  10 , the measuring device  109   a  can be used to measure a distance between an A/P point along the top of the tibia and a coronal plane parallel to the coronal plane containing the mechanical axis. The measuring device  109   a  can include a marking or markings providing a visual indication of distance, and can slide within a block  109   d . The measuring device  109   c  can also measure a distance, and can include a marking or markings to provide a visual indication of distance. 
     D. Acquiring Orientation Information Using Mechanical Referencing of a Distal Landmark 
     1. Registering the Coronal and Sagittal Planes 
     After pre-operative planning for a joint replacement procedure, the tibial preparation system  210 ,  210 ′ described above can be used to identify the location and orientation of an axial line, as well as to orient a cutting block relative to the axial line. 
     For example, once the desired varus/valgus and posterior/anterior angles for resection have been determined pre-operatively for a knee replacement procedure as describe above, the tibial preparation system  210 ,  210 ′ can be provided. In one technique at least some of the components are modular, enabling using such component with multiple other orthopedic components. As such, the tibial preparation system  210 ,  210 ′ can be assembled from these components. 
     The surgical orientation device  12  can be coupled to the universal jig  212 , and the tibial preparation system  210 ,  210 ′ can be positioned adjacent the proximal tibia on an anterior side of the tibia (i.e. front of the leg). In other techniques, the tibial preparation system  210 ,  210 ′ is partially or completely pre-assembled or integrated. 
     In a preferred arrangement, the tibial preparation system  210 ,  210 ′ can be positioned such that the surgical orientation device  12  is generally centered with the insertion of an anterior cruciate ligament and a medial tibial insertion of the patella tendon in a patient&#39;s knee, for example as described above with respect to tibial preparation system  10 . Once centering has been achieved, the base member  214  of the universal jig  212 ,  212 ′ can be pinned, anchored, and/or otherwise secured to the tibia, such that the base member  214  has zero or substantially zero degrees of freedom relative to the tibia. 
     The user can then slide the connector  230  in a posterior and/or anterior direction (e.g. translate the connector  230  forwards or backwards), until the swing arm  234 ,  234 ′ is located proximate an anatomical landmark. For example, the connector  230  can slide until the tip  240  of the swing arm  234 ,  234 ′ is located adjacent the lateral malleolus on the patient&#39;s ankle. The lower, or distal, portion  238  can swing and/or rotate during such movement in order to get the tip  240  closer to the lateral malleolus. 
     In a preferred arrangement, measuring devices  109   a  and  109   c , such as the ones illustrated in system  210 ′, can be used. For example, one measuring device  109   a  can be located proximal the universal jig  212  or  212 ′, and another measuring device  109   c  can be located at a distal end of the swing arm  234  or  234 ′. 
     The measuring devices  109   a  can be moved until a tip of the measuring device  109   a  is resting over the insertion point of the anterior cruciate ligament in the knee, and/or a soft point on the top of the tibia commonly referred to as the A/P point of the mechanical axis. As described above, this point is located along a tibial spine on top of the tibia, and generally marks the location of a point along the mechanical axis of the leg. 
     The measuring device  109   c  can then be moved until a tip  240  or  240 ′ is positioned next to the lateral malleolus (for example as shown in  FIG.  23 B ). For example, the user can palpate adjacent to a distal feature of the patient&#39;s tibia, such as for example the ankle, to find a location of the lateral malleolus of the tibia. Once this location is found, the user can position the tip  240 ,  240 ′ of the swing arm  234 ,  234 ′ adjacent to a distal feature of the patient&#39;s tibia, such as onto the lateral malleolus as shown in  FIG.  23 B . 
     The measuring devices  109   a ,  109   c  can then be adjusted until portions  109   d  are approximately the same distance anterior of a coronal plane containing the mechanical axis, placing the surgical orientation device  12  in an orientation parallel to that of the coronal plane containing the mechanical axis. Each measuring device  109   a ,  109   c  can have analogous numbering systems. For example, the measuring devices  109   a ,  109   c  can comprise etchings, or markings. 
     The user can activate the surgical orientation device  12 , such as by pressing one of the user inputs  26  on the surgical orientation device  12 . Once activated, the, surgical orientation device  12  can register (e.g. record) the orientation of the surgical orientation device as a first reference position. For example, the surgical orientation device  12  can register and/or calculate the current orientation of the surgical orientation device  12  based on data collected from the sensors  40 . The orientation of the surgical orientation device  12  in this first reference position can be used to identify and register the orientation of a coronal plane which contains the mechanical axis of the leg, as well as to determine a first reference point for identifying the location and/or orientation of a sagittal plane containing this same mechanical axis. 
     The user can then swing the swing arm  234 ,  234 ′ over to the other (e.g., medial) side of the leg, such that the tip  240 ,  240 ′ is located adjacent the medial malleolus. For example, the user can turn the knob  242  on system  210  so that the posterior/anterior adjustment block  216 , connector  230 , and swing arm  234  are moved in a varus/valgus manner, until the swing arm  234  has moved to the other side of the leg. The lower, or distal, portion  238  of the swing arm  234  can swing and/or rotate during such movement in order to avoid hitting or contacting the an anterior side of the leg. 
     The user can then again palpate the ankle, and position the tip  240 ,  240 ′ of the swing arm adjacent to the medial malleolus. Once the location of the medial malleolus is identified, the user can press one of the user inputs  26  on the surgical orientation device  12  to cause the surgical orientation device  12  to determine the orientation of the surgical orientation device  12  in a second reference position. For example, the surgical orientation device  12  can register and/or calculate the current orientation of the surgical orientation device  12  based on data collected from the sensors  40 . 
     The orientation of the surgical orientation device  12  in this second reference position can be again be used to identify the orientation of a coronal plane extending through the tibia that contains the mechanical axis of the leg, and/or can be used to locate a second reference point for identifying the location and/or orientation of a sagittal plane containing the same mechanical axis. 
     When using the surgical orientation device  12  to determine the first and second reference positions, output of the sensors  40  in the surgical orientation device  12  can be monitored in a manner that minimizes error in the reading. For example, a transient phase can be eliminated in the output of the sensors  40  to arrive at an accurate estimation of the given anatomical landmark as discussed above. 
     Once information about both the first and second reference positions has been acquired and registered in the surgical orientation device  12 , the surgical orientation device  12  can determine (e.g. calculate) the location of a desired plane between the lateral malleolus and the medial malleolus. As described above, the desired plane corresponds to the sagittal plane containing the mechanical axis. The desired plane can vary, depending on factors such as the patient&#39;s specific anatomy and the surgeon&#39;s training and experience. For example, the desired plane can be located midway between the lateral malleolus and medial malleolus, or 55% toward the medial malleolus from the lateral malleolus, or at some other predetermined location. 
     The user can use one or more user inputs  26  to direct the surgical orientation device  12  to calculate the location of and/or orientation of the sagittal plane. Once the surgical orientation device  12  has calculated where the sagittal plane is, the surgical orientation device  12  can provide location feedback to the user, for example in the form of a visual signal or signals on the display  24 , indicating that the location of the sagittal plane has been calculated. 
     2. Adjusting an Orthopedic Fixture to Set the Orientation of a Cutting Block 
     Once the locations of the coronal and sagittal planes containing the mechanical axis have been acquired (e.g. registered) by the surgical orientation device  12 , the surgical orientation device  12  can calculate and store the location and orientation of the mechanical axis of the leg. Based on this stored information, the surgical orientation device  12 , and universal jig  212 ,  212 ′, can be used to adjust a cutting block in order to obtain a desired orientation for resection of the top of the tibia. 
     For example, and as described above with respect to tibial preparation system  10 , the knob or knobs  90   a ,  96   a  on the universal jig  212  can be turned to set a desired varus/valgus and posterior/anterior angle for resection. During this adjustment, the surgical orientation device  12  can provide a reading or readings on its display  24  indicating whether the surgical orientation device (and likewise the cutting block  224 ) is aligned with the sagittal plane and/or coronal plane containing the mechanical axis, or whether the cutting block  224  is at an acute angle relative to the sagittal plane and/or coronal plane containing the mechanical axis. 
     Once the orientation of the cutting block  224  has been adjusted and set, the mirror  226  can be used. For example, the user can press one of the user inputs  26  on the surgical orientation device  12  to direct a laser beam out of the optical element  32  and onto the mirror  226 . The laser beam can be reflected through an opening  102  on the cutting block  224  and onto the tibia, illuminating an area on the tibia for resection through the cutting block  224 . The points of bone on the tibia illuminated by the laser are those which would be resected by the cutting saw. In the event that a different depth of the resection is desired, the user can adjust the cutting block  224  and reconfirm depth of resection. 
     E. Other Target Systems and Methods 
     While the tibial preparation systems  10 ,  10 ′,  210 , and  210 ′ and their methods of use are described above specifically in terms of a system that incorporates a surgical orientation device  12 , a universal jig  16  or  212 , a laser system, and/or a set of target probes  18  or swing arm  234 , in other embodiments other components can be used to determine anatomical planes on the human body and/or facilitate alignment of surgical devices, systems, and/or anatomical parts. 
     For example, a light system other than a laser system can be attached to a surgical orientation device that is otherwise similar to the surgical orientation device  12  described above. A user can position the surgical orientation device until the light is illuminating a target, such as for example an anatomical landmark, and the surgical orientation device can acquire this first position as a reference. The user can then position the device until the laser is illuminating another anatomical landmark and the surgical orientation device can acquire this second position as a reference. Third, fourth, and/or additional reference positions can also be obtained in the same technique. 
     The surgical orientation device can employ an algorithm that calculates some appropriate point (e.g. a midpoint), as directed by the user, between the two anatomical landmarks that corresponds to the position of a desired anatomical plane. The surgical orientation device can also provide feedback to the user to position the surgical orientation device in alignment with this plane. Alternatively, if a desired plane or axis can be determined based on the position of one, two, three, or more anatomical landmarks, a system can be used to make such determination based on a light-mapping of such landmark(s) and corresponding calculations performed by a surgical orientation device. 
     In some embodiments, the surgical orientation device  12 , or other surgical orientation device, can be held at some distance from the body by the user. The surgical orientation device  12  can be used as a registration guide. For example, the user can activate a light system on the surgical orientation device that illuminates a line along the body, such as for example along the mechanical axis. Once the line is visibly aligned along the mechanical axis, the surgical orientation device can press a user input  24  and the surgical orientation device can register an orientation of the surgical orientation device. This orientation information can later be used to align orthopedic fixtures or cutting blocks. 
     In some embodiments, the target systems described herein, or other target systems, can be used to locate targets on the hip, femur, or other areas of the body, and to use such targets to acquire planes or axes extending through the body. For example, the universal jig  16  can be attached on the femur, and the system  10 , including target probes  18   a ,  18   b  described above, can be used to locate landmarks such as the greater trochanter, center of the head of a femur, a point of entrance of a ligament, or other landmarks, and use these landmarks to reference an anatomical plane or planes. Similarly, the universal jig  212  can be attached on the femur, and the system  210 , including swing arm  234 ′ can be used to reference an anatomical plane or planes. 
     F. Tibial Preparation System with Landmark Acquisition Assembly and Extramedullary Alignment Guide 
       FIGS.  3   a  and  3   b    show a tibial preparation system  310  (shown as assemblies  310   a  and  310   b ) for use in a joint replacement procedure, such as for example a knee replacement procedure. The tibial preparation system  310  can comprise the surgical orientation device  12  described above, the coupling device  14  described above, a landmark acquisition assembly  312 , and an extramedullary alignment guide  314 . The tibial preparation system  10  can be different from the systems  10  and  210 , for example in that the system  310  can utilize both a structural alignment guide and surgical orientation device alongside a lateral side of the tibia (e.g. held alongside the tibia) to locate a plane containing the mechanical axis, and a second structural alignment guide (with surgical orientation device) attached along the anterior side of the tibia. 
     1. Orthopedic Fixture for Acquiring Anatomical Planes or Axes 
     An orthopedic fixture can be provided which can be used to identify and acquire anatomical planes and/or axes. For example,  FIG.  24    shows an embodiment of a landmark acquisition assembly  312 . The landmark acquisition assembly  312  can comprise an orthopedic fixture which can be used to identify the location of an axial line or plane. The landmark acquisition assembly  312  can comprise a structure or structures for contacting an anatomical landmark or landmarks in order to obtain an alignment of an axis or plane extending through those anatomical landmarks. 
     For example, in a preferred arrangement, the landmark acquisition assembly  312  can comprise an elongate member, for example a primary rod  316 , with a proximal end  317   a  and a distal end  317   b . The landmark acquisition assembly  312  can further comprise a connecting element or elements  318 , and secondary rod or rods  320 . The secondary rod or rods  320  can comprise transverse members coupled with each of the proximal and distal ends  317   a ,  317   b  of the primary rod  316 . While the embodiment shown in  FIG.  24    includes a single primary rod  316 , two connecting elements  318 , and four secondary rods  320 , other embodiments can include other numbers or configurations of primary rods, connecting elements, and/or secondary rods. In some embodiments, the connecting element  3218  can be made integral with the primary rod  316  or a secondary rod  320 . 
     The landmark acquisition assembly  312  can be arranged, for example, such that each connecting element  318  connects the primary rod  316  to at least one secondary rod  320 . The secondary rods  320  and primary rod  316  can be at right angles to one another, as illustrated in  FIG.  11   , or can be at angles other than right angles. 
       FIG.  25 A  shows a first portion  322  and a second portion  324  of a cross-section of the primary rod  316 . The first portion  322  can be generally rounded, while the second portion  324  can be generally flat. The second portion  324  can facilitate connection with other components or devices in the system  310 . For example, the second portion  324  can be configured to inhibit a connected device from rotating about or pivoting about the primary rod  316 . The first and second portions  322 ,  324  can be arranged to permit only one orientation for the landmark acquisition assembly  312 . Other configurations and shapes for a first portion  322  and second portion  324  besides those illustrated in  FIG.  25    are also possible. 
       FIG.  25 B  shows ends  326  of the secondary rod  320  which can be narrowed and/or or pointed. The ends  326  can be used to contact portions of the human body in order to locate and/or pinpoint landmarks on the body, such landmarks including but not limited to the proximal tibia near the ligamentous attachment of the collateral ligaments, and the malleolus protruding out of the ankle region. Other shapes and configurations for the ends  326  are also possible. The secondary rod  320  can further include ribs, protrusions, or other structures which can engage the connecting element  318  and permit the secondary rod or rods  320  to be adjusted within the connecting element  318 . 
       FIG.  26    shows an opening  328  in the connecting element  318  which can receive the primary rod  316  and facilitate connection of the primary rod  316  to another structure or structures. As illustrated in  FIG.  26   , the opening  328  can be shaped to receive the primary rod  316 . The opening  328  can include a rounded portion and a flat portion both configured to engagingly receive the first portion  322  and second portion  324  of the primary rod  316 . 
     The connecting element  318  can further include additional openings shaped to receive, for example, the secondary rods  320  shown in  FIG.  25   . The secondary rods  320  can be threaded, and openings of the connecting element  218  can include internal threads to receive the secondary rods  320 . In a preferred arrangement, the opening  328 , or other openings in the connecting element  318 , can include notches, or grooves, which provide tactile feedback to a user when the primary rod  316  and/or secondary rod or rods  320  are sliding through the openings. The opening  328  or other openings in the connecting element  318  can extend entirely through the connecting element  318 , thus allowing the primary rod  316  and/or secondary rod or rods  320  to be inserted entirely through the connecting element  318 . 
     2. Orthopedic Fixture for Orienting a Surgical Orientation Device 
     An orthopedic fixture can be provided for orienting a surgical orientation device and/or cutting block. For example,  FIG.  27    shows an extramedullary alignment guide  314 . The extramedullary alignment guide  314  can comprise an orthopedic fixture which can be attached, at least in part, to an anatomical location, and can extend outside and/or along an appendage of the body. The extramedullary alignment guide can be used to aid in orienting a surgical orientation device, such as for example surgical orientation device  12 , and for locating an axial line or plane. 
     As illustrated in  FIG.  27   , the extramedullary alignment guide  314  can comprise a distal mounting structure, such as for example a clamping portion  330 , which can clamp onto a distal feature of a patient&#39;s leg or tibia, such as for example an ankle. The extramedullary alignment guide  314  can further comprise an elongate, extended rod  332  which can extend outside the body and generally parallel to the tibia. The clamping portion  330  can include a slide  334 , which permits the extended rod  332  to slide and/or swing in front of the leg and tibia. The slide  334  can comprise an elongate recess or recesses along the clamping portion. The extended rod  332  can include a portion which fits within these recesses, and slides back and forth. 
     The extramedullary alignment guide can further comprise, or be attached to, a proximal mounting structure, such as for example a cutting block  84 . The cutting block  84  can be identical to the cutting block  84  described above. For example, the cutting block  84  can comprise an opening  102  for insertion of a cutting tool (e.g. a cutting saw). 
     G. Acquiring Orientation Information Using a Landmark Acquisition Assembly and Extramedullary Alignment Guide 
     After pre-operative planning for a joint replacement procedure, the tibial preparation system  310  described above can be used to identify the location and orientation of an axial line, as well as to orient a cutting block relative to the axial line. 
     For example, the leg to be operated on can be secured by placement in a leg holder, and the knee can be exposed using standard surgical procedure. During this time an extramedullary alignment guide, for example the extramedullary alignment guide  314 , can be held in position adjacent the leg. A single spike on an end of the extramedullary alignment guide can be placed in a proximal medial tibial spine, such that an end of the extramedullary alignment guide is in position over the proximal medial tibial spine. Alternatively, a non-spiked rod can be used with an ankle clamp holding the guide in place. 
     Resection depth of the tibia can then be determined by, for example, using a stylus on the extramedullary alignment guide. For example, a depth of resection can be determined by aligning the stylus length-wise, parallel with the tibia, with the depth of resection being determined by the point of contact between the tip of the stylus and the lowest point of the medial condyle of the tibia. 
     Once the desired varus/valgus and posterior/anterior angles for resection have been determined pre-operatively for a knee replacement procedure, and the resection depth has been determined, the tibial preparation system (referring to system  310   a ) can be assembled as shown in  FIG.  3   a   . For example, the surgical orientation device  12 , coupling mechanism  14 , and landmark acquisition assembly  312  can be coupled together, and the landmark acquisition assembly  312  can be positioned laterally alongside the tibia and outside of the leg. 
       FIGS.  28  and  29    show the tibial preparation system  310   a  located laterally alongside the tibia. Specifically,  FIGS.  28  and  29    show the tibial preparation system  10  being used to locate and reference an orientation of an axial line, in this case the mechanical axis extending through the lower (e.g. distal) leg. 
     In order to reference the orientation of the mechanical axis, the secondary rods  320  on the landmark acquisition assembly  312  can be adjusted such that their pointed ends  326  contact specified landmarks on the body. These landmarks can be pre-marked on the lower leg prior to a knee joint replacement procedure. Location of the landmarks can be acquired, for example, prior to a resection of the proximal tibia, with the tibia subluxed sufficiently to expose the tibial plateaus. 
     As shown in  FIGS.  28  and  29   , the tibia preparation system  310   a  can be used to acquire the mechanical axis in a coronal plane (i.e. acquire the orientation of a coronal plane containing the mechanical axis). For example, the secondary rods  220  can be adjusted and positioned such that one secondary rod  220  contacts the lateral collateral ligament of the proximal fibula head and another secondary rod  320  contacts the apex of the lateral malleolus. Once the secondary rods  320  have been adjusted, and are in contact with the aforementioned anatomical landmarks, the orientation of the mechanical axis can be obtained. 
     One of the user inputs  26  on the surgical orientation device  12  (e.g. a middle button below the display  24 ) can be pushed to record and/or register the orientation of the mechanical axis. The landmark acquisition assembly  312  can then be moved slightly back and forth until the surgical orientation device  12  indicates that the surgical orientation device  12  has acquired a plane containing the mechanical axis and verifies that the orientation has been recorded in the surgical orientation device  12 . This indication can include, for example, a reading of zero on display  24 , or some other signal. In a preferred arrangement, the display  24  can display a zero degrees reading and a flashing light (e.g. a green light), as shown in  FIG.  29   . 
     Once the surgical orientation device  12  has acquired an orientation of the mechanical axis, the surgical orientation device  12  and coupling device  14  can be removed from the landmark acquisition assembly  312 , and the tibia preparation system can be re-assembled into system  310   b  such that the surgical orientation device  12  and coupling device  14  are coupled with the extramedullary alignment guide  314 . 
       FIG.  30    shows the tibia preparation system  310   b  in an assembled state. In a preferred arrangement, the extramedullary alignment guide  214  can be aligned with the front of the leg. The clamping portion  330  can be used to clamp and/or secure a lower, or distal, portion of the extramedullary alignment guide  314  to the patient&#39;s ankle. 
     The extramedullary alignment guide  314  can be moved (e.g. rotated) in a first degree of rotation (e.g. roll) until the sensor or sensors  40  in the surgical orientation device  12  observe that the surgical orientation device  12  is in a plane parallel to the coronal plane containing the mechanical axis of the leg. Once the sensor or sensors  40  inside the surgical orientation device  12  observe that the surgical orientation device  12  is in this orientation, the surgical orientation device  12  can provide an indication to the user. For example, the surgical orientation device  12  can display zero degrees and a flashing light on the display  24 . In a preferred arrangement, a pictorial representation of a bubble can be displayed that, for so long as the surgical orientation device  12  remains aligned with gravitational zero within an allowable range, stays within the confines of two vertical lines, each on one side of the bubble. The two vertical lines marking the confines of the “level” orientation range can correspond to a relative angle or tilt of plus and minus three degrees or plus and minus one degree, for example. In another embodiment, the graphical display of a bubble can be combined with a secondary indication to cue the user as to the state of alignment. For example, if the bubble moves beyond the lines, the background color of the screen behind the bubble can change from a first state (e.g., a first color, such as green) to a second state (e.g., a second color, such as amber) to indicate that the orientation is out of the acceptable range. Once the user has received this indication, the user can press a user input  26  (e.g. a middle button below display  24 ), confirming and/or registering the orientation of the surgical orientation device  12 . 
     The extramedullary alignment guide  314  can then be moved (e.g. rotated) in a second degree of rotation (e.g. pitch) until the sensor or sensors  40  observe that the surgical orientation device  12  is in a plane parallel to the coronal plane containing the mechanical axis of the patient&#39;s leg. Once the sensor or sensors  40  inside the surgical orientation device  12  observe that the surgical orientation device  12  is in this orientation, the surgical orientation device  12  can again provide an indication to the user. For example, the surgical orientation device  12  can display zero degrees and a flashing green light on the display  24 , and/or a bubble as described above.  FIG.  31    shows such a flashing light on a display  24 . Once the user has observed this light or other indication, the user can press a user input  26  (e.g. a middle button below display  24 ), confirming and/or registering the orientation of the surgical orientation device  12 . 
     In some embodiments, the surgical orientation device can provide an indication when the surgical orientation device  12  is aligned in both degrees of freedom at the same time, rather than providing an indication each time separately. The user can then press the user input  26  once, rather than twice, to confirm registration of the orientation of the surgical orientation device  12 . 
     In yet other embodiments, the surgical orientation device  12  can monitor and store the output of tilt meter sensors  40  in the surgical orientation device  12 , such that when the tilt meter sensors  40  have been steady for a certain period, the surgical orientation device  12  can record the output to confirm and/or register the orientation of the surgical orientation device  12 . In one technique, the surgical orientation device  12  can average the data recorded over a period of time (e.g. data recorded over the last second or several seconds prior to pressing a user input  26 ) and use the average as the acquired data for the coronal plane. This process can be used in other instances of the procedures described herein, for example when the surgeon or other medical personnel is directing the surgical orientation device  12  to acquire a plane or orientation of the surgical orientation device  12 . This method can be advantageous in that it can reduce and/or eliminate inaccuracies caused by physical movement during a key-press (or other force imposed by the surgeon or other medical personnel onto the surgical orientation device  12 , electrical noise due to the current flow during a key-press (or other user action), other vibrational movement, or electrical and physical (audio) noise. In certain embodiments, the surgical orientation device  12  can be configured to identify the data corresponding to the time a button is pressed and then use the most recent “good” data obtained before the button was pressed by the user (for example, before the fluctuations in the data occurred due to the button press). 
     After registering the orientation of the mechanical axis as described above, the resection depth can be verified with a stylus.  FIG.  32    shows a stylus  336 . The stylus  336  can be attached to the extramedullary alignment guide  214 . The stylus  336 , or other surgical instrument, can be used to confirm and/or select a desired depth of resection for the tibial cut. This resection depth can be specified, for example, in an implant manufacturer&#39;s technique guide, and can help determine what size prosthetic component or components to use for the replacement knee joint. 
     The user can then orient the cutting block  84  into the pre-operatively determined varus/valgus and posterior/anterior angles for resection. For example, the extended rod  332  of the extramedullary alignment guide  214  can be adjusted (e.g. swung) in the sagittal (i.e. flexion/extension) plane in order to move the cutting block  84  into the pre-operatively determined posterior/anterior angle. In one arrangement, a lower, or distal, portion of the extended rod  332  can be moved and/or adjusted further away from or closer to the clamping portion  330 .  FIGS.  33 A and  33 B  illustrate movement of the extended rod  332  towards the clamping portion  330 . By moving the distal, end of the extended rod  332  away from or closer to the clamping portion  330  of the extramedullary alignment guide  313 , the posterior/anterior angle the cutting block  84  can be altered. 
     The extramedullary alignment guide  314  can additionally include markings, for example, which give an indication of the angle created by adjustment of the extended rod  332 . In a preferred arrangement, the surgical orientation device  12  can also provide a read-out on its display  24  of the angle of orientation of the resection plane created by moving the extended rod  332 . 
     Once the extended rod  332  is positioned as desired, a first mounting pin  333 , or other anchoring device, can be inserted through the cutting block  84 , for example as shown in  FIGS.  34 A and  34 B . Once this first mounting pin  333  is inserted, the cutting block  84  and extending rod  332  can be restricted from movement in all but a varus/valgus plane along the front of the tibia. 
     The user can then locate the sagittal plane containing the mechanical axis through use of a laser guide or guides. For example, the user can press one of the user inputs  26  (e.g. the middle button beneath the display  24 ) on the surgical orientation device  12  to activate a laser system in the surgical orientation device  12 . When the laser system is activated, the optical elements  32  on the top and bottom of the surgical orientation device  12  can emit red (or other color) laser beams out of the surgical orientation device  12 . The laser beams can be in the form of lines, planes, cross-hairs, or other configurations. 
     Other locations for a laser system or systems can also be used. For example, the laser system can be attached to or integrated with the primary rod  316 , secondary rods  320 , and/or adjacent the surgical orientation device  12 . In some embodiments, the laser system can be an entirely separate feature or device. In some embodiments, the laser system can be used for establishing the correct cutting angle during resection of the tibia and/or femur by providing beams which illuminate the epicondyles and/or a Whiteside&#39;s line to establish proper rotational orientation of a femoral implant. 
       FIGS.  35   a  and  35   b    illustrate how a laser system can be used to align the cutting block  84  with the sagittal plane which contains the mechanical axis. Once activated, the laser system in the surgical orientation device  12  can project a red laser light against the lower leg, with the laser light forming a line or lines along the exterior of the lower leg to provide visual cues as to alignment. For example, and as shown in  FIGS.  35   a  and  35   b   , the laser light (dashed line in the figures) can emanate down the leg and extended rod  332  from an optical element  32  on the surgical orientation device  12 , and can illuminate a landmark or landmarks, such as for example an anatomical landmark between the first and second toes on the patient&#39;s foot. Because only one pin or other anchoring device is inserted into the cutting block  84 , the extended rod  332 , surgical orientation device  12 , and cutting block  84  can swing about the inserted first pin in a varus/valgus plane until the laser light is pointing to the desired landmark on the foot.  FIGS.  35 A and  35 B  illustrate an example of this movement. 
     Once the laser light has hit the desired landmark, the user can press a user input  26  on the surgical orientation device  12 , and the surgical orientation device  12  can register the orientation of the sagittal plane. The surgical orientation device  12  can then provide a display of the varus/valgus angle as the varus/valgus angle changes relative to this recorded initial position. For example, the display  24  can indicate zero degrees when the cutting block is aligned with the sagittal plane, and can read other values when the cutting block is swung one way or the other relative to the initial position. This can allow the user to change the varus/valgus angle until the varus/valgus angle of the cutting block is at its pre-operatively determined value. 
     Once this desired value is obtained, the user can insert a second pin or pins, or other anchoring device or devices, through the cutting block  84  and into the tibia.  FIGS.  36 A and  36 B  illustrate a second mounting pin insertion. Once the second mounting pin  333  is inserted, the cutting block  84  can be fixed in place, or substantially fixed in place. 
     Once the cutting block is fixed, the rest of the extramedullary alignment guide  313 , as well as the surgical orientation device  12  and coupling device  14 , can be removed.  FIG.  37    illustrates the cutting block  84  fixed to the tibia, with a cutting tool beginning to resect the tibia by moving a saw blade through the opening  102 . 
     H. Tibial Preparation System with a Single Orthopedic Fixture 
     A tibial preparation system can be provided which uses a single orthopedic fixture, instead of two orthopedic fixtures as described above. For example,  FIGS.  4   a  and  4   b    show a tibial preparation system  410  for use in a joint replacement procedure, such as for example a knee replacement procedure. The tibial preparation system  410  can comprise the surgical orientation device  12  described above, the coupling device  14  described above, and a landmark acquisition assembly  412 . The tibial preparation system  410  can be different from the systems  10 ,  210 , and  310 , for example in that the system  410  can utilize a single structural alignment device with a surgical orientation device, the alignment device being used along the lateral side of the tibia (e.g. held alongside the leg), as well as along the anterior side of the tibia. 
     The landmark acquisition assembly  412  can be similar to the landmark acquisition assembly  312  described above. For example, the landmark acquisition assembly  412  can comprise a primary rod, connecting element or elements, and secondary rod or rods. 
     The landmark acquisition assembly  412  can further include a handle  414 . The handle  414  can attached to or integrally formed with a first portion  416  of the landmark acquisition assembly  414 . For example, the handle  414  can be attached to or integrally formed with a primary rod, or other extending structure, of the first portion  416  of the landmark acquisition assembly  412 . 
     The handle  414  can also be releasably coupled to a second portion  418  of the landmark acquisition assembly  412 . For example, one end of the handle  414  can be screwed onto, and/or latched onto, an end of the second portion  418 , such that the second portion  418  of the landmark acquisition assembly  412  can be removed from the first portion  416 . 
     The surgical orientation device  12  can be coupled to the landmark acquisition assembly  412 . For example, the surgical orientation device  12  can be coupled to the first portion  416  of the landmark acquisition assembly  412  with the coupling device  14 . As shown in  FIG.  4   b   , the surgical orientation device  12  can comprise a laser system or systems  42 . 
     A cutting block  84  can also be attached to or integrally formed with the first portion  416 , and can itself be attached to or integrally formed with a stylus  420  used for determining resection depth. 
     I. Acquiring Orientation Information Using a Single Orthopedic Fixture 
     After pre-operative planning for a joint replacement procedure, the tibial preparation system  410  described above can be used to identify the location and orientation of an axial line, as well as to orient a cutting block relative to the axial line. 
     For example, once the desired varus/valgus and posterior/anterior angles for resection have been determined pre-operatively for a knee replacement procedure, the tibial preparation system  410  can first be assembled as shown in  FIG.  4   a   . The surgical orientation device  12 , coupling mechanism  14 , and landmark acquisition assembly  412  can be coupled together, and the landmark acquisition assembly  412  can be positioned laterally alongside the tibia and outside of the leg. 
     Similar to the method described above with respect to the landmark acquisition assembly  312 , the secondary rods or structures on the landmark acquisition assembly  412  can be placed against predetermined anatomical landmarks alongside the leg, and the surgical orientation device  12  can register an orientation of the mechanical axis. Once the orientation of the mechanical axis has been registered, the landmark acquisition assembly can be positioned and/or aligned in front of the tibia, (i.e. anterior to the tibia) 
       FIGS.  38  and  39    show the landmark acquisition assembly  412  placed in front of the tibia T. The landmark acquisition assembly  412  can be moved and/or rotated in a first degree of rotation (e.g. roll) until the sensor or sensors  40  in the surgical orientation device  12  observe that the roll of the surgical orientation device  12  is aligned with gravitational zero. For example, one axis of a dual-axis accelerometer sensor  40  can be aligned with gravitational zero. Once the sensor or sensors  40  inside the surgical orientation device  12  observe that the surgical orientation device  12  is in this orientation, the surgical orientation device  12  can provide an indication to the user. For example, the surgical orientation device  12  can display zero degrees and a flashing green light on the display  24 , or a bubble as described above. Once the user has received this indication, the user can press a user input  26  (e.g. a middle button below display  24 ), confirming and/or registering the orientation of the surgical orientation device  12 . 
     The landmark acquisition assembly  412  can then be rotated and/or moved in a second degree of rotation (e.g. pitch) until the sensor or sensors  40  observe that the surgical orientation device  12  is in a plane parallel to the coronal plane containing the mechanical axis of the patient&#39;s leg. Once the sensor or sensors  40  inside the surgical orientation device  12  observe that the surgical orientation device  12  is in this orientation, the surgical orientation device  12  can again provide an indication to the user. For example, the surgical orientation device  12  can display zero degrees and a flashing green light on the display  24 , or a bubble as described above. Once the user has observed this light or other indication, the user can press a user input  26  (e.g. a middle button below display  24 ), confirming and/or registering the orientation of the surgical orientation device  12 . 
     As described above, in some embodiments the surgical orientation device can provide an indication when the surgical orientation device  12  is aligned in both degrees of freedom at the same time, rather than providing an indication each time separately. Similarly, in some embodiments the user can press the user input  26  once, rather than twice, to confirm registration of the orientation of the surgical orientation device  12 . 
     Once the cutting block  84  is aligned with the mechanical axis, the opening  102  which comprises an elongated slot for receiving a cutting saw can extend generally perpendicular to the mechanical axis extending through the tibia. If pins were inserted through the cutting block  84  into the proximal end of the tibia to anchor the cutting block  84 , and a cutting saw was inserted through this elongated slot  102 , the cutting saw would resect the top of the tibia and leave a flat tibial plateau perpendicular to the mechanical axis. 
     However, as with the other methods described above, the cutting block  84  can be adjusted in order to orient the cutting block into the pre-operatively determined varus/valgus and/or posterior/anterior angles for resection. For example, the first portion  416  and second portion  418  of the landmark acquisition assembly  412  can be separated, and the second portion  418  can be placed to the side. The first portion can then be moved and/or rotated by hand in a varus/valgus direction and/or posterior/anterior direction. 
       FIG.  39    shows the landmark acquisition assembly  412  being maneuvered by hand. For example, the handle  414  can be moved towards or away from the distal end of the tibia in a sagittal plane to move the first portion  416  and cutting block  84 . This movement can alter the angle of any pin placement in the cutting block  84 , and consequently, alter the posterior/anterior angle of the cutting block  84 . 
     Once the landmark acquisition assembly  412  and cutting block  84  are aligned as desired, a pin or other anchoring device can be inserted through a hole  102  of the cutting block  84  and into the tibia, for example as shown in  FIG.  39   . This first pin can anchor the cutting block in place, yet allow the cutting block  84  to swing in a varus-valgus direction about the first, fixed pin. 
     The handle  414  can then be used to swing the first portion  416  about the fixed pin, and to orient the cutting block in the varus/valgus plane. For example, a laser system, such as one described above, can be used while the cutting block  84  is pinned and swung by the handle  414 . A laser beam or beams can emanate form the surgical orientation device  12  out of the optical element or elements  32 . Similar to what is shown in  FIGS.  35   a  and  35   b   , the laser beam can identify a landmark, such as the area between the first and second toes on the patient&#39;s foot, in order to acquire an orientation of the sagittal plane containing the mechanical axis. 
     Once the orientation of the sagittal plane containing the mechanical axis has been acquired and registered in the surgical orientation device  12 , the handle  414  can be moved again to change the varus/valgus angle until the display  24  on the surgical orientation device  12  indicates that the varus/valgus angle of the cutting block is at its pre-operatively determined value. 
     Once the desired pre-operatively determined angles are obtained, a second pin or pins, or other anchoring device or devices, can be placed through the openings  102  in the cutting block  84 , and the cutting block  84  can be anchored firmly, such that there is substantially no freedom of motion. The handle  414  and rest of first portion  416  can then be removed completely, leaving only the cutting block  84  securely anchored to the tibia. A cutting tool (e.g. cutting saw) can then be moved through the elongate opening  102  on the cutting block  84  to resect a portion or portions of the proximal tibia. 
     III. Femoral Cut/Knee Distraction Systems and Methods 
     As discussed above, knee replacement procedures commonly involve a resection of the tibia along the proximal tibia. This resection of the tibia typically leaves a tibial plateau or plateaus along the proximal tibia, which can provide a location for placement and/or attachment of a prosthetic knee joint. 
     In addition to a tibial resection, or alternatively to a tibial resection, a knee replacement procedure can further comprise a resection of a portion or portions of the distal femur. Resecting a portion or portions of the distal femur can provide a location for placement and/or attachment of a femoral knee joint prosthetic. As with the tibial resection, the orientation of a cutting block, and/or cutting plane or planes, can be pre-operatively determined in order to provide a desired fit and/or orientation for the femoral knee joint prosthetic. Properly orientating the cutting plane or planes along the distal femur can facilitate alignment of the femoral knee joint prosthetic with the tibial knee joint prosthetic. This alignment can create a set of knee joint prosthetics which function smoothly, continuously, and/or without substantial wear during their life of use. 
     Along with attaining and/or facilitating proper alignment between the femoral knee joint prosthetic and the tibial knee joint prosthetic, the user can additionally prepare the knee joint such that the ligaments and/or soft tissue surrounding the knee joint is substantially balanced after attachment of the knee joint prosthetics. A balanced joint refers generally to a joint in which one side of the knee is not substantially straining, pulling, and/or constraining the other side of the knee. For example, in an unbalanced knee joint, the ligaments and soft tissue on the lateral side of the knee may be experiencing tension at a substantially higher degree as compared to the ligaments and soft tissue on the medial side of the knee. During a knee joint replacement procedure, it can be advantageous to balance the tension on either side of the knee, so as to prevent undesired strain or stress within the knee joint. This balancing can be achieved, for example, by use of a knee distraction device or instrument which distracts the distal femur from the proximal tibia in a manner that achieves substantial balancing of the knee joint prior to attachment of the knee joint prosthetics. 
     Systems and methods of preparing a femoral cut, and/or distracting the knee are described further herein. While the systems and methods are described in the context of a knee joint replacement procedure, the systems and/or their components and methods can similarly be used in other types of medical procedures, including but not limited to shoulder and hip replacement procedures. 
     A. Femoral Preparation System with a Moveable Orthopedic Fixture 
       FIG.  5    shows a femoral preparation system  510  for use in a joint replacement procedure, such as a knee joint replacement procedure. The femoral preparation system  510  can be used to resect a portion of a femur, and can comprise the surgical orientation device  12  described above, the coupling device  14  described above, and an orthopedic fixture, such as a universal jig  512 . 
     1. Orthopedic Fixture for Orienting a Surgical Orientation Device in Multiple Degrees of Freedom 
     An orthopedic fixture can be provided which can have a moveable portion or portions which are used to orient a surgical orientation device. The surgical orientation device can be oriented in multiple degrees of freedom. For example,  FIGS.  40  and  41    illustrate the universal jig  512 . The universal jig  512  can be similar to the universal jigs described above. For example, the universal jig  512  can comprise a base portion  514 , a posterior/anterior adjustment block  516 , and a varus/valgus adjustment block  518 . 
     The universal jig  512  can facilitate movement of a cutting block in at least two degrees of freedom. For example, the universal jig  512  can be configured to enable the surgeon to move a cutting block in a direction that changes the angle of the cut on the femur such that the cutting angle slopes either from the posterior to the anterior side of the knee or from the anterior to the posterior side (flexion-extension), providing one degree of freedom. The cutting block  512  can additionally or alternatively be configured so that a cutting block can be moved such that the cutting angle slopes in a varus-valgus manner, thereby providing a second degree of freedom. 
     In some embodiments, it can be desirable to provide multiple degrees of freedom in a translation direction. For example, the universal jig  512  can be configured to enable a cutting block to be moved in a proximal (toward the hip joint) or distal (toward the foot) direction, providing a first degree of freedom in translation. The universal jig  512  can further be configured such that a cutting block can be moved posteriorly toward the surface of the knee joint or anteriorly away from the surface of the knee joint to create more space between the block and the joint. In one technique it can be desirable to have the ability to move a cutting block posteriorly into contact with the anterior surface of the femur. 
     a. Base Member for Providing an Anchored or Fixed Initial Position of an Orthopedic Fixture, and Slide Member for Allowing Translational Movement 
     A base member can be provided which can anchor or fix an initial position of an orthopedic fixture. A slide member can also be provided for allowing translation movement of a portion or portions of the orthopedic fixture. For example, and with continued reference to  FIGS.  40  and  41   , the base member  514  can be attached to a distal portion of the femur. For example, a pin, screw, or other anchoring device can be inserted through a hole or holes  520  located along the base member  514 . The holes  520  can take any suitable configuration and orientation. For example, the holes  520  can be angled at 45° with respect to the posterior surface of the base member  514 . Once the anchoring devices are inserted through the base member  514  and into the distal femur, the base member  514  can be held stable relative to the femur, while other portions of the universal jig  512  can move relative to the base member  514 . 
     The base member  514  can comprise a slot or slots  522  extending along a portion or portions of the base member  514 . The slots  522  can be configured to receive corresponding, or mating, flanges formed on a slide member  524 . For example, the slots  522  can be configured to receive flanges  526  along slide member  524 , as shown in  FIG.  41   . The slots  522  and flanges  526  can be configured such that slide member  524  can slide and/or translate both distally and proximally relative to the base member  514  and femur. 
     The slide member  524  can further comprise receiving holes  528 . The receiving holes  528  can be sized and/or shaped so as to receive a pivot pin on the posterior/anterior adjustment block  516 . 
     b. Device for Adjusting a Posterior/Anterior Slope of a Cutting Block 
     A posterior/anterior adjustment device can be provided which can be used to adjust the orientation of a surgical orientation device and/or cutting block adjacent the femur. For example, the posterior/anterior adjustment block  516  can comprise a pivot pin  530 . As described above, the pivot pin  530  can be received by the receiving holes  528  on the slide member  524 . The pivot pin  530  can facilitate pivoting motion and/or rotation of the posterior/anterior adjustment block  516  relative to the slide member  524  and/or base member  514  in a posterior/anterior direction. In a preferred arrangement, the pivot pin  530  can facilitate pivoting of the posterior/anterior adjustment block  516  within a range of approximately twenty degrees (e.g. +− ten degrees on either side of a predetermined angle). Other ranges are also possible. 
     The posterior/anterior adjustment block  516  can further comprise a receiving hole or holes  532 . The receiving holes  532  can be sized and/or shaped so as to receive a pivot pin. The pivot pin can extend through the receiving holes  532  as well as through a receiving hole or holes on the varus/valgus adjustment block  518 . 
     c. Device for Adjusting a Varus/Valgus Slope of a Cutting Block 
     A varus/valgus adjustment device can be provided which can be used to adjust the orientation of a surgical orientation device and/or cutting block adjacent the femur. For example, the varus/valgus adjustment block  518  can comprise an elongate rod  534 . The elongate rod  534  can extend distally from the base member  514  when the universal jig  512  is attached to the distal femur. In a preferred arrangement of the universal jig  512 , the elongate rod  534  can be coupled to the coupling device  14 , and the coupling device  14  can be couple to the surgical orientation device  12 . 
     With continued reference to  FIG.  41   , the varus/valgus adjustment block  518  can further comprise a receiving hole  536 . As described above, the receiving hole  536  can receive a pin which extends through the receiving holes  532 . The pin extending through the receiving holes  532  and  536  can facilitate pivoting motion and/or rotation of the varus/valgus adjustment block  518  relative to the base member  514  in a varus/valgus direction. In a preferred arrangement, the pivot pin  530  can facilitate pivoting of the posterior/anterior adjustment block  516  within a range of approximately twenty degrees (e.g. +− ten degrees on either side of a predetermined angle). Other ranges are also possible. 
     The varus/valgus adjustment block  518  can further comprise a flange or flanges  538 . The flanges  538  can be configured to be received by corresponding, or mating, slots in a cutting block or other structure. 
     d. Cutting Block which can be Oriented for Bone Resection 
     A cutting block, or other orthopedic fixture, can be provided for bone resection. The cutting block can be oriented with the aid of a surgical orientation device and an orthopedic fixture or fixtures.  FIGS.  40  and  41    illustrate a cutting block  540 . The cutting block  540  can be similar to the cutting block  84  described above. For example, the cutting block  540  can comprise at least one opening  102 . One opening  102  can comprise, for example, an elongate slot configured to receive a cutting tool, such as for example a cutting saw. 
     The cutting block  540  can further comprise a slot or slots  542 . The slots  542  can be configured to receive the flanges  538  on the varus/valgus adjustment block  518 . The combination of the slots  542  and flanges  538  can facilitate movement (e.g. translational movement) of the cutting block relative to the varus/valgus adjustment block  518 . For example, in a preferred arrangement the cutting block  540  can translate in a posterior/anterior direction (i.e. towards or away from the femur). 
     B. Acquiring Information Using a Femoral Preparation System 
       FIGS.  42  and  43    show a method of using the femoral preparation system  510 . In a preferred arrangement, the base member  514  is first pinned to a distal aspect of the femur F, which has been exposed in any conventional surgical manner. The orientation device  12  can then be coupled with the elongate rod  534 , for example by using the clamping device  14 . Thereafter, the femoral preparation system  10 , including the surgical orientation device  12 , as well as the entire lower leg, can be moved, swung, and/or pivoted about a proximal head of the femur until the location and/or orientation of the mechanical axis of the leg is found. 
     For example, the center of rotation of the head of the femur, and/or the mechanical axis of the patient&#39;s leg, can be detected by moving and/or swinging the leg and attached surgical orientation device  12  on a horizontal plane (e.g. a plane along the operating table), starting from a known fixed position and orientation (referred to as the origin, which can be close to the surface of the horizontal plane) and obtaining inertial readings such as angular displacement and acceleration (referred to as IMU data). The arrows in  FIG.  43    illustrate at least one example of how the direction or directions the leg can be moved. 
     The surgical orientation device  12 , which can be coupled to the leg during such movement, can comprise at least one single- or multi-axis gyroscope sensor  40  and/or at least one single- or multi-axis accelerometer sensor  40 . The accelerometer(s) can have axes angled with respect to an axis of the surgical orientation device  12 . As the leg is swung, the sensors  42  can detect movement of the surgical orientation device  12 , and collect the IMU data. 
     From this IMU data, the surgical orientation device  12  can calculate the location of the center of rotation of the femur, as well as the location of the mechanical axis running through the leg. 
     Once the surgical orientation device  12  has made the above-described calculation or calculations, the surgical orientation device  12  can be rotated and/or moved by the universal jig  512  to align the surgical orientation device  12  with the mechanical axis of the leg. When the surgical orientation device  12  is aligned with the mechanical axis of the leg, the surgical orientation device  12  can provide a signal, such as for example a flashing green light on its display  24 . 
     The user can then use the universal jig  512  to move and/or change the position of the surgical orientation device  12  and cutting block  540 , in order to achieve a pre-operatively determined resection angle or angles for resection of the femur. As with the tibial cut methods described above, the varus/valgus and posterior/anterior angles for resection can be adjusted by moving the varus/valgus adjustment block  518  and/or posterior/anterior adjustment block  516 . Other adjustments, movements, translations, rotations, and/or changes in position of the cutting block  540  can also be made. 
     The surgical orientation device  12  can provide an indication of degrees of movement. For example, the surgical orientation device  12  can inform the user how many degrees (e.g. in half degree increments) the surgical orientation device and cutting block  540  are rotated past the mechanical axis in one or more planes. The surgical orientation device can display this information in its display  24 , and/or provide audio indications to the user as well. 
     The cutting block  514  can then be brought into contact with the distal femur. The cutting block  540  can be immobilized, for example, by advancing pins through one or more openings  102 . The user can then disconnect the surgical orientation device  12  from the universal jig  512 , e.g. by releasing the clamping device  14 . Additionally, or alternatively, the user can disconnect a portion or portions of the universal jig  512  from the cutting block  540 , thereby leaving the cutting block  540  behind on the distal femur. Thereafter, the cutting block  540  can be used to resect the distal femur. For example, a cutting tool or tools can be moved through an elongate opening or openings  102 , so as to prepare the distal femur for receiving a knee joint prosthetic. 
     C. Alternative Method of Using Femoral Preparation System 
     In other embodiments, the center of rotation and the mechanical axis can be detected by moving the leg about the junction of the femoral head and an acetabulum in several different planes, as opposed to one plane, and obtaining IMU inputs of the femur for various locations of the distal end of the femur approximating a portion of a spherical surface, with the center of the sphere being the femoral head center. For example, in one embodiment of the surgical orientation device  12  incorporating one or more multi-axis accelerometers and gyroscopes, IMU data for each movement of the femur can be numerically integrated over time to obtain a trajectory of position and velocity points (one point for each IMU input) without imposing any plane trajectory constraints on movements of the femur. The location of the sphere center (e.g., the femoral head center) can be calculated using, for example, a non-linear least-squares fit algorithm. Examples of three possible leg movement trajectories for calculating IMU data are: (i) a horizontal swing from the leg&#39;s position of origin to the surgeon&#39;s right and then back again; (ii) a horizontal swing from the origin to the surgeon&#39;s left and then back again; and (iii) a vertical swing upward and then back again. During each swing trajectory the IMU data can be stored for future processing. 
     Accuracy in determining the femoral head center can be improved if both positive and negative time integrations are performed for each movement of the femur from an origin at t=T 0  to a given position at t=T 1  and then back again to the origin at t=T 2 . The negative integrations (which correspond to integration from T 2  to T 0  in one technique) can be used to reduce the integration errors which may arise, for example, because of imperfect calibration or drift. For example, following each inertial measurement for a given location of the distal femur, the leg can be returned to its origin, with input provided to the surgical orientation device  12  that the surgical orientation device  12  has been returned to the origin. In one embodiment, the surgical orientation device  12  can be configured to assume or recognize that it has been returned to the origin. The surgical orientation device  12  can include a microcontroller in its electronic control unit  1102 , for example, that can be configured to perform forward and backward integration over the maneuver and compare the results. This can be done as a way to calibrate the sensors  40 . 
     When taking inertial readings, the surgical orientation device  12  can assume that roll motion of the femur (with respect to a femur line) is zero. In one method, the user can restrict the femur roll motion as much as possible and endeavor to move the femur in pitch and yaw motions (with respect to the femur line) when taking readings. 
     In one embodiment, the surgical orientation device  12  can be placed at the origin with no motion for a pre-determined time period to signal positioning at the origin, e.g., at least one second in between swing trajectories. This can facilitate the surgical orientation device&#39;s recognition of the start and end of a swing trajectory. In such an embodiment, a numerical value for magnitude of the acceleration of gravity or the location of the device in an Earth Centered Rotating (ECR) coordinate system can be an input to the processing inside the electronic control unit  1102 . 
     In one embodiment of the device, there can be a parameterized function mapping of the IMU readings to the assumed or estimated acceleration and angular orientation in a frame attached to the device. This set of trajectory points (i.e. free trajectory points) along with the set IMU readings can be referred to as spherical independent values. There can be four individual dynamic sets of independent values, which are: position, velocity, IMU gyro values, and IMU accelerometer values. During the processing, a corresponding set of spherical dependent values can be generated, assuming the motion of the surgical orientation device  12  is constrained to the surface of the sphere and there is no roll motion about the line connecting the center of the sphere and the surgical orientation device  12 . This set of values can be a function of the center of the sphere (the value for the radius of the sphere can be known since the origin is assumed to lie on the surface of the sphere) and, if needed, a set of IMU calibration parameters. The assumption can be made that at each IMU cycle time the surgical orientation device  12  is at a point of intersection of the sphere and the line connecting the corresponding independent position point and the center of the sphere. 
     The algorithm employed by the surgical orientation device  12  to determine the femoral head center can utilize a mathematical principle that determines the values for the unknown parameters (femoral head center and IMU calibration parameters) that minimize a cost function consisting of the sum of the squares of the difference between the spherical independent values and the spherical dependent values. The spherical independent IMU values can be provided by the sensor or sensors  40 , and the spherical dependent IMU values can be calculated. 
     The following are two Cartesian coordinate frames that may be used to describe an algorithm:
         1. The inertial Trajectory frame or T-frame. The coordinate frame for integrating the IMU input values. The origin is at the center of device at the start and end of each trajectory and the unit vectors are
           Z-axes (Z T ) points upward   X-axes (X T ) points in patients foot to head in the horizontal plane   Y-axes (Y T ) points to the surgeons left in the horizontal plane (Y T =Z T ×X T ).   
           2. The moving and rotating Device frame or D-frame. The IMU system can be attached to this frame and its origin can be located at the center of the IMU device. At the start/end of each frame it should be aligned with the T-frame.
           X-axes (X D )=(X T )   Y-axes (Y D )=(Y T )   Z-axes (Z D )=(Z T )
 
The following symbols can be used to describe the processing that generates the spherical independent trajectory points for the nth swing trajectory according to one technique that can be incorporated into an embodiment of an orientation device described herein.
 
Δ—IMU cycle time interval
 
t n   0 —Starting time of the trajectory
 
t n   I —Ending time of the Ith IMU cycle (I*Δ).
 
N n   I —Total number of trajectory IMU time intervals.
 
t n   E —Trajectory ending time (N n   I *Δ)
 
w n (t)—IMU angular velocity input value for time t
 
w n   I —IMU angular velocity input value for cycle I (w n (t)=w n   I  for (I−1)*Δ≤t≤I*Δ)
 
a n (t)—IMU acceleration input value for the nth swing at time t.
 
a n   I —IMU angular velocity input value for cycle I (a n (t)=a n   I  for (I−1)*Δ≤t≤I*Δ)
 
W D (x w ,w(t))—The function that maps the IMU angular velocity value to the assumed/estimated angular velocity in the D-frame.
 
x w —Gyro calibration parameters that can be estimated such as biases and scale factors.
 
N w —Number of Gyro calibration parameters (can be zero)
 
Φ D   T (t): Direction Cosine matrix—maps a vector in the D-frame to a vector in the T-fame. It can be calculated using both forward and backward time integration
   
               

     
       
         
           
             
               
                 
                     
                     
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     A D  (x A ,a(t))—The function that maps the IMU accelerometer value to the assumed/estimated acceleration in the D-frame.
 
x A : Accelerometer calibration parameters that may need to be estimated such as biases and scale factors.
 
N A —Number of Accelerometer calibration parameters (can be zero).
 
 + R n   I (x A ,x W )-Ith positive trajectory position point
 
 − R n   I (x A ,x W )-Ith negative trajectory position point
 
 + V n   I (x A ,x W )-Ith positive trajectory velocity point
 
 − V n   I (x A ,x W )-Ith negative trajectory velocity point
 
         +   R   n   I ( x   A   ,x   W )=∫ 0   t     I   ∫ 0   t   A   T ( x   w   ,x   A   ,w   n ( s ), a   n ( s )) dsdt  
 
         −   R   n   I ( x   A   ,x   W )=∫ Tn   t     I   ∫ Tn   t   A   T ( x   w   ,x   A   ,w ( s ), a ( s )) dsdt  
 
         +   V   n   I ( x   A   ,x   W )=∫ 0   t     I     A   T ( x   w   ,x   A   ,w   n ( s ), a   n ( s )) ds  
 
         −   V   n   I ( x   A   ,x   W )=∫ Tn   t     I     A   T ( x   w   ,x   A   ,w   n ( s ), a   n ( s )) ds  
 
         A   T ( x   w   ,x   A   ,w   n ( s ), a   n ( s ))=Φ D   T ( x   w   ,s )· A   D ( x   A   ,a   n ( s ))
 
     R n   I (x A ,x W ) Ith trajectory position point. 
         R   n   I ( x   A   ,x   W )=β + *( +   R   n   I ( x   A   ,x   W ))+(1−β + )*( −   R   n   I ( x   A   ,x   W ))
 
       β + =( t   n   E   −t   n   I )/ t   n   E  
 
     Error in double integration due to white is proportional to the time of integration.
 
V n   I (x A ,x W )—The Ith trajectory velocity point
 
         V   n   I ( x   A   ,x   W )=β + *( +   V   n   I ( x   A   ,x   W ))+(1−β + )*( −   V   n   I ( x   A   ,x   W ))
 
       β + =(( t   n   E   −t   n   I )/ t   n   E ) 1/2  
 
     Error in single integration due to white is proportional to the square-root of time of integration.
 
The following describes a processing for the spherical dependent trajectory parameters. Most of the calculation can be performed in the Inertial Trajectory Frame. This processing assumes the points are constrained to the surface of a sphere. The center of the sphere is denoted by {right arrow over (R)}c or the three component vector (x c ,y c ,z c ). Since the origin is assumed to be on the sphere the radius of the sphere is
 
         Rc =( x   c   2   +y   c   2   +z   c   2 ) 1/2    
     The following symbol and expression are use to describe how the Ith spherical dependent trajectory parameter values can be calculated in terms of the (I−1)th values for the nth swing trajectory.
 
 S R n   I -Ith Position Point
 
         S   R   n   I =unit( R   n   I )* Rc    
       S θ n   I -Ith Rotation Vector 
         S θ n   I =unit( S   R   n   I-1 × S   R   n   I )*arc cos(unit( S   R   n   I-1 )·unit( S   R   n   I ))
 
       S Ω n   I -Ith Angular Velocity Vector 
         S Ω n   I = S θ n   I /Δ
 
       S A n   I -Ith Velocity Point 
         S   V   n   I = S Ω n   I × S   R   n   I  
 
       S A n   I -Ith Acceleration Vector 
         S   A   n   I =( S   V   n   I − S   V   n   I-1 )/Δ
 
       S Φ n   I -Ith Spherical Trajectory direction cosine matrix; transforms a vector in the Device frame to a vector in the Trajectory frame. 
     
       
         
           
             
               
                 
                   
                     
                         
                         
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     The operator “⊗” produces the direction cosine matrix that results from rotating the direction cosine matrix to the right of the operator about the angle to the left of the operator.
 
 D   S Ω n   I -Ith Angular Velocity Vector for the Nth Swing Trajectory Expressed in the Device Frame
 
         D   S Ω n   I =½*( S Φ n   I-1 + S Φ n   I ) T · S Ω n   I  
 
       D   S A n   I -Ith Acceleration Vector Expressed in the Device Frame 
         D   S   A   n   I =½*( S Φ n   I-1 + S Φ n   I ) T · S   A   n   I  
 
       S w n   I : Ith Calculated Gyro Value (the Application of the Inverse Mapping of the Gyro Calibration Function) 
         S   w   n   I   =W   D   −1 ( x   w , D   S Ω n   I )
 
       S a n   I : Ith Calculated Gyro Value (the Application of the Inverse Mapping of the Accelerometer Calibration Function) 
         S   a   n   I   =A   D   −1 ( x   a , D   S   A   n   I ) 
     The following contains a definition of the four trajectory parameter cost functions and the total cost function. The total cost function represents a weighted average of the four trajectory parameter cost functions.
 
γ R (x c ,y c ,z c ,x A ,x W )—Position Cost Function
 
     
       
         
           
             
               
                 
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     γ V (x c ,y c ,z c ,x A ,x W )—Velocity Cost Function 
     
       
         
           
             
               
                 
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     γ G (x c ,y c ,z c ,x A ,x W )—Gyro Cost Function 
     
       
         
           
             
               
                 
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     γ A (x c ,y c ,z c ,x A ,x W )—Accelerometer Cost Function 
     
       
         
           
             
               
                 
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     γ(x c ,y c ,z c ,x A ,x W )—Total Cost Function 
       γ( x   c   ,y   c   ,z   c   ,x   A   ,x   W )=α R *γ R ( x   c   ,y   c   ,z   c   ,x   A   ,x   W )+α V *γ V ( x   c   ,y   c   ,z   c   ,x   A   ,x   W )±α G *γ G ( x   c   ,y   c   ,z   c   ,x   A   ,x   W )+α A *γ A ( x   c   ,y   c   ,z   c   ,x   A   ,x   W )
 
     The mathematical goal of the algorithm can be to solve the following 3+Na+Nw equations for (x c ,y c ,z c ,x A ,x W ) that minimize the Total Cost Function. 
       ∂γ( x   c   ,y   c   ,z   c   ,x   A   ,x   W )/∂ x   c =0
 
       ∂γ( x   c   ,y   c   ,z   c   ,x   A   ,x   W )/∂ y   c =0
 
       ∂γ( x   c   ,y   c   ,z   c   ,x   A   ,x   W )/∂ z   c =0
 
       ∇ x   A (γ( x   c   ,y   c   ,z   c   ,x   A   ,x   W ))=0, ∇ x   A  the gradient  wrt  accelerometer calibration parameters
 
       ∇ x   W (γ( x   c   ,y   c   ,z   c   ,x   A   ,x   W ))=0, ∇ x   W  the gradient  wrt  gyro calibration parameters
 
     D. Femoral Preparation System with Knee Distraction Device for Resecting the Femur and/or Distracting the Knee Joint 
     A femoral preparation system can be provided which can both align a cutting block for resecting a bone, as well as distract a joint so as to balance the tissue surrounding the joint. For example,  FIG.  6    shows a femoral preparation system  610  for use in a joint replacement procedure, such as for example a knee joint replacement procedure. The femoral preparation system  610  can comprise the surgical orientation device  12  described above, the coupling device  14  described above, and a distraction instrument, such as for example a knee distraction device  612 . As described further herein, the femoral preparation system  610  can be used for both alignment and distraction. 
       FIG.  44    shows a knee distraction device  612 . The knee distraction device  612  can be configured to distract the knee joint during a knee replacement procedure and balance the soft tissue and/or ligaments within the knee joint. The knee distraction device  612  can additionally or alternatively be configured to facilitate attachment of a cutting block to the distal femur for resection of the distal femur. 
     With continued reference to  FIG.  44   , the knee distraction device  612  can comprise a distractor body, such as for example a body  614 . The body  614  can comprise an inner body portion  616 , an outer body portion  618 , and at least one adjustment device  620 . The knee distraction device  612  can further comprise a reference feature, such as for example a tibial baseplate  624 , and at least one distraction element  626 . The knee distraction device can further comprise guide portion  628 . The body  614 , tibial baseplate  624 , and distraction element or elements  626  can form an anterior portion of the knee distraction device  612 . 
     In some embodiments the distraction elements  626  can comprise femur contacting components. For example, the distraction elements  626  can include generally flat, thin, foot portions  630  which extend away from the body  614 , and can be configured to engage the bottom of a bony landmark, such as for example a femoral condyle. The distraction elements  626  can further include posts  632  which can be movable relative to the tibial baseplate  624 , and can extend into a portion or portions of the outer body portion  618 . 
     The posts  632  can be controlled by the adjustment devices  620  on either side of the body  614 . The adjustment device or devices  620  can comprise knobs, and the distraction elements  626  can resemble feet, with legs which extend from a lower, or distal, portion of the body  614 . 
     The tibial baseplate  624  can comprise a planar member coupled to the distractor body, and can sit underneath the distraction elements  626 . The tibial baseplate can be configured to be positioned on a tibial plateau. The tibial baseplate  624  can extend at an angle perpendicular to a front face of the body  614 . The distraction elements  626  can be coupled with the distractor body, and can be configured to be moved relative to the tibial baseplate  624  to increase or decrease a gap therebetween. The distraction elements  626  can also extend at an angle perpendicular to the front face of the body  614 , and can individually be moved away from the tibial baseplate  624  (e.g. in a proximal direction), or towards the tibial baseplate  624  (e.g. in distal direction), by turning the adjustment devices  620 . 
       FIG.  45    shows a side view of the knee distraction device  612 . As shown in  FIG.  45   , the knee distraction device  612  can comprise a sizing stylus  622 . The stylus  622  can form a posterior portion of the knee distraction device  12 , and can be a modular device that can be changed to approximate a desired femoral implant size and/or to accommodate anatomical differences between the left and right knee joints. The stylus  622  can reference a particular femoral implant size and a corresponding measurement along an anterior aspect of the femur. The stylus  622  can generally comprise an anterior/posterior (A/P) sizing guide, and in some embodiments can include a marking or markings  634  along an attached post. The marking or markings  634  can provide an indication of how far the stylus  622  has been raised or lowered relative to, for example, the distraction element  626 . The stylus  622  can be attached to, and/or move with, the inner body portion  616 . The stylus  622  can be used, for example, to help measure the needed size of a knee joint prosthetic during a knee joint replacement procedure. 
     The body  614  of the knee distraction device  612  can further comprise a securing device  636 . The securing device  636  can comprise, for example, a knob which can be turned to lock the guide portion  628  in place. When unlocked, the guide portion  628  can slide within an opening of the outer body portion  618 . 
     In some embodiments, the guide portion  628  can protrude at least 75 mm beyond the tibial baseplate  624 . In some embodiments, the guide portion  132  can be 12.7 mm in diameter. Other diameters are also possible. In some embodiments, a cross section of the guide portion  628  can comprise a generally round portion and a generally flat portion similar to the primary rod  316  of the landmark acquisition assembly  312  described above. A portion of the guide portion  628  can be used, for example, as a handle. The guide portion  628  can be used to couple the knee distraction device  612  to the surgical orientation device  12 . For example, the coupling device  14  can be attached to the guide portion  628 , and the surgical orientation device  12  can be attached to the coupling device  14 . 
       FIGS.  44 ,  45 , and  46    illustrate how the inner body portion  616 , outer body portion  618 , and posts  632  can function together.  FIG.  44    shows a channel  638  extending down the outer body portion  618  on either side of the outer body portion  618 . The posts  632 , which are shown extending from beneath the outer body portion  618  in  FIG.  44   , can extend up into these channels  638 . 
       FIG.  45    shows a top view of the knee distraction device  612 , looking down the channels  638 . As illustrated, the tops of posts  632  can be seen inside the channels  638 .  FIG.  45    also shows extrusions  640 . The extrusions  640  can form part of the inner body portion  616 , and can extend partially or entirely into the channels  638 . 
       FIG.  47    shows the knee distraction device  612  with the outer body portion  618  removed. The extrusion  640 , which extends from inner body portion  616 , can rest on top of the post  632 , such that as the post  632  is moved inside the channel  638 , the inner body portion  616  is moved as well. In some embodiments, the adjustment device  620  and post  632  can comprise a rack and pinion-like gear system, wherein the post  632  comprises a plurality of gear teeth, and the adjustment device  620  comprises a plurality of corresponding gear teeth. When the adjustment device  620  is turned, the post  632  can be moved either up or down (e.g. proximally or distally) within the channel  638 . As the post  632  moves, the post  632  can carry the inner body portion  640 , and stylus  636 , with it. In some embodiments, only one extrusion  640  can be used to dictate and/or facilitate movement of the inner body portion  616 . 
     With continued reference to  FIG.  47   , the inner body portion  616  can comprise a modular structure or device, such as for example a sizing guide, which can be used for a specifically-sized implant or implants, and/or for a right leg or left leg only. In some embodiments, the inner body portion  616  can be removable from the knee distraction device  612 . The inner body portion  616  can be used to measure femoral implant size, and can contain holes through which pins can be placed into the femur (or other bony structure) for mounting another surgical apparatus or apparatuses. 
     In a preferred arrangement of the knee distraction device  612 , movement of the post or posts  632  can be tracked or monitored. For example, the knee distraction device  612  can provide audible and/or visual feedback to the user, indicating the degree or extent to which a post  632  and distraction element  626  have been moved relative to an initial starting position.  FIG.  48    shows a pin  642  and spring  644  which can be inserted into the outer body portion  618 . The spring  644  can bias the pin  642  against gear teeth along the post  632 , such that as the post  632  moves up and/or down, a user can hear and/or feel an edge of the pin  642  contacting the gear teeth along the post  632 . This contact can produce an audible click, or clicks. This contact can additionally or alternatively provide a force (e.g. frictional) which can hold the post  632  in a desired position, until the adjustment device  620  is turned again. 
     With continued reference to  FIGS.  44 - 48   , the distraction elements  626 , including the foot portions  630 , can be moved up and down (e.g. proximally and distally) relative to the tibial baseplate  624  by the adjustment device or devices  626 . For example, the distraction elements  626  can be moved individually and independently in a vertically upwards (e.g. proximal) direction to apply pressure to the distal condyles of a femur or other bony structure in the body, and move the condyles of the femur to a desired position. This movement can distract the knee joint, surrounding soft tissue, and/or ligaments. In some embodiments, a pressure or force gauge or gauges can be incorporated with the knee distraction device  612  to determine the amount of compressive force which was applied by, or is being applied by, the distraction elements  626  against the condyles of the femur. 
     The knee distraction device  612  can include an indicator which indicates the distance the inner body portion  616  has traveled relative to the tibial baseplate  624  after the adjustment device or devices  20  has been turned. For example, the indicator can be in the form of markings and/or other structures or components which provide a visual or audio indication. 
     The knee distraction device  612  can further comprise a spring or springs which can apply a constant spring force to whatever anatomical structure or structures the distraction elements  626  are contacting. For example, each distraction element  626  can include a pre-tensioned spring, such that when the knee distraction device  612  is placed into an anatomical joint (e.g. a knee joint), the pre-tensioned springs can be released, and a constant, pre-determined pressure can be applied by the distraction elements  626  to any contacted anatomical structures (e.g. condyles). In some embodiments, the pressure applied can be approximately 70-80 psi. In other embodiments the pressure applied by can be approximately 60-90 psi. Other pressures and/or pressure ranges are also possible. The pressures applied by each spring can be different. 
     In some embodiments, when the knee distraction device  612  is being used to distract the knee joint, a ligament or ligaments can be released on either or both sides of the knee. The knee distraction device  100  can be used to modify the ligament(s) of the knee to provide a desired balance of forces around the knee joint. 
     In a preferred arrangement, the foot portions  630  can be removably attached to the posts  632 . The foot portions  630  can be adjustable relative to the body  614  and/or posts  632 . For example, the foot portions  630  can be longitudinally slotted, such that the foot portions  630  can be adjusted in a longitudinal direction in a plane containing the tibial baseplate  624 . This adjustment can allow the foot portions  630  to be inserted into a knee joint, or other joint, at different depths, for example based on the knee joint size. By making the foot portions  630  slotted and/or adjustable relative to the posts  632 , the foot portions  630  can be inserted to a particular desired depth during each step of a procedure. Furthermore, the adjustability of the foot portions  630  can enable a single pair of foot portions  630  to be used throughout a joint procedure. In other contexts, a plurality of depths can be achieved by providing a set of foot portions  630  of different lengths that can be coupled with the posts  632 . 
     In a preferred arrangement, the foot portions  630  can additionally be rotatably adjustable. For example, the foot portions  636  can rotate in one ore more directions about the posts  632 . This rotation can facilitate use of the knee distraction device  612  in knee joints which vary in size, and where for example the femoral condyles in a particular knee joint are spaced significantly far apart. This rotation can also allow the foot portions  630  to be inserted through a relatively narrow incision in the body and then spread out once inside the knee joint (e.g. rotate away from one another) to engage the femoral condyles. This rotation can inhibit the use of larger, more undesirable incisions on a patient&#39;s body, thereby leaving the patient with a smaller, less visible scar after a joint replacement procedure. 
       FIG.  47    illustrates an opening or openings  646 . The openings  646  can be located on the inner body portion  616 , and can extend through the entire inner body portion  616 . While eight such openings  646  are shown in  FIG.  47   , different numbers, sizes, shapes, and/or locations of openings  646  can also be used. 
     The openings  646  can be used as drill hole and/or pin insertion guides. For example, when the knee distraction device  612  has distracted a distal femoral condyle or condyles in a knee replacement procedure, a pin or pins can be inserted into the distal femur in order to provide a mounting location for a cutting block. The openings  646  can be used as guides for insertion of these pins. The openings  646  can be spaced apart from one another in a pattern or patterns. For example, some of the openings  646  along the bottom of the inner body portion  616  can be spaced slightly higher, and/or further away from the tibial baseplate  624  than other openings  646  along the bottom of the inner body portion  616 . Similarly, some of the openings  646  along the top of the inner body portion  616  can be spaced slightly higher, and/or further away from the tibial baseplate  624  than other openings along the top of the inner body portion  616 . This spacing can be used, for example, to eventually control the orientation of a cutting block which is later attached to the pins. 
     The knee distraction device  612  described above can be biocompatible for short term exposure to the inner anatomy of the knee or other body joint, and can be sterilized by autoclave and/or gas. The weight of the knee distraction device  612  can vary. For example, in a preferred arrangement, the knee distraction device  612  can have a maximum weight of 1 kg, and can generally be lightweight for ease of operation and handling. Other maximum weights, including weights greater than 1 kg, are also possible. 
     The knee distraction device  612  can operate without lubricants. Materials can be selected and treated to prevent galling and provide smooth operation consistent with expectations for a high quality surgical instrument. In general, the knee distraction device  612  described above can be made robust to withstand normal and abusive use, especially rough handling during cleaning and/or sterilization. The knee distraction device  612  can be etched with part numbers, revisions levels, and company name and logo. Other markings can be added to provide clarity. 
     The knee distraction device  612 , or other similar distraction devices, can be used in joints other than the knee joint. For example, the knee distraction device  612  can be used in the elbow, or other joint, to distract a joint. 
     E. Acquiring Orientation Information and Distracting a Joint Using a Femoral Preparation System 
     During a knee joint replacement procedure, the knee distraction device  612  and femoral preparation system  610  described above can be used to align and balance the ligamentous structure of the knee joint and/or determine an orientation for a cut or cuts along the femur. In some techniques, one cut is referred to as the distal femoral cut (DFC). The DFC removes a distal (i.e., lower) portion of the femur. 
     Prior to using the femoral preparation system  610 , and prior to the DFC, the proximal (i.e. upper) tibia can be cut. For example, and as described above, a tibial preparation system  10 ,  210 ,  310 ,  410 , or other tibial preparation system can be used to resect a portion or portions of the tibia, such that the proximal end of the tibia comprises generally a flat plane or plateau. Based on pre-operative determinations of desired varus/valgus, posterior/anterior, and/or other angles for this tibial resection plane, the plateau can be perpendicular to the mechanical axis, or at an angle other than perpendicular to the mechanical axis. 
     Prior to insertion of the knee distraction device  612  into the knee joint, an appropriately sized and/or configured inner body portion  616  can be chosen. For example, the inner body portion  616  can indicate “LEFT” for a left leg and “RIGHT” for a right leg. Additionally, prior to insertion of the knee distraction device  612 , osteophytes on the femur and/or tibia can be removed to prevent obstruction and interference. 
       FIGS.  49   a  and  49   b    show the leg in full extension, with a portion of the knee distraction device  612  inserted into the knee joint. The distraction elements  626  are shown inserted underneath the femoral condyles, and above the tibial plateau, such that one distraction element  626  is located generally underneath one condyle, and another distraction element  626  is located generally under the other condyle. The tibial baseplate  624  is also shown inserted into the knee joint. 
     Prior to or after insertion of the knee distraction device  612 , the laser  42  of the surgical orientation device  12  can be turned on, such that a laser beam or beams emanate from the optical element or elements  32 . For example, and as shown by the arrow in  FIG.  49   a   , the user can press one of the user inputs  26 . The laser beams are illustrated in dashed lines in  FIGS.  49   a    and  49   b.    
     With reference to  FIGS.  49   a ,  49   b ,  50   a , and  50   b   , once a portion of the knee distraction device  612  is inserted into the knee joint, the distraction elements  626  can be moved up or down by turning the adjustment devices  620 . For example, the distraction elements  626  can be moved away from the tibial baseplate  624  and into contact with distal aspects of the femoral condyles, thereby causing the knee distraction device  12  to apply an opposing force or forces to the proximal tibia and the distal aspect of the femoral condyles. This force or forces can distract the knee joint and its surrounding soft tissue and/or ligaments. Each distraction element  626  can be moved independently, and as described above, if desired each distraction element  626  can apply a different amount of pressure or force to each femoral condyle. In a preferred arrangement, and as described above, as a distraction element  626  moves, the distraction element  626  can cause identical movement of the inner body portion  616 . In other embodiments, the inner body portion  616  can remain stationary while the distraction elements  626  are moved. 
     With continued reference to  FIGS.  49   a ,  49   b ,  50   a , and  50   b   , the laser beam or beams emanating from the surgical orientation device  12  can provide an indication of, and/or facilitate, alignment of the femoral preparation system  610 . For example, while the distraction elements  626  are being moved and/or adjusted, and the knee joint is being distracted, the laser beams can move towards a desired anatomical landmark or landmarks. As shown in  FIG.  50   b   , one of these landmarks can be on the hip and/or femoral head, and the other can be on the foot and/or ankle. These landmarks can be used to identify an orientation of the mechanical axis. For example, if the laser beams are pointing to one or more of these landmarks, the user can have a visual indication that the surgical orientation device  12  is generally aligned with the mechanical axis. The user can also have a visual indication that a gap, or distance, between one femoral condyle and the tibial plateau is substantially identical to the gap, or distance, between the other femoral condyle and the tibial plateau. In some embodiments, the user can release one or more ligaments in the knee joint prior to or during the knee distraction in order to facilitate simultaneous symmetry of the gaps, mechanical axis alignment, and/or balancing of the soft tissue and/or ligaments in the knee joint. 
     During distraction, the surgical orientation device  12  can be configured to measure and display tension within the soft tissue on the medial and/or lateral sides of the knee joint. For example, the knee distraction device  612  can comprise sensors, or other structures, which can relay information to the surgical orientation device about the degree of tensile force being exerted upon the distraction element or elements  626 , and/or the tibial baseplate  624 . The surgical orientation device  12  can display this information, for example, on the display  24 . If the tension on a medial or lateral side of the knee is too great, the user can change the tension by adjusting (e.g. turning) one or more of the adjustment members  620 . 
     Once the distraction elements  626  have applied a desired level of pressure or force against the condyles of the femur, and/or the femoral preparation system  610  is aligned with the mechanical axis (or other axial line), a drill or other cutting tool can be used to drill holes through the openings  646  of the knee distraction device  612  into the femur. In some embodiments, the openings  646  closest to the outer body portion  618  can be used. In other embodiments, different sets of openings  646  can be used. The openings  646  which are selected can determine and/or change an orientation and/or arrangement of reference pins which are placed into the femur. This orientation and/or arrangement of reference pins can determine the orientation of a cutting block which can be attached to the reference pins after the femoral preparation system  10  is removed. For example, if the user has pre-operatively determined that a cutting plane along the distal femur should be oriented at three degrees in a varus/valgus direction relative to the mechanical axis, the user can select a set of openings  646  which provide for a three degree slope, and drill holes through these openings  646 . 
     These drilled holes can serve as reference holes, and can be used for insertion of reference pins  647 . As shown in  FIGS.  51   a  and  51   b   , the reference pins  647  can be inserted through the openings  646  and into the reference holes in the femur. Once the reference pins are inserted into the femur, the femoral preparation system  610  can be removed, and a cutting block  648 . The cutting block  648  can be placed onto or coupled to the reference pins. As shown in  FIG.  52   , once the cutting block  648  is attached, a saw or other cutting device can then be used to make an appropriate DFC cut or cuts of the femur. 
     In some knee joint procedures, another cut which can be made is a posterior femoral cut (PFC). In preparation for the posterior femoral cut, the leg can be placed in approximately 90 degrees of flexion.  FIG.  53    shows the leg in flexion, with the tibial baseplate  624  and distraction elements  626  again extended inside the knee joint. The body  614  of the knee distraction device  612  can sit flush with a plateau formed on the resected femoral condyles from the DFC. 
     Once the knee distraction device  612  is inserted into the knee joint, the adjustment devices  626  on either side of the outer body portion  618  can be turned to individually move the distraction elements  626  away from the tibial baseplate  624 , thereby distracting the knee joint and applying an individual opposing force or forces to the tibial plateau and the femoral condyles. Each condyle can be distracted individually, simultaneously, and/or consecutively. 
       FIGS.  53 ,  54 , and  55    show the knee distraction device  612  during adjustment of the distraction elements  626 . As shown in  FIGS.  54  and  55   , the user can activate the laser  42  on the surgical orientation device  12  to facilitate alignment of the surgical orientation device  12  with the mechanical axis. For example, the knee distraction device  12  can be adjusted until a laser hits a landmark such as the area between the first and second toe on the patient&#39;s foot. 
     As shown in  FIG.  56   , the stylus  622  can then be positioned and/or adjusted to assess a level of the anterior cortex resection. For example, with the knee joint in full flexion, the tip of the stylus  622  can be brought down and into contact with the femur. The stylus  622  can then be moved along the femur to measure or identify a desired size for the femoral knee joint prosthetic. 
     In some embodiments, an additional device can be used to project a laser beam or beams onto the resected distal surface of the femur to create a cross pattern. This cross pattern can be used, for example, to check the rotational orientation of the knee distraction device  612  relative to the femur by comparison of the positions of the beams relative to the epicondylar axis of the femur and a Whiteside&#39;s line. 
     As shown in  FIG.  56   , once the knee distraction device  612  is aligned with the mechanical axis, holes can be drilled into the femur, and reference pins  647  can be inserted. The reference pins  647  can be inserted into various openings  646 , again depending on the desired angle of resection. For example, and as described above, some of the openings  646  can be located at slightly different levels or elevations on the inner body portion  616 . Depending on where the reference pins  647  are inserted, a slightly different angle of resection can be achieved (e.g. zero degrees, plus three degrees, minus three degrees relative to a plane perpendicular to the mechanical axis in the tibia). 
     Once the reference pins  647  are inserted, a cutting block  650  can be placed onto or coupled with the reference pins  647 , for example as shown in  FIG.  57   . A saw or other cutting device can then make appropriate PFC cut or cuts (e.g. an anterior, additional posterior, and/or chamfer) along the femur. 
     IV. Attachment of Prosthetic Components 
     Once all of the tibial and/or femoral cuts are made with the systems and/or methods described above, a knee joint prosthetic or prosthetics can be attached to the distal femur and/or proximal tibia. The knee joint prosthetic devices can comprise a replacement knee joint. The replacement knee joint can be evaluated by the user to verify that alignment of the prosthetic components in the replacement knee joint does not create any undesired wear, interference, and/or damage to the patient&#39;s anatomy, or to the prosthetic components themselves. 
     V. User Interfaces 
     The systems and methods described above can each incorporate the use of a measuring device, such as, for example, the surgical orientation device  12 . As described above, the surgical orientation device  12  can comprise at least one user input, a display and an electronic control unit. The user inputs and display, and/or the combination of the inputs, display, and electronic control unit can together form part of an interactive user interface. For example, the interactive user interface can comprise a housing (e.g., housing  20  described above), a coupling member (e.g., coupling device  14  described above) formed on or within the housing configured to removably couple the user interface to an alignment device (e.g., universal jig  16  described above), a sensor (e.g., sensor  40  described above), an electronic control unit (e.g., electronic control unit  1102  described above), a user input (e.g., user input  26  described above, which can transmit input commands to the electronic control unit), and a display (e.g., display  24  described above). 
     The interactive user interface can comprise a graphical user interface having an interactive window displaying on-screen graphics. For example, the interactive user interface can provide the user with a plurality of screen displays. The screen displays can illustrate the steps to be performed in a surgical procedure and can guide the user through the performance of the steps. Each screen display can comprise one or more on-screen graphics. The on-screen graphics can comprise one or more visual cues or indicators to prompt the user as to what step or steps to take next during one of the procedural methods described above. The visual cues referenced herein can comprise instructive images, diagrams, pictoral representations, icons, animations, visual cues, charts, numerical readings, measurements, textual instructions, warnings (visual and/or audible), or other data. The interactive user interface can be configured to alter attributes (e.g., color) of the on-screen graphics according to one or more data protocols. The interactive user interface can provide visual feedback to the user during performance of one or more surgical procedures. In certain embodiments, the interactive user interface can be configured to generate graphical user interface (“GUI”) images to be displayed to the user. As described above, the user can interact with the surgical orientation device  12  via one or more user input devices  1114  (e.g., buttons, switches, touchscreen displays, scroll wheel, track ball, keyboard, remote controls, a microphone in conjunction with speech recognition software). The interactive user interface further can allow the user to confirm that a step has been completed (for example, by pressing a user input button). The interactive user interface can allow the user to enter data (e.g., a numerical value, such as a distance, an angle, and/or the like), verify a position of the surgical orientation device  12 , turn a visible alignment indication system on and off, and/or turn the entire surgical orientation device on and off. In certain embodiments, the interactive user interface provides one or more drop-down lists or menus from which a user can make selections. For example, the user can make selections from a drop-down list using a scroll wheel, trackball, and/or a series of button presses. In some embodiments, the user interface provides a drop-down list of predicates that dynamically updates based on user input. 
     In at least one embodiment, a module for creating an interactive user interface can comprise a computer readable medium having computer readable program code embodied therein. The computer readable program code can comprise a computer readable program code configured to display one or more of a plurality of GUI images on a user interface of a surgical orientation device, the GUI images comprising instructive images related to the performance of a surgical procedure. The computer readable program code can be configured to receive instructions from a user identifying the surgical procedure to be performed (e.g., which joint and/or right or left). The computer readable program code can be configured to show the user steps to be performed in the identified process for the identified surgical procedure. The computer readable program code can be configured to guide the user in performance of the steps. For example, the computer readable program code can be configured to receive from the user an instruction to continue to the next step in the procedure, to receive orientation data from a sensor mounted within the surgical orientation device, and to display the orientation data on the user interface of the surgical orientation device. 
     In at least one embodiment, the surgical orientation device  12  described above can comprise a display module configured to display information and a sensor module configured to monitor the position and orientation of the surgical orientation device  12  in a three-dimensional coordinate reference system, and to generate orientation data corresponding to the monitored position and orientation of the surgical orientation device. The surgical orientation device  12  can further comprise a control module configured to receive the orientation data from the sensor module and convert it to objective signals for presentation on the display module, the control module also configured to display a set of GUI images or other on-screen graphics on the display module, the GUI images or on-screen graphics representing the orientation data received from the sensor module and also representing instructive images related to the performance of the joint replacement surgery. 
     In at least one embodiment, the surgical orientation device  12  can receive orientation data from a sensor module, receive input commands from a user input module to store orientation data from a user input module, convert the orientation data to a human readable format for presentation on a display device, and display on the display device on-screen graphics or GUI images for communicating information to a user based on the input commands and the orientation data, the information comprising instructive images for performing a joint replacement surgery and one or more visual indicators of a current orientation of the display device with respect to a fiducial, or reference, orientation. 
     In at least one embodiment, the surgical orientation device  12  described herein can comprise a sensor module attached to an alignment jig and configured to measure and record a fiducial orientation and to continuously collect orientation data of the surgical orientation device, a display module configured to display at least one visual indicator of the orientation of the surgical orientation device with respect to the fiducial, or reference, orientation, the display module further configured to display instructive images of one or more steps to be performed by the surgeon during the joint replacement surgery, and a control module configured to receive the orientation data and to convert the orientation data to objective signals for presentation on the display module. 
       FIG.  58 A- 61 K  show various screen shots which can form part of the interactive user interface or interfaces described above. For example,  FIGS.  58 A,  58 B, and  58 C  illustrate display screen shots for assisting a user in using a measuring device, for example the surgical orientation device  12 . The screen shots can be seen, for example, on a display of the measuring device when the device is in startup mode, standby mode, and system fault mode (e.g., system failure mode), respectively. 
     As shown in  FIG.  58 A , an interface screen can illuminate in response to pressing a user input, e.g., a center button on the surgical orientation device  12 . Thereafter, a message can be displayed indicating to the user that the surgical orientation device  12  is preparing for operation. The message can be a display of text on a screen, as illustrated in  FIG.  58 A , an audible sound, or other signal to the user to wait for the device to confirm a proper operational state. For example, a variety of self-tests can be performed. In one embodiment, information about the operating system, such as its version, can be displayed for review. 
       FIG.  58 B  shows an operational state of the surgical orientation device  12  in which the surgical orientation device  12  is ready to receive input indicating that a procedure can begin. The surgical orientation device  12  can be configured to prompt the user to initiate operation when ready, for example by pressing a user input  26 . In one embodiment of a surgical orientation device  12 , the user input  26  can comprise a button provided on a front face of the surgical orientation device  12 . The image in  FIG.  58 B  can be displayed in response to pressing a center button of the surgical orientation device  12  while the image on  FIG.  58 A  is displayed. In other embodiments, the user can press one or more buttons while the image in  FIG.  58 A  is displayed in order to initiate the surgical orientation device  12  for use with surgical procedures for different joints (e.g. right knee joint, left knee joint, right hip joint, left hip joint, either right or left hip joint). For example, the user can toggle among displays for each joint until the setting for the appropriate joint is found. In the standby mode of  FIG.  58 B , the display  24  can provide an on-screen graphic of one or more parameters to be used during the procedure. For example, a numerical display can be provided for one or more angles, such as flexion-extension angles, varus-valgus angles, or rotation angles (e.g. angles of rotation about the mechanical axis of the leg). The on-screen graphic can comprise alphanumeric text or symbols of various colors, one or more background colors, one or more icons, one or more GUI images, animations, arrows, and the like. 
       FIG.  58 B  also illustrates that textual instructions regarding how to begin a procedure once the type of procedure has been selected. For example, a visual cue can be provided on the display  24  to start a procedure.  FIG.  58 B  shows that the word “START” can be displayed along with an arrow pointing toward a button or other device. 
       FIG.  58 C  illustrates a visual notification or warning screen. In certain embodiments, the color of the background of the display can be changed when the device is operating in the fault mode. The interactive user interface can also provide an audible alarm or other audible indication to the user when the device is in a system fault mode. This display screen can be configured such that the screen is displayed when the surgical orientation device  12  fails to pass a self test or tests that can automatically be initiated by the surgical orientation device  12  before or during use of the surgical orientation device  12 . 
       FIG.  59 A  shows a display screen shot which can instruct the user to position a surgical instrument, for example, an extramedullary device (e.g. the extramedullary alignment guide  313 ) and/or a cutting block, on the tibia. In one embodiment, the display screen shot can include an image of the tibia and the surgical instrument displayed adjacent to a particular aspect of the tibia (e.g., the anterior surface). The instructive images in  FIG.  59 A  can be displayed in response to pressing a button located immediately below the arrow displayed in  FIG.  58 B . In a preferred arrangement, the user can move from one screen to the following screen by pressing a button indicated below an arrow displayed on the current screen, and can navigate back to prior screens by pressing a different button on the surgical orientation device  12  (for example a left arrow or BACK button). In certain embodiments, a user can power off the display screen by pressing two different buttons simultaneously. 
       FIG.  59 B  shows a display screen shot which can instruct the user to provide an orientation assembly (e.g. tibial preparation system  310   a ). In one method, the user can be provided with an image of the surgical orientation device  12  or other measuring device and the landmark acquisition assembly  312 , and the visual cues of  FIG.  59 B  can instruct the user to couple these structures together. The visual cues can include an animation or series of animations. The screen shot illustrated in  FIG.  59 B , as well as other screen shots described herein, can illustrate that the user interface can include a combination of visual cues or indicators to provide instructions to the user. For example, text can be provided along with instructive images or icons. In some embodiments, either text or visual cues can be provided alone. In another embodiment, audible cues can be provided alone or in combination with text and/or visual cues. The audible cues can comprise, for example, speech, a buzzer, or an alarm. 
       FIG.  59 C  shows a display screen shot which can instruct the user to position an orientation assembly (e.g. tibial preparation system  310   a ) in a coronal plane of the tibia and to direct the surgical orientation device  12  or other measuring device to acquire the coronal plane of the tibia. The instructive images in  FIG.  59 C  can be displayed in response to pressing the central button located immediately below the arrow displayed in  FIG.  59 B . 
     In one method, such as one of the methods described above, the user can be provided with a surgical orientation device  12  or other measuring device and a landmark acquisition assembly  312 , coupled together. The visual cues of  FIG.  59 C  can instruct the user to position the tibial preparation system  310   a  with respect to the tibia by palpating and placing a tip  326  of a secondary rod  320  of the landmark acquisition assembly  312  on the location of attachment of the lateral collateral ligament to the proximal fibular head, and placing a second tip  326  on the apex of the lateral malleolus. 
       FIG.  59 C  can further instruct the user to press a button of the surgical orientation device  12  indicated by the screen (for example by a green arrow) to direct the surgical orientation device  12  to acquire the coronal plane of the tibia. In one embodiment, the user interface can provide information on the status of the process of acquiring the coronal plane, as well as instruction for operation of the surgical orientation device  12 . For example, the bottom right hand corner of the display  24  can provide information on the status of the acquisition of the coronal plane. The information on the screen regarding the status of the acquisition of the coronal plane can be designed to attract the attention of the user by, for example, flashing a first color such as green to indicate that the surgical orientation device  12  is aligned and a second color, such as grey, to indicate that the surgical orientation device  12  is out of alignment. 
     This color indication can be combined with a more specific visual cue such as the visual depiction of the degree of alignment of the surgical orientation device. After the user has pressed a button on the surgical orientation device directing the surgical orientation device  12  to acquire the coronal plane, the surgical orientation device  12  can initiate a recording of the output of one or more sensors. Such recording can follow the application of a data protocol that is selected to minimize error in the measurement, e.g., excluding transient reading and processing readings over a period, such as by employing median and averaging techniques or stabilization algorithms as described above or otherwise manipulating the readings. In certain embodiments, the data protocol is selected to record in memory the last stable data measurement received before the button was pressed. 
     In addition, in certain embodiments, the screen in  FIG.  59 C  can provide the user with feedback as to whether the surgical orientation device  12  is being maintained parallel (e.g. within an allowable range) to the coronal plane of the tibia. For example, the display  24  can provide the user with feedback on the rotation (e.g. roll) of the surgical orientation device  12  about a first axis. Instead of displaying a degree measurement, the display  24  can be configured to display a pictorial representation of a bubble that, for so long as the surgical orientation device  12  remains parallel to the coronal plane of the tibia within an allowable range, stays within the confines of two vertical lines, one line on either side of the bubble. The two vertical lines marking the confines of the “level” orientation range can correspond to a relative angle or tilt of plus and minus three degrees or plus and minus one degree, for example. If the bubble moves beyond either of these lines, the background color of the display  24  behind the bubble can change, for example, from green to amber, to indicate that the orientation is out of the acceptable range. 
       FIG.  59 C  also shows that a visual cue which can be provided to the user that the surgical orientation device  12  is in the process of acquiring the coronal plane. For example, the text “ACQUIRING” can appear on the display  24 . The text “ACQUIRING” can instruct the user to continue to maintain the orientation of the surgical orientation device  12  so that the surgical orientation device  12  is aligned with the coronal plane. 
       FIG.  59 D  shows a display screen shot which can instruct the user to reposition or move the surgical orientation device  12 , or other measuring device, such that the surgical orientation device  12  is attached to a surgical instrument (e.g. extramedullary alignment guide  313 ) on the tibia. The on-screen graphic of images and visual cues of  FIG.  59 D  can be displayed in response to pressing the central button located immediately below the arrow displayed in  FIG.  59 C . 
     In one embodiment, the screen shot in  FIG.  59 D  can comprise a visual cue or indicator which can comprise an image of the tibia and the surgical instrument displayed adjacent to a particular aspect of the tibia (e.g., the anterior surface), with the surgical orientation device  12  or other measuring device coupled with an anterior surface or side of the surgical instrument. 
       FIG.  59 D  can also show a visual cue which can instruct the user to maintain the tibia in its current position while carrying out the other instructions of  FIG.  59 D . Maintaining the tibial position at this stage of the procedure can be one way of minimizing error in the use of data acquired by the surgical orientation device  12 . In certain embodiments of the surgical orientation device  12 , the screen in  FIG.  59 D  can provide feedback as to whether the surgical orientation device  12  is being maintained parallel (e.g. within an allowable range) to the coronal plane of the tibia, for example by employing the same bubble pictorial method, or GUI image, described for  FIG.  59 D  above. Such feedback can inform the user of any unacceptable rotation (e.g. roll) of the surgical orientation device  12 . 
       FIG.  59 E  shows a display screen shot which can inform the user to set the posterior slope of a cutting block (e.g. cutting block  84 ) or other surgical instrument operatively coupled to the anterior side of the tibia. The instructive images in  FIG.  59 E  can be displayed in response to pressing the central button located immediately below the arrow displayed in  FIG.  59 D . 
     For example, the bottom left hand corner of the screen shown in  FIG.  59    E can provide a degree measurement of the posterior slope being set by the user in real time as the surgical instrument (e.g. extramedullary alignment guide  313 ) and surgical orientation device  12  are adjusted, and can inform the user to insert a first pin through the cutting block and into the proximal tibia. In certain embodiments, the screen in  FIG.  59 E  can provide feedback as to whether the surgical orientation device  12  is being maintained parallel (e.g. within an allowable range) to the coronal plane of the tibia, for example by employing the same bubble pictorial method described for  FIG.  59 C . Such feedback can enable the user to control variation in the rotation (e.g. roll) of the surgical orientation device  12  within an acceptable limit.  FIG.  59 E  shows an animated depiction of the pin being inserted through the cutting block and into the proximal tibia, to suggest its insertion by the user. A text instruction and/or audible signal can be provided instead of, or in addition to, the animated depiction. For example, a text instruction can be combined with an animated depiction to provide a more comprehensive visual cue. 
       FIG.  59 F  shows a display screen shot which can instruct the user to command the surgical orientation device  12  to acquire a sagittal plane of the tibia. As described above, the sagittal plane can be a plane extending through anterior and posterior surfaces of the tibia and including the portion of the mechanical axis extending through the tibia. The images in  FIG.  59 F  can be displayed in response to pressing the central button displayed in  FIG.  59 E . 
     The display screen shot shown in  FIG.  59 F  can also instruct the user to maintain the tibia in its current position as a way of minimizing errors that might result from movement of the tibia. Such a visual cue can include, for example, a text instruction located at the top of the screen and an arrow directed at a button. Pressing a button can activate a light source on the device (e.g. laser  42 ), which can be directed distally. For example, the surgical orientation device  12  can include three user inputs  26  in the form of buttons extending from left to right across the surgical orientation device  12 , and the arrow can direct the user to press the button furthest to the right. 
       FIG.  59 G  shows a display screen shot which can instruct the user to set the varus/valgus angle of the cutting block (e.g. cutting block  84 ) or other surgical device. The images in  FIG.  59 G  can be displayed in response to pressing the central button displayed in  FIG.  59 F . 
     The bottom right hand corner of the screen shown in  FIG.  59 G  can provide a real-time degree measurement of the varus/valgus angle of the surgical orientation device  12  and the cutting block. This degree measurement can correspond to the varus/valgus angle of a cutting plane. The pictorial representation of the proximal tibia and cutting block at the right of the screen can informs the user to insert a second pin through the block and into the proximal tibia.  FIG.  59 G  can also provide an animated depiction of the second pin being inserted through the block and into the proximal tibia, to suggest its insertion. The left-hand portion of the screen can show the varus/valgus angle of the surgical orientation device  12  and the cutting block graphically. 
       FIG.  59 H  shows a display screen shot illustrating a degree measurement of the angles of proximal tibia resection, based on the angle of the surgical orientation device  12  and the cutting block with respect to the tibia. In one embodiment, the screen can provide both the anterior-posterior angle and the varus/valgus angle of the cutting block both in degree measurement and pictorially. The images in  FIG.  59 H  can be displayed in response to pressing the central button displayed in  FIG.  59 G . 
       FIGS.  60 A,  60 B,  60 C, and  60 D  show display screen shots that can be displayed by the interactive user interface of the surgical orientation device  12  or other measuring device in connection with preparation of a portion of a joint. For example, the screen shots shown in  FIGS.  60 A,  60 B,  60 C, and  60 D  can be displayed in connection with a femoral cut and/or knee distraction as described above. In at least one knee procedure, various steps can be performed by the user prior to the user interface interactions illustrated in  FIGS.  60 A,  60 B,  60 C, and  60 D . For example, a tibial resection can be performed using one of the systems and/or methods described above. After these procedures are complete, the user can use and refer to the display screens of  FIGS.  60 A,  60 B,  60 C, and  60 D . 
       FIG.  60 A  shows a display screen shot which can inform the user that the surgical orientation device  12  is in a “Femoral Preparation” mode, and can provide an image of an arrow instructing the user to push a button (e.g., a center button on the surgical orientation device  12 ) when the user is ready to continue the procedure. The images in  FIG.  60 A  can be displayed, for example, in response to pressing the central button displayed in  FIG.  59 H . 
       FIG.  60 B  shows a display screen shot which can, for example, inform the user that the surgical orientation device  12  is in an “Extension-Balancing” mode. The images in  FIG.  60 B  can be displayed in response to pressing the central button displayed in  FIG.  60 A . 
     The display screen shot shown in  FIG.  60 B  can provide a visual cue informing the user that the knee being operated on can be in an extension position and that a knee distraction device (e.g. knee distraction device  612 ), coupled with the surgical orientation device  12 , can be inserted into the knee joint and into contact with the femur. 
       FIG.  60 B  can further illustrate a visual cue instructing the user to adjust the knee distraction device to balance the tension between the ligaments in the knee. For example, the screen shot shown in  FIG.  60 B  can contain a visual cue directing the user to align a tibial laser, which can shine distally from the surgical orientation device  12  along the direction of the tibia, and a femoral laser, which can shine proximally from the surgical orientation device  12  along the direction of the femur, with certain landmarks on the body. The display screen shot shown in  FIG.  60 B  can also display information indicating that a user input  26  (e.g. button) can be pushed on the surgical orientation device  12  to turn the laser off 
       FIG.  60 C  shows a display screen shot which can, for example, inform the user that the surgical orientation device  12  is in a “Flexion-Balancing” mode. The images in  FIG.  60 C  can be displayed in response to pressing the central button displayed in  FIG.  60 B . 
     The display screen shot shown in  FIG.  60 C  can provide a visual cue informing the user that the knee being operated on can be in a flexion position and that a knee distraction device (e.g. knee distraction device  612 ), coupled with the surgical orientation device  12 , can be inserted into the knee joint and into contact with one or more femoral condyles. The display screen shot shown in  FIG.  60 C  can further illustrate a visual cue instructing the user to adjust the knee distraction device to balance the tension between the ligaments in the knee. For example, the surgical orientation device  12  can contain a visual cue directing the user to align a tibial laser, which can shine distally from the measuring device along the direction of the tibia, with one or more landmarks on the body. The display screen shot shown in  FIG.  60 C  can also display information indicating that a user input  26  (e.g. button) can be pushed on the surgical orientation device  12  to turn the laser off. 
       FIG.  60 D  shows a display screen shot which can, for example, inform the user that the surgical orientation device  12  is in a “Femoral-Sizing” mode, and can illustrate a flexed knee being sized. The sizing can be accomplished in any suitable manner, such as by using a stylus. The display screen shot shown in  FIG.  60 D  can also display information indicating that a user input  26  (e.g. button) can be pushed on the surgical orientation device  12  to turn the laser off. The images shown in  FIG.  60 D  can be displayed in response to pressing the central button in  FIG.  60 B . 
       FIGS.  61 A-K  show display screen shots that can be displayed by the user interface of the surgical orientation device  12  or other measuring device in connection with preparation of a portion of a joint. For example, the screen shots shown in  FIGS.  61 A-K  can be displayed in connection with a tibial preparation described above. 
       FIG.  61 A  shows a display screen shot which can, for example, inform the user that the surgical orientation device is in a joint selection mode. The user can select which knee (right or left) will be operated on by pressing a user input  26  on the surgical orientation device  12 . For example, the user can press a left button for the left knee, and a right button for the right knee. 
       FIG.  61 B  shows a display screen shot which can provide a visual cue informing the user that an orthopedic fixture (e.g. universal jig  16 ) can be assembled, if it has not already been assembled. The images in  FIG.  61 B  can be displayed in response to pressing a button located immediately below the arrow or arrows displayed in  FIG.  61 A . 
       FIG.  61 C  shows a display screen shot which can provide a visual cue informing the user that the universal jig  16  can be coupled to the surgical orientation device  12 , for example with the coupling device  14  described above. The images in  FIG.  61 C  can be displayed in response to pressing a button located immediately below the arrow displayed in  FIG.  61 B . 
       FIG.  61 D  shows a display screen shot which can provide a visual cue informing the user that a tibia preparation system (e.g. tibia preparation system  10 ) can be positioned adjacent an anterior surface of the tibia. For example, the screen in  FIG.  61 D  can provide a visual cue informing the user that the tibial preparation system  10  can be positioned and/or moved until the surgical orientation device  12  is generally centered with the insertion of an anterior cruciate ligament and a medial tibial insertion of the patella tendon in a patient&#39;s knee. 
     The images in  FIG.  61 D  can be displayed in response to pressing a button located immediately below the arrow displayed in  FIG.  61 C . In a preferred arrangement, the user can move from one screen to the following screen by pressing a button indicated below an arrow displayed on the current screen, and can navigate back to prior screens by pressing a different button on the surgical orientation device  12  (for example a left arrow or BACK button). 
     In some embodiments, the screen in  FIG.  61 D , or other screens, can provide the user with feedback as to whether the surgical orientation device  12  is being maintained parallel (e.g. within an allowable range) of an anatomical plane. For example, in one embodiment, the user interface can provide information on the status of the process of acquiring the coronal and/or sagittal planes containing the mechanical axis, as well as instructive images or textual instructions regarding operation of the surgical orientation device  12  or steps to be performed in a surgical procedure. 
     In some embodiments, the interactive user interface can be configured to display a red “shaky hand” on-screen graphic or icon to indicate to the user that the device is not currently receiving stable measurements. In certain embodiments, the electronic control unit  1102  can be configured to ignore user attempts to register or record reference angles when the “shaky hand” icon is being displayed. The display  24  can also provide a textual, audible, or other visual notification to the user that the current measurements are unstable. As one example, the background color of the display screen or the color of the measurement readings can be changed when the current measurements are unstable. 
     As described above, the display  24  can display an on-screen graphic of a bubble (as described above) that, for so long as the surgical orientation device  12  remains parallel to the coronal and/or sagittal plane of the tibia within an allowable range, stays within the confines of two vertical lines, one line on either side of the bubble. If the bubble moves beyond either of these lines the background color of the display  24  behind the bubble can change, for example, from green to amber, to indicate that the orientation is out of the acceptable range. 
       FIG.  61 E  shows a display screen shot which can provide a visual cue informing the user that a centering stylus, or other measuring device (e.g. measuring device  109   a ), can be used to measure a first distance from an A/P point on top of the tibia to an optical element  32  on the surgical orientation device  12 . The images in  FIG.  61 E  can be displayed in response to pressing a button located immediately below the arrow displayed in  FIG.  61 D . 
       FIG.  61 F  shows a display screen shot which can provide a visual cue informing the user that a target probe (e.g. target probe  18   a ) can be adjusted such that its length corresponds to the distance measured by the measuring device. The images in FIG.  61 F can be displayed in response to pressing a button located immediately below the arrow displayed in  FIG.  61 E . 
       FIG.  61 G  shows a display screen shot which can provide a visual cue informing the user that the lateral malleolus can be palpated, and that a target probe (e.g target probe  18   a ) can be held or affixed adjacent the lateral malleolus. The screen in  FIG.  61 G  can also provide a visual cue informing the user that a cross-hair laser can be directed towards the probe  18   a , and the user can press a user input  26  to register the lateral malleolus. The images in  FIG.  61 G  can be displayed in response to pressing a button located immediately below the arrow displayed in  FIG.  61 F . 
       FIG.  61 H  shows a display screen shot which can provide a visual cue informing the user that the medial malleolus can be palpated, and that a target probe (e.g. target probe  18   b ) can be held or affixed adjacent the medial malleolus. The screen in  FIG.  61 G  can also provide a visual cue informing the user that a cross-hair laser can be directed towards the probe  18   a , and the user can press a user input  26  to register the lateral malleolus. The images in  FIG.  61 H  can be displayed in response to pressing a button located immediately below the arrow displayed in  FIG.  61 G . 
       FIG.  61 I  shows a display screen shot which can provide a visual cue informing the user that a universal jig (e.g. universal jig  16 ) can be adjusted to adjust the resection plane along the proximal tibia. In one embodiment, the screen can provide both an anterior-posterior angle and a varus/valgus angle of the cutting block  84  both in degree measurement and pictorially. The images in  FIG.  61 I  can be displayed in response to pressing a button located immediately below the arrow displayed in  FIG.  61 H . 
       FIG.  61 J  shows a display screen shot which can provide a visual cue informing the user that the resection depth for the tibial cut can be set. For example, the screen can continue to provide both an anterior/posterior angle and a varus/valgus angle of the cutting block  84  in degree measurement and pictorially. The images of  FIG.  61 J  can be displayed in response to pressing a button located immediately below the arrow displayed in  FIG.  61 I . 
       FIG.  61 K  shows a display screen shot which can provide a visual cue informing the user a tibial preparation procedure has completed. The screen can include a visual indication that once the procedure has been completed for one joint (e.g. left knee), the user can proceed to another joint. For example, the screen can include an arrow pointing to a user input  26 . The user can press the user input  26  to proceed to the next joint. In other embodiments, the display  24  of the interactive user interface can be configured to automatically shut off after the procedure is completed. 
     Although these inventions have been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present inventions extend beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the inventions and obvious modifications and equivalents thereof. In addition, while several variations of the inventions have been shown and described in detail, other modifications, which are within the scope of these inventions, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments can be made and still fall within the scope of the inventions. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed inventions. Thus, it is intended that the scope of at least some of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above.