Patent Publication Number: US-2023149185-A1

Title: Hip replacement navigation systems and methods

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/160,995, filed Jan. 28, 2021, which is a continuation of U.S. patent application Ser. No. 15/920,216, filed Mar. 13, 2018, which claims benefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 62/471,185, filed Mar. 14, 2017 and U.S. Provisional Patent Application No. 62/521,097, filed Jun. 16, 2017 each of which is incorporated in its entirety by reference herein. Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application is hereby incorporated by reference in its entirety under 37 CFR 1.57. 
    
    
     BACKGROUND 
     Field 
     This application is directed to the field of hip replacement, and particularly to surgical tools and methods for establishing a reference plane. This application is also directed surgical tools and methods for calculating leg length and joint offset. 
     Description of the Related Art 
     Hip replacement surgery is common and getting more common by the year. One persistent issue with hip replacement is poor placement of the cup and ball components of the prosthetic hip joint. For example, the cup is optimally placed in a specific abduction and anteversion orientations. While an acceptable window of deviation from the optimal abduction and anteversion angles has been observed in clinical practice for several reasons an unacceptably high percentage of patients have the cup of the artificial hip joint out of this window. 
     Unfortunately, misalignment can lead to dislocation of the hip as soon as within one year of the implantation procedure. This is particularly problematic because recovery from a hip procedure can take many months. Patients undergoing a revision so soon after the initial implantation will certainly be dissatisfied with their care, being subject to addition redundant surgery. Of course, all surgery carries some degree of risk. These poor outcomes are unsatisfactory for patients and surgeons and are inefficient for the healthcare system as a whole. 
     SUMMARY 
     There is a need for improved systems and methods for providing for proper alignment of hip components with a patient&#39;s anatomy during a hip replacement procedure. This can involve use of a table reference frame. This can involve use of a vertical reference plane. This can involve use of a reference plane that approximates the Anterior Pelvic Plane. This can involve providing the user with additional information related to the anatomy including leg length and joint offset. 
     In some embodiments, a method of positioning a medical prosthesis is provided. The method can include establishing a vertical plane with a measuring device. The method can include positioning a probe to contact a point. The method can include recording a position of the probe when the probe is contacting the point before replacing a joint. The method can include recording a second position of the probe when the probe is contacting the point after replacing the joint. In some embodiments, a comparison between the first position and the second position indicates a change in leg length or joint offset. 
     In some embodiments, the method can include coupling the measuring device and the probe to a patient. In some embodiments, the point is a structure. In some embodiments, the point is a burr. In some embodiments, the point is an anatomical landmark. In some embodiments, the method can include determining cup angles relative to the vertical plane. In some embodiments, the method can include positioning a medical prosthesis at an angle relative to the vertical plane. In some embodiments, the method can include manually repositioning the femur after replacing the joint. In some embodiments, the method can include establishing a horizontal plane with a measuring device, wherein the vertical plane and the horizontal plane define a reference frame. 
     In some embodiments, a method of positioning a medical prosthesis is provided. The method can include establishing a vertical plane with a measuring device. The method can include projecting a pattern of light onto the leg of a patient. The method can include recording the incidence of light on the leg of a patient. The method can include replacing the joint by inserting a cup, wherein angles of the cup are measured relative to the vertical plane. The method can include projecting the pattern light onto the leg of the patient after replacing the joint. The method can include repositioning the leg to align the recording of the incidence of light with the pattern of light. 
     In some embodiments, the method can include recording a position of a probe when contacting a point pre-dislocation. In some embodiments, the method can include recording a position of a probe when contacting a point post-instrumentation. In some embodiments, the method can include determining a change in leg length. In some embodiments, the method can include determining a change in leg length in the vertical plane. In some embodiments, the method can include determining a change in joint offset. In some embodiments, the method can include determining a change in joint offset in a plane perpendicular to the vertical plane. In some embodiments, the method can include establishing a horizontal plane with a measuring device, wherein the vertical plane and the horizontal plane define a reference frame. In some embodiments, the method can include recording a point in the reference frame. In some embodiments, the method can include recording a point pre-operatively in the reference frame. In some embodiments, the method can include recording a point post-operatively in the reference frame. 
     In some embodiments, a surgical system for assisting a surgeon in obtaining correct orientation of an acetabular prosthetic socket in a patient&#39;s acetabulum in provided. In some embodiments, the instrument can include a support device. The instrument can include a first electronic orientation device having a coupler for releasably coupling the first electronic orientation device to the support device. In some embodiments, the first electronic orientation device comprises at least one inertial sensor. In some embodiments, the first electronic orientation device and the second electronic orientation device are adapted to establish a reference plane based upon a direction of gravity. 
     In some embodiments, the system can include a probe assembly comprising a base portion and an elongate member configured to pivot and translate relative to the base portion, the probe assembly comprising an second electronic orientation device, wherein the second electronic orientation device comprises at least one inertial sensor. In some embodiments, the first electronic orientation device and the second electronic orientation device are adapted to record a point when the probe contacts a point. In some embodiments, the first electronic orientation device and the second electronic orientation device are adapted to record a point when the probe contacts a point pre-operatively and post-operatively. In some embodiments, the at least one inertial sensor of the first electronic orientation device or the at least one inertial sensor of the second electronic orientation device comprises an accelerometer. In some embodiments, the reference plane comprises a vertical plane. In some embodiments, the first electronic orientation device includes a display configured to provide an indication of the change in angular position of the second electronic orientation device relative to the reference plane. In some embodiments, the system can include an optical component configured to project a pattern of light. 
     In some embodiments, a hip joint navigation system is provided. The system can include a jig assembly. The system can include a first inertial navigation device configured to be immovably coupled to the jig assembly. The system can include an optical component configured to project a pattern of light, wherein incidence of the pattern of light can be record to assist the user in realigning the femur to a pre-operative position. The system can include a second inertial navigation device configured to determine the orientation of a probe when the probe is moved to touch a point. 
     In some embodiments, the pattern of light is a cross-hair. In some embodiments, the pattern of light is two lines. In some embodiments, the pattern of light is three points. 
     There is a need for improved systems and methods for providing for proper alignment of hip components with a patient&#39;s anatomy during a hip replacement procedure. This can involve use of the Anterior Pelvic Plane. This can involve the use of a table plane. This can involve the use of an Adjusted Plane. This can involve providing the user with additional information related to the anatomy including pelvic tilt and rotation. 
     In some embodiments, a method of positioning a medical prosthesis is provided. The method can include coupling a measuring device and probe to a patient. The method can include positioning the probe to contact a first point. The method can include recording the position of the probe when the probe is contacting the first point. The method can include positioning the probe to contact a second point. The method can include recording the position of the probe when the probe is contacting the second point. The method can include positioning the probe to contact a third point. The method can include recording the position of the probe when the probe is contacting the third point. In some embodiments, the first point, the second point, and the third point define a plane, the plane can be rotated by the direction of gravity define an adjusted plane. 
     The method can include coupling the measuring device with a second measuring device, wherein the second measuring device includes a digital display to provide an indication of positional changes of the probe. In some embodiments, the first point is the ipsilateral ASIS. In some embodiments, the second point is the contralateral ASIS. The method can include positioning the probe horizontally to measure the direction of gravity. The method can include determining cup angles relative to the reference plane. The method can include positioning a medical prosthesis at an angle relative to the adjusted plane. In some embodiments, the first point and the second point define the inter-ASIS line. In some embodiments, the first point, the second point, and the third point define the anterior pelvic plane. In some embodiments, the third point is the anterior surface of the pubic symphysis. 
     In some embodiments, a surgical system for assisting a surgeon in obtaining correct orientation of an acetabular prosthetic socket in a patient&#39;s acetabulum is provided. The instrument can include a support device. The instrument can include a first electronic orientation device having a coupler for releasably coupling the first electronic orientation device to the support device, wherein the first electronic orientation device comprises at least one inertial sensor. The instrument can include a probe assembly comprising a base portion and an elongate member configured to pivot and translate relative to the base portion, wherein the elongate member has a length sufficient to enable a tip thereof to contact anatomy disposed about the pelvis at a plurality of discrete, spaced apart locations, the probe assembly comprising an second electronic orientation device, wherein the second electronic orientation device comprises at least one inertial sensor. In some embodiments, the first electronic orientation device and the second electronic orientation device are adapted to establish a reference plane based upon a direction of gravity and based upon the position of the at least one inertial sensor when the tip contacts the plurality of spaced apart locations. 
     In some embodiments, the at least one inertial sensor of the first electronic orientation device or the at least one inertial sensor of the second electronic orientation device comprises an accelerometer. In some embodiments, the reference plane comprises the inter-ASIS line. In some embodiments, the first electronic orientation device includes a display configured to provide an indication of the change in angular position of the second electronic orientation device relative to the reference plane. 
     In some embodiments, a hip joint navigation system is provided. The system can include a jig assembly. The system can include a first inertial navigation device configured to be immovably coupled to the jig assembly. The system can include a landmark acquisition probe configured to be movably coupled to the jig assembly, the landmark acquisition probe configured to move in a plurality of degrees of freedom relative to the jig assembly. The system can include a second inertial navigation device configured to determine the orientation of the landmark acquisition probe when the landmark acquisition probe is moved to touch an anatomical landmark. In some embodiments, the first inertial navigation device, the second inertial navigation device, or the first inertial navigation device and the second inertial navigation device are configured to adjusts for tilt by rotating the Anterior Pelvic Plane about the inter-ASIS line to determine a reference plane. 
     In some embodiments, the second inertial device comprises a mount device configured to detachably connect the second inertial device to the landmark acquisition probe. In some embodiments, the second inertial device comprises a camera. In some embodiments, the first inertial navigation device comprises a display. 
     In some embodiments, a method of positioning a medical prosthesis is provided. The method can include establishing a vertical plane with a measuring device. The method can include positioning a probe to contact a point. The method can include recording a position of the probe when the probe is contacting the point before replacing a joint. The method can include recording a second position of the probe when the probe is contacting the point after replacing the joint. In some embodiments, a comparison between the first position and the second position indicates a change in leg length or joint offset. 
     The method can include coupling the measuring device and the probe to a patient. In some embodiments, the point is a structure. In some embodiments, the point is a burr. In some embodiments, the point is an anatomical landmark. The method can include determining cup angles relative to the vertical plane. The method can include positioning a medical prosthesis at an angle relative to the vertical plane. The method can include manually repositioning the femur after replacing the joint. The method of claim  1 , further comprising establishing a horizontal plane with a measuring device, wherein the vertical plane and the horizontal plane define a reference frame. 
     In some embodiments, a method of positioning a medical prosthesis is provided. The method can include establishing a vertical plane with a measuring device. The method can include projecting a pattern of light onto the leg of a patient. The method can include recording the incidence of light on the leg of a patient. The method can include replacing the joint by inserting a cup, wherein one or more angles of the cup are measured relative to the vertical plane. The method can include projecting the pattern light onto the leg of the patient after replacing the joint. The method can include repositioning the leg to align the recording of the incidence of light with the pattern of light. The method can include recording a position of a probe when contacting a point pre-dislocation. The method can include recording a position of a probe when contacting a point post-instrumentation. The method can include determining a change in leg length. The method can include determining a change in leg length in the vertical plane. The method can include determining a change in joint offset. The method can include determining a change in joint offset in a plane perpendicular to the vertical plane. The method can include establishing a horizontal plane with a measuring device, wherein the vertical plane and the horizontal plane define a reference frame. The method can include recording a point in the reference frame. The method can include recording a point pre-operatively in the reference frame. The method can include recording a point post-operatively in the reference frame. 
     In some embodiments, a surgical system for assisting a surgeon in obtaining correct orientation of an acetabular prosthetic socket in a patient&#39;s acetabulum is provided. The surgical system can include a support device. The surgical system can include a first electronic orientation device having a coupler for releasably coupling the first electronic orientation device to the support device. In some embodiments, the first electronic orientation device comprises at least one inertial sensor. In some embodiments, the first electronic orientation device and the second electronic orientation device are adapted to establish a reference plane based upon a direction of gravity. 
     The surgical system can include a probe assembly comprising a base portion and an elongate member configured to pivot and translate relative to the base portion. In some embodiments, the probe assembly comprises an second electronic orientation device. In some embodiments, the second electronic orientation device comprises at least one inertial sensor. In some embodiments, the first electronic orientation device and the second electronic orientation device are adapted to record a point when the probe contacts a point. In some embodiments, the first electronic orientation device and the second electronic orientation device are adapted to record a point when the probe contacts a point pre-operatively and post-operatively. In some embodiments, the at least one inertial sensor of the first electronic orientation device or the at least one inertial sensor of the second electronic orientation device comprises an accelerometer. In some embodiments, the reference plane comprises a vertical plane. In some embodiments, the first electronic orientation device includes a display configured to provide an indication of the change in angular position of the second electronic orientation device relative to the reference plane. The surgical system can include an optical component configured to project a pattern of light. 
     In some embodiments, a hip joint navigation system is provided. The hip joint navigation system can include a jig assembly. The hip joint navigation system can include a first inertial navigation device configured to be immovably coupled to the jig assembly. The hip joint navigation system can include an optical component configured to project a pattern of light. In some embodiments, incidence of the pattern of light can be record to assist the user in realigning the femur to a pre-operative position. The hip joint navigation system can include a second inertial navigation device configured to determine the orientation of a probe when the probe is moved to touch a point. 
     In some embodiments, the pattern of light is a cross-hair. In some embodiments, the pattern of light is two lines. In some embodiments, the pattern of light is three points. In some embodiments, the optical component is configured to couple to the jig assembly with one or more magnets. The hip joint navigation system can include a target probe for recording or displaying the pattern of light, wherein the target probe comprises an anatomical contact portion and a target portion. In some embodiments, the anatomical contact portion and a target portion are separate component. In some embodiments, the anatomical contact portion comprises an incision drape. 
     In some embodiments, a hip joint navigation system is provided. The hip joint navigation system can include an impactor. The hip joint navigation system can include a coupler configured to be immovably coupled with and to be decoupled from the impactor. The hip joint navigation system can include an inertial navigation device configured to be immovably coupled to the coupler. In some embodiments, the inertial navigation device is configured to determine the orientation of the impactor as the impactor is moved. 
     The hip joint navigation system can include a universal impactor adaptor comprising the coupler. In some embodiments, the universal impactor adaptor is configured to be removably coupled to the impactor. In some embodiments, the universal impactor adaptor comprises a clamp. In some embodiments, the universal impactor adaptor comprises a magnet. 
     In some embodiments, a method of positioning a medical prosthesis is provided. The method can include coupling a measuring device and probe to a patient. The method can include positioning the probe to contact a first point. The method can include recording the position of the probe when the probe is contacting the first point. The method can include positioning the probe to contact a second point. The method can include recording the position of the probe when the probe is contacting the second point. The method can include positioning the probe to contact a third point. The method can include recording the position of the probe when the probe is contacting the third point. In some embodiments, the first point, the second point, and the third point define a plane, the plane can be rotated by the direction of gravity define an adjusted plane. 
     The method can include coupling the measuring device with a second measuring device, wherein the second measuring device includes a digital display to provide an indication of positional changes of the probe. In some embodiments, the first point is the ipsilateral ASIS. In some embodiments, the second point is the contralateral ASIS. The method can include positioning the probe horizontally to measure the direction of gravity. The method can include determining cup angles relative to the reference plane. The method can include positioning a medical prosthesis at an angle relative to the adjusted plane. In some embodiments, the first point and the second point define the inter-ASIS line. In some embodiments, the first point, the second point, and the third point define the anterior pelvic plane. In some embodiments, the third point is the anterior surface of the pubic symphysis. 
     In some embodiments, a surgical system for assisting a surgeon in obtaining correct orientation of an acetabular prosthetic socket in a patient&#39;s acetabulum is provided. The surgical system can include a support device. The surgical system can include a first electronic orientation device having a coupler for releasably coupling the first electronic orientation device to the support device. In some embodiments, the first electronic orientation device comprises at least one inertial sensor. The surgical system can include a probe assembly comprising a base portion and an elongate member configured to pivot and translate relative to the base portion. In some embodiments, the elongate member has a length sufficient to enable a tip thereof to contact anatomy disposed about the pelvis at a plurality of discrete, spaced apart locations. In some embodiments, the probe assembly comprises an second electronic orientation device. In some embodiments, the second electronic orientation device comprises at least one inertial sensor. In some embodiments, the first electronic orientation device and the second electronic orientation device are adapted to establish a reference plane based upon a direction of gravity and based upon the position of the at least one inertial sensor when the tip contacts the plurality of spaced apart locations. 
     In some embodiments, the at least one inertial sensor of the first electronic orientation device or the at least one inertial sensor of the second electronic orientation device comprises an accelerometer. In some embodiments, the reference plane comprises the inter-ASIS line. In some embodiments, the first electronic orientation device includes a display configured to provide an indication of the change in angular position of the second electronic orientation device relative to the reference plane. 
     In some embodiments, a hip joint navigation system is provided. The hip joint navigation system can include a jig assembly. The hip joint navigation system can include a first inertial navigation device configured to be immovably coupled to the jig assembly. The hip joint navigation system can include a landmark acquisition probe configured to be movably coupled to the jig assembly. In some embodiments, the landmark acquisition probe is configured to move in a plurality of degrees of freedom relative to the jig assembly. The hip joint navigation system can include a second inertial navigation device configured to determine the orientation of the landmark acquisition probe when the landmark acquisition probe is moved to touch an anatomical landmark. In some embodiments, the first inertial navigation device, the second inertial navigation device, or the first inertial navigation device and the second inertial navigation device are configured to adjust for tilt by rotating the Anterior Pelvic Plane about the inter-ASIS line to determine a reference plane. 
     In some embodiments, the second inertial device comprises a mount device configured to detachably connect the second inertial device to the landmark acquisition probe. In some embodiments, the second inertial device comprises a camera. In some embodiments, the first inertial navigation device comprises a display. In some embodiments, the second inertial navigation is configured to couple to an impactor. The hip joint navigation system can include a universal impactor adaptor comprising a coupler, wherein the second inertial navigation is configured to couple to an impactor with the adaptor. In some embodiments, the universal impactor adaptor comprises a clamp. In some embodiments, the universal impactor adaptor comprises one or more magnets. The hip joint navigation system can include an optical component. In some embodiments, the optical component is configured to couple to the jig assembly with one or more magnets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects and advantages are described below with reference to the drawings, which are intended to illustrate but not to limit the inventions. In the drawings, like reference characters denote corresponding features consistently throughout similar embodiments. 
         FIG.  1    is a perspective view of a hip navigation system applied to a patient. 
         FIG.  2    illustrates an exploded view of embodiments of a fixation base of the system of  FIG.  1   . 
         FIGS.  3 A- 3 G  illustrate various view of embodiments of a first assembly of the system of  FIG.  1   . 
         FIGS.  4 A- 4 F  illustrate various view of embodiments of a second assembly of the system of  FIG.  1   . 
         FIGS.  5 A- 5 C  illustrate various view of embodiments of an orientation sensing device of the system of  FIG.  1   . 
         FIG.  6 A  illustrates an embodiment of an optical component.  FIGS.  6 B- 6 C  illustrate an embodiment of an optical component. 
         FIG.  7    illustrates a hip navigation system. 
         FIGS.  8 A- 8 B  illustrate an embodiment of a fixation base of the system of  FIG.  7   . 
         FIG.  9    illustrates an embodiment of a first assembly of the system of  FIG.  7   . 
         FIGS.  10 A- 10 D  illustrate an embodiment of a second assembly of the system of  FIG.  7   . 
         FIG.  11    illustrates a configuration of positioning of a patient in a posterior approach. 
         FIG.  12 A  illustrates a configuration of and a manner of coupling of components of the system.  FIG.  12 B  illustrates a configuration of the system with a calibration fixture.  FIG.  12 C  illustrates embodiments of components described herein. 
         FIGS.  13 A- 13 C  illustrates the fixation base and fixation pins of the system of  FIG.  7    coupled to the pelvis. 
         FIGS.  14 A- 14 C  illustrates the assembly of the system of  FIG.  7   . 
         FIGS.  15 A- 15 C  illustrates the adjustment of the system of  FIG.  7    including the optical component of  FIG.  6 A . 
         FIG.  16    illustrates an embodiment of table registration. 
         FIGS.  17 A- 17 B  illustrate an embodiment of point registration before cup placement. 
         FIG.  18 A  illustrates an embodiment of an impactor including the orientation sensing device of  FIGS.  5 A- 5 C .  FIG.  18 A  illustrates a hip prosthesis placement system.  FIGS.  18 B- 18 D  illustrate embodiments of a universal impactor adapter. 
         FIGS.  19 A- 19 C  illustrate an embodiment of point registration after cup placement. 
         FIGS.  20 A- 20 I  illustrate embodiments of target probes. 
         FIG.  21    is an example of an x-ray that can be taken pre-operatively. 
         FIG.  22    illustrates the positioning of a patient prior to connection of the system of  FIG.  1    in an anterior approach. 
         FIG.  23    illustrates a configuration of the system of  FIG.  1    coupled with the pelvis. 
         FIG.  24    illustrates anatomy of an anterior portion of the hip joint, including the pelvis and the proximal femur. 
         FIGS.  25 A- 25 D  illustrates method steps to identify the Anterior Pelvic Plane. 
         FIGS.  26 A- 26 D  illustrates method steps to identify a table or other horizontal plane. 
         FIGS.  27 A- 27 D  illustrates method steps to calculate an Adjusted Plane. 
         FIGS.  28 A- 28 B  illustrate side views of the pelvis and the Anterior Pelvic Plane and the Adjusted Plane thereof.  FIG.  28 C  illustrates a top view of these planes.  FIGS.  28 A- 1  and  28 B- 1    are alternative views. 
         FIG.  29    illustrates a screen display of a surgical orientation device of the system of  FIG.  1   . 
         FIGS.  30 A- 30 C  illustrate a neutral and two tilt positions of the pelvis. 
         FIGS.  31 A- 31 C  illustrate a neutral and two rotation positions of the pelvis. 
     
    
    
     DETAILED DESCRIPTION 
     A variety of systems and methods are discussed below that can be used to improve outcomes for patients by increasing the likelihood of proper placement of a medical prosthesis. These systems can be focused on inertial navigation techniques to establish a reference plane. These systems can be focused on inertial navigation techniques to measure leg length and/or joint offset. 
     A. Systems for Anterior and Poster Approach 
     1. Hip Navigation System 
       FIG.  1    shows a hip navigation system  600  adapted to navigate a hip joint procedure with reference to anatomical landmarks. The system  600  is shown mounted on a pelvis in  FIG.  1   , which is shown as a box for simplicity. The system  600  can be mounted on a pelvis for a posterior approach as described herein. The system  600  can be mounted on a pelvis for an anterior approach as described herein 
     The system  600  can include a fixation base  602 , a first assembly  604 , and a second assembly  606 . The first assembly  604  is rigidly connected to the hip or pelvis in the illustrated configuration so that motion of the pelvis causes corresponding motion of sensor(s) in the first assembly  604  as discussed herein. Sensing this motion enables the system  600  to eliminate movement of the patient as a source of error in the navigation. The second assembly  606  provides a full range of controlled motion and sensor(s) that are able to track the motion, in concert with sensor(s) in the first assembly  604 . Additional details of systems, devices, sensors, and methods are set forth in U.S. application Ser. No. 10/864,085 filed Jun. 9, 2004, U.S. application Ser. No. 11/182,528 filed Jul. 15, 2009 and related to U.S. Pat. No. 8,057,479, U.S. application Ser. No. 12/557,051 filed Sep. 10, 2009 and related to U.S. publication no. 2010/0076505, U.S. application Ser. No. 12/509,388 filed Jul. 24, 2009, U.S. application Ser. No. 13/011,815 filed Jan. 21, 2011, U.S. application Ser. No. 13/115,065, filed May 24, 2011 and issued as U.S. Pat. No. 8,118,815; U.S. application Ser. No. 14/399,046 filed Nov. 5, 2014, U.S. application Ser. No. 14/401,274 filed Nov. 14, 2014, U.S. application Ser. No. 13/800,620 filed Mar. 13, 2013, U.S. application Ser. No. 14/643,864 filed Mar. 10, 2015 and U.S. application Ser. No. 15/550,564 filed Aug. 11, 2017, which are all incorporated by reference herein in their entireties for all purposes. The sensors in assemblies  604 ,  606  preferably transfer data among themselves and in some cases with external devices and monitors wirelessly, using Bluetooth, Wifi® or other standard wireless telemetry protocol. The system  600  can include one or more fixation pins  610 ,  612 . The system  600  can also include a surgical orientation device  172  and an orientation sensing device  204 , as described herein. 
     The system  600  can include the fixation base  602  shown in  FIG.  2   .  FIG.  2    shows an exploded view of the fixation base  602 . The fixation base  602  can include a platform  620  and a support  622 . The platform  620  can interact with the support  622  to function as a clamp. In the illustrated embodiment, the fixation base  602  can include one or more fixation devices  624  such as screws. The fixation devices  624  can pass through the support  622  and engage corresponding holes in the platform  620 . 
     The platform  620  and the support  622  form one or more channels therebetween. The number of channels can correspond to the number of fixation pins. Upon rotation of the fixation devices  624 , each fixation pin  610 ,  612  is retained between the platform  620  and the support  622 . The fixation base  602  can include a divot  630 . The divot  630  can be associated with a parked configuration or home position, as described herein. 
     The fixation base  602  can include a first coupler  632 . The first coupler  632  can couple to one or more components of the system  600 . The first coupler  632  can include an elongate post  635 . The first coupler  632  can include a slot  634 . The slot  634  can be designed to interact with detents of other components of the system  600 , as described herein. The first coupler  632  can include a tapered surface  636 . The tapered surface  636  can facilitate entry of the first coupler  632  within other components of the system  600 . In some embodiments, the first coupler  632  can have a regular shape (e.g., cylindrical). In some embodiments, the first coupler  632  can have an irregular shape (e.g., triangular, teardrop, elliptical, rectangular). The irregular shape may facilitate alignment of other components of the system  600  with the platform  620  of the fixation base  602 . In the illustrated embodiment, the other components of the system  600  can mate with the first coupler  632  in a single orientation. 
     The system  600  can include the first assembly  604  shown in  FIGS.  3 A- 3 G . The first assembly  604  can include a pelvic bracket  638 . In the illustrated embodiment, the pelvic bracket  638  can be substantially vertical in use, as shown in  FIG.  1   . The first assembly  604  can be designed to couple with the fixation base  602 . The first assembly  604  can include a lock lever  640  to couple the first assembly  604  with the fixation base  602 . In some embodiments, the tapered surface  636  of the first coupler  632  causes the pivoting of the lock lever  640 . In some embodiment, the surgeon causes the pivoting of the lock lever  640 . The lock lever  640  can include a detent  642 . The detent  642  is sized and shaped to be received within the slot  634 . The engagement of the detent  642  and the slot  634  can rigidly couple the first assembly  604  with the fixation base  602 . 
     The first assembly  604  can include an extension  644 . The extension  644  can be coupled to the pelvic bracket  638 . The extension  644  can include a second coupler  648 . The second coupler  648  can be designed to couple with the second assembly  606 . The second coupler  648  provides a stable manner to position the second assembly  606  relative to the first assembly  604 . 
     The extension  644  can include a mount  646  designed to couple with a surgical orientation device  172 . The surgical orientation device  172  is rigidly coupled to the extension  644  when engaged with the mount  646 . The surgical orientation device  172  can be angled when coupled to the first assembly  604 , as shown in  FIG.  1   . The surgical orientation device  172  can be angled approximately 35° from the horizontal axis. Other angles from the horizontal axis are contemplated, (e.g., 5°, 10°, 15°, 20°, 25°, 30°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, or 85°, between 30°-40°, between 25°-45°). In some embodiments, the angle of the surgical orientation device  172  improves visibility. The angle is a compromise between tilting the surgical orientation device  172  up toward the surgeon and allowing another surgeon or surgical assistant on the other side of the patient to still see the display. One reason for angling the surgical orientation device  172  is that in an anterior approach, the surgeon stands toward the patient&#39;s feet while impacting the acetabular implant and a horizontal display may be difficult to see. 
     The surgical orientation device  172  detects orientation and rotation of the device  172  relative to a reference frame. The surgical orientation device  172  preferably comprises at least one sourceless sensor, such as an accelerometer, a gyroscope, or a combination of these sensors and other sensors. In some embodiments, the surgical orientation device  172  includes a three axis accelerometer to detect orientation relative to gravity and a plurality of gyroscopes to detect rotation. Other sensors could be used in various modifications. Examples of specific sensor combinations include Analog Devices ADIS 16445 and Invensense MPU-6050 or MPU-9150 among others. In some approaches, the surgical orientation device  172  can be disposable and so the sensors preferably are less expensive sensors. In some embodiments, the surgical orientation device  172  is disposable. 
     The surgical orientation device  172  includes one or more sensors that together form an inertial measurement unit (IMU). In particular, the IMU can include a first sensor for determining acceleration and a second sensor for determining gyroscopic positioning. As discussed herein, the first sensor can be an accelerometer and the second sensor can be a gyroscopic sensor. In some embodiments, the sensors can comprise a three-axis gyroscopic sensor and a three-axis accelerometer sensor. The surgical orientation device  172  can include a transmitter for sending data or receiving data from one or more sensors of the system  600 , such as one or more sensors of the orientation sensing device  204 . The information received from the orientation sensing device  204  can be fed to an input port, or alternatively, the electronic control unit can itself receive the information (e.g., wirelessly). The information from the orientation sensing device  204  can correspond, for example, to the position and/or orientation of the orientation sensing device  204  and can be used by the surgical orientation device  172  to determine an aggregate, or overall, position and/or orientation of the surgical orientation device  172 . 
     The system  600  can include the second assembly  606  shown in  FIG.  4 A- 4 F . The second assembly  606  can include a probe bracket  652 . In the illustrated embodiment, the probe bracket  652  can be substantially angled with respect to the pelvic bracket  638  when in use, as shown in  FIG.  1   . The second assembly  606  can be designed to couple with the second coupler  648  of the first assembly  604 . The second assembly  606  can include a lock lever  654 . The lock lever  654  can be coupled to the probe bracket  652  with pivot pins. The lock lever  654  can be pivoted relative to the probe bracket  652 . In some embodiments, the tapered surface of the second coupler  648  causes the pivoting of the lock lever  654 . In some embodiments, the surgeon causes the pivoting of the lock lever  654 . The lock lever  654  can include a detent  656 . The detent  656  is sized and shaped to be received within the slot of the second coupler  648 . The engagement of the detent  656  and the slot can rigidly couple the second assembly  606  with the first assembly  604 . 
     In the illustrated embodiment, the second assembly  606  includes a mount  658 . The mount  658  can be coupled to the probe bracket  652  to allow relative movement therebetween. The mount  658  can be received within an opening in the probe bracket  652 . The mount  658  can permit rotation about a longitudinal axis of the mount  658  relative to the probe bracket  652 . 
     The second assembly  606  can include a dock  662 . The dock  662  can be coupled to the mount  658  to allow relative movement therebetween. The dock  662  can be coupled to the mount  658  with one or more pivot pins  660 . The dock  662  can have two degrees of freedom relative to the probe bracket  652  (e.g., rotational motion and pivoting motion). The dock  662  can include a sliding support with a through lumen  664 . The through lumen  664  is sized to accept a probe  678 . The probe  678  has a distal end  680  designed to touch a point or a location or locations, as described herein. The distal end  680  can be straight as shown in  FIG.  4 A . In other embodiments, the distal end  680  is slanted or curved. 
     The through lumen  664  of the dock  662  permits slideable extension of the probe  678 . The dock  662  is movable relative to the probe bracket  652  (e.g., via rotation of the mount  658  and pivoting of the pivot pin  660 ). The dock  662  can be rotated about a longitudinal axis of the mount  658  to different rotational positions relative to the attachment location of the fixation pins  610 ,  612 . This may require movement of the mount  658  in a rotational manner relative to the probe bracket  652 . The dock  662  can be pivoted about the longitudinal axis of the pivot pins  660  to different positions relative to the attachment location of the fixation pins  610 ,  612 . This may require movement of the dock  662  in a pivoting manner relative to the mount  658 . 
     The probe  678  can be coupled to the dock  662  such that the probe  678  is movable relative to the probe bracket  652  (e.g., via rotation of the mount  658  and pivoting of the pivot pin  660 ). This maneuverability enables the distal end  680  of the probe  678  to pivot or rotate to contact anatomical landmarks, as discussed herein. The probe  678  can be slid relative to the dock  662  to different translational positions relative to the attachment location of the fixation pins  610 ,  612 . The slideability of the probe  678  within the dock  662  enables the distal end  680  to move to reach a point or anatomical landmarks in the same plane of the probe  678  but closer to or farther from the distal end  680 . 
     The second assembly  606  permits a range of motion of a distal end  680  of the probe  678  to facilitate acquiring a point that that is spaced apart from the attachment location of the fixation pins  610 ,  612 . The second assembly  606  permits a range of motion of a distal end  680  of the probe  678  to facilitate acquiring a plurality of landmarks that are different distances from the attachment location of the fixation pins  610 ,  612 . In other words, the distal end  680  of the probe  678  can be extended away from the axis of the sliding support of the dock  662  or can be retracted to a position closer to the axis of the sliding support of the dock  662 . 
     The dock  662  can include a third coupler  668 . In some embodiments, the third coupler  668  is a universal coupler. In some embodiments, the third coupler  668  is identical or substantially similar to the second coupler  648 . This permits the orientation sensing device  204  to couple to either the second coupler  648  or the third coupler  668 , as described herein. In some embodiments, the third coupler  668  can be substantially similar to the first coupler  632  described herein. The third coupler  668  can be designed to couple with the orientation sensing device  204 .  FIG.  5 A- 5 C  illustrate an embodiment of the orientation sensing device  204 . The second assembly  606  can include an extension  670 . The extension  670  can couple to the third coupler  668  of the dock  662 . The engagement between the third coupler  668  and the extension  670  minimizes or prevents relative movement therebetween to avoid any mechanical relative movement during navigation procedures. The extension  670  can include a mount  672  designed to couple with the orientation sensing device  204 . In the illustrated embodiment, the mount  672  includes a lock and release lever that can pivot relative to the extension  670 . The orientation sensing device  204  can include features to mate with the lock and release lever. Other configurations are contemplated. The orientation sensing device  204  is rigidly coupled to the extension  670  when engaged with the mount  672 . 
     The orientation sensing device  204  can be angled when coupled to the second assembly  606 , as shown in  FIG.  1   . The orientation sensing device  204  can be angled approximately 35° from the horizontal axis. Other angles from the horizontal axis are contemplated, (e.g., 5°, 10°, 15°, 20°, 25°, 30°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, or 85°, between 30°-40°, between 25°-45°). In some embodiments, the angle of the orientation sensing device  204  improves visibility. 
     The orientation sensing device  204  detects orientation and rotation of the probe  678 , as described herein. The orientation sensing device  204  preferably comprises at least one sourceless sensor, such as an accelerometer, a gyroscope, or a combination of these sensors and other sensors. In some embodiments, the orientation sensing device  204  includes a three axis accelerometer to detect orientation relative to gravity and a plurality of gyroscopes to detect rotation. Other sensors could be used in various modifications. In some embodiments, the orientation sensing device  204  is reusable. 
     Referring back to  FIGS.  4 A and  4 C , the probe  678  can include a marking  682 . The marking  682  can indicate length or extension of the probe  678  relative to the dock  662 . The marking  682  can include a scale. In some embodiments, the marking  682  can be over a range of from about 8 inches, 10 inches, 12 inches, approximately 8-12 inches, etc. The marking  682  can be printed on the probe  678 . In some embodiments, the marking  682  can be on a separate component such as a probe inlay  676 . The probe inlay  676  can be received within a portion of the probe  678 . In some embodiments, the probe inlay  676  is separated a distance from the distal end  680  of the probe  678 . 
     Referring to  FIG.  5 A- 5 C , the orientation sensing device  204  can include a camera  184 . The camera  184  can capture images of the marking  682 . In some embodiments, the dock  662  includes a window to permit the camera  184  to capture images. The camera  184  can read the marking  682  to provide accurate determination of the translational position of the probe  678  relative to the dock  662 . In another embodiment, camera data derived from the marking  682  can be used to confirm the data from sensors in the orientation sensing device  204 . 
     2. Optical Component 
     In some methods of use, the system  600  includes an optical component  174  shown in  FIG.  6 A . In some embodiments, the optical component  174  is integrated into the surgical orientation device. In some embodiments, the optical component  174  can be a separate component from the surgical orientation device  172 . The optical component  174  can be located below the surgical orientation device  172  adjacent to a fixture to be coupled with a patient, e.g., closer to the pelvis of the patient. The optical component  174  can be located beside or adjacent to or above the surgical orientation device  172 . The display of the surgical orientation device  172  can include instructions related to the method of using the optical component  174 . 
     In some embodiments, the optical component  174  can include a housing. The optical component  174  can include one or more light sources within the housing of the optical component  174 . The optical component  174  can include one or more windows which allow light to project outward from the optical component  174 . The optical component  174  can include one or more additional optical components such as one or more lens, one or more reflectors, one or more filters, one or more diffractor, and/or one or more diffusors. The optical component  174  can include one or energy sources to supply energy to the light source. The optical component  174  can include any features of the surgical orientation device  172  and/or the orientation sensing device  204  described herein. 
     In some embodiments, the optical component  174  is coupled to the system  600 . In some embodiments, the optical component  174  is coupled to the first assembly  604 . In some embodiments, the optical component  174  can be rotated, pivoted, or otherwise moved relative to the first assembly  604 . The system  600  can include additional features to facilitate positioning of the optical component  174  relative to the first assembly  604 . The optical component  174  can include a bracket  176 . The bracket  176  can facilitate connection between the optical component  174  and another component of the system  600 . In some embodiments, the bracket  176  can be a housing for the laser or other light source, described herein. The optical component  174  can include one or more features to allow the independent adjustment of the optical component  174 . The optical component  174  can include an adjustment feature  178 . The adjustment feature  178  can cause the rotation of the optical component  174  relative to the first assembly  604 . The adjustment feature  178  can cause the rotation of the optical component  174  relative to the second assembly  606 . The adjustment feature  178  can cause the rotation of the optical component  174  relative to the fixation base  602 . The adjustment feature  178  can cause the rotation of the optical component  174  relative to the pelvis. The adjustment feature  178  can be a knob. The adjustment feature  178  can be coupled to an axle to cause rotation of the optical component  174  about the axle. The adjustment feature  178  can be coupled to the bracket  176  to cause rotation of the bracket  176 . The bracket  176  can include a sleeve or tubular portion designed to fit around an axle of the adjustment feature  178 . In some embodiments, the optical component  174  is coupled independently to the bone of the patient. The optical component  174  can be coupled to the pelvis. Other configurations of the optical component are contemplated, see  FIG.  12 C . 
       FIGS.  6 B- 6 C  illustrate another embodiment of an optical component  194 . The optical component  194  can include one or more magnets  196 . The one or more magnets  196  can be located on a surface of the optical component  194 . The one or more magnets  196  can be disposed in or on a housing  200  of the optical component  194 . In some embodiments, the optical component  194  can include one magnet, two magnets, three magnets, four magnets, etc. In some embodiments, the optical component  194  can include one or more magnets on a first surface  202  and one or more magnets on a second surface  204 . The first surface  202  can be located on an opposite side as the second surface. In some embodiments, the optical component  194  can include one or more magnets on opposite sides of the optical component  194 . In some embodiments, the one or more magnets  196  on opposite sides of the optical component  194  can allow the optical component  194  to be coupled with another component of any of the systems disclosed herein on either side of the optical component  194 . 
     In some embodiments, the optical component  194  is coupled to the system  600 . In some embodiments, the optical component  194  is coupled to the first assembly  604 . In some embodiments, the first assembly  604  can include one or more magnets  198 . The one or more magnets  198  can be located on a surface of the first assembly  604 . The one or more magnets  198  can be disposed in or on an outer flat surface of the first assembly  604 . In some embodiments, the first assembly  604  can include one magnet, two magnets, three magnets, four magnets, etc. In some embodiments, the first assembly  604  includes one or more magnets  198  on a first surface and one or more magnets  198  on a second surface. In some embodiments, the first assembly  604  can include one or more magnets on opposite sides of the first assembly  604 . In some embodiments, the optical component  194  can couple to either side of the first assembly  604 . The one or more magnets  198  of the first assembly  604  can correspond in number, size, shape and/or pattern to the one or more magnets  196  of the optical component  194 . The one or more magnets  196  of the optical component  194  can be configured to attract and couple to the one or more magnets  198  of the first assembly  604 . In some embodiments, the first assembly  604 , or a portion thereof, comprises a magnetic material. In some embodiments, the entire first assembly  604  is magnetic. In some embodiments one or more magnets  198  can be configured to attract a magnetic material disposed on or in the housing of the optical component  194 . Accordingly, magnets may be positioned in or on the optical component  194 , in or on the first assembly  604 , or on or in both the component  194  and the assembly  604 . 
     In some embodiments, the optical component  194  can be held in position relative to the first assembly  604  with the one or more magnets  196 ,  198 . In some embodiments, the optical component  194  can be removably coupled and decoupled from the system  600 . In some embodiments, the optical component  194  can allow for independent rotational adjustment of the optical component  194  relative to the system  600 . In some embodiments, the optical component  194  can connect to the system  600  in a single orientation. In some embodiments, the optical component  194  can connect to the system  600  in one of a plurality of orientations. In some embodiments, the optical component  194  can connect to the system  600  on either side of the first assembly  604 . As described herein, the optical component  194  can include one or more magnets  196  on opposite sides of the optical component  194 . The first assembly  604  can include one or more magnets  198  or magnetic surfaces on opposite sides of the first assembly  604 . 
     In some embodiments, the optical component  194  and the first assembly  604  can include one or more mounting features  190 ,  192 . The mounting features  190 ,  192  can include one or more recesses  190  and one or more protrusions  192 . In some embodiments, the first assembly  604  can include one or more protrusions  192  and the optical component  194  can include one or more corresponding recesses  190 . In some embodiments, the first assembly  604  can include two protrusions  192  and the optical component  194  can include two or more recesses  190 . In the illustrated embodiment, the first assembly  604  includes two protrusions  192  and the optical component  194  includes three recesses  190 . The two protrusions  192  can engage two of the recesses  190  in a first configuration and two of the recesses in a second configuration. In embodiments, including three recesses  190  and two protrusions  192 , one of the recesses  190  is engaged in both the first and second configurations. The first configuration and the second configuration can tilt the optical component  194  relative to the first assembly  604 . Other configurations are contemplated (e.g., one protrusion, two protrusions, three protrusions, four protrusions, etc.) and (e.g., one recess, two recesses, three recesses, four recesses, five recesses, six recesses, etc.). In some embodiments, there are more recesses  190  than protrusions  192 . The mounting features  190 ,  192  can reduce or limit rotation between the optical component  194  and the first assembly  604 . The mounting features  190 ,  192  can facilitate alignment between the optical component  194  and the first assembly  604 . The mounting features  190 ,  192  can facilitate the connection between the optical component  194  and the first assembly  604 . The one or more magnets  196  of the optical component  194  can allow for quicker and simpler attachment to the system  600 . The one or more magnets  196  of the optical component  194  can allow for a magnetic snap-on connection. In other embodiments the polarity of the magnets  196  and/or the magnets  198  can be configured such that only one or only two relative positions of the optical component  194  and the assembly  604  result in attraction and magnetic securement therebetween. Other types of connections between the optical components and the systems described herein are contemplated. 
     In some embodiments, the optical component  174 ,  194  can be positioned at any one of a plurality of discrete positions relative to the first assembly  604 . For instance, the system  600  can include a plurality of splines between the optical component  174 ,  194  and an adjacent structure. The plurality of splines can be a serrated plate. The adjacent structure can be coupled to the first assembly  604 . The plurality of splines can retain the position of the optical component  174 ,  194  relative to the first assembly  604 . In some embodiments, the optical component  174 ,  194  can be oriented at an infinite number of positions relative to the first assembly  604 . In some embodiments, the optical component  174 ,  194  can be oriented at a select position along a continuum of motion. In some embodiments, the optical component  174 ,  194  can be oriented at one discrete position or orientation relative to the first assembly  604 . In some embodiments, the optical component  174 ,  194  can be oriented at two discrete positions or orientations relative to the first assembly  604 . In some embodiments, the optical component  174 ,  194  can be oriented at one discrete position or orientation on each side of the first assembly  604 . In some embodiments, the optical component  174 ,  194  can be oriented at a plurality of discrete positions or orientations relative to the first assembly  604 . The connection between the optical component  174 ,  194  and the first assembly  604  is sufficiently rigid to maintain the position of the optical component  174 ,  194  relative to the first assembly  604  once moved into position. 
     As described herein, in some methods of use, the optical component  174 ,  194  is mounted to the pelvis of the patient. In some embodiments, the optical component  174 ,  194  can be mounted to any component of the system  600 . In some embodiments, the optical component  174 ,  194  can be mounted to the platform  602 . In some embodiments, the optical component  174 ,  194  can be mounted to the first assembly  604 . In some embodiments, the optical component  174 ,  194  can be separately mounted to the pelvis. In some methods of use, the optical component  174 ,  194  can be independently mounted to the pelvis of the patient. In some methods of use, the optical component  174 ,  194  can be spaced apart from the system  600 . In some methods of use, the optical component  174 ,  194  can be fixed in position relative to the pelvis during the surgical procedure. In some methods of use, the optical component  174 ,  194  can project light from the same position during the surgical procedure. The rigidity of the system  600  can secure the position of the optical component  174 ,  194  once moved into position. In some methods of use, the optical component  174 ,  194  can be positioned and/or moved until the optical component  174 ,  194  projects light on a selected portion of the anatomy. In some methods of use, the optical component  174 ,  194  can be positioned and/or moved until the optical component  174 ,  194  projects light on a target probe, as described herein. In some methods of use, the optical component  174 ,  194  can be positioned and/or moved until the optical component  174 ,  194  projects light on sterile wrap, medical drape, bandage, tape, and/or other instruments. In some methods of use, the optical component  174 ,  194  can be positioned and/or moved until the optical component  174 ,  194  projects light on a device coupled to the anatomy. In some methods of use, the optical component  174 ,  194  can be positioned and/or moved until the optical component  174 ,  194  projects light on a device placed near the anatomy, as described herein. 
     The optical component  174 ,  194  can emit a pattern of light. Examples of patterns of lights include one or more lines, one or more points, one or more plane, or one or more shapes. The optical component  174 ,  194  can be moved until the light is projected on at least one anatomical region. In some methods of use, the light is projected onto at least one anatomical region with little soft tissue. The soft tissue may move relative to the underlying bone. The surgeon can select locations to illuminate where the skin is close to the underlying bone. In some methods of use, the optical component  174 ,  194  can project a pattern onto a portion of the anatomy. In some methods of use, the optical component  174 ,  194  can project a pattern onto a target coupled to the anatomy. The surgeon can complete any method steps described herein. Thereafter, the optical component  174 ,  194  can project the same pattern on the selected portion of the anatomy. 
     In some embodiments, the optical component  174 ,  194  can project light onto an anatomical surface. In some embodiments, the optical component  174 ,  194  can project light onto an anatomical feature or landmark. The light can illuminate a portion of the femur. The light can illuminate a portion of the knee joint. The light can illuminate a portion of the tibia. The light can illuminate can illuminate a portion of the ankle. The light can illuminate a portion of the foot. The light can illuminate a portion of the foot constrained within a positioning boot. In some embodiments, the light can be projected onto a flat or substantially flat local area. In some embodiments, the light can be projected onto a curved or substantially curved local area. In some methods of use, the shape of the surface does alter the projection of light, e.g., changes in angle, tilt, shape, etc. In some methods of use, the shape of the surface does not alter the projection of light. In some methods of use, the shape of the surface does not alter the utility of the approach, as described herein. 
     In this context, optical component is a broad term. The optical component  174 ,  194  can be any device designed to project light including visible, ultraviolet, and infrared light. The optical component  174 ,  194  can comprise one or more lasers, which can be configured to project laser light. The laser can emit light with a very narrow spectrum, for instance a single color of light. The optical component  174 ,  194  can focus light on a single location, such as a point. The optical component  174 ,  194  can focus light along a line. The optical component  174 ,  194  can project one or more points, one or more lines, one or more planes, one or more shapes, one or more colors, and/or one or more patterns. In some embodiments, the projection of light when incident on a surface is visible as two intersecting lines, the pattern may be referred to herein as a cross-hair. 
     The optical component  174 ,  194  can be positioned to project light toward a desired location. The optical component  174 ,  194  can provide a visual guide to replicate an original position of an anatomical feature relative to another anatomical feature, as described herein. In methods wherein the optical component  174 ,  194  is mounted to the pelvis, the optical component  174 ,  194  can provide a visual guide to replicate the original position of the leg or a portion thereof relative to the hip. In some embodiments, the optical component  174 ,  194  can provide a visual guide to replicate the original position of the femur relative to the pelvis as described herein. The optical component  174 ,  194  can provide alternative or additional orientation information to a surgeon regarding the position on the pelvis relative to the femur. In methods wherein the optical component  174 ,  194  is mounted to the pelvis, the optical component  174 ,  194  can provide a visual guide to replicate the original orientation of the leg or a portion thereof relative to the hip. In some embodiments, the optical component  174 ,  194  can provide a visual guide to replicate the original orientation of the femur relative to the pelvis as described herein. The optical component  174 ,  194  can provide alternative or additional orientation information to a surgeon regarding the orientation on the pelvis relative to the femur. 
     The optical component  174 ,  194  can be used to perform one or more methods or method steps. In some methods of use, the optical component  174 ,  194  can project the pattern of light pre-operatively. In some methods of use, the optical component  174 ,  194  can project the pattern of light before cup placement. In some methods of use, the optical component  174 ,  194  can project the pattern of light before joint replacement. In some methods of use, the optical component  174 ,  194  can project the pattern of light before joint dislocation. In some methods of use, the optical component  174 ,  194  can project the pattern of light that can be traced. In some methods of use, the optical component  174 ,  194  can project the pattern of light after cup placement. In some methods of use, the optical component  174 ,  194  can project the pattern of light post-instrumentation. In some methods of use, the optical component  174 ,  194  can project the pattern of light that can align with a marking as the femur is moved. In some methods of use, the optical component  174 ,  194  can project the pattern of light onto the same surface before and after the cup is replaced. In some methods of use, the optical component  174 ,  194  can project the pattern of light onto the same surface intra-operatively. In some methods of use, the optical component  174 ,  194  can project the pattern of light onto the same surface intra-operatively at two or more times during the procedure. 
     3. Alternative Hip Navigation System 
       FIG.  7    illustrates a hip navigation system  700 .  FIGS.  8 A- 8 B  illustrate an embodiment of a fixation base  702  of the system  700  of  FIG.  7   .  FIG.  9    illustrates an embodiment of a first assembly  704  of the system  700  of  FIG.  7   .  FIGS.  10 A- 10 D  illustrate an embodiment of a second assembly  706  of the system  700  of  FIG.  7   . 
     The system  700  can include any of the features described herein with respect to system  600 . Similar elements are provided with similar reference numbers. The system  700  can include a fixation base  702 , a first assembly  704 , and a second assembly  706 . The system  700  can include the surgical orientation device  172  and the orientation sensing device  204 . The orientation sensing device  204  can include a camera  184  as shown in  FIG.  5 A . The system  700  can include an optical component  174  as shown in  FIG.  6 A  and/or the optical component  194  shown in  FIGS.  6 B- 6 C . The optical component  174  can include one or more of the following features: a bracket  176  and an adjustment feature  178  (see  FIG.  6 A ). The optical component  194  can include one or more of the following features: one or more magnets  196  and one or more mounting features  190 ,  192  (see  FIGS.  6 B- 6 C ). 
     Referring to  FIGS.  8 A- 8 B , the fixation base  702  can include one or more of the following: a platform  720 , a support  722 , one or more fixation devices  724 , a divot  730 , and a first coupler  732  with a slot  734  and a tapered surface  736 . The system  700  can include one or more fixation pins, such as a fixation pin  710  and a fixation pin  712  (see  FIGS.  13 A- 13 C ). 
     Referring to  FIG.  9   , the first assembly  704  can include one or more of the following: a pelvic bracket  738 , a lock lever  740 , a detent  742  sized and shaped to be received within the slot  734  (see  FIG.  3 A  for similar detent  642 ), an extension  744 , a second coupler  748  and a mount  746  designed to couple with a surgical orientation device  172 . 
     Referring to  FIGS.  10 A- 10 B , the second assembly  706  can include one or more of the following: a probe bracket  752 , a lock lever  754 , a detent  756  (see  FIG.  4 A  for similar detent  656 ), a mount  758  to permit rotation about a longitudinal axis of the mount  758  relative to the probe bracket  752 , a dock  762  coupled to the mount  758 , a through lumen  764  sized to accept a probe  778 , a third coupler  768 , an extension  770  (see  FIG.  7   ), and a mount  772  (see  FIG.  7   ). The orientation sensing device  204  can couple to either the second coupler  748  or the third coupler  768 . Referring to  FIGS.  10 C- 10 D , the system  700  can include the probe  778 . The probe  778  can include one or more of the following: a distal end  780  designed to touch a point, a marking  782 , and a probe inlay  776 . 
     The system  700  can include additional features from the system  600  described herein. The system  600  can include one or more of these additional features. Referring back to  FIGS.  8 A- 8 B , the platform  720  can include an articulation  726 . The articulation  726  can allow movement between the platform  720  and the first assembly  704 . The articulation  726  can form a ball and socket joint with the platform  720 . The articulation  726  can include a head  728 . The head  728  can interact with the platform  720  to form a joint. In the illustrated embodiment, the platform  720  includes the socket. 
     The articulation  726  can include the first coupler  732 . The first coupler  732  can couple to one or more components of the system  700 . In some embodiments, the first coupler  732  is a universal coupler. The first coupler  732  can include an elongate post  735 . In some embodiments, the first coupler  732  can have a regular shape (e.g., cylindrical). In some embodiments, the first coupler  732  can have an irregular shape (e.g., triangular, teardrop, elliptical, rectangular). The irregular shape may facilitate alignment of other components of the system  700  with the platform  720  of the fixation base  702 . In the illustrated embodiment, the other components of the system  700  can mate with the first coupler  732  in a single orientation. The articulation  726  can include the divot  730 . The divot  730  can be associated with a parked configuration or home position, as described herein. 
     The fixation base  702  can include the platform  720  and the support  722 . The platform  720  can interact with the support  722  to function as a clamp. In the illustrated embodiment, the fixation base  702  can include one or more fixation devices  724 . In the illustrated embodiment, fixation base  702  includes two fixation devices  724 . The fixation devices  724  can pass through the support  722  and engage corresponding holes in the platform  720 . Upon advancement of the fixation devices  724 , each fixation pin  710 ,  712  is clamped between the platform  720  and the support  722 . In some embodiments, the fixation devices  724  are screws, but other configurations are contemplated to clamp the platform  720  and the support  722 . 
     The articulation  726  can be locked in position. The fixation base  702  can include a lock  727 . The lock  727  can be advanced against the head  728  to reduce, limit, or prevent movement of the articulation  726 . The lock  727  can include fastener such as a screw. In some embodiments, the lock  727  can include a contacting surface  729 . The fastener can be rotated or translated to advance the contacting surface  729  relative to the platform  720 . The contacting surface  729  can be moved away from the head  728  to enable the head  728  to articulate with the platform  720 . The contacting surface  729  can be moved toward the head  728  to apply a force or pressure on the head  728 . The contacting surface  729  can be moved toward the head  728  push the head  728  against a surface of the platform  720 . The force or pressure of the contacting surface of the lock  727  against the head  728  can reduce movement of the head  728 . Other configuration to reduce or prevent movement of the joint are contemplated. 
     The articulation  726  is illustrated as a ball and socket joint. The articulation  726  can be any joint known in the art. The articulation  726  can include an axle, a sleeve, a bearing, a bushing, and/or a swivel. The articulation  726  can be any joint or connection that allows motion about one or more planes or axes. The articulation  726  can be sufficiently rigid to maintain the position of the first assembly  704  relative to the platform  720  once moved into position. Other configurations are contemplated. 
     In some methods of use, the fixation base  702  is mounted to the pelvis, as described herein. The position of the pelvic bracket  738  of the first assembly  704  can be adjusted via the articulation  726 . The position of the extension  744  of the first assembly  604  can be adjusted via the articulation  726 . The optical component  174 ,  194  can be coupled to the first assembly  604  as described herein. The position of the optical component  174 ,  194  can be adjusted via the articulation  726 . In some embodiments, the position of the optical component  174 ,  194  is determined in part by the position of the articulation  726 . The system  700  can have additional features to position of the optical component  174 ,  194 , as described herein. In other embodiments, the position of the optical component  174 ,  194  is determined entirely by the position of the articulation  726 . 
     Referring now to  FIGS.  10 A- 10 D , the second assembly  706 , or a portion thereof such as the probe  778 , can be easily removed when not in use. The distal end  780  of the probe  778  can be angled, bent or curved to facilitate acquiring a point. The distal end  780  of the probe  778  can be bent or curved to reach the home position. The shape of the probe  778  can facilitate the touching of a point or structure in the posterior approach. In some embodiments, the probe  778  comprises two or more components. In some embodiments, the distal end  680  is removable. 
     The second assembly  706  can include a dock  762 . The dock  762  can be coupled to the mount  758  to allow relative pivotal movement therebetween. For instance, the dock  662  can be coupled to the mount  758  with one or more pivot pins  760 . The dock  762  can have two degrees of freedom relative to the probe bracket  752  (e.g., rotational motion and pivoting motion). The dock  762  can include a sliding support with a through lumen  764 . The through lumen  764  is sized to accept a probe  778 . The probe  778  has a distal end  780  designed to touch a point, as described herein. The distal end  780  can be slanted or curved. This maneuverability enables the distal end  780  of the probe  778  to pivot, rotate, or slide to contact a point, as discussed herein. 
     The through lumen  764  of the dock  762  permits slideable extension of the probe  778 . The probe  778  can slide relative to the dock  762  to different translational positions relative to the attachment location of the fixation pins  710 ,  712 . The slideability of the probe  778  within the dock  762  enables the distal end  780  to move to reach a point in the which is offset from the plane of the probe  778  but closer to or farther from the distal end  780 . 
     The second assembly  706  can include a lock  766 . The lock  766  can be advanced against the probe  778  to reduce, limit, or prevent movement of the probe  778 . The lock  766  can include fastener such as a screw. In some embodiments, the lock  766  includes a contacting surface  767 . In some embodiments, the contacting surface  767  can be the end of the fastener. The fastener can be rotated or translated to advance the contacting surface  767  relative to the dock  762 . The contacting surface  767  can be moved away from the probe  778  to enable the probe  778  to slide within the dock  762 . The contacting surface  767  can be moved toward the probe  778  to apply a force or pressure on the probe  778 . The contacting surface  767  can be moved toward the probe  778  push the probe  778  against a surface of the dock  762 . The force or pressure of the contacting surface  767  of the lock  766  against the probe  778  can reduce movement of the probe  778 . The lock  766  can limit or reduce slidablility of the probe  778  relative to the dock  762 . In some methods of use, the probe  778  can still pivot (e.g., pivotal motion between the dock  762  and the mount  758 ). In some methods of use, the probe  778  can still rotate (e.g., rotational motion between the mount  758  and the probe bracket  752 ). The lock  766  can reduce slidability when the point is registered, as described herein. 
     The system  700  can be utilized in the posterior approach as described herein. The system  700  can be utilized in the anterior approach as described herein. 
     B. Navigation for Cup Placement with Posterior Approach 
     1. Methods for Posterior Approach 
       FIGS.  1 - 10 D  illustrate hip navigation systems  600 ,  700  adapted to navigate a hip joint procedure from a posterior approach. While the method is described with respect to system  700 , any systems described herein or in the following publications can be utilized: U.S. Pat. Pub. No. 2016/0242934, filed Mar. 10, 2015; U.S. Pat. Pub. No. 2014/0052149 filed Mar. 13, 2013; U.S. Pat. Pub. No. 2010/0137871 filed Sep. 10, 2009, all of which are incorporated by reference in their entirety. 
     In some methods of cup placement in total hip arthroplasty, the inclination and anteversion angles are with respect to the Anterior Pelvic Plane (defined as a plane created by the two anterior superior iliac spines (ASIS) and the pubic symphysis). While these anatomical features are visible/palpable while the patient is in a supine position, the majority of total hip replacements are accomplished via a posterolateral approach with the patient in some variation of a lateral position, in which most of these landmarks are not accessible or visible. Historically, navigation for posterior approach hip replacement has been accomplished by registering the anatomical features of the Anterior Pelvic Plane with the patient first in a supine position and, once this plane is recorded by the navigation computer, moving the patient to a lateral position in order to perform hip surgery—with navigation performed with respect to the directly registered Anterior Pelvic Plane. This approach to hip navigation is sub-optimal for surgical workflow because the extra movement of the patient from supine to lateral position takes more surgeon and staff time and requires breaking sterility and re-draping. This is one of the key reasons why hip navigation has failed to be adopted by most of the market. 
     Additionally, altered leg length is a common patient complaint arising from hip replacement surgery and has been a common cause of medical malpractice lawsuits that arise from hip replacement. Because part of the hip replacement procedure requires precise measurements of patient leg length and joint off-set that are frequently difficult to visualize utilizing conventional instrumentation, there are opportunities to improve the surgeon&#39;s performance of these measurements using computer technology. 
     Most hip replacement procedures presently are performed from a posterior approach. In this approach, the patient is positioned on his/her side and the anterior pelvic plane is oriented vertically, e.g., perpendicular to the plane of the table on which the patient is positioned. Most surgeons performing hip replacement are very familiar with this approach and will immediately recognize the benefit of enhanced certainty about the orientation of the relevant anatomy when the patient is in this position. 
     As discussed herein, the method of use can include using the probe  778  and the sensor  204  to estimate a horizontal plane of the surgical table upon which the patient is resting. As discussed herein, the method of use can include using the probe  778  and the sensor  204  to estimate a vertical plane utilizing a measurement of gravity. The system  700  can establish a reference frame for guiding the placement of the cup without registering landmarks. The system  700  can measure leg length and/or joint offset within the established reference frame. 
       FIG.  11    shows an embodiment of the patient positioning for the posterior hip approach. In the posterior hip approach, the patient can be placed on their side. In some methods of use, the patient can be placed in the lateral decubitus position. When positioning patient prior to surgery, the surgeon can align the anterior pelvic landmarks (both ASIS&#39;s and pubic tubercle) in a vertical plane parallel to the long edge of the operating table. In some methods of use, when positioning patient prior to surgery, the surgeon can align the anterior pelvic landmarks (both ASIS&#39;s and pubic tubercle) in a vertical plane perpendicular to a surface of the table. In some methods of use, when positioning patient prior to surgery, the surgeon can align the anterior pelvic landmarks (both ASIS&#39;s and pubic tubercle) in a vertical plane parallel to gravity. In some methods of use, when positioning patient prior to surgery, the surgeon can align Anterior Pelvic Plane parallel to gravity. In some methods of use, when positioning patient prior to surgery, the surgeon can align Anterior Pelvic Plane vertically. The surgeon can ensure that pelvis is securely held by an appropriate positioning device such as a peg board or vise-type patient positioner. The surgeon can verify that patient is positioned in an appropriate position for the posterior approach. Correct patient positioning is important for accurate navigation. In some methods of use, the system  700  calculates cup angles based on the assumption that the pelvis is accurately positioned during table registration. In some methods of use, the system  700  calculates cup angles based on the assumption that the Anterior Pelvic Plane is vertical during the posterior procedure. 
     The surgical orientation device  172  and the orientation sensing device  204  can be turned on before the procedure begins. If the system can be used in a knee or hip procedure, one method can involve a surgeon selecting a module corresponding to the hip. If the system can be used in a posterior or anterior approach, one method can involve a surgeon selecting a module corresponding to the posterior approach. The surgical orientation device  172  can include a display screen. The surgical orientation device  172  can include a user interface, such as buttons which can be depressed by the user. The display screen can confirm the communication between the surgical orientation device  172  and the orientation sensing device  204 . 
     The system  700  can be partially assembled for calibration. While the system  600  is shown in  FIG.  12 A , the system  700  can be similarly coupled. In some embodiments, the first assembly  604 ,  704  can be assembled. The pelvic bracket  638 ,  738  can be coupled to the extension  644 ,  744 , if separate components. The surgical orientation device  172  can be coupled to the mount  646 ,  746 . In some techniques, the extension  670 ,  770  can be coupled to the second coupler  648 ,  748 . The orientation sensing device  204  can be coupled to the mount  672 ,  772 . The surgical orientation device  172  and the orientation sensing device  204  form a general V-shaped configuration, similar to the orientation shown in  FIG.  12 A . The orientation sensing device  204  can be fixed in position relative to the surgical orientation device  172 . 
     In some methods of use, the probe  778  can be calibrated. The extension  770  can be decoupled from the second coupler  748 . The second assembly  706  can be assembled as shown in  FIG.  12 B . The first assembly  704  can be coupled to the second assembly  706  as shown in  FIG.  12 B . In some methods of use, the system  700  can include a calibration fixture  790 . The first assembly  704  and the second assembly  706  can be mounted to the calibration fixture  790 . The calibration fixture can include a plurality of points for the probe  778  to contact. 
     In some methods of use, the probe  778  can contact a center hole at the base of the calibration fixture  790  to calibrate a center point. The user can depress a button when the probe  778  is placed. In some methods of use, the probe  778  can contact a left hole at the base of the calibration fixture  790  to calibrate a left point. The user can depress a button when the probe  778  is placed. In some methods of use, the probe  778  can contact a right hole at the base of the calibration fixture  790  to calibrate a right point. The user can depress a button when the probe  778  is placed. The calibration fixture  790  can be utilized prior to the procedure. The calibration fixture  790  can be located away from the patient, for instance on a back table. Other calibration fixtures and jigs are contemplated. 
     The surgical orientation device  172  and the orientation sensing device  204  can be calibrated. The surgical orientation device  172  can be rested on a level horizontal surface with the display horizontal (facing up). The surgeon can hold the assemblies  704 ,  706  steady until the surgical orientation device  172  indicates completion. The orientation sensing device  204  can be rested on a level horizontal surface with the display vertical (facing user). The surgeon can hold the assemblies  704 ,  706  steady until the surgical orientation device  172  indicates completion. The surgical orientation device  172  can be rested on a level horizontal surface with the display pointed sideways (left side). The surgeon can hold the assemblies  704 ,  706  steady until the surgical orientation device  172  indicates completion. The surgical orientation device  172  can be rested on a level horizontal surface with the display horizontal (facing up) again. The surgeon can hold the assemblies  704 ,  706  steady until the surgical orientation device  172  indicates completion. Other orientations of the surgical orientation device  172  and the orientation sensing device  204  are contemplated for calibration. 
     The user can remove the required instruments and prepare the instruments for use.  FIG.  12 C  illustrates examples of components described herein. The optical component  174 ,  194  can be activated. In some embodiments, the optical component  174 ,  194  can include a movable cover or screen, such as a shutter. The user can close the shutter and insert a battery into the optical component  174 ,  194 . In some embodiments, the optical component  174 ,  194  can be coupled to the first assembly  704  using one or more fasteners. In some embodiments, the fastener is the adjustment feature  178 . In some embodiments, the fastener can be secured using a driver  792 , see  FIG.  12 C . In some embodiments, the optical component  174 ,  194  is affixed to the first assembly  704  using a hex driver. In some embodiments, the optical component  174 ,  194  is affixed to the first assembly  704  using a ball driver. In some embodiments, the optical component  174 ,  194  can be affixed to the first assembly  704  using one or more magnets as described in relation to  FIGS.  6 B- 6 C . In some embodiments, the optical component  174 ,  194  can be affixed to the first assembly  704  using one or more removable coupling devices such as clips, straps, bayonet connection, etc., and/or non-removable coupling devices such as adhesive, integrally formed, monolithically formed, etc. The surgeon can ensure that the optical component  174 ,  194  is securely attached and does not rotate on the first assembly  704 . In some embodiments, the bracket  176  facilitates the coupling of the optical component and the first assembly  704 . In some embodiments, the adjustment feature  178  facilitates the coupling of the optical component and the first assembly  704 . In some embodiments, the optical component  174 ,  194  is coupled to the fixation base  702 . In some embodiments, the optical component is coupled to the fixation pins  710 ,  712 . In some embodiments, the optical component is coupled to the second assembly  606 ,  706 . In some embodiments, the optical component  174 ,  194  is coupled directly to the pelvis. In some embodiments, the optical component  174 ,  194  remains on as long as the battery is installed. The laser or other light emission is shown or hidden through the movement of the shutter. The optical component  174 ,  194  can include a marking to indicate the direction of the emission. In some embodiments, the optical component  174 ,  194  can include an arrow to indicate the direction of the laser. 
     The user can interact with the surgical orientation device  172 . If the system  700  can be used in either hip procedure, one method can involve a surgeon selecting a module corresponding to the right hip or the left hip. In some methods of use, the user can input a target cup abduction angle. This is the Radiographic Abduction angle defined as the coronal plane projection of the angle between the acetabular axis and the longitudinal axis of the body. Abduction and adduction are also used to describe movement of the limb within the coronal plane. In some methods of use, the user can input a target cup anteversion angle. This is the Radiographic Anteversion angle defined as the angle between the acetabular axis and the coronal plane. The user can input target angles which can be stored by the surgical orientation device  172 . In some methods of use, these target angles are utilized by the surgical orientation device  172  during cup placement. 
     The system  700  can be attached to the pelvis as shown in  FIGS.  13 A- 13 C . The user can position the system  700  such that the system  700  has solid and stable mount for attachment of the instrumentation to the pelvis. In some methods of use, all measurements and references are based off the initial registration process and any movement of the first assembly  704  after will result in error in the resulting readouts of cup position, leg length, and/or joint offset. In some methods, the fixation pins  710 ,  712  are placed in the ipsilateral iliac crest. Referring to  FIG.  13 A , for the first fixation pin  710 , the surgeon can make a stab incision over the ipsilateral iliac crest, directly superior to the greater trochanter. The surgeon can insert the fixation pin  710 . In some embodiments, the fixation pin  710  is a 4.0 mm threaded fixation pin. The fixation pin  710  can be inserted vertically using a wire driver. Referring to  FIG.  13 B , the surgeon can make a second stab incision, and insert the second fixation pin  710  in the iliac crest 2 cm anterior parallel to the first pin  712 . The surgeon can use the fixation base  702  as a guide for spacing between the pins  710 ,  712 . Referring to  FIG.  13 C , the surgeon can slide the fixation base  702  over both pins to the level of the skin. The surgeon can use a driver to tighten the two fixation devices  724  to secure fixation base  702  to the fixation pins  710 ,  712 . In some methods of use, the fixation pins  710 ,  712  are placed in a similar fashion to placement of pins for pelvic external fixation. In some methods of use, the fixation pins  710 ,  712  enter the iliac wing at its most superior surface and travel between the tables of the inner and outer bone of the iliac wing. In some methods of use, the fixation base  702  is attached prior to dislocating the hip to ensure correct patient positioning and navigation accuracy. The surgeon can take steps to avoid plunging through the medial wall of the iliac wing. The surgeon can verify that fixation base  702  is securely mounted to the bone. The surgeon can minimize divergence or bending of fixation pins  710 ,  712 . 
     The system  700  can be assembled as shown in  FIG.  14 A- 14 C . Referring to  FIG.  14 A , the orientation sensing device  204  can be coupled to the probe  778 . In some embodiments, the orientation sensing device  204  and/or the probe  778  can include indicia such as arrows to facilitate alignment. Referring to  FIG.  14 B , the first assembly  704  can be secured to the fixation base  702  with the surgical orientation device  172  attached. The first assembly  704  can be secured by pushing on the lock lever  740 , as described herein. Referring to  FIG.  14 C , the second assembly  706  can be secured to the fixation base  702  with the orientation sensing device  204  attached. In some embodiments, the second assembly  706  and/or the fixation base  702  can include indicia such as arrows to facilitate alignment. The second assembly  706  can be secured by pushing on the lock lever  754 , as described herein. The optical component  174 ,  194  can be secured to the first assembly  704 . In some embodiments, the optical component  174 ,  194  and/or the first assembly  704  can include indicia such as arrows to facilitate alignment. 
     The system  700  can be aligned as shown in  FIG.  15 A . The surgeon can place the leg on the operative side in a neutral position. The surgeon can open the shutter on the optical component  174 ,  194 . The surgeon can align the optical component  174 ,  194  so that the laser projects a pattern of light. One example of the incidence of light is shown as  180 . In some embodiments, the pattern of light includes two lines. In some embodiments, the pattern of light includes two intersecting lines. In some embodiments, the pattern of light includes two perpendicular lines. In some embodiments, the pattern of light includes two parallel lines. In some embodiments, the pattern of light includes three points. In some embodiments, the pattern of light includes three points that form a triangle. In some embodiments, the pattern of light includes three points which do not lie on the same line. In some embodiments, the pattern of light is projected onto the leg. In some embodiments, the pattern of light is projected onto the knee. In some embodiments, the pattern of light is projected onto the distal foot. In some embodiments, the pattern of light is projected onto the distal thigh. In some embodiments, the pattern of light is projected onto a portion of the leg including a sterile wrap. 
     The system  700  can be adjusted as shown in  FIGS.  15 B- 15 C . To adjust the projection of the optical component  174 ,  194 , the user can adjust the articulation  726 . To adjust the projection of the optical component  174 ,  194 , the user can adjust the adjustment feature  178  (see  FIG.  6 A ). To adjust the projection of the optical component  174 ,  194 , the user can adjust the re-position of the fixation base  702 . The surgeon can loosen the fixation devices  724  to adjust the fixation base  702  as desired. The surgeon can adjust the articulation  726  to position the articulation  726  as desired. The surgeon can adjust the bracket  176  and/or adjustment feature  178  to position the optical component as desired. The surgeon can reposition any component of the system  700  as desired. 
     Once the system  700  is in the desired position, components of the system  700  can be immobilized. The surgeon can tighten the fixation devices  724  to secure the fixation base  702 . The fixation base  702  can be secured to the fixation pins  710 ,  712 . In some methods of use, the fixation base  702  remains in this position for the procedure. The articulation  726  can be locked in position. The fixation base  702  can include the lock  727 . The surgeon can advance the lock  727  against head  728  to prevent movement of the articulation  726 . In some methods of use, the surgeon can use a driver to rotate the lock  727 . The driver can be a 3.5 mm hex driver to advance the contact surface  729  against the head  728  of the articulation  726 . In some methods of use, the articulation  726  remains in this position for the procedure. The surgeon can adjust the lock  727  to reduce or prevent movement of the articulation  726 . The optical component  174 ,  194  can be secured to the first assembly  704  and/or the fixation base  702 . In some embodiments, the adjustment feature  178  can be self-locking. The adjustment feature  178  can include a plurality of discrete location. The adjustment feature  178  can lock when moved to one of the plurality of discrete location. In some methods of use, the optical component  174 ,  194  can remain immobilized during the rest of the procedure. In some methods of use, the first assembly  604  can remain immobilized during the rest of the procedure. 
     Referring to back to  FIG.  15 A , the method can include recording the incidence of the light  180 . The surgeon can record the shape of the projection. The surgeon can record the incidence of light from the optical component onto a surface. The incidence of light can be the intersection of the light with an anatomical surface of the patient. The anatomical surface can be any surface of the patient. The anatomical surface can be any surface on the leg. The method can include marking the position of the light. The method can include the step of marking two or more points along a line of light. The method can include drawing a line along the line of light. The method can include capturing an image of the incidence of light. The method of use can include the step of utilizing a camera to capture the incidence of light. In some embodiments, the surgeon traces the pattern of light. In some embodiments, the surgeon can make a mark on the femur, such as a bovie mark, a pen mark, a stitch or other durable indication. 
     In some embodiments, the surgeon can mark the incidence of light  180 . In some embodiments, the surgeon can mark two lines. In some embodiments, the surgeon can mark two intersecting lines. In some embodiments, the surgeon can mark two perpendicular lines. In some embodiments, the surgeon can mark two parallel lines. In some embodiments, the surgeon can mark a cross-hair. In some embodiments, the surgeon can mark the incidence of light from a projected pattern of light. In some embodiments, the surgeon can mark three points In some embodiments, the surgeon can mark three points which do not lie on the same line. In some embodiments, the surgeon can mark three points which are localized on a region of the leg. In some embodiments, the surgeon can mark three points which are projected onto femur. In some embodiments, the surgeon can mark three points, one or more points lie on the femur. In some embodiments, the surgeon can mark three points, one or more points lie on the femur, tibia, knee, ankle, or foot, or any combination thereof. In some embodiments, the surgeon can mark onto the leg. In some embodiments, the surgeon can mark onto the knee. In some embodiments, the surgeon can mark onto the distal foot. In some embodiments, the surgeon can mark onto the distal thigh. In some embodiments, the surgeon can trace the pattern with a marker. In some embodiments, the surgeon can trace the pattern onto the leg directly. 
     In some embodiments, the surgeon can trace the pattern on the sterile wrap. In some embodiments, the pattern of light is projected onto a portion of the leg including a sterile wrap. In some embodiments, the surgeon traces the pattern of light on the sterile wrap. In some embodiments, the surgeon marks the two lines on the sterile wrap. In some embodiments, the surgeon marks the three points on the sterile wrap. 
     In some embodiments, target probes can be provided for recording the incidence of light.  FIGS.  20 A- 20 I  illustrates examples of target probes.  FIGS.  20 A- 20 B  illustrate target probe  18   a  and  FIG.  20 C- 20 D  illustrates target probe  18   b . At least one target probe  18   a ,  18   b , or other targets or devices, can comprise a structure for contacting the anatomy of a patient and serving as a target for an emitted light from the optical component  174 ,  194 . For example, in some embodiments, 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 or surface. In some embodiments, the anatomical contact portion  107  contacts the femur. In some embodiments, the anatomical contact portion  107  contacts the knee. In some embodiments, the anatomical contact portion  107  contacts the upper thigh. In some embodiments, the anatomical contact portion  107  can be held against the anatomical feature. In some embodiments, the anatomical contact portion  107  can be drilled into the anatomical feature. In some embodiments, the anatomical contact portion  107  coupled with the anatomical feature. 
     The anatomical contact portion  107  can be connected to or integrally formed with the target portion  108 . The target portion  108  can comprise a surface which can be marked by the surgeon. The target portion  108  can comprise a surface which can record the incidence of light. The target portion  108  is configured to assist in recording the incidence of light. Aligning the incidence of light on the target portion  108  before and after cup placement can assist in aligning the underlying anatomy before and after cup placement. 
     In some embodiments, the target portion  108  can comprise one or more target shapes  110 , in the form of markings, slits, or other structures. In some methods of use, the target shapes  110  can be marked before placement of the target  18   a ,  18   b  on the anatomy. In some methods of use, the target shapes  110  are marked by the surgeon after placement of the target  18   a ,  18   b  on the anatomy. In some methods of use, the target shapes  110  are marked by the surgeon before cup placement. In some methods of use, 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.  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 . 
     In some embodiments, the optical component  174 ,  194  is adjusted to align the incidence of light with the target  18   a ,  18   b . In some embodiments, the system  700  is adjusted to align the incidence of light with the target  18   a ,  18   b . For instance, the articulation  726  can be adjusted. In some embodiments, the target  18   a ,  18   b  is adjusted to align the incidence of light with the target portion  108  of the target  18   a ,  18   b . The target portion  108  can 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 the incidence of light with the target  18   a ,  18   b . 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. 
       FIGS.  20 E- 20 F  illustrate an embodiment of target probe  18   c . In some embodiments, the target probe  18   c  is not attached rigidly to the leg. In some embodiments, the target probe  18   c  is held in position by the user.  FIG.  20 E  illustrates the target probe  18   c  in position against the anatomy of the patient, and  FIG.  20 F  illustrates the target probe  18   c  being removed by the surgeon. In the illustrated embodiment, the leg is wrapped with an incise drape. The incise drape can be marked by the user. The user has marked the longitudinal axis of the bone, as well as a home position for the target probe  18   c . These markings on the drape can be performed when the surgeon marks the incidence of light on the target probe  18   c . The target probe  18   c  can be oriented within the home position and the incidence of light can be marked. During the procedure, the user can align the marking with the marked longitudinal axis. The surgeon can adjust the anatomy until the incidence of light aligns with the marking on the target  18   c . The target  18   c  can be any shape to allow the marking of the incidence of light. In the illustrated embodiment, the target  18   c  is generally L-shaped. In some embodiments, the target probe  18   c  is removable during the surgery. The target probe  18   c  can be positioned on the leg. In some methods of use, one or more markings on the thigh  182  can aid in re-positioning of the target  18   c . The markings can include one or more lines, points, shapes, symbols, etc. In the illustrated embodiment, the markings on the thigh  182  can include a cross-hair or other pattern related to the incidence of light  180 . In some methods of use, the surgeon can position the target  18   c  before and after cup replacement. In some methods of use, the surgeon can mark the incidence of light before joint dislocation. In some methods of use, the surgeon can reposition the femur after cup placement such that the incidence of light aligns with the markings. 
       FIG.  20 G  illustrates an embodiment of target probe  18   d . The target probe  18   d  can comprise an anatomical contact portion  107  and a target portion  108 . The anatomical contact portion  107  can comprise a strap, clip, bracket, zip-tie or other structure configured to wrap around an anatomical feature or surface. In some embodiments, the anatomical contact portion  107  contacts the thigh. In some embodiments, the anatomical contact portion  107  contacts the knee. In some embodiments, the anatomical contact portion  107  contacts the shin. In some embodiments, the target portion  108  can be moved relative to the anatomical contact portion  107 . The target portion  108  can be rotated, pivoted, and/or translated to position the target portion  108  relative to the anatomical contact portion  107 . In some embodiments, the target portion  108  is fixed relative to the anatomical contact portion  107 . The target portion  108  can include one or more surfaces to mark the incidence of light. 
       FIGS.  20 H- 20 I  illustrate an embodiment of a target probe  18   e . The target probe  18   e  can comprise an anatomical contact portion  107  and a target portion  108 . The anatomical contact portion  107  can comprise a bendable surface configured to adapt to and directly contact or indirectly couple with the anatomy of the patient. The contact portion  107  can create a tri-fold shape or can be formed to a continuous curve. The contact portion  107  can include a portion to wrap around the anatomical feature or surface of the patient. In some embodiments the wrap is a separate component that is stretched or wrapped around the contact portion  107 . The contact portion  107  can include or be wrapped by an incise drape  109 , such as an iodine-impregnated incision drape (Ioban® manufactured by 3M®). The incise drape  109  can provide strong adhesion to the surface of the skin. In some embodiments, the incise drape  109  can provide antimicrobial properties for the reduction of post-operative wound infections. The contact portion  107  can be adhered or otherwise coupled to the incise drape  109  or to the leg prior to wrapping the drape  109 . The contact portion  107  can be integrally formed with the incise drape  109 . The target portion  108  can be integrally formed with the contact portion  107 . The target portion  108  can be integrally formed with the incise drape  109 . Other wraps or drapes are contemplated. The contact portion  107  can by connected to the anatomy of the patient through any means. In some embodiments, the contact portion  107  includes an adhesive. In some embodiments, the contact portion  107  is adjustable, such as through the use of an adjustable adhesive or putty. In some embodiments, the contact portion  107  includes a tape or other medical wrap. In some embodiments, the contact portion  107  includes one or more fixation pins. 
     In some embodiments, the incise drape  109  wraps around the thigh of the patient. In some embodiments, the incise drape  109  wraps around the knee of the patient. In some embodiments, the incise drape  109  wraps around the shin of the patient. In some embodiments, the target portion  108  is fixed relative to the anatomical contact portion  107  and/or the incise drape  109 . In some embodiments, the target portion  108  can be moved relative to the anatomical contact portion  107  and/or the incise drape  109 . The target portion  108  can be rotated, pivoted, and/or translated to position the target portion  108  relative to the anatomical contact portion  107 . The target portion  108  can include one or more surfaces to mark the incidence of light. The target probe  18   e  can be a vertical laser target. The target portion  108  can extend from the skin of a patient in a vertical direction. The target portion  108  can extend from the skin of a patient in a horizontal direction. 
     The target probe  18   e  can be formed of two pieces. The contact portion  107  and the target portion  108  can be separate component. The contact portion  107  and the incise drape  109  can be separate components. The target portion  108  and the incise drape  109  can be separate component. The contact portion  107  and/or the incise drape  109  can be rigidly affixed to the body of the patient. In some embodiments, the contact portion  107  and/or the incise drape  109  can be permanently fixed, or at least permanently fixed during the duration of the procedure. The contact portion  107  and/or the incise drape  109  can be affixed to the thigh to form a self-supporting structure with the thigh. The target portion  108  can be removably attached to the contact portion  107 . The target portion  108  and the contact portion  107  can couple via any mechanical connection such as a snap-fit, one or more hooks, pinch tab or button, slide pin, bayonet, and/or one or more magnets. 
     In some methods, the incise drape  109  is removed from a protective covering to expose an adhesive. In some methods, the surgeon can couple the contact portion  107  with the incise drape  109 . In some methods, the incise drape  109  and the contact portion  107  are provide to the surgeon coupled. The surgeon can position the contact portion  107  relative to the anatomy. The contact portion  107  can be positioned such that the contact portion  107  is aligned with the optical component  174 ,  184 . The contact portion  107  can be positioned against a portion of the anatomy with little or no soft tissue. The contact portion  107  can be positioned adjacent to the bone. In some embodiments, the contact portion  107  contacts the skin of the patient. In some embodiments, the contact portion  107  is spaced from the skin of the patient 
     In some methods, the incise drape  109  can be coupled to the contact portion  107  prior to positioning the contact portion  107 . In some methods, the incise drape  109  can provide an adhesive to couple the contact portion  107  to the patient. In some methods, the surgeon positions both the contact portion  107  and the incise drape  109  simultaneously. In some methods, the incise drape  109  can be coupled to the contact portion  107  after to positioning the contact portion  107  on the leg of the patient. In some methods, the incise drape  109  can be coupled to the patient after positioning the contact portion  107 . In some methods, the surgeon positions the contact portion and the incise drape  109  independently. The surgeon can cover the anatomy with the incise drape  109 . In some methods, the surgeon can wrap the anatomy with the incise drape  109  forming one or more closed loops around the anatomy. 
     In some methods, the target portion  108  can be coupled to the contact portion  107  prior to positioning the contact portion  107 . In some methods, the target portion  108  can be coupled to the contact portion  107  after to positioning the contact portion  107 . In some methods, the target portion  108  can be coupled to the contact portion  107  by a snap fit connection. In some methods, the incise drape  109  is positioned over the contact portion  107 . In some methods, the target portion  108  can couple to the contact portion  107  even if the incise drape  109  is positioned over the contact portion  107 . The target portion  108  can couple to the contact portion  107  to form a rigid connection. The target portion  108  can couple to the contact portion  107  to form a releasable connection. In some embodiments, the target portion  108  cannot be removed from the contact portion  107  once coupled. 
     The surgeon can activate the optical component  174 ,  194  to project light. The surgeon can align the optical component  174 ,  194  to project a pattern of light on the target portion  108 . One example of the incidence of light is shown as  180 . In some embodiments, the pattern of light includes two lines. In some embodiments, the pattern of light includes two intersecting lines. The surgeon can adjust the optical component  174 ,  194  such that the incidence of light  180  is located on the target portion  108 . In some embodiments, the optical component  174 ,  194  emits light before or as the surgeon positions one or more of the contact portion  107 , the target portion  108 , and/or the incise drape  109 . In some embodiments, the optical component  174 ,  194  emits light after the surgeon positions one or more of the contact portion  107 , the target portion  108 , and/or the incise drape  109 . The surgeon can mark the incidence of light  180  on the target portion  108 . The target portion  108  can include a markable, flat surface to facilitate the marking of the incidence of light  180 . The surgeon can perform one or more methods or method steps described herein. 
     The surgeon can activate the optical component  174 ,  194  to project light again. The surgeon can move the anatomy of the patient connected to the target probe  18   e . In some methods, the target probe  18   e  is coupled to the thigh and the surgeon moves the thigh. In some methods, the target probe  18   e  is coupled to the upper leg (e.g., femur) and the surgeon moves the upper leg (e.g., femur). In some methods, the target probe  18   e  is coupled to the lower leg (e.g., tibia) and the surgeon moves the lower leg (e.g., tibia). In some methods, the target probe  18   e  is coupled to the foot and the surgeon moves the foot. The surgeon can realign a portion of the anatomy such that the incidence of light  180  aligns with the mark on the target portion  108 . The surgeon can manually realign a portion of the anatomy with the position of the anatomy when the incidence of light  180  was recorded. The surgeon can realign a portion of the anatomy in order to measure joint offset. The surgeon can realign a portion of the anatomy in order to measure changes in leg length. The surgeon can realign a portion of the anatomy in order to compare a measurement before and after joint replacement. 
     The surgeon can register a parked configuration or home position. In some techniques, the distal end  780  of the probe  778  can be engaged with a point on the fixation base  702 , such as the divot  730 . The probe  778  can be vertical in the home position. The orientation sensing device  204  can be vertical in the home position. The distal end of the probe  778  can be curved or bent to facilitate registering the home position. 
     When registering the home position, the user can hold the probe  778  close to the distal end  780  to maximize accuracy of the measurement of the point. When interacting with the surgical orientation device  172 , the user can support the back of the surgical orientation device  172  to avoid flexing the fixation pins  710 ,  712  and/or the fixation base  702 . The user can register the home position by pressing a button of the surgical orientation device  172 . If the registration is not accepted, the user can keep the probe  778  stationary and press the button again. 
       FIG.  16    illustrates one embodiment of registering the table.  FIG.  16    is a top view with the patient in the lateral decubitus position of the posterior approach. The surgeon can verify the sagittal plane of pelvis is level. During positioning of the patient, the Anterior Pelvic Plane is positioned vertically. The Anterior Pelvic Plane can be defined as a plane created by the two anterior superior iliac spines (ASIS) and the anterior surface of the pubic symphysis. 
     The Anterior Pelvic Plane can be oriented vertically when the patient is in the lateral decubitus position of the posterior approach. The top surface of the operating table upon which the patient is positioned is positioned horizontally. The patient can be positioned so that the Anterior Pelvic Plane is perpendicular to the table. In some embodiments, the surgeon can visually verify the Anterior Pelvic Plane is vertical. In some embodiments, the surgeon can use devices to position the patient&#39;s body to align the Anterior Pelvic Plane perpendicular to the plane of the top surface of the table. 
     If not already horizontal, the surgeon can position operating table horizontally. The table plane can be a horizontal or generally horizontal plane. In some techniques, the operating table is horizontal and the table plane approximates the plane of the table. In some techniques, the table plane can be oriented relative to other surface in the operating room. In some techniques, the floor is horizontal and the table plane approximates the plane of the floor. In some techniques, the wall is vertical and the table plane approximately a plane perpendicular to the wall. In some techniques, the ceiling is horizontal and the table plane approximates the ceiling. Other surfaces may be use to approximate a horizontal plane. 
     During table registration, the probe  778  is coupled with the orientation sensing device  204 . In some methods of use, the probe  778  and the orientation sensing device  204  are constrained. As one example, the probe  778  can be coupled with other components of the first assembly  704  and/or the second assembly  706 . In some methods of use, the system  700  is assembled, such that the first assembly  704  and the second assembly  706  are coupled to the patient via the fixation pins  710 ,  712 . There may be mechanical constraints imposed by the configuration of the system  700 . 
       FIG.  16    illustrates one position of the probe  778  to calculate the direction of gravity when the probe  778  is generally horizontal. The probe  778  is rotated and/or pivoted by the mount  758 . The probe  778  can be extended toward the patient&#39;s foot. The probe  778  can be aligned with the long axis of the body. The probe  778  can be held substantially parallel to the plane of the table. In some embodiments, the user can align the probe  778  with the horizontal. The user can visually inspect the probe  778  from one or more locations. For instance, the user can inspect the probe  778  from a top view and a side view. In some embodiments, the user can align the probe  778  with the sagittal plane. The probe  778  can be parallel with the sagittal plane or a para-sagittal plane. The sagittal plane divides the body into right and left parts. As described herein, the orientation sensing device  204  can be positioned horizontally to measure gravity. As described herein, the probe  778  coupled to the orientation sensing device  204  can be positioned horizontally or substantially horizontally to measure gravity. Referring back to  FIG.  11   , the side view of the patient illustrates one dashed line which is parallel to the table. During table registration, the probe  778  can be parallel to the table as viewed from the side. 
     The probe  778  can be held in position or immobilized. The probe  778  can be held steady during table registration. The second assembly  706  can include the lock  766 . The lock  766  can limit or reduce slidablility of the probe  778  relative to the dock  762 . In some methods of use, the probe  778  can still pivot (e.g., pivotal motion between the dock  762  and the mount  758 ). In some methods of use, the probe  778  can still rotate (e.g., rotational motion between the mount  758  and the probe bracket  752 ). The lock  766  can reduce slidability when the table is registered. The lock  766  limits or reduces one degree of freedom during table registration. 
     The position and/or orientation of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . The user can enter an input to register the table (e.g., depress a button on the surgical orientation device  172 ). The user can interact with a user interface on the surgical orientation device  172  to signal to the surgical orientation device  172  to capture data of the orientation sensing device  204 . The surgical orientation device  172  can indicate that data was recorded. In some methods of use, the table registration can be taken at any point during the procedure. The table registration can be taken during pre-operative calibration. The table registration can be taken during intra-operative calibration. The table reference frame can be calculated in addition or as an alternative to the table plane. The surgical orientation device  172  can store the table plane and/or the table reference frame. 
     In some techniques, the table registration can be completed prior to dislocating the hip. The torque applied during dislocation can move pelvis away from the correct initial alignment. In some techniques, the fixation base  702  cannot be adjusted by the user after table registration. For instance, the user cannot adjust the fixation base  702  relative to the pins  710 ,  712 . The fixation base  702  remains in position for the rest of the procedure. In some techniques, the pelvic bracket  738  cannot be adjusted by the user after table registration. The pelvic bracket  738  remains in position for the rest of the procedure. In some techniques, angle of the pelvic bracket  738  relative to the fixation base  702  cannot be changed after table registration. 
     In some embodiments, information from one or more inertial sensors is used during table registration. As described herein, the orientation sensing device  204  and the surgical orientation device  172  can include one or more inertial sensors. In some embodiments, the position and/or the orientation of one or more inertial sensors can provide data related to the table plane. The one or more inertial sensors can detect gravity and provide a vector for the down direction. 
     The table registration can utilize a measurement of gravity. As described herein surgical orientation device  172  comprise one or more inertial sensors. As described herein orientation sensing device  204  comprise one or more inertial sensors. In some embodiments, inertial data from one or more inertial sensors is used to calculate the vertical plane and/or horizontal plane. In some embodiments, the position and/or the orientation data of one or more inertial sensors is used to calculate the table plane or table reference frame. The surgical orientation device  172  and/or the orientation sensing device  204  can comprise an accelerometer, which can provide a measurement of the direction of gravity. In some embodiments, the surgical orientation device  172  and/or the orientation sensing device  204  includes a sensor to detect the direction of gravity. The surgical orientation device  172  and/or the orientation sensing device  204  can be sensitive to the direction of gravity. The one or more inertial sensors can provide a vector aligned with vertical, e.g., for the down direction. In some embodiments, the surgical orientation device  172  and/or the orientation sensing device  204  includes a three axis accelerometer to detect orientation relative to or of gravity. 
     In some embodiments, the surgical orientation device  172  includes an accelerometer. In some embodiments, the orientation sensing device  204  includes an accelerometer. The accelerometer at rest can measure the acceleration due to Earth&#39;s gravity. The accelerometer can measure the acceleration from gravity straight downward or vertically. In some embodiments, the accelerometer can detect the magnitude and direction of the force of gravity. The accelerometer can produce a vertical vector. The accelerometer can produce a horizontal vector by transforming the vertical vector (e.g., by rotation of 90 degrees). The accelerometer can provide orientation and/or position data such that the table plane is perpendicular to the force of gravity. 
     In some embodiments, the orientation sensing device  204  measures gravity. In some embodiments, the surgical orientation device  172  measures gravity. The surgical orientation device  172  and/or the orientation sensing device  204  can provide an indication of the upward/downwards or vertical direction. The orientation sensing device  204  and/or the surgical orientation device  172  can produce a vertical vector. The surgical orientation device  172  and/or the orientation sensing device  204  can produce a horizontal vector by transforming the vertical vector of gravity (e.g., by rotation of 90 degrees). In some embodiments, the surgical orientation device  172  remains stationary when measuring gravity. In some embodiments, the surgical orientation device  172  is coupled or affixed to the pelvis of the patient when measuring gravity. In some methods of use, the surgical orientation device  172  is coupled to the patient via the fixation pins  710 ,  712  when measuring gravity. In some methods of use, the surgical orientation device  172  is constrained when measuring gravity. As one example, the surgical orientation device  172  can be coupled with other components of the first assembly  704  and/or the second assembly  706 . In some methods of use, the orientation sensing device  204  is constrained when measuring gravity. As one example, the orientation sensing device  204  can be coupled with other components of the first assembly  704  and/or the second assembly  706 . In some embodiments, the orientation sensing device  204  and the surgical orientation device  172  both determine the direction of gravity. In some embodiments, inertial data from two or more sensors are used to measure gravity. 
     The surgical orientation device  172  and/or the orientation sensing device  204  can provide a reference to gravitational zero. Gravitational zero, as referred to herein, refers generally to an orientation in which an axis of a 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. The surgical orientation device  172  can store gravitational zero for calculations related to the table plane. In some methods, gravitational zero is registered only once and utilized throughout the procedure. The table registration can include recording a measurement of gravitational zero. 
     In some methods of use, the orientation sensing device  204  can be positioned in other ways than horizontally to measure the direction of gravity. In some methods of use, the orientation sensing device  204  can measure gravity when in the home position. In some methods of use, the orientation sensing device  204  can be positioned vertically or substantially vertically to measure gravity. In some methods of use, the orientation sensing device  204  can measure gravity when contacting a point or anatomical landmark. In some methods of use, the orientation sensing device  204  can measure gravity when contacting the point before cup placement. In some methods of use, the orientation sensing device  204  can measure gravity when contacting the tracker  784 . In some methods of use, the orientation sensing device  204  can measure gravity when contacting the point on the femur. The point on the femur can be a mark, such as Fm described herein. The point on the femur can be an anatomical landmark. In some methods of use, the orientation sensing device  204  can measure the force of gravity at any angular orientation. In some methods of use, the orientation sensing device  204  determine a vertical vector of gravity when held at any position. 
     The table reference frame can include two perpendicular planes. The two perpendicular planes can include a vertical plane and a horizontal plane. The table registration generates two planes, a plane including a vector for the force of gravity and a plane perpendicular to said plane. The table plane is considered a horizontal plane. In some methods of use, the vector for the down direction can be used by the system to verify that the table plane is a horizontal plane. Plane. The horizontal plane may be recorded and stored by the surgical orientation device  172  and/or the orientation sensing device  204 . 
     In some methods of use, the vector for the down direction can be used by the system to establish a vertical plane. In some methods of use, the vector for the down direction can be used by the system to establish true vertical and true horizontal. The vertical plane can approximate the Anterior Pelvic Plane. For instance, abduction and anteversion angles can be calculated relative to the vertical plane. The vertical plane provides an estimation of the orientation of the Anterior Pelvic Plane. The vertical plane may be recorded and stored by the surgical orientation device  172  and/or the orientation sensing device  204 . The system  700  can calculate cup angles based on the vertical plane based on the assumption that the pelvis of the patient is correctly positioned such that the Anterior Pelvic Plane is vertical. In some methods of use, the abduction and anteversion angles in cup placement in total hip arthroplasty can be with respect to the vertical plane determined during table registration. 
     The orientation of the vertical plane can be a baseline for placement of the cup portion of a hip prosthesis. The surgical orientation device  172  can display information with respect to the vertical plane. In some methods of use, the abduction and anteversion angles in cup placement in total hip arthroplasty can be with respect to the vertical plane. In some embodiments, the vertical plane is determined by the surgical orientation device  172  and/or the orientation sensing device  204 . In some embodiments, the surgical orientation device  172  and/or the orientation sensing device  204  can provide orientation and/or position data related to the table reference frame. In some embodiments, the surgical orientation device  172  and/or the orientation sensing device  204  can provide orientation and/or position data related to vertical plane. In some embodiments, the surgical orientation device  172  and/or the orientation sensing device  204  can provide orientation and/or position data related to horizontal plane. 
     In some embodiments, the table plane is determined completely independently of any anatomical landmarks. The table plane provides a reference plane that is unaffected by pelvic tilt. The table plane provides a reference plane that is unaffected by errors in landmark registration due to soft tissue. The table plane also appears in large console navigation which might be familiar to the surgeon. In some methods of use, the horizontal plane is calculated based on aligning the probe  778 . In some methods of use, the vertical plane is calculated based on a measurement of gravity. In some methods of use, target cup angles are relative to the Anterior Pelvic Plane. In some methods of use, navigated cup angles are relative to the vertical plane which approximates the Anterior Pelvic Plane. The pre-operative and/or post-operative images, such as x-rays, are captured within a reference plane similar to the Anterior Pelvic Plane. The table registration may provide a reference plane that approximates the reference plane of imaging techniques. The table registration may provide a reference plane that approximates the Anterior Pelvic Plane. 
     Referring to  FIGS.  17 A- 17 B , in some methods of use, the surgeon can register a point. In some methods of use, the surgeon can register only one point. In some methods of use, the surgeon registers a single point on the femur. In some methods of use, the surgeon registers a single anatomical landmark during the procedure. The point can be located on femur of the joint being operated on. For some procedures on a patient&#39;s left hip, the point is on the left femur. For some procedures on a patient&#39;s right hip, the point is on the right femur. In some methods of use, the surgeon can make the standard incision. In some methods of use, the surgeon can identify a point along the transtrochanteric line on the proximal femur. In some methods of use, the point is the located on the greater trochanter. 
     The surgeon can position the distal end  780  of the probe  778  at the point. In some methods of use, the distal end  780  of the probe  778  is placed on the point on the greater trochanter. In some methods of use, the tip of the distal end  780  is brought into contact with a part of the greater trochanter or elsewhere on the proximal femur. In some methods of use, the tip of the distal end  780  is brought into contact with any point on the anatomy of the patient. 
     In some methods of use, after a point is found and/or contacted, the clinician can make a mark on the femur. In some methods of use, the surgeon can make a mark using a bovie mark, a pen mark, a stitch or other durable indication. In some methods of use, the surgeon can couple tracker  784 . The tracker  784  can be fastener such as a screw, bolt, pin, plate, or other durable structure. In some methods of use, the surgeon can insert 20 mm screw into the femur. In some embodiments, the tracker  784  can be secured to the femur. The tracker  784  can be rotated to be secured into the femur. The tracker  784  can be advanced into the femur with a driver. The surgeon should ensure that the tracker  784  is lateral enough so as not to interfere with the stem. The point can be located on the tracker  784 . In some methods of use, the surgeon can make a divot or burr into a bone or other portion of the anatomy of the patient. In some embodiments, the divot or burr is in the femur. The point can be located on the divot or burr. In some methods of use, the surgeon can alter the femur to provide a reliable indication of the point that is registered. 
     The probe  778  can be immobilized to register the point. In some embodiments, the surgeon can hold the tip of the probe  778  at the point. In some embodiments, the surgeon can hold the tip of the probe  778  in a divot or burr. In some embodiments, the surgeon can hold the tip of the probe  778  in a hole of the tracker  784 . In some embodiments, the surgeon can hold the tip of the probe  778  at an anatomic landmark. In some embodiments, the surgeon can hold the tip of the probe  778  at the marked point Fm. 
     As described herein, the second assembly  706  can include a lock  766 . The lock can limit or reduce slidablility of the probe  778  relative to the dock  762 . In some methods of use, the probe  778  can still pivot (e.g., pivotal motion between the dock  762  and the mount  758 ). In some methods of use, the probe  778  can still rotate (e.g., rotational motion between the mount  758  and the probe bracket  752 ). The lock  766  can reduce slidability when the point is registered. In some embodiments, the lock  766  is advanced before the point is registered. In some methods of use, the lock  766  limits or reduces one degree of freedom during point registration. 
     Once the tip of the distal end  780  is in contact with the desired point, the system  700  processes data from and stores the orientation of one or more sensor(s) in the orientation sensing device  204 . During registration, the position of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . During registration, the orientation of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . During registration, the extension of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . 
     The distance related to the extension of the probe  778  can be used in conjunction with the positional and/or orientation data from the orientation sensing device  204 . Additionally, in some embodiments, the probe  778  is provided with a marking  782  indicating position of the tip of the probe  778 , e.g., relative to the dock  762  or some other relevant fixed feature of the patient or the system  700 . The marking  782  can be read by the clinician or the camera  184 . In some embodiments, the camera  184  records the marking  782  indicating the extension of the probe  778 . The distance that the probe  778  is extended, as captured by the camera  184 , to contact the point can be recorded by the orientation device  172 . In some methods, the orientation sensing device  204  or the surgical orientation device  172  can converts the image of the camera  184  into an extension measurement of the probe  778 . When registering the anatomical points, the camera  184  captures an image of the marking  782 . The camera  184  can read the marking  782  to provide accurate determination of the translational position of the probe  778  relative to the dock  762 . The camera  184  can be directly above the marking  782 . In some methods, the camera  184  can read a binary code of the marking  782 . The surgical orientation device  172  can use the length measurement from the camera  184  and the data from the orientation sensing device  204  to determine the location of the distal end  780  of the probe  778 . 
     In some embodiments, the surgeon will enter an input (e.g., depress a button) to collect data from the orientation sensing device  204 . In some methods, the surgeon will enter an input (e.g., depress a button) to collect data from the camera  184 . In some embodiments, the surgeon will enter an input (e.g., depress a button) to collect data from the orientation sensing device  204  and the camera  184  simultaneously. In some methods, the orientation sensing device  204  and/or the camera  184  will only send data if the orientation sensing device  204  is stable or non-moving. In some embodiments, the surgeon can press a button on the surgical orientation device  172  to register the point. The surgeon can enter an input to register the point. Other ways of entering an input include interacting with a touchscreen, using a verbal command, touching an icon, holding the probe  778  steady for a period of time, and/or reaching the end of a countdown clock, etc. The surgical orientation device  172  can indicate that the point was recorded. 
     In some methods, the surgeon marks the incidence of light before registering the point. In some methods, the surgeon marks the incidence of light after registering the point. In some methods, the surgeon marks the incidence of light simultaneously with registering the point. In some methods, the surgeon marks the incidence of light but does not register the point. In some methods, the surgeon registers the point but does not mark the incidence of light. In some methods, the surgeon marks the incidence of light independently of registering the point. In some methods, the surgeon marks the incidence of light and registers the point after the leg is secured. In some methods, the surgeon marks the incidence of light and registers the point when the leg is in the same orientation. 
     The surgical orientation device  172  can record a point in the table reference frame. The table reference frame can form a coordinate system. The table reference frame can include the vertical plane and the horizontal plane. In some methods of use, the registered point is located at the origin of the table reference frame. In some methods of use, the center of rotation of the femur is located at the origin of the table reference frame. The user can record a point in the table reference frame before cup placement. The user can record the same point in the table reference frame after cup placement. The system  700  can compare the measurement of the same point before and after cup placement. The comparison can relate to leg length. The comparison can relate to joint offset. In some embodiments, changes in the registered point along the vertical plane indicate a change in leg length. In some embodiments, changes in the registered point along the horizontal plane indicate a change in joint offset. 
     In some techniques, the table registration is completed prior to dislocating the hip. In some techniques, the point is registered prior to dislocating the hip. In some techniques, the incidence of light is marked prior to dislocating the hip. Once registration is complete, the surgeon can proceed to dislocate the hip, resect the femoral head, and prepare the acetabulum as per the implant manufacturer&#39;s technique. The torque applied during dislocation can move pelvis away from the correct initial alignment. 
     In some techniques, the fixation base  702  cannot be adjusted by the user after table registration, home registration, recording the incidence of light, and/or point registration. For instance, the user cannot adjust the fixation base  702  relative to the pins  710 ,  712 . The fixation base  702  remains in position for the rest of the procedure. In some techniques, the pelvic bracket  738  cannot be adjusted or removed. The pelvic bracket  738  remains in position for the rest of the procedure. In some techniques, angle of the pelvic bracket  738  relative to the fixation base  702  cannot be changed. In some techniques, the probe  778  cannot be replaced with a different probe. The same probe  778  is used for the remainder of the procedure. 
     In some methods of use, the surgical orientation device  172  can provide options to the user regarding how to proceed. In some methods of use, the surgeon can set anteversion and/or abduction cup angles. In some methods of use, the surgical orientation device  172  can store target cup angles. In some methods of use, the surgeon can input anteversion and/or abduction cup angles into the surgical orientation device  172 . In some methods of use, the surgeon set the target angle of the cup. In some methods of use, the surgical orientation device  172  can allow the surgeon to check the target angles after the surgeon sets the target angle of the cup. 
     In some methods of use, the surgical orientation device  172  can provide options related to leg length and joint offset. In some methods of use, the surgical orientation device  172  can measure leg length from a pre-operative state. In some methods of use, the surgical orientation device  172  can measure offset from a pre-operative state. In some methods of use, the surgical orientation device  172  can measure leg length before cup placement. In some methods of use, the surgical orientation device  172  can measure joint offset before cup placement. In some methods of use, the surgical orientation device  172  can measure changes in the registered point. In some methods of use, the surgical orientation device  172  can measure changes in the registered point in the table reference frame. In some methods of use, the surgical orientation device  172  can measure changes in the registered point in the table reference frame comprising the vertical plane. In some methods of use, the surgical orientation device  172  can measure changes in the registered point in the table reference frame comprising the horizontal plane. In some methods of use, the surgical orientation device  172  can measure changes in the registered point in the table reference frame comprising the vertical plane and the horizontal plane. 
     In some methods of use, the surgical orientation device  172  can provide options related to the home position. In some methods of use, the surgeon can position the probe  778  at the home position during the procedure. In some methods of use, the surgeon can position the probe  778  at the home position to verify that one or more components of the system  700  remain fixed. In some methods of use, the surgical orientation device  172  can repeat the registration of a point. In some methods of use, the surgical orientation device  172  can repeat the acquisition of the point used. The surgical orientation device  172  can repeat acquisition of the point before the joint is dislocated. The surgical orientation device  172  can repeat acquisition of the point after insertion of a medical prosthesis. In some methods of use, the surgical orientation device  172  can indicate the end of the procedure. In some methods of use, the surgeon can end the procedure to select the other hip for a bi-lateral procedure. 
     Once registration is complete, the user can proceed to proceed to dislocate the hip, resect the femoral head, and prepare the acetabulum. The user can prepare the impactor and shell. The user can remove the second assembly  706  from the first assembly  704 . The user can remove the orientation sensing device  204  from the probe  778 . The user can dock the orientation sensing device  204  to the first assembly  704 . The surgical orientation device  172  and the orientation sensing device  204  form a general V-shaped configuration, similar to the orientation shown in  FIG.  12   . The user can set the cup angle. In some methods of use, the surgeon can hold the hip stable until the surgical orientation device  172  provides an indication to proceed. 
     The user can remove the orientation sensing device  204  from the first assembly  704 . The orientation sensing device  204  and the surgical orientation device  172  can at this point be used to guide placement of the cup in the prescribed orientation. The surgeon can remove the extension  770  from the third coupler  768 . The surgeon can couple the extension  770  to an impactor. In some embodiments, if the orientation sensing device  204  is moved too quickly, an error message will appear on the surgical orientation device  172 . In some embodiments, if the orientation sensing device  204  is moved too quickly, the orientation sensing device  204  can be coupled to the first assembly  704  as shown in  FIG.  12   . 
       FIG.  18 A  illustrates an embodiment of an impactor  300 A. In some methods of use, the orientation sensing device  204  can be coupled to the impactor  300 A. The orientation sensing device  204  can determine cup angles relative to a reference plane as the impactor  300 A is moved. The impactor  300 A can include a shell  312 A. The movement of the shell  312 A is cushioned by a plurality of spring members  340 ,  344  which are configured to absorb at least some of the shock of the impact on the impactor  300 A. The shell  312 A can include a fourth coupler  342  (see  FIGS.  18 B- 18 D ). This fourth coupler  342  permits the orientation sensing device  204  to couple to the shell  312 A. The orientation sensing device  204  can be removably coupled to the fourth coupler  342 . The orientation sensing device  204  can be coupled to the impactor  300 A in order to navigate cup angles, as described herein. 
     In some embodiments, the fourth coupler  342  can be a universal coupler. This permits the fourth coupler  342  couple to any other device or subsystem, as described herein. In some embodiments, the fourth coupler  342  is identical or substantially similar to the first coupler  632 , second coupler  648 , and/or the third coupler  668 . The fourth coupler  342  can couple to one or more components of the system  600 , such as the orientation sensing device  204 . The fourth coupler  342  can include an elongate post. The fourth coupler  342  can include a slot. The slot can be designed to lock with the orientation sensing device  204 , or a component thereof such as the extension  670 . The extension  670  can include a detent. The detent can be sized and shaped to be received within the slot of the fourth coupler  342 . The engagement of the detent and the slot can rigidly couple the orientation sensing device  204  with the fourth coupler  342 . The engagement between the fourth coupler  342  and the extension  670  of the orientation sensing device  204  minimizes or prevents relative movement therebetween to avoid any mechanical relative movement during navigation procedures. 
     The fourth coupler  342  can include a tapered surface. The tapered surface can facilitate entry of the fourth coupler  342  into the extension  670 . In some embodiments, the fourth coupler  342  can have a regular shape (e.g., cylindrical). In some, the orientation sensing device  204  can mate with the fourth coupler  342  in a plurality of orientations. In some embodiments, the fourth coupler  342  can have an irregular shape (e.g., triangular, teardrop, elliptical, rectangular). The irregular shape can facilitate alignment of the orientation sensing device  204  relative to the fourth coupler. In some, the orientation sensing device  204  can mate with the fourth coupler  342  in a single orientation. 
     The orientation sensing device  204  can be releasably coupled to the extension  670 . The extension  670  can include a mount  672  designed to couple with the orientation sensing device  204 . In the illustrated embodiment, the mount  672  includes a lock and release lever that can pivot relative to the extension  670 . The orientation sensing device  204  can include features to mate with the lock and release lever. Other configurations are contemplated. The orientation sensing device  204  is rigidly coupled to the extension  670  when engaged by the mount  672 . 
     In some embodiments, impactor  300 A is provided which includes the shell  312 A with the fourth coupler  342 . The impactor  300 A can be provided by the manufacturer of other components of the systems described herein. The impactor  300 A can include the forth coupler  342  to allow the impactor  300 A to interface with the orientation sensing device  204 . In some embodiments, an impactor is provided which does not include the fourth coupler  342 .  FIGS.  18 B- 18 D  illustrate embodiments of a universal impactor adapter. The universal impactor adapter can allow any impactor to be used with the systems described herein. The universal impactor adapter can allow the orientation sensing device  204  to couple with any impactor. In some embodiments, the universal impactor adapter can be an attachment which provides the fourth coupler  342  to allow the orientation sensing device  204  to mount thereon. The orientation sensing device  204  can mount on a large array of impactors, not only impactor  300 A. The universal impactor adapter can be coupled to any impactor to provide the fourth coupler  342 . The universal impactor adapter can provide a means to rigidly couple the fourth coupler  342  to the impactor. The universal impactor adapter can provide a means to rigidly couple the orientation sensing device  204  to the impactor. 
       FIG.  18 B  is an embodiment of a universal impactor adapter  350 .  FIGS.  18 C- 18 D  is an embodiment of a universal impactor adapter  352 . The universal impactor adapter  350 ,  352  can be designed to couple to a plurality of impactors. The universal impactor adapter  350 ,  352  can be designed to couple to impactors having a certain range of sizes of shafts or coupling portions. The universal impactor adapter  350 ,  352  can be designed to couple to impactors having a different shapes or configurations. The universal impactor adapter  350 ,  352  can include the fourth coupler  342 . The universal impactor adapter  350 ,  352  can include any coupler designed to couple to the orientation sensing device  204 . The universal impactor adapter  350 ,  352  can couple to a shaft of an impactor by any manner of connections. The universal impactor adapter  350  can connect to a shaft of an impactor with one or more magnets  354 . The one or more magnets  354  of the universal impactor adapter  350  can be configured to attract and couple to the one or more magnets (not shown) of an impactor. The impactor is configured to be inserted within the recess  358 . The recess  354  is an arcuate channel for receiving a shaft of an impactor within a range of impactor shaft sizes. While four magnets  354  are shown in  FIG.  18 B , other configurations are contemplated (e.g., one magnet, two magnets, three magnets, four magnets, five magnets, six magnets, etc.). The four magnets can be angled downward toward the recess  358 . This orientation is to concentrate the magnetic force in the recess  358  to enhance the attraction of the adaptor  350  to a shaft of an impactor that is fitted in the recess  358 . The four magnets can be angled downward relative to the fourth coupler  342 . While two magnets are shown on one side of the universal impactor adapter  350 , two additional magnets  354  have a mirror image configuration on the other side of the device in the illustrated embodiment. The magnets are directed toward the recess  358  are configured to interact with corresponding magnets of the impactor in one embodiment. The one or more magnets  354  of universal impactor adapter  350  can be configured to attract and couple to the one or more magnets of the impactor. In some embodiments, one or more magnets  354  can be configured to attract a magnetic material disposed on or in the shaft of the impactor. In some embodiments, the impactor, or a portion thereof, comprises a magnetic material. In some embodiments, the entire impactor is magnetic. The one or more magnets  354  of the universal impactor adapter  350  can allow the universal impactor adapter  350  and the forth coupler  342  to form a self-supporting structure with the impactor when assembled. The forth coupler  342  can be rigidly coupled such that any movement of the impactor causes correcting movement of the fourth coupler and the reference sensor device  204  coupled thereto. The one or more magnets  354  of the universal impactor adapter  350  can reduce or prevent unwanted movement between the impactor and the orientation sensing device  204 . 
     The universal impactor adapter  352  can connect to a shaft of an impactor with one or more clamps  356 .  FIG.  18 C  illustrates the clamp  356  when tightened and  FIG.  18 D  illustrates the clamp  356  when loosened. The clamp is an example of a mechanical connection between the universal impactor adapter  352  and any impactor. The clamp  356  can include a round inner surface to connect to a round outer surface an impactor. 
     The clamp  356  of the universal impactor adapter  352  can allow the universal impactor adapter  352  and the forth coupler  342  to form self-supporting structure with the impactor. The clamp  356  of the universal impactor adapter  352  can reduce or prevent unwanted movement between the impactor and the orientation sensing device  204 . The clamp  356  can apply a force necessary to rigidly couple to the exterior surface of the impactor. Other configurations of the universal impactor adapter are contemplated. 
     The impactor  300 A or any impactor with the universal impactor adapter  350 ,  352  can be modified to suit any of a plurality of hip prostheses. For example, a plurality of tip components  348  can be provided in a kit where each tip component is attachable to and detachable from a distal end of the shaft of the impactor. Two types of tip adapters are shown in  FIG.  12 C . In some embodiments, the tip adapter  348  can be offset. The plurality of tip adaptors is optional. 
     The acetabular shell can be threaded onto a tip component  348 . The user can select the appropriate shell adapter for the desired impactor. The impactor  300 A or any impactor with the universal impactor adapter  350 ,  352  also is configured to be modified to suit any of a plurality of hip prostheses. In some methods of use, the surgeon can thread acetabular shell onto tip component  348 . In some methods of use, the surgeon can snap the tip component  348  onto end of impactor shaft. In some embodiments, the tip component  348  can be rotated to multiple angles relative to impactor to align the screw holes of shell as desired. In some embodiments, if none of available tip component  348  fit on selected shell, then the impactor  300 A cannot be navigated. In some embodiments, if none of available tip component  348  fit on selected shell, then another impactor is selected based on the selected shell. The impactor can be outfitted with the universal impactor adapter  350 ,  352  to be able to couple with the orientation sensing device  204 . In some embodiments, prior to impacting, the surgeon can verify shell is fully seated on shoulder of impactor. In some embodiments, prior to impacting, the surgeon can verify that threads do not protrude beyond outer face of shell. Another embodiment of an impactor is shown in  FIG.  12 C . The impactor  300 B can have any of the features of the impactor  300 A described herein. The impactor  300 B is an offset shell impactor. The impactor  300 A is a straight shell impactor. The plurality of impactors is optional. 
     In some methods of use, the impactor is not navigated as described herein. In some embodiments, the cup angle can be checked after insertion by registering the hip center. In some methods of use, the surgeon can register three points on the outer rim of the cup. These three points define the hip center. In some embodiments, the point which is equidistant from all three points is the hip center. Additionally, these three points define the plane of the cup. The cup angle is defined as the angle of an axis which is perpendicular to this plane. Note that the impactor is perpendicular to this axis. Additional information regarding the registration of points and identification of the hip center can be found in U.S. application Ser. No. 14/639,758 filed Mar. 5, 2015; Ser. No. 14/639,784 filed Mar. 5, 2015; Ser. No. 13/800,620, filed Mar. 13, 2013; and Ser. No. 14/643,864 filed Mar. 10, 2015, the disclosures of which are incorporated by reference in their entirety. In some methods of use, there is no registration of the hip center. In some methods of use, only a single point is registered. In some methods of use, the point is registered before and after cup placement for leg length and/or joint offset. In some methods of use, no points are registered. In some methods of use, the surgeon does not calculate leg length and/or joint offset using point registration. 
     The acetabular shell can be inserted into the acetabulum and positioned at the desired angle. As described herein, the surgeon can store target angles with the surgical orientation device  172 . The surgical orientation device  172  can guide the surgeon in placing the cup relative to the target angles. As described herein, the target abduction and anteversion angles can be cup angles entered by the surgeon into the surgical orientation device  172 . The target abduction and anteversion angles can be an input into the system  700 . 
     In some methods of use, once the orientation sensing device  204  is attached to impactor  300 A or any other impactor with the universal impactor adapter  350 ,  352 , the surgical orientation device  172  can display radiographic inclination and anteversion angles of impactor. In some methods of use, once the orientation sensing device  204  is attached to impactor, the surgical orientation device  172  can display radiographic inclination and anteversion angles of impactor relative to frontal pelvic plane. In some methods of use, once the orientation sensing device  204  is attached to impactor, the surgical orientation device  172  can display radiographic inclination and anteversion angles of impactor relative to the vertical plane. In some methods of use, once the orientation sensing device  204  is attached to impactor, the surgical orientation device  172  can display radiographic inclination and anteversion angles of impactor relative to a plane that approximates the Anterior Pelvic Plane. The angle of the impactor can be calculated in real-time. 
     The surgical orientation device  172  can graphically display when the orientation sensing device  204  is navigated to the target abduction and anteversion angles. The surgical orientation device  172  can include indicia such as a target or bullseye to indicate the pre-determined abduction and anteversion angles. The surgical orientation device  172  can include indicia such as a dot or cross-hair to indicate movement of the impactor. Aligning the indicia in the center of the target or bullseye can indicate that the impactor is aligned with the predetermined cup angles. In some methods of use, the surgeon aligns cross-hairs in a center of a bull&#39;s eye. In some methods of use, the surgeon aligns a bubble level. In some methods of use, the surgeon aligns two indicia. In some methods of use, the surgeon substantially aligns a moving indicia with a fixed indicia. In some methods of use, the surgeon moves an indicia on the user interface of the surgical orientation device  172  by moving the impactor. In some methods of use, the surgeon moves an indicia on the user interface of the surgical orientation device  172  by moving the orientation sensing device  204 . Aligning a visual indicator displayed on the surgical orientation device  172  can guide the user to position the impactor at the desired cup angles. The indicia can move in real-time. 
     The surgical orientation device  172  can graphically display the abduction and anteversion angles as the orientation sensing device  204  is moved. In some methods of use, the indicia align when the impactor is positioned at the target anteversion angle. In some methods of use, the indicia align when the impactor is positioned at the target abduction angle. In some methods of use, the surgeon enters the target anteversion angle and/or the target abduction angle into the surgical orientation device  172 . 
     In some methods of use, the surgical orientation device  172  displays a target angle. The target abduction and anteversion angles can be displayed statically. The surgical orientation device  172  can include a readout of the abduction and anteversion angles. The readout of the abduction and anteversion angles can change as the impactor is moved. The readout of the abduction and anteversion angles can be in real-time. In some methods of use, the surgeon compares readout and the target angle to position a cup at the target angle. In some methods of use, the surgical orientation device  172  provides a graphical display to assist the surgeon in aligning the cup with the target angles. In some methods of use, the surgical orientation device  172  provides a user interface to assist the surgeon in aligning the cup with the target angles. In some methods of use, the surgical orientation device  172  provides visual feedback when the impactor is aligned with one or more target angles. As described herein, angles displayed can be calculated according to their radiographic definitions. In some methods of use, the surgical orientation device  172  can provide the readout of angles dynamically. 
     The user can enter an input once the desired cup angles are reached. The user can have a set amount of time to align the impactor with the desired cup angles. In some methods of use, the surgeon must align the impactor at the desired target angle within a period of time. In some methods of use, the surgeon must align the impactor at the desired target angle within 30 seconds, 25 second, 20 seconds, less than a minute, less than 30 seconds, etc. The user can align impactor at desired cup angle. In some methods, after the impactor is positioned relative to the desired cup angles, the cup angles can be displayed statically. The cup angles can be checked after impacting by repeating one or more of the proceeding steps. 
     In some methods of use, the surgical orientation device  172  proceeds to the next step if the timer expires (e.g., 30 second timer, 25 second timer, 20 second timer, 1 minute timer, etc.). In some methods of use, the surgical orientation device  172  proceeds to the next step if a button of the surgical orientation device  172  is pressed. In some methods of use, the surgical orientation device  172  proceeds to the next step if the orientation sensing device  204  detects an impact strong enough to disrupt navigation. In some methods of use, the surgical orientation device  172  displays abduction and/or anteversion cup angles statically. In some methods of use, the surgical orientation device  172  displays abduction and/or anteversion cup angles statically after impaction. In some methods of use, the surgical orientation device  172  displays abduction and/or anteversion cup angles after the timer expires. In some methods of use, the surgical orientation device  172  displays abduction and/or anteversion cup angles after the user enters an input, such as depressing a button. In some methods of use, the surgical orientation device  172  displays abduction and/or anteversion cup angles after navigation has ended. 
     The surgical orientation device  172  can provide cup angles relative to any reference plane, including those described herein. The surgical orientation device  172  can provide cup angles relative to the vertical plane. The surgical orientation device  172  can provide cup angles relative to a plane that approximates the Anterior Pelvic Plane. The surgical orientation device  172  can provide cup angles relative to a plane acquired during table registration. The surgical orientation device  172  can provide cup angles relative to a plane that includes a vector for gravity. 
     In some embodiments, the surgeon can check cup angle after impacting as cup angle will change during impaction. In some embodiments, the cup angle is displayed up to the beginning of impaction, typically after the first mallet strike. In some methods of use, the surgeon will typically strike the impactor several times during cup placement. In some methods of use, these strikes may change the orientation of the cup. In some embodiments, the surgical orientation device  172  displays only the cup angle from prior to impaction. In some methods of use, the surgeon will repeat the cup navigation procedure by coupling the orientation sensing device  204  to the first assembly  704  such that it is in a fixed orientation with the surgical orientation device  172 . In some methods of use, the configuration can be similar to the configuration shown in  FIG.  12 A . In some methods of use, the surgeon can interact with the orientation sensing device  204  and/or surgical orientation device  172  using one or more of the method steps described herein. Then the surgeon will move the orientation sensing device  204  to the impactor. The system  700  will now display the current cup angle. In some embodiments, the surgeon can check cup angle after impacting to improve accuracy. In some embodiments, the surgeon can verify the position of orientation sensing device  204  and the surgical orientation device  172  after impacting before checking angles. In some embodiments, the surgeon can visually confirm cup angles before proceeding. 
     After positioning the cup, the user can attach the second system  706  to the first system  704 , similar to the configuration shown in  FIG.  7   . In some methods of use, the user can measure for leg length and/or joint offset. At the surgeon&#39;s discretion, the system  700  can be used to navigate a condition, location and/or orientation of the femur prior to hip replacement. At the surgeon&#39;s discretion, the system  700  can be used to navigate a condition, location and/or orientation of the femur after hip replacement. 
     Referring to  FIG.  19 A- 19 B , the surgeon can manually re-position the femur. In some embodiments, the surgeon can manually re-position the femur in the orientation in which the point was recorded. In some embodiments, the surgeon can manually re-position the femur in the orientation prior to cup placement. In some embodiments, the surgeon can manually re-position the femur in the orientation prior to joint replacement. In some methods, the surgeon opens the shutter of the optical component  174 ,  194 . The method can include projecting light from the optical component  174 ,  194 . In some methods of use, the incidence of light may not align with the marking. In some methods of use, the femur has moved from the orientation when the point was registered. In some methods of use, the femur has moved from a previously recorded orientation. In some methods, the surgeon positions the leg so that the optical component  174 ,  194  projects a light onto the leg. In some embodiments, the optical component  174 ,  194  projects onto the femur. In some embodiments, the optical component  174 ,  194  projects onto the sterile wrap. In some embodiments, the optical component  174 ,  194  projects light onto the distal thigh. 
     Referring to  FIGS.  19 A- 19 B , the method can include aligning incidence of light with the prior marking or recording of the incidence of the light. In some embodiments, the surgeon can manually position the femur by moving the femur. The femur can be moved in anterior-posterior direction. The femur can be moved in varus-vulgas direction. The femur can be rotated about the head of the femur. In some embodiments, the surgeon can manually position the femur after the joint is replaced, such as after a cup is placed within the joint. In some embodiments, the surgeon can realign the femur such that the femur is in same positon before and after cup placement. In some embodiments, the surgeon can realign the femur such that the femur is in same positon before and after joint replacement. In some embodiments, the surgeon can position the femur to be in the same position as when the surgeon traced the incidence of light. In some embodiments, the surgeon can position the femur to be in the same position as when the surgeon recorded the point. The surgeon can extend and/or rotate the femur to position the femur. 
     In some embodiments, the surgeon positions the leg such that the incidence of light from the optical component  174 ,  194  aligns with the traced pattern. In some embodiments, the surgeon positions the femur relative to the pelvis. In some embodiments, the surgeon positions the femur such that the incidence of light from the optical component  174 ,  194  aligns with one or more marks. In some embodiments, the surgeon positions the femur such that the incidence of light aligns with two lines. In some embodiments, the surgeon positions the femur such that the incidence of light aligns with a marked cross-hair. In some embodiments, the surgeon positions the femur such that the incidence of light aligns with three marked points. In some embodiments, the surgeon positions the femur such that the incidence of light aligns with a marking on the sterile wrap. In some embodiments, the surgeon positions the femur such that the incidence of light aligns with a marking on the target probe  18   a ,  18   b . In some embodiments, the surgeon positions the femur such that the incidence of light passes through one or more slots of the target probe  18   a ,  18   b . In some embodiments, the surgeon discontinues use of the optical component if the cross-hair pattern is obscured. 
     Referring to  FIG.  19 C , in some methods of use, the surgeon can register the point after positioning the femur. In  FIG.  19 C , the incidence of light  180  aligns with the marking. While a cross-hair pattern is shown in  FIG.  19 C , the incidence of light  180  and the marking can be any pattern. By aligning the incidence of light  180  and the marking, the femur is in the same position before and after cup placement. 
     In some methods of use, the surgeon can register the point after cup placement. In some methods of use, the surgeon can register the same point intra-operatively. In some embodiments, the surgeon can register the point after the cup is placed at one or more desired target angles. In some embodiments, the surgeon can register the point after joint replacement. The surgeon can position the distal end  780  of the probe  778  at the point. In some methods of use, the distal end  780  of the probe  778  is placed on part of the greater trochanter or elsewhere on the proximal femur. In some methods of use, the distal end  780  of the probe  778  is placed on the mark on the femur. In some methods of use, the distal end  780  of the probe  778  is placed on the tracker  784 . In some methods of use, the distal end  780  of the probe  778  is placed on a divot or burr on the femur. 
     The probe  778  can be immobilized to register the point. In some embodiments, the surgeon can hold the tip of the probe  778  at the point. The second assembly  706  can include a lock  766 . The lock  766  can limit or reduce slidablility of the probe  778  relative to the dock  762 . The lock  766  limits or reduces one degree of freedom during point registration. 
     Once the tip of the distal end  780  is in contact with the desired point, the system  700  processes data from and stores the orientation of one or more sensor(s) in the orientation sensing device  204 . During registration, the position of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . During registration, the orientation of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . During registration, the extension of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . In some embodiments, the surgical orientation device  172  can register the point. In some embodiments, the surgeon can press a button on the surgical orientation device  172  to register the point. 
     In some methods, the surgeon aligns the marking with the projection of light before registering the point. In some methods, the surgeon aligns the marking with the projection of light simultaneously with registering the point. In some methods, the surgeon aligns the marking with the projection of light but does not register the point. In some methods, the surgeon registers the point but does not align the marking with the projection of light. In some methods, the surgeon aligns the marking with the projection of light independently of registering the point. In some methods, the surgeon aligns the marking with the projection of light and registers the point after the leg is fixed. In some methods, the surgeon aligns the marking with the projection of light, secures the femur, and then registers the point after the femur is secured. 
     If the point is acquired in the procedure prior to separating the natural joint, the same point can be acquired after the prosthetic joint is placed to confirm that the replacement of the joint has not changed either the length of the leg, the off-set of the leg from the trunk of the patient, or both. After joint replacement, the distal end  780  of the probe  778  can be brought into contact with the same point acquired early in the procedure. The orientation of the orientation sensing device  204  and the extension of the probe  778  can be input into the surgical orientation device  172 . These data enable the surgical orientation device  172  to output amounts of change in leg length and leg offset. 
     The system  700  can measure the orientation of the femur relative to pelvis during a baseline measurement of the point. The system  700  can measure the orientation of the femur relative to pelvis during one or more intra-operative measurements of the point. The system  700  can store the two-dimensional coordinates of the point in the table reference frame. In some methods of use, the surgeon can correct for changes in orientation by doing a rotation about the center of rotation of the femur. In some methods of use, the surgeon can correct for changes in orientation by aligning the incidence of light from the optical component  174 ,  194  with the marking on the femur. In some methods of use, the surgeon manually realigns the femur to take another measurement of the point. In some methods of use, the method can require obtaining a single point on the femur. The single point can be a mark. The single point can be a tacker  784  or other fixture such as a screw or pin. The single point can be an anatomical landmark. The single point can be a burr or divot in the femur. The point can be registered by the probe  778  intra-operatively each time the leg length and/or joint offset is to be measured. 
     Before navigation systems, such as system  700 , surgeons did not take measurements intra-operatively. Rather, surgeons typically looked at the cup placement during a procedure and determined whether current cup placement looked like previous cup placements. The surgeon would visually confirm cup placements during surgery and past experience in viewing post-operative images. The surgeon would determine if the current cup placement was likely to correlate to the correct abduction and anteversion angles post-operatively. The surgeon would look at the cup placement and determine that the placement looks like 40 degrees×15 degrees based on their experience looking at post-operative images. The surgeon&#39;s confidence in the procedure would be based on their correlation of cup placement and post-operative images. 
     For the system  700 , the user is provided with an output that assists a user to navigate to proper cup placement. The output can be abduction and anteversion angles displayed on the surgical orientation device  172 . The user can navigate to the desired abduction and anteversion angles by moving components of the system  700 , such as the impactor  300 A or any impactor with the universal impactor adapter  350 ,  352 . When the user places the cup at the desired abduction and anteversion angles, the user wants to see the same or similar angle on post-operative images. The user&#39;s confidence in the navigation of the system  700  increases if the abduction and anteversion angles produced by the system  700  match the post-operative images. The vertical plane, determined from gravity as described herein, can match the plane used in post-operative images. In some embodiments, the vertical plane may be similar to the reference plane of imaging techniques. In some methods of use, with some patients, the vertical plane provides abduction and anteversion angles that closely match post-operative images. 
     In some methods of use, as described herein, the method can include one or more of the following steps. The method can include recording the position of a probe  787  as the probe touches the point after replacing the hip joint. The method can include comparing the position of a probe as the probe touches the point to the position recorded before replacing the hip joint. In some embodiments, the surgical orientation device  172  compares two or more measurements of the point. In some embodiments, the surgical orientation device  172  compares measurements of the point before and after the cup is replaced. In some embodiments, the surgical orientation device  172  can provide a visual output of the change in leg length. In some embodiments, the surgical orientation device  172  can provide a visual output of the change in joint offset. In some embodiments, the surgical orientation device  172  can provide a visual output of the direction of change of leg length (e.g., longer or shorter). In some embodiments, the surgical orientation device  172  can provide a visual output of the direction of change of joint offset (e.g., lateral). 
     In some methods of use, as described herein, the method can include one or more of the following steps. The method can include confirming the leg length after replacing the hip joint. The method can include confirming joint offset after replacing the hip joint. When measuring changes in leg length and/or lateral joint offset, the apparent changes are sensitive to changes in the orientation of the femur relative to the pelvis. In some methods, the changes are particularly sensitive to the abduction angle. The changes are moderately sensitive to the rotation about the mechanical axis of the femur. The optical component  174 ,  194  can be used to verify the orientation of the femur relative to the pelvis before and after replacing the hip joint. In some methods, confirming the leg length and/or joint offset can include obtaining a single point of the femur. The method of use can include the step of manually realigning the femur about the center of rotation (COR) of the hip 
     In some methods of use, as described herein, the method can include one or more of the following steps. The method can include projecting light after replacing the hip joint. The method can include comparing the position of the light before and after replacing the hip joint. The method can include comparing the incidence of light after replacing the hip joint with the one or more marks made before replacing the hip joint. The method can include the comparing the incidence of light after replacing the hip joint with the two or more marks made before replacing the hip joint. The method can include comparing the incidence of light after replacing the hip joint with a line made before replacing the hip joint. 
     In some methods of use, as described herein, the method can include one or more of the following steps. The method can include confirming the position of the leg relative to the pelvis after replacing the hip joint. The method can include confirming the position of the femur relative to the pelvis after replacing the hip joint. The optical component  174 ,  194  can be useful to measure the orientation of the leg relative to pelvis during preoperative baseline and postoperatively. The surgeon can correct for changes in orientation by repositioning the leg based on the incidence of light. These marks can guide the surgeon in replicating the orientation of the leg relative to the pelvis each time a leg length measurement or joint offset measurement is needed. The optical component  174 ,  194  can be used in conjunction with the posterior approach described herein. 
     In some embodiments, the surgeon can verify the home position after measuring leg length and/or joint offset. The second assembly  706  can be coupled to the first assembly  704 . The first assembly  704  can be coupled to the fixation base  702 . In some techniques, the distal end  780  of the probe  778  can be engaged with a point on the fixation base  702 , such as the divot  730 . The user can enter an input to record the home position. In some methods of use, the home position remains fixed relative to the pelvis throughout the procedure. In some embodiments, the surgical orientation device  172  can indicate a change in the home point. The number displayed may not be zero due to mechanical play and noise of the orientation sensing device  204 . In some methods of use, if displayed number is greater than 3 mm, then the surgeon can verify all reference sensor attachments and jig connections are correct and secure before repeating. In some methods of use, if displayed number is greater than 3 mm, then surgeon can repeat registration of the point or alignment of the femur. In some methods of use, repeating registrations will result in a loss of all previous registrations. In some methods of use, the surgeon determines whether the fixation base  702  has moved. In some methods of use, the surgeon can end the procedure. In some methods of use, ending the procedure can result in loss of previous registrations. In some methods of use, ending the procedure can result in information being stored. In some methods of use, the leg length is stored. In some methods of use, the joint offset is stored. In some methods of use, the target angles are stored. In some methods of use, the fixation base  702  and the fixation pins  710 ,  712  are removed prior to closure. In some embodiments, the surgical orientation device  172  is discarded. In some embodiments, the orientation sensing device  204  is reusable. In some embodiments, the optical component  174 ,  194  is reusable. 
     The table plane can be an improvement over a landmark-based reference planes for some patients. In some embodiments, the landmark-based reference planes may differ from the vertical reference plane calculated herein due to patient specific factors. For instance, pelvic tilt may orient the landmark-based reference planes at an angle from the vertical reference plane. For instance, the patient&#39;s high body mass index may impact the ability to contact anatomical landmarks. For instance, the anatomical features of the reference points may not be visible and/or palpable while the patient is in the lateral decubitus position of the posterior approach. For instance, the ipsilateral ASIS, the contralateral ASIS, and/or the pubic symphysis may not be visible and/or palpable. The patient specific factors can results in differences between navigated cup angles from the landmark-based reference planes and angles measured post-operatively. In some methods of use, with some patients, the landmark-based reference planes may not provide abduction and anteversion angles that match post-operative images. 
     Systems and methods described herein can improve prosthetic hip joint placement using navigation. These hip procedures generally guide a prosthetic hip to an orientation within the acetabulum that minimizes the chance of dislocation due to impingement of the femoral neck on the cup or on bones around the acetabulum or other reasons related to suboptimal orientation of the prosthetic. Various techniques leverage population averages of proper placement while others are amenable to patient specific refinements. 
     C. Navigation Using One or More Reference Planes with Anterior Approach 
     1. Methods for Anterior Approach 
       FIGS.  1 - 5 C  illustrate a hip navigation system  600  adapted to navigate a hip joint procedure from an anterior approach.  FIGS.  7 - 10 D  illustrate hip navigation system  700  adapted to navigate a hip joint procedure from an anterior approach. While the method is described with respect to system  600 , any systems described herein or in the following publications can be utilized: U.S. Pat. Pub. No. 2016/0242934, filed Mar. 10, 2015; U.S. Pat. Pub. No. 2014/0052149 filed Mar. 13, 2013; U.S. Pat. Pub. No. 2010/0137871 filed Sep. 10, 2009, all of which are incorporated by reference in their entirety. Anterior approach to hip replacement advantageously can be less invasive than posterior approach. In particular, the anterior approach can enable smaller incisions, less soft tissue dissection, and shorten recovery time for patients. 
     In some embodiments, the navigation system  600  is configured to locate a relevant anatomical feature to aid in proper placement of a prosthetic hip joint. In some methods, pre-operative imaging techniques are used. In some methods of use, the surgeon can use a standing or supine anteroposterior (AP) pelvic x-ray.  FIG.  21    shows standing AP radiograph taken with patient standing with feet in neutral rotation and shoulder width apart in stance. The x-ray tube-to-film distance should be 120 cm, with the crosshairs centered on the midpoint between the superior border of the pubic symphysis and a line drawn connecting the anterior superior iliac spines (ASIS). The coccyx should be centered in line with the pubic symphysis, and the iliac wings, obturator foramina and radiographic teardrops should be symmetrical in appearance. For appropriate pelvic inclination or abduction, a 1-3 cm gap should be seen between the tip of the coccyx and the superior border of the pubic symphysis. This positioning can be important for measuring the patient specific Rim Teardrop (RT) angle. 
     To obtain the patient specific Rim Teardrop (RT) angle from the AP pelvic x-ray the surgeon can complete one or more of the following steps. The surgeon can draw a line on the x-ray connecting the bottom of the teardrops. The surgeon can draw a line from the most lateral point on the rim of the acetabulum (R) on the operative side through the bottom of the teardrop (T) to the horizontal inter-teardrop line. If osteophytes are present on the rim (R), the surgeon can draw a line through the most lateral osteophyte. The surgeon can measure the angle between the inter-teardrop line and the RT line just drawn. This patient specific RT abduction angle can be an input for the system  600 ,  600 A. 
       FIG.  22    shows the patient positioning for the anterior hip approach. In the anterior hip approach, the patient should be placed in the supine position. When positioning the patient prior to surgery, the surgeon should take care to align the spine and femur of a patient in a horizontal plane parallel to the long edge of the operating table. The surgeon can verify that patient is positioned in an appropriate position, e.g., in a supine position. 
       FIG.  23    shows the system  600  adapted to navigate a hip joint procedure with reference to anatomical landmarks from an anterior approach. The system  600  can include the orientation sensing device  204 , not shown in  FIG.  23   . The system  600  can be adapted for either a posterior approach or an anterior approach. In the anterior approach, the patient is in the supine position. 
     The surgical orientation device  172  and the orientation sensing device  204  can be turned on before the procedure begins. If the system can be used in a knee or hip procedure, one method can involve a surgeon selecting a module corresponding to the hip. If the system can be used in a posterior or anterior approach, one method can involve a surgeon selecting a module corresponding to the anterior approach. The surgical orientation device  172  can include a display screen. The surgical orientation device  172  can include a user interface, such as buttons which can be depressed by the user. The display screen can confirm the communication between the surgical orientation device  172  and the orientation sensing device  204 . 
     The system  600  can be partially assembled for calibration as shown in  FIG.  12 A . In some embodiments, the first assembly  604  can be assembled. The pelvic bracket  638  can be coupled to the extension  644 , if separate components. The surgical orientation device  172  can be coupled to the mount  646 . In some techniques, the extension  670  can be coupled to the second coupler  648 . The orientation sensing device  204  can be coupled to the mount  672 . The surgical orientation device  172  and the orientation sensing device  204  form a general V-shaped configuration, similar to the orientation shown in  FIG.  12 A . The orientation sensing device  204  can be fixed in position relative to the surgical orientation device  172 . 
     The surgical orientation device  172  and the orientation sensing device  204  can be calibrated. The surgical orientation device  172  can be rested on a level horizontal surface with the display horizontal (facing up). The surgeon can hold the assemblies  604 ,  606  steady until the surgical orientation device  172  indicates completion. The orientation sensing device  204  can be rested on a level horizontal surface with the display vertical (facing user). The surgeon can hold the assemblies  604 ,  606  steady until the surgical orientation device  172  indicates completion. The surgical orientation device  172  can be rested on a level horizontal surface with the display pointed sideways (left side). The surgeon can hold the assemblies  604 ,  606  steady until the surgical orientation device  172  indicates completion. The surgical orientation device  172  can be rested on a level horizontal surface with the display horizontal (facing up) again. The surgeon can hold the assemblies  604 ,  606  steady until the surgical orientation device  172  indicates completion. Other orientations of the surgical orientation device  172  and the orientation sensing device  204  are contemplated for calibration. 
     The user can remove the required instruments and prepare the instruments for use.  FIG.  18 A  illustrates an impactor  300 A. As described herein, the impactor  300 A can include the fourth coupler  342  to couple the impactor  300 A to the orientation sensing device  204 . In some methods, any impactor can be used with the systems and methods described herein. The universal impactor adapter  350 ,  352  can provide the fourth coupler  342  to couple the impactor to the orientation sensing device  204 . In some methods of use, the orientation sensing device  204  can be coupled to the impactor  300 A. In some methods of use, the orientation sensing device  204  can be coupled to any impactor via the universal impactor adapter  350 ,  352 . The orientation sensing device  204  can determine cup angles relative to a reference plane as the impactor is moved. As described herein, the impactor  300 A can include a shell  312 A. The movement of the shell  312 A is cushioned by a plurality of spring members  340 ,  344  which are configured to absorb at least some of the shock of the impact on the impactor  300 A. The shell  312 A can include a fourth coupler  342 . This permits the orientation sensing device  204  to couple to the shell  312 A. The impactor  300 A can be configured to be modified to suit any of a plurality of hip prostheses. For example, a plurality of tip components  348  can be provided in a kit where each tip component is attachable to and detachable from a distal end of the shaft of the impactor  300 A. The acetabular shell can be threaded onto a tip component  348 . The user can select the appropriate shell adapter for the desired impactor. 
     As described herein, any impactor can be utilized. The surgeon can utilize the universal impactor adapter  350 ,  352 . The universal impactor adapter  350 ,  352  can include a fourth coupler  342 . This permits the orientation sensing device  204  to couple to the impactor. The universal impactor adapter  350 ,  352  can form any rigid connection to the impactor. While magnets and clamps are described herein, any mechanical connection between the universal impactor adapter  350 ,  352  and the impactor is contemplated. The impactor can suit any of a plurality of hip prostheses. For example, a plurality of tip components  348  can be provided in a kit where each tip component is attachable to and detachable from a distal end of the shaft of the impactor. The impactor can suit a particular hip prosthesis. The tip of the impactor can be designed to interface with a single acetabular shell. The acetabular shell can be threaded onto the impactor. The universal impactor adapter  350 ,  352  can allow any impactor to be used with the orientation sensing device  204  as described herein. 
     The user can interact with the surgical orientation device  172 . If the system can be used in either hip procedure, one method can involve a surgeon selecting a module corresponding to the right hip or the left hip. In some methods of use, the user can input a target cup abduction angle. This is the radiographic abduction angle defined as the coronal plane projection of the angle between the acetabular axis and the longitudinal axis of the body. Abduction and adduction are also used to describe movement of the limb within the coronal plane. In some methods of use, the user can input a target cup anteversion angle. This is the Radiographic Anteversion angle defined as the angle between the acetabular axis and the coronal plane. 
     The probe  678  can be calibrated. The extension  670  can be decoupled from the second coupler  648 . The second assembly  606  can be assembled as shown in  FIG.  12 B . The first assembly  604  can be coupled to the second assembly  606  as shown in  FIG.  12 B . In some methods of use, the system  600  can include a calibration fixture  690 . The first assembly  604  and the second assembly  606  can be mounted to the calibration fixture  690 . The calibration fixture can include a plurality of points for the probe  678  to contact. 
     The probe  678  can contact a center hole at the base of the calibration fixture  690  to calibrate a center point. The user can depress a button when the probe  678  is placed. The probe  678  can contact a left hole at the base of the calibration fixture  690  to calibrate a left point. The user can depress a button when the probe  678  is placed. The probe  678  can contact a right hole at the base of the calibration fixture  690  to calibrate a right point. The user can depress a button when the probe  678  is placed. The calibration fixture  690  can be utilized prior to the procedure. The calibration fixture  690  can be located away from the patient, for instance on a back table. Other calibration fixtures and jigs are contemplated. 
     The system  600  can be attached to the pelvis as shown in  FIG.  23   . The user can position the system  600  such that the system  600  has solid and stable mount for attachment of the instrumentation to the pelvis. In some methods of use, all measurements and references are based off the initial registration process and any movement of the first assembly  604  after will result in error in the resulting readouts of cup position. In some methods, the fixation pins  610 ,  612  are placed in the ipsilateral iliac crest in a parallel fashion. The fixation pins  610 ,  612  are placed in a similar fashion to placement of pins for pelvic external fixation. The fixation pins  610 ,  612  enter the iliac wing at its most superior surface and travel between the tables of the inner and outer bone of the iliac wing. 
     In order to prevent obstruction of subsequent femoral exposure and broaching with the anterior approach, in some methods of use, the most anterior fixation pin should be placed 2-4 cm posterior to the ASIS. It is also helpful to evaluate the patients pre-operative x-rays to assess the relative angle that will allow for passage of the fixation pins  610 ,  612  within the bone. The most optimal position for the fixation pins  610 ,  612  is to enter at approximately a 45 degree angle from the anterior pelvic plane to allow the pins to enter into the thicker supra-acetabular bone along the anterior column. In some methods of use, fixation pins  610 ,  612  that are passed at an angle greater than 45 degrees are at risk for exiting the cortical bone where the ilium thins more posteriorly. 
     The fixation pins  610 ,  612  are designed with a pointed tip to allow for secure placement while starting through the thicker outer cortical bone. This decreases risk of pin slippage and aberrant placement. It is also important for the user feel for any significant resistance when passing the fixation pins  610 ,  612  to an appropriate depth to avoid perforating the cortical bone. If there is concern about pin location, the user may aim more to the outer iliac wall. In some methods of use, the fixation pins  610 ,  612  can be stabilized if they are placed at least half their length into the bone. This will provide a stable construct with the mount. The fixation base  602  has been designed to allow for parallel placement with the anterior pelvic plane if the pins are placed at 45 degrees. 
     The fixation pins  610 ,  612  can be inserted into the bone. In some techniques, one or more of the fixation pins  610 ,  612  are positioned as described herein. In some techniques, one or more of the fixation pins  610 ,  612  are positioned on the iliac crest. In some techniques, one the fixation pins  610 ,  612  is positioned on the iliac crest 2-4 cm posterior to ASIS. In some techniques, the other fixation pins  610 ,  612  is positioned 2 cm posterior to the first fixation pin. The fixation base  602  can be slid over the fixation pins  610 ,  612  to the level of the skin. The fixation devices  624  of the fixation base  602  can be tightened to secure the fixation base  602  to the fixation pins  610 ,  612 . In some methods of use, the fixation base  602  must be attached prior to dislocating the hip. 
     The system  600  can be assembled as shown in  FIG.  1   . The orientation sensing device  204  can be coupled to the probe  678 . In some embodiments, the orientation sensing device  204  and/or the probe  678  include indicia such as arrows to facilitate alignment. The first assembly  604  can be secured to the fixation base  602  with the surgical orientation device  172  attached. The first assembly  604  can be secured by pushing on the lock lever  640 , as described herein. The second assembly  606  can be secured to the fixation base  602  with the orientation sensing device  204  attached. In some embodiments, the second assembly  606  and/or the fixation base  602  include indicia such as arrows to facilitate alignment. 
     The surgical orientation device  172  can be aligned with the sagittal plane. The system  600  can be placed such that the probe  678  can reach all required landmarks defining the Anterior Pelvic Plane. The fixation base  602  can be adjusted. In some methods of use, the fixation base  602  can be slid along the fixation pins  610 ,  612 . In some methods of use, angle or tilt of the fixation base  602  can be adjusted. After adjustment, the screws on the fixation base  602  can be tightened to secure the fixation base  602  to the fixation pins  610 ,  612  for the remainder of the procedure. 
     The surgeon can register a parked configuration or home position. In some techniques, the distal end  680  of the probe  678  can be engaged with a point on the fixation base  602 , such as the divot  630 . The probe  678  can be vertical in the home position. The orientation sensing device  204  can be vertical in the home position. The distal end of the probe  678  can be curved or bent to facilitate locating anatomical landmarks or points. 
     When registering points, the user can hold the probe  678  close to the distal end  680  to maximize accuracy of the measurement of the point. When interacting with the surgical orientation device  172 , the user can support the back of the surgical orientation device  172  to avoid flexing the fixation pins  610 ,  612  and/or the fixation base  602 . The user can register a point by pressing a button of the surgical orientation device  172 . If the registration is not accepted, the user can keep the probe  678  stationary and press the button again. 
     The surgeon can position the distal end  680  of the probe  678  at various anatomical landmarks or points.  FIG.  24    illustrates the anatomy of the hip. As illustrated by  FIG.  24   , two landmarks are circled. The landmarks include the two anterior superior iliac spines (ASIS) which are bony projections of the iliac bone. The anterior superior iliac spines can be visualized and/or palpitated by the user during surgery. The anterior superior iliac spine is the anterior extremity of the iliac crest of the pelvis. The inter-ASIS line extends between these landmarks. The inter-ASIS line extends between the ipsilateral ASIS and the contralateral ASIS. In other methods of use, other landmarks are used. Other landmarks that could be used include locations on the ilium, ischium, pubis, anterior insertion point of trans-acetabular ligament to the ischium, mid-point of the inferior aspect of the acetabular notch, the anterior superior iliac spine, anterior inferior iliac spine, convergence of the acetabulum and anterior inferior iliac spine, as well as the other landmarks known in the art. 
     The system  600  has one or more processors that receive(s) data and determines the relative position and/or orientation of these anatomical landmarks when the probe  678  contacts the anatomical landmark. The data can be generated by inertial sensors, as discussed elsewhere herein, or other types of sensors of the system  600 . Preferably the sensors are small enough to be mounted on or in handheld housings or embedded in the instruments, such as the surgical orientation device  172  and the orientation sensing device  204 . The system  600  preferably also has a memory device to at least temporarily store the position of these points. The system  600  preferably also has the ability to at least temporarily store the relevant position and/or orientation data when the probe  678  contacts the anatomic landmarks. In some methods of use, the system  600  records the position and/or orientation of the probe  678  when the probe  678  contacts each anatomic landmark or point. In some methods of use, the system  600  stores the recorded position and/or orientation of the probe  678  during the length of the procedure. In some methods of use, the system  600  stores the recorded position and/or orientation of the probe  678  until the system is powered off. 
       FIGS.  25 A- 25 D  illustrate method steps to calculate the Anterior Pelvic Plane. The Anterior Pelvic Plane can be defined as a plane created by the two anterior superior iliac spines (ASIS) and the anterior surface of the pubic symphysis. Three points provide adequate information to calculate a plane. The system  600  can generate the Anterior Pelvic Plane by registering Point 1, Point 2, and Point 3. These anatomical features are visible and/or palpable while the patient is in a supine position. In some methods, the probe  678  registers the Anterior Pelvic Plane with direct contact of anatomical landmarks when the patient is in the supine position. The system  600  is then able to provide the user navigation data of the orientation of a hip instrument (e.g., the impactor  300 A or any impactor with universal impactor adapter  350 ,  352 ) with respect to the Anterior Pelvic Plane. In some embodiments, the system  600  is able to provide the user navigation data in real-time. In the anterior approach, the patient is positioned on his/her back and the Anterior Pelvic Plane is oriented substantially horizontally, e.g., substantially parallel to the plane of the table on which the patient is positioned. 
       FIG.  25 A  illustrates the approximate location of three points of the Anterior Pelvic Plane. The surgeon can register Point 1, Point 2, and Point 3. The illustrated embodiment shows Point 1 on the left hip, Point 2 on the right hip, and Point 3 on the right hip. Other configurations are contemplated. For some procedures on a patient&#39;s left hip, Point 1 is on the left hip and Point 2 is on the right hip. For some procedure on a patient&#39;s right hip, Point 1 is on the right hip and Point 2 is on the left hip. Other methods are contemplated. In some methods, Point 1 is the ipsilateral ASIS. In some methods, the distal end  680  of the probe  678  is placed at the ipsilateral ASIS landmark. The probe  678  can be immobilized and the position and/or orientation of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . The surgeon can enter an input to register Point 1 (e.g., depress a button on the surgical orientation device  172 ). Other ways of entering an input include interacting with a touchscreen, using a verbal command, touching an icon, holding the probe  678  steady for a period of time, and/or reaching the end of a countdown clock, etc. The surgical orientation device  172  can indicate that Point 1 was recorded. Additionally, the distance that the probe  678  is extended, as captured by the camera  184 , to contact the ipsilateral ASIS can be recorded by the orientation device  172 . The process to record the ipsilateral ASIS can be repeated for one or more additional points. 
     In some methods, Point 2 is the contralateral ASIS. In some methods, the distal end  680  of the probe  678  is placed at the contralateral ASIS landmark. The probe  678  can be immobilized and the position and/or orientation of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . The surgeon can enter an input to register Point 2 (e.g., depress a button on the surgical orientation device  172 ). The surgical orientation device  172  can indicate that Point 2 was recorded. Additionally, the distance that the probe  678  is extended, as captured by the camera  184 , to contact the contralateral ASIS can be recorded by the orientation device  172 . The process to record the contralateral ASIS can be repeated for one or more additional points. 
     In some methods, Point 3 is the anterior surface of the pubic symphysis. In some methods, the distal end  680  of the probe  678  is placed at the pubis landmark. In some methods, either pubic tubercle may be used as Point 3. In some embodiments, the contralateral pubic tubercle is used as Point 3. The probe  678  can be immobilized and the position and/or orientation of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . The surgeon can enter an input to register Point 3 (e.g., depress a button on the surgical orientation device  172 ). The surgical orientation device  172  can indicate that Point 3 was recorded. Additionally, the distance that the probe  678  is extended, as captured by the camera  184 , to contact the pubic symphysis can be recorded by the orientation device  172 . The process to record the pubic symphysis can be repeated for one or more additional points. 
     The distance related to the extension of the probe  678  can be used in conjunction with the positional and/or orientation data from the orientation sensing device  204 . In some methods, the orientation sensing device  204  converts the image of the camera  184  into an extension measurement of the probe  678 . In some embodiments, the surgical orientation device  172  converts the image of the camera  184  into an extension measurement of the probe  678 . When registering the anatomical points, the camera  184  captures an image of the marking  682 . The camera  184  can read the marking  682  to provide accurate determination of the translational position of the probe  678  relative to the dock  662 . The camera  184  can be directly above the marking  682 . In some methods, the camera  184  can read a binary code of the marking  682 . 
     The surgical orientation device  172  can use the length measurement from the camera  184  and the data from the orientation sensing device  204  to determine the location of the distal end  680  of the probe  678 . In some embodiments, the surgeon will enter an input (e.g., depress a button) to collect data from the orientation sensing device  204 . In some methods, the surgeon will enter an input (e.g., depress a button) to collect data from the camera  184 . In some embodiments, the surgeon will enter an input (e.g., depress a button) to collect data from the orientation sensing device  204  and the camera  184  simultaneously. In some methods, the orientation sensing device  204  and/or the camera  184  will only send data if the orientation sensing device  204  is stable or non-moving. 
     Once the foregoing points of the pelvis have been navigated and the data recorded into the surgical orientation device  172 , the Anterior Pelvic Plane can be calculated from data indicating the navigated points. The system  600  can calculate the Anterior Pelvic Plane from the three points recorded by the system  600 . The three points are shown in  FIG.  12 A .  FIG.  25 B  illustrates the inter-ASIS line. The inter-ASIS line connects Point 1 and Point 2. The inter-ASIS line provides a straight line between the ipsilateral ASIS and the contralateral ASIS.  FIG.  25 C  illustrates the general horizontal direction of the Anterior Pelvic Plane. The Anterior Pelvic Plane can be considered a horizontal plane that pivots about the inter-ASIS axis depending on the location of Point 3.  FIG.  25 D  illustrates the Anterior Pelvic Plane (APP) which is determined by Point 3. The Anterior Pelvic Plane includes the ipsilateral ASIS, the contralateral ASIS, and the anterior surface of the pubic symphysis. 
     As described herein, the system  600  can determine a reference plane. The plane can be uniquely determined by any of the following: three non-collinear points, a line and non-collinear point, two distinct but intersecting lines, or two parallel lines. In some methods of use, the Anterior Pelvic Plane is calculated based on three non-collinear points. In some methods of use, the Anterior Pelvic Plane is calculated based on ipsilateral ASIS, contralateral ASIS, and the anterior surface of the pubic symphysis. In some methods of use, the orientation of the Anterior Pelvic Plane can be a baseline for placement of the cup portion of a hip prosthesis. The surgical orientation device  172  can display information with respect to the Anterior Pelvic Plane. In some methods of use, the abduction and anteversion angles in cup placement in total hip arthroplasty can be with respect to the Anterior Pelvic Plane. The Anterior Pelvic Plane is cited in literature as a valid anatomical plane to guide cup placement. In some embodiments, the Anterior Pelvic Plane is determined by the surgical orientation device  172  and/or the orientation sensing device  204 . In some embodiments, a reference frame is established by the Anterior Pelvic Plane. The Anterior Pelvic Plane reference frame is a three dimensional reference frame. The Anterior Pelvic Plane reference frame is a reference frame that contains the Anterior Pelvic Plane. In some embodiments, the surgical orientation device  172  and/or the orientation sensing device  204  can provide orientation and/or position data related to the Anterior Pelvic Plane reference frame. In some embodiments, the surgical orientation device  172  can display orientation and/or position data relative to the Anterior Pelvic Plane reference frame. 
       FIGS.  26 A- 26 D  illustrate method steps to calculate a table plane. Any method to establish the table plane described herein or incorporated by reference can be utilized. The table plane can be a horizontal or generally horizontal plane. In some techniques, the operating table is horizontal and the table plane approximates the plane of the table. In some techniques, the table plane can be oriented relative to other surface in the operating room. In some techniques, the floor is horizontal and the table plane approximates the plane of the floor. In some techniques, the wall is vertical and the table plane approximately a plane perpendicular to the wall. In some techniques, the ceiling is horizontal and the table plane approximates the ceiling. Other surfaces may be use to approximate a horizontal plane. The table registration estimates the coronal plane or frontal plane. The coronal plane is a plane that divides the body in anterior and posterior sections. The coronal plane is a horizontal reference plane when the patient is in the supine position of the anterior approach. The orientation sensing device  204  can register the operating table or perform table registration for the anterior approach. The top surface of the operating table upon which the patient is positioned is positioned horizontally. The patient can be positioned so that the coronal plane of the pelvis is level, e.g., parallel to the table and/or also horizontal. The user can visually verify the coronal plane is level or can use devices to position the patient&#39;s body to align the coronal plane with the plane of the top surface of the table. In some embodiment, a reference plane based on the plane of the top surface of the table can be input into the system  600 . 
     The table plane provides clinical value. In some techniques, the table plane can provide a secondary reference plane to the Anterior Pelvic Plane. In some embodiments, the table plane is determined completely independently of any anatomical landmarks. The table plane provides a check against gross errors from the anatomical registrations. The table plane provides a reference plane that is unaffected by pelvic tilt. The table plane provides a reference plane that is unaffected by errors in registration due to soft tissue. The table plane appears in large console navigation. The table plane is calculated based on properly aligning the probe  678 . In some methods of use, the alignment of the probe  678  can be done entirely by eye. The table plane provides a horizontal plane which may be useful for comparing the navigated cup angles to pre-operative and/or post-operative images. The pre-operative and/or post-operative images, such as x-rays, are captured within a horizontal reference plane. The table plane may provide a horizontal reference plane that approximates the horizontal reference plane of imaging techniques. 
     During table registration, the probe  678  is coupled with the orientation sensing device  204 . In some methods of use, the probe  678  and the orientation sensing device  204  are constrained. As one example, the probe  678  can be coupled with other components of the first assembly  604  and/or the second assembly  606 . In some methods of use, the system  600  is assembled, such that the first assembly  604  and the second assembly  606  are coupled to the patient via the fixation pins  610 ,  612 . There may be mechanical constraints imposed by the pivot configuration of the system  600 . 
       FIG.  26 A  illustrates the position of the probe  678  during table registration. The probe  678  is rotated and/or pivoted by the mount  658  such that the probe  678  points in a direction that is parallel to the patient&#39;s sagittal plane. The probe  678  can be extended toward the patient&#39;s foot. The probe  678  can be aligned with the long axis of the body. The probe  678  can be held substantially parallel to the plane of the table. Referring back to  FIG.  22   , the side view of the patient illustrates one line which is parallel to the table. During table registration, the probe  678  can be parallel to the table as viewed from the side. In some embodiments, the user can align the probe  678  with the horizontal. The user can visually inspect the probe  678  from one or more locations. For instance, the user can inspect the probe  678  from a top view and a side view. In some embodiments, the user can align the probe  678  with the sagittal plane. The probe  678  can be parallel with the sagittal plane or a para-sagittal plane. The sagittal plane divides the body into right and left parts. 
       FIG.  26 B  illustrates the table plane (TP) in a method of use. The probe  678  can be immobilized and the position and/or orientation of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . The user can enter an input to register the table (e.g., depress a button on the surgical orientation device  172 ). The user can interact with a user interface on the surgical orientation device  172  to signal to the surgical orientation device  172  to capture the position and/or orientation of the orientation sensing device  204 . The surgical orientation device  172  can indicate that the table plane was recorded. 
     In some embodiments, information from one or more inertial sensors is used during table registration. As described herein, the orientation sensing device  204  and the surgical orientation device  172  can include one or more inertial sensors. In some embodiments, the position and/or the orientation of one or more inertial sensors can provide data related to the table plane. The one or more inertial sensors can detect gravity and provide a vector for the down direction. The table plane is considered a horizontal plane. In some methods of use, the vector for the down direction can be used by the system to verify that the table plane is a horizontal plane. In some embodiments, only the direction of the projection of the probe  678  onto a horizontal plane is used. In some embodiments, the table plane is determined by the surgical orientation device  172 . In some embodiments, a reference frame is established by the table plane. The table reference frame is a three dimensional reference frame. The table reference frame can be determined by the orientation sensing device  204  and the surgical orientation device  172 . The table reference frame can be determined in a different way for the anterior and posterior approach. For instance, different sensors of the orientation sensing device  204  and the surgical orientation device  172  can be utilized to determine the table reference frame for the anterior and posterior approach. 
     The table plane provides an estimation of the orientation of the coronal plane. The table plane may be recorded and stored in the system  600 . The system  600  can calculate cup angles based on the table plane based on the assumption that the pelvis of the patient is correctly positioned during registration of the table plane. In some methods of use, the abduction and anteversion angles in cup placement in total hip arthroplasty can be with respect to the plane determined during table registration. 
     In some techniques, the table registration can be completed prior to dislocating the hip. The torque applied during dislocation can move pelvis away from the correct initial alignment. In some techniques, the fixation base  602  cannot be adjusted by the user after table registration. For instance, the user cannot adjust the fixation base  602  relative to the pins  610 ,  612 . The fixation base  602  remains in position for the rest of the procedure. In some techniques, the pelvic bracket  638  cannot be adjusted by the user after table registration. The pelvic bracket  638  remains in position for the rest of the procedure. In some techniques, angle of the pelvic bracket  638  relative to the fixation base  602  cannot be changed after table registration. In some techniques, the probe  678  cannot be replaced with a different probe after table registration. The same probe  678  is used for the remainder of the procedure. 
       FIGS.  26 C and  26 D  illustrate another outcome of table registration. In some methods of use, the probe  678  can be oriented at in an infinite number of angles from horizontal during table registration. For instance, when viewed from the side similar to the view of  FIG.  22   , the probe  678  may appear to be aligned with the coronal plane. However, the top view, shown in  FIG.  26 C , shows that the probe is angled relative to the sagittal plane. The user can introduce other errors based, in part, on the point of view of the user when probe  678  is positioned.  FIG.  26 D  shows the resulting table plane (TP).  FIGS.  13 B and  26 D  show two different planes calculated during table registration. In both methods of use, the probe  678  is positioned parallel to the operating table. However, the two planes are angled based on the positioning of the probe  678 . In some methods of use, there may be a potential for misalignment due to improper positioning of the probe  678 . 
       FIGS.  27 A- 27 D  illustrate method steps to calculate an Adjusted Plane (ADJUSTED).  FIG.  27 A  illustrates the inter-ASIS line. The inter-ASIS line connects Point 1 and Point 2 discussed above in connection with  FIG.  25 A . The inter-ASIS line provides a straight line between the ipsilateral ASIS and the contralateral ASIS. As described herein, Point 1 and Point 2 can be recorded by the system  600 . Point 1 and Point 2 can be recorded as part of a method to calculate the Anterior Pelvic Plane. Point 1 and Point 2 can be recorded independently from a method to calculate the Anterior Pelvic Plane. The Adjusted Plane can be calculated in addition or as an alternative to the Anterior Pelvic Plane. In some methods, Point 1 and Point 2 are used to calculate the Anterior Pelvic Plane and the Adjusted Plane. The system  200  can store Point 1 and Point 2 for the Anterior Pelvic Plane and the Adjusted Plane. In some methods, Point 1 and Point 2 are registered only once for the Anterior Pelvic Plane and the Adjusted Plane. 
     The system  600  can generate the Adjusted Plane by registering Point 1 and Point 2. These anatomical features are visible and/or palpable while the patient is in a supine position. The system  600  is then able to provide the user navigation data of the orientation of a hip instrument (e.g., the impactor  300 A or any impactor with the universal impactor adapter  350 ,  352 ) with respect to the Adjusted Plane. In some methods of use, the navigation data is provided in real-time. In the anterior approach, the patient is positioned on his/her back and the Adjusted Plane is oriented horizontally, e.g., parallel to the plane of the table on which the patient is positioned. 
       FIG.  27 A  illustrates the approximate location of two points of the Adjusted Plane. The surgeon can register Point 1 and Point 2, as described herein. In some methods, Point 1 is the ipsilateral ASIS. In some methods, the distal end  680  of the probe  678  is positioned at the ipsilateral ASIS landmark. While the probe  678  is contacting the landmark, the position and/or orientation of the orientation sensing device  204  can be transmitted to the surgical orientation device  172 . While the probe  678  is contacting the landmark, the distance that the probe  678  is extended, as measured by the camera  184 , can be transmitted to the surgical orientation device  172 . The user can enter an input to record Point 1 (e.g., depress a button on surgical orientation device  172 ). The surgical orientation device  172  can provide an indication that Point 1 was recorded, such as a visual or audial cue. 
     In some methods, Point 2 is the contralateral ASIS. In some methods, the distal end  680  of the probe  678  is placed at the contralateral ASIS landmark. In some methods, the distal end  680  of the probe  678  is positioned at the contralateral ASIS landmark. While the probe  678  is contacting the landmark, the position and/or orientation of the orientation sensing device  204  can be transmitted to the surgical orientation device  172 . While the probe  678  is contacting the landmark, the distance that the probe  678  is extended, as measured by the camera  184 , can be transmitted to the surgical orientation device  172 . The user can enter an input to record Point 2 (e.g., depress a button on surgical orientation device  172 ). The surgical orientation device  172  can provide an indication that Point 2 was recorded, such as a visual or audial cue. 
     The Adjusted Plane is found by a rotation of the Anterior Pelvic Plane about the inter-ASIS line to be perpendicular to the force of gravity. The Adjusted Plane utilizes a measurement of gravity. As described herein surgical orientation device  172  comprise one or more inertial sensors. As described herein orientation sensing device  204  comprise one or more inertial sensors. In some embodiments, inertial data from one or more inertial sensors is used to calculate the Adjusted Plane. In some embodiments, the position and/or the orientation data of one or more inertial sensors is used to calculate the Adjusted Plane. The surgical orientation device  172  and/or the orientation sensing device  204  can comprise an accelerometer, which can provide a measurement of the direction of gravity. In some embodiments, the surgical orientation device  172  and/or the orientation sensing device  204  includes a sensor to detect the direction of gravity. The surgical orientation device  172  and/or the orientation sensing device  204  can be sensitive to the direction of gravity. The one or more inertial sensors can provide a vector aligned with vertical, e.g., for the down direction. In some embodiments, the surgical orientation device  172  and/or the orientation sensing device  204  includes a three axis accelerometer to detect orientation relative to or of gravity. 
     In some embodiments, the surgical orientation device  172  includes an accelerometer. In some embodiments, the orientation sensing device  204  includes an accelerometer. The accelerometer at rest can measure the acceleration due to Earth&#39;s gravity. The accelerometer can measure the acceleration from gravity straight downward or vertically. In some embodiments, the accelerometer can detect the magnitude and direction of the force of gravity. The accelerometer can produce a vertical vector. The accelerometer can produce a horizontal vector by transforming the vertical vector (e.g., by rotation of 90 degrees). The accelerometer can provide orientation and/or position data such that the Adjusted Plane is perpendicular to the force of gravity. 
     The surgical orientation device  172  and/or the orientation sensing device  204  can provide a reference to gravitational zero. Gravitational zero, as referred to herein, refers generally to an orientation in which an axis of a 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 some methods of use, the measurement of gravity can be taken at any point during the procedure. The measurement of gravity can be taken during pre-operative calibration. The measurement of gravity can be taken during table registration. In some methods, the probe  678  is placed horizontally. The placement of the probe  678  can provide verification that the gravitational measurement is free from gross errors.  FIG.  27 B  illustrates one position of the probe  678  to calculate the direction of gravity when the probe  678  is generally horizontal. The probe  678  is rotated and/or pivoted by the mount  658  such that the probe  678  points in a direction that is parallel to the patient&#39;s sagittal plane. The probe  678  can be extended toward the patient&#39;s foot. The probe  678  can be aligned with the long axis of the body. The probe  678  can be held substantially parallel to the plane of the table. In some embodiments, the user can align the probe  678  with the horizontal. The user can visually inspect the probe  678  from one or more locations. For instance, the user can inspect the probe  678  from a top view and a side view. In some embodiments, the user can align the probe  678  with the sagittal plane. The probe  678  can be parallel with the sagittal plane or a para-sagittal plane. The sagittal plane divides the body into right and left parts. As described herein, the orientation sensing device  204  can be positioned horizontally to measure gravity. As described herein, the probe  678  coupled to the orientation sensing device  204  can be positioned horizontally or substantially horizontally to measure gravity. 
     The probe  678  can be held in position or immobilized. The position and/or orientation of the orientation sensing device  204  can be recorded by the surgical orientation device  172 . The user can enter an input when the probe  678  is positioned horizontally (e.g., depress a button on the surgical orientation device  172 ). The user can interact with a user interface on the surgical orientation device  172  to signal to the surgical orientation device  172  to capture data of the orientation sensing device  204  when the probe  678  is positioned horizontally. The surgical orientation device  172  can indicate that data was recorded. The Adjusted Plane can be calculated in addition or as an alternative to the table plane. The system  200  can store gravitational zero for calculations related to the Anterior Pelvic Plane. In some methods, gravitational zero is registered only once and utilized throughout the procedure. 
     In some methods of use, the orientation sensing device  204  can be positioned in other ways than horizontally to measure the direction of gravity. In some methods of use, the orientation sensing device  204  can measure gravity when in the home position. In some methods of use, the orientation sensing device  204  can be positioned vertically or substantially vertically to measure gravity. In some methods of use, the orientation sensing device  204  can measure gravity when contacting a point or anatomical landmark. In some methods of use, the orientation sensing device  204  can measure gravity when contacting Point 1. In some methods of use, the orientation sensing device  204  can measure gravity when contacting Point 2. In some methods of use, the orientation sensing device  204  can measure gravity when contacting a point on the femur. The point on the femur can be a mark, such as Fm described herein. The point on the femur can be a structure. The point on the femur can be an anatomical landmark. In some methods of use, the orientation sensing device  204  can measure the force of gravity at any angular orientation. In some methods of use, the orientation sensing device  204  determine a vertical vector of gravity when resting at any position. 
     In some embodiments, the surgical orientation device  172  measures gravity. The surgical orientation device  172  can provide an indication of the upward/downwards or vertical direction. The surgical orientation device  172  can produce a horizontal vector by transforming the vertical vector of gravity (e.g., by rotation of 90 degrees). In some embodiments, the surgical orientation device  172  remains stationary when measuring gravity. In some embodiments, the surgical orientation device  172  is coupled or affixed to the pelvis of the patient when measuring gravity. In some methods of use, the surgical orientation device  172  is coupled to the patient via the fixation pins  610 ,  612  when measuring gravity. In some methods of use, the surgical orientation device  172  is constrained when measuring gravity. As one example, the surgical orientation device  172  can be coupled with other components of the first assembly  604  and/or the second assembly  606 . In some embodiments, the orientation sensing device  204  and the surgical orientation device  172  both determine the direction of gravity. In some embodiments, inertial data from two or more sensors are used to measure gravity. 
       FIG.  27 C  illustrates a horizontal direction of the Adjusted Plane. The Adjusted Plane can be considered a horizontal plane that pivots about the inter-ASIS line depending on the measurement of gravity.  FIG.  27 D  illustrates the Adjusted Plane. Once the foregoing points of the pelvis have been navigated and the data recorded into the surgical orientation device  172 , the Adjusted Plane can be calculated from data indicating the navigated points and the gravity measurement. The Adjusted Plane includes the ipsilateral ASIS and the contralateral ASIS. The Adjusted Plane includes the inter-ASIS line. The system  600  can combine the horizontal vector with Point 1 and Point 2 to calculate the Adjusted Plane. In some embodiments, the Adjusted Plane can be considered a horizontal plane determined by the direction of gravity. In some embodiments, the Adjusted Plane can be considered a horizontal plane containing the inter-ASIS line. 
     As described herein, three anatomical landmarks are registered for the Anterior Pelvic Plane. The ipsilateral ASIS, the contralateral ASIS, and the pubic symphysis, as registered by the probe  678 , define the Anterior Pelvic Plane. As described herein, two anatomical landmarks are registered for the Adjusted Plane. The two landmarks define the inter-ASIS line. 
     In some embodiments, the surgical orientation device  172  can provide a corrected reference frame by transforming, e.g., by rotating the Anterior Pelvic Plane about the inter-ASIS line based on the direction of gravity. In some embodiments, the surgical orientation device  172  can rotate the Anterior Pelvic Plane about the inter-ASIS line to provide a corrected reference frame that is aligned with horizontal. The measurement of gravity enables the surgical orientation device  172  to rotate the Anterior Pelvic Plane. The measurement of gravity enables the surgical orientation device  172  to establish the Adjusted Plane. The measurement of gravity enables the surgical orientation device  172  to calculate the angle that the Anterior Pelvic Plane must rotate to be aligned with horizontal. In some embodiments, the orientation sensing device  204  can rotate the Anterior Pelvic Plane about the inter-ASIS line based on the direction of gravity. The surgical orientation device  172  and/or the orientation sensing device  204  can include hardware or software to enable the transformation of, e.g., the rotation of, the Anterior Pelvic Plane based on the direction of gravity. The one or more inertial sensors of the orientation sensing device  204  and/or the surgical orientation device  172  can provide data to determine how to transform, e.g., to rotate, a plane containing the inter-ASIS axis to be perpendicular to the force of gravity. In some methods of use, the vector for the down direction can be used by the orientation sensing device  204  and/or the surgical orientation device  172  to determine a horizontal plane containing the inter-ASIS axis. In some methods of use, inertial data related to gravity can be used by the system  600  to determine the degree in which to rotate the Anterior Pelvic Plane about the inter-ASIS axis to be horizontal. 
     The orientation of the Adjusted Plane can be a baseline for placement of the cup portion of a hip prosthesis. The surgical orientation device  172  can display information with respect to the Adjusted Plane. In some methods of use, the abduction and anteversion angles in cup placement in total hip arthroplasty can be with respect to the Adjusted Plane. In some embodiments, the Adjusted Plane is determined by the surgical orientation device  172  and/or the orientation sensing device  204 . In some embodiments, a reference frame is established by the Adjusted Plane. The Adjusted Plane reference frame is a three dimensional reference frame. The Adjusted Plane reference frame is a reference frame that contains the Adjusted Plane. In some embodiments, the surgical orientation device  172  and/or the orientation sensing device  204  can provide orientation and/or position data related to the Adjusted Plane reference frame. In some embodiments, the surgical orientation device  172  can display orientation and/or position data relative to the Adjusted Plane reference frame. 
     Once registration is complete, the user can proceed to proceed to dislocate the hip, resect the femoral head, and prepare the acetabulum. The user can prepare the impactor and shell. The user can remove the second assembly  606  from the first assembly  604 . The user can remove the orientation sensing device  204  from the probe  678 . The user can dock the orientation sensing device  204  to the first assembly  604 . The surgical orientation device  172  and the orientation sensing device  204  form a general V-shaped configuration, similar to the orientation shown in  FIG.  12 A . 
     The user can set the cup angle. The user can remove the orientation sensing device  204  from the first assembly  604 . The orientation sensing device  204  and the surgical orientation device  172  can at this point be used to guide placement of the cup in the prescribed orientation. The surgeon can remove the extension  670  from the third coupler  668 . The surgeon can couple the extension  670  to an impactor  300 A, shown in  FIG.  18 A . The surgeon can couple the extension  670  to any of the universal impactor adapters  350 ,  352  described herein. The universal impactor adapter  350 ,  352  can be utilized to mount the fourth coupler  342  to any impactor. The fourth coupler  342  can allow the orientation sensing device  204  to couple to the impactor. The impactor can be configured to be modified to suit any of a plurality of hip prostheses or the impactor can be designed to suit a particular hip prosthesis. 
     The acetabular shell can be inserted into the acetabulum and positioned at the desired angle. The surgical orientation device  172  can guide the surgeon in setting the appropriate cup angle. The surgical orientation device  172  can graphically display when the orientation sensing device  204  is navigated to the desired abduction and anteversion angles. The desired abduction and anteversion angles can be pre-operative cup angles entered by the surgeon during calibration. The surgical orientation device  172  can graphically display the abduction and anteversion angles as the orientation sensing device  204  is moved. The user can align impactor at desired cup angle. Aligning a visual indicator of the surgical orientation device  172  can guide the user to position the impactor at the desired cup angles. The abduction and anteversion angles can be displaced statically. The cup angles can be checked after impacting by repeating the proceeding steps. 
     The surgical orientation device can provide cup angles relative to any reference plane, including those described herein. The Adjusted Plane can provide several advantages over the table registration. The Adjusted Plane can increase the accuracy of the table registration. For instance, the Adjusted Plane provides a verification of the horizontal direction of the probe  678  via a measurement of gravity. For instance, the Adjusted Plane improves placement of the horizontal plane by including anatomical landmarks or points. For instance, the Adjusted Plane can include one or more anatomical locations. For instance, the Adjusted Plane can include an anatomical line. For instance, the Adjusted Plane can include the inter-ASIS line as described above. From a side view, the Adjusted Plane can look as though it is the same as the table plane. However, the Adjusted Plane includes the inter-ASIS line whereas the table plane may not always include this line. The table registration may introduce some errors in orientating the horizontal plane. There may be greater accuracy in the Adjusted Plane since it orients the plane based on anatomical landmarks and a measurement of gravity. 
     The surgical orientation device  172  can include indicia such as a target or bullseye to indicate the pre-determined abduction and anteversion angles. The surgical orientation device  172  can include indicia such as a dot or cross-hair to indicate movement of the impactor. Aligning the indicia in the center of the target or bullseye can indicate that the impactor is aligned with the predetermined cup angles. The indicia can move in real-time. The surgical orientation device  172  can include a readout of the abduction and anteversion angles. The angles can be calculated in real-time. The angles can change as the impactor is moved. The user can have a set amount of time to align the impactor with the desired cup angles. The user can enter an input once the desired cup angles are reached. In some methods, after the impactor is positioned relative to the desired cup angles, the cup angles can be displayed statically. The surgical orientation device  172  can provide information regarding the pelvis or other information dynamically. 
     After positioning the cup, the user can attach the second system  606  to the first system  604 , similar to the configuration shown in  FIG.  1   . The user can verify the home position. In some techniques, a distal end of the probe  678  can be engaged with a point on the fixation base  602 , such as divot. The probe  678  can be vertical in the home position. The orientation sensing device  204  can be vertical in the home position. The user can repeat registration if the home position has shifted. The user can end the procedure. The user can remove the system  600  prior to closure. 
     In some methods of use, the user can measure for leg length and joint offset. At the surgeon&#39;s discretion the system  600  can be used to navigate a condition, location and/or orientation of the femur prior to hip replacement. In some embodiments, a mark Fm as shown in  FIG.  24    may be made on the proximal femur. In some embodiments, a structure is attached to the femur, such as a pin. In some embodiments, a burr or detent is made in the femur. Thereafter the orientation sensing device  204  can be initialized or zeroed such as by placing it back in the home position. Thereafter, the distal end  680  of the probe  678  can be brought into contact with the femur mark Fm. The surgical orientation device  172  can be signaled to record the orientation of the orientation sensing device  204 . A distance from the point of attachment of the fixation pins  610 ,  612  to the marked position on the femur can then be recorded in the surgical orientation device  172 . The position can be based on capturing the markings  682  the probe  678  or probe inlay  676  by the camera  184 , in combination with inertial data from the orientation sensing device  204 . 
     If femoral landmark Fm is acquired in the procedure prior to separating the natural joint, the same landmark can be acquired after the prosthetic joint is placed to confirm that the replacement of the joint has not changed either the length of the leg, the off-set of the leg from the trunk of the patient or both. Thereafter, the distal end  680  of the probe  678  can be brought into contact with the same landmark (e.g., Fm) acquired early in the procedure. The orientation of the orientation sensing device  204  and the extension of the probe  678  can be input into the surgical orientation device  172 . These data enable the surgical orientation device  172  to output amounts of change in leg length and leg offset. 
     In some methods of use, the system  600  includes an optical component  174  shown in  FIG.  6 A  and/or the optical component  194  shown in  FIGS.  6 B- 6 C . In some embodiments, the optical component  174 ,  194  is a separate component. In some embodiments, the optical component  174 ,  194  is coupled to the first assembly  604 . In some embodiments, the optical component  174  can be rotated relative to the first assembly  604 , for instance by a knob  176 . The optical component  174 ,  194  can comprise one or more lasers, which can be configured to project laser light. The optical component  174 ,  194  can provide a visual guide to replicate the original position of the femur relative to the pelvis. 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. The surgeon can mark one or more points along the line of the projection of the optical component  174 ,  194 . The surgeon can complete any steps described herein. The surgeon, thereafter, can verify the one or more points are along the line of the projection of the optical component  174 ,  194 . When measuring changes in leg length and lateral joint offset, the apparent changes are sensitive to changes in the orientation of the femur relative to the pelvis. The user can reposition the femur prior to measuring the change such that the orientation of the femur relative to the pelvis is the same as that when the preoperative baseline measurement was made. 
     Another method is to measure the orientation of the femur relative to pelvis during preoperative baseline and postoperatively and then correct for changes in orientation by doing a virtual rotation about the postoperative center of rotation of the femur. The method may require obtaining three points of the femur. The three points on the femur can be marks or anatomical landmarks. The three points can be on a femur plate. The three points on the femur or femur plate may be registered by the probe  678  to resolve for the femur orientation preoperatively and then postoperatively each time the leg length is to be measured. 
     2. Adjusted Plane and Anterior Pelvic Plane Comparison 
       FIG.  28 A  illustrates a side view of the Anterior Pelvic Plane. The Anterior Pelvic Plane includes the inter-ASIS line as described herein.  FIG.  28 B  illustrates a comparison between the Anterior Pelvic Plane and the Adjusted Plane.  FIGS.  28 A- 1  and  28 B- 1    illustrate another side view of the system where in the ASIS are aligned.  FIG.  28 B  illustrates a side view of the Anterior Pelvic Plane and the Adjusted Plane.  FIG.  28 C  illustrates a top view of the Anterior Pelvic Plane and the Adjusted Plane. As described herein, the Anterior Pelvic Plane and the Adjusted Plane both contain the inter-ASIS line. The Anterior Pelvic Plane also contains Point 3 to define the plane. The Adjusted Plane utilizes the direction of gravity to define the plane. In some embodiments, the Anterior Pelvic Plane and the Adjusted Plane are coaxial about the inter-ASIS line as shown in  FIGS.  28 B and  28 B- 1   . The Adjusted Plane is a rotation of the Anterior Pelvic Plane about the inter-ASIS line. The Adjusted Plane and the Anterior Pelvic Plane can form an angle alpha as shown in  FIGS.  28 B and  28 B- 1   . The angle alpha can be a measurement of pelvic tilt. The angle alpha can measure the difference to horizontal from the Anterior Pelvic Plane. The angle alpha can adjust the Anterior Pelvic Plane such that the cup angles more closely match those shown in post-operative x-rays. In some embodiments, the Adjusted Plane adjusts for tilt. In some embodiments, the Adjusted Plane adjusts for tilt of the pubis relative to the inter-ASIS line. 
     The Adjusted Plane has clinical value. The pre-operative and post-operative x-rays produce two-dimensional images on a horizontal plane. The image receptor is positioned horizontally relative to the patient in the supine position. The image receptor captures the remnant beam as the beam exits the body of the patient. The anatomy of the patient is projected onto the horizontal plane of the image receptor. For pelvis x-rays, the routine projection is an anterior-posterior projection. The navigate angles can be correlated to the view of the post-operative x-ray via the Adjusted Plane. The Adjusted Plane may provide a horizontal reference plane that approximates the horizontal reference plane of imaging techniques. There is a clinical benefit in providing users with navigated cup angles during a procedure that will reflect those measured on post-operative x-rays. The navigated cup angles based on the Adjusted Plane can be provided in addition, or as a substitute to those based on the Anterior Pelvic Plane. The navigated cup angles based on the Adjusted Plane can be provided in addition, or as a substitute to those based on the table plane. 
     The adjustment from the Anterior Pelvic Plane to the Adjusted Plane can provide the user with cup angles that correlate to clinically expected cup angles. The adjustment from the Anterior Pelvic Plane to the Adjusted Plane can provide the user with cup angles that correlate to what they expect to see during surgery (e.g., a comparison between the image of the cup and the output of the system  600 ). The adjustment from the Anterior Pelvic Plane to the Adjusted Plane can provide the user with cup angles that correlate to what they expect to see on post-operative images (e.g., a comparison between the output of the system  600  and post-operative images). The user, such as a surgeon, correlates the output of the system  600  with numbers that correlate to clinical experience, e.g., calibrated to what they expect to see in post-operative images. The post-operative images can be 6 week post-operative supine films. The post-operative images are taken from a horizontal cross-section of the patient&#39;s body. The Adjusted Plane may be more similar to the plane of the post-operative images. 
     Before navigation systems, such as system  600 , surgeons did not take measurements intra-operatively. Rather, surgeons typically looked at the cup placement during a procedure and determined whether current cup placement looked like previous cup placements. The surgeon would visually confirm cup placements during surgery and past experience in viewing post-operative images. The user would determine if the current cup placement was likely to correlate to the correct abduction and anteversion angles post-operatively. The surgeon would look at the cup placement and determine that the placement looks like 40 degrees×15 degrees based on their experience looking at post-operative images. The surgeon&#39;s confidence in the procedure would be based on their correlation of cup placement and post-operative images. 
     For the system  600 , the user is provided with an output that assists a user to navigate to proper cup placement. The output can be abduction and anteversion angles displayed on the surgical orientation device  172 . The user can navigate to the desired abduction and anteversion angles by moving components of the system  600 , such as the impactor. When the user places the cup at the desired abduction and anteversion angles, the user wants to see the same or similar angle on post-operative images. The user&#39;s confidence in the navigation of the system  600  increases if the abduction and anteversion angles produced by the system  600  match the post-operative images. 
     The Adjusted Plane can be an improvement over a landmark-only reference plane, such as the Anterior Pelvic Plane, for some patients. In some embodiments, the Anterior Pelvic Plane may differ from the horizontal reference plane of imaging techniques due to patient specific factors. For instance, pelvic tilt may orient the Anterior Pelvic Plane at an angle from the horizontal reference plane of imaging techniques. For instance, the patient&#39;s high body mass index may impact the ability to contact anatomical landmarks. For instance, the anatomical features of the reference points may not be visible and/or palpable while the patient is in a supine position. For instance, the ipsilateral ASIS, the contralateral ASIS, and/or the pubic symphysis may not be visible and/or palpable. The patient specific factors can results in differences between navigated cup angles from the Anterior Pelvic Plane and angles measured post-operatively. In some methods of use, with some patients, the Anterior Pelvic Plane may not provide abduction and anteversion angles that match post-operative images. 
     The Adjusted Plane can be an improvement over a table plane-only reference frame for procedures. In some embodiments, the table plane may differ from the horizontal reference plane of imaging techniques. The user may introduce errors in the table plane by improper placement of the probe  678 . In some methods of use, with some patients, the table plane may not provide abduction and anteversion angles that match post-operative images. 
     In some methods of use, two or more reference planes can be provided, e.g., any combination of the Adjusted Plane, the table plane, the horizontal plane and the Anterior Pelvic Plane. Any of the foregoing combinations of the reference planes provides redundancy that ensures that the angle information provided to the user is accurate and reliable such that the procedures performed will be better contained within an acetabular cup “safe zone”. 
     Systems and methods described herein can improve prosthetic hip joint placement using navigation in combination of pre-operative imaging and landmark referencing. These hip procedures generally guide a prosthetic hip to an orientation within the acetabulum that minimizes the chance of dislocation due to impingement of the femoral neck on the cup or on bones around the acetabulum or other reasons related to suboptimal orientation of the prosthetic. Various techniques leverage population averages of proper placement while others are amenable to patient specific refinements. 
     3. Pelvis Tracking 
       FIG.  29    shows a screen display for a hip method generated by one embodiment of the interactive user interface of the surgical orientation device  172 . Once the orientation sensing device  204  is attached to the impactor  300 A or any other impactor coupled to the universal impactor adapter  350 ,  352 , the surgical orientation device  172  can display radiographic abduction and anteversion angles of impactor relative to a reference plane. The reference plane can be any plane including a frontal pelvic plane, the Anterior Pelvic Plane, the table plane, the Adjusted Plane, etc. The surgical orientation device  172  can display abduction and anteversion angles relative to two or more planes. In the illustrated embodiment, the surgical orientation device  172  can display radiographic abduction and anteversion angles relative to the Anterior Pelvic Plane. The surgical orientation device  172  displays “Pelvis” angles relative to the Anterior Pelvic Plane. The Anterior Pelvic Plane is based on inputs from the anatomic landmarks. In the illustrated embodiment, the surgical orientation device  172  can display radiographic abduction and anteversion angles relative to the Adjusted Plane. The surgical orientation device  172  displays “Adjusted” angles relative to the Adjusted Plane. The Adjusted Plane is a reference plane where the Anterior Pelvic Plane is rotated about the inter-ASIS axis until its superior-inferior axis is parallel to the level table. This effectively adjusts for pelvic tilt. The “Adjusted” angles may correlate with post-operative x-rays which use a horizontal plane. 
     The surgical orientation device  172  can display additional information for the user. For instance, the surgical orientation device  172  can display information related to the position and orientation of the pelvis. As described herein, the surgical orientation device  172  can be coupled to the pelvis such that the surgical orientation device  172  can measure changes in the pelvis. The surgical orientation device  172  can include one or more inertial sensors that can track the position of the pelvis during the procedure. The surgical orientation device  172  can display the change in positioning of the pelvis in real time. The surgical orientation device  172  can provide an indicia if the position of the pelvis has changed beyond a threshold, for instance by a visual or audial cue. 
     The surgical orientation device  172  can track pelvic tilt. The tilt of the pelvis can be displayed dynamically on the surgical orientation device  172 .  FIGS.  30 A- 30 C  illustrate the tilt of the pelvis. At the start of the procedure, the pelvis may be ideally positioned. However, the pelvis can shift through the rigors of the procedure. The surgical orientation device  172  can provide information about where the pelvis is relative to the rest of the body. The surgical orientation device  172  can indicate pelvic tilt from a neutral position. The surgical orientation device  172  can indicate a posterior tilt or an anterior tilt. The surgical orientation device  172  can track the pelvis throughout the surgical procedure. 
     The surgical orientation device  172  can track pelvic rotation. The rotation of the pelvis can be displayed dynamically on the surgical orientation device  172 .  FIGS.  31 A- 31 C  illustrate the rotation of the pelvis. The surgical orientation device  172  can indicate a pelvic rotation. The surgical orientation device  172  can include one or more sensors to provide an output. The surgical orientation device  172  can track the pelvis at the pelvis moves during the procedure. The surgical orientation device  172  can graphically display when the pelvis is located at neutral rotation. For instance, the neutral rotation can be recorded by the surgical orientation device  172  at the beginning of a procedure when the pelvis is ideally placed. 
     Referring back to  FIG.  29   , the screen display of the surgical orientation device  172  can indicate pelvic tilt. In the illustrated embodiment, pelvic tilt is shown as a measurement of an angle. The screen display of the surgical orientation device  172  can indicate pelvic rotation. In the illustrated embodiment, pelvic tilt is shown as a measurement of an angle. 
     The surgical orientation device  172  can include indicia such as a target or bullseye to indicate when the pelvic tilt and pelvic rotation are neutral. In the illustrated embodiment, pelvic tilt can be along the Y-axis or vertical axis of the bullseye. In the illustrated embodiment, pelvic rotation can be along the X-axis or horizontal axis of the bullseye. The surgical orientation device  172  can include indicia such as a dot to indicate the degree of pelvic tilt and rotation. The indicia can move in real-time. As the degree of pelvic tilt increases, the indicia can move further away from the origin or center of the bullseye. As the degree of pelvic tilt decrease, the indicia can move closer to the origin or center of the bullseye. As the degree of pelvic rotation increases, the indicia can move further away from the origin or center of the bullseye. As the degree of pelvic rotation decrease, the indicia can move closer to the origin or center of the bullseye. The indicia can assist the user in understanding the alignment of the pelvis. The indicia can assist the user in positioning the pelvis. For instance, the user can reposition the pelvis during surgery to a neutral position, such as a position having neutral tilt and/or neutral rotation. 
     Referring back to  FIG.  28 C , the Adjusted Plane can be provided by transforming, e.g., by rotating the Anterior Pelvic Plane to correct for pelvic tilt. The Adjusted Plane can rotate the Anterior Pelvic Plane about the inter-ASIS line to correct for anterior tilt or posterior tilt. The transformation between the Anterior Pelvic Plane and the Adjusted Plane accounts for tilt of the patient&#39;s pelvis. The transformation between the Anterior Pelvic Plane and the Adjusted Plane accounts for pelvic tilt due to the location of the pubic symphysis. The Adjusted Plane rotates a location corresponding to the pubic symphysis in the Anterior Pelvic Plane from the position in which the pubic symphysis was probed to a horizontal location. 
     Referring to  FIGS.  31 A- 31 C , pelvic rotation corresponds to the relative location of the ipsilateral ASIS and the contralateral ASIS. Regardless of pelvic rotation, the inter-ASIS line connects the ipsilateral ASIS and the contralateral ASIS. The Adjusted Plane and the Anterior Pelvic Plane both contain the inter-ASIS line. 
     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 this application extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. In addition, while a number of variations of the inventions have been shown and described in detail, other modifications, which are within the scope of the 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 may be made and still fall within the scope of the application. For example, the application contemplates the connection hub alone or in combination with any of the other modules could comprise a separate aspect. Or, any one or a combination of the modules could be directly connected to an umbrella hub or overhead support to form another separate aspect. Accordingly, 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 embodiments. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow. 
     Similarly, this method of disclosure, is not to be interpreted as reflecting an intention that any claim require more features than are expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment.