Patent Publication Number: US-2023149184-A1

Title: System for preparing a patient?s tibia in an orthopaedic joint replacement procedure

Description:
This application is a continuation of U.S. patent application Ser. No. 16/701,880, now U.S. Pat. No. 11,497,620, which was filed on Dec. 3, 2019, which is a continuation of U.S. patent application Ser. No. 15/598,624, now U.S. Pat. No. 10,492,799, which was filed on May 18, 2017, which claims priority under 35 U.S.C. § 119 to U.S. Patent Application Ser. No. 62/338,284, filed May 18, 2016, and having the title “SYSTEM AND METHOD FOR PREPARING A PATIENT&#39;S TIBIA IN AN ORTHOPAEDIC JOINT REPLACEMENT PROCEDURE,” the entireties of each of which are hereby incorporated by reference. 
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     Cross reference is made to U.S. Patent Application Ser. No. 62/338,276 entitled “SYSTEM AND METHOD FOR PREPARING A PATIENT&#39;S FEMUR IN AN ORTHOPAEDIC JOINT REPLACEMENT PROCEDURE;” and U.S. Patent Application Ser. No. 62/338,468 entitled “SYSTEM AND METHOD FOR PREPARING A PATIENT&#39;S BONE TO RECEIVE A PROSTHETIC COMPONENT,” each of which is assigned to the same assignee as the present application, each of which is filed concurrently herewith, and each of which is hereby incorporated by reference. 
     Cross reference is made to U.S. patent application Ser. No. 15/598,622, now U.S. Pat. No. 10,470,898, entitled “ORTHOPAEDIC INSTRUMENT SYSTEM FOR SURGICALLY-PREPARING A PATIENT&#39;S TIBIA;” and U.S. patent application Ser. No. 15/598,626, now U.S. Pat. No. 10,470,899, entitled “METHOD FOR PREPARING A PATIENT&#39;S TIBIA IN AN ORTHOPAEDIC JOINT REPLACEMENT PROCEDURE,” each of which is assigned to the same assignee as the present application, each of which is filed concurrently herewith, and each of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to an orthopaedic prosthesis system, including prosthetic components and instruments for use in the performance of an orthopaedic joint replacement procedure, and more particularly to orthopaedic prosthetic components and surgical instruments for use in the performance of a knee replacement procedure. 
     BACKGROUND 
     Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. For example, in a total knee arthroplasty surgical procedure, a patient&#39;s natural knee joint is partially or totally replaced by a prosthetic knee joint or knee prosthesis. A typical knee prosthesis includes a tibial tray, a femoral component, and a polymer insert or bearing positioned between the tibial tray and the femoral component. The tibial tray generally includes a plate having a stem extending distally therefrom, and the femoral component generally includes a pair of spaced apart condylar elements, which include surfaces that articulate with corresponding surfaces of the polymer bearing. The stem of the tibial tray is configured to be implanted in a surgically-prepared medullary canal of the patient&#39;s tibia, and the femoral component is configured to be coupled to a surgically-prepared distal end of a patient&#39;s femur. 
     From time-to-time, a revision knee surgery may need to be performed on a patient. In such a revision knee surgery, the previously-implanted knee prosthesis, sometimes referred to a “primary knee prosthesis,” is surgically removed and a replacement or revision knee prosthesis is implanted. In some revision knee surgeries, all of the components of the primary knee prosthesis, including, for example, the tibial tray, the femoral component, and the polymer bearing, may be surgically removed and replaced with revision prosthetic components. In other revision knee surgeries, only part of the previously-implanted knee prosthesis may be removed and replaced. 
     During a revision knee surgery, the orthopaedic surgeon typically uses a variety of different orthopaedic surgical instruments such as, for example, cutting blocks, surgical reamers, drill guides, prosthetic trials, and other surgical instruments to prepare the patient&#39;s bones to receive the knee prosthesis. Other orthopaedic surgical instruments such as trial components may be used to size and select the components of the knee prosthesis that will replace the patient&#39;s natural joint. Trial components may include a femoral trial that may be used to size and select a prosthetic femoral component, a tibial tray trial that may be used to size and select a prosthetic tibial tray, and a stem trial that may be used to size and select a prosthetic stem component. 
     SUMMARY 
     An orthopaedic joint replacement system is shown and described. The system includes a number of prosthetic components configured to be implanted into a patient&#39;s knee. The system also includes a number of surgical instruments configured for use in preparing the bones of the patient&#39;s knee to receive the implants. A method or technique for using the surgical instruments to prepare the bones is also disclosed. 
     According to one aspect of the disclosure, an orthopaedic surgical instrument system includes a surgical reamer including an elongated shaft and a plurality of cutting flutes defined at a distal end of the elongated shaft. An attachment base includes a housing including a main body, an elongated bore that is sized to receive the elongated shaft of the reamer and extends along a longitudinal axis of the main body, and a rail extending from the main body orthogonal to the longitudinal axis. A locking knob is secured to the housing and has a longitudinal bore aligned with the elongated bore of the housing that is sized to receive the elongated shaft of the reamer. The locking knob is rotatable between a first position in which the attachment base is permitted to slide along the elongated shaft of the surgical reamer and a second position in which the attachment base is locked into position on the elongated shaft of the surgical reamer. A mounting frame is positioned on the rail. The mounting frame is configured to slide relative to the housing along the rail. A cutting block is removably coupled to the mounting frame. The locking knob is operable to advance a section of the housing into engagement with the reamer when rotated to the second position. 
     In some embodiments, the housing of the attachment base may have a retaining flange configured to engage an inner rib of the locking knob to secure the locking knob to the housing. In some embodiments, the housing of the attachment base may have an upper shaft extending outwardly from the main body along the longitudinal axis. The upper shaft may have a plurality of outer threads and the retaining flange. The locking knob may have a plurality of inner threads configured to engage the plurality of outer threads of the upper shaft. In some embodiments, the locking knob may be moveable along the longitudinal axis between an engaged position in which the plurality of inner threads are engaged with the plurality of outer threads of the upper shaft and a disengaged position in which the plurality of inner threads are spaced apart from the plurality of outer threads of the upper shaft. In some embodiments, the upper shaft may have a plurality of beams that extend along the longitudinal axis. Each beam may be spaced apart from an adjacent beam by an elongated slot. The retaining flange may have a plurality of retaining flanges. Each retaining flange may extend from a tip of each beam. In some embodiments, each beam may have a ramped upper surface. The locking knob may have an annular rib having a conical lower surface that may be configured to engage the ramped upper surface of each beam to advance the beams into engagement with the elongated shaft of the surgical reamer. 
     In some embodiments, the mounting frame may have a locking mechanism that may be operable to selectively secure the mounting frame in a position along the rail. In some embodiments, the mounting frame may have a second locking mechanism that may be operable to removeably couple the cutting block to the mounting frame. 
     In some embodiments, the rail may have a planar outer surface. The mounting frame may have a planar inner surface that corresponds to and engages the planar outer surface of the rail to prevent the mounting frame from rotating about the rail. In some embodiments, the cutting block may have a plurality of cutting guides sized for insertion of a cutting tool during resection of the patient&#39;s tibia. In some embodiments, an alignment guide plate may be sized to be received in one of a plurality of cutting guides of the cutting block to assess a resection of the patient&#39;s tibia. 
     According to another aspect of the disclosure, an orthopaedic surgical instrument system includes a housing including a main body, an elongated bore that is sized to receive an elongated shaft of a surgical reamer and that extends along a longitudinal axis of the main body, and a rail extending from the main body orthogonal to the longitudinal axis. A locking knob is secured to the housing and has a bore aligned with the elongated bore of the housing that is sized to receive the elongated shaft of the reamer. The locking knob is rotatable between a first position in which the elongated bore of the housing includes an opening having a first diameter and a second position in which the opening of the elongated bore has a second diameter that is less than the first diameter to lock the housing into position on the elongated shaft of the surgical reamer. 
     In some embodiments, the housing may have an upper shaft extending outwardly from the main body along the longitudinal axis. The upper shaft may have a plurality of outer threads and define the opening. The locking knob may have a plurality of inner threads configured to engage the plurality of outer threads of the upper shaft. In some embodiments, the locking knob may be moveable along the longitudinal axis between an engaged position in which the plurality of inner threads are engaged with the plurality of outer threads of the upper shaft and a disengaged position in which the plurality of inner threads are spaced apart from the plurality of outer threads of the upper shaft. In some embodiments, the upper shaft may have a plurality of beams that extend along the longitudinal axis. Each beam may be spaced apart from an adjacent beam by an elongated slot and may have a ramped upper surface. The locking knob may have an annular rib having a conical lower surface that may be configured to engage the ramped upper surface to cause the beams to decrease the opening from the first diameter to the second diameter. 
     In some embodiments, a mounting frame may be positioned on the rail. The mounting frame may be configured to slide relative to the housing along the rail and may have a bracket sized to receive a cutting block. In some embodiments, the mounting frame may have a locking mechanism that may be operable to selectively secure the mounting frame in a position along the rail. In some embodiments, a cutting block may be removably coupled to the mounting frame. 
     In some embodiments, the rail may have a planar outer surface. The mounting frame may have a planar inner surface that corresponds to and engages the planar outer surface of the rail to prevent the mounting frame from rotating about the rail. 
     According to yet another aspect of the disclosure, an orthopaedic surgical instrument system includes a first surgical reamer including an elongated shaft and a plurality of cutting flutes defined at a distal end of the elongated shaft. A tibial base plate includes a central opening extending along a first longitudinal axis and a pair of fixation bores. An offset guide includes an upper drum, a lower plate sized to be positioned in the central opening of the tibial base plate, and a bore extending through the offset guide along a second longitudinal axis that is offset from the first longitudinal axis of the tibial base plate when the offset guide is positioned on the tibial base plate. The bore is sized to receive the elongated shaft of the surgical reamer. A reamer guide body has a passageway defined therein that is configured to be substantially aligned with the central opening of the tibial base plate when the reamer guide body is positioned on the tibial base plate. The reamer guide body also includes a pair of fixation pins. Each of the fixation pins extends downwardly from the bottom surface of the guide body and is sized to be received in and extend outwardly from each of the fixation bores of the tibial base plate when the guide body is positioned on the tibial base plate. The offset guide is operable to rotate such that the lower plate of the offset guide engages the tibial base plate to rotate the tibial base plate about the second longitudinal axis. 
     In some embodiments, the offset guide may have a conical inner surface that defines the bore. The conical inner surface may extend from an upper opening to a lower opening smaller than the upper opening. In some embodiments, the offset guide may have a plurality of offset guides. Each offset guide may have a second longitudinal axis offset from the first longitudinal axis of the tibial base plate by a distance different from the offsets of the other offset guides. In some embodiments, the distance of one offset guide may be equal to zero millimeters. 
     In some embodiments, a second surgical reamer may be sized to extend through the passageway of the reamer guide body. The second surgical reamer may have an elongated shaft and a plurality of cutting flutes defined at a distal end. The plurality of cutting flutes may define a distal frustoconical cutting section, a proximal cutting section having a first diameter, and a cylindrical middle cutting section having a second diameter smaller than the first diameter. 
     In some embodiments, a second tibial base plate may have a central opening and a pair of slots extending outwardly from the central opening. A punch instrument may have a pair of arms sized to be positioned in the pair of slots of the second tibial base plate. Each arm may have a plurality of cutting teeth. In some embodiments, an impaction handle may have a locking flange configured to pivot between a locked position and an unlocked position. The punch instrument may have a plate configured to engage the locking flange when the locking flange is in the locked position. In some embodiments, the impaction handle may have a proximal post extending along a longitudinal axis. The impaction handle may have a bracket coupled to the proximal post and operable to move along the longitudinal axis relative to the post. The bracket may have an elongated slot defined therein. The impaction handle may have a lever arm that may be pivotally coupled to the proximal post. The lever arm may have the locking flange and a tab positioned in the elongated slot defined in the bracket. When the bracket is moved in a distal direction along the longitudinal axis, the tab may be advanced along the elongated slot and the lever arm may be pivoted from the locked position to the unlocked position. In some embodiments, a biasing element may be operable to bias the lever arm in the locked position. 
     In some embodiments, an attachment device may be configured to be secured to the elongated shaft of the first surgical reamer. A tibial cutting block may be configured to be coupled to the attachment device. 
     According to an aspect of the disclosure, an orthopaedic surgical instrument system includes a first surgical reamer including an elongated shaft and a plurality of cutting flutes defined at a distal end of the elongated shaft. A tibial base plate includes a central opening extending along a first longitudinal axis and a pair of fixation bores. An offset guide includes an upper drum, a lower plate sized to be positioned in the central opening of the tibial base plate, and a bore extending through the offset guide along a second longitudinal axis that is offset from the first longitudinal axis of the tibial base plate when the offset guide is positioned on the tibial base plate. The bore is sized to receive the elongated shaft of the surgical reamer. An attachment device is configured to be secured to the elongated shaft of the first surgical reamer. The attachment device includes a locking knob sized receive the elongated shaft of the first surgical reamer. A tibial cutting block is configured to be coupled to the attachment device. The tibial cutting block includes a cutting slot sized to receive a cutting tool to surgically-prepare a patient&#39;s tibia to receive the tibial base plate. The locking knob may be operable to advance a section of the attachment device into engagement with the first surgical reamer to lock the attachment device position on the elongated shaft of the first surgical reamer. 
     In some embodiments, a second tibial base plate may have a central opening and a pair of slots extending outwardly from the central opening. A punch instrument may have a pair of arms sized to be positioned in the pair of slots of the second tibial base plate. Each arm may have a plurality of cutting teeth. 
     In some embodiments, an impaction handle may have a locking flange configured to pivot between a locked position and an unlocked position. The punch instrument may have a plate configured to engage the locking flange when the locking flange is in the locked position. In some embodiments, the impaction handle may have a proximal post extending along a longitudinal axis. The impaction handle may have a bracket coupled to the proximal post and operable to move along the longitudinal axis relative to the post. The bracket may have an elongated slot defined therein. The impaction handle may have a lever arm that may be pivotally coupled to the proximal post. The lever arm may have the locking flange and a tab positioned in the elongated slot defined in the bracket. When the bracket is moved in a distal direction along the longitudinal axis, the tab may be advanced along the elongated slot and the lever arm may be pivoted from the locked position to the unlocked position. In some embodiments, a biasing element may be operable to bias the lever arm in the locked position. 
     In some embodiments, a reamer guide body may have a passageway defined therein that may be configured to be substantially aligned with the central opening of the tibial base plate when the reamer guide body is positioned on the tibial base plate. In some embodiments, a second surgical reamer may be sized to extend through the passageway of the reamer guide body. The second surgical reamer may have an elongated shaft and a plurality of cutting flutes defined at a distal end. The plurality of cutting flutes may define a distal frustoconical cutting section, a proximal cutting section having a first diameter, and a cylindrical middle cutting section having a second diameter smaller than the first diameter. 
     According to another aspect of the disclosure, a method of preparing a patient&#39;s tibia for a tibial prosthetic component includes inserting a surgical reamer into a cavity formed in a proximal end of a patient&#39;s tibia. The method also includes coupling an attachment device to an elongated shaft of the reamer such that the elongated shaft extends through a bore of a locking knob and a bore of a housing of the attachment device. The method also includes rotating the locking knob about the elongated shaft such that to compress a section of the housing engages the elongated shaft of the reamer. The method also includes coupling a mounting frame to a rail extending from the housing at an orthogonal angle with respect to the longitudinal axis. The method also includes coupling a cutting block to the mounting frame. The method also includes advancing a saw blade through a cutting guide formed in the cutting block to cut the proximal end of the patient&#39;s tibia. 
     In some embodiments, rotating the locking knob may require advancing a bottom surface of the locking knob toward a shoulder surface of the housing. In some embodiments, rotating the locking knob may require advancing a plurality of beams of the housing into engagement with the elongated shaft of the surgical reamer. In some embodiments, rotating the locking knob may require advancing an annular rib of the locking knob into engagement with a ramped upper surface of each of the plurality of beams to advance the plurality of beams of the housing into engagement with the elongated shaft of the surgical reamer. In some embodiments, rotating the locking knob may require engaging a threaded inner surface of the locking knob with a threaded outer surface of each of the plurality of beams. 
     In some embodiments, rotating the locking knob may require gripping an angled outer surface of the locking knob. In some embodiments, the method may require operating a locking mechanism to selectively secure the mounting frame to the rail. In some embodiments, the method may require inserting the rail into a bore extending through the mounting frame such that the mounting frame moves longitudinally on the mounting post to position the cutting block relative the patient&#39;s tibia. In some embodiments, the method may require engaging a planar outer surface of the mounting post with a planar inner surface of the bore of the mounting frame to prevent the mounting frame from rotating about the mounting post. 
     In some embodiments, the method may require removing the attachment device, the mounting frame, and the cutting block from the patient&#39;s tibia. The method may require positioning a tibial base plate on the proximal end of the patient&#39;s tibia such that the elongated shaft of the surgical reamer extends through a central opening of the tibial base plate. The method may require advancing an end of the elongated shaft into a bore defined in an offset guide, wherein the bore extends along a longitudinal axis that may be spaced apart from a longitudinal axis of the central opening. The method may require positioning the offset guide within the central opening of the tibial plate. The method may require rotating the offset guide to rotate the tibial plate relative a proximal end of the patient&#39;s tibia. The method may require determining an offset orientation of a tibial prosthetic component based on the orientation of the tibial plate relative to the proximal end of the patient&#39;s tibia. 
     In some embodiments, the method may require removing the offset guide and the surgical reamer from the patient&#39;s tibia. The method may require positioning a reamer guide body on the tibial base plate. The method may require inserting a second surgical reamer into the reamer guide body. The second surgical reamer may have a plurality of cutting flutes that define (i) a distal frustoconical cutting section, (ii) a proximal cutting section having a first diameter, and (iii) a cylindrical middle cutting section having a second diameter smaller than the first diameter. 
     In some embodiments, the method may require advancing a drill stop along an elongated shaft of the second surgical reamer. In some embodiments, inserting the second surgical reamer into the reamer guide body may require advancing the second surgical reamer into the patient&#39;s tibia and using the drill stop to determine a maximum reaming depth. 
     In some embodiments, the method may require removing the offset guide from the surgical reamer, wherein the offset guide may be a first offset guide of a plurality of offset guides. The method may require selecting a second offset guide of the plurality of offset, wherein the second offset guide has a second bore. The method may require advancing an end of the elongated shaft into the second bore of the second offset guide, wherein the second bore extends along a second longitudinal axis that may be spaced apart from the longitudinal axis of the central opening by an amount different from longitudinal axis of the first offset guide. The method may require rotating the second offset guide to rotate the tibial plate relative a proximal end of the patient&#39;s tibia to determine the offset orientation. 
     According to yet another aspect of the disclosure, a method of preparing a patient&#39;s tibia for a tibial prosthetic component includes inserting a first surgical reamer into a cavity formed in a proximal end of a patient&#39;s tibia. The method also includes positioning a tibial base plate on the proximal end of the patient&#39;s tibia such that the elongated shaft of the first surgical reamer extends through a central opening of the tibial base plate. The method also includes advancing an end of the elongated shaft into a bore defined in an offset guide, wherein the bore extends along a longitudinal axis that may be spaced apart from a longitudinal axis of the central opening. The method also includes positioning the offset guide within the central opening of the tibial plate. The method also includes rotating the offset guide to rotate the tibial base plate relative a proximal end of the patient&#39;s tibia. The method also includes determining an offset orientation of a tibial prosthetic component based on the orientation of the tibial plate relative to the proximal end of the patient&#39;s tibia. The method also includes removing the offset guide and the first surgical reamer from the patient&#39;s tibia. The method also includes positioning a reamer guide body on the tibial base plate. The method also includes inserting a second surgical reamer into the reamer guide body, wherein the second surgical reamer includes a plurality of cutting flutes that define (i) a distal frustoconical cutting section, (ii) a proximal cutting section having a first diameter, and (iii) a cylindrical middle cutting section having a second diameter smaller than the first diameter. 
     In some embodiments, the method may require positioning a depth stop on the elongated shaft of the second surgical reamer. The depth stop may have a moveable flange sized to be separately received in an aperture defined in the elongated shaft of the second surgical reamer. The method may require actuating a user-operated button of the depth stop to engage the flange with the annular slot. 
     In some embodiments, the method may require removing the offset guide from the surgical reamer, wherein the offset guide may be a first offset guide of a plurality of offset guides. The method may require selecting a second offset guide of the plurality of offset, wherein the second offset guide has a second bore. The method may require advancing an end of the elongated shaft into the second bore of the second offset guide, wherein the second bore extends along a second longitudinal axis that may be spaced apart from the longitudinal axis of the central opening by an amount different from longitudinal axis of the first offset guide. The method may require rotating the second offset guide to rotate the tibial plate relative a proximal end of the patient&#39;s tibia to determine the offset orientation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description particularly refers to the following figures, in which: 
         FIG.  1    is an exploded perspective view of prosthetic components of an orthopaedic joint replacement system; 
         FIG.  2    is a perspective view of a tibial cutting guide assembly of the orthopaedic joint replacement system; 
         FIG.  3    is a cross-sectional side elevation view of a portion of the cutting guide assembly of  FIG.  2    taken along line  3 - 3  in  FIG.  2   ; 
         FIG.  4    is a side elevation view of a surgical reamer of the orthopaedic joint replacement system; 
         FIG.  5    is an exploded perspective view of a number of surgical instruments of the orthopaedic joint replacement system for use in determining an amount of tibial offset; 
         FIG.  5 A  is a cross-sectional elevation view of an offset guide of the surgical instruments of  FIG.  5   ; 
         FIG.  6    is a perspective view of an impaction handle of the orthopaedic joint replacement system; 
         FIG.  6 A  is a bottom perspective view of the impaction handle of  FIG.  6   ; 
         FIGS.  7 - 21    illustrate a number of steps of a surgical procedure utilizing the orthopaedic joint replacement system; 
         FIG.  22    is a perspective view of another surgical reamer; and 
         FIGS.  22 A- 24    illustrate a number of steps of a surgical procedure utilizing the orthopaedic joint replacement system. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     Terms representing anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, etcetera, may be used throughout the specification in reference to the orthopaedic implants and orthopaedic surgical instruments described herein as well as in reference to the patient&#39;s natural anatomy. Such terms have well-understood meanings in both the study of anatomy and the field of orthopaedics. Use of such anatomical reference terms in the written description and claims is intended to be consistent with their well-understood meanings unless noted otherwise. 
     The exemplary embodiments of the present disclosure are described and illustrated below to encompass prosthetic knee joints and knee joint components, as well as methods of implanting and reconstructing knee joints. It will also be apparent to those of ordinary skill in the art that the preferred embodiments discussed below are exemplary in nature and may be reconfigured without departing from the scope and spirit of the present invention. However, for clarity and precision, the exemplary embodiments as discussed below may include optional steps, methods, and features that one of ordinary skill should recognize as not being a requisite to fall within the scope of the present invention. 
     Referring now to  FIG.  1   , the orthopaedic joint replacement system  10  includes a number of orthopaedic prosthetic components  12  and a number of orthopaedic surgical instruments  14  (see, for example,  FIG.  2   ) for use in preparing the bone to receive one or more of the prosthetic components  12 . What is meant herein by the term “orthopaedic surgical instrument” or “orthopaedic surgical instrument system” is a surgical tool for use by a surgeon in performing an orthopaedic surgical procedure. As such, it should be appreciated that, as used herein, the terms “orthopaedic surgical instrument” and “orthopaedic surgical instruments” are distinct from orthopaedic prosthetic components or implants, such as those shown in  FIG.  1   . 
     The prosthetic components  12  of the system  10  include a prosthetic femoral component  20  configured to be secured to a surgically-prepared distal end of a patient&#39;s femur and a prosthetic tibial component  22  configured to be secured to a surgically-prepared proximal end of the patient&#39;s tibia. In the illustrative embodiment, the tibial component  22  includes a tibial tray  24  and a prosthetic insert  26  configured to engage the femoral component  20  after implantation into a patient&#39;s knee. It should be appreciated that the system  10  may include a number of components  12  corresponding to patients having bones of varying sizes. In that way, a surgeon will be able to select the components and other instruments that most-closely match the patient&#39;s bony anatomy. 
     As shown in  FIG.  1   , the femoral component  20  includes an anterior flange  30  and a pair of condyles  32  extending away from the flange  30 . A notch  34 , commonly called an intra-condylar notch, is defined between the condyles  32 . The condyles  32  define articulation surfaces  36  configured to engage corresponding articulation surfaces  70  of the insert  26 . The femoral component  20  also includes an elongated stem post  40 , which extends superiorly away from its backside surface  42 . As described in greater detail below, the femoral stem post  40  is configured to receive one of a number of different stem components  44 . In the illustrative embodiment, a threaded bore  48 , which is sized to receive a corresponding threaded shaft  50  of a stem component  44 , is defined in the stem post  40 . 
     The tibial tray  24  is configured to be implanted into a surgically-prepared end of a patient&#39;s proximal tibia (not shown). The tibial tray  24  includes a platform  58  having an elongated stem post  60  extending inferiorly away from its inferior surface  62 . The elongated tibial stem post  60  is configured to receive one of a number of different stem components  44 . Specifically, as can be seen in  FIG.  1   , a threaded bore  48 , which is sized to receive a corresponding threaded shaft  50  of a stem component  44 , is defined in the stem post  60 . 
     The insert  26  is securable to the tibial tray  24 . In particular, the insert  26  may be snap-fit to the tibial tray  24 . In such a way, the insert  26  is fixed relative to the tibial tray  24  (i.e., it is not rotatable or moveable in the anterior/posterior or medial/lateral directions). Although, in other embodiments, the tibial tray may be secured in a manner that allows it to rotate relative to the tibial tray  24 . 
     The insert  26  includes lateral and medial articulation surfaces  70 . The surfaces  70  are configured to articulate with the corresponding articulation surfaces  36  of the femoral component  20 . Specifically, the femoral component  20  is configured to be implanted into a surgically-prepared distal end of the patient&#39;s femur (not shown), and is configured to emulate the configuration of the patient&#39;s natural femoral condyles. As such, the articulation surfaces  36  of the femoral component  20  are configured (e.g., curved) in a manner which mimics the condyles of the natural femur. 
     As shown in  FIG.  1   , the stem components  44  of the system  10  include elongated stems  80 , which are configured to be attached to either of the components  20 ,  22 . Each elongated stem  80  extends from the threaded shaft  50  at one end to a pointed tip  82  at the opposite end. Each stem also includes a ribbed outer surface  84  extending from the pointed tip  82  toward the threaded shaft  50 . A plurality of substantially planar surfaces  86  are positioned around the outer circumference of the stem  80  adjacent to the shaft  50 . The surfaces  86  are sized and positioned to receive the end of a wrench or other installation tool so that the stem  80  may be rotated into tight engagement with one of the threaded bores  48 . 
     In the illustrative embodiment, the prosthetic components  12  also include a plurality of offset adapters  90 ,  92  configured to be attached to the components  20 ,  22 . As shown in  FIG.  1   , the adapter  90  is configured to offset the longitudinal axis of the elongated stem  80  from the longitudinal axis of the stem post  60  of the tibial tray  24  by a predetermined amount. Similarly, the adapter  92  is configured offset the longitudinal axis of the elongated stem  80  from the longitudinal axis of the stem post  40  of the femoral component  20 . Each of the adapters  90 ,  92  includes a threaded shaft  50  configured to be received in the threaded bore  48  of either of the components  20 ,  22 . Each of the adapters  90 ,  92  also includes a threaded bore  48  at its opposite end, which is sized to receive a threaded shaft  50  of one of the elongated stems  80 . In the illustrative embodiment, a locking nut  100  is positioned on the threaded shaft  50  of each of the adapters  90 ,  92 . The locking nut  100  may be typed against the surface of the stem post of each component to secure the adapter thereto. 
     The components of the knee prosthesis  10  that engage the natural bone, such as the femoral component  20 , the tibial tray  24 , and the stem components  44 , may be constructed with an implant-grade biocompatible metal, although other materials may also be used. Examples of such metals include cobalt, including cobalt alloys such as a cobalt chrome alloy, titanium, including titanium alloys such as a Ti6Al4V alloy, and stainless steel. Such a metallic components may also be coated with a surface treatment, such as hydroxyapatite, to enhance biocompatibility. Moreover, the surfaces of the metallic components that engage the natural bone may be textured to facilitate securing the components to the bone. Such surfaces may also be porous coated to promote bone ingrowth for permanent fixation. 
     The insert  26  may be constructed with a material that allows for smooth articulation between the insert  26  and the femoral component  20 , such as a polymeric material. One such polymeric material is polyethylene such as ultrahigh molecular weight polyethylene (UHMWPE). 
     Referring now to  FIG.  2   , the system  10  includes an attachment device  212  and a cutting block  214  configured to be secured to the attachment device  212 . In the illustrative embodiment, the attachment device  212  is configured to be selectively attached to a surgical reamer  216  (see  FIG.  4   ). As described in greater detail below, the surgeon may use the attachment device  212  and the reamer  216  to position the cutting block  214  for use during the resection of the proximal end of a patient&#39;s tibia. 
     The attachment device  212  of the system  10  includes an attachment base  230  configured to be secured to the surgical reamer  216  and a mounting frame  232  configured to be moveably coupled to the base  230 . The mounting frame  232  is also configured to be secured to the cutting block  214 , as described in greater detail below. In the illustrative embodiment, the attachment base  230  and the mounting frame  232  are formed from a metallic material, such as, for example, stainless steel or cobalt chromium. It should be appreciated that in other embodiments the attachment base  230  or the mounting frame  232  may be formed from a polymeric material. 
     The attachment base  230  includes a housing  234 , a rail  236  that extends outwardly from the housing  234 , and a locking knob  238  that is attached to the upper end  242  of the housing  234 . The attachment base  230  has a longitudinal axis  240  extending through a lower end  244  and the upper end  242 . The rail  236  has an end  246  secured to the housing  234  and extends to a cantilevered tip (see  FIG.  3   ). In the illustrative embodiment, the rail  236  extends orthogonal to the longitudinal axis  240  of the housing  234 . As shown in  FIG.  2   , the rail  236  has an oblong cross-section with a substantially planar top and bottom surfaces  250 ,  252 , respectively, to permit relative rotation between the attachment base  230  and the mounting frame  232 . 
     Referring now to  FIG.  3   , the attachment base  230  has a passageway  254  that extends along the axis  240  from the lower end  244  of the housing  234  through the locking knob  238 . The passageway  254  is sized to receive the surgical reamer  216  and permit the base  230  to be moved along the shaft of the reamer  216  to a desired location. The housing  234  includes a main body  256  that extends from the lower end  244  to a shoulder surface  258  positioned below the knob  238 . An upper shaft  260  extends outwardly from the shoulder surface  258  to the upper end  242  of the housing  234 , as shown in  FIG.  3   . 
     In the illustrative embodiment, the upper shaft  260  includes a plurality of longitudinal slots  262  that divide the shaft  260  into a number of beams  264 . Each beam  264  includes an outer plate  266  positioned on its outer surface. As shown in  FIG.  3   , each plate  266  includes an upper surface  268  that is connected to a lower surface  270  that is externally-threaded. When viewed in cross-section, the upper surface  268  is angled or ramped relative to the lower surface  270  so that the plate  266  has an outer diameter at its lower end greater than at its upper end. At the upper end  242 , a retaining flange  274  extends outwardly from each of the beams  264 . 
     As shown in  FIG.  3   , the locking knob  238  includes an upper surface  276  configured to be gripped by a user and a substantially planar bottom surface  278  configured to engage the shoulder surface  258  of the housing  234 . A bore  280  extends through the locking knob  238  along the longitudinal axis  240  and defines a section of the passageway  254 . In the illustrative embodiment, the locking knob  238  includes an annular rib  282  that extends into the bore  280  near the lower end thereof. The locking knob  238  includes another annular rib  284  that is spaced from and positioned above the rib  282 . The annular rib  282  is internally-threaded and may be threaded onto the lower surfaces  270  of the beams  264  of the base  230 . As shown in  FIG.  3   , the annular rib  284  has a conical lower surface  286  such that its inner diameter is greater at its upper end than at its lower end. The rib  284  has an upper surface  288  positioned opposite the lower surface  286 . In the illustrative embodiment, the retaining flanges  274  of the beams  264  are configured to engage the upper surface  288  to prevent the disassembly of the knob  238  from the housing  234 . 
     In use, a surgeon may position a reamer  216  in the passageway  254  of the attachment base  230 . To lock the base  230  in position relative to the reamer  216 , the surgeon may rotate the knob  238  clockwise about the axis  240  to slide the ribs  282 ,  284  downward along the plates  266  of the beams  264 . The engagement between the conical lower surface  286  of the rib  284  and the ramped upper surfaces  268  of the beams  264  causes the beams  264  to bend radially inward toward the axis  240 , thereby contracting the diameter of the passageway  254 . In the illustrative embodiment, when the bottom surface  278  of knob  238  is engaged with the shoulder surface  258  of the housing  234 , the beams  264  are compressed against the reamer  216 , thereby securing the attachment base  230  to the reamer  216  at a desired position. To release the attachment base  230 , the surgeon may rotate the knob  238  counterclockwise and advance the knob  238  upward, thereby moving the rib  284  out of contact with the plates  266  and permitting the beams  264  bend radially outward. 
     Returning to  FIG.  2   , the system  10  also includes a mounting frame  232  configured to be moveably coupled to the base  230 . In the illustrative embodiment, the mounting frame  232  includes an upper bracket  300 , a lower bracket  302 , and a base plate  304  connecting the brackets  300 ,  302 . The upper bracket  300  includes an opening  306  sized to receive the rail  236  of the attachment base  230 . In the illustrative embodiment, the opening  306  is defined by a pair of substantially planar surfaces that match the configuration of the surfaces  250 ,  252  of the rail  236 . A knurled surface  308  is positioned on each side of the bracket  300  to permit a surgeon to grip the bracket  300  to advance it along the rail  236 . 
     The upper bracket  300  also includes a locking mechanism  310 , which may be operated to secure the upper bracket (and hence the mounting frame  232 ) to the rail  236 . In the illustrative embodiment, the locking mechanism  310  includes a user-operated handle  312  and a shaft (not shown) that extends through a bore into the opening  306 . When the handle  312  is rotated clockwise, the shaft  314  is advanced into engagement with the upper surface  250  of the rail  236 . It should be appreciated that in other embodiments other mechanical locking devices may be used to secure the mounting frame  232  in position relative to the rail  236 . 
     As described above, the mounting frame  232  also includes a lower bracket  302 . The lower bracket  302  includes a pair of grooves  320  sized to receive a corresponding pair of tabs  322  of the cutting block  214 . In that way, the grooves  320  provide a mounting point for the cutting block  214 . Similar to the upper bracket  300 , the lower bracket  302  includes a locking mechanism  324 , which may be operated to secure the cutting block  214  to the lower bracket  302 . In the illustrative embodiment, the locking mechanism  324  includes a user-operated handle  326  that is positioned in a gap  328  defined between the brackets  300 ,  302 . The handle  326  is attached to a shaft (not shown). When the handle  326  is rotated clockwise, the shaft may be advanced into engagement with the cutting block  214 , thereby securing the block  214  to the mounting frame  232 . It should be appreciated that in other embodiments other mechanical locking devices may be used to secure the mounting frame  232  to the cutting block  214 . 
     As shown in  FIG.  2    the cutting block  214  includes a posterior side wall  340  that is configured to confront the anterior side of the patient&#39;s tibia, as described in greater detail below. The cutting block  214  also includes an anterior side wall  342  that is positioned opposite the posterior side wall  340 . An upper surface  344  connects the side walls  340 ,  342 . The upper surface  344  has a groove  346  defined between the tabs  322  described above. In the illustrative embodiment, the cutting block  114  is formed from a metallic material, such as, for example, stainless steel or cobalt chromium. 
     The cutting block  214  includes a number of cutting guides  350  that may be used during an orthopaedic surgical procedure to resect a portion of the patient&#39;s bone. Each cutting guide  350  includes an elongated slot sized to receive a cutting saw blade of a surgical saw or other surgical device. In the illustrative embodiment, the cutting block  214  has four cutting guides  350  extending through the side walls  340 ,  342 . Each cutting guide  350  is spaced apart from the other cutting guides  350  by about  5  millimeters and includes a planar surface  352  that defines a resection plane. 
     As described above, the system  10  includes a number of surgical reamers to define a passageway in the patient&#39;s tibia during the surgical procedure. Referring now to  FIG.  4   , one of the surgical reamers  216  is shown. The reamer  216  includes an elongated shaft  360  having a plurality of cutting flutes  362  formed at a distal end  364 . A tool shank  366  is formed at the opposite end and is sized to be secured to a surgical drill or other rotary surgical instrument. The elongated shaft  360  includes a cylindrical outer surface  370  that extends from the cutting flutes  362  to the tool shank  366 . A plurality of spaced-apart annular slots  368  are defined in the outer surface  370 . In the illustrative embodiment, the position of each annular slot  368  along the outer surface  370  corresponds to a desired reaming depth of the reamer  216 . In the illustrative embodiment, the heights of the slots  368  vary in order to provide the surgeon with a visual indication of the different depths. 
     Referring now to  FIG.  5   , the system  10  also includes a tibial base plate  400  configured to be positioned on a proximal end of a patient&#39;s tibia. It should be appreciated that the system  10  may include multiple tibial plates of different sizes generally corresponding to the various potential sizes of a patient&#39;s bony anatomy. The system  10  also includes a plurality of offset guides  402  configured for use with the tibial base plate  400  and a reaming guide tower or body  404  that is also configured for use with the tibial plate  400 . The tibial base plate  400  includes a number of fixation pin guide holes  406 , which permit the passage of fixation pins  408  (see  FIG.  21   ) to secure the tibial plate  400  to the proximal end of the patient&#39;s tibia. 
     The tibial base plate  400  includes a substantially planar bottom surface  410  and a substantially planar top surface  412  that is positioned opposite the bottom surface  410 . A curved outer side wall  414  extends between the surfaces  410 ,  412 . The tibial plate  400  also includes a central opening  416  that extends through the surfaces  410 ,  412 . A pair of guide bores  418  are positioned adjacent to the anterior side of the tibial plate  400 . As described in greater detail below, each guide bore  418  is sized to receive one of the fixation pins  420  of the reaming guide tower  404 . 
     As shown in  FIG.  5   , each offset guide  402  includes an upper drum  430  connected to a lower cylindrical plate  432 . The cylindrical plate  432  is sized to be received in the central opening  416  of the tibial plate  400 . Each offset guide  402  also includes a passageway  434  that extends through the drum  430  and plate  432 . The amount of offset is different for each offset guide  402 . In the illustrative embodiment, the drum  430  includes a plurality of indicia  440  that cooperate with a marking  442  on the tibial base plate  400  to provide a surgeon with an indication of the angular position of the longitudinal axis  436 . When the marking  442  is aligned with one of the indicia  440 , a numerical indicator corresponding to that indicia  440  may be read to determine the offset orientation. 
     As shown in  FIG.  5 A , each passageway  434  extends along a longitudinal axis  436  that is offset from the longitudinal axis  438  of the cylindrical plate  432 . In the illustrative embodiment, the elongated shaft  360  of the reamer extends longitudinal axis  438  when the tibial base plate  400  is positioned over the reamer. The passageway  434  is illustratively defined by a tapered inner wall  444  that extends from an upper or proximal opening  446  that is larger than the lower or distal opening  448 . In other embodiments, the passageway may be cylindrical. 
     As described above, the system  10  also includes a reaming guide tower  404 . The tower  404  includes a main body  450  that extends from a substantially planar bottom surface  452  to an upper surface  454 . A guide passageway  456  extends through the surfaces  452 ,  454 . When the tower  404  is attached to the tibial plate  400 , the passageway  456  is aligned with the central opening  416 . As described above, the tower  404  includes a pair of anterior fixation pins  420 , which are received in the anterior bores  418  of the tibial plate  400  when the tower is attached thereto. 
     Referring now to  FIG.  6   , an impaction handle  470  of the system  10  is shown. In the illustrative embodiment, the impaction handle is formed as an assembly from separate components made from metallic materials such as, for example stainless steel. The impaction handle  470  includes a strike plate  472  attached to the distal end of an elongated body  474 . The elongated body  474  is sized and shaped to be gripped by a surgeon during use. The body  474  extends from the strike plate  472  to an end  476 . The impaction handle  470  also includes a proximal post  478  that extends from the end  476  of the elongated body  474 . The proximal post  478  includes a cylindrical body section  480  that is connected to the end  476 , an intermediate cylindrical body section  482  extending from the body section  480 , and a proximal tip  484  extending from the section  482 . The proximal tip  484  includes a substantially planar anterior surface  486  that is connected to a curved posterior surface  488 . 
     The impaction handle  470  includes an attachment mechanism  500  configured to selectively secure other surgical instruments to the impaction handle  470  during the surgical procedure. In the illustrative embodiment the attachment mechanism  500  includes a lever arm  502 , which is coupled to the post  478  and is configured to pivot relative to the proximal post  478 . The lever arm  502  includes a locking flange  504  that extends toward the planar anterior surface  486  of the proximal tip  484 . When the lever arm  502  is pivoted in the direction indicated by arrow  506 , the locking flange  504  is advanced away from the proximal tip  484 . The lever arm  502  also includes a tab  508  that extends in the direction opposite the locking flange  504 . 
     The attachment mechanism  500  includes a bracket  510  that is configured to slide relative to the post  478  and the elongated body  474 . The bracket  510  is illustratively L-shaped and includes a flange  512  that extends away from the proximal post  478 . The flange  512  is connected to a slide plate  514  that extends along the body section  480 . As shown in  FIG.  6   , the slide plate  514  has an oblong slot  516  defined therein, and the tab  508  is positioned in the slot  516 . 
     The bracket  510  includes a pair of tabs  522  that are received in a pair of longitudinal slots  524  defined in the cylindrical body section  480  of the post  478 . As shown in  FIG.  6 A , the bracket  510  also includes a plate  526  that is received in a channel  528  extending through the post  478 . A biasing element such as, for example, a spring  530  is positioned between the plate  526  and the post  478  to bias the bracket  510  (and hence the lever arm  502 ) in the position shown in  FIG.  6   . 
     To advance the lever arm  502  in the direction indicated by arrow  506 , a user may press on the flange  512  to overcome the bias exerted by the spring  530  and cause the bracket  510  to advance distally toward the strike plate  472 . As the bracket  510  advances distally, the flange  512  is advanced into a channel  520  defined in the end  476  of the elongated body  474 . Additionally, the proximal edge  522  of the slide plate  514  is advanced into engagement with the tab  508 , thereby causing the lever arm  502  to pivot about its axis  532  (see  FIG.  6 A ) and moving the locking flange  504  away from the proximal tip  484 . When the user releases the flange  512 , the spring  530  urges the slide plate  514  toward the proximal end, thereby releasing the lever arm  502  to pivot toward the locking flange  504 . 
     The instruments  14  described may be used to surgically prepare a patient&#39;s femur to receive a prosthetic tibial component  22 , one of the stem components  44 , and an offset adaptor  90 . In the illustrative embodiment, the instruments  14  may be used in a revision procedure in which a primary implant has been removed from a proximal end of the patient&#39;s tibia. As shown in  FIG.  7   , the proximal end  600  of a patient&#39;s tibia  602  in a revision procedure includes a proximal surface  604  that has been previously-shaped to receive the primary implant. During a revision procedure, the surface  604  is resected to prepare the proximal end  600  to receive the prosthetic tibial component  22 .  FIGS.  7 - 23    illustrate a number of exemplary steps of a procedure for surgically-preparing the proximal end  600  during a revision procedure. It should be appreciated that any surgical procedure may include additional or fewer steps depending on the state of the patient&#39;s bony anatomy and the preferences of the surgeon. 
     Referring now to  FIG.  7   , the surgeon may select one of the reamers  216  for insertion into the intramedullary canal  608  of the patient&#39;s tibia  602 . The choice of reamer may depend on the size and shape of the patient&#39;s tibia  602 . As shown in  FIG.  7   , the surgeon may advance the selected reamer  216  into the canal  608  to straight ream the canal to a predetermined depth corresponding to one of the annular slots  368 . 
     The surgeon may leave the reamer  216  in place at the predetermined depth while assembling the attachment device  212 . As described above, the surgeon may attach the cutting block  214  to the mounting frame  232  and securing the instruments together by operating the handle  326 . The surgeon may slide the mounting frame  232  along the rail  236  of the attachment base  230  and lock the frame  232  in position relative to the base  230  by operating the other handle  312 . As shown in  FIG.  8   , the surgeon may place the assembled attachment device  212  on the elongated shaft  360  of the reamer  216 . To do so, the surgeon may align the passageway  254  of the attachment device  212  with the shank  366  of the reamer  216  and then advance the attachment device  212  over the shank  366  and down the elongated shaft  360  toward the tibia  602 . 
     As shown in  FIGS.  9 - 10   , a surgeon may utilize a number of different gauges  620 ,  622  to determine where to place the cutting block  214  relative to the bone  602 . Each of the gauges  620 ,  622  has a probe tip  624  configured to engage the proximal surface  604  when the cutting block  214  is properly positioned relative to the tibia  602 . In the illustrative embodiment, each gauge is selectively attached to the cutting block  214  via a mounting flange  626  sized to be positioned in the cutting guides  350  of the block  214 . The gauge  622  is also adjustable such that the probe tip  624  may be set at different heights relative to its mounting flange  626  (and hence the cutting block  214 ). The surgeon may slide the attachment device  212  and cutting block  214  along the reamer  216  in the directions indicated by arrows  630  in  FIGS.  9 - 10    until the cutting block  214  is properly positioned to guide the resection of the proximal surface  604 . 
     The surgeon may then lock the attachment device  212  at the desired position by operating the control knob  238 . When the knob  238  is rotated clockwise, the ribs  282 ,  284  of the knob  238  cause the diameter of the passageway  254  to contract, as described above. In the illustrative embodiment, when the bottom surface  278  of knob  238  is engaged with the shoulder surface  258  of the housing  234 , the attachment base  230  engages the reamer  216 , thereby locking the cutting block  214  in position relative to the bone. The surgeon may also selectively operate the handle  312  to free the mounting frame  232  (and hence the cutting block  214 ) for movement along the rail  236 . In that way, the surgeon may also adjust the position of the cutting block  214  relative to the anterior face of the tibia  602 . 
     As shown in  FIG.  11   , the surgeon may utilize a number of fixation pins  420  to secure the cutting block  214  to the tibia  602 . The surgeon may then detach the cutting block  214  from the attachment device  212  by operating both handles  312 ,  326  to release the mounting frame  232  from the cutting block  214  and the attachment base  230 . After sliding the mounting frame  232  off the rail  236 , the surgeon may release the attachment base  230  from the reamer  216  by operating the control knob  238 . 
     Referring now to  FIG.  12   , the surgeon may also remove the reamer  216  from the canal  608  before resecting the tibia  602 . To perform the resection, the surgeon may advance a surgical saw  640  through one of the cutting guide slots  350  into contact with the patient&#39;s bone. The surgeon may then use the saw  640  to remove material from the end  600  of the patient&#39;s tibia  602  and create a new surgically-prepared proximal surface shaped to receive a prosthetic tibial component  22 . 
     Referring now to  FIGS.  13 - 14   , surgeon may utilize the reamer  216  and the tibial plate  400  to determine whether an offset adaptor  90  should be included in the tibial prosthetic assembly. To do so, surgeon may insert the reamer  216  into the intramedullary canal  608 , as shown in  FIG.  13   . The surgeon may position the tibial plate  400  on the proximal end  600  of the patient&#39;s tibia  602 . As shown in  FIG.  14   , the center of the opening  416  of the tibial plate  400  is offset from the longitudinal axis of the reamer  216 , indicating the need to use an offset adapter  90  in the tibial prosthetic assembly. 
     As shown in  FIG.  15   , the surgeon may select an offset guide  402  and advance along the reamer  216  into contact with the tibial plate  400  positioned on the patient&#39;s tibia  602 . With the offset guide  402  seated on the tibial plate  400 , the surgeon may grip the contoured outer surface of the guide  402  to turn the guide  402  about the reamer  216  as indicated in  FIG.  15    by arrows  650 . As the guide  402  is turned, the tibial plate  400  is rotated about the proximal surface  604  of the patient&#39;s tibia  602 . That movement changes the offset orientation of the guide  402  and tibial plate  400  relative to the reamer  216 . The surgeon may continue to turn the guide  402  until the tibial plate  400  is placed in a location on the patient&#39;s tibia  602  that offers maximum coverage of the surgically-prepared proximal surface  604 . When the base plate  400  is in the desired location on the patient&#39;s tibia  602 , the surgeon identifies the indicia  440  that is aligned with the mark  442  and reads the numerical indicator associated with the indicia  440  to identify the selected offset orientation, as shown in  FIG.  16   . It should be appreciated that the surgeon may repeat this process with other offset guides  402  having different amounts of offset until the tibial plate  400  is placed in a location on the patient&#39;s tibia  602  that offers maximum coverage of the proximal surface  604 . When the tibial plate  400  is positioned at a desired location on the patient&#39;s tibia  602 , the surgeon may utilize one or more fixation pins  408  to secure the tibial plate  400  and the position, as shown in  FIG.  16   . The surgeon may then remove the offset guide  402  from the tibial plate  400  and the reamer  216 , as shown in  FIG.  17   . 
     Referring now to  FIG.  18   , the surgeon may perform another reaming operation utilizing a larger diameter reamer  702  continue reshaping the canal  608 . As shown in  FIG.  19   , the surgeon may also utilize the reaming guide tower  404  with the tibial plate  400 . To do so, the surgeon may align the fixation pins  420  of the tower  404  with the guide holes  418  of the tibial plate  400 . The surgeon may then advance the fixation pins  420  through the guide holes  418  and into the proximal end  600  of the patient&#39;s tibia  602 . 
     Referring now to  FIGS.  20 - 22   , the surgeon may utilize another reamer  704  with the tower  404 . The system  10  also includes a moveable depth stop  710 , which be attached to any of the reamers at an annular slot  642  corresponding to a desired depth. In the illustrative embodiment, the depth stop  710  has a central opening  712  and a plurality of alignment tabs  714  extending inwardly into the opening  712 . The central opening  712  has a diameter corresponding to the largest diameter reamer in the system  10 . Each reamer, including the reamer  704 , includes a plurality of longitudinal slots  716  corresponding in number to the number of alignment tabs  714  of the depth stop  710 . As shown in  FIG.  20   , the bottom surfaces of the slots  716  of each reamer are positioned and sized to be received in an alignment opening  720  defined by the tips of the tabs  714  so that a single depth stop  710  may be used with any size reamer. 
     In the illustrative embodiment, the depth stop  710  includes a movable plate  722  having a pin that may be advanced into and out of engagement with the annular slot  642  or other aperture to secure the depth stop at a desired position. 
     As shown in  FIG.  21   , when the depth stop  710  is properly positioned at the desired annular slot  642  of the reamer  704 , the reamer  704  may be advanced into the central cylindrical passageway of a reaming guide adaptor  724  positioned in the guide tower  404 . The reamer  704  may then be advanced along the guide adaptor  724  and into contact with the proximal end  600  of the patient&#39;s tibia  602 . The surgeon may continue to advance the reamer  704  deeper into the patient&#39;s tibia until the depth stop  710  contacts the guide adapter  724 , thereby reshaping the canal  608  as desired. It should also be appreciated that in some embodiments the reamer and the depth stop  710  may be used with the guide tower alone. 
     Returning to  FIGS.  22 - 22 A , the reamer  704  is shown with the guide tower  404 . Similar to the reamer  216 , the reamer  704  includes an elongated shaft  730  having a plurality of cutting flutes  732  formed at a distal end  734 . A tool shank  736  is formed at the opposite end and is sized to be secured to a surgical drill or other rotary surgical instrument. The elongated shaft  730  includes an outer surface  740  that extends from the cutting flutes  732  to the tool shank  736 , and the plurality of longitudinal slots  716  are defined in the outer surface  740 . 
     As shown in  FIG.  22   , the plurality of cutting flutes  732  include a frustoconical distal section  750  that extends from the distal end  734 . The distal section  750  is connected at an edge  752  to a cylindrical middle section  754  of the cutting flutes  732  (i.e., the edges of cutting flutes  732  define a cylindrical shape). The middle section  754  has a diameter  756 . The middle section  754  is connected to a proximal section  758  via a tapered section  760 . In the illustrative embodiment, the proximal section  758  has a diameter  762  that is greater than the diameter  756  of the middle section  754 . The combination of the cylindrical middle section  754 , tapered section  760 , and proximal section  758  of the cutting flutes  732  cooperate to define an opening a patient&#39;s tibia shaped to match the offset adaptor  90  of the prosthetic tibial component  22 , as indicated in broken line in  FIG.  22 A . 
     Referring now to  FIG.  23   , the surgeon may select a keel punch  660  to resize the canal  608  to receive a portion of the elongated stem post  60  of the tibial tray  24 . The keel punch  660  includes a pair of arms  662  extending outwardly from a central body  664 . Each of the arms  662  includes a number of downwardly-extending cutting teeth  668  the patient&#39;s bone to create a passageway for the elongated stem post  60 . The central body  664  includes an undercut  670  sized to receive the flange  504  of the lever arm  502  of the impaction handle  470 . The central body  664  also includes an engagement plate  672  positioned above the undercut  670 , which is configured to engage the locking flange  504 , as shown in  FIG.  23   . 
     To secure the keel punch  660  the impaction handle  470 , a user may press on the flange  512  to cause the bracket  510  of the handle  470  to advance distally toward the strike plate  472 . As the bracket  510  advances distally, the flange  512  is advanced into a channel  520  defined in the end  476  of the elongated body  474 . Additionally, the proximal edge  522  of the slide plate  514  is advanced into engagement with the tab  508 , thereby causing the lever arm  502  to pivot about its axis and moving the locking flange  504  away from the proximal tip  484 . The keel punch  660  may then be advanced over the proximal tip  484  and into contact with the cylindrical body section  482 , as shown in  FIG.  23   . The user may then release the flange  512  and a biasing element  530  of the handle  470  urges the bracket  510  proximally, thereby moving the locking flange  504  toward the proximal tip  484  and into engagement with the engagement plate  672  to secure the keel punch  660  to the handle  470 . 
     As shown in  FIG.  24   , the surgeon may remove the tibial plate  400  from the proximal end  600  of the patient&#39;s tibia  602  and replace it with another tibial plate  690  including openings  692  sized to receive the arms  662  of the keel punch  660 . The surgeon may then advance the impaction handle  470  and keel punch  660  toward the tibial plate  690 , as indicated by arrow  694 . As the keel punch  660  passes through the tibial plate  690 , the cutting teeth  668  engage the patient&#39;s bone and reshape the canal to receive the elongated post  60  of the tibial prosthetic component  22 . 
     While the foregoing exemplary embodiments have been described to have a separable tibial tray and a tibial tray insert, it is to be understood that the tibial tray may include condyle receiver bearing surfaces that obviate the need for a separate tibial tray insert. 
     Following from the above description and invention summaries, it should be apparent to those of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, the invention contained herein is not limited to this precise embodiment and that changes may be made to such embodiments without departing from the scope of the invention as defined by the claims. Additionally, it is to be understood that the invention is defined by the claims and it is not intended that any limitations or elements describing the exemplary embodiments set forth herein are to be incorporated into the interpretation of any claim element unless such limitation or element is explicitly stated. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of any claims, since the invention is defined by the claims and since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.