Patent Publication Number: US-2011054626-A1

Title: Stem extension and adaptor for use with a knee orthopaedic implant

Description:
This application is a continuation of U.S. patent application Ser. No. 11/862,310, filed on Sep. 27, 2007, which is incorporated in its entirety herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to orthopaedic implant devices and more particularly to stem extensions for use with orthopaedic implant devices for knees. 
     BACKGROUND 
     Movement (e.g., flexion and extension) of the natural human knee involves movements of the femur and the tibia. Specifically, during flexion and extension, the distal end of the femur and the proximal end of the tibia articulate relative to one another through a series of complex movements. Damage (e.g., trauma) or disease can deteriorate the bones, articular cartilage, and/or ligaments of the knee, which can ultimately affect the ability of the natural knee to function in such a manner. As a result, orthopaedic implant devices have been developed to replace the natural knees of patients. 
     The longevity of an orthopaedic implant is dependent on a number of factors. One such factor is the proper matching of the implant with the patient&#39;s anatomy. Due to the large variation in human anatomy, the surgeon may use orthopaedic implants of various sizes and configurations to ensure proper matching of the implant with the anatomy of the patient. 
     SUMMARY 
     According to one aspect, an orthopaedic implant may include a knee prosthetic component configured to be coupled to a surgically prepared surface of a bone of a patient and an adaptor that connects the knee prosthetic component with a stem extension. The adaptor may include a first mounting end that is coupled with the knee prosthetic component and a second mounting end that is coupled with the stem extension. The first mounting end may define a first axis and the second mounting end may define a second axis. The second axis may be offset from and parallel to the first axis when viewed in a first anatomical plane. Additionally, the first axis and the second axis may define an angle therebetween greater than zero degrees when viewed in a second anatomical plane substantially orthogonal to the first anatomical plane. In some embodiments, the second mounting end may comprise an aperture that receives a tapered end of the stem extension. Additionally, in some embodiments, the second mounting end may be movable relative to the first mounting end. 
     In some embodiments, the knee prosthetic component may be embodied as a tibial tray. The tibial tray may include a platform and a stem extending downwardly from a bottom surface of the platform. The stem may have an aperture defined at the distal end. The first mounting end of the adaptor may be tapered such that the aperture of the stem may receive the first mounting end of the adaptor. The first anatomical plane may be the medial/lateral plane, and the second anatomical plane may be the anterior/posterior plane. For example, the second axis of the second mounting end of the adaptor may be offset from and parallel to the first axis of the first mounting end of the adaptor when viewed in the medial/lateral plane. Additionally, the first axis of the first mounting end of the adaptor and the second axis of the second mounting end of the adaptor may define an angle therebetween greater than zero degrees when viewed in the anterior/posterior plane. 
     In other embodiments, the knee prosthetic component may be embodied as femoral component. The femoral component may include a pair of condyles and a platform defined between the condyles. The platform may include an aperture defined in an upper surface. The first mounting end of the adaptor may be tapered such that the aperture of the platform may receive the first mounting end of the adaptor. The first anatomical plane may be the anterior/posterior plane, and the second anatomical plane may be the medial/lateral plane. For example, the second axis of the second mounting end of the adaptor may be offset from and parallel to the first axis of the first mounting end of the adaptor when viewed in the anterior/posterior plane. Additionally, the first axis of the first mounting end of the adaptor and the second axis of the second mounting end of the adaptor may define an angle therebetween greater than zero degrees when viewed in the medial/lateral plane. 
     In some embodiments, the adaptor may be formed from two pieces. The first piece may include the first mounting end and a first mounting surface. The second piece may include the second mounting end and a second mounting surface. In some embodiments, the second mounting surface may be movable relative to the first mounting surface to change the angle defined between the first axis and the second axis when viewed in the second anatomical plane. Additionally, in some embodiments, the first mounting surface may include a first number of teeth and the second mounting surface may include a second number of teeth. The second number of teeth may be interdigitated with the first number of teeth of the first mounting surface. 
     According to another aspect of the invention, an implantable orthopaedic device may include a stem extension. The stem extension may include a mounting end and an elongated shaft that extends from the mounting end. The mounting end may be configured to be coupled with a knee prosthetic component such as a tibial tray or a femoral component. The mounting end may define a first axis and the elongated shaft may define a second axis. In some embodiments, the second axis may be offset from and parallel to the first axis when viewed in a first anatomical plane. In some embodiments, the first anatomical plane may be the medial/lateral plane. In other embodiments, the first anatomical plane may be the anterior/posterior plane. For example, the second axis may be offset from and parallel to the first axis by a distance of about two millimeters to about eight millimeters when viewed in the medial/lateral plane in some embodiments. In other embodiments, the second axis may be offset from and parallel to the first axis when viewed in the anterior/posterior plane. 
     Additionally, the first axis and the second axis may define an angle therebetween greater than zero degrees when viewed in a second anatomical plane. In some embodiments, the angle defined between the first axis and the second axis may be greater than or equal to one degree when viewed in the second anatomical plane. In some embodiments, the second anatomical plane may be the anterior/posterior plane. In other embodiments, the second anatomical plane may be the medial/lateral plane. For example, the angle defined between the first axis and the second axis may be about one degree to about five degrees when viewed in the anterior/posterior plane. In other embodiments, the angle defined between the first axis and the second axis may be about one degree to about nine degrees when viewed in the medial/lateral plane. In some embodiments, the angle defined between the first axis and the second axis may also be adjustable when viewed in the second anatomical plane. For example, the elongated shaft may be movable relative to the mounting end to adjust the angle defined between the first axis and the second axis when viewed in the anterior/posterior plane. 
     According to still another aspect of the invention, an implantable orthopaedic device may include an adaptor. The adaptor may include a first mounting end configured to be coupled with a knee prosthetic component and a second mounting end configured to be coupled with a stem extension. The first mounting end may define a first axis, and the second mounting end may define a second axis. The second axis may be offset from and parallel to the first axis when viewed in a first plane. Additionally, the first axis and the second axis may define an angle therebetween greater than zero degrees when viewed in a second plane substantially orthogonal to the first plane. In one particular embodiment, the first plane may be embodied as the medial/lateral plane and the second plane may be embodied as the anterior/posterior plane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description particularly refers to the following figures, in which: 
         FIG. 1  is an exploded view of one embodiment of an orthopaedic implant for use with the tibia of a patient as viewed in the medial/lateral plane; 
         FIG. 2  is an exploded view of the orthopaedic implant of  FIG. 1  as viewed in the anterior/posterior plane; 
         FIG. 3  is a perspective view of the orthopaedic implant of  FIGS. 1 and 2 ; 
         FIG. 4  is an exploded view of another embodiment of an orthopaedic implant for use with the femur of a patient as viewed in the medial/lateral plane; 
         FIG. 5  is an exploded view of the orthopaedic implant of  FIG. 4  as viewed in the anterior/posterior plane; 
         FIG. 6  is a perspective view of the orthopaedic implant of  FIGS. 4 and 5 ; 
         FIG. 7  is a side elevation view of another embodiment of a stem extension of an orthopaedic implant as viewed in the medial/lateral plane; 
         FIG. 8  is a side elevation view of the stem extension of  FIG. 7  as viewed in the anterior/posterior plane; 
         FIG. 9  is a perspective view of another embodiment of the adaptor of the orthopaedic implant of  FIGS. 1-6 ; 
         FIG. 10  is an exploded perspective view of the adaptor of  FIG. 9 ; 
         FIG. 11  is a side elevation view of the adaptor of  FIGS. 9-10  as viewed in the anterior/posterior plane; 
         FIG. 12  is an exploded side elevation view of an embodiment of a multiple-piece stem extension as viewed in the medial/lateral plane; and 
         FIG. 13  is a side elevation view of the stem extension of  FIG. 12  as viewed in the anterior/posterior plane. 
     
    
    
     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. 
     Referring to  FIGS. 1-6 , an orthopaedic implant  10  includes a knee prosthetic component  12 , an adaptor  14 , and a stem extension  16 . The knee prosthetic component  12 , the adaptor  14 , and the stem extension  16  are configured to be coupled together as illustrated in  FIG. 3 . As described in more detail below, the adaptor  14  is configured to be coupled to both the knee prosthetic component  12  and the stem extension  16 . The knee prosthetic component  12 , the adaptor  14 , and the stem extension  16  are each illustratively formed from an implantable metallic material such as titanium or cobalt chromium but may be formed from other materials, such as a ceramic, a polymer, a bioengineered, or another like material, in other embodiments. 
     The knee prosthetic component  12  may be embodied as any type of knee prosthetic component configured to receive a stem extension. For example, as illustrated in  FIGS. 1-3 , the knee prosthetic component  12  may be embodied as a tibial tray  18 . The tibial tray includes a platform  20  and a stem  22 . The platform  20  includes an upper surface  24  and a lower surface  26 . The stem  22  extends downwardly from the lower surface  26 . The tibial tray  18  is configured to be coupled to a surgically prepared surface of the proximal end of a patient&#39;s tibia (not shown). When the tibial tray  18  is coupled to the patient&#39;s tibia, the stem  22  (as well as the adaptor  14  and stem extension  16 ) is embedded in the patient&#39;s tibia to thereby secure the tibial tray  18  to the patient&#39;s bone. 
     The tibial tray  18  is configured to be coupled with a tibial bearing (not shown) such as a polymer tibial bearing. As such, the upper surface  24  of the platform  20  may be configured to receive the tibial bearing. For example, the platform  20  may include any number of rails, tracks, openings, and/or the like configured to receive or otherwise be coupled with a portion of the tibial bearing. Additionally, the tibial tray  18  may be configured to be coupled to any type of tibial bearing, including, for example, a mobile tibial bearing and/or a fixed tibial bearing. 
     As discussed above, the adaptor  14  is configured to be coupled with the tibial tray  18  and the stem extension  16 . As such, the adaptor  14  includes a mounting end  28  configured to be coupled to the tibial tray  18 . The mounting end  28  may include any number of apertures, protrusions, grooves, and/or other structures necessary to facilitate the securing of adaptor  14  to the tibial tray  18 . For example, in the embodiment illustrated in  FIGS. 1-3 , the stem  22  of the tibial tray  18  includes an internal passage  30  and an aperture  32  defined at a distal end  34 . Accordingly, the mounting end  28  of the adaptor  14  is tapered and sized to be received in the aperture  32  of the stem  22 . In addition, the mounting end  28  includes a threaded aperture  36 . A bolt  38  is threaded into the threaded aperture  36  of the mounting end  28  via the internal passageway  30  of the stem  22  to secure the adaptor  14  to the tibial tray  18 . 
     In other embodiments, the mounting end  28  of the adaptor  14  may include other or additional structures to facilitate the coupling of the adaptor  14  to the tibial tray  18 . For example, in some embodiments, the mounting end  28  may include a threaded stud extending therefrom. In such embodiments, the distal end  34  of the stem  22  may include a corresponding threaded aperture configured to receive the threaded stud of the mounting end  28 . Alternatively, the distal end  34  of the stem  22  may be threaded and configured to be received in a threaded aperture defined in the mounting end  28  of the adaptor  14 . 
     The adaptor  14  also includes a mounting end  40  configured to be coupled with the stem extension  16 . Similar to the mounting end  28 , the mounting end  40  may include any number of apertures, protrusions, grooves, and/or other structures necessary to facilitate the securing of adaptor  14  to the stem extension  16 . For example, in the embodiments illustrated in  FIGS. 1-3 , the stem extension  16  includes a tapered end  43 . Accordingly, the mounting end  40  of the adaptor  14  includes an aperture  44  in which the tapered end  43  of the stem extension  16  is received. Again, in other embodiments, the mounting end  40  of the adaptor  14  may include other or additional structures to facilitate the coupling of the adaptor  14  to the stem extension  16 . For example, in some embodiments, the mounting end  40  of the adaptor  14  may include a threaded stud and the end  43  of the stem extension  16  may include a corresponding threaded aperture. In other embodiments, the end  43  of the stem extension  16  may include a threaded stud and the mounting end  40  of the adaptor  14  may include a corresponding threaded aperture. 
     The adaptor  14  is configured such that the position of the stem extension  16  relative to the tibial tray  18  is altered when the adaptor  14  is coupled therebetween. As illustrated in  FIGS. 1 and 2 , the mounting ends  28 ,  40  define an axis  46  and an axis  48 , respectively. The axis  48  defined by the mounting end  40  is offset from and parallel to the axis  46  defined by the mounting end  28  by a distance  50  when the axes  46 ,  48  are viewed in the medial/lateral plane (see  FIG. 1 ). Additionally, an angle  52  is defined between the axes  46 ,  48  when the axes  46 ,  48  are viewed in the anterior/posterior plane (see  FIG. 2 ). It should be appreciated that the terms “medial/lateral plane” and “anterior/posterior plane” have well-understood meanings in the art of orthopaedic implants. As used herein, these terms refer to the respective anatomical planes of a patient when the orthopaedic implant  10  is implanted in the patient. 
     The adaptor  14  may be configured such that the axis  48  is offset from and angled relative to the axis  46  by any amount suitable for implantation. For example, in one particular embodiment, the axis  48  is offset from the axis  46  by a distance  50  of about two millimeters to about eight millimeters when the axes  46 ,  48  are viewed in medial/lateral plane (see  FIG. 1 ). Additionally, the axes  46 ,  48  define an angle  52  therebetween greater than one degree. For example, in one particular embodiment, the angle  52  defined between the axes  46 ,  48  is in the range of about one degree to about five degrees. It should be appreciated, however, that other amounts of offset and angulation may be used in other embodiments based on the particular implementation, bone anatomy of the patient, and the like. 
     It should be also appreciated that, in use, an orthopaedic surgeon may select an adaptor  14  having a desirable offset and angulation for the particular patient. For example, as illustrated in  FIGS. 1-3 , because the stem extension  16  is offset in the medial/lateral plane and angled in the anterior/posterior plane when the adaptor  14  is used, the stem extension  16  may be positioned in an improved position for implantation in the particular patient. Additionally, it should be appreciated that the adaptor  14  may be used with an orthopaedic implant configured for the left knee joint or the right knee joint of the patient. Depending on the particular knee joint to be replaced, the adaptor  14  may be secured to the tibial tray  18  such that the offset and angle of the stem extension  16  is in the correct direction and/or anatomical plane for the particular knee joint (e.g., for the left or right knee joint of the patient). 
     It should be also appreciated that the adaptor  14  may be used with any one of a number of knee prosthetic components and stem extensions to offset the stem extension  16  in a first anatomical plane and angle the stem extension  16  in a second anatomical plane, which is orthogonal to the first anatomical plane. That is, in some embodiments, the adaptor  14  may be used to offset the stem extension  16  in the medial/lateral plane and angle the stem extension  16  in the anterior/posterior plane (see  FIGS. 1-3 ). Alternatively, in other embodiments, the adaptor  14  may be configured to offset the stem extension  16  in the anterior/posterior plane and angle the stem extension  16  in the medial/lateral plane. For example, as illustrated in  FIGS. 4-6 , the adaptor  14  may be used with the knee prosthetic component  12  to offset the stem extension  16  in the anterior/posterior plane and angulate the stem extension  16  in the medial/lateral plane. 
     Although the knee prosthetic component  12  is embodied as a tibial tray in the embodiment of  FIGS. 1-3 , the knee prosthetic component  12  may be embodied as other types of knee prosthetic components in other embodiments. For example, as illustrated in  FIGS. 4-6 , the knee prosthetic component  12  may be embodied as a femoral component  60 . Similar to the embodiment of  FIGS. 1-3 , the femoral component  60 , the adaptor  14 , and the stem extension  16  are configured to be coupled to together as illustrated in  FIG. 6 . The femoral component  60  includes a pair of condyles  62 ,  64  and a platform  66  defined between the condyles  62 ,  64 . The platform  66  includes an upper surface  68  and a lower surface  70 . 
     The femoral component  60  is configured to be coupled to a surgically prepared surface of the distal end of a patient&#39;s femur (not shown). When the femoral component  60  is coupled to the patient&#39;s femur, the adaptor  14  and the stem extension  16  are embedded in the patient&#39;s femur to thereby secure the femoral component  60  to the patient&#39;s bone. In use, the condyles  62 ,  64  replace the natural condyles of the patient&#39;s femur and are configured to articulate on the proximal end of the patient&#39;s natural or surgically prepared tibia. 
     As discussed above, the adaptor  14  is configured to be coupled with the femoral component  60  and the stem extension  16 . As such, as described above in regard to  FIGS. 1-3 , the mounting end  28  may include any number of apertures, protrusions, grooves, and/or other structures necessary to facilitate the securing of the adaptor  14  to the femoral component  60 . For example, in the embodiment illustrated in  FIGS. 4-6 , the mounting end  28  is configured to be coupled to the upper surface  68  of the platform  66  of the femoral component  60 . To do so, a bolt  74  or other securing device may be inserted through an aperture  72  defined in the platform  66  of the femoral component  60  and threaded into the threaded aperture  36  of the mounting end  28  to secure the adaptor  14  to the femoral component  60 . The mounting end  28  may or may not be tapered. 
     In other embodiments, the mounting end  28  of the adaptor  14  may include other or additional structures to facilitate the coupling of the adaptor  14  to the femoral component  60 . For example, in some embodiments, the femoral component  60  may include a stem (not shown) extending upwardly from the upper surface  68  of the platform  66 . In such embodiments, the mounting end  28  may be configured to be coupled to the stem of the femoral component  60 . For example, in such embodiments, the mounting end  28  may be tapered and sized to be received in an aperture of the stem of the femoral component  60 . In other embodiments, the mounting end  28  may include a threaded stud extending therefrom and configured to be received in a corresponding threaded aperture defined in the end of the stem of the femoral component  60 . Alternatively, the distal end of the stem of the femoral component  60  may be threaded and configured to be received in a threaded aperture defined in the mounting end  28  of the adaptor  14 . 
     As discussed above in regard to  FIGS. 1-3 , the adaptor  14  also includes the mounting end  40  configured to be coupled with the stem extension  16 . The mounting end  40  may include any number of apertures, protrusions, grooves, and/or other structures necessary to facilitate the securing of the adaptor  14  and the stem extension  16 . Again, when the femoral component  60 , the adaptor  14 , and the stem extension  16  are coupled together, the position of the stem extension  16  is altered. In contrast with the embodiment of  FIGS. 1-3 , the adaptor  14  is coupled with the femoral component  60  and stem extension  16  such that the axis  48  defined by the mounting end  40  is angled with respect to the axis  46  defined by the mounting end  28  when the axes  46 ,  48  are viewed in the medial/lateral plane (see  FIG. 4 ). Additionally, the axis  48  defined by the mounting end  40  is offset from and parallel to the axis  46  defined by the mounting end  28  when the axes  46 ,  48  are viewed in the anterior/posterior plane (see  FIG. 5 ). 
     The adaptor  14  may be configured such that the axis  48  is offset from and angled relative to the axis  46  by any amount suitable for implantation. For example, in one particular embodiment, the angle  76  defined between the axes  46 ,  48  is in the range of about one degree to about nine degrees (see  FIG. 4 ). Additionally, in one particular embodiment, the axis  48  is offset from the axis  46  by the distance  78  of about two millimeters to about eight millimeters when the axes  46 ,  48  are viewed in the anterior/posterior plane (see  FIG. 5 ). Again, it should be appreciated that other amounts of offset and angulation may be used in other embodiments based on the particular implementation, bone anatomy of the patient, and the like. 
     Although the adaptor  14  and the stem extension  16  are illustrated in  FIGS. 1-6  as separate pieces, the adaptor  14  and the stem extension  16  may be integral to each other in other embodiments. For example, as illustrated in  FIGS. 7 and 8 , the orthopaedic implant  10  may include the knee prosthetic component  12  and a stem extension  80 . The stem extension  80  is configured to be coupled with the knee prosthetic component  12 . The knee prosthetic component  12  may be embodied as a tibial tray, a femoral component, or any type of knee prosthetic component configured to receive a stem extension. As such, the stem extension  80  includes a mounting end  82  and an elongated shaft  84 . The elongated shaft  84  extends from the mounting end  82 . Additionally, the mounting end  82  is configured to be coupled to the knee prosthetic component  12 . The mounting end  82  may include any number of apertures, protrusions, grooves, and/or other structures necessary to facilitate the securing of stem extension  80  to the knee prosthetic component  12 . 
     The stem extension  80  is configured such that the position of the elongated shaft  84  is altered relative to the knee prosthetic component  12 . As illustrated in  FIGS. 7 and 8 , the mounting end  82  defines an axis  86 . Additionally, the elongated shaft  84  defines an axis  88 . Similar to axes  46 ,  48  discussed above in regard to  FIGS. 1-3 , the axis  88  defined by the elongated shaft  84  is offset from and parallel to the axis  86  defined by the mounting end  82  by a distance  90  when the axes  86 ,  88  are viewed in the medial/lateral plane (see  FIG. 7 ). Additionally, an angle  92  is defined between the axes  86 ,  88  when the axes  86 ,  88  are viewed in the anterior/posterior plane (see  FIG. 8 ). 
     Similar to the adaptor  14 , the stem extension  80  may be configured such that the axis  88  is offset from and angled relative to the axis  86  by any amount suitable for implantation. For example, in one particular embodiment, the axis  88  is offset from the axis  86  by the distance  90  of about two millimeters to about eight millimeters when the axes  86 ,  88  are viewed in the medial/lateral plane (see  FIG. 7 ). Additionally, the axes  86 ,  88  define an angle  92  therebetween greater than one degree when the axes  86 ,  88  are viewed in the anterior/posterior plane (see  FIG. 8 ). For example, in one particular embodiment, the angle  92  defined between the axes  86 ,  88  is in the range of about one degree to about five degrees. In other embodiments, the angle  92  defined between the axes  86 ,  88  may be in the range of about one degree to about nine degrees. 
     It should be appreciated, however, that other amounts of offset and angulation may be used in other embodiments based on the particular implementation, bone anatomy of the patient, and the like. It should also be appreciated that the stem extension  80  is configured to be used with a particular knee joint, either the left knee joint or right knee joint of the patient. A different embodiment of stem extension  80  may be required for use with the other knee joint such that the offset and angulation of the elongated shaft  84  is proper for the particular knee joint. 
     It should also be appreciated that the stem extension  80  can be used with any one of a number of knee prosthetic components to offset the elongated shaft  84  in a first anatomical plane and angle the elongated shaft  84  in a second anatomical plane, which is orthogonal to the first anatomical plane. That is, in some embodiments, the stem extension  80  may offset the elongated shaft  84  in the medial/lateral plane and angle the elongated shaft  84  in the anterior/posterior plane (see  FIGS. 7 and 8 ). Alternatively, in other embodiments, the stem extension  80  may be configured to offset the elongated shaft  84  in the anterior/posterior plane and angle the elongated shaft  84  in the medial/lateral plane. 
     In some embodiments, the adaptor  14  may be formed from multiple pieces. For example, as illustrated in  FIGS. 9-11 , the adaptor  14  of  FIGS. 1-6  may be embodied a first or knee prosthetic component piece  100  and a second or stem extension piece  102  removably coupled to each other. In addition, the first piece  100  is configured to be coupled to the knee prosthetic component  12 . Similarly, the second piece  102  is also configured to be coupled to the stem extension  16 . 
     In such embodiments, the first piece  100  of the adaptor  14  includes the mounting end  28  and a mounting plate  103  having a mounting surface  104 . The second piece  102  of the adaptor  14  includes the mounting end  40  and a mounting plate  105  having a mounting surface  106 . When the pieces  100 ,  102  of the adaptor  14  are coupled together, the mounting surfaces  104 ,  106  confront or abut each other. As such, the mounting surfaces  104 ,  106  may include any number of apertures, protrusions, grooves, and/or other structures necessary to facilitate the securing of the first piece  100  to the second piece  102 . For example, referring to  FIG. 10 , the mounting plate  103  of the first piece  100  includes a threaded aperture  108 . The mounting plate  105  of the second piece  102  includes a hole  110 . A bolt  112  is threaded into the hole  110  of mounting surface  106  and the threaded aperture  108  of mounting surface  104  to secure piece  102  to piece  100 . Additionally, the mounting surface  104  includes a number of teeth  114 . Similarly, the mounting surface  106  includes a number of teeth  116  that interdigitate with the number of teeth  114  of mounting surface  104  when the piece  102  is secured to the piece  100 . 
     In some embodiments, the second piece  102  may be coupled to the first piece  100  at any one of a number of positions such that the angle  52  (see  FIG. 11 ) defined between the axes  46 ,  48  when the axes  46 ,  48  are viewed in the anterior/posterior plane is adjustable. In other embodiments, the second piece  102  may be coupled to the first piece  100  at any one of a number of positions such that the angle defined between the axes  46 ,  48  when the axes  46 ,  48  are viewed in the medial/lateral plane is adjustable. Due to the interaction of the number of teeth  114 ,  116 , the position of the second piece  102  of the adaptor  14  relative to the first piece  100  may be adjusted in a stepwise manner. Once the desired position as been reached, the pieces  100 ,  102  may be secured to each other via the bolt  112 . 
     Alternatively, as illustrated in  FIGS. 12 and 13 , the second piece  102  of the adaptor  14  may be integral with the stem extension  16 . That is, the first piece  100  of the adaptor  14  may be configured to be removably coupled to a stem extension  120 . The stem extension  120  includes a mounting plate  121  having a mounting surface  122  and an elongated shaft  124  extending from the mounting plate  121 . When the stem extension  120  and the first piece  100  are coupled together, the mounting surfaces  104 ,  122  confront or abut each other. As such, as described above in regard to  FIGS. 9-11 , the mounting surfaces  104 ,  122  may include any number of apertures, protrusions, grooves, and/or other structures necessary to facilitate the securing of the stem extension  120  to the first piece  100 . For example, referring to  FIG. 12 , the mounting plate  121  of the stem extension  120  includes a hole  126 . A bolt  112  is threaded into the hole  126  of mounting surface  122  and the threaded aperture  108  of the mounting surface  104  to secure the stem extension  120  to the piece  100 . Additionally, the mounting surface  122  of the stem extension  120  may include a number of teeth  128  that interdigitate with the number of teeth  114  of mounting surface  104  when the stem extension  120  is secured to the piece  100 . 
     In some embodiments, the stem extension  120  may be coupled to the first piece  100  at any one of a number of positions such that an angle  132  (see  FIG. 13 ) defined between the axis  46  defined by the mounting end  28  and an axis  130  defined by the elongated shaft  124 —when the axes  46 ,  48  are viewed in the anterior/posterior plane is adjustable. In other embodiments, the stem extension  120  may be coupled to the first piece  100  at any one of a number of positions such that an angle defined between the axis  46  defined by the mounting end  28  and an axis  130  defined by the elongated shaft  124  when the axes  46 ,  48  are viewed in the medial/lateral plane is adjustable. Due to the interaction of the number of teeth  114 ,  128 , the position of the stem extension  120  relative to the first piece  100  may be adjusted in a stepwise manner. Once the desired position as been reached, the first piece  100  and the stem extension  120  may be secured to each other via the bolt  112 . 
     While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. 
     There are a plurality of advantages of the present disclosure arising from the various features of the apparatus, system, and method described herein. It will be noted that alternative embodiments of the apparatus, system, and method of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the apparatus, system, and method that incorporate one or more of the features of the present invention and fall within the spirit and scope of the present disclosure as defined by the appended claims.