Patent Publication Number: US-2023149175-A1

Title: Orthopaedic surgical instrument system and a method of trialing an orthopaedic prosthetic assembly

Description:
This application is a divisional of and claims priority to U.S. patent application Ser. No. 17/038,710, which was filed on Sep. 30, 2020, the entirety of which is expressly incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to orthopaedic surgical instruments, and particularly to a tibial trial component for use in trialing an orthopaedic prosthetic. 
     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. In a revision knee surgery, the previously-implanted knee prosthesis, sometimes referred to as a “primary knee prosthesis,” is surgically removed and a replacement or revision knee prosthesis is implanted. 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. In some cases when soft tissue may not be adequate, a hinged knee prosthesis is implanted, where the polymer insert or bearing links the femoral component to the insert to allow for flexion and extension of the knee. 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. 
     During joint arthroplasty, 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, a tibial insert trial that may be used to size and select a prosthetic tibial insert, and a stem trial that may be used to size and select a prosthetic stem component. 
     SUMMARY 
     According to one aspect of the disclosure, an orthopaedic surgical instrument system includes a tibial base trial, a hinged tibial insert trial, a post adapter, and a femoral component. The tibial base trial includes a plate configured to be positioned on a proximal end of a patient&#39;s tibia and a post extending outwardly from a superior surface of the plate. The hinged tibial insert trial includes an inferior surface configured to confront the superior surface of the plate. The hinged tibial insert further includes a pair of curved surfaces positioned opposite the inferior surface, a spine positioned between the pair of curved surfaces, a housing hingedly coupled to the spine and including a button mechanism having an elongated plunger pin, and a central opening defined in the inferior surface. The post adapter is sized to be positioned in the central opening defined in the hinged tibial insert trial. The post adapter includes an outer wall and an aperture defined in the outer wall that is sized to receive the post of the tibial base trial. The femoral component includes a pair of curved surfaces configured to confront the pair of curved surfaces of the hinged tibial insert trial. The femoral component further includes anterior flange positioned between the pair of curved surfaces, a femoral box defined between the pair of curved surfaces and configured to receive the housing of the hinged tibial insert trial, and a pocket defined in an inner wall of the anterior flange and configured to receive a first end of the elongated plunger pin. The button mechanism is operable to retract the first end of the elongated plunger pin within the housing. 
     In an embodiment, the post adapter includes a locking tab positioned in a central passageway defined in the post adapter. In an embodiment, the post includes a stem extending outwardly from the plate to the superior flange, and the locking tab includes a pair of arms configured to engage the stem of the post, wherein each arm of the pair of arms is a spring clip. 
     In an embodiment, the housing includes a medial wall having a transverse bore defined in the medial wall and extending in a medial-lateral direction, and a lateral wall having a transverse bore defined in the lateral wall and extending in the medial-lateral direction. The spine includes a transverse bore extending in the medial-lateral direction. The hinged tibial insert trial includes an elongated pin positioned in the transverse bores of the housing and the spine to couple the housing to the spine. In an embodiment, the housing of the hinged tibial insert trial is configured to rotate about an axis extending through the elongated pin. 
     In an embodiment, the orthopaedic surgical instrument system further includes a trial shim including an inferior surface configured to confront the superior surface of the plate, a superior surface including a superior plateau sized to be received by a recess defined in the inferior surface of the hinged tibial insert trial, and a central passageway defined in the trial shim and sized to receive the post adapter. 
     In an embodiment, the housing includes a hook extending posteriorly and including a curved inferior surface. The femoral component includes a shelf extending into the femoral box and including a curved superior surface configured to confront the curved inferior surface of the housing. In an embodiment, the femoral component comprises a prosthetic implant. 
     In an embodiment, the housing includes an anterior wall having a bore defined in the anterior wall. The first end of the plunger pin selectively extends through the bore in the anterior wall, and the button mechanism includes a spring configured to bias the first end of the plunger pin to extend through the bore. In an embodiment, the housing includes a medial wall and a lateral wall, wherein the medial wall, the lateral wall, and the anterior wall cooperate to define a button chamber accessible through the bore in the anterior wall, and wherein the button mechanism is positioned within the button chamber. The button mechanism includes a button plate coupled to the plunger pin and extending through an inferior opening in the button chamber. 
     According to another aspect, an orthopaedic surgical instrument comprises a hinged tibial insert trial that includes an inferior surface configured to confront a superior surface of a tibial base trial, a pair of curved surfaces positioned opposite the inferior surface, a central opening defined in the inferior surface, a spine positioned between the pair of curved surfaces, and a housing hingedly coupled to the spine and including a button mechanism having an elongated plunger pin having a first end that selectively extends out of the housing, wherein the button mechanism is operable to retract the first end of the elongated plunger pin within the housing. 
     In an embodiment, the orthopaedic surgical instrument further includes an elongated pin, wherein the housing includes a medial wall having a transverse bore defined in the medial wall and extending in a medial-lateral direction and a lateral wall having a transverse bore defined in the lateral wall and extending in the medial-lateral direction. The spine includes a transverse bore extending in the medial-lateral direction, and the elongated pin is positioned in the transverse bores of the housing and the spine to couple the housing to the spine. In an embodiment, the housing is configured to rotate about an axis extending through the elongated pin. 
     In an embodiment, the housing includes an anterior wall having a bore defined in the anterior wall, the first end of the plunger pin selectively extends through the bore in the anterior wall, and the button mechanism includes a spring configured to bias the first end of the plunger pin to extend through the bore. In an embodiment, the housing includes a medial wall and a lateral wall, wherein the medial wall, the lateral wall, and the anterior wall cooperate to define a button chamber accessible through the bore in the anterior wall, and wherein the button mechanism is positioned within the button chamber. The button mechanism includes a button plate coupled to the plunger pin and extending through an inferior opening in the button chamber. In an embodiment, the spine includes a bore extending generally in an anterior-posterior direction and configured to receive a shank of the plunger pin. 
     According to another aspect, a method of assembling a surgical instrument system includes clipping a base post adapter onto a post of a tibial base trial, wherein the tibial base trial is positioned on a proximal end of a patient&#39;s tibia; placing a hinged tibial insert trial on the base post adapter in response to clipping the base post adapter; positioning the patient&#39;s knee joint in less than about 45 degrees of flexion in response to placing the hinged tibial insert trial; depressing a button mechanism of the hinged tibial insert trial causing retraction of a plunger pin; inserting a housing of the hinged tibial insert trial into a femoral box defined in a femoral component through a gap defined between a pair of curved surfaces of the femoral component while depressing the button mechanism and in response to positioning the patient&#39;s knee joint; and releasing the button mechanism in response to inserting the housing. 
     In an embodiment, the method further includes moving the patient&#39;s knee joint through a range of motion including extension and flexion in response to releasing the button mechanism. In an embodiment, the method further includes positioning the patient&#39;s knee joint in less than about 45 degrees of flexion in response to moving the patient&#39;s knee joint through the range of motion; and removing the housing of the hinged tibial insert trial from the femoral box while depressing the button mechanism and in response to positioning the patient&#39;s knee joint. 
     In an embodiment, the method further includes attaching a trial shim to an inferior surface of the hinged tibial insert trial; wherein placing the hinged tibial insert trial on the base post adapter includes placing the hinged tibial insert trial and the trial shim on the base post adapter in response to attaching the trial shim. 
     BRIEF DESCRIPTION 
     The detailed description particularly refers to the following figures, in which: 
       FIG.  1    is an exploded view of an orthopaedic surgical instrument system in accordance with one embodiment; 
       FIG.  2    is a bottom plan view of a base post adapter shown in  FIG.  1   ; 
       FIG.  3    is a bottom plan view of a hinged tibial insert trial shown in  FIG.  1   ; 
       FIG.  4    is a perspective view of the hinged tibial insert trial shown in  FIG.  1   ; 
       FIG.  5    is a perspective view of the orthopaedic surgical instrument system of  FIG.  1   ; 
       FIG.  6    is a cross-sectional view taken along the line  6 - 6  in  FIG.  5   ; 
       FIG.  7    is a perspective view of a patient&#39;s surgically prepared knee joint; 
       FIG.  8    is a perspective view of a femoral component and a tibial base trial of  FIG.  1    positioned in the patient&#39;s surgically prepared knee joint; 
       FIG.  9    is a perspective view of a spacer block inserted in the patient&#39;s knee joint; 
       FIG.  10    is a perspective view of a base trial post adapter being attached to the tibial base trial of  FIGS.  8 - 9   ; 
       FIG.  11    is a perspective view of a trial shim being attached to a hinged tibial insert trial of  FIG.  1   ; 
       FIG.  12    is a perspective view of the hinged tibial insert trial of  FIG.  1    being attached to the tibial base trial post adapter shown in  FIG.  10   ; 
       FIG.  13    is a perspective view of the hinged tibial insert trial shown in  FIG.  12    being inserted into the femoral component; 
       FIG.  14    is a perspective view of the assembled orthopaedic surgical instrument system of  FIG.  1    positioned in the surgically prepared knee joint; and 
       FIGS.  15 - 16    are perspective views of the hinged tibial insert trial shown in  FIG.  14    being removed from the femoral component. 
    
    
     DETAILED DESCRIPTION 
     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 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. 
     Referring now to  FIGS.  1 - 6    an orthopaedic surgical instrument system  10  includes a tibial base trial component  20 , a tibial base post adapter  18 , and a hinged tibial insert trial component  14  configured to be selectively coupled to the tibial base trial  20  using the tibial base post adapter  18 . The tibial base trial component  20  and the hinged tibial insert trial component  14  may be utilized with a femoral component  12  to size and select a tibial prosthesis for implantation into a patient&#39;s surgically-prepared tibia. The femoral component  12  may be a femoral trial component as shown in  FIG.  1    or, in some embodiments, a femoral implant or other femoral component. It should be appreciated that the system  10  may include a number of trial components  14 ,  20  and femoral trial components of different sizes to accommodate a range of patient anatomies. 
     As described in greater detail below, the base post adapter  18  is configured to removably secure to the tibial base trial  20 , and the hinged tibial insert trial  14  and/or a trial shim  16  attached to the hinged tibial insert trial  14  may be positioned on the base post adapter  18 . It should be understood that in some embodiments, the hinged tibial insert trial  14  and the trial shim  16  may be combined in a single tibial insert trial component. The system  10  may include multiple such combined tibial insert trial components, for example each having different sizes and/or thicknesses. In some embodiments, the base post adapter  18  may also be included in such a combined tibial insert trial component. 
     The hinged tibial insert trial  14  is configured to be removably secured to the femoral component  12  by a retention device  15 , which is illustratively embodied as a pushbutton release system  170 . During a surgical procedure, the surgeon may evaluate the range of motion of the patient&#39;s leg with the base trial component  20 , the hinged tibial insert trial component  14 , and the femoral component  12  positioned in the knee joint, assessing, among other things, the stability of the knee and the displacement of the joint. The hinged tibial insert trial  14  is configured to be detached from the femoral component  12  and from the base post adapter  18  during the surgical procedure and replaced with a hinged tibial insert trial  14  and/or shim  16  of different size to permit the surgeon to evaluate a range of possible implant sizes and select the one that provides the best performance. 
     The tibial base trial component  20  is configured to be positioned on a surgically-prepared proximal end of a patient&#39;s tibia. In the illustrative embodiment, the base trial  20  includes a plate  22  shaped to be positioned on a proximal end of a patient&#39;s tibia. The plate  22  has a superior surface  26 , an inferior surface  28 , and an outer side wall  30  extending between the surfaces  26 ,  28 . The outer side wall  30  has an anterior section  32  and a posterior section  34  shaped to match a proximal end of a resected tibia. In the illustrative embodiment, the anterior section  32  of the side wall  30  is convexly curved, and the posterior section  34  is concavely curved. It should be appreciated that the tibial base trial  20  may be formed in a number of different sizes to accommodate tibias of various sizes. 
     The tibial base trial  20  may receive a pin  24 , which when attached to the tibial base trial  20  extends downwardly from the inferior surface  28  of the plate  22 . The pin  24  is sized to be received in a notch of a surgical instrument inserted into the proximal end of the patient&#39;s tibia. Such instruments may include, for example, an elongated broach or stem trial component sized to be positioned in a patient&#39;s intramedullary canal. The plate  22  also includes a number of fastener guides. Each fastener guide illustrative includes a bore configured to receive a fastener such as a fixation pin, which may be utilized to secure the tibial base trial  20  to the proximal end of the patient&#39;s tibia. 
     The tibial base trial  20  includes a post  36  that extends outwardly from the superior surface  26  of the plate  22  along a longitudinal axis  38 . The post  36  is configured to secure to the base post adapter  18 . The post  36  includes an inferior flange  40  extending from the superior surface  26  of the plate  22 , a stem  42  extending from the inferior flange  40 , and a superior flange  44  extending from the stem  42  to a proximal end of the post  36 . The stem  42  includes an outer surface  46  having a radius from the longitudinal axis  38  of the post  36 . The flanges  40 ,  44  each include an outer surface  48  having a radius from the longitudinal axis  38 . The radius of the outer surfaces  48  is larger than the radius of the outer surface  46 . Thus, a channel  50  is defined between the inferior flange  40  and the superior flange  44 . In particular, the channel  50  is defined between an inferior surface of the superior flange  44  and a superior surface of the inferior flange  40 . As described below, a locking mechanism of the base post adapter  18  is configured to engage the stem  42  of the post  36  within the channel  50 . 
     As shown in  FIGS.  1 - 2   , the base post adapter  18  of the hinged tibial insert trial component  14  includes an annular body  52  having a superior ring  54  and an inferior extension  56  extending inferiorly from the superior ring  54 . The annular body  52  includes an outer surface  58  and a curved inner surface  60  positioned opposite the outer surface  58 . The inner surface  60  defines a central passageway  62  through the base post adapter  18  that is sized to be positioned over the post  36  of the tibial base trial  20 . 
     The inferior extension  56  includes a pair of curved arms  64 ,  66  that extend around the central passageway  62 , and an aperture  68  is defined between the arms  64 ,  66 . The aperture  68  includes a slot  70  positioned at an inferior end of the aperture  68 , and another slot  72  positioned superior to the slot  70 . The slot  70  is sized to receive the stem  42  of the post  36 , and the slot  72  is sized to receive the superior flange  44  of the post  36 . 
     In some embodiment, a locking tab  74  may be positioned within the central passageway  62 . The locking tab  74  includes a trunk extending inward from the inner surface  60  into the central passageway  62 . The locking tab  74  also includes a pair of arms  76  extending from the trunk  66 . Each arm  76  includes a curved inner surface that corresponds to the outer surface  46  of the stem  42 , and a gap is formed between an outer surface of each arm  76  and the curved inner surface  60 . An opening is defined between the arms  76  such that each arm  76  is configured as a spring clip that can deflect into the respective gap to position the locking tab  74  on the post  36  of the tibial base trial  20 . When the base post adapter  18  is secured to the tibial base trial  20 , the arms  76  of the locking tab  74  are configured to position within the channel  50  defined between the superior flange  44  and the inferior flange  40 , as described below. Additionally or alternatively, in some embodiments the arms  64 ,  66  of the inferior extension  56  may be configured as spring clips configured to position within the channel  50 . 
     As shown in  FIG.  1   , the instrument system  10  may include a trial shim  16  configured to be selectively attached to the hinged tibial insert trial  14 . The shim  16  includes a plate  78  shaped to confront the superior surface  26  of the tibial base trial  20 . The shim  16  has a superior surface  80 , an inferior surface  82 , and an outer side wall  84  extending between the surfaces  80 ,  82 . It should be understood that in some embodiments, the system  10  may be assembled with one of a number of different trial shims  16 . Each trial shim  16  may have a different thickness; that is, the outer side wall  84  of each trial shim  16  may have a different height. 
     The outer side wall  84  of the trial shim  16  further includes an anterior section  86  and a posterior section  88 . In the illustrative embodiment, the anterior section  86  of the side wall  84  is convexly curved, and the posterior section  88  is concavely curved. An oval notch  87  is defined in the anterior section  86 , and the posterior section  88  further includes a straight ledge  90 . As described further below, the ledge  90  may provide a grip surface for a surgeon to use when assembling or disassembling the system  10 . 
     The trial shim  16  further includes a superior plateau  92  positioned on the anterior section  86  of the outer side wall  84 . A pair of locking tabs  93  extend posteriorly from the superior plateau  92  toward the posterior section  88 . As described further below, the superior plateau  92  and the outer side wall  84  are sized to be received and retained by the hinged tibial insert trial  14 . The oval notch  87  and the locking tabs  93  are configured to engage the hinged tibial insert trial  14 . A central passageway  94  through the trial shim  16  is defined by an inner side wall  96 . The central passageway  96  is sized to receive the outer surface  58  of the base post adapter  18 . 
     The hinged tibial insert trial  14  includes a body  98  and a housing  136  that may be hingedly connected by an elongated pin  168 . The body  98  has an inferior surface  100  and a superior surface  102 . The inferior surface  100  of the hinged tibial insert trial  14  is configured to confront the superior surface  26  of the plate  22  or the superior surface  80  of the trial shim  16 . The superior surface  102  includes a pair of curved surfaces  104 ,  106  positioned opposite the inferior surface  100  and configured to correspond to surfaces of the femoral component  12 , as described below. A spine  108  is positioned between the curved surfaces  104 ,  106  and extends superiorly from the superior surface  102 . A pin hole  110  extends medially-laterally between openings  112  formed in the spine  108 . The pin hole  110  is configured to receive the elongated pin  168  (described further below) to secure the body  98  to the housing  136 . The pin hole  110  may also be configured to receive bushings that are positioned in each opening  112 . A plunger hole  114  extends anteriorly-posteriorly between openings  116  formed in the spine  108 . The plunger hole  114  is configured to receive part of a button mechanism included in the housing  136  and described further below. 
     The body  98  includes an outer side wall  118  having an anterior section  120  that is shaped to match the anterior section  32  of the tibial base trial  20  and a posterior section  122  that is shaped to match the posterior section  34  of the base trial  20 . As shown in  FIG.  3   , the body  98  further includes an inner side wall  124  positioned opposite the outer side wall  118  along a perimeter of the inferior surface  100 . A recess  126  in the inferior surface  100  is defined by the inner side wall  124  and extends from the inferior surface  100  to a superior end wall  128 . A central opening  130  in the inferior surface  100  is further defined by an inner side wall  132  and extends from the inferior surface  100  to a superior end wall  134 . Similar to the central passageway  94  of the trial shim  16 , the central opening  130  is sized to receive the outer surface  58  of the base post adapter  18 . An intermediate side wall  135  is positioned opposite the inner side wall  132  and further defines a boundary of the recess  126 . The recess  126  is configured to receive the superior plateau  92  of the shim  16 , for example by a friction fit between the outer side wall  84  of the trial shim  16  and the inner side wall  124  of the body  98 . The recess  126  is further configured to engage the locking tabs  93  of the trial shim  16 . For example, in some embodiments, the locking tabs  93  may be embodied as spring clips that grip the intermediate side wall  135  and further retain the trial shim  16  against the body  98 . 
     Referring again to  FIG.  1   , the housing  136  includes a body  138  having medial-lateral sides  140 ,  142 . A pin hole  144 ,  146  extends through each of the respective sides  140 ,  142 , and is configured to receive the elongated pin  168 . As discussed further below, the housing  136  may be fixed to the body  98  by the pin  168 , which allows the housing  136  to rotate relative to the body  98  about the pin  168 . Each of the sides  140 ,  142  further includes a respective hook  148 ,  150  extending posteriorly from the respective side  140 ,  142 . Each hook  148 ,  150  includes a respective curved inferior surface  152 ,  154 . 
     As described above, the hinged tibial insert trial  14  is configured to be removably secured to the femoral trial component  12  by the retention device  15 , which will now be described in greater detail. In the illustrative embodiment, the retention device  15  includes a retained fastener (e.g., a plunger pin  172 ) that is selectively engaged with a bore (e.g., pocket  222 ) to secure the femoral trial component  12  to the tibial insert trial  14 . As shown in  FIG.  1   , the retention device is shown as a pushbutton release system  170  that includes the plunger pin  172 . The body  138  of the housing  136  further includes an anterior wall  156  positioned between the sides  140 ,  142 , and a bore  158 , which is sized to receive the plunger pin  172 , is defined through the anterior wall  156 . Similarly, an inner wall  160  is positioned between the sides  140 ,  142  posterior to the anterior wall  156 . A bore  162 , also sized to receive the plunger pin  172 , is defined through the inner wall  160 . The sides  140 ,  142  and the walls  156 ,  160  cooperate to define a button chamber  164  within the housing  136 . The button chamber  164  has an inferior opening  166  leading out of the housing  136 . 
     As shown in  FIG.  6   , when assembled, components of the pushbutton release system  170  may be positioned within the button chamber  164 . As shown in  FIGS.  1  and  6   , the pushbutton release system  170  includes a button mechanism including the elongated plunger pin  172 , a biasing element such as, for example, a spring  174 , and an actuator such as, for example, a button  176 . The plunger pin  172  extends from a posterior shank  178  to a cylindrical body  182  and then to a pointed end  186 . A flat collar  180  separates the posterior shank  178  and the cylindrical body  182 , and a circumferential groove  184  is defined in the cylindrical body  184 . 
     The button  176  is generally flat, and a bore  188  is defined therethrough. A retaining pin channel  190  is defined through an opening in a superior end of the button  176 . The retaining pin channel  190  opens into the bore  188  and is sized to receive a retaining pin or set screw  192 . A button surface  194  is positioned on an inferior end of the button  176 . As described below, a surgeon or other user may press the button surface  194  with a finger, forceps, or other tool to operate the pushbutton release system  170 . 
     Referring again to  FIG.  6   , when assembled, the button  176  is positioned within the button chamber  164  with the button surface  194  extending out of the inferior opening  166 . The plunger pin  172  is also positioned within the button chamber, and extends through the bores  162 ,  188 ,  158  of the inner wall  160 , the button  176 , and the anterior wall  156 , respectively. The circumferential groove  184  of the plunger pin  172  is positioned within the bore  188 , and the retaining pin  192  also extends through the retaining pin channel  190  into the bore  188 . The retaining pin  192  thus retains the plunger pin  172  relative to the button  176 . Although illustrated as a retaining pin  192 , in other embodiments any technique may be used to retain the button  176  to the plunger pin  172 . The spring  174  surrounds the posterior shank  178  and is positioned between the inner wall  160  and the collar  180 , thus biasing the plunger pin  172  in an anterior direction toward the anterior wall  156  and biasing the button  176  into engagement with the inner surface of the anterior wall  156 . 
     As shown, the button  176  is biased into a position at which the pointed end  186  of the plunger pin  172  extends outward (anteriorly) of the anterior wall  156  through the bore  158 . In this position, the plunger pin  172  may engage the femoral component  12 , as described further below. In use, a surgeon may depress the button surface  194  of the button  176 , causing the plunger pin  172  to move posteriorly into the housing  136  into a different position and thereby retracting the pointed end  186  through the bore  158  into the button chamber  164 . In this posterior position, engagement of the plunger pin  172  with the femoral component  12  is prevented. Further, although illustrated as a pointed end  186 , it should be understood that the end  186  may be flat, round, or any other shape capable of engaging the femoral component  12 , as described further below. 
     As shown in  FIG.  4   , when the hinged tibial insert trial  14  is assembled, the housing  136  is attached to the body  98  using the pin  168 . The pin  168  passes through the pin holes  144 ,  146  of the housing  136  and through the pin hole  110  of the spine  108 , allowing the housing  136  to rotate about an imaginary axis extending through the pin holes  110 ,  144 ,  146  along the pin  168 . It should be understood that that the hinged tibial insert trial  14  may be assembled by a surgeon or other user and/or may be assembled pre-operatively (e.g., during manufacture). 
     Returning to  FIG.  1   , the femoral component  12  includes a body  196  having a pair of curved surfaces  198 ,  200  that are configured to articulate on the curved surfaces  104 ,  106  of the hinged tibial insert trial  14 . An anterior flange  202  connects the curved surfaces  198 ,  200 . A boss  204  extends superiorly from the body  196  and is configured to be attached to a surgical instrument such as a femoral broach, femoral stem trial, or other surgical instrument. 
     Inner walls  206  extend inwardly from the curved surfaces  198 ,  200  toward a superior wall  208 . Similarly, an inner wall  210  extends inwardly from the anterior flange  202  to the superior wall  208 . The inner walls  206 ,  210  and the superior wall  208  define a femoral box  212 . The femoral box  212  is accessible through an intercondylar notch  214 , which is an aperture between the curved surfaces  198 ,  200 . As shown in  FIGS.  5 - 6    and described further below, the femoral box  212  is configured to receive the housing  136  of the hinged tibial insert trial  14 . Each inner wall  206  includes a shelf  216  that projects into the femoral box  212  and is configured to receive a corresponding hook  148 ,  150  of the housing  136 . As shown, each shelf  216  includes a flat superior surface  218  and a curved anterior surface  220 . The surfaces  218 ,  220  are configured to engage the corresponding inferior surfaces  152 ,  154  of the hooks  148 ,  150 . Although illustrated as including a pair of surfaces  218 ,  220  that engage a corresponding pair of hooks  148 ,  150  of the housing  136 , it should be understood that in some embodiments, the femoral component  12  may include a single shelf surface projecting within the femoral box  212  that engages a corresponding hook of the housing  136 . 
     As shown in  FIG.  6   , a pocket  222  is defined in the inner wall  210  of the anterior flange  202 . The pocket  222  is configured to receive the pointed end  186  of the plunger pin  172  of the pushbutton release system  170 . Thus, and as described further below, the housing  136  of the tibial insert trial component  14  may be removably secured within the femoral box  212  of the femoral trial component  12 . 
     In an embodiment, multiple tibial insert trials  14  and trial shims  16  may be provided in different sizes and/or configurations. Because each tibial insert trial  14  and trial shim  16  are configured to be secured to the base post adapter  18 , the surgeon is able to assemble a hinged tibial insert trial  14  and trial shim  16  assembly of one size and configuration, evaluate the performance of that assembly, and then modify the hinged tibial insert trial component  14  and/or the trial shim  16  as necessary to determine intraoperatively the type and configuration of the tibial insert component to be implanted. 
     Referring now to  FIGS.  7 - 16   , portions of an orthopaedic surgical procedure utilizing the system  10  are shown. The surgeon first performs a resection of the proximal end of the patient&#39;s tibia  302  to surgically prepare the tibia  302  for trial reduction. For example, the surgically-prepared proximal end of the patient&#39;s tibia  302  includes a resected surface configured to receive the tibial base trial  20 . In an embodiment where the femoral component  12  is a trial component, the surgeon may also perform a resection of the distal end of the patient&#39;s femur  304  to surgically prepare the femur  304  for trial reduction. In an embodiment where the femoral component  12  is a primary femoral component (not shown) or other femoral implant, the surgeon may trial the hinged tibial insert trial component  14  with the primary femoral component or other femoral implant. As shown in  FIG.  8   , in the illustrative embodiment, the surgeon positions the tibial base trial  20  on the resected surface of the patient&#39;s tibia  302  and positions the femoral trial component  12  on the resected surface of the patient&#39;s femur  304 . 
     After placing the tibial base trial  20  on the patient&#39;s tibia  302  and the femoral component  12  on the patient&#39;s femur  304 , the surgeon evaluates the joint space. As illustrated in  FIG.  9   , the surgeon may insert a spacer block  306  of a joint distractor  308  into the patient&#39;s knee joint to evaluate the joint gap. The surgeon may evaluate the gap in flexion or extension. Typically, the patient&#39;s knee joint is distracted in extension an amount necessary to establish a generally rectangular joint gap. 
     After evaluating the joint space, the surgeon may perform an initial trial reduction with the instrument system  10 . In doing so, the surgeon uses the system  10  to evaluate and check the stability and kinematics of the patient&#39;s femur  304  and tibia  302  for implantation of a hinged knee prosthesis. As illustrated in  FIG.  10   , the surgeon advances the base post adapter  18  in the direction indicated by arrow  310  in order to clip the base post adapter  18  onto the post  36  of the tibial base trial  20 . As shown, the post  36  is received in the aperture  68 , and in particular the superior flange  44  of the post  36  is received in the superior slot  72 , and the stem  42  of the post  36  is received in the inferior slot  70 . 
     As the base post adapter  18  is advanced, the post  36  passes through the opening between the arms  76  of the locking tab  74 . The arms  76  of the locking tab  74  are received within the channel  50  defined between the superior flange  44  of the post  36  and the inferior flange  40  of the tibial base trial  20 . The arms  76  of the locking tab  74  deflect outward so that the stem  42  of the post  36  is received in the opening defined between the arms  76 . The arms  76  spring back to their original position to engage the stem  42  of the post  36  to secure the locking tab  74  to the post  36 , thereby preventing movement of the base post adapter  18  in an inferior-superior direction relative to the tibial base trial  20 . 
     As illustrated in  FIG.  11   , the surgeon may select a trial shim  16  for use with the hinged tibial insert trial  14 . As described above, trial shims  16  may be provided in different sizes and/or configurations. The combined thickness of a particular trial shim  16  and hinged tibial insert trial  14  corresponds to the thickness of a particular tibial insert prosthetic component. The surgeon may, for example, select the trial shim  16  and/or the hinged tibial insert trial  14  to achieve a thickness determined during joint evaluation with the spacer block  306  as shown in  FIG.  9   . It should be understood that in some embodiments, the hinged tibial insert trial  14  may be used without a trial shim  16 . 
     Still referring to  FIG.  11   , the selected trial shim  16  may be aligned with the inferior surface  100  of the hinged tibial insert trial  14 . The surgeon advances the trial shim  16  in the direction indicated by arrow  312 , and the superior plateau  92  of the trial shim  16  is received by the recess  126  of the hinged tibial insert trial  14 . The inner walls  124  of the hinged tibial insert trial  14  engage the outer wall  84  of the trial shim  16  and thus retain the trial shim  16  against the inferior surface  100  of the hinged tibial insert trial  14 . When assembled, the central passageway  94  of the trial shim  16  is aligned with the central opening  130  of the hinged tibial insert trial  14 . Depending on thickness of the shim  16 , the inferior surface  82  of the trial shim  16  may extend outward beyond the inferior surface  100  of the hinged tibial insert trial  14 . The surgeon may remove the trial shim  16  (for example, to attach a different trial shim  16  having a different thickness) by grasping the ledge  90  on the posterior section  88  of the trial shim  16  and separating the hinged tibial insert trial  14  from the trial shim  16 . 
     As illustrated in  FIG.  12   , after assembly with the trial shim  16 , the hinged tibial insert trial component  14  is aligned with the base post adapter  18  and the tibial base trial  20 . The surgeon advances the hinged tibial insert trial component  14  in the direction indicated by arrow  314  onto the base post adapter  18 . The outer surface  58  of the base post adapter  18  is received by the central opening  130  of the hinged tibial insert trial  14  and/or by the central passageway  94  of the trial shim  94 . Positioning the hinged tibial insert trial component  14  on the base post adapter  18  permits the hinged tibial insert trial component  14  to rotate relative to the tibial base trial  20 . 
     After being positioned on the tibial base trial  20 , the hinged tibial insert trial component  14  may be attached to the femoral trial  12 . As illustrated in  FIG.  13   , the surgeon positions the patient&#39;s knee joint at  45  degrees of flexion or less. The surgeon depresses the button surface  194  in the direction indicated by arrow  316 , causing the pointed end  186  of the plunger pin  172  to retract within the housing  136 . With the button surface  194  of the push release system  170  depressed, the housing  136  is inserted into the femoral box  212  in the direction indicated by arrow  318 . When the housing  136  is initially inserted, the anterior wall  156  may be tilted in an inferior direction toward the curved surfaces  104 ,  106 . During or after insertion, the housing  136  may be rotated back such that the posterior hooks  148 ,  150  move in the inferior direction toward the curved surfaces  104 ,  106 . Thus, as the housing  136  is inserted, the curved surfaces  152 ,  154  of the hooks  148 ,  150  engage the surfaces  218 ,  220  of the shelves  216  projecting within the femoral box  212 . When fully inserted, the housing  136  engages the superior wall  208  of the femoral component. The surgeon releases the button surface  194 , and the pointed end  186  is urged by the spring  174  to extend out of the housing  136  into the pocket  222  of the femoral component, thus retaining the housing  136  within the femoral component  12 . 
     As illustrated in  FIG.  14   , after attaching the hinged tibial insert trial  14  to the femoral trial  12 , the surgeon evaluates the knee joint. For example, the surgeon may carefully extend the knee of the patient, noting the anteroposterior stability, medial-lateral stability, and overall alignment in the anterior-posterior (“A/P”) plane and medial-lateral (“M/L”) plane. The hinged tibial insert trial component  14  may also be rotated about the axis  38  of the post  36  of the tibial base trial  20 . 
     After evaluating the knee joint, the surgeon removes the hinged tibial insert trial  14 , for example to exchange the hinged tibial insert trial  14  and/or the trial shim  16 . As illustrated in  FIG.  15   , the surgeon positions the patient&#39;s knee joint at  45  degrees of flexion or less. The surgeon depresses the button surface  194  in the direction indicated by the arrow  316 , causing the pointed end  186  of the plunger pin  172  to retract within the housing  136 . As illustrated in  FIG.  16   , with the button surface  194  of the pushbutton release system  170  depressed, the surgeon removes the hinged tibial insert trial  14  from the femoral component  12  in the direction indicated by arrow  320 . After being detached from the femoral component  12 , the hinged tibial insert trial  14  (including any attached trial shim  16 ) may be removed from the base post adapter  18  by being advanced superiorly. The base post adapter  18  is left secured to the post  36  of the tibial base trial  20  such that another hinged tibial insert trial  14  and/or another trial shim  16  may be secured to the base post adapter  18  for trialing. The surgeon may then select a second hinged tibial insert trial  14  and/or a second trial shim  16  to attach to the base post adapter  18 . The surgeon may then trial the second hinged tibial insert trial  14  and/or the second trial shim  16  as discussed above. 
     Although the retention device  15  is illustratively shown as a pushbutton release system  170 , it should be appreciated that in other embodiments the retention device  15  may take other forms. For example, the tibial insert trial component  14  might include other retained fasteners such as, for example, a threaded screw, which may be received in a corresponding threaded bore in the femoral trial component  12 . In other embodiments, the fastener may not be retained and/or may not be threaded. In still other embodiments, the fastener might be incorporated into the femoral trial component  12 , and the tibial insert trial component  14  might include the bore configured to receive the fastener. Similarly, the plunger pin  172  and pushbutton release system  170  might be included in the femoral trial component  12 , while the tibial insert trial component  14  has the pocket  222  sized to receive the plunger pin  172 . 
     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 method, apparatus, and system described herein. It will be noted that alternative embodiments of the method, apparatus, and system 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 method, apparatus, and system 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.