Abstract:
A tibial trial assembly for evaluating the stability and kinematics of a tibial implant, particularly a mobile bearing implant, prior to committing to the final preparation of the proximal tibia is described. The tibial trail assembly includes a tray trial adapted to be secured onto a resected proximal end of a patient&#39;s tibia. An evaluation bullet is either adapted to removably fit into a configured recess in the trial tray, or is integral therewith. A trunnion on the evaluation bullet accepts a recess in a corresponding articular tibial insert trial. The tibial insert trial is thus received on the trunnion. Preferably, the evaluation bullet is removable from the trial tray such that the remaining assembly is used to locate and guide (orient) the instrument(s) that prepare the tibia for the final implant. Typically, this includes broaching, drilling, or punching through the opening in the trial tray/plate.

Description:
PROVISIONAL PATENT APPLICATION 
   This application claims the benefit of U.S. Provisional Application Ser. No. 60/258,390, filed Dec. 27, 2000, the disclosure of such application being totally incorporated herein by reference in its entirety. 

   TECHNICAL FIELD OF THE INVENTION 
   The present invention relates generally to a surgical trial instrument assembly and, more particularly, to a method and apparatus for evaluating the stability and kinematic behavior of a mobile bearing knee implant prior to commitment to a final preparation of a proximal tibia. 
   BACKGROUND OF THE INVENTION 
   During the lifetime of a patient, it may be necessary to perform a joint replacement procedure on the patient as a result of, for example, disease or trauma. One such type of joint replacement procedure is a total knee replacement procedure in which a diseased and/or damaged knee joint is replaced with a prosthetic knee joint. A typical total knee replacement procedure utilizes a prosthesis that generally includes a femoral component, a tibial tray, and a tibial bearing insert. The femoral component generally includes a pair of laterally spaced apart condylar portions, the distal surfaces of which bear against a complementary pair of surfaces defined in the tibial bearing insert. The tibial tray typically includes a plate having a stem extending distally therefrom. The stem is implanted in a prepared medullary canal of the patient&#39;s tibia. Once implanted in such a manner, the tibial tray provides a surface on the proximal end of the tibia to which the tibial bearing insert may be affixed. 
   During performance of such a knee replacement procedure, the surgeon must evaluate the size and condition of the patient&#39;s bones (e.g. the patient&#39;s tibia) in order to determine the proper type and configuration of each of the various types of prosthetic components that are to be implanted. This procedure is known as trialing. 
   Surgeons prefer to check the stability and kinematic behavior of the implant prior to the final preparation of the tibia bone for the final implant. However, current trialing systems require the surgeon to prepare the bone for the final implant prior to checking the stability and behavior of the implant. In particular, current trialing systems require the proximal tibia to be broached, reamed, punched, or otherwise prepared in order to place an evaluation trial in place. This requires the surgeon to commit to the use of a mobile bearing tibial implant prior to being able to finish their evaluation of stability and kinematic behavior. 
   What is needed therefore is an apparatus and method for trialing a tibia implant. 
   What is further needed therefore is an apparatus and method for evaluating the stability and kinematic behavior of a mobile bearing knee implant during a total knee arthroplasty. 
   SUMMARY OF THE INVENTION 
   In accordance with one embodiment of the present invention, there is provided a trial tray assembly for evaluating the stability and kinematic behavior of a prosthetic knee implant prior to implanting the final prosthetic knee implant. The assembly includes a trial tray configured to be placed on a proximal end of a resected tibia, the trial tray having a plate with a configured opening. The assembly further includes an alignment handle detachably couplable to the plate. Moreover, the assembly includes an evaluation bullet having a profile corresponding in shape to the configured opening and removably received in the configured opening, the evaluation bullet including a trunnion adapted to receive a trial insert thereon, the trial insert mimicking the final prosthetic knee implant. 
   In accordance with another embodiment of the present invention, there is provided a method for evaluating the stability and kinematic behavior of a prosthetic knee implant prior to implanting a final prosthetic knee implant. The method includes the steps of (i) resecting a patient&#39;s proximal tibia, (ii) placing a trial tray onto the resected proximal tibia, the trial tray defined by a plate having a configured opening therein, (iii) placing an evaluation bullet into the configured opening, the evaluation bullet shaped to substantially conform to the configured opening and having a trunnion, (iv) placing an insert trial mimicking the final prosthetic knee implant having a recess therein onto the trunnion, and (v) moving the tibia to determine stability and kinematics of the insert trial. 
   In accordance with yet another embodiment of the present invention, there is provided an apparatus for evaluating the stability and kinematic behavior of a prosthetic knee implant before final implant of a prosthetic knee implant. The apparatus includes a trial tray having a configuration substantially corresponding to a shape of a resected tibia and including a cutout portion. The apparatus further includes a handle adapted to be removably attached to the trial tray. Moreover, the apparatus includes an evaluation bullet shaped to be removably received in the cutout portion and including a trunnion. Also, the apparatus includes a trial insert having a recess adapted to be removably received on the trunnion. 
   Pursuant to another embodiment of the present invention, there is provided a prosthesis evaluation assembly which includes a tray configured to be supported on a proximal end of a resected tibia, the tray having an opening defined therein. The prosthesis evaluation assembly further includes an evaluation member having (i) a lower portion configured to be received within the opening, and (ii) an upper portion configured to support a trial insert thereon. 
   In accordance with yet another embodiment of the present invention, there is provided a prosthesis evaluation assembly. The assembly includes a tray configured to be supported on a proximal end of a resected tibia, the tray having an opening defined therein. The assembly also includes an evaluation member having (i) a tray contact portion configured to be received within the opening, and (ii) an insert contact portion. In addition, the assembly includes a trial insert having a recess configured to receive the insert contact portion. 
   It is therefore an object of the present invention to provide a new and useful surgical assembly for evaluating the stability and kinematic behavior of a trial prosthetic implant prior to final prosthetic implant. 
   It is moreover an object of the present invention to provide an improved surgical assembly for evaluating the stability and kinematic behavior of a trial prosthetic implant prior to final prosthetic implant. 
   It is a further object of the present invention to provide a new and useful method of surgically evaluating the stability and kinematic behavior of a trial prosthetic implant prior to final prosthetic implant. 
   It is also an object of the present invention to provide an improved method of surgically evaluating the stability and kinematic behavior of a trial prosthetic implant prior to final prosthetic implant. 
   The above and other objects, features, and advantages of the present invention will become apparent from the following description and the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a trial tray and handle incorporating features in accordance with the principles of the present invention; 
       FIG. 2  is a top view of the trial tray and handle of  FIG. 1  situated on a proximally resected tibia in accordance with the principles of the present invention; 
       FIG. 3  is a top plan view of an embodiment of a lock-out evaluation bullet in accordance with the principles of the present invention; 
       FIG. 4  is a bottom plan view of the lock-out evaluation bullet of  FIG. 3 ; 
       FIG. 5  is a side plan view of the lock-out evaluation bullet of  FIG. 3  taken along line  5 — 5  thereof; 
       FIG. 6  is a side plan view of the lock-out evaluation bullet of  FIG. 3  taken along line  6 — 6  thereof; 
       FIG. 7  is a sectional view of the trunnion of the lock-out evaluation bullet of  FIG. 6  taken along line  7 — 7  thereof; 
       FIG. 8  is a top plan view of an embodiment of a pinned, rotational evaluation bullet in accordance with the principles of the present invention; 
       FIG. 9  is a bottom plan view of the pinned, rotational evaluation bullet of  FIG. 8 ; 
       FIG. 10  is a side plan view of the pinned, rotational evaluation bullet of  FIG. 8  taken along line  10 — 10  thereof; 
       FIG. 11  is a side plan view of the pinned, rotational evaluation bullet of  FIG. 8  taken along line  11 — 11  thereof; 
       FIG. 12  is a sectional view of the trunnion of the pinned, rotational evaluation bullet of  FIG. 11  taken along line  12 — 12  thereof; 
       FIG. 13  is a front perspective view of the present trial tray and handle situated on the resected tibia and accepting the lock-out evaluation bullet; 
       FIG. 14  is a side view of the present trial tray, handle and lock-out evaluation bullet of  FIG. 13  on the resected tibia accepting a tibial insert trial; 
       FIG. 15  is a front perspective view of the present trial tray, handle and lock-out evaluation bullet between the resected tibia and femur of  FIG. 13  for rotational alignment thereof; 
       FIG. 16  is a front perspective view of the present trial tray and handle situated on the resected tibia and accepting the pinned, rotational evaluation bullet; 
       FIG. 17  is a front view of the present trial tray and tibial insert trial of  FIG. 13  on the resected tibia; 
       FIG. 18  is a front view of the present trial tray and tibial insert trial of  FIG. 13  between the tibia and femur for evaluating rotation thereof; 
       FIG. 19  is a perspective view of the present trial tray without an evaluation bullet being secured to the resected tibia for final implant; and 
       FIG. 20  is a perspective view of the trial tray secured onto the resected tibia showing placement of a drill guide thereon. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has 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 invention to the particular form 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. 
   It should initially be appreciated that the present invention is used after proper resection of a patient&#39;s proximal tibia for evaluating the stability and kinematics of a mobile bearing implant therefor prior to committing to the final preparation of the proximal tibia. Proper resection of the proximal tibia is beyond the scope of the present disclosure. Reference should be made to an appropriate surgical manual for such resection. In particular, reference is preferably made to the P.F.C.® Sigma Rotating Platform Knee System with M. B. T. Tray, copyright 2000, by DePuy International LTD, a Johnson &amp; Johnson company, the disclosure of which is herein incorporated by reference in its entirety . 
   Referring now to  FIG. 1 , there is shown a trial tray assembly  10  having a trial tray  12  and a detachable alignment handle  14 . The trial tray  12  has a body  25 , preferably made of stainless steel, which is shaped to substantially correspond to the configuration of the patient&#39;s resected proximal tibia. The trial tray body  25  includes a cutout portion  32  that is partially surrounded by an inset ledge or rim  34 . The cutout portion  32  includes a first radially extending slot  36  and a second radially extending slot  38 . The inset ledge  34  is absent from the first and second radially extending slots  36  and  38 . As explained further below, the cutout portion  32  and slots  36 ,  38  are configured and adapted to receive and retain an evaluation bullet. 
   The trial tray  25  also includes a first recessed bore  40  disposed proximate the slot  36  and a second recessed bore  42  disposed proximate the slot  38 . The bores  40  and  42  are configured and adapted to receive fixation pins as explained below. In addition, the trial tray  25  includes a first slotted bore  26  in a sidewall thereof, and a second slotted bore  28  in the sidewall thereof. A third bore  30  is disposed between the first and second slotted bores  26  and  28 . These bores are adapted and configured to receive pins or prongs of the alignment handle  14  as described below. 
   The alignment handle  14  is defined by a stem  16  having a first flanged pin or prong  20  and a second flanged pin or prong  22 . The first and second flanged pins  20  and  22  are configured and adapted to be releasably received into the respective slotted bores  26  and  28  of the body  25  of the trial tray  12 . The stem  16  also has a retractable center pin  24  that is configured and adapted to be received in the center bore  30  of the body  25  of the trial tray  12 . A lever  18  controls the retraction and extension of the center pin  24 . 
   For attachment of the handle  14  to the trial tray  12 , the center pin  24  is retracted, and the flanged pins  20  and  22  are received into the slotted bores  26  and  28  respectively. Once the flanged pins  20  and  22  are received in the slotted bores  26  and  28 , the center pin  24  is extended into the bore  30 . The extension of the center pin  24  into the bore  30  prevents the flanged pins  20  and  22  from being removed from their respective slotted bores  26  and  28 . The lever  18  and/or the center pin  24  are preferably biased into an extended position. Removal of the handle  14  from the body  25  is accomplished in a reverse manner to installation or attachment thereof. 
   Referring to  FIG. 2 , the trial tray assembly  10  is shown placed onto the patient&#39;s resected, proximal tibia  50 . This is performed after resection of the proximal tibia, sizing of the trial tray  12 , and attachment of the handle  14  to the trial tray  12 . It should be appreciated that there are various sizes of trial trays to accommodate various sizes of a patient&#39;s tibia. Therefore, regardless of the size of the trial tray, the configuration and function is the same as described herein for each size. The surgeon must decide which trial tray best fits the patient&#39;s resected, proximal tibia. The trial tray  12  is now ready to receive an evaluation bullet. 
   Referring now to  FIGS. 3-7 , there is shown one embodiment of a tibia trial or evaluation bullet, generally designated  60 , that may be used in conjunction with the trial tray assembly  10  during a total knee replacement surgery/operation. The evaluation bullet  60  is a fixed or non-rotation (lock-off) evaluation bullet. As explained further below, the evaluation bullet  60  is used with a non-rotatable insert trial. 
   The evaluation bullet  60  is preferably made of stainless steel and is defined by a body  62 . The shape of the body  62  is substantially the same as the shape of the cutout portion  32  of the trial tray  12 . The body  62  also has a first prong  64  and a second prong  66 , each radially extending from therefrom in the same manner and substantially the same configuration as the slots  36  and  38  radially extend from the cutout portion  32 . The body  62  further includes a trunnion  68  that defines a bearing surface for a trial insert  100  (see FIG.  14 ). The trunnion  68  is generally dome-shape in cross section and includes a flat  70  on one side thereof. The flat  70  provides the non-rotational component of the bearing surface. 
   Referring to  FIGS. 8-12 , there is shown another embodiment of a tibia trial or evaluation bullet, generally designated  80 , that may be used in conjunction with the trial tray assembly  10  during a total knee replacement surgery/operation. The evaluation bullet  80  is a rotational evaluation bullet. As explained further below, the evaluation bullet  60  is used with a rotatable insert trial. 
   The evaluation bullet  80  is preferably made of stainless steel and is defined by a body  82 . The shape of the body  82  is substantially the same as the shape of the cutout portion  32  of the trial tray  12 . The body  82  also has a first prong  84  and a second prong  86 , each radially extending from therefrom in the same manner and substantially the same configuration as the slots  36  and  38  radially extend from the cutout portion  32 . The body  82  further includes a trunnion  88  that defines a bearing surface for a trial insert  110  (see FIG.  17 ). The trunnion  68  is generally arcuate-shaped in cross section and includes a concavity  90  on one side thereof. The concavity  90  provides a rotational bearing surface for the trial insert  110 . The first prong  84  includes a first mounting spike  85  extending therefrom while the second prong  86  includes a second mounting spike  87 . As explained further below, the spikes  85  and  87  temporarily affix the evaluation bullet  80  onto the resected tibia  50  in order to allow the trial insert  110  to rotate about the trunnion  88  by coaction between the trunnion  88 /concavity  90  and the trial insert  110 . 
   It should be appreciated that the two embodiments of the evaluation bullets  60  and  80  respectively shown in  FIGS. 3-7 , and  8 - 12 , are for use during performance of a joint replacement procedure such as a total knee replacement procedure. Therefore, although the present invention is herein exemplarily described in regard to performance of a total knee replacement procedure, certain of the concepts of the present invention may be utilized in regard to replacement procedures at numerous other joint locations throughout the body. 
   Referring to  FIG. 13 , the evaluation bullet  60  is shown being inserted into the cutout portion  32  of the body  25  of the trial tray  12  after the trial tray assembly  10  is positioned onto the resected tibia  50 . At this point, the trial tray assembly  10 , which now includes the evaluation bullet  60 , is ready to receive an insert trial that allows the surgeon to check the stability of the final implant. 
   Referring to  FIG. 14 , there is shown an insert trial  100  having a recess  102 , being inserted onto the trunnion  68  of the evaluation bullet  60 . The insert trial  100  is chosen to match the femoral size and style, and one that is either curved or stabilized, per the surgeon&#39;s preference. The recess  102  of the insert trial  100  is received on the trunnion  68  in a non-rotatable manner. When the insert trial  100  is in place, the knee of the patient is carefully extended, noting the anteroposterior stability, medial/lateral stability and overall alignment in the A/P and M/L plane. Various insert trials may be tried in order to ascertain which final implant will work best. 
   Referring to  FIG. 15 , rotational alignment of the tibial tray  25  is adjusted with the knee in full extension, using the handle  16  to rotate the tray  25  and insert trial  100  into congruency with the femoral trial  140 . The rotation of the trial tray  25  is usually centered on the junction between the medial and central one-third of the tibial tubercle. Once the appropriate position is located, it is marked  96  by electrocautery tool  94  on the anterior tibial cortex. Overall alignment may be confirmed using a two part alignment rod, attaching it to the handle  16 . 
   The trial reduction explained above with reference to a non-rotating insert trial, may be accomplished with a rotating insert trial instead of or in addition to the non-rotating insert trial. This is accomplished by using the evaluation bullet  80  (a “pinned” evaluation bullet) rather than the evaluation bullet  60 . In this regard, reference is now made to FIG.  16 . In  FIG. 16 , the evaluation bullet  60  is shown being inserted into the cutout portion  32  of the tray body  25  of the trial tray  12 . The evaluation bullet  80  is tapped down to push the spikes  85  and  87  into the proximal tibia. 
   Once the evaluation bullet  80  is in place, a tibial insert trial  110  is chosen that matches the chosen femoral size and style, curved or stabilized, as decided by the surgeon for the particular case and anatomy. Referring to  FIGS. 17 and 18 , the insert trial  110  includes a recess  112  that is received onto the trunnion  88  of the evaluation bullet  80 . As well, the handle  16  is removed. With the trial insert  110  in place, the knee is extended noting the anteroposterior stability, medial/lateral stability and overall alignment in the A/P and M/L plane. Assessment of the bearing rotation and patellofemoral tracking can also be achieved, since the insert trial  110  is rotatable on the trunnion  88 /evaluation bearing  80 . Overall alignment can be confirmed using a two part alignment rod (not shown) attaching it to the handle  16  that would be reattached to the trial tray  25 . If there is any indication of instability, a next greater thickness insert trial is selected and trial reduction is repeated. An insert trial should be selected which gives the greatest stability in flexion and extension while still allowing full extension. Once the correct insert trial is obtained, tray rotation and position is noted and marked with electrocautery. 
   Referring to  FIGS. 19 and 20 , thereafter, the handle  16  is reattached to the tray  25  and the evaluation bullet is removed (for both evaluation bullets  60  and  80 ). The trial tray  12  is then secured to the tibia  50  by two fixation pins  120  and  122  respectively extending through recessed bores  40  and  42 . The handle  16  is then removed and a drill guide  130  is retained thereon. Various options regarding the final implant vary from cemented to non-cemented applications, as well as with or without keel preparation. After drilling or the like, the trial tray  25  is removed and the final implant is installed. 
   Please note that the trunnion  88  of the evaluation bullet  80  is configured to cooperate with the structure of the insert trial  110  that defines the recess  112  so as to enable rotation of the insert trial  110  about a fixed axis relative to the evaluation bullet. However, it should be appreciated that the trunnion  88  of the evaluation bullet  80  and the structure of the insert trial  110  that defines the recess  112  may be alternatively configured. With such configuration, the alternatively configured trunnion would be configured to cooperate with the alternatively configured structure of the insert trial that defines the recess so as to enable some anterior-posterior movement (and/or medial-lateral movement) along with some rotational movement of the insert trial relative to the evaluation bullet. 
   Operation of the Present Invention 
   In operation, the trial tray assembly  10  of the present invention is utilized to evaluate and check the kinematics of a patient&#39;s tibia  50  for implantation of a tibial component during performance of a knee replacement procedure. In order to do so, the proximal end portion of the patient&#39;s tibia  50  is first resected by use of, for example, a bone saw (not shown). Thereafter, with the knee in maximal flexion, the patient&#39;s tibia  50  is subluxed anteriorly with a tibia retractor (not shown). An appropriately sized trial tray  12 , having a handle assembly  14  is placed onto the resected tibia  50 , as particularly shown in  FIGS. 2 ,  13 , and  16 . In particular, a group of trial trays  12  may be provided which includes trial trays configured in a number of different sizes. Hence, a trial tray  12  which provides the greatest coverage of the resected surface of the tibia  50  without overhanging anteriorly of the midcoronal plane of the tibia  50  is selected from such a group. 
   An appropriate evaluation bullet  60  or  80  is selected and placed into the cutout portion  32  of the tray body  25 . If a non-rotating insert trial is desired, the evaluation bullet  60  is chosen. If a rotating insert trial is desired, the evaluation bullet  80  is chosen. An appropriate insert trial is then placed onto the trunnion of the evaluation bullet. Once the bullet and insert trial are in place, the knee is extended in order to allow the surgeon to assess the medial and lateral stability of the knee along with the overall alignment of the knee in both the anterior/posterior and medial/lateral planes. If the surgeon encounters any potential instability, a different insert trial  100  or  110  may be substituted in order increase stability in flexion and extension along with allowing for full extension. 
   Moreover, during such a “mock up”, the surgeon may adjust the rotational alignment of the trial tray  12  while the knee is positioned in full extension. The handle assembly  16  is utilized to rotate the trial tray  12  and the bearing insert  110  relative to the femoral component  140 . Once each of the components associated with the prostheses is positioned in a desired location, the location of the trial tray  12  is marked so as to be recreated at a later time. In particular, as shown in  FIG. 15 , electrocautery is utilized to create a number of alignment marks  96  on the anterior tibial cortex of the patient&#39;s tibia  50 . Such marks  96  correspond with features on the trial tray  12  and/or the handle assembly  16  thereby allowing the current orientation of the trial tray  12  to be reproduced by subsequent realignment of the trial tray  12  relative to the marks  96 . Once the alignment marks  96  have been formed in the tibia  50 , the trial prostheses may be disassembled or otherwise removed from the knee. 
   Thereafter, with the knee in substantially full flexion and the tibia subluxed anteriorly, the trial tray  12  is positioned in a desired rotational position by use of the alignment marks  96 . Once aligned, the evaluation bullet is removed and the trial tray  12  is secured to the resected surface of the tibia  50  by use of the fixation pins  120 ,  122  which are inserted through the openings  40 ,  42  defined in the plate  25  of the trial tray  12 . It should be appreciated that a pair of holes (not shown) may be drilled in the tibia  50  to receive the fixation pins  120 ,  122  prior to insertion thereof. 
   The handle assembly  16  which was utilized to align the trial tray  12  is then removed so that the handle assembly  16  associated with the drill guide  130  may be secured to the trial tray  12 . Once the drill guide  130  has been secured to the trial tray  12 , a bone drill (not shown) is advanced through an elongated bore of the drill guide  130  in order to drill a drilled hole in the patient&#39;s tibia  50 . The bone drill (not shown) may be equipped with a depth stop which engages the body of the drill guide  130  once the bone drill has drilled to a desired depth in the patient&#39;s tibia  50 . It should be appreciated that the drilled hole is provided to receive a sub-stem member of a final tibial component. As such, it should further be appreciated that the drilled hole is centered or otherwise aligned with the both the center of the plate  25  of the trial tray  12  (i.e. the center point of the plate opening  32 ) and the center of the tibia  50 . 
   The trial tray  25  is used as a drill/broach guide and an appropriate bore is made in the tibia  50  for the final implant. Once broached or punched in such a manner, the trial assembly may be disassembled. The fixation pins  120 ,  122  may then be removed so as to allow the trial tray  12  to be detached from the tibia  50 . The resultant features formed in the proximal end of the patient&#39;s tibia  50  are configured to receive a final tibial implant  100 . 
   While the invention 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 the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. For example, while the evaluation bullet is disclosed as being adapted to removably fit into a configured recess in the trial tray, it is possible that the evaluation bullet can be made integral with the trial tray. 
   There is a plurality of advantages of the present invention arising from the various features of the present invention and associated method described herein. It will be noted that alternative embodiments of the surgical instrument assembly and associated method of the present invention 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 a surgical instrument assembly and associated method that incorporate one or more of the features of the present invention and fall within the spirit and scope of the present invention as defined by the appended claims.