Abstract:
A tibial component for use with a resected tibia can include a medial tray portion adapted to engage a portion of the resected tibia and a lateral tray portion adapted to engage a portion of the resected tibia. A linkage can couple the medial tray portion to the lateral tray portion such that at least one of the medial tray portion and the lateral tray portion is pivotable relative to the other of the medial tray portion and the lateral tray portion to position the medial tray portion and the lateral tray portion at separate angles with respect to each other.

Description:
FIELD 
     The present disclosure relates to a knee joint prosthesis including a tibial tray component having independent and selectively attachable bearings, the tibial tray including a medial tray portion and a lateral tray portion that are independently pivotal around axes that extend generally in a medial/lateral direction. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     A knee joint prosthesis can generally comprise a femoral component and a tibial component. The femoral component and the tibial component can be designed to be surgically attached to the distal end of the femur and the proximal end of the tibia, respectively. The femoral component can further be designed to cooperate with the tibial component in simulating the articulating motion of an anatomical knee joint. In many examples, the tibial component can further include a bearing component that includes articulation surfaces on the medial and lateral side for cooperating with a medial and lateral condyle portion of the femoral component. In some examples, the bearing component can be fixed relative to the tibial component. In other examples, the bearing component can be a mobile bearing component that has at least a portion that can move relative to the tibial component during articulation of the femoral component. In some applications, it may be desirable to retain or reconstruct an anterior cruciate ligament (ACL) and/or a posterior cruciate ligament (PCL). 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     A tibial component for use with a resected tibia can include a medial tray portion adapted to engage a portion of the resected tibia and a lateral tray portion adapted to engage a portion of the resected tibia. A linkage can couple the medial tray portion to the lateral tray portion such that at least one of the medial tray portion and the lateral tray portion is pivotable relative to the other of the medial tray portion and the lateral tray portion to position the medial tray portion and the lateral tray portion at separate angles with respect to each other. 
     According to additional features, the linkage can comprise a pivot axle that extends into one of the medial tray portion and the lateral tray portion. One of the medial tray portion and lateral tray portion is selectively rotatable around an axis defined by the pivot axle. The linkage can move between a locked position and an unlocked position. In the locked position, one of the medial tray portion and lateral tray portion is fixed relative to the other of the medial tray portion and lateral tray portion. In the unlocked position, one of the medial tray portion and lateral tray portion is rotatable relative to the other of the medial tray portion and lateral tray portion. In one example, the pivot axle comprises a threaded fastener. 
     According to still other features, a connection portion can be disposed between the medial and lateral tray portions. The connection portion, medial tray portion and lateral tray portion can collectively form a U-shaped body. The linkage can further comprise a first linkage and a second linkage. The first linkage can rotatably couple the medial tray portion to the connection portion. The second linkage can rotatably couple the lateral tray portion to the connection portion. 
     According to still other features, the pivot axle can further comprise a first pivot axle and a second pivot axle. The medial tray portion can define a medial bore that receives a first portion of the first pivot axle and the connection portion defines a medial receiving bore that receives a second portion of the first pivot axle. The lateral tray portion can define a lateral bore that receives a first portion of the second pivot axle and the connection portion can define a lateral receiving bore that receives a second portion of the second pivot axle. The first pivot axle can include a first threaded fastener that threadably engages the medial receiving bore. The second pivot axle can include a second threaded fastener that threadably engages the lateral receiving bore. 
     According to other examples, a medial bearing can be selectively engaged to the medial tray portion. A lateral bearing can be selectively engaged to the lateral tray portion. A femoral component can be adapted to engage a portion of a resected femur and be rotatably engaged with the medial and lateral bearings. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is an anterior perspective view of a knee prosthesis assembly that incorporates a pivoting tibial tray according to one example of the present teachings; 
         FIG. 2  is an anterior perspective view of the pivoting tibial tray of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the knee prosthesis assembly of  FIG. 1 ; 
         FIG. 4  is a lateral view of the pivoting tibial tray of  FIG. 2 ; 
         FIG. 5  is a lateral view of the pivoting tibial tray of  FIG. 4  and shown with the lateral tray portion pivoted around a pivot axis that extends generally along a medial/lateral direction in an implanted position; and 
         FIG. 6  is a lateral view of the pivoting tibial tray shown with a lateral bearing and a medial bearing connected to respective lateral and medial tray portions and shown with the lateral tray portion rotated generally posteriorly in an implanted position about the pivot axis. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     With initial reference to  FIGS. 1 and 2 , a knee prosthesis assembly constructed in accordance to one example of the present teachings is shown and generally identified at reference numeral  10 . The knee prosthesis assembly  10  shown in the drawings is specific for a left knee. It will be understood, however, that a suitable right knee prosthesis can be similarly constructed. The knee prosthesis assembly  10  can generally include a femoral component  12 , a tibial tray  14 , a medial bearing  16 , and a lateral bearing  18 . As will be described, the knee prosthesis assembly  10  can be used when it is desirable to retain or reconstruct an ACL and/or a PCL. 
     The respective components of the knee prosthesis assembly  10  can be patient specific, such that each component can be constructed for optimal features of a given patient. For example, the bone interface margins of the femoral component  12  and tibial tray  14  can be patient specific for optimized bone coverage. In addition, the overall size, such as anterior-posterior dimensions and bone cut geometry can be determined and used for manufacturing the components of the knee prosthesis assembly  10 . Moreover, some articulation features can be determined and used as criteria for forming the components of the knee prosthesis assembly  10 . In sum, each of the components of the knee prosthesis assembly  10  can be patient-specific implant, a semi-custom implant, or an off-the-shelf or standard production implant. 
     A custom-made implant is a patient-specific, one-of-a-kind implant specifically made for a particular patient, and consequently, there is no inventory associated with such an implant. Standard or off-the-shelf implants are available and stocked in a number of sizes, typically six or more, and a number of configurations or types, including bilateral or unilateral implants, constrained, semi-constrained, mobile, etc. Because of the variety of sizes and configurations that are kept in stock to be accommodated by different patients, a large inventory of standard implants is created, and several molds for each type and size of implant may be used. Semi-custom implants can provide an intermediate solution between custom-made and off-the-shelf implants. Semi-custom implants reduce the size of inventory and molds required for production, while allowing some degree of patient-specific customization. Additional description of patient-specific implants and semi-custom implants and their implementations may be found in co-pending patent application Ser. No. 12/103,824, filed Apr. 16, 2008 and entitled: Method and Apparatus for Manufacturing an Implant, the disclosure of which is hereby incorporated by reference. 
     With specific reference now to  FIG. 1 , the femoral component  12  will now be described in greater detail. The femoral component  12  can generally comprise a cruciate retaining prosthesis and includes various portions to replace or mimic the distal femur. The femoral component  12  can include a medial condyle portion  20  and a lateral condyle portion  22 . The condyle portions  20  and  22  can replace the medial and lateral condyles of a distal femur F. The medial and lateral condyle portions  20  and  22  can interconnect and be formed as a single piece with a patellar track portion  26 . The patellar track portion  26  can allow for articulation of a patella, either natural or prosthetic patella, once the femoral component  12  is implanted onto the distal femur. The medial and lateral condyle portions  20  and  22  and the patellar track portion  26  can generally define an exterior portion of the femoral component  12 . The femoral component  12  can define an opening or passage  30  between the medial and lateral condyle portions  20  and  22 . As can be appreciated, the passage  30  can accommodate, and provide clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. 
     The femoral component  12  can include a bone contacting or inferior surface  34  adapted to engage the distal femur F. The inferior surface  34  can include an anterior surface  36  that can be substantially flat and formed generally parallel to a pair of posterior surfaces  38   a  and  38   b . A pair of intermediate surfaces  40   a  and  40   b  are provided generally at an intermediate portion of the inferior surface  34 . A pair of angled anterior transition surfaces  42   a  and  42   b  generally connect the anterior surface  36  with the intermediate surfaces  40   a  and  40   b , respectively. Similarly, a pair of angled posterior transition surfaces  44   a  and  44   b  are provided between the respective posterior surfaces  38   a  and  38   b  and the intermediate surfaces  40   a  and  40   b . While not specifically shown, threaded bosses can be provided on each of the intermediate surfaces  40   a  and  40   b , respectively. Similarly, threaded bosses can be provided on the posterior surfaces  38   a  and  38   b , respectively. The bosses can be optionally used to threadably couple with various augments (not specifically shown) as necessary. 
     The femoral component  12  can be formed as a unitary structure and cast of a biocompatible high strength alloy, such as cobalt-chromium-molybdenum alloy or similar suitable material. All surfaces, which do not contact the femur F, can be highly polished to provide smooth articulating bearing surfaces. The interior surface  34  of the femoral component  12  can be roughened or uneven or include porous material to allow bone ingrowth or attachment with bone cement. Other features of the femoral component  12  can include those associated with the Oxford® Partial Knee marketed by Biomet, Inc. 
     With reference now to  FIGS. 1-3 , the tibial tray  14  will now be described in greater detail. The tibial tray  14  can include a generally U-shaped body  58  having a first or medial tray portion  60 , a second or lateral tray portion  62 , and a connection portion  64 . A slot  66  can be formed in the tibial tray  14  generally between the medial and lateral tray portions  60  and  62 . As with the passage  30  of the femoral component, the slot  66  of the tibial tray  14  can accommodate and provide a clearance for a host ACL and/or PCL or a reconstructed ACL and/or PCL. During implantation, the tibial tray  14  can be advanced posteriorly, such that the slot  66  can accommodate a host ACL and/or PCL. In instances where a reconstructed ACL and/or PCL is used, a tray (and bearing) having a passage can be utilized. One suitable configuration is further described in commonly owned U.S. Pat. No. 7,255,715; issued Aug. 14, 2007 and is hereby incorporated by reference. 
     The tibial tray  14  can include an inferior bone engaging side  68  and a superior bearing engaging side  70 . A pair of fins  71  can extend from the inferior bone engaging side  68 . While the fins  71  are shown operatively associated with the tibial tray  14 , other structures suitable for engaging a proximal tibia T can include pegs, posts, or porous material and can additionally or alternatively be provided on the inferior bone engaging side  68 . The medial tray portion  60  of the superior bearing engaging side  70  can include a medial tibial bearing engaging surface  72 . The medial tibial bearing engaging surface  72  can extend generally along a plane  73 . The lateral tray portion  62  of the superior engaging side  70  can include a lateral tibial bearing engaging surface  74 . The lateral tibial bearing engaging surface  74  can extend generally along a plane  75 . The connection portion  64  can have an upper surface  76  that extends along a plane  78 . 
     The tibial tray  14  can generally include a locating tab  80  formed on an anterior edge of the medial tray portion  60  and a locating tab  82  formed on an anterior edge of the lateral tray portion  62 . A retaining rail  86  can be formed around a posterior edge of the medial tray portion  60 . The retaining rail  86  can include a lip  90  and a groove  92 . A retaining rail  100  can be formed around a posterior edge of the lateral tray portion  62  of the tibial tray  14 . The retaining rail  100  can generally include a lip  102  and a groove  104 . 
     With particular reference now to  FIGS. 2 and 3 , additional features of the tibial tray  14  will now be described. The tibial tray  14  can include a first linkage  120  and a second linkage  122 . As will be described further herein, the first linkage  120  and the second linkage  122  can allow a surgeon to selectively and independently pivot the medial tray portion  60  and lateral tray portion  62  relative to each other. In some examples, the medial tray portion  60  or lateral tray portion  62  can be pivoted relative to the connection portion  64 . In this regard, the connection portion  64  can be aligned in various positions relative to either the medial tray portion  60  or the lateral tray portion  62 . Explained further, the plane  78  of the connection portion  64  can be positioned coplanar with either, both, or neither of the planes  73  and  75 . In other configurations, the connection portion  64  can be integrally formed with one of the medial or lateral tray portions  60 ,  62  when it is desirable to provide a tibial tray with only one linkage. 
     The medial tray portion  60  can rotate around a first or medial pivot axis  126  defined by a first or medial pivot axle  128  ( FIG. 3 ). Similarly, the lateral tray portion  62  can pivot around a second or lateral pivot axis  130  defined by a second or lateral pivot axle  132 . The first linkage  120  further includes a medial bore  134 , a head engaging surface  136 , and a medial recess  138  provided on the medial tray portion  60 . The first linkage  120  further comprises a medial boss  140  and a medial receiving bore  142  provided on the connection portion  64 . In an assembled position ( FIG. 1 ), the medial boss  140  is received by the medial recess  138  to provide additional structural support to the first linkage  120 . It is appreciated that alternate configurations may be provided. For example, the medial recess  138  may be formed on the connection portion  64  and the medial boss  140  may be formed on the medial tray portion  60 . 
     The second linkage  122  can further comprise a lateral bore  154 , a head engaging surface  156 , and a lateral recess  158  provided on the lateral tray portion  62 . The second linkage  122  can further include a lateral boss  160  and a lateral receiving bore  162  provided on the connection portion  64 . In an assembled position ( FIG. 1 ), the lateral boss  160  is received by the lateral recess  158  to provide structural support to the second linkage  122 . It is appreciated that alternate configurations may be provided. For example, the lateral recess  158  may be formed on the connection portion  64  and the lateral boss  160  may be formed on the lateral tray portion  62 . 
     The medial pivot axle  128  is in the form of a first or medial fastener  170  that includes a head  172  and a shaft  174 . The head  172  defines a tool engaging portion  176 . The shaft  174  can define threads  178 . Similarly, the lateral pivot axle  132  can generally comprise a second or lateral fastener  180  having a head  182  and a shaft  184 . The head  182  can define a tool engaging portion  186 . The shaft  184  can include threads  188 . As can be appreciated, the medial pivot axis  126  can be provided along the medial fastener  170 . Similarly, the lateral pivot axis  130  can be provided along the lateral fastener  180 . It will also be appreciated that while the medial pivot axis  126  and the lateral pivot axis  130  are represented in the drawings as coaxial relative to each other, they may alternatively be parallel and offset relative to each other, intersecting or non-parallel and non-intersecting. 
     With specific reference now to  FIG. 3 , the medial and lateral bearings  16  and  18  will be described. The medial bearing  16  can generally include a superior surface  202  that substantially conforms to and provides a surface contact with the profile of the medial condyle portion  20  of the femoral component  12 . A channel  204  can be formed along an anterior inferior surface  206  and that generally tapers anteriorly. A groove  210  can be formed around a posterior edge of the bearing  16 . The bearing  16  can have an inner wall  212  that cooperates with the U-shaped profile of the tibial tray  14  to accommodate a host or reconstructed ACL. 
     The lateral bearing  18  can generally include a superior surface  222  that substantially conforms to and provides a surface contact with the profile of the lateral condyle portion  22  of the femoral component  12 . A channel  224  can be formed along an anterior inferior surface  226  and that generally tapers anteriorly. A groove  230  can be formed around a posterior edge of the lateral bearing  18 . The lateral bearing  18  can have an inner wall  332  that cooperates with the U-shaped profile of the tibial tray  14  to accommodate a host or reconstructed ACL. 
     Connection of the medial bearing  16  to the medial tray portion  60  of the tibial tray  14  will now be discussed. Initially, the inferior surface  206  of the medial bearing  16  is located onto the medial tray portion  60  of the tibial tray  14 . Next, the medial bearing  16  is slidably advanced posteriorly, such that the channel  204  slidably accommodates the locating tab  80  while the groove  210  locates under the lip  90 . The medial bearing  16  is adapted to be statically secured relative to the medial tray portion  60  of the tibial tray  14  when assembled. 
     Connection of the lateral bearing  18  to the lateral tray portion  62  of the tibial tray  14  is similarly carried out. The medial bearing  16  and the lateral bearing  18  are both independently formed and interoperatively selected according to the needs of a given patient. It is appreciated that other configurations and connection techniques may be provided for the medial and lateral bearings  16  and  18 . Furthermore, while the medial bearing  16  and the lateral bearing  18  are generally fixed bearing components, a mobile bearing component may be similarly provided for either of the medial and/or lateral sides. Further discussion of such mobile bearing components may be found in commonly owned and co-pending patent application Ser. No. 12/788,961; filed May 27, 2010, entitled Knee Prosthesis; the disclosure of which is incorporated herein by reference. 
     An exemplary method of rotating the lateral tray portion  62  of the tibial tray  14  relative to a remainder of the tibial tray  14  (i.e., the medial tray portion  60  and the connection portion  64 ) will now be described. At the outset, the lateral fastener  180  may be located into the lateral bore  154  such that the head  182  engages the head engaging surface  156  while the threads  188  are threadably received by the lateral receiving bore  162 . A surgeon can advance a tool into the lateral bore  154  to engage the tool engaging portion  186  of the lateral fastener  180 . The surgeon can then loosen the lateral fastener  180  such that the lateral tray portion  62  is free to rotate about the lateral pivot axis  130  in a first rotational direction (counter-clockwise as viewed in  FIG. 5 ). Next, a surgeon can rotate the lateral tray portion  62  about the lateral pivot axis  130  such that the lateral tray portion  62  moves toward a generally anterior sloped position  62   a  (phantom line,  FIG. 5 ). Alternatively, the surgeon can rotate the lateral tray portion  62  about the lateral pivot axis  130  in a second rotational direction (clockwise as viewed in  FIG. 5 ) such that the lateral tray portion  62  moves toward a posterior sloped position  62   b  (solid line,  FIG. 5 ) according to the needs of a particular patient. Once the lateral tray portion  62  has been rotated about the lateral pivot axis  130  to the desired position, the surgeon can then tighten the lateral fastener  180  into the lateral receiving bore  162  until the lateral tray portion  62  is statically fixed relative to the connection portion  64 . It will be appreciated that the medial tray portion  60  may be rotated around the medial pivot axis  126  in a similar manner to independently position the medial tray portion  60  at a desired slope, if necessary. It is also appreciated that other mechanical configurations may be provided for the medial and second linkages  120 ,  122 . 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.