Abstract:
A prosthetic tibial component for a knee joint, said prosthetic tibial component comprising:
       a base construct for engaging the tibia; and   a bearing construct for engaging the femoral side of the knee joint;   said bearing construct being adjustably fixedly mountable to said base construct.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
     This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 61/638,956, filed Apr. 26, 2012 by Brian James Katerberg et al. for MODULAR TRAY, which patent application is hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to orthopedic prostheses in general, and more particularly to prosthetic tibial components for knee joint prostheses. 
     BACKGROUND OF THE INVENTION 
     Joint replacement surgery seeks to replace some or all of a natural joint with prosthetic components so as to provide long-lasting function and pain-free mobility. 
     For example, in the case of a prosthetic total hip joint, the head of the femur is replaced with a prosthetic femoral stem component, and the socket of the acetabulum is replaced by a prosthetic acetabular cup component, whereby to provide a prosthetic total hip joint. 
     In the case of a prosthetic total knee joint, the top of the tibia is replaced by a prosthetic tibial component, and the bottom of the femur is replaced by a prosthetic femoral component, whereby to provide a prosthetic total knee joint. 
     The present invention is directed to orthopedic prostheses for restoring the knee joint and, in particular, to improved prosthetic tibial components. 
     Looking now at  FIG. 1 , there is shown a prior art prosthetic total knee joint  5  which generally comprises a prosthetic tibial component  10  secured to the top end of a resected tibia  15 , and a prosthetic femoral component  20  which is secured to the bottom end of a resected femur  25 . 
     A typical prior art prosthetic tibial component  10  is shown in greater detail in  FIGS. 2 and 3 . Prior art prosthetic tibial component  10  generally comprises a metal base construct  30  and a polyethylene bearing construct  35 . 
     More particularly, metal base construct  30  generally comprises a baseplate  40  having a top surface  42  and a bottom surface  43 , a stem  45  and a plurality of posts  50  descending from bottom surface  43  of baseplate  40  and into resected tibia  15 , and a plurality of screws  55  passing through baseplate  40  and into resected tibia  15 . Baseplate  40  preferably has a peripheral profile which generally matches the peripheral profile of the resected tibia  15 . Metal base construct  30  also comprises a pair of locking rails  60  fixed to the top surface  42  of baseplate  40  and defining a groove  65  therebetween, and a pair of end walls  70  connected to top surface  42  of baseplate  40 . Preferably bottom surface  43  of baseplate  40  (and, optionally, stem  45  and/or posts  50 ) comprises a porous material so as to allow bone ingrowth into baseplate  40  (and/or stem  45  and/or posts  50 ), whereby to facilitate osseo-integration of baseplate  40  (and/or stem  45  and/or posts  50 ) with resected tibia  15  over time. Additionally and/or alternatively, baseplate  40  and/or stem  45  and/or posts  50  may be fixed to resected tibia  15  with bone cement. 
     Polyethylene bearing construct  35  comprises a sculpted upper surface  71  having a central ridge  72  which separates a pair of scalloped seats  73  for receiving the condyles (either natural or prosthetic) of the lower femur. Polyethylene bearing construct  35  also comprises a flat bottom surface  75  having a recess  80  in which is disposed a tongue  85 . Tongue  85  is sized to slidingly fit in the groove  65  which is defined by locking rails  60  of metal base construct  30  ( FIG. 3 ), whereby polyethylene bearing construct  35  may be slidingly secured to locking rails  60  of metal base construct  30 . Note that end walls  70  of locking metal base construct  30  act as stops for polyethylene bearing construct  35  when tongue  85  of polyethylene bearing construct  35  is advanced into the groove  65  which is defined by locking rails  60  of metal base construct  30 . 
     In use, the top end of tibia  15  is resected, and metal base construct  30  is secured to tibia  15 , i.e., by advancing stem  45  and posts  50  into resected tibia  15  until bottom surface  43  of baseplate  40  is seated against resected tibia  15 . Note that the parallel dispositions of stem  45  and posts  50  facilitates advancement of stem  45  and posts  50  into the resected tibia. Next, screws  55  are advanced through baseplate  40  and into resected tibia  15 , whereby to secure metal base construct  30  to resected tibia  15 . Then polyethylene bearing construct  35  is locked onto metal base construct  30 , e.g., by sliding tongue  85  of polyethylene bearing construct  35  into the groove  65  which is defined by locking rails  60  of metal base construct  30  until polyethylene bearing construct  35  engages end walls  70  of baseplate  40 . Thereafter, the knee joint is reduced, allowing the condyles (either natural or prosthetic) of the lower femur to settle into the scalloped seats  73  of polyethylene bearing construct  35 . 
     Unfortunately, in some patients, the natural geometry of the knee is such that there may be some degree of misalignment between the condyles (either natural or prosthetic) of the lower femur and the scalloped seats  73  of polyethylene bearing construct  35  of the prosthetic tibial component  10 . Specifically, the anterior-posterior centerline of the condyles (either natural or prosthetic) of the lower femur, and the anterior-posterior centerline of the scalloped seats  73  of polyethylene bearing construct  35  of the prosthetic tibial component  10 , may be angularly offset from one another. As a result, the condyles (either natural or prosthetic) of the lower femur may not seat properly in the scalloped seats  73  of polyethylene bearing construct  35  of the prosthetic tibial component  10 . This may occur at some or all of the extent of flexure of the knee. This mis-seating of the condyles (either natural or prosthetic) of the lower femur in the scalloped seats  73  of polyethylene bearing construct  35  of the prosthetic tibial component  10  can lead to reduced stability of the knee in both static and dynamic conditions, and can lead to excessive wear of the polyethylene bearing construct  35  over time. In addition, this mis-seating of the condyles (either natural or prosthetic) of the lower femur in the scalloped seats  73  of polyethylene bearing construct  35  of the prosthetic tibial component  10  can lead to early loosening of the prosthetic tibial component, or to early loosening of the prosthetic femoral component, or both, and/or it can result in poor bone coverage leading to bone subsidence. 
     Thus there is a need for a new and improved prosthetic tibial component for a knee joint prosthesis which can provide for better alignment between the condyles (either natural or prosthetic) of the lower femur and the scalloped seats of the polyethylene bearing construct of the prosthetic tibial component. 
     SUMMARY OF THE INVENTION 
     The present invention comprises the provision and use of a new and improved prosthetic tibial component for a knee joint prosthesis which provides for better alignment between the condyles (either natural or prosthetic) of the lower femur and the scalloped seats of the polyethylene bearing construct of the prosthetic tibial component. 
     More particularly, the present invention comprises the provision and use of a new and improved prosthetic tibial component for a knee joint prosthesis which provides for better alignment of the anterior-posterior centerline of the condyles (either natural or prosthetic) of the lower femur and the anterior-posterior centerline of the scalloped seats of the polyethylene bearing construct of the prosthetic tibial component. 
     In one preferred form of the invention, there is provided a prosthetic tibial component for a knee joint, said prosthetic tibial component comprising: 
     a base construct for engaging the tibia; and 
     a bearing construct for engaging the femoral side of the knee joint; 
     said bearing construct being adjustably fixedly mountable to said base construct. 
     In another preferred form of the invention, there is provided a method for reconstructing a knee joint, said method comprising: 
     providing a prosthetic tibial component for a knee joint, said prosthetic tibial component comprising a base construct for engaging the tibia, and a bearing construct for engaging the femoral side of the knee joint, said bearing construct comprising a pair of concave seats for receiving the condyles of the femoral side of the knee joint, and said bearing construct being adjustably fixedly mountable to said base construct; 
     resecting the tibia; and 
     mounting said base construct to said resected tibia and adjustably fixedly mounting said bearing construct to said base construct so that said pair of concave seats in said bearing construct are appropriately aligned with the condyles of the femoral side of the knee joint. 
     In another preferred form of the invention, there is provided a prosthetic tibial component for a knee joint, said prosthetic tibial component comprising: 
     a base construct comprising a baseplate for attachment to the tibia and a mount for receiving a bearing construct for engaging the femoral side of the knee joint, said mount being adjustably fixedly mountable to said baseplate. 
     In another preferred form of the invention, there is provided a prosthetic component for a joint, said prosthetic component comprising: 
     a base construct for engaging a first bone of the joint; and 
     a bearing construct for engaging a second bone of the joint; 
     said bearing construct being adjustably fixedly mountable to said base construct. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
         FIG. 1  is a schematic side view showing a prior art prosthetic total knee joint; 
         FIG. 2  is a schematic partially-exploded perspective view showing a prior art prosthetic tibial component; 
         FIG. 3  is a schematic front view showing a prior art prosthetic tibial component secured to a resected tibia; 
         FIG. 4  is a schematic view showing a reconstructed knee joint, wherein the tibial side of the reconstructed knee joint comprises a novel prosthetic tibial component which is secured to the top end of a resected tibia, and the femoral side of the reconstructed knee joint comprises a prosthetic femoral component which is secured to the bottom end of a resected femur; 
         FIG. 5  is a schematic view showing the tibial side of the reconstructed knee joint shown in  FIG. 4 ; 
         FIGS. 6 and 7  are schematic views showing the femoral side of the reconstructed knee joint shown in  FIG. 4 ; 
         FIGS. 8 and 9  are schematic views showing the novel prosthetic tibial component shown in  FIG. 4 ; 
         FIG. 10  is a schematic exploded view showing the modular metal base construct of the novel prosthetic tibial component shown in  FIGS. 8 and 9 ; 
         FIG. 11  is a schematic view showing the polyethylene bearing construct of the novel prosthetic tibial component shown in  FIGS. 8 and 9 ; 
         FIGS. 12A, 12B and 12C  show the locking rail element of the modular metal base construct of  FIG. 10  in a range of angular positions (i.e.,  FIG. 12A  shows the locking rail element externally rotated,  FIG. 12B  shows the locking rail element in a “neutral” position, and  FIG. 12C  shows the locking rail element internally rotated); 
         FIGS. 13A, 13B and 13C  are views similar to those of  FIGS. 12A, 12B and 12C , respectively, but with the polyethylene bearing construct shown mounted to the modular metal base construct (i.e.,  FIG. 13A  shows the polyethylene bearing construct externally rotated,  FIG. 13B  shows the polyethylene bearing construct in a “neutral” position, and  FIG. 13C  shows the polyethylene bearing construct internally rotated); and 
         FIG. 14  is a schematic view showing one preferred construction for securing the locking rail element to the remainder of the modular metal base construct. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The Novel Prosthetic Tibial Component 
     The present invention comprises the provision and use of a new and improved prosthetic tibial component for a knee joint prosthesis which provides for better alignment between the condyles (either natural or prosthetic) of the lower femur and the scalloped seats of the polyethylene bearing construct of the prosthetic tibial component. 
     More particularly, the present invention comprises the provision and use of a new and improved prosthetic tibial component for a knee joint prosthesis which provides for better alignment of the anterior-posterior centerline of the condyles (either natural or prosthetic) of the lower femur and the anterior-posterior centerline of the scalloped seats of the polyethylene bearing construct of the prosthetic tibial component. 
     Looking now at  FIG. 4 , there is shown a novel prosthetic total knee joint  105  which generally comprises a novel prosthetic tibial component  110  secured to the top end of a resected tibia  115 , and a prosthetic femoral component  120  which is secured to the bottom end of a resected femur  125 . 
     As will hereinafter be discussed in further detail, and looking now at  FIG. 5 , novel prosthetic tibial component  110  generally comprises a modular metal base construct  130  and a polyethylene bearing construct  135 . As will also hereinafter be discussed in further detail, novel prosthetic tibial component  110  is characterized by two scalloped seats  173  which define an anterior-posterior centerline  136  of the polyethylene bearing construct  135 . 
     Prosthetic femoral component  120  is shown in greater detail in  FIGS. 6 and 7 , and is characterized by two condyles  137  which define an anterior-posterior centerline  138 . 
     As will hereinafter be discussed, novel prosthetic tibial component  110  is configured so as to allow the anterior-posterior centerline  136  of the scalloped seats of polyethylene bearing construct  135  to be better aligned with the anterior-posterior centerline  138  of the two condyles  137  of the lower femur, whereby to provide for better alignment between the condyles of the lower femur and the scalloped seats of the polyethylene bearing construct. 
     More particularly, and looking now at  FIGS. 8-10 , modular metal base construct  130  generally comprises a baseplate  140  and a locking rail component  141 . 
     Baseplate  140  has a top surface  142  for receiving polyethylene bearing construct  135 , an opposing bottom surface  143  for engaging resected tibia  115 , a stem  145  descending from the bottom surface of baseplate  140  for extending into resected tibia  115 , a bore  146  extending through baseplate  140  and into stem  145 , and a plurality of screw holes  156  extending through baseplate  140  for receiving screws (not shown) for securing baseplate  140  to resected tibia  115 . Baseplate  140  preferably has a peripheral profile which generally matches the peripheral profile of the resected tibia  115 . 
     Locking rail component  141  comprises a body  157  having a pair of locking rails  160  running along its top surface  161  and defining a groove  165  therebetween. Groove  165  extends along a longitudinal axis  166 . Body  157  of locking rail component  141  also has an end wall  170  connected to top surface  161  of body  157  and connecting locking rails  160  to one another. A post  169  descends from body  157  of locking rail component  141  and is sized to be received in bore  146  of baseplate  140  and secured therein. Preferably the bottom surface  143  of baseplate  140  (and, optionally, stem  145 ) comprises a porous material so as to allow bone ingrowth into baseplate  140  (and/or stem  145 ), whereby to facilitate osseo-integration of the baseplate  140  (and/or stem  145 ) with resected tibia  115  over time. Additionally and/or alternatively, baseplate  140  and/or stem  145  may be fixed to resected tibia  115  with bone cement. 
     Looking now at  FIGS. 8, 9 and 11 , polyethylene bearing construct  135  comprises a sculpted upper surface  171  having a central ridge  172  which separates a pair of scalloped seats  173  for receiving the condyles (either natural or prosthetic) of the lower femur. Polyethylene bearing construct  135  also comprises a flat bottom surface  175  having a recess  180  in which is disposed a tongue  185  which extends along a longitudinal axis  186 . Note that longitudinal axis  186  of tongue  185  extends parallel to the anterior-posterior centerline  136  of scalloped seats  173  of the polyethylene bearing construct  135 . Tongue  185  is sized to slidingly fit in groove  165  of locking rails  160  of locking rail component  141  ( FIG. 11 ), whereby polyethylene bearing construct  135  may be slidingly secured to locking rail component  141  of modular metal base construct  130 . Note that end wall  170  of locking rail component  141  acts as a stop for polyethylene bearing construct  135  when tongue  185  of polyethylene bearing construct  135  is advanced into groove  165  of locking rail component  141  of modular metal base construct  130 . Note also that when polyethylene bearing construct  135  is mounted to locking rail component  141 , the anterior-posterior centerline  136  of the scalloped seats  173  of the polyethylene bearing construct  135 , and the longitudinal axis  186  of the tongue  185  of polyethylene bearing construct  135 , both extend parallel to longitudinal axis  166  of groove  165  of locking rail component  141 . 
     Use of the Novel Prosthetic Tibial Component 
     In use, the top end of tibia  115  is first resected. 
     Next, baseplate  140  is secured to tibia  115 , i.e., by advancing stem  145  into resected tibia  115  until the bottom surface  143  of baseplate  140  is seated against resected tibia  115 , and by advancing screws through holes  156  of baseplate  140  and into resected tibia  115 , whereby to secure baseplate  140  to resected tibia  115 . 
     Then locking rail component  141  is mounted to baseplate  140  by advancing post  169  of locking rail component  141  into bore  146  of baseplate  140  and fixedly locking post  169  in bore  146 , whereby to fixedly secure locking rail component  141  vis-à-vis baseplate  140 . Note that prior to fixedly securing locking rail component  141  to baseplate  140 , the angular disposition of locking rail component  141  is carefully adjusted vis-à-vis baseplate  140  (and hence vis-à-vis resected tibia  115 ), such that the longitudinal axis  166  of groove  165  of locking rail component  141  is aligned with the anterior-posterior centerline  138  of the two condyles  137  of the lower femur (which will thereafter assure, when polyethylene bearing construct  135  is mounted to locking rail component  141 , that the anterior-posterior centerline  136  of the scalloped seats  173  of polyethylene bearing construct  135  are appropriately aligned with the anterior-posterior centerline  138  of the two condyles  137  of the lower femur). By way of example but not limitation, as seen in  FIGS. 12A, 12B and 12C , the longitudinal axis  166  of groove  165  of locking rail component  141  is oriented to an appropriate angular position relative to baseplate  140  so that the longitudinal axis  166  of groove  165  is appropriately aligned with the anterior-posterior centerline  138  of the two condyles  137  of the lower femur. 
     Next, polyethylene bearing construct  135  is locked onto modular metal base construct  130 , e.g., by sliding tongue  185  of polyethylene bearing construct  135  into groove  165  of locking rail component  141  of modular metal base construct  130  until polyethylene bearing construct  135  engages end wall  170  of locking rail component  141 . This action will cause the anterior-posterior centerline  136  of the scalloped seats  173  of polyethylene bearing construct  135  to be aligned with the longitudinal axis of groove  165  of locking rail component  141  (see  FIGS. 13A, 13B and 13C ), and hence appropriately aligned with the anterior-posterior centerline  138  of the two condyles  137  of the lower femur. Note that polyethylene bearing construct  135  may be offered in a range of sizes so as to minimize any “overhang” vis-à-vis baseplate  140  when polyethylene bearing construct  135  is set in an externally rotated position ( FIG. 13A ) or in an internally rotated position ( FIG. 13C ). 
     Thereafter, the joint is reduced, allowing the condyles (either natural or prosthetic) of the lower femur to settle into the scalloped seats  173  of polyethylene bearing construct  135  of prosthetic tibial component  110 . 
     If, after the joint is reduced, it is found that the kinematics of the joint are not satisfactory, the joint can be distracted again, polyethylene bearing construct  135  can be removed, locking rail component  141  can be repositioned vis-à-vis baseplate  140 , polyethylene bearing construct  135  can be remounted to locking rail component  141 , and then the joint can be reduced again. In this way, optimal positioning of the anterior-posterior centerline  136  of the scalloped seats  173  of polyethylene bearing construct  135  can be achieved vis-à-vis the anterior-posterior centerline  138  of the two condyles  137  of the lower femur. 
     Furthermore, if revision surgery should subsequently be required to adjust the positioning of the anterior-posterior centerline  136  of the scalloped seats  173  of polyethylene bearing construct  135 , this can be achieved in a similar manner. 
     Mounting the Locking Rail Component to the Baseplate 
     As discussed above, post  169  of locking rail component  141  is advanced into bore  146  of baseplate  140  and fixedly locked in position, whereby to fixedly secure locking rail component  141  to baseplate  140 . It will be appreciated that various arrangements may be provided to effect this securement. By way of example but not limitation, and looking now at  FIG. 14 , post  169  may receive an expanding collet  187  so as to cause post  169  to radially expand and thereby “grip” the side wall of bore  146  of baseplate  140 . More particularly, in this construction, a screw  188  may pass through a hole  189  formed in body  157  of locking rail component  141  so as to pull collet  187  proximally, whereby to radially expand post  169  within bore  146  and fixedly secure post  169  in bore  146 . 
     Alternatively, and by way of further example, post  169  may comprise a Morse taper for binding with the side wall of bore  146  of baseplate  140 . 
     Or, by way of still further example, post  169  may be formed with a compressible design for forming a friction grip with the side wall of bore  146 . 
     And post  169  and recess  146  of baseplate  140  may be formed with threads for fixedly securing post  169  in recess  146 . 
     In still another form of the invention, a male-female connection is used to fixedly secure locking rail component  141  to baseplate  140 , but in this alternative form of the invention, the male portion of the connection is formed on baseplate  140  and the female portion of the connection is formed on locking rail component  141 . 
     Still other approaches for securing locking rail component  141  to baseplate  140  will be apparent to those skilled in the art in view of the present disclosure. 
     Further Aspects of the Invention 
     In addition to the foregoing, it should also be appreciated that polyethylene bearing construct  135  may be mounted to locking rail component  141  before the locking rail component  141  is mounted to baseplate  140 , and/or locking rail component  141  may be mounted to baseplate  140  before baseplate  140  is mounted to resected tibia  115 . 
     Also, while in the foregoing description the novel prosthetic tibial component is discussed in the context of use with a prosthetic femoral component, it should be appreciated that the novel prosthetic tibial component may be used in conjunction with the natural condyles of a femur. 
     And it should be appreciated that the present invention is not restricted to “dual-compartment” knee joint reconstructions, i.e., it may also be applied to “uni-compartment” knee joint reconstructions where only one scalloped seat  173  and one femoral condyle is involved. 
     In addition to the foregoing, it should be appreciated that it is common in the orthopedic field to test a joint reconstruction using “trial” components prior to committing to the joint reconstruction using the actual prosthetic components. In this respect it should be appreciated that the present invention may be applied to trial components as well as to the actual prosthetic components. 
     Application to Other Joints 
     It should be appreciated that the present invention may be utilized in prostheses for joints other than the knee. By way of example but not limitation, the present invention may be utilized in an elbow joint prosthesis, an ankle joint prosthesis, a spinal prosthesis, etc. 
     Modifications 
     It should also be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the present invention, may be made by those skilled in the art while still remaining within the principles and scope of the invention.