Abstract:
An implant sterilization tray includes an integral torquing fixture for holding an implant stationary. By incorporating the fixture into the instrument tray, a large, stable base is provided for holding the implant. The user can more readily hold the implant in a stable position with the implant resting in the case and the case resting on a table.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a sterilization tray. More particularly, the invention relates to a sterilization tray having an integral torque fixture. 
     Surgical instruments are advantageously supplied as modular components that can be assembled at the time of surgery to address the needs of the particular patient. Screws are typically used to attach the components to one another and wrenches are provided to tighten the screws. For example, Zimmer, Inc. sells the NexGen® Complete Knee Solution which includes the Legacy® Knee LCCK components. The tibial component of this knee includes a base plate, an articular surface, and a locking screw to secure the articular surface to the base plate. A tibial plate wrench is supplied for holding the base plate stationary while a second wrench is used to torque the locking screw. 
     SUMMARY OF THE INVENTION 
     The present invention provides an alternative to a separate wrench for holding an implant stationary while a screw is torqued into the implant. An implant sterilization tray includes an integral torquing fixture for holding the implant stationary. By incorporating the fixture into the instrument tray, a large, stable base is provided for holding the implant. The user can more readily hold the implant in a stable position with the implant resting in the case and the case resting on a table. It is then only necessary to prevent the case from sliding while the attachment screw is torqued. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial perspective view of a torquing fixture incorporated into a sterilization tray according to the present invention. 
     FIG. 2 is a perspective view of the torquing fixture of FIG. 1 separated from the sterilization tray. 
     FIG. 3 is a partial side section view of the torquing fixture of FIG. 1 incorporated in a sterilization tray. 
     FIG. 4 is a partial top plan view of the torquing fixture of FIG.  1 . 
     FIG. 5 is a top plan view of the torquing fixture and sterilization tray of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-5 depict an exemplary sterilization tray  2  having a bottom wall  4  and opposing pairs of side walls  6  and  8 . A lid  10  is provided to close the open top of the tray. The tray  2  and lid  10  are perforated  12  to let a sterilant, e.g. steam, in and out of the tray  2 . Preferably the tray  2 , is made of a lightweight, rigid material, e.g. aluminum or aluminum alloy. The lid  10  is preferably made of a transparent, lightweight material, e.g. plastic. 
     A torquing fixture  20  is incorporated into the tray  2 . The torquing fixture  20  includes apertures  22  for receiving an implant to be torqued. Each aperture  22  forms an opening through the torquing fixture and has a peripheral wall  24  defining the aperture  22  shape. The torquing fixture  20  is preferably made of a high strength, non-staining sheet material, e.g. stainless steel. A suitable material is 17-4 stainless steel which is a commonly used stainless steel alloy used for surgical instruments. The torquing fixture  20  is advantageously formed by punching or cutting from the sheet material and then bending to final shape. In one embodiment, the torquing fixture  20  is permanently attached to the sterilization tray  2 , e.g. with. rivets  26 . In an alternative embodiment, the torquing fixture  20  is removable from the tray  2  so that it can be used separate from the tray  2 . In either case, the torquing fixture preferably includes feet  27  for engaging the bottom wall  4  and an edge  28  for engaging side wall  8  to help stabilize the fixture when it is in the tray. 
     A modular tibial knee implant  30  includes a tibial base plate  32 , an articular surface  34 , and a fixation screw  36  for attaching the articular surface  34  to the base plate  32 . A torque wrench  38  engages screw  36  for applying a specified torque. Each aperture  22  is sized to receive a different size base plate  32 . The aperture  22  receives the base plate  32  in torque transmitting relation such that the peripheral wall  24  positively engages the contours of the base plate  32  to prevent the base plate from turning when the screw  36  is torqued. The material for the torque fixture  20  is chosen to be of sufficient strength, hardness, and gauge that it does not deform or transfer material to the base plate  32  when torque is applied to the implant. Preferably the fit between the aperture  22  and the base plate  32  is such that motion that could lead to scratching or otherwise marring the implant is minimized. Each aperture  22  is advantageously shaped based on the shape of different styles of tibial base plates  32  so that it positively engages each of the different styles of a particular size in the same aperture. For example, the tibial base plate  32  shown is available for a particular size, e.g. size  4 , in several different styles or shapes including, e.g. sharp fluted stem, fluted stem, and pegged. The peripheral wall of one aperture  24  is designed to engage each of these styles. The engagement with one style of base plate  32  is shown in FIG.  4 . It has been found that a tri-lobed, or clover shaped, design as shown in the figures can be shaped to positively engage each of these styles. 
     In use, the instrument tray  2  is positioned in the operating room in a convenient location, e.g. a table adjacent the operating table. It typically would contain various instruments used in the implantation procedure. The implantation site for the tibial implant is prepared for receiving the implant as is known in the art. Once the appropriate components have been chosen for the particular patient, they are assembled in the torquing fixture as shown in FIG.  1 . The wrench  38  is engaged with the screw  36  and a predetermined torque is applied to the screw  36 . The weight of the instrument tray  2  counteracts the torque applied to the screw  36 . If further resistance is needed, it is an easy matter to grip the tray  2  or press down on it. The case can also be counter torqued or rotated to counter the applied torque. Because of the relatively large size of the case  2  it is easier to grip and stabilize than the small implant wrenches known in the prior art. 
     It will be understood by those skilled in the art that the foregoing has described a preferred embodiment of the present invention and that variations in design and construction may be made to the preferred embodiment without departing from the spirit and scope of the invention defined by the appended claims.