Modular patella instrument

Abstract

A patella clamp has a first part including a reference surface engageable with the anterior surface of a patella. The first part includes a stop surface spaced from the reference surface. A second clamping part is provided which is moveable with respect to the first clamping part. A cutting element coupled to the first clamping part is moveable with respect to the first part. The cutting element includes a shaft with an adjustable collar mounted on the shaft for movement with respect to the longitudinal axis of the shaft and cutting element. The adjustable collar on the shaft is engageable with a stop surface on the first part for spacing the cutting element a desired distance from the reference surface. A pair of gages are provided for selectively setting the position of the adjustable collar with respect to either the amount of patella bone being removed or the amount of patella bone remaining.

1 . A patellar resurfacing clamp comprising: 
 a first part having a first surface engageable with a surface of the patella and including a second surface spaced from said first surface;    a second part moveable with respect to the first part;    a patella cutting element coupled to said first part and moveable with respect to said first part, said cutting element having a shaft and an adjustable collar mounted on the shaft for movement with respect to a longitudinal axis of the shaft, said adjustable collar on said shaft having a first stop surface engageable with said second surface on said first part for spacing said cutting element a distance from said first surface; and    at least one gage element for selectively setting the position of said adjustable collar on said shaft with respect to the first surface contacting the patella based on either the amount of patella bone being removed or the amount of patella remaining.    
     
     
         2 . The patella clamp as set forth in  claim 1  wherein there are two gage elements, one for setting the position of said collar along the shaft with respect to said amount of bone removed and one for setting the position of said collar along the shaft with respect to the amount of bone remaining.  
     
     
         3 . The patellar clamp as set forth in  claim 1  wherein the shaft is a drive shaft.  
     
     
         4 . The patellar clamp as set forth in  claim 3  wherein said shaft has a portion having external teeth for engaging the collar.  
     
     
         5 . The patellar clamp as set forth in  claim 4  wherein said collar has an internal locking element for selectively engaging said external teeth on said shaft to set the adjustment of said collar along said longitudinal axis.  
     
     
         6 . The patellar clamp as set forth in  claim 5  wherein said collar is moveable from a first position where said collar may slide with respect to said shaft to a second position where said teeth on said shaft and said collar engage and prevent further axial movement.  
     
     
         7 . The patellar clamp as set forth in  claim 1  wherein said second part includes a tubular clamping jaw for engaging a surface of the patella opposite a patella surface engaging said first surface of said first part.  
     
     
         8 . The patellar clamp as set forth in  claim 7  wherein said tubular clamping jaw acts as a guide for said cutting element.  
     
     
         9 . The patellar clamp as set forth in  claim 8  wherein said tubular clamping jaw is removably attached to said second part so that a size of said jaw may be varied by providing a plurality of clamping jaws of different diameters.  
     
     
         10 . The patellar clamp as set forth in  claim 7  wherein said clamping jaw includes teeth for engaging the patella bone.  
     
     
         11 . The patellar clamp as set forth in  claim 1  wherein said second part includes a scale indicating a posterior-anterior thickness of said patella.  
     
     
         12 . The patellar clamp as set forth in  claim 1  wherein said cutting element is an end mill.  
     
     
         13 . The patella clamp as set forth in  claim 1  wherein said cutting element is a reamer.  
     
     
         14 . The patellar clamp as set forth in  claim 1  wherein said shaft includes a stop surface for engaging a second stop surface on said collar and upon engagement of said surfaces said collar first stop surface is spaced from said first part second stop surface a distance allowing a cutting face of said cutting element to be positioned adjacent said first surface of said first part when said collar first stop surface and said first part second surface contact.  
     
     
         15 . The patellar clamp as set forth in  claim 14  wherein the distance between said collar second stop surface and said shaft stop surface element along said longitudinal axis is equal to the bone remaining on the patella after cutting the patellar by moving said cutting element until said collar first stop surface engages said second surface of said first part.  
     
     
         16 . The patellar clamp as set forth in  claim 15  wherein said at least one gage element has a plurality of steps of different height for varying the bone remaining thickness on the patella by spacing the second stop surface of the collar a desired distance from said stop surface on said shaft.  
     
     
         17 . The patellar clamp as set forth in  claim 16  wherein the distance between said collar first stop surface and said first part second surface is equal to the bone to be removed from the patella.  
     
     
         18 . The patella clamp as set forth in  claim 17  wherein said at least one gage has a plurality of steps of different height for varying the amount of patella bone removed by spacing the collar first stop surface a desired distance from said first part second surface.  
     
     
         19 . A patella clamping system comprising: 
 a first clamp part having a reference surface engageable with an anterior surface of a patella, said first part including a stop surface spaced from said reference surface along an axis;    a second clamp part moveable with respect to said first clamp part along said axis;    a cutting element for resecting bone from a patella rotatably mounted on said first clamp part and moveable with respect to said axis, said cutting element having a first adjustable stop surface engageable with said stop surface on said first clamp part;    a first gage element for setting the position of said adjustable stop surface with respect to the reference surface on said first clamp based on the amount of bone to be removed from the patella; and    a second gage element for setting the position of said adjustable stop surface with respect to the reference surface on said first clamp based on the amount of bone to remain on the patella.    
     
     
         20 . The patellar clamp as set forth in  claim 19  wherein said cutting element includes a shaft having a stop surface for engaging a second adjustable stop on said cutting element surface and upon engagement of said surfaces, said first adjustable stop surface on said cutting element is spaced from said first part stop surface a distance allowing a cutting face of said cutting element to be positioned adjacent said reference surface of said first part when said adjustable first stop surface and said first clamp part stop surface contact.  
     
     
         21 . The patellar clamp as set forth in  claim 20  wherein the distance between said second adjustable stop surface and said shaft stop surface along said axis is equal to the bone remaining on the patella after cutting the patella by moving said cutting element until said first adjustable stop surface engages said stop surface of said first clamp part.  
     
     
         22 . The patellar clamp as set forth in  claim 21  further comprising at least one gage element having a plurality of steps of different height for varying the bone remaining thickness on the patella by spacing the second adjustable stop surface of a desired distance from said stop surface on said shaft.  
     
     
         23 . The patellar clamp as set forth in  claim 22  wherein the distance between said first adjustable stop surface and said first clamp part stop surface is equal to the bone to be removed from the patella.  
     
     
         24 . The patella clamp as set forth in  claim 23  wherein said at least one gage has a plurality of steps of different height for varying the amount of patella bone removed by spacing the first adjustable stop surface a desired distance from said first clamp part stop surface.  
     
     
         25 . A kit of instruments for preparing a patella for receiving an implant comprising: 
 a clamp having at least two carriers for releasably mounting clamping elements;    at least two cutting elements of different size for engaging a posterior surface of the patella and adapted for releasably mounting on said clamp; and    at least two clamping elements adapted to engage a peripheral surface of the patella extending between the posterior surface and an anterior surface of the patella said clamping elements adapted for releasably mounting on said carriers.    
     
     
         26 . The kit as set forth in  claim 25  further comprising at least two clamping elements of different size for engaging a posterior surface of said patella, said two clamping elements adapted to releasably engage at least one of said carriers.  
     
     
         27 . The kit as set forth in  claim 26  further comprising at least two clamping elements of different size shaped to engage the anterior surface of a patellar implant, said implant engaging clamps adapted for releasably mounting on at least one of said carriers.  
     
     
         28 . The kit as set forth in  claim 26  further comprising at least two clamping elements in the form of drill guides for engaging the posterior side of a patella, said drill guide adapted to releasably engage at least one of said carriers.  
     
     
         29 . The kit as set forth in  claim 25  further comprising at least two clamping elements shaped to engage the posterior surface of a patellar implant, said implant engaging clamps adapted for releasably mounting on at least one of said carriers.  
     
     
         30 . The kit as set forth in  claim 25  further comprising at least one gage element for setting the amount of bone to be removed from the patella during preparation and at least one gage element for setting the amount of bone to remain on the patella after preparation.  
     
     
         31 . The kit as set forth in  claim 26  wherein said clamping elements for engaging the posterior surface of the patella have a tubular shape.  
     
     
         32 . The kit as set forth in  claim 31  wherein a circumferential surface of said tubular clamping element contacting said patella has teeth for engaging patellar bone.  
     
     
         33 . The kit as set forth in  claim 25  wherein a bone contacting surface of said two clamping elements engaging the periphery of the patella include teeth.  
     
     
         34 . The kit as set forth in  claim 25  wherein the at least two cutting elements are milling cutters.