Mis patellar preparation

Abstract

Instruments and a method for preparing the articular surface of the patella to receive a patellar implant are utilized without everting the patella. A medial or lateral parapatellar incision and an anterior midline incision are made adjacent the patella. The patella is clamped with a patella clamp, a hole is drilled from the anterior surface of the patella. A reamer is inserted through the medial or lateral parapatellar incision and is then attached to the end of a drive shaft that extends outwardly beyond the articular surface of the patella. The posterior facing cutting surface of the reamer device is then placed in contact with the articular surface. The drive shaft is then rotated and moved anteriorly causing the cutting surface of the reamer device to remove a desired amount of patellar cartilage and bone to accommodate a patellar component. The patellar component is secured into place by aligning a central peg protruding from the top surface of the patellar component with the previously drilled hole in the patellar remnant.

1 . A reamer system for resecting a posterior surface of a patella comprising:
 a guide shaft extending from an anterior surface of the patella through at least the posterior surface of the patella along a first axis;   a reamer having a cutting surface adapted to receive the guide shaft along the first axis;   a drive shaft extending along a second axis offset from the first axis; and   a gear engaged to the drive shaft and rotatable about the second axis,   wherein the gear when engaged to the reamer is capable of rotating the reamer about the first axis as the drive shaft is driven about the second axis.   
   
   
       2 . The reamer system of  claim 1 , wherein the second axis is substantially parallel to the first axis. 
   
   
       3 . The reamer system of  claim 1 , further comprising means for moving the reamer anteriorly along the first axis for resecting the posterior surface of the patella. 
   
   
       4 . The reamer system of  claim 3 , further comprising means for moving the gear anteriorly along the second axis while the reamer is moved anteriorly along the first axis. 
   
   
       5 . The reamer system of  claim 1 , wherein at least a portion of the guide shaft is housed within a first bushing. 
   
   
       6 . The reamer system of  claim 5 , wherein at least a portion of the drive shaft is housed within a second bushing. 
   
   
       7 . The reamer system of  claim 6 , wherein the first and second bushings are connected to each other by an arm extending between the bushings. 
   
   
       8 . The reamer system of  claim 7 , wherein the second bushing is connected to a base by a pair of arms extending upward from the base. 
   
   
       9 . A reamer system for resecting a posterior surface of a patella comprising:
 a guide shaft extending from an anterior surface of the patella through at least the posterior surface of the patella along a first axis;   a reamer having a cutting surface adapted to receive the guide shaft;   a first gear engaged to the reamer for rotation therewith about the first axis;   a second gear engaged to the first gear, the second gear capable of rotating the first gear about the first axis; and   a drive shaft engaged to the second gear.   
   
   
       10 . The reamer system of  claim 9 , wherein the second gear is rotatable about a second axis transverse to the first axis of the guide shaft. 
   
   
       11 . The reamer system of  claim 10 , wherein the first axis and the second axis are substantially perpendicular. 
   
   
       12 . The reamer system of  claim 9 , further comprising:
 a housing including the first gear and the second gear therein, the housing having an outside surface including an attachment element fixed thereto.   
   
   
       13 . The reamer system of  claim 12 , wherein the attachment element is attached to a clamp having means for moving the reamer anteriorly along the first axis for resecting the posterior surface of the patella. 
   
   
       14 . The reamer system of  claim 12 , wherein the housing further includes an inside bottom surface having an axle fixed thereto. 
   
   
       15 . The reamer system of  claim 14 , wherein the first gear is centered about the axle along the first axis. 
   
   
       16 . The reamer system of  claim 15 , wherein the guide shaft, reamer, first gear and axle are all aligned along the first axis. 
   
   
       17 . A reamer system for resecting a posterior surface of a patella comprising:
 a guide shaft extending from an anterior surface of the patella through at least the posterior surface of the patella along a first axis;   a reamer having a cutting surface adapted to receive the guide shaft;   a first gear engaged to the reamer for rotating the reamer about the first axis; and   a drive means operatively engaged to the first gear for driving the first gear.   
   
   
       18 . The reamer system of  claim 17 , further comprising a second gear engaged to the first gear, the second gear capable of rotating the first gear about the first axis, wherein the drive means is engaged to the second gear. 
   
   
       19 . The reamer system of  claim 18 , wherein the second gear is rotatable about a second axis transverse to the first axis of the guide shaft. 
   
   
       20 . The reamer system of  claim 19 , wherein the second gear is a worm gear. 
   
   
       21 . The reamer system of  claim 18 , wherein the second gear is a rack located on a second axis and the first gear is a pinion, the second axis being perpendicular to the first axis of the guide shaft.