Bone resection apparatus and method for knee surgery

Abstract

A bone resection apparatus and its method of use for knee surgery are presented. In one aspect of the invention, the apparatus includes a spacer and a tibial cut guide. The spacer has a first surface engageable with the cut distal femoral bone and a second surface opposite the first surface engageable with the uncut proximal tibial bone in joint articulating relationship. The spacer further includes a cut guide support. The tibial cut guide has a cutter guide defining a cut plane and a support engaging element engageable with the cut guide support. The cut guide support and support engaging element cooperate to position the cut plane in relative to the first surface.

1 . A system for guiding a bone cut comprising:
 at least one spacer having a first surface configured to engage a surface of a cut distal femoral bone, a second surface opposite the first surface configured to engage an uncut proximal tibial bone and to reestablish a joint articulating relationship between the cut femoral bone and the uncut tibial bone;   a tibial cut guide defining a cut plane and a support engaging element; and   a cut guide support engageable with the at least one spacer and the tibial cut guide to position the cut plane at a predetermined posterior slope angle relative to the first surface.   
     
     
         2 . The system of  claim 1 , wherein the surface is planar. 
     
     
         3 . The system of  claim 1 , wherein the second surface comprises an arcuate condylar surface generally in the shape of an anatomic femoral condyle. 
     
     
         4 . The system of  claim 1 , wherein the second surface is curved in a sagittal plane to correspond to an anterio/posterior curvature of an anatomic femoral condyle. 
     
     
         5 . The system of  claim 4 , wherein the second surface is curved in a frontal plane to correspond to a medial/lateral curvature of an anatomic femoral condyle. 
     
     
         6 . The system of  claim 4 , wherein the at least one spacer comprises a plurality of spacers having a convexly curved second surface, each one of the second surfaces having a different curvatures to permit selection of a spacer that best matches a patient's anatomy or that best corrects an anatomical defect in the patient. 
     
     
         7 . The system of  claim 3 , wherein the at least one spacer has a condylar thickness, the at least one spacer comprising a plurality of spacers each having a different condylar thickness. 
     
     
         8 . The system of  claim 1 , wherein the cut guide support comprises an elongated member having a longitudinal axis and in an assembled configuration the cut guide support projects outwardly from the at least one spacer. 
     
     
         9 . The system of  claim 1 , wherein in an assembled configuration with the at least one spacer a longitudinal axis of the cut guide support forms a predetermined tibial posterior slope angle relative to the first surface. 
     
     
         10 . The system of  claim 1 , wherein the at least one spacer comprises a plurality of spacers and wherein in an assembled configuration with the cut guide support each one of the plurality of spacers has a different posterior slope angle between zero and ten degrees. 
     
     
         11 . The system of  claim 1 , wherein the cut support comprises a non-circular cross section and the tibial cut guide comprises a an aperture having a non-circular cross section configured to receive the support, and wherein in an assembled configuration the aperture and cut guide support permit linear translation of the cut guide relative to the at least one spacer and maintain a fixed posterior slope angle between the cut guide and the at least one spacer. 
     
     
         12 . The system of  claim 1 , wherein the cut guide support comprises a circular cross section and the tibial cut guide comprises an aperature having a circular cross section configured to receive the cut guide support, and wherein in an assembled configuration the aperture and the cut guide support permit linear translation of the cut guide relative to the at least one spacer, varus/valgus rotation of the cut guide relative to the at least one spacer, and maintain a fixed posterior slope angle between the cut guide and the at least one spacer. 
     
     
         13 . The system of  claim 1 , wherein the cut guide includes a saw slot defining the cut plane, and wherein in an assembled configuration the cut plane is oriented parallel to the longitudinal axis of the cut guide support. 
     
     
         14 . The system of  claim 1 , wherein the cut guide includes at least one fixation hole having a longitudinal axis, the at least one fixation hole being oriented such that in an assembled configuration the longitudinal axis of the fixation hole is parallel to the longitudinal axis of the cut guide support. 
     
     
         15 . A system comprising:
 an implant system including a femoral component having a femoral component thickness and a tibial component having a tibial component thickness, the implant system having an overall implant thickness which is the sum of the femoral component thickness, the tibial component thickness; and an additional joint laxity distance corresponding to a desired amount of joint laxity;   at least one spacer having a body including a planar seating surface, an arcuate condylar surface arching away from the seating surface generally in the shape of an anatomic femoral condyle, and an elongated support having a longitudinal axis, the spacer having a spacer thickness normal to the planar seating surface; and   a tibial cut guide including an aperture having a longitudinal axis, the aperture configured to engage the cut guide support for linear translation of the cut guide parallel to the aperture longitudinal axis, a cutter guide slot defining a cut plane oriented parallel to the aperture longitudinal axis, the cut plane being spaced a predetermined distance from the aperture such that in an assembled configuration the cut plane is spaced from the arcuate condylar surface by a tibial resection distance.   
     
     
         16 . The apparatus of  claim 15 , wherein the at least one spacer comprises a plurality of spacers, each one of the plurality of spacers having a different spacer thickness, wherein in an assembled configuration each one of the pluarlaity of spacers establishes a different tibial resection distance. 
     
     
         17 . The apparatus of  claim 15 , wherein in an assembled configuration the cut plane is spaced from the planar seating surface a distance equal to the overall implant thickness. 
     
     
         18 . A method of performing knee surgery comprising:
 resecting a portion of a distal femoral bone;   inserting a spacer into the knee joint to abut a cut surface of the distal femoral bone, the spacer having an arcuate condylar portion facing away from the cut surface;   abutting the arcuate condylar portion with a surface of a proximal tibial bone:   mounting a tibial cut guide on the spacer to position a cut plane at a predetermined posterior slope angle and at a depth relative to the cut surface of the distal femoral bone; and   guiding a cutter in the cut plane to form a planar surface on the proximal tibial bone.   
     
     
         19 . The method of  claim 18 , further comprising, before the step of mounting the tibial cut guide, the steps of:
 articulating the knee joint between flexion and extension such that the surface of the proximal tibial bone articulates with the arcuate condylar portion of the spacer to evaluate knee kinematics; and   placing the knee joint in extension.   
     
     
         20 . The method of  claim 18 , further comprising, after guiding a cutter, mounting a femoral implant component on the resected distal femoral bone and mounting a tibial implant component on the proximal tibial bone, wherein inserting a spacer comprises inserting a spacer having a thickness corresponding to the femoral implant component thickness plus an additional thickness corresponding to a desired joint laxity such that the cut guide guides the cutter to remove a portion of proximal tibial bone equal in thickness to the tibial implant component thickness.