Bony balancing apparatus and method for total knee replacement

Abstract

Total knee replacement surgery is improved through custom cuts on the distal femur without resorting to expensive computer navigation. The method involves measurement, on plain radiographs prior to surgery, the amount of bone that would be resected on each knee, medially and laterally on the distal femur. In the preferred embodiments, the predetermined distance is in the range of 8-10 mm, more preferably 10 mm, and the resulting distance from the second line to the apex of the lateral condyle is in the range of 6 to 7 mm. A cutting fixture is provided and used to resect the medial condyle at the predetermined distance and the lateral condyle at the measured resulting distance.

1 . A method of resecting a distal femur in conjunction with total knee replacement surgery, comprising the steps of:
 obtaining an x-ray image of a patient's femur, the image including a hip joint with a femoral head and a knee joint with medial and lateral condyles and an intercondylar notch;   identifying a first line on the image from the center of the femoral head to the center of the distal femur and the intercondylar notch;   identifying a second line perpendicular to the first line, the second line being at a predetermined, arbitrary distance from the apex of the medial condyle;   measuring the resulting distance from the second line to the apex of the lateral condyle;   providing a cutting fixture to resect the medial condyle at the predetermined distance and the lateral condyle at the measured resulting distance; and   resecting the medial and lateral condyles using the fixture.   
     
     
         2 . The method of  claim 1 , wherein the predetermined distance is in the range of 8-10 mm. 
     
     
         3 . The method of  claim 1 , wherein the predetermined distance is approximately 10 mm. 
     
     
         4 . The method of  claim 1 , wherein the predetermined distance is approximately 10 mm and the resulting distance from the second line to the apex of the lateral condyle is in the range of 6 to 7 mm. 
     
     
         5 . The method of  claim 1 , wherein the cutting fixture includes:
 at least one cutting slot; and   at least one device for measuring the distance between the apex of the medial condyle and the cutting slot.   
     
     
         6 . The method of  claim 1 , wherein the cutting fixture includes:
 at least one cutting slot; and   at least one device for measuring the distance between the apex of the medial condyle and the cutting slot and the distance between the apex of the lateral condyle and the cutting slot.   
     
     
         7 . The method of  claim 1 , wherein the cutting fixture includes separate slots for the resecting the medial and lateral condyles. 
     
     
         8 . The method of  claim 1 , wherein the cutting fixture includes:
 two separate slots, one for resecting the medial condyle and the other for resecting the lateral condyle; and   one or more devices for measuring the distance between the apex of the medial condyle and the slot for resecting the medial condyle and for measuring the distance between the apex of the lateral condyle and the slot for resecting the lateral condyle.   
     
     
         9 . The method of  claim 1 , wherein the cutting fixture includes:
 two separate slots, one for resecting the medial condyle and the other for resecting the lateral condyle; and   a mechanism for ensuring that the two slots are at all times co-planar.   
     
     
         10 . The method of  claim 1 , wherein the cutting fixture is initially rotatable to first adjust for the predetermined distance. 
     
     
         11 . The method of  claim 1 , wherein the cutting fixture includes an arm configured for placement on the outer cortex of a femur. 
     
     
         12 . The method of  claim 1 , including the step of obtaining a digital, standing x-ray image of a patient's femur.