An accurate and reproducible method for locating the joint line during a revision total knee arthroplasty

Studies have shown that the position of the joint line has a direct effect on postoperative results, including range of motion, functional knee scores, and midflexion stability. Four anatomic landmarks were investigated as references for locating the joint line during a revision knee surgery--the medial femoral epicondyle, the fibular head, the tibial tubercle, and the inferior pole of the patella. Measurements from 6 cadaver knees identified the distance of each landmark to the joint line. These distances were used to design instruments to aid in the intraoperative positioning of the joint line. The instruments were validated on 94 primary total knees. The instrument referencing the medial epicondyle had 99% and 93% accuracy for locating the natural position of the joint line within 5 and 3 mm, respectively.