MALROTATION ASSOCIATED WITH IMPLANT ALIGNMENT TECHNIQUE IN TOTAL KNEEARTHROPLASTY

This study documents the malrotation between the femoral and tibial co mponents associated with contemporary alignment techniques that positi on the tibial component relative to the tubercle, posterior tibial con dyles, transtibial axis, and malleoli, The technique that allows the t ibial component to float into alignment as the knee is passed through a range of motion and the technique of coupling the tibial component t o the femoral component also were assessed, The average external rotat ion of the tibial component relative to the femoral component associat ed with each alignment technique is 19 degrees (tibial tubercle), 5 de grees (transtibial axis), 7 degrees (posttibial axis), 3 degrees (mall eolar axis), and 14 degrees (range-of-motion technique). The coupled-c omponent technique produced 2 degrees internal rotation. The observed tendency to externally rotate the tibial component relative to the fem oral component with most alignment techniques may account for the high incidence of posteromedial polyethylene wear reported in retrieval st udies.