Tension and motion measurement for extended trochanteric osteotomy with different fixation methods.

The revision of total hip arthroplasty (THA) is becoming an increasingly common procedure around the world. The extended trochanteric osteotomy (ETO) has proved to be an effective way in revision of THA. Four generations of trochanteric osteotomy fixation systems have been developed, all of which has its own clinical application. However, few studies on the biomechanical stability of the above fixation methods have been reported, though many clinical follow-up studies showed some postoperative functional differences among them. Research in this field is mainly subject to constraints of measurement devices and 3D motion analysis. We designed a synchronous testing approach to acquire the tension data loaded to the greater trochanter and minimal rotation or migration of osteotomy fragment which could not be solved by strain gauge method. Active markers were designed to precisely track proximal femoral bed and the osteotomy fragment in 3D space. Six cadaver femurs constructed as vitro biomechanical models were chosen for a preliminary study. Each femur underwent the steps of prosthesis implanting, ETO and a series of five fixation methods in a random order with 2 wires, 3 wires, 2 wires and a short claw plate,2 cables and a short claw plate, and a long claw plate. We also gave a preliminary result of the displacement of fragment and the stiffness of femur after ETO in this paper. Further clinical significance remains to be discussed.