Intraoperative simulation and planning using a combined acetabular and femoral (CAF) navigation system for total hip replacement

Abstract

This paper describes intraoperative simulations for the limb length and the range of motion (ROM) adjustment in total hip relacement (THR) surgery, and their utility in intraoperative planning. After implantation of the cup and stem, final adjustments can be made to the limb length and ROM by selecting the optimal combination of femoral neck and head components from the range available in a changeable modular system. The aim of this work is to provide intraoperative assistance to the surgeon in selecting the optimal component combination as well as in planning additional osteotomy to remove unwanted bone impingements and widen the safe ROM. Using the positions and orientations of the cup and stem intraoperatively measured by a combined acetabular and femur (CAF) navigation system, limb length and ROM simulations are carried out for neck and head components of various lengths and angles. These simulations provide information on limb length, the ROM, and where in a 3D model impingements will occur for each combination of components. The accuracy of the simulations was evaluated by comparison with postoperative CT data for the limb length and actually measured motions for the ROM.