It is not always clear why some patients experience recurrent dislocation following total hip arthroplasty (THA). In order to plan appropriate revision surgery for such patients, however, it is important to understand the specific biomechanical basis for the dislocation. We have developed a novel method to analyse the biomechanical profile of the THA, specifically to identify edge loading and prosthetic impingement, taking into account spinopelvic mobility. In this study we compare the results of this analysis in THA patients with and without recurrent dislocation. Post-operative CT scans and lateral standing and seated radiographs of 40 THA patients were performed, 20 of whom had experienced postoperative dislocation. The changes in pelvic and femoral positions on the lateral radiographs were measured between the standing and seated positions, and a 3D digital model was then generated to simulate the movement of the hip when rising from a chair for each patient. The path of the joint reaction force (JRF) across the acetabular bearing surface and the motion of the femoral neck relative to the acetabular margin were then calculated for this “sit-to-stand” movement, in order to identify where there was risk of edge loading or prosthetic impingement.Background
Methods
