Distinguishing Acetabulum Cup Retroversion From Anteversion on Anteroposterior Radiographs After Total Hip Arthroplasty

A computerized ellipse method (Liaw's version) for measurement and detection of acetabulum cup retroversion.

Total hip arthroplasty (THA) is considered to be the best and most reliable treatment of end-stage hip disorders with satisfactory long-term clinical outcomes. However,the incidence of postoperative dislocation ranges from 0.3% to 3% in primary THA. The most important risk factor is malpositioning of implant components. Generally, excessive anteversion and retroversion increase risk of anterior and posterior hip dislocation respectively. Several radiological methods have been proposed to measure anteversion of the acetabular cup on plain radiographs, but most of these methods cannot accurately distinguish cup retroversion from anteversion. In this article, we will demonstrate and prove a computerized ellipse method (Liaw's version) for measurement and detection of acetabulum cup retroversion.