Acetabular retroversion, defined by the crossover sign (COS) on plain film radiographs, (Figure 1) is thought to cause early onset osteoarthritis (OA). When the COS is present, the anterior acetabular rim is lateral to the posterior acetabular rim proximally. As the rim progresses distally, the posterior rim crosses lateral to the anterior rim, creating the COS. Clinical studies have demonstrated that hips with OA have a higher incidence of acetabular retroversion than normal hips [1–3]. There are two possible mechanical links between acetabular retroversion and OA. First, decreased area in the posterior acetabulum may cause abnormally high cartilage contact stresses in the posterior acetabulum during activities of daily living. Alternatively, pincer femoroacetabular impingement may cause posterior damage via posterior subluxation [4–6]. Although clinical studies suggest that retroverted hips have altered cartilage mechanics, cartilage mechanics cannot be measured in-vivo. However, finite element (FE) modeling can be used to predict mechanics, and thereby identify possible mechanical mechanisms of OA development in patient populations. Therefore, the objective of this study was to compare cartilage contact mechanics between normal hips and hips with acetabular retroversion using a validated approach to subject-specific FE modeling [7].

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