The association between hip morphology parameters and nineteen-year risk of end-stage osteoarthritis of the hip: a nested case-control study.

Objective. Subtle deformities of the hip joint areimplicated in the etiology of osteoarthritis (OA) of thehip. Parameters that quantify these deformities may aidunderstanding of these associations. We undertook thisstudy to examine relationships between such parametersand the 19-year risk of total hip arthroplasty(THA) for end-stage OA.Methods. A new software program designed formeasuring morphologic parameters around the hip wasdeveloped and validated in a reliability study. THA wasthe outcome measure for end-stage OA. A nested case–control study was used with individuals from a cohort of1,003 women who were recruited at year 1 in 1989 andfollowed up to year 20 (the Chingford Study). All hipswith THA by year 20 and 243 randomly selected controlhips were studied. Pelvis radiographs obtained at year 2were analyzed for variations in hip morphology. Measurementswere compared between the THA case groupand the control group.Results. Patients with THA had a higher prevalenceof cam deformity than did their respective controls(median alpha angle 62.4° versus 45.8° [P ? 0.001];mean modified triangular index height 28.5 mm versus26.9 mm [P ? 0.001]) as well as a higher prevalence ofacetabular dysplasia (mean lateral center edge angle29.5° versus 34.3° [P ? 0.001]; median extrusion index0.25 versus 0.185 [P ? 0.009]). Logistic regressionanalyses clustering by subject and adjusting for radiographichip OA at year 2 showed that these morphologicparameters were still significantly associated with THAby year 20. The alpha angle and lateral center edgeangle predicted the risk of THA independently whenincluded in the same model.Conclusion. This investigation describes measurementsthat predict the risk of THA for end-stage OAby year 20, independently of the presence of radiographichip OA at year 2. These measurements can bemade on an anteroposterior pelvis radiograph, which isan inexpensive and commonly used clinical method ofinvestigation