Hip dysplasia and osteoarthrosis

INTRODUCTION: Hip dysplasia (HD) is assumed to be an etiological factor in the development of premature hip osteoarthrosis (OA). We established the prevalences of HD and OA in adults according to qualified radiographic discriminators, and investigated the relationship between HD and OA. METHODS: Wiberg's CE angle (CE), Sharp's angle, the femoral head extrusion index, the acetabular depth ratio (ADR), the radiographic OA discriminators of Croft, and of Kellgren and Lawrence, and also minimum joint space width (JSW) or = 5 mm). Average CE angle was 34 degrees in men (SD 7.3 degrees), and 35 degrees in women (SD 7.6 degrees). Applying a CE cut-off value of 20 degrees for designation of definite hip dysplasia, we found a prevalence of hip dysplasia of 3.4%. Approximately 2% of cases were unilateral and 1.4% of cases were bilateral. We found significant relationships between radiographic OA discriminators and the CE angle, femoral head extrusion index and ADR. Odds ratios ranged from 1.0 to 6.2. Compared to subjects with OA in morphologically normal hips, a trend towards younger age in subjects with HD and OA was noted, but this was not strictly significant. INTERPRETATION: We found that HD is not uncommon in the general population. The assumption that HD is an etiological factor in the development of hip OA was confirmed.