Developmental dysplasia of the hip: is acetabular retroversion a crucial factor?

OBJECTIVE The objective of this study was to investigate a possible relation between congenital hip dysplasia and acetabular retroversion and to explore the eventual influence of the latter in the surgical decision for periacetabular osteotomy. MATERIALS AND METHODS We assessed the classical morphological characteristics of both hips, with an additional newly described retroversion index. The study was conducted in 174 patients with uni- or bilateral congenital hip dysplasia having undergone unilateral (153 patients) or bilateral (21 patients) periacetabular osteotomy when respectively one or both dysplastic hips remained symptomatic. RESULTS In the group of operated hips (195 hips in total), 53% of the acetabuli were anteverted, 42% retroverted, and 5% neutral orientations. The group of nonoperated hips (153 hips) included 24% normal hips, 22% hips with normal coverage but retroverted, 35% dysplastic hips with anteverted or neutral orientation, and 19% dysplastic retroverted hips. Comparing the two hips in the subgroup of patients in whom the operated and nonoperated sides were both dysplastic failed to demonstrate statistically significant difference in the mean retroversion index. However, all the other variables measured were significantly different; with the operated side more dysplastic. Comparing the two hips in the other subgroups showed that acetabular retroversion was nearly always bilateral and symmetrical, even in presence of unilateral congenital dysplasia. DISCUSSION Our data suggest that the presence of acetabular retroversion is probably independent of the congenital hip dysplasia and that this abnormality seems at best a secondary factor in the appearance of dysplastic hip symptoms. LEVEL OF EVIDENCE Level IV, retrospective diagnostic study.