Acetabular coverage after innominate osteotomy.

A criticism of innominate osteotomy is that it may cause relative acetabular retroversion, predisposing to osteoarthritis. This study was designed to address that hypothesis. We had access to standing hip radiographs of 30 patients (36 hips) who had undergone open reduction and innominate osteotomy for late presenting developmental hip dislocation at least 40 years earlier. A single independent investigator used the validated method of Hefti (1995) to measure anterior and posterior acetabular coverage, contact area, and version. Ten operated hips had advanced osteoarthritis obscuring acetabular landmarks. Twenty-six operated hips were readable despite some radiographs showing signs of mild-to-moderate osteoarthritis. Twenty contralateral hips without developmental hip dysplasia formed a comparison group and 21 age-matched and sex-matched "normal hips" were used as a control. A significant difference between the groups was found for contact area (P < 0.001). There was no significant difference between the other 3 outcomes: anterior coverage (P = 0.509), posterior coverage (P = 0.135), and anteversion (P = 0.845). Anteversion in hips with a good outcome after innominate osteotomy and open reduction was not different to a control group of radiographically normal hips. The early osteoarthritic changes seen in these hips may relate to decreased contact area compared with the normal population. In this series, innominate osteotomy before the age of 5 years did not consistently cause acetabular retroversion that persisted into adulthood. Apparently unaffected hips contralateral to the dislocated side display reduced contact area relative to controls indicating probable occult dysplasia.