The bicompartmental acetabulum is one of the morphological changes which may be seen in children with Legg-Calvé-Perthes’ disease. Three-dimensional CT and MRI were used to analyse the detailed morphology of the acetabulum with special reference to its inner surface, in 16 patients with Perthes’ disease and a bicompartmental acetabulum. The bicompartmental appearance was seen on the coronal plane image through the acetabular fossa. The lunate surface was seen to grow laterally resulting in an increased mediolateral thickness of the triradiate cartilage. On the horizontal plane images, the acetabular fossa had deepened and had a distinct prominence at its posterior border. The combination of these morphological changes resulted in a bicompartmental appearance on plain radiography. Acetabular bicompartmentalisation appears to be the result of an imbalance of growth between the cartilage-covered lunate surface and the cartilage-devoid acetabular fossa

The treatment of osteochondritis dissecans after Legg-Calvé-Perthes’disease hasnot been clearly determined. It may be either by simple observation or surgical removal of the osteochondral fragment. We studied the evolution of the lesion in 13 children and reviewed 92 hips reported in the literature. In our patients ten showed a tendency towards spontaneous healing, one required drilling + grafting to obtain fusion, and in two there was separation into the joint. These loose bodies were in the acetabular fossa and caused no symptoms. On reviewing the literature, we found only four cases of hips with loose bodies from osteochondritis dissecans. These were lying in the inferomedial capsule and were also asymptomatic. Treatment of osteochondritis dissecans after Legg-Calvé-Perthes’ disease should therefore be conservative unless the fragment interferes with the mechanics of the hip

Salter innominate osteotomy is an effective reconstructive procedure for the treatment of developmental dysplasia of the hip (DDH), but some children have a poor outcome at skeletal maturity. In order to investigate factors associated with an unfavourable outcome, we assessed the development of the contralateral hip. We retrospectively reviewed 46 patients who underwent a unilateral Salter osteotomy at between five and seven years of age, with a mean follow-up of 10.3 years (7 to 20). The patients were divided into three groups according to the centre–edge angle (CEA) of the contralateral hip at skeletal maturity: normal (> 25°, 22 patients), borderline (20° to 25°, 17 patients) and dysplastic (<  20°, 7 patients). The CEA of the affected hip was measured pre-operatively, at eight to nine years of age, at 11 to 12 years of age and at skeletal maturity. The CEA of the affected hip was significantly smaller in the borderline and dysplastic groups at 11 and 12 years of age (p = 0.012) and at skeletal maturity (p = 0.017) than in the normal group. Severin group III was seen in two (11.8%) and four hips (57.1%) of the borderline and dysplastic groups, respectively (p < 0.001).

Limited individual development of the acetabulum was associated with an unfavourable outcome following Salter osteotomy.

Cite this article: Bone Joint J 2014;96-B:1419–23.