We studied the pathogenesis, incidence and consequences of avascular necrosis in 184 children treated for congenital dislocation of the hip. Of 210 hips, 99 (47%) had some evidence of avascular necrosis (total 81, partial 18). The incidence was not influenced by the age at reduction, the duration of traction or the use of adductor tenotomy. Patients treated by closed reduction without preliminary traction did not have a higher incidence of avascular necrosis. At long-term clinical and radiological review of 81 hips, early avascular necrosis significantly increased the chance of a poor outcome but did not predispose to acetabular dysplasia. If review includes minor forms of avascular necrosis, then this condition is common after closed reduction. Its presence is an important determinant of long-term radiological and clinical outcome.

We report four children with sternomastoid contracture combined with torticolis secondary to congenital vertebral anomalies. Two had features of Klippel-Feil syndrome and a proximal release of the contracted sternomastoid produced good cosmetic correction initially. Progression of the deformity occurred subsequently without recurrence of sternomastoid contracture. One child had such mild deformity that it was merely observed. The fourth child was born with torticollis without sternomastoid tightness and a vertebral anomaly was later recognised. He slowly developed a sternomastoid contracture and his condition was considerably improved by sternomastoid release. This combination of causes of torticollis has not, as far as we know, been previously reported. The clinician should be aware of it and should also realise that radiographs of the very immature spine may not disclose the bony anomalies.

We investigated the reproducibility of the various radiological methods of assessment of hip dysplasia by making 474 assessments of hips and quantifying the inter-observer and intra-observer variation. There was a wide range of variability between the readings made by different observers and by one observer on two occasions. A measurement of acetabular index has to be given a range of +/- 6 degrees in order to be 95% confident of including the true measurement. We found the most helpful measurements to be the acetabular index, up to the age of eight years; the centre-edge angle, over the age of five years; and Smith's c/b ratio and neck-shaft angle. We feel, however, that the change in value over a series of radiographs in the same child is much more valuable. Single readings of all the radiological measurements investigated in this study were unreliable.

We have reviewed the serial radiographs of 63 hips in 53 children treated by closed reduction for congenital dislocation with a view to finding a radiological measurement which can predict subsequent acetabular development. All had been followed for more than seven years, and at latest review, 34 hips were dysplastic. Failure to obtain concentric reduction or its loss by migration of the femoral head within one year of reduction were the best predictors of persisting acetabular dysplasia and were best quantitated by the h/b ratio (Smith et al. 1968). The acetabular index at reduction or its decrease in the first year were not reliable predictors. Late treatment was less likely to lead to normal acetabular development, but avascular necrosis did not appear to have a significant influence. The average age at which the acetabulum stopped developing was five years, but ranged from 17 months to eight years. The failure of a dysplastic acetabulum to improve in each annual radiograph after closed reduction should lead to consideration of operation on the acetabulum.