Aims

Slipped upper femoral epiphysis (SUFE) has well documented biochemical and mechanical risk factors. Femoral and acetabular morphologies seem to be equally important. Acetabular retroversion has a low prevalence in asymptomatic adults. Hips with dysplasia, osteoarthritis, and Perthes’ disease, however, have higher rates, ranging from 18% to 48%. The aim of our study was to assess the prevalence of acetabular retroversion in patients presenting with SUFE using both validated radiological signs and tomographical measurements.

Aims. The purpose of this study was to calculate the dislocation rate following open or closed reduction for developmental dysplasia of the hip (DDH) in our unit. In addition we evaluated the posterior neck line as a method of determining hip relocation and assessed the morphology of the dysplastic acetabulum on single slice CT scan. Method. We retrospectively assessed all patients operated on for either open or closed reduction for DDH between August 2007 and August 2009 and evaluated their notes, CT scans and radiographs. The immediate post-operative dislocation rate was calculated, as was the subsequent re-dislocation rate and late subluxation rate. The acetabular morphology was assessed to determine whether the acetabulae were “S” shaped or “C” shaped. A novel method for confirming hip reduction was also appraised. Results. Seventy-five hips were operated on during the study period. The immediate post-operative dislocation rate was 9.3%. There were no subsequent dislocations in any of the patients in whom CT scans had confirmed adequate initial reduction. Two patients went on to develop late subluxation. 98.6% of dysplastic acetabulae displayed an S shaped acetabulum and 1 hip had a virtually flat acetabulum. The posterior neck line test for dislocation had a 85.7% sensitivity and 96.9% specificity. Conclusions. Immediate post-operative CT scan of the hip is a useful investigation following reduction of the hip for DDH. If it can be established that the hip is reduced on the scan it is unlikely to re-dislocate. The S shape of the acetabulum in DDH is consistently present and is a marker of the dysplastic posterior acetabular wall. The posterior neck line is a reliable measure of hip reduction

We analysed the incidence of avascular necrosis in 101 hips of 90 infants with congenital dislocation treated with the Pavlik harness and followed up for more than one year. Using ultrasonography in the flexed-abducted position the hips were classified as type A when the femoral head was displaced posteriorly, but within the socket and making contact with the posterior inner wall of the acetabulum; type B when it was in contact with the posterior margin of the acetabulum, with its centre at this level or anterior to it; and type C when it was displaced out of the socket, with its centre posterior to the posterior rim of the acetabulum. Eighty-seven hips were reduced by the harness (86%), and seven of these developed avascular necrosis (8%). All 69 hips with type-A dislocation were reduced, and only one (1.4%) showed slight avascular necrosis. Eighteen (78.3%) of 23 hips with type-B dislocation were reduced, and six developed avascular necrosis (33.3%). In one hip, the femoral head was severely damaged. None of the nine hips with type-C dislocation was reduced in the harness. We conclude that the Pavlik harness is indicated for type-A, but not for type-B or type-C dislocations

We carried out a morphometric analysis of the acetabulum following Dega osteotomy in patients with cerebral palsy using three-dimensional CT. We assessed 17 acetabula in 12 patients with instability of the hip. A Dega osteotomy and varus derotation femoral osteotomy were performed in all 17 hips. Three-dimensional CT scans were taken before and approximately one year after operation. Acetabular cover was evaluated using anterosuperior, superolateral and posterosuperior acetabular indices, and the change in the acetabular volume was calculated. Inter- and intra-observer reliability was assessed using the intraclass correlation coefficient. After the osteotomy, the anterosuperior, superolateral and posterosuperior cover had improved significantly towards the value seen in a control group. The mean acetabular volume increased by 68%.

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.