The role of the acetabulum in Perthes disease.

The purpose of this study is to evaluate the changes in the shape of acetabulum from the onset of the disease to the skeletal maturity in Legg-Calvé-Perthes disease. The study population consisted of 243 patients with unilateral involvement who had reached skeletal maturity at last follow-up. All hips were treated by containment methods (which included bed rest and traction in abduction, Petri cast, brace, varus osteotomy, Salter osteotomy, and shelf acetabuloplasty). Necrosis of the femoral head was estimated according to the lateral pillar classification and late results according to the Stulberg classification. Changes in the shape of the acetabulum were divided into 3 groups: type I-normal, concave lateral acetabulum margin; type II-flat, horizontal lateral acetabulum margin; and type III-convex, sloping acetabular margin. Roentgenograms performed during the fragmentation stage revealed type I changes in 78 (32.1%) hips, type II in 136 (55.7%), and type III in 29 (12.2%). At the last follow-up, there were type I changes in 124 (51.2%) hips, type II in 81 (33.5%), and type III in 38 (15.3%). The statistical analysis revealed no significant statistical difference between the age at the onset and gender with regard to acetabular changes. There was significant statistical correlation between the lateral pillar classification, subluxation of the femoral head, the range of hip abduction, and the Stulberg classification with regard to acetabular changes. A type III was statistically associated with lateral pillar classification group C, major subluxation of the femoral head, limited hip abduction, and in Stulberg group 3, 4, or 5. Only surgical methods of treatment improved the acetabular shape at the last follow-up (P<0.05). In our opinion, the lateral acetabulum shape plays a very important role during the remodeling of the deformed proximal femoral epiphysis.