Does Acetabulum Remodel Following Varus Derotation Osteotomy for Perthes' Disease?

Objective We investigated the effect of disease stage, patient's age and final contour of femoral head on acetabulum contour following varus derotation osteotomy of proximal femur (VDRO) in unilateral Perthes's disease. Methods The study is a retrospective analysis of case records of 23 children aged ≥6 years with unilateral Perthes' disease who underwent primary VDRO procedure for containment. Acetabular index (AI) and center edge angle (CEA) were calculated bilaterally in preoperative and follow-up radiographs and compared statistically. Results There were 15 boys and 8 girls. Six hips were in Ib, 8 in IIa and 9 in IIb modified Waldenström stage while undergoing VDRO. The mean age at surgical intervention was 8.7 years. The mean follow-up duration was 3.5 years. All femoral heads were healed at final follow-up and the final Stulberg grades were I = 3, II = 8, III = 7, IV = 5. A significant acetabular dysplasia on the affected side was present preoperatively. At follow-up, the patients operated had significantly raised AI and reduced CEA. There was no significant acetabular remodeling of the affected hips at follow-up even in children operated at younger age (< 8 years) or early stages (stage Ib or IIa). The acetabulum remodeling did not correspond to the final Stulberg grade as well. Conclusion Acetabulum was found involved in early stages of Perthes' disease. Varus derotation femoral osteotomy for the diseased hip showed no significant improvement in acetabular dysplasia even when operated in early disease stages or younger age group. Residual acetabular changes were also noted even with favorable Stulberg grades.