Chiari pelvic osteotomy in Perthes disease.

A retrospective study of 17 Chiari osteotomies performed on patients with Perthes disease who were followed until the end of growth is presented. The average age at operation was 8 years 9 months. Catterall grading was mainly group IV. Chiari osteotomy provided satisfactory femoral head coverage with a decreased acetabular index and a 19.6 degrees improvement of the Wiberg angle. Good femoral coverage was related to age at operation and the site of the osteotomy on the upper rim of the acetabulum. The postoperative result was less successful on younger patients or when the osteotomy was performed higher. At follow-up, the results of femoral head sphericity studied by Mose measurements were favorable under Catterall grading.