Chiari innominate osteotomy in adults. Technique, indications and contra-indications.

The results are reported of 44 consecutive Chiari innominate osteotomies performed on 39 adult patients aged between 18 and 55 years for symptoms arising from disproportion between the acetabulum and the femoral head. Predisposing causes included congenital dysplasia of the acetabulum, congenital subluxation of the hip, and Perthes' disease. Follow-up averaged 5 years 2 months. Four pre-operative categories of dysplasia and degeneration were recognised. The analysis of the results from each category made possible the recognition of clinical and radiological features likely to provide a satisfactory result. Of 32 cases now considered to have been selected appropriately, 29 (90%) achieved a significant and apparently lasting improvement. In the other 12 cases there were 9 failures--an unacceptable proportion. The features predisposing to these poor results are discussed. The operation is not difficult. It is safe, and is less demanding than the complex alternative "double", "triple" and "dial" osteotomies. In successful cases there is reduction in symptoms and in limp, and improvement of radiological appearances beginning six months after surgery and progressing to a maximum recovery two to three years later.