LONG TERM SURVIVAL AND PELVIC REMODELLING AFTER THE CHIARI OSTEOTOMY

Abstract

Over the last 30 years 215 Chiari medial displacement pelvic osteotomies have been carried out, principally for dysplasia of the hip, presenting after adolescence or following previous surgical treatment. Substantial pain relief was achieved initially in 93 per cent of the patients, particularly when the osteotomy was undertaken before stiffness and arthritic change had developed. Survivor-ship analysis, using revision of the hip as the index of failure, revealed that there was a progressive deterioration of the result with time, but that almost 4 out of every 5 hip joints were functioning acceptably at 25–30 years.

The radiographic characteristics of 110 osteotomies in 89 patients were evaluated 5-30 (mean 18) years after surgery which was performed at the age of 15.9+-9.5 years. Revision was significantly (p < 0.05) more likely in those patients operated upon after the age of 25 years. The centre-edge (CE) angle increased from 2.5+-13.9 degrees preoperatively to 41.8+- 15.0 degrees immediately after operation; the increase in the CE angle was maintained at long-term review (39.5+-16.5 degrees), and even with severe dysplasia (CE angle less than zero) a substantial improvement in femoral head cover was achieved, usually by the medial shift of the lower pelvic fragment. However, the femoral head was not invariably medialised by the osteotomy and lateral movement of the ilium was noted when the preoperative position of the joint was relatively medial, or when the hip was arthritic. In the longer term pelvic remodelling did not reverse the medialisation produced by the osteotomy, and femoral head cover was maintained. The osteotomy is at its most effective between the ages of 10–35 years and is not recommended above the age of 40 years.