Chiari osteotomy in the adult: a long-term follow-up study.

For almost 20 years the Chiari pelvic displacement osteotomy has been used as a method of providing cover to the femoral head in cases of acetabular dysplasia. The osteotomy is one of a number of procedures that have been used in an attempt to prevent the early development of secondary osteo-arthritis and the need for total hip replacement. More recently, the operation has been undertaken in cases where there is already some arthritic change. This long-term review of 18 Chiari operations shows that the procedure was successful in cases of acetabular dysplasia where there was minimal subluxation of the femoral head (i.e. with Shenton's line still intact). In more advanced cases where there was significant subluxation (i.e. with Shenton's line broken by more than 1 mm) and even early arthritic changes, the results were poor. It is concluded that the operation may be of value as an almost 'prophylactic' procedure but that it is of no value as a so-called 'salvage' procedure.