EXTRAARTICULAR AUGMENTATION FOR RESIDUAL HIP-DYSPLASIA - RADIOLOGICALASSESSMENT AFTER CHIARI OSTEOTOMIES AND SHELF PROCEDURES

The Chiari osteotomy and various shelf procedures are used to augment the weight-bearing area in dysplastic acetabula. The new articular sur face derives by metaplasia from the acetabular rim and joint capsule, and is therefore of poorer quality than congruous hyaline cartilage. W e reviewed 32 patients after augmentation procedures, using convention al radiographs and three-dimensional reconstruction from CT scans. We showed that Chiari osteotomy and shelf procedures generally achieve le ss than complete cover, especially over the posterolateral quadrant of the femoral head. Our results suggest that alternative methods which reorientate the whole of the acetabulum are the treatment of choice. A ugmentation procedures remain as a salvage option when reorientation i s inappropriate or the original hyaline cartilage surface is absent, a s in subluxed joints with a secondary acetabulum. Computerised assessm ent is recommended before operation to assess existing cover and the p ossible extent of provision of new cover.