[Prophylactic osteotomy of pelvis in dysplastic acetabulum.]

Acetabular dysplasia and anatomical changes of pelvis accompanied with gracility of iliac bone pose a problem for a reliable fixation of acetabular component. In extreme cases the bone stock is not sufficient to accommodate the smallest size of the cup. Sometimes even reaming of the bed down to lamina interna is not sufficient for an adequate covering of the implant. Consequently, weakening of the bottom of acetabulum may be not only one of the causes of the failure of the implant but it makes difficult also the following revision surgeries. Therefore in acetabular dysplasia the authors recommend acetabuloplasty of the bottom of acetabulum preserving its original thickness including inner cortex. They recommend to perform osteotomy of the full thickness of the medial wall of acetabulum and move the massive bone graft created in this way farther into pelvis. At the same time they take care to preserve blood supply of the bone graft by retaining corticoperiostal bridge by means of osteoclasia. The suggested procedure allows full coverage of the implant by iliac bone and at the same time preserves a firm support of acetabular fossa. The original thickness of the medial wall of acetabulum is considered by authors as a significant antimigration barrier. In the period 1991 -1994 the authors used this method at Ist Orthopaedic Clinic of 1st Medical Faculty, Charles University in Prague in total in 16 patients. In all of them after 6 months the bone graft was fully absorbed. Remodelling of the bone graft occurred 1 to 2 years after the surgery and after that the thickness of the graft remained the same. Neither any change of the structure nor reduction of the thickness of the graft was found between 3rd and 4th year after the surgery. The nature of trabecular remodelling of the bone graft corresponds to the transfer of forces in loading the graft by acetabular cup. Key words: acetabuloplasty, osteotomy of the medial wall of acetabulum, osteotomy of pelvis, THR, acetabular dysplasia.