We wanted to solve the problem of acetabular dysplasia with a cementless total hip endoprothesis by using a smaller acetabular cup in order to fit the size of the dysplastic acetabulum without using any additional bone transplantation for superstructure of the acetabulum. By using this type of acetabular reconstruction we can preliminarily conclude that the bone superstructure of the acetabulum can be avoided and that problems may occur if remodelation of the bone transplant has failed. Irregular biomechanical bending in the supraacetabular region can also be avoided. Uncured developmental dysplasia of the hip joint (DDH) is a huge problem to solve in elderly patients. DDH can be expressed in several forms according to stage, i.e., in young and elderly patients we can find different consequences, from slight to moderate supraacetabular dysplasia combined with anterior dysplasia, valgus and anteversion of the proximal femur, to high hip luxation. In efforts to find a better way to solve slight and moderate supraacetabular dysplasia (in some cases combined with high luxation), we have tried to use a smaller acetabular cup that will fit the dysplastic acetabulum, combined with a higher hip centre, dysplastic polyethylene, and a longer femoral neck to avoid leg length discrepancy and weakness of the gluteal musculature. From January 1999 to January 2000 we performed the above-mentioned type of operation in 33 patients (25 females, 8 males) with dysplastic coxarthrosis of the hip. Age range was from 32 to 63 years. In all cases we performed the application of a Zimmer or Biomet smaller acetabular cementless cup after reaming the acetabulum near the internal lamina of the iliac bone. Good primary fixation of the acetabulum was achieved in all of the cases. Supraacetabular reconstruction was not used. In some cases where the dysplasia was very expressive, we left the acetabular cup uncovered for about 0.5 cm. In the postoperative period we advised the patient to load the operated leg over two crutches without full weight bearing for approximately six weeks. After that time period and according to clinical and radiographic findings, we prescribed walking with one crutch, and walking without crutches four months later. The follow-up period is short but preliminary results of our study are satisfactory. There were no early postoperative complications. Incorporation of bone was good in the acetabular cups measured with radiographs and in some cases with Tc99m. In some cases where we left part of the cup uncovered, there was supraacetabular formation of new bone after six months.
