To evaluate the results of the acetabular circumferential medial wall osteotomy in obtaining secure fixation of cementless hemispherical acetabular cup to the hypoplastic acetabulum.

Seventy-nine THAs with a circumferential acetabular medial wall osteotomy in the dysplastic acetabulum performed between 1987 to 1997 and followed up for more than 6 years were assessed. The indication of this technique was acetabular coverage that could not achieve more than 70% after cup fixation. In all cases, a cementless hemispherical acetabular cup was fixed in the true acetabulum. Additional procedures included soft tissue releases in 23 hips, a derotational femoral osteotomy in 10 hips, a structural bone graft in 7 hips and femoral shortening in 8 hips. Both clinical and radiographic parameters were evaluated.

The Harris hip scores were improved from 68.4 to 92.2 postoperatively. Radiographic analysis revealed no aseptic loosening or radioluacent line, and showed stable bony fixation at the true acetabulum in all cases. 7 hips showed acetabular osteolysis. Two acetabular components were revised due to dissociation of the polyethylene liner and 4 polyethylene liners were exchanged because of severe wear or osteolysis.

The circumferential acetabular medial wall osteotomy can provide appropriate positioning, sufficient coverage of the acetabular cup with a preservation of the medial wall thickness in cementless THA without additional bone grafting in the dysplastic acetabulum.