To evaluate the results of cementless cup fixation in primary total hip arthroplasties (THAs) involving removal of acetabular subchondral bone and medial placement of a cementless cup.

Forty-three primary THAs, in which the subchondral bone of acetabulum was removed and the cementless cup was placed medially, were performed between November 1997 and August 2000, and followed for more than 2 years. Clinical results were assessed using the Harris hip score and radiological results were analyzed.

The mean Harris hip score improved from 56 points preoperatively to 95 points postoperatively. Postoperatively, the hip center migrated 13 mm medially and the average superolateral coverage of the cup with bone was 98.3 percent. Union of the perforated or fractured medial wall of acetabulum took 3.1 months (3-4 months) on average. During follow-up, no osteolysis or loosening of acetabular componentsn was observed and no revision was required.

The removal of subchondral bone of the acetabulum and medial fixation of the cementless acetabular component provided predictable and durable cup fixation.