OBJECTIVETo summarize the surgical technique and the clinical results of small acetabular components combined with medial protrusio technique in primary total hip arthroplasty (THA) for the treatment of Crowe type IV congenital hip dislocation (CHD).

METHODSFrom January 2000 to December 2005, total 14 patients (16 hips) of Crowe type IV CHD underwent cementless THA (12 unilateral, 2 bilateral) with this new technique. There were 2 males and 12 females with an average age of 49 years (range, 38 to 75 years). The indications for surgery was severe hip pain and leg length discrepancy with difficulty in walking and activating. Cup design: Duraloc (Depuy, Warsaw, USA) in 10 hips, Pressfit S II (LINK, Germany) in 6 hips. The outside diameter of the cup was 42 to 44 mm; and the thickness of the polyethylene liner was 6 to 7 mm. Total hip replacement were performed with the medial protrusion technique to stabilize the fit of a hemispherical metal cup in the acetabulum. The hip functions were evaluated by Harris hip score. The muscle strength of the gluteus medius and gait were respectively evaluated in accordance with the standards of five and four classes.

RESULTSThe X-ray showed that the average superolateral bone coverage in these 16 hips (none of which had bone graft) was more than 98 percent. The cup was an average of (5.8 +/- 1.2) mm medial and (6.2 +/- 1.7) mm superior to the Ranawat triangle. The follow-up period ranged from 3 to 9 years. The Harris hip score improved from 25 to 32 preoperatively to 90 to 98 1 year postoperatively. X-ray showed that perforated area of the medial acetabulum were repaired with healed bone mud 4 to 8 months after operation. The rate of linear wear of the polyethylene liner averaged (0.10 +/- 0.03) mm each year. Until now, no aseptic loosening or osteolysis was identified around the acetabulum components, no acetabular components were revised for loosening or other reasons.

CONCLUSIONSmall acetabular components combined with medial protrusio technique is a simple, reliable and flexible surgical technique. Early and mid-term result in total hip arthroplasty with this technique for the treatment of Crowe type IV CHD is satisfactory.