Medium-term results of the ABG total hip arthroplasty in young patients.

A total of 66 patients (71 hips) <65 years old (average age, 55.4 years; range, 26-65 years) received a proximally hydroxyapatite-coated femoral prosthesis with a hemispheric metal-backed, hydroxyapatite-coated acetabular cup (ABG hip, Howmedica International, Staines, UK), with an average follow-up of 4.8 years (range, 2-7 years). All operations were performed by 1 surgeon in a district general hospital. The average preoperative Harris hip score and Merle d'Aubigné score were 59.8 and 9.6, which rose to 92.7 and 16.3 at the longest follow-up. Most patients were satisfied with the outcome, with only 2 patients complaining of intermittent thigh pain. Survivorship analysis predicted a survival rate of 96.87% at 7 years. There were 2 revisions, one to reposition an acetabular cup and one for an undersized femoral component. Radiographic changes were consistent with bone remodeling. There were no radiolucencies around the acetabular cup, but we noted eccentric polyethylene wear in 37 (60%) inserts ranging from 0.4 to 4 mm (annual wear average, 0.25 mm/y; range, 0.063-0.76 mm/y). There were no loose femoral stems. Osseointegration was achieved in all cases, with only 1 case developing endosteal cavitation in Gruen zone 2. Cancellous densification was found to be mainly in zones 2 and 6 (67.2% and 55.7%), extending distally in zones 3 and 5 (52.4% and 50.8%). Hypertrophy of the femoral shaft was less prominent and was noted mostly distally, in zones 3, 4, and 5 (11.4%, 18.3%, and 18.3%), extending proximally in zones 2 and 6 (8.1% and 13.1%). The ABG hip can achieve excellent results in the medium term, but polyethylene wear of the acetabular insert should be noted with concern.