Hydroxyapatite-coated stems with metaphyseal and diaphyseal press-fit. Eleven-year follow-up results.

We report the 11-year follow-up results of 52 unilateral primary hip arthroplasties performed with hydroxyapatite-coated stems. The femoral prosthesis used was a collarless titanium alloy implant, with proximal circumferential hydroxyapatite coating and increased distal thickness to fit the proximal diaphyseal region of the femur. Clinical evaluation was performed using the Merle d'Aubigné Hip Score. Anteroposterior and lateral radiographs were obtained and compared with previous postoperative films. Radiographic evaluation was carried out following Engh's criteria for uncemented implant fixation and using Livermore's method for measurement of polyethylene wear. At the end of the follow-up period, excellent and good clinical results were recorded in 40 arthroplasties (77%). The incidence of thigh pain at one year was 32.7%, but it decreased to 4.2% after the first post-operative year. The 11-year survival rate was 92.3%. Seven arthroplasties were revised because of aseptic loosening of the cup in one case, aseptic loosening of the stem, in one case, septic loosening of the stem in one case, periprosthetic fracture in two cases and polyethylene wear in three cases. Forty-two (87.5%) of the nonrevised stems met the criteria for radiographic osseointegration. Cortical hypertrophy was observed around the mid-part and tip of the stem in 22 patients of the series. This sign tends to be related to thigh pain (p < 0.1). Calcar osteolysis was present in 8 cases. There was only one case of distal femoral osteolysis. We found a strong and significant relationship between long-term wear rates and the occurrence of osteolysis (p < 0.001). We concluded that thigh pain is in relation to the distal diameter of the stems and significantly decreases after the first postoperative year. There was a low incidence of osteolysis in our series in comparison with other series of noncemented implants with 32-mm femoral heads and with similar follow-up.