INTRODUCTION: The aim of this study was to calculate the wear rate of highly cross-linked polyethylene (HXLPE) and investigate long-term clinical and radiographic outcomes related to two femoral stem designs, the distal-cylindrical (DC) and distal-taper (DT) stems. MATERIALS AND METHODS: Outcomes for the DC and DT stems were evaluated in 110 patients, who underwent total hip arthroplasty using an HXLPE socket, over a 5-year follow-up period. There were 56 hips (53 patients) in the DC group and 60 hips (57 patients) in the DT group. Clinical outcomes were measured using the Japanese Orthopaedic Association (JOA) score and radiographic changes. Polyethylene wear rate was calculated using a computer software. RESULTS: The mean follow-up period was 135.7 and 124.0 months for the DC and DT groups, respectively. Both stem designs improved hip function. On radiographic assessment, osteolysis around the tip of the stem was more frequent in the DC than in the DT group. Three cases of aseptic loosening of the stem were identified in the DC group, and no cases were identified in the DT group. The 10-year stem survival, using aseptic loosening as the primary endpoint, was 94.1% and 100% for the DC and DT groups, respectively (p = 0.06). The polyethylene wear rate was comparable for both stem groups. CONCLUSION: Better clinical outcomes were obtained with the DT stem than with the DC stem regardless of the equivalent polyethylene wear rate for the two designs. The DC shape of the stem may increase the risk of aseptic loosening.
INTRODUCTION: The aim of this study was to calculate the wear rate of highly cross-linked polyethylene (HXLPE) and investigate long-term clinical and radiographic outcomes related to two femoral stem designs, the distal-cylindrical (DC) and distal-taper (DT) stems. MATERIALS AND METHODS: Outcomes for the DC and DT stems were evaluated in 110 patients, who underwent total hip arthroplasty using an HXLPE socket, over a 5-year follow-up period. There were 56 hips (53 patients) in the DC group and 60 hips (57 patients) in the DT group. Clinical outcomes were measured using the Japanese Orthopaedic Association (JOA) score and radiographic changes. Polyethylene wear rate was calculated using a computer software. RESULTS: The mean follow-up period was 135.7 and 124.0 months for the DC and DT groups, respectively. Both stem designs improved hip function. On radiographic assessment, osteolysis around the tip of the stem was more frequent in the DC than in the DT group. Three cases of aseptic loosening of the stem were identified in the DC group, and no cases were identified in the DT group. The 10-year stem survival, using aseptic loosening as the primary endpoint, was 94.1% and 100% for the DC and DT groups, respectively (p = 0.06). The polyethylene wear rate was comparable for both stem groups. CONCLUSION: Better clinical outcomes were obtained with the DT stem than with the DC stem regardless of the equivalent polyethylene wear rate for the two designs. The DC shape of the stem may increase the risk of aseptic loosening.