Results of Primary Total Hip Arthroplasty Using 36 mm Femoral Heads on 1st Generation Highly Cross Linked Polyethylene in Patients 50 Years and Less with Minimum Five Year Follow-up

PURPOSE We evaluated the clinical and radiographic midterm results of primary total hip arthroplasty (THA) using a 36 mm diameter femoral head on 1st generation highly cross-linked polyethylene (HXLPE) in patients 50 years and less with minimum five year follow-up. MATERIALS AND METHODS We retrospectively reviewed 31 patients (41 hips) aged 50 years and less underwent primary THA with a 36 mm diameter femoral head on HXLPE between 2004 and 2010. Clinical follow-ups included specific measurements like modified Harris hip scores (HHS) and Merle d'Aubigne and Postel score. For radiologic evaluations, together with position of acetabular cup at six weeks later of postoperation, we separately calculated the penentrations of femoral head into polyethylene liners during postoperation and one year later check-ups, and during one year later check-ups and final check-ups. RESULTS There were no major complications except for one case of dislocation. Average modified HHS at final follow-up was 88 (81-98), and Merle d'Aubigne and Postel scores were more than 15. Mean acetabular cup inclination and anteversion were 45.81°(36.33°-54.91°) and 13.26°(6.72°-27.71°), respectively. Average femoral head penetration of steady-state wear rate determined using radiographs taken at one-year postoperatively and at latest follow-up was 0.042±0.001 mm/year. CONCLUSION Based on minimum 5 years clinical results, we think 36 mm metal head coupling with HXLPE as the good alternate articulation surface when planning THA for patients aged 50 years and less.