13 year evaluation of highly cross-linked polyethylene articulating with either 28mm or 36mm femoral heads using radiostereometric analysis and computerized tomography

Abstract Background The objective of this 13 year prospective evaluation of HXLPE was to (1) assess the long-term wear of HXLPE articulating with 2 femoral head sizes using radiostereometric analysis (RSA), and to (2) determine if osteolysis is a concern with this material through the use of plain radiographs and computerized tomography (CT). Methods All patients received a Longevity® HXLPE liner with tantalum beads and either a 28mm or 36mm femoral head. Twelve patients (6 in each head size group) agreed to return for 13 year RSA, plain radiograph, and CT follow-up. The 1 year and 13 year plain radiographs as well as the CT scans were analyzed for the presence of osteolysis. Results The 13 year mean ± standard error steady state wear was 0.05 ± 0.02mm with no significant increase over time or between the 2 head size groups. Two patients’ CT scans showed radiolucent regions in the acetabulum of 4.51cm3 and 11.25cm3 , respectively. In one patient, this area corresponded to a partially healed degenerative cyst treated with autograft during surgery. The second patient had an acetabular protrusio treated with autograft and the CT scan revealed areas of remodeling of this graft. One patient’s 13 year plain radiographs showed evidence of cup loosening, and linear radiolucencies in zones 2 and 3. Conclusion There was no evidence of significant wear over time using RSA. The CT scans did not show evidence of osteolysis due to wear particles. These results suggest that this material has reduced wear compared to conventional polyethylene, irrespective of head size.