Wear rates of larger-diameter cross-linked polyethylene at 5 to 13 years: does liner thickness or component position matter?
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BACKGROUND: Cross-linked polyethylene (XLPE) has demonstrated significantly reduced wear and osteolysis into the second decade for total hip arthroplasty. There is a relative paucity of data with >/=36-mm bearings. Issues include potential effects of reduced liner thickness and component position on wear, osteolysis, and mechanical failure of the bearing. METHODS: Radiographs of 48 primary total hip arthroplasties with >/=36-mm modular XLPE bearings were analyzed at a minimum 5 years postoperative on serial radiographs using a validated, edge-detection-based algorithm. Subgroups were examined to assess the effect of bearing diameter, liner thickness, acetabular abduction angle, and acetabular anteversion on XLPE wear. RESULTS: There was no significant difference in volumetric wear when subgroups were stratified by component factors: liner thickness (<6.5 mm vs >/=6.5 mm) 40.69 mm(3)/y vs 24.47 mm(3)/y, respectively (P = .315); acetabular component abduction angle (<45 degrees vs >/=45 degrees ): 38.68 mm(3)/y vs 27.8 mm(3)/y, respectively (P = .522); acetabular anteversion (<20 degrees vs >/=20 degrees ): 41.32 mm(3)/y vs 31.79 mm(3)/y, respectively (P = .521). There were no dislocations, mechanical failures, or revisions. There were 7 hips with volumetric wear rates >/=80 mm(3)/y; 1 had possible osteolysis. CONCLUSION: Larger-diameter XLPE wear was not measurably affected by liner thickness, acetabular abduction angle, or acetabular anteversion. However, there is a trend for increasing volumetric wear with increasing bearing size. Wear outliers do occur, and continued follow-up of larger-diameter XLPE bearings is warranted.
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