Very Large Diameter Polymer Acetabular Liners Show Promising Wear Simulator Results.

Abstract

Thinner and larger acetabular components are more stable and are useful for resurfacing. This study performed wear simulator tests of the largest polyurethane (PUR) and highly cross-linked polyethylene (XLPE) liners available. The results were compared with conventional polyethylene (ConvPE) to determine wear, survivorship, wear debris particles generated, and oxidative degradation. Two-piece acetabular components with a 4-mm poly liner, a 2-mm metal backing, and 1 mm of porous coating with an inner diameter of 51 mm were tested. Cobalt chromium (CoCr) and titanium nitride (TiN)-coated titanium- resurfacing femoral components were counter-face surfaces. Acetabular components were tested at 45° and 65° inclinations, with both 300 μm and an increase of 1 mm in radial clearance. After 30 million cycles, PUR had 56% (p < 0.001) less wear and cross-linked had 93% (p < 0.001) less wear than ConvPE. TiN-coated femoral implants had 23% less wear than CoCr when used with cross-linked polyethylene. Wear increased by 16% at 65° and by 19% when radial clearance increased with cross-linked polyethylene. Polymethylmethacrylate debris ultimately failed ConvPE, but not the cross-linked polyethylene or PUR. XLPE acetabular liners are compatible with >20 years of expected use in active patients.