"Thicker" polyethylene bearings are associated with higher failure rates in primary total knee arthroplasty

Abstract

"Thin" modular polyethylene bearings have previously been associated with failure from wear. This study examined the influence of polyethylene thickness on survivorship in primary total knee arthroplasty (TKA). Do "thinner" or "thicker" bearings fail more? Six thousand seventy primary TKAs with a single implant design were reviewed. The failure rate in knees with bearings 14 mm or less was 0.7%, whereas the failure rate of knees with bearings 16 mm or greater was 2.3% (P < .0001; hazard ratio, 3.2). No knee was revised for polyethylene wear. Thicker bearings did not directly cause failure, but factors that lead to the insertion of a thicker bearing such as a deeper tibial resection and ligament imbalance may contribute to the observed increased failure. The significant influence of this often-unrecognized surgical variable has not been previously reported and must be carefully considered during TKA.