FIXATION OF ULTRAHIGH-MOLECULAR-WEIGHT POLYETHYLENE LINERS TO METAL-BACKED ACETABULAR CUPS

Locking mechanisms and metal-liner interface surfaces of six modular a cetabular systems were evaluated to determine their effect on micromot ion and backside wear of the polyethylene liner. Rotational and axial motion between the metal shell and polyethylene liner was measured in the Duraloc (DePuy, Warsaw, IN), Harris-Galante (Zimmer, Warsaw, IN), Impact (Biomet, Warsaw, IN), Lip Loc (Biomet), Precision Osteoloc (How medica, Rutherford, NJ), and Reflection (Smith & Nephew Orthopaedics, Memphis, TN) designs at the start of each test, and at 1 million, 5 mi llion, and 10 million cycles. At 10 million cycles, the Lip Loc and Re flection cups had significantly lower rim micromotion than the Duraloc and Harris-Galante cups (F < .0010). The Impact, Precision Osteoloc, and Reflection cups had significantly lower rim subsidence than the Ha rris-Galante cup (F < .0025). The Harris-Galante cup had significantly greater rotational micromotion than the Lip Loc cup (F < .0074), and had significantly greater interface slippage than the Impact and Refle ction cups (F < .0070). The Lip Loc produced significantly lower dome micromotion than the Harris-Galante (F < .0300). The Lip Loc and Refle ction cups had significantly less backside wear than the Duraloc and H arris-Galante cups (P < .0001), the Impact cup (P < .0243), and the Pr ecision Osteoloc (P < .0027) cup.