BACKSIDE WEAR IN RETRIEVED MODULAR AND NON-MODULAR UNCEMENTED ACETABULAR CUPS.

Abstract

Backside wear is generated at the non-articulating surfaces of modular acetabular cups. We compared the backside wear of retrieved liners from cementless non-modular and modular cups of first and second generation designs. We match paired for time in situ, patient age and weight, 9 retrieved Harris Galante type 1 liners, 9 Harris Galante type 2, 9 Trilogy, and 9 liners from a modern two-piece preassembled cup (Implex). The average time in situ was 2.5 years (1 to 7). The backside was divided in quadrants and each one examined under a 10x binocular loupe and rated with a score from 0 (absence of wear) to 3 (severe backside wear) for a total ranging from 0 to 12. Among 36 quadrants in the HG1 group there were 3 rated 1, 23 rated 2, and 10 rated 3. In the HG2 group, there was 1 quadrant rated 0, 16 rated 1, 14 rated 2, and 5 rated 3. In the Trilogy group, there were 6 quadrants rated 0, 27 rated 1, and 3 rated 2. In the Implex group, there were 15 quadrants rated 0, 21 rated 1. The average total backside wear score was 8.4; 7.3; 3.7; and 2.3 respectively. The HG cups demonstrated more severe backside wear than the Trilogy and Implex (HG1 vs Trilogy and HG1 vs Implex: p< 0.001; HG2 vs Trilogy and HG2 vs Implex: p< 0.02). There was a tendency towards less backside wear in the Implex cup when compared to the Trilogy (p=0.04). The difference between the HG1 and HG2 was not significant. Despite the limitations imposed by the small sample studied, the presence of multiple screw holes in the Harris-Galante retrievals, and sub-optimal matching for sex, height, and varied indication for revision, we detected significant reduction in the backside wear of modern modular and non-modular acetabular cups when compared to first generation modular designs.