Acetabular polyethylene wear and acetabular inclination and femoral offset.

UNLABELLED: Restoration of femoral offset and acetabular inclination may have an effect on polyethylene (PE) wear in THA. We therefore assessed the effect of femoral offset and acetabular inclination (angle) on acetabular conventional (not highly cross-linked) PE wear in uncemented THA. We prospectively followed 43 uncemented THAs for a minimum of 49 months (mean, 64 months; range, 49-88 months). Radiographs were assessed for femoral offset, acetabular inclination, and conventional PE wear. The mean (+/- standard deviation) linear wear rate in all THAs was 0.14 mm/year (+/- 0.01 mm/year) and the mean volumetric wear rate was 53.1 mm(3)/year (+/- 5.5 mm(3)/year). In THAs with an acetabular angle less than 45 degrees , the mean wear was 0.12 mm/year (+/- 0.01 mm/year) compared with 0.18 mm/year (+/- 0.02 mm/year) in those with a reconstructed acetabular angle greater than 45 degrees . Reproduction of a reconstructed femoral offset to within 5 mm of the native femoral offset was associated with a reduction in conventional PE wear (0.12 mm/year versus 0.16 mm/year). Careful placement of the acetabular component to ensure an acetabular angle less than 45 degrees in the reconstructed hip allows for reduced conventional PE wear. LEVEL OF EVIDENCE: Level II, prospective study. See Guidelines for Authors for a complete description of levels of evidence.