Dual mobility bearings withstand loading from steeper cup-inclinations without substantial wear.

Abstract

Steep cup abduction angles with adverse joint loading may increase traditional polyethylene bearing wear in total hip arthroplasties. However, there have been few reports evaluating the effect of cup inclination on the wear of dual-mobility devices. In a hip joint simulation, we compared the short-term wear of two-sizes of modular highly cross-linked dual-mobility bearings (28 mm femoral head diameter/42 mm polyethylene insert outer diameter/54 mm acetabular shell diameter; 22.2 mm femoral head diameter/36 mm polyethylene insert outer diameter/48 mm acetabular shell diameter) at 50 and 65° of cup inclination with modular 28 mm femoral head on 54 mm cup diameter metal-on-highly cross-linked polyethylene bearings. Increasing inclination from 50-65° had no changes in volumetric wear of 28/42/54 mm (mean, 1.7 vs. 1.2 mm3 /million cycles, respectively; p = 0.50) and 22.2/36/48 mm (mean, 1.7 vs. 1.2 mm3/million cycles, respectively; p = 0.48) dual mobility bearings. At 65°, 22.2/36/48 mm dual-mobility bearings had lower volumetric loss (mean, 2.2 vs. 6.3 mm(3) ; p = 0.03) and wear rates (mean, 1.2 vs. 2.7 mm3/million cycles; p = 0.02) compared to metal-on-highly cross-linked polyethylene bearings. Modern-generation dual-mobility designs with highly cross-linked polyethylenes may potentially withstand edge-loading from steeper cup-inclinations without substantial decreases in wear.