Survival in the Third Decade of Uncemented Total Hip Arthroplasty With Small-Diameter Metal-on-Metal Versus Ceramic-on-Conventional Polyethylene Bearings

Background This study aimed to assess the long-term revision and mortality rates after uncemented total hip arthroplasty with small-diameter metal-on-metal (SD-MoM) and ceramic-on-conventional polyethylene (CoPE) bearings over 20-24 years of follow-up. Methods This retrospective, single-center study included 622 total hip arthroplasty (1998-2001) with 3 stem (BEO, CLS Spotorno, Alloclassic) and 2 bearing types (SD-MoM: n=458; CoPE: n=164). Kaplan-Meier survival analysis assessed implant revision and patient mortality. Revision was defined as any surgical intervention involving the exchange, removal, or addition of implant components. Results Revision rates did not differ significantly between SD-MoM and CoPE bearings ( P = .77). SD-MoM bearings showed a steady increase in revisions, while CoPE bearings experienced a marked rise after 10 years, surpassing SD-MoM rates. Mortality was significantly lower in the SD-MoM group (19.9% vs 48.9% for CoPE at 20 years, P < .0001). No significant differences in revision rates were observed between the Alloclassic, CLS Spotorno stem and/or BEO stems. Conclusions While SD-MoM bearings showed favorable long-term revision rates compared to CoPE, recent data suggest conflicting results. No increased mortality could be observed for SD-MoM, the even lower mortality in this group was likely due to the younger age of these patients. While SD-MoM seem to compare favorably to large diameter MoM regarding long-term outcomes, need for follow-up, including monitoring of cobalt and chromium blood levels, remains.