Comparison of long-term cause of failure and survivorship of 427 metal-on-metal hip arthroplasties: resurfacing versus large head total hip arthroplasty.

Introduction Comparison of mid- to long-term cause of failure and survivorship of metal-on-metal (MoM) resurfacing hip arthroplasty (RHA) and large head total hip arthroplasty (THA) remains sparse. This study aimed to identify and compare the cause of failure and survivorship of MoM RHA and THA at a minimum ten year follow-up. Methods Four hundred twenty-seven MoM hip arthroplasties (286 THA and 141 RHA) were retrospectively analyzed at a mean follow-up of 13 ± three years. Causes of failure were reported as MoM specific (i.e., adverse reaction to metal debris (ARMD) and painful hip with ion elevation) or MoM non-specific (i.e., fracture, infection, and dislocation). Chromium (Cr) and cobalt (Co) ion levels and Co/Cr ratio were compared. Survivorship was compared according to the cause of failure with revision as the endpoint. Results The rate of ARMD was significantly higher in THA (OR = 2.9 [95%-CI: 1–7]; p = 0.02). No significant difference was detected in failure rate due to other causes between the two groups (p = 0.2–0.9). Ion levels and Co/Cr ratio were both significantly higher in THA (p < 0.01). Survivorship was significantly lower in THA compared to RHA at ten years [89% (95%-CI: 85%–91%) vs 96% (95%-CI: 91%–98%); p = 0.01] and 15 years [73% (95%-CI: 67%–78%) vs 83% (95%-CI: 73%–90%); p = 0.01]. Conclusion RHA survivorship was significantly higher at any time point. Failure rate due to ARMD was significantly higher in THA while no significant difference in other causes of failure was observed between the two groups. This result emphasizes the role of fretting corrosion at the head-neck junction (i.e., trunnionosis) with significantly higher ion levels and Co/Cr ratio dissociation in THA