Are Metal Ion Levels Elevated After Dual Mobility Acetabular Systems: Minimum Five-Year Analyses

While dual mobility systems in total hip replacements have demonstrated reduced dislocation and revision occurrences, concerns persist about the potential elevation of metal ions in the bloodstream, leading to negative tissue reactions. Notably, there's a scarcity of research spanning over five years post-surgery that examines cobalt and chromium levels after such implants. This study aimed to delve into these metal ion concentrations after a five-year period, building on previous metal-ion findings. We focused on: (1) cobalt concentrations in blood and urine; (2) chromium concentrations in blood and urine; (3) cobalt variations based on follow-up duration and specific implant metrics (e.g., offset, cup dimension, stem, and neck inclination); and (4) chromium variations based on the same parameters.

We tracked 57 individuals who received THA using modular dual mobility systems from January 1, 2011, to December 31, 2016, for an average span of six years (ranging from five to 10 years). At the final check-up, we measured cobalt and chromium levels in serum, plasma, blood, and urine. We also evaluated parameters like head composition and dimension, stem offset, cup dimension, and stem-neck inclination.

Cobalt concentrations remained minimal, with average blood and urine values being 0.8+0.6mcg/L (standard <1.8mcg/L) and 1.2+1.0mcg/L (standard <2.8mcg/L), respectively. Two individuals exhibited a slight increase in blood cobalt concentration by 0.1 and 0.2mcg/L. Chromium averages in blood and urine were also minimal, with readings of 0.9+0.2mcg/L (standard <1.2mcg/L) and 1.3 + 0.5mcg/L (standard <2mcg/L), respectively. One individual had a marginally increased blood chromium concentration of 1.3mcg/L. Evaluations considering ceramic or cobalt-chrome heads, up to a decade of follow up, or varying implant metrics showed negligible variations in metal ion concentrations.

The findings reveal that over a minimum of five years (average = six years; span, five to 10 years), cobalt and chromium concentrations in patients' systems remained within normal limits and were clinically insignificant, irrespective of the follow-up duration, head material, or implant specifications. This underscores the efficacy of dual mobility systems in ensuring minimal metal ion presence.