Comparing 1-year and 10-year whole blood metal ion results following Birmingham hip resurfacing for osteoarthritis

Abstract

Background: Patients with metal-on-metal hip arthroplasty may develop adverse reactions to metal debris that can lead to clinically concerning symptoms, often needing revision surgery. As such, many regulatory authorities advocate for routine blood metal ion measurement. This study compares whole blood metal ion levels obtained 1 year following Birmingham Hip Resurfacing (BHR) to levels obtained at a minimum 10-year follow-up. Methods: A retrospective chart review was conducted to identify all patients who underwent a BHR for osteoarthritis with a minimum 10-year follow-up. Whole blood metal ion levels were obtained at final follow-up in June 2019. These results were compared with patients’ metal ion levels at 1 year. Results: Of the 211 patients who received a BHR, 71 patients (54 males and 17 females) had long-term metal ion levels assessed (mean follow-up 12.7 ± 1.4 yr). The mean cobalt and chromium levels for patients with unilateral BHRs (43 males and 13 females) were 3.12 ± 6.31 μg/L and 2.62 ± 2.69 μg/L, respectively; for patients with bilateral BHRs (11 males and 4 females) cobalt and chromium levels were 2.78 ± 1.02 μg/L and 1.83 ± 0.65 μg/L, respectively. Thirty-five patients (27 male and 8 female) had metal ion levels tested at 1 year postoperatively. The mean changes in cobalt and chromium levels were 2.29 μg/L ( p = 0.0919) and 0.57 μg/L ( p = 0.1612), respectively. Conclusion: Our results suggest that regular metal ion testing as per current regulatory agency guidelines may be impractical for asymptomatic patients. Metal ion levels may in fact have little utility in determining the risk of failure and should be paired with radiographic and clinical findings to determine the need for revision.