Abstract
INTRODUCTION: Cobalt is a mitochondrial toxin, clinical cobaltism manifests with constitutional, neurologic, and cardiovascular symptomatology. Cobalt's severe toxidrome is known through case reports from extreme wear or corrosion of cobalt-chromium arthroplasty components. However, the spectrum and epidemiology of orthopedic-implant cobaltism and its relationship to duration and degree of cobalt exposure are not well defined. METHODS: The relationship of urine-cobalt concentration and duration of exposure to cobalt-chromium joint implants and cobaltism symptomatology were prospectively studied in 229 patients. Subjects received a Cobaltism-Symptom-Inventory-Score (CSIS) based on a protocolized interview and examination followed by a spot urine-cobalt measurement. RESULTS: 129 (56%) subjects were cobalturic (urine-cobalt ≥1.0 ppb). 122 (53%) subjects had a CSIS of >2, this status significantly associates with cobalturia. Median [IQR] urine-cobalt in the subjects with a CSIS >2 was 4.1[1.1-17.0] ppb compared to 0.5[0.5-1.4] ppb in subjects with CSIS ≤ 2. Cobalturia has a sensitivity of 0.69, a specificity of 0.77, and a positive predictive value of 0.74 for a CSIS of >2. The product of years-exposed to a cobalt-chromium implant and urine-cobalt by quartiles significantly positively associates with the Cobaltism-Symptom-Inventory-Score. CONCLUSION: A urine-cobalt of ≥1 ppb likely indicates adverse systemic exposure to orthopedic-implant generated cobalt. Cobaltism severity as quantified by the CSIS significantly correlates with the product of spot urine-cobalt concentration and years-exposed to a cobalt-chromium orthopedic-implant indicating a dose-response relationship. Medical provider and public awareness of orthopedic-implant cobaltism is vital because tens-of-millions are at-risk and early cobaltism is reversible. Further use of cobalt-chromium orthopedic-implants should be questioned given cobaltism becomes clinically apparent at a spot urine-cobalt of 1 ppb or greater. Monitoring of patients with high-risk cobalt-chromium orthopedic-implants appears to be indicated.