Stephen Tower

Title : The association of cobalturia with cobaltism symptoms: A prospective blinded study of 229 post-arthroplasty patients

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 joint implants. However, the spectrum and epidemiology of orthopedic-implant cobaltism and its relationship to duration and degree of cobalt exposure is 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 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. Medical provider and public awareness of orthopedic-implant cobaltism is vital because tens-of-millions are at-risk and the toxidrome is reversible if diagnosed early. Further use of cobalt-chromium orthopedic-implants needs to be tempered given cobaltism becomes frequently clinically apparent at a spot urine-cobalt of 1 ppb or greater.

Biography:

Stephen S. Tower, MD received his medical degree from the University of Washington (Seattle) and completed internship in Internal Medicine at Dartmouth Hitchcock Medical Center (Lebanon, NH) followed by 4 years of service at a General Medical Officer for the Indian Health Service. He then completed residency in Orthopedic Surgery at Oregon Health Sciences University (Portland). He is a member of the American Academy of Orthopaedic Surgeons and is a current Diplomate of the American Board of Orthopedic Surgery. He has practiced Orthopedic Surgery in Anchorage since 1992 and is an affiliate Professor of Medicine at the University of Alaska. He works with Dartmouth Biomedical Engineering Center on research defining the failure mechanisms of modern hip replacements. This collaboration has resulted in multiple peer-reviewed publications. Dr. Tower authored the index case report of cobaltism from modern primary hip replacement in 2010 followed by additional publications concerning this common yet underappreciated entity. His experience with arthroprosthetic cobaltism as patient, surgeon, and researcher has been featured in three book chapters, the Netflix’s documentary The Bleeding Edge, and episodes on the medical TV serials House, Gray’s Anatomy, and New Amsterdam. Dr. Tower continues to practice arthroprosthetic surgery in Anchorage, Alaska.