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Cobaltemia and Cobaltism are common in Alaskans with failed Metal-metal Hips

by Dr Stephen Tower

Introduction

Systemic cobalt poisoning from excessive wear of a hip implant was first reported in 2001. The male patient presented with profound peripheral neuropathy, a metal laden pericardial effusion, and immune thyroiditis in 1997. Notable elevations of cobalt and chromium were detected in the patient’s blood and urine. The patient had no symptoms at his prosthetic hip but the chrome-cobalt femoral head was out-ofround on radiographs. A Metal-on-Ceramic Wear Mechanism (MoCWM) explained the patient’s extreme cobaltemia. Ceramic bits from the broken primary femoral head embedded in the revision plastic socket liner and severely abraded the revision chrome-cobalt alloy femoral head. 1

Nine years later we reported the first two cases of ArthroProsthetic Cobaltism (APC) from a Metal-on- Metal Wear Mechanism (MoMWM). The articular surfaces of a Metal-on-Metal Hip Replacement (MoMHR) are wrought or forged of chrome-cobalt alloy. 2 Our patients’ ASR (DePuy) hips wore excessively resulting in notable cobaltemia. Both men developed disordered mood and cognition, audiovestibular dysfunction, rashes, and symptomatic cardiomyopathies. The more severely cobaltemic and involved patient developed retinopathy. His Blood Cobalt Level ([BCo]) peaked at 122BET (122 times the Biologic Exposure Threshold [BET] of 1 mcg/L) and 600 times the mean [BCo] of subjects without hip replacements. 2 3 4 5 The ASR hips were exchanged for Ceramic-on-Plastic (CoP) implants after 3.5 years because of progressive hip pain and noise, the periprosthetic tissues were stained by metal debris (metallosis) and wear of the explant of the index patient was 2 orders of magnitude above that predicted by the ASR’s designers. 6 Both men’s mood and cognition improved over months as their [BCo] declined. Their cardiomyopathies, rashes, audio-vestibular and optic impairments largely resolved over three years. 7 An author of this paper (ST) was the index case and he wrote that report. The second subject was the only patient that ST implanted with an ASR hip. The surgeon’s [BCo] during his ASR implantation and recovery, and the chronology of the development and resolution of his constitutional, dermatological, psychological, neurological, and cardiac cobaltism manifestations are depicted in Figure 1.7 His JBJS report was accompanied by a commentary commissioned by the Presidential Line of the American Academy of Orthopedic Surgeons (AAOS) that concluded: 3 8 “The report is unusual because of the rarity of the occurrence of metal-induced systemic complications in patients with total hip replacement and the fact that the author was one of the patients. As millions of patients worldwide have undergone total hip replacement, these cases represent rare events indeed. ”

The full 18 page original manuscript can be downloaded here Cobaltemia and Cobaltism Dr Stephen Tower Feb 2014

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