Wear and Tear Vision

Radiography of the hip was suggestive of periarticular wear debris around the prosthesis. As the patient underwent hip prosthesis revision, the surgical site revealed a worn-down CoCrMo metal head with high quantities of metallic debris around the prosthesis.The blood test revealed extremely elevated cobalt levels (6975 nmol/l, normal <17) confirming the diagnosis of cobalt neurotoxicity. Endogenous cobalt poisoning may induce toxic effects in both retinal ganglion cells and optic nerve fibers (1, 2). Previously reported cases described improvement of sight after metal ion concentrations decreased. Although cobalt concentrations decreased rapidly during the months after hip revision, the patient's vision did not improve. Our patient's course suggests that the neurotoxic effects may be irreversible when cobalt poisoning persists for too long at very high levels. In hindsight, the deterioration of the patient's general condition including many of her varied symptoms could be attributed to cobalt toxicity (3): The patient did not only suffer from vision loss, but also from hearing impairment and imbalance. Accordingly, video head impulse testing demonstrated bilateral vestibular loss. Although the patient has not been formally tested, the acral paresthesias could be indicative of a cobalt-induced polyneuropathy. In addition, the patient suffered from cardiomyopathy, as confirmed by heart muscle biopsy showing cardiomyocytic degeneration, vacuolation and atrophy, as well as mild fibrosis. The circumstances leading to the toxic metallosis in the hip could be explained by the sequence of implants used (4). Initially, the hip prosthesis had to be revised because of a fracture of the ceramic femoral head (5). The ceramic head was then replaced by a metal head paired with a polyethylene inlay. Presumably, fine ceramic particles left behind from the broken head subsequently adhered to the polyethylene inlay grinding down the new metal head like a grindstone.