Cobalt toxic optic neuropathy and retinopathy: Case report and review of the literature

Abstract

Purpose: We detail a case of cobalt toxicity with visual and systemic complications, review the pathogenic process for the optic neuropathy and retinopathy, and discuss the controversy of metallic hip prosthesis.

Observations: A 59-year-old female with a history of multiple left hip arthroplasties presented to our clinic with bilateral visual loss. The year prior, she had failure of the hip implant necessitating revision surgery with placement of a chrome-cobalt head. A few months after surgery, she began experiencing blurred and "white, spotty" vision in both eyes in addition to hypothyroidism, cardiomyopathy and neuropathy. The possibility of the patient's symptoms being due to cobalt toxicity from her hip prosthesis was proposed and she was found to have a serum cobalt level >1000 μg/L (normal 0-0.9 ng/mL). Visual acuity was 20/600 in the right and 20/800 in the left eye. There was bilateral temporal optic disc pallor. Goldmann visual field testing demonstrated bilateral central scotomas, optical coherence tomography (OCT) showed severe ganglion cell layer-inner plexiform layer (GCLIPL) thinning and multifocal electroretinography (mfERG) demonstrated decreased amplitudes in both eyes. She underwent a total hip revision arthroplasty with extensive debridement of "black sludge" found within a pseudocapsule. Four days after surgery, cobalt serum levels had significantly decreased to 378 ng/mL. One month after surgery, she had significant improvement in visual acuity (20/150 right eye, 20/250 left eye), Goldmann visual field testing, and mfERG. OCT showed retinal nerve fiber thinning and persistent GCLIPL thinning in both eyes.

Conclusions and importance: Excessive cobalt levels can result in systemic toxicity leading to visual changes, peripheral neuropathy, hearing loss, cognitive deficits, cardiomyopathy and hypothyroidism. In recent years it has become apparent that cobalt toxicity can be associated with metal-on-metal total hip arthroplasty, or the grinding effects of retained ceramic particles from a fractured ceramic head on a cobalt-chromium femoral head prosthesis.

Keywords: Ceramic hip prosthesis; Cobalt toxicity; Metal on metal hip prosthesis; Optic neuropathy; Retinopathy.

Fig. 1

A. Ceramic fragments pigmented dark from the “black sludge” following March 2017 catastrophic failure of hip implant. B. Extensive black discoloration of subcutaneous tissue and black sludge material under the fascia was noted during the August 2018 hip revision surgery.

Fig. 2

A. Color fundus photographs showing bilateral temporal optic disc pallor prior to August 2018 hip revision surgery. B. Goldmann visual field testing demonstrates bilateral central scotomas prior to August 2018 hip revision surgery in August 2018. C. Goldmann visual field testing one month after the revision surgery demonstrates breaking up of the bilateral central scotomas. . (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

A. Optical coherence tomography of the retinal nerve fiber layer shows normal thickness in both eyes before the August 2018 revision surgery. B. Optical coherence tomography of the ganglion cell layer shows diffuse thinning in both eyes before the August 2018 revision surgery. C. Optical coherence tomography of the retinal nerve fiber layer shows moderate thinning in the right eye and severe thinning in the left eye one-month post revision surgery. D. Optical coherence tomography of the ganglion cell layer shows persistence of diffuse thinning in both eyes one-month post revision surgery.

Fig. 4

A. Initial multifocal electroretinography (mfERG) four days after surgery demonstrates decreased tracing amplitude. B. Repeat mfERG one month after revision surgery shows improvement with an increase in the tracing amplitude.

Fig. 5

A. Illustration of the original hip prosthesis with a ceramic ball (a.k.a. head) and a ceramic liner. B. Ceramic ball fracture in the setting of catastrophic failure of the hip implant. C. Retained ceramic fragments remain present at the site of the previous fracture despite debridement during revision surgery. D. After the first revision surgery, the components of the hip prosthesis included a cobalt ball and chrome, polyethylene liner. E. Ceramic fragments embedded into the polyethylene liner grinding down on the cobalt femoral ball releasing cobalt into the systemic circulation.