Impact of Raised Serum Cobalt Levels From Recalled Articular Surface Replacement Hip Prostheses on the Visual Pathway

Background

The articular surface replacement (ASR) was recalled in 2010 because of higher than expected revision rates. Patients reported symptoms of neurologic dysfunction including poor vision. This cohort study, using objective measurements, aimed to establish whether a higher incidence of visual function defects exists in ASR patients.

Methods

Thirty-three ASR patients and 33 non-ASR controls (control 1) were recruited. Data were compared with normative population data from the visual electrophysiology database (control 2). Patients underwent investigations for serum cobalt levels, psychophysical visual tests, and extensive electrophysiological visual testing.

Results

After excluding 2 subjects with pre-existing eye disease, data from 33 ASR patients were compared with the 2 control cohorts. The median serum cobalt level in the ASR group (median, 52 nmol/L interquartile range, 14-151 nmol/L]) was significantly higher than that in the control 1 cohort (median, 7 nmol/L interquartile range, 5-14 nmol/L]; P < .0001). The photoreceptor function of patients with an ASR of the hip showed significantly larger electroretinography mixed rod-cone b-wave amplitudes than both control 1 and control 2 cohorts (P = .0294 and .0410, respectively). Abnormalities in macular function as reflected by multifocal and scotopic electroretinography were more prevalent in control 1 (P = .0445 and .0275, respectively). Optic nerve pathway measurements using visual-evoked potential latency was significantly longer in the ASR group compared with those in the control 2 cohort (P = .0201). There were no statistical differences in visual acuity.

Conclusion

A statistically significant disturbance in visual electrophysiology was found in the ASR group when compared with the control groups. These differences did not translate to identifiable clinical visual deficits. Orthopedic surgeons need to be aware of the possibility of visual dysfunction in patients with ASR and other metal-on-metal hip arthroplasties; however, routine visual testing is not recommended.