Self-reported neurological clinical manifestations of metal toxicity in metal-on-metal hip arthroplasty

Self-Reported Neurotoxic Symptoms in Hip Arthroplasty Patients With Highly Elevated Blood Cobalt: A Case-Control Study

OBJECTIVES

This study aimed to investigate the prevalence of self-reported neurotoxicity and cognitive defects in hip replacement patients with markedly raised blood cobalt.

METHODS

Case group comprised 53 patients with metal-on-metal (MoM) implants and a history of blood Co ≥20 μg/L for a median of 3 years (interquartile range, 2-5 years). The control group comprised 53 patients with ceramic-on-ceramic prostheses and blood Co <1 μg/L. Median age was 67 years (interquartile range, 60-74 years). The participants completed the Neurotoxic Symptom Checklist-60, Diabetic Neuropathy Score, Douleur Neuropathique-10, and Systemic Symptom Checklist, and underwent the Mini-Mental State Examination.

RESULTS

The MoM and ceramic-on-ceramic groups were compared, the results were as follows: Neurotoxic Symptom Checklist-60 (median): cognitive defects (2.0 versus 1.9; P = 0.002), chest complaints (1.3 versus 1.3; P = 0.042), balance disturbances (1.3 versus 1.0; P < 0.001), sleep disturbances (2.7 versus 2.0; P = 0.004), mood disorders (2.0 versus 1.5; P = 0.001), sensorimotor disorders (1.6 versus 1.2; P < 0.001), physical complaints (2.0 versus 1.4; P = 0.009), fatigue (2.0 versus 1.6; P = 0.001), and total score (108 versus 90; P < 0.001); abnormal Diabetic Neuropathy Score/Douleur Neuropathique-10 (%): 60.3/13.2 versus 24.5/1.9 (P < 0.001/P = 0.028). Systemic Symptom Checklist (in percent): feeling cold (37.7 versus 17; P = 0.01), weight gain (18.9 versus 1.9; P = 0.008), metallic taste (26.4 versus 3.8; P = 0.002), worsening eyesight (37.7 versus 15.1; P = 0.008) and hearing (24.5 versus 7.5; 0.032), ankle swelling (32.1 versus 7.5; P = 0.002), shortness of breath on exertion (9.4 versus 5.7; P = 0.015), and generalized rash (28.3 versus 7.5; P = 0.01); and Mini-Mental State Examination (median): 29 versus 30 (P = 0.017). Patients in the MoM group were aware of their high cobalt levels and displayed a higher tendency to overreport symptoms (P < 0.001), which could have contributed to the higher scores.

CONCLUSIONS

Frequency of reporting a number of symptoms was markedly higher in MoM patients, but clinically significant neurotoxicity was not observed (possibly due to the short exposure to elevated cobalt). Patients with repeated blood Co ≥20 μg/L measurements should be questioned about possible systemic health complaints at follow-up.

The ototoxic potential of cobalt from metal-on-metal hip implants: a pilot study on the patient-reported auditory, vestibular, and general neurological outcome

OBJECTIVE

This study aimed to systematically investigate the ototoxic potential of cobalt in patients with a metal-on-metal (MoM) hip implant, using objective auditory and vestibular assessments and a questionnaire. The results of the objective evaluation were published previously, whereas the current study focused on the questionnaire outcome and its relationship to the blood cobalt level. Design and study sample: Twenty patients (33-65 years) with a primary MoM hip implant and 20 non-implanted control subjects, matched for age, gender, and noise exposure, received a questionnaire to evaluate the presence of several hearing and balance symptoms (part 1) and general neurological issues (part 2).

RESULTS

Concerning part 1, the proportion of auditory-related symptoms in general (p = 0.022) and tinnitus (p = 0.047) was significantly higher in the MoM patient group, whereas no group difference was found for hyperacusis, increased listening effort, and decreased speech understanding. Concerning part 2, no significant group differences were detected. Within the MoM patient group, the questionnaire outcome was not significantly different between the low-exposure and high-exposure subgroups according to the blood Co level.

CONCLUSIONS

In line with our previous study, these results potentially imply Co-induced impairment to the auditory system, despite the lack of a clear dose-response relationship.

Self-reported systemic complaints in patients with metal-on-metal hip arthroplasty

Introduction

An increase in blood serum metal ion levels is seen after implantation of all metal-on-metal (MoM) hip prosthesis. Systemic complaints contributed to raised cobalt ion concentrations in patients with MoM arthroplasty may lead to a variety of symptoms. The aim of this study is to investigate self-reported systemic complaints in association with cobalt ion concentrations in patients with any type of MoM hip prosthesis.

Methods

A cohort study was conducted. Patients with both unilateral and bilateral, resurfacing and large head metal on metal total hip arthroplasties (LHMoM THA) were included. Cobalt ion concentrations were measured by inductively coupled plasma mass spectrometry. Based on the known cobalt toxicity symptoms of case-reports and toxicology reports a new non-validated questionnaire was developed. Analysis was performed on two groups; a low cobalt ion concentration group and a high cobalt ion concentration group.

Results

A total of 62 patients were included with a mean age at surgery of 60.8 ± 9.3 years and a mean follow up of 6.3 ± 1.4 years. Mean cobalt ion concentrations were 104 ± 141 nmol/L (9-833). Based on the different thresholds (120-170 or 220 nmol/L) the low cobalt ion concentration group consisted of 44 (71%), 51 (82%) or 55 (89%) subjects respectively. In the 120 nmol/L and 170 nmol/L thresholds a significant difference in age was found. The composite score for OVS increased from 54% to 57%-68% with rising threshold value, a hint at the correlation between ion concentration and symptom prevalence.

Discussion

Ocular-vestibular symptoms were more common in high cobalt ion concentration groups for the three threshold levels tested and with increasing prevalence for higher threshold values. With regards to proactively inquired, self-reported symptoms the threshold where effects may be present could be lower than values currently applied in clinical follow-up.