Among patients with unexplained pain after undergoing total joint replacement with metal-containing components, women are more likely than men to test positive for metal sensitisation, according to a report by Nadim Hallab and colleagues from Rush University Medical Center, Chicago.
“These findings may explain, at least in part, the sex disparity in the outcomes of certain total joint arthroplasty implant designs,” the researchers write.
The authors reviewed data on 2,613 patients who were evaluated for unexplained joint pain after total hip and/or knee replacement. All had metal-containing joint replacement components, and none had signs of infection, inflammation or other findings that would explain their pain.
The patients averaged 62 years of age; 60 per cent of the patients were women. The average time since joint replacement was about three years, and in most cases it was less than two years. Women had higher average pain scores than men: 6.8 versus 6.1, on a scale of 0 to 10.
All patients underwent a blood test – the lymphocyte transformation test (LTT) – to evaluate immune cell sensitisation to metals. The LTT results suggested immune sensitisation to implant metals in 49 per cent of women, compared to 38 per cent of men. The difference persisted when researchers used a more stringent definition of sensitisation: 25 versus 18 per cent. In addition, among patients with positive LTT results, the severity of metal sensitivity was greater in women.
Prior to blood testing, 29 per cent of women with pain after joint replacement said they had allergic skin reactions to metals, compared to 4 per cent of men.
The results show a ‘remarkable and significant’ increase in immune cell sensitivity to metals in women compared to men with unexplained pain after total hip or knee replacement. “This supports both our hypothesis and previous reports that females may have a higher risk of adverse responses to implant metals,” Hallab and co-authors write.
The findings support the possibility that the higher rate of complications after total joint replacement in women may have an ‘adaptive immunological basis.’ But it’s still unclear whether the sex-related difference in immune sensitisation is related to intrinsic biological factors, such as hormones, or to environmental factors, such as exposure to metals in jewellery or cosmetics.
The study also couldn’t determine whether sensitisation to metals is a pre-existing condition, or induced by the metal-containing joint implants, or a combination of the two. The researchers call for more targeted studies to assess the clinical outcomes of patients who test positive for metal sensitisation.
Reference: Marco Caicedo and others. Females with Unexplained Joint Pain Following Total Joint Arthroplasty Exhibit a Higher Rate and Severity of Hypersensitivity to Implant Metals Compared with Males. The Journal of Bone and Joint Surgery, 2017; 99 (8): 621 DOI: 10.2106/JBJS.16.00720
Source: Wolters Kluwer Health