Prevalence of metal hypersensitivity in total knee replacement

Cutaneous and local reactions to metals used in orthopaedic implants have been well documented. The prevalence of metal sensitivity in general population is 10%-15%. Nickel, Cobalt and Chromium are the most common allergen. The association between cutaneous reactions and implants has been less understood. Hence, this study was taken up with the aim to assess the prevalence of metal hypersensitivity in Total Knee Replacement (TKR) patients and find the most prevalent allergen.

Longitudinal study conducted during January-December 2017. We enrolled 233 subjects who were at least three months postoperative. Radiological assessment was done. CREDISOL® kit was used for patch test. Results were recorded using ICDRG grading at 48 hours and five days.

Mean age was 59.59 years; 12.01% were symptomatic. Pain followed by loss of function were the most common symptoms. However, loss of function and patient dissatisfaction towards procedure were significantly associated with metal hypersensitivity (χ² value > 3.84; p value < 0.05). In 66% subjects, pre-operative diagnosis was severe osteoarthritis, followed by rheumatoid arthritis (23%). None of the subjects had evidence of loosening on X-ray. Prevalence of Metal Hypersensitivity was found to be 15.87% (patch test positive). Chromium (11.58%) was found to be most common allergen followed by Nickel (8.58%) and then Cobalt (6.43%).

Significant prevalence of metal hypersensitivity was found. Therefore, we recommend pre-operative patch test for detecting allergic reactions to implants. Alternatives like Titanium or Zirconium can be used to avoid complications.