Summary

PATCH TEST FOR METAL HYPERSENSITIVITY IN ELECTIVE ORTHOPAEDICS SURGERY CAN PREVENT FAILURE OF IMPLANTS

Abstract

Patch tests are the gold standard for allergic hypersensitivity, and they must be inclusive of Day seven readings to avoid missed reactions. Metal panel includes Nickel (Ni), Cobalt (Co), Chromium (Cr), Titanium (Ti), Copper (Cu), Aluminium (Al) and Molybdenum (Mo). Preoperative testing leads to minimized brittle failure in osteosynthesis and aseptic symptomatic arthroplasty cases. Positive Patch test may even mandate or guide implant removal and/or revision with hypoallergic implants. Patch test to metals is among major criteria for allergic dermatitis secondary to implant material. Any investigation acquires a role of preoperative routine investigation depending upon following parameters – Sensitivity, Specificity, Negative Predictive Value, Positive Predictive Value, Likelihood Ratio LR+ & LR-, ROC curve with Youden Index J, Accuracy Index, Clinical Utility Index CIU + & CIU - and Cost Benefit Ratio.

Materials And Methods

Case control study design was implemented with 400 cases of orthopedics implant and arthroplasty (operated between January 2023 – May 2024) and retrospective controls of same pattern (operated between July 2021 – December 2022). Excluded cases were immunocompromised patients, those on corticosteroids or biologics. The cases were subjected to personal interview and dermatological examination along with history of allergic contact dermatitis (ACD). 205 cases were shortlisted according to positive history. Patch tests were performed in all these cases using Pure metal or metal salts in proposed concentration. Erythema and papule or vesicle or bullae covering at least 50 % of Patch area is considered Positive Patch test. Hypersensitivity cases were offered alternate metal implants and proved effective.

Results

Statistical analysis showed max Ni hypersensitivity 36.1% followed by Cr 24.4% and Co 19.5% and almost same 4.9% for Al, Mo and Ti. Cu showed very few cases 1.46%. Statistical analysis showed brittle failure rate, and aseptic loosening was significantly reduced by using hypoallergic or alternate implants in cases with positive patch tests (p 0.03)

Conclusion

It is concluded that Patch test including day seven observation is a useful necessary test which can clearly guide implant selection and avoid future complications arising out of metallurgy in elective orthopedics surgery cases.
Keywords: metal hypersensitivity; allergic contact dermatitis (ACD); patch test; nickel;
cobalt; chromium; titanium; implants.