# Screening of Metal Hypersensitivity in Pediatric Spine Surgery vs. Pectus Excavatum: A Comparative Cohort Study

## TL;DR

This study compares metal hypersensitivity rates in children undergoing spine surgery versus pectus excavatum repair, finding higher hypersensitivity in the latter group.

## Contribution

The study introduces a comparative analysis of metal hypersensitivity screening practices and outcomes in two pediatric orthopedic procedures.

## Key findings

- Spine surgery patients had a 3.3% hypersensitivity rate, while pectus excavatum patients had 12.8%.
- Spine patients were less likely to test positive despite being older and more female-dominated.
- Selective screening in spine surgery may underdiagnose hypersensitivity compared to routine testing.

## Abstract

Introduction: Metal hypersensitivity is a type-IV delayed-type hypersensitivity reaction that may contribute to complications in orthopedic surgeries. While its clinical relevance remains uncertain, immune responses to implants have been documented. Pediatric spinal deformity correction and pectus excavatum repair often involve the use of metal implants that contain known allergens, including nickel, cobalt, and chromium. Despite extensive adult data, prevalence in pediatric spine surgery remains underexplored.

Methods: This retrospective cohort study reviewed pediatric patients who underwent posterior spinal fusion with instrumentation or the Nuss procedure for pectus excavatum repair between 2014 and 2020. The spine cohort underwent selective preoperative screening based on a self-reported metal sensitivity questionnaire, while the pectus cohort received routine preoperative Patch Metal Allergy Testing (PMAT). Statistical analyses, including Fisher’s Exact Test and logistic regression, were performed to compare hypersensitivity prevalence and associated risk factors. Odds ratios (OR) with 95% confidence intervals (CI) were calculated for categorical comparisons.

Results: Of 796 spinal fusion patients, 118 (14.8%) underwent PMAT, yielding a 3.3% hypersensitivity rate. In contrast, 815 of 864 pectus excavatum patients completed PMAT, yielding a 12.8% hypersensitivity rate. Patients in the spine cohort were older (median age 15 vs. 14 years; p < 0.01) and more likely to be female (64.2% vs. 22.7%; OR = 6.11, 95%CI: 4.91-7.60; p < 0.0001). Despite this, they were significantly less likely to test positive for metal hypersensitivity (OR = 0.23, 95%CI: 0.15-0.36; p < 0.0001). When viewed from the pectus cohort perspective, this corresponds to 4.33 times higher odds of PMAT positivity.

Conclusion: The lower prevalence in spine patients likely reflects differences in PMAT determination rather than true population differences. This study highlights the potential underdiagnosis of hypersensitivity in the spine cohort when using selective screening, compared to routine testing in the pectus cohort. Determining higher yield screening criteria for spine surgery may result in detection rates more comparable to those found in the pectus cohort. Further research is needed to refine preoperative screening protocols and evaluate the clinical impact of metal hypersensitivity in pediatric orthopedic surgery.