Metal Hypersensitivity Reactions to Orthopedic Implants

Area of Science:

• Orthopedic Surgery
• Allergy and Immunology
• Biomaterials Science

Background:

• Total hip and knee replacements commonly use metal alloys.
• Type IV allergic reactions to these implants are infrequent but can cause significant morbidity.
• Predicting reactions, even with pre-existing metal allergy, remains challenging.

Purpose of the Study:

• To review the current understanding of peri-implant metal allergic reactions.
• To provide evidence-based conclusions regarding diagnosis and management.
• To identify areas requiring further research.

Main Methods:

• Literature review of scientific publications on metal allergy in joint replacement.
• Analysis of diagnostic approaches including patch testing and lymphocyte transformation testing (LTT).
• Evaluation of clinical outcomes following revision surgery with inert devices.

Main Results:

• Routine pre-implant allergy testing in asymptomatic individuals is not indicated.
• Patient-reported concerns regarding metal allergy should be considered.
• Patch testing is suggested as a primary screening method.
• Post-implantation testing is controversial; positive results do not definitively diagnose metal allergy.
• Complete recovery after revision with an immunologically inert device suggests a metal allergy diagnosis.

Conclusions:

• Current evidence supports limited conclusions on peri-implant metal allergy.
• A diagnostic approach involves considering patient concerns, patch testing, and revision outcomes.
• Further research is necessary to scientifically address this clinical issue.