History of metal allergy in cervical and lumbar arthroplasty: A review

Cervical and lumbar total disc replacement (TDR) has emerged as a motion-preserving alternative to spinal fusion, offering favorable outcomes and reduced adjacent segment disease. However, the use of metal-on-metal implants introduces the rare but clinically significant risk of metal hypersensitivity. This review examines the pathophysiology, diagnostic approach, and treatment considerations surrounding metal allergy in spinal arthroplasty. Metal ions released through implant wear may act as haptens, triggering immune responses, most commonly type IV delayed hypersensitivity, leading to chronic inflammation, soft tissue masses, and implant failure. While metal allergy is well documented in hip and knee arthroplasty, its role in spinal TDR remains underrecognized, with current literature limited to isolated case reports. These reports consistently describe symptom recurrence, sterile inflammatory masses, and histologic findings rich in lymphocytes and eosinophils, often requiring revision surgery and hardware removal. Patch testing is the preferred diagnostic method in patients with a suspected reaction, though its routine use preoperatively is not recommended unless a known history of metal allergy exists. All documented cases in cervical and lumbar TDR were ultimately managed with explanation and fusion, resulting in symptom resolution. Given the increasing prevalence of disc arthroplasty and the estimated 10–15% of the population with metal sensitivity, awareness of this complication is essential. Emerging evidence supports the potential of alternative implant materials such as ceramics and PEEK to mitigate this risk. Further research is warranted to establish incidence rates, optimize screening strategies, and develop hypersensitivity-resistant biomaterials for spinal arthroplasty.