(61) Metal Allergy Testing in Patients Listed for Temporomandibular Joint Replacement at Massachusetts General Hospital

Abstract: Patients with temporomandibular joint (TMJ) arthropathies (i.e end-stage degeneration, invasive pathology, or developmental anomalies) may be candidates for total joint replacement (TJR). There is only one FDA-approved manufacturer of patient-specific alloplasts of the TMJ, Stryker-TMJ Concepts. Stryker can fabricate a custom prosthesis composed of a cobalt-chromium-molybdenum alloy, with a maximum of 1% nickel present in the condylar component. However, metal hypersensitivity can occur, which may cause failure in up to 3% of TMJ replacements.1

All-titanium alloplasts exist and are a suitable alternative for those with metal hypersensitivity. However, FDA-approval for compassionate release is required, as is IRB approval. Metal allergy testing via lymphocyte transformation test (LTT) or skin patch test (SPT) is conducted beforehand to guide the choice of prosthesis. Currently, SPT is the gold standard. However, a dermatologist with expertise in patch testing is required, of which there are only a few in the country. LTT is a send-off blood test that can be performed at any phlebotomy lab. Some surgeons prefer LTT for detection of systemic allergy, as they believe it more accurately mimics the immunological response at the implant site.2 Our aim was to determine the agreeability between the LTT and SPT for detection of metal allergy.

This was a prospective analysis of patients who presented to Massachusetts General Hospital with TMJ arthropathies requiring TJR and were referred for LTT and SPT, from 2018-2022. Of the 31 patients included, the mean age was 45.2 years. 87.1% were female and 90.3% self-identified as White. Of the fourteen patients who completed both the LTT and SPT, 21.4% self-reported a history of metal allergy, while 50% self-reported a history of jewelry allergy. The results of LTT and SPT were discordant with regards to aluminum, cobalt, chromium, molybdenum, zirconium, or iron. 41.7% of patients who tested positive for nickel at any concentration on LTT also tested positive for nickel on SPT. 100.0% of patients who tested positive for vanadium at any concentration on LTT also tested positive for vanadium on SPT. The sensitivity and specificity of LTT were 46.2% and 83.8%, respectively.

In conclusion, in patients planned for TMJ TJR, there is the most agreement between LTT and SPT on vanadium allergy, followed by nickel allergy. There is no agreement on other metal allergies. When compared to SPT, LTT has a low sensitivity and high specificity.

1) Wolford LM, Morales-Ryan CA, Morales PG, Cassano DS. Autologous fat grafts placed around temporomandibular joint total joint prostheses to prevent heterotopic bone formation. Proc (Bayl Univ Med Cent). 2008 Jul;21(3):248-54. doi: 10.1080/08998280.2008.11928404. PMID: 18628972; PMCID: PMC2446413
2) Richards LJ, Streifel A, Rodrigues JM. Utility of Patch Testing and Lymphocyte Transformation Testing in the Evaluation of Metal Allergy in Patients with Orthopedic Implants. Cureus. 2019 Sep 25;11(9):e5761. doi: 10.7759/cureus.5761. PMID: 31723520; PMCID: PMC6825456.