Diagnosing Systemic Amyloidosis Presenting as Carpal Tunnel Syndrome: A Risk Nomogram to Guide Biopsy at Time of Carpal Tunnel Release

J Bone Joint Surg Am. 2021 Jun 7. doi: 10.2106/JBJS.20.02093. Online ahead of print.

Abstract

Background: As carpal tunnel syndrome often precedes other signs of systemic amyloidosis, tenosynovial biopsy at the time of carpal tunnel release may facilitate early diagnosis and treatment. However, evidence-based guidelines for amyloidosis screening during carpal tunnel release have not been established. We sought to develop a predictive model for amyloidosis after carpal tunnel release to inform screening efforts.

Methods: We performed a retrospective cohort study of adults without known amyloidosis undergoing at least 1 carpal tunnel release from 2000 to 2019 with use of the national Veterans Health Administration database. After estimating the cumulative incidence of amyloidosis after carpal tunnel release, we identified risk factors, constructed a predictive nomogram based on a multivariable subdistribution-hazard competing-risks model, and performed cross-validation.

Results: Among 89,981 patients undergoing at least 1 carpal tunnel release, 310 were subsequently diagnosed with amyloidosis at a median interval of 4.5 years, corresponding to a cumulative incidence of 0.55% (95% confidence interval [CI]: 0.47% to 0.63%) at 10 years. Amyloidosis diagnosis following carpal tunnel release was associated with an increased hazard of heart failure (hazard ratio [HR], 4.68; 95% CI: 4.26 to 5.55) and death (HR, 1.27; 95% CI: 1.07 to 1.51) after adjustment for potential confounders. Age, male sex, Black race, monoclonal gammopathy of undetermined significance or multiple myeloma, rheumatoid arthritis, atrial fibrillation, spinal stenosis, and bilateral carpal tunnel syndrome were independently associated with increased risk of amyloidosis diagnosis and were included in the risk nomogram.

Conclusions: Amyloidosis diagnosis after carpal tunnel release is rare but is associated with poor outcomes. We present an amyloidosis-risk nomogram to help guide tenosynovial biopsy at time of carpal tunnel release.

Level of evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.