Ultrasonographic and Electrophysiologic Assessment of Radial Tunnel Syndrome in Patients With Treatment-Resistant Lateral Epicondylitis: Insights into Diagnostic Utility and Clinical Implications

Keles A., PALAMAR KADIOĞLU D., Gunduz A., Akarirmak U.

AMERICAN JOURNAL OF PHYSICAL MEDICINE & REHABILITATION, vol.105, no.4, pp.330-337, 2026 (SCI-Expanded, Scopus)

Abstract

ObjectivesThe aims of the study were to evaluate radial tunnel syndrome in patients with treatment-resistant lateral epicondylitis and to assess the diagnostic utility of ultrasonographic, electrophysiologic, and clinical evaluations.DesignIn this cross-sectional study, 32 patients with lateral epicondylitis persisting for at least 6 mos underwent comprehensive clinical, electrophysiological, and ultrasonographic assessments. Radial tunnel syndrome diagnosis was established using an ultrasound-guided posterior interosseous nerve block as the reference standard and compared with diagnostic criteria based on nerve cross-sectional area threshold values and side-to-side cross-sectional area comparison. Preblock and postblock pain levels during clinical tests were also analyzed.ResultsRadial tunnel syndrome was diagnosed in 44% of patients using the injection test. The mean cross-sectional area of the posterior interosseous nerve was larger on the symptomatic side but did not differ significantly between radial tunnel syndrome-positive and radial tunnel syndrome-negative cases. Electrophysiological findings were normal in all patients, and lateral epicondylitis ultrasound findings did not vary based on the presence of radial tunnel syndrome. Agreement between radial tunnel syndrome diagnosis and ultrasound-cross-sectional area comparison with the contralateral side was slight (kappa = 0.138; P = 0.4024), while threshold values showed no agreement (kappa = 0.098; P = 0.118). Cozen's test demonstrated the highest reliability, with significant pain reduction following the block.ConclusionsRadial tunnel syndrome frequently coexists with treatment-resistant lateral epicondylitis. Comparing posterior interosseous nerve-cross-sectional area with the asymptomatic side, along with the ultrasound-guided posterior interosseous nerve block, enhances diagnostic accuracy.