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

In this cross-sectional study, 32 patients with LE persisting for at least 6 months underwent comprehensive clinical, electrophysiological, and ultrasonographic assessments. RTS diagnosis was determined using ultrasound-guided posterior interosseous nerve (PIN) block as a reference standard and compared with diagnostic criteria based on nerve cross-sectional area (CSA) threshold values and contralateral side measurements. Pre- and post-block pain levels during clinical tests were also analyzed.

Results: RTS was diagnosed in 44% of patients using the injection test. PIN CSA and anteroposterior (AP) thickness were larger on the symptomatic side but did not differ significantly between RTS-positive and RTS-negative cases. Electrophysiological findings were normal in all patients, and LE ultrasound findings did not vary based on the presence of RTS. Agreement between RTS diagnosis and US-CSA comparison with the contralateral side was slight (κ=0.138; p=0.4024), while threshold values showed no agreement (κ=0.098; p=0.118). Cozen’s test demonstrated the highest reliability, with significant pain reduction following the block.

Conclusions:

RTS frequently coexists with treatment-resistant LE. Comparing PIN-CSA with the asymptomatic side, along with the US-guided PIN block, enhances diagnostic accuracy.