Severity grading of cubital tunnel syndrome using diagnostic ultrasound

To investigate the diagnostic value of diagnostic ultrasound in the diagnosis and severity grading of cubital tunnel syndrome (CuTS). A retrospective analysis, which does not constitute a prospective clinical trial and therefore did not require registration, was performed on data from patients diagnosed with and without CuTS during the same period. Differences in ulnar nerve cross-sectional area (CSA) and ulnar nerve CSA/forearm nerve CSA (Ratio) were analyzed among patients with varying severity levels. The severity of CuTS was graded using the Gu classification system. Receiver operating characteristic (ROC) curve analysis was performed to assess the diagnostic value of each parameter in diagnosing CuTS and determining its severity. The area under the curve (AUC) values for CSA and the Ratio in diagnosing normal individuals versus those with mild CuTS were 0.96 and 0.98, respectively. For diagnosing mild-to-moderate CuTS, the AUC values were 0.83 and 0.85, respectively. For diagnosing moderate-to-severe CuTS, the AUC values were 0.77 and 0.61, respectively. Diagnostic ultrasound parameters have strong discriminatory value in stratifying the severity of cubital tunnel syndrome (CuTS), especially in the early stages of the disease. CSA & Ratio achieved excellent diagnostic efficiency (AUC = 0.96 and 0.98) for distinguishing normal controls from mild CuTS. These two ultrasound indices also showed good performance in differentiating mild‑to‑moderate (AUC = 0.83, 0.85) and moderate‑to‑severe CuTS (AUC = 0.77, 0.61). Based on ultrasound findings in this study, we propose a clinically practical CuTS severity grading scale corresponding to the Gu classification. Mild CuTS: CSA slightly increased, Ratio near normal range; mainly subjective symptoms, no obvious muscle atrophy. Moderate CuTS: CSA moderately enlarged, Ratio significantly changed; mild weakness, intermittent sensory loss. Severe CuTS: CSA markedly increased, Ratio distorted; persistent numbness, muscle atrophy, and impaired motor function.