Diagnosis and Severity Evaluation of Ulnar Neuropathy at the Elbow by Ultrasonography: A Case-Control Study.

Background: Traditional diagnostic techniques such as clinical examination and electrodiagnosis are less sensitive in diagnosing ulnar neuropathy at the elbow (UNE). Ultrasonography (USG) is increasingly being used to diagnose UNE. However, clinical applicability is limited by the lack of uniformity in the previous studies. Therefore, we aimed to study in the Indian patients the diagnostic utility of the ulnar nerve cross-sectional area (CSA) and a novel parameter-entrapment index (EI) in UNE measured by USG and to find if both these parameters correlate with the electrodiagnostic severity. Methods: This retrospective casecontrol study included 28 patients (36 nerves) of UNE and 12 (24 nerves) age- and gender-matched healthy controls. Electrodiagnostic severity was graded using the Padua classification. USG was performed in both groups, and CSA was measured at the medial epicondyle (ME) and 5 cm proximally and distally. EI was calculated by multiplying the ratio of CSA above ME over CSA at ME by 100. Best cutoffs were derived by the receiver operating characteristic curve analysis. Results: UNE group had significantly higher CSA at all three locations and lower EI than the control group. CSA at ME ≥9.7 mm2 and EI ≤61.5 has sensitivity and specificity of 88.9%/87.5% and 72.2%/79.2%, respectively. There was no significant difference in CSA and EI between nonsevere and severe UNE groups. Conclusion: CSA at ME and EI have good sensitivity and specificity in diagnosing UNE. However, they cannot differentiate nonsevere from severe UNE.