Ultrasonic measurement for the diagnosis of cubital tunnel syndrome: A study in the Hong Kong Chinese population

Abstract

Introduction: Ulnar nerve enlargement is observed in ultrasound (USG) in patients with cubital tunnel syndrome (CuTS). This study aims to compare the ultrasound size of the ulnar nerve between CuTS patients and control subjects, to find the cut off size for diagnosis, and to validate the use of USG as an adjunct in CuTS diagnosis. Materials and Methods: There were 23 elbows with clinical and nerve conduction test (NCT) confirmed CuTS, and 42 elbows in the control group. Cases with elbow deformities, old ulnar nerve injuries and postoperative cases were excluded. The ulnar nerve cross sectional area (CSA) was measured at 6 different levels and positions: over the medial epicondyle (ME) in elbow flexion/extension, 2 cm and 5 cm distal to the ME, 2 cm and 5 cm proximal to the ME. A cut off CSA value for CuTS diagnosis was derived. Correlation between ulnar nerve CSAs and NCT was analysed. Results: The age and gender distribution were similar in both groups (61.2 vs 56.6; M > F, p > 0.05). The mean CSA of the CuTS group vs control group was 19.2 mm2 vs 7.0 mm2, 19.5 mm2 vs 7.1 mm2, 20.8 mm2 vs 8.1 mm2 at ME flexion, ME extension and maximal CSA respectively. The derived CSA cut off value for CuTS at ME flexion, ME extension and maximal CSA were 10.5 mm2, 11.5 mm2, and 15 mm2 respectively. The CSA difference at different levels between the 2 groups were significant except at 5 cm proximal to ME. A strong negative correlation was seen between the CSA and the across elbow nerve conduction velocity, with correlation coefficient of −0.748 at ME flexion, −0.654 at ME extension and -0.676 at maximal CSA. Conclusion: USG can be used as an adjunct for the diagnosis of CuTS with high accuracy and patient safety. It can also be used to delineate possible anatomical etiologies at the cubital tunnel.