Sonographic appearances of the normal ulnar nerve in the cubital tunnel

Purpose. To investigate the sonographic characteristics of the normal ulnar nerve in the cubital tunnel, as well as any differences related to age, sex, and dominant arm. Method. Two hundred twelve elbows in healthy volunteers were evaluated sonographically. The cross-sectional area (CSA) of the ulnar nerve within the cubital tunnel was measured with the elbow in extension and in flexion. The presence and number of fascicles was determined. The displacement of the ulnar nerve out of the cubital tunnel in full elbow flexion was also investigated. Results. The mean ± SD CSA of the ulnar nerve was 6.6 ± 1.7 mm2 (6.7 ± 1.8 mm2 in men and 6.5 ± 1.7 mm2 in women). The mean CSA of the ulnar nerve was highest for subjects aged 50–59 years, and lowest for subjects aged 30–39 years. Forty-two of 212 (19.8%) ulnar nerves had 2 fascicles, and 5 (2.4%) had 3 fascicles. The remaining 165 (77.8%) nerves had 1 fascicle. During elbow flexion, 49 of 212 (23.1%) ulnar nerves showed subluxation, and 18 (8.5%) were dislocated. Conclusion: There were differences in the CSA of the ulnar nerve between some age groups, but there was no variation with sex or handedness. Sonography can evaluate the morphologic changes of the nerve during flexion of the elbow. © 2008 Wiley Periodicals, Inc. J Clin Ultrasound, 2008