Dynamic ultrasound evaluation of the ulnar nerve at the elbow in a healthy Colombian population

Abstract

Background The diagnosis of cubital tunnel syndrome is traditionally based on the patient's medical history, findings from physical examination, and electromyography. However, with the advancement of ultrasound as a diagnostic tool, which is more comfortable for patients than is electromyography, there has been research and exploration into the possibility of using ultrasound measurements as a diagnostic method for cubital tunnel syndrome. Hence, it is convenient to familiarize a healthy population with ultrasound measurements. Methods Forty healthy volunteers (20 women and 20 men) underwent ultrasound (US) of the ulnar nerve at two different time points. In this observational study, we measured the short and long axes of the nerve, the cross-sectional area of the nerve, the nerve-trochlea distance, the width, and the depth of the epicondylar groove at different degrees of elbow flexion-extension and at different levels. We also determined the number of individuals who presented with dislocation or subluxation of the nerve in relation to the tip of the epicondyle at different degrees of elbow flexion-extension. Additionally, we calculated whether there were changes in the flattening index. Statistical analysis was performed using tests for normality with the Shapiro‒Wilk test, the median and interquartile range were used as summary measures. Subsequently, for continuous variables, comparisons of values between two groups were conducted using the Mann‒Whitney, and Kruskal‒Wallis test were applied. Results Women and men have median ultrasound cross-sectional nerve area measurements of 4.0 mm² and 5.0 mm², respectively, at the level of the medial epicondyle with the elbow flexed at 90 degrees. No statistically significant differences were found between measurements taken and calculated values regarding the ultrasound morphology of the elbow and ulnar nerve in individuals between the first and second measurements. Men have greater nerve-trochlea distances, groove widths, and cross-sectional areas (both ultrasound and formula-derived) than women at various elbow measurement locations. Individuals with a body mass index (BMI) > 25 have a larger ulnar nerve diameter than individuals with a BMI < 25. Conclusions This study provides normative data on ulnar nerve ultrasound at the elbow in a Latin-American population.