Relationship Between Gender, Age, BMI and Side of Body on the Size and Position of Nerves of the Brachial Plexus in Axilla: Pilot Study.

Background and Objectives Studies demonstrate variations in the size and position of the nerves in the brachial plexus. The objective of this pilot study was to determine the effect of age, gender, BMI and side of body on the size and position of these nerves and to determine the feasibility of a further study. Methods Twenty healthy volunteers were recruited. The ultrasound position of the nerves was confirmed by a dynamic scan. The size of the nerves was calculated using the freehand calliper tool. A graph was designed to study the position of the nerves. ImageJ was used to analyse the position of the nerves. Student's t-tests were carried out to compare the gender and side of arm with the size of the nerve. Pearson's correlation coefficients were calculated to determine the correlation between BMI and age with the size of the nerves. The position of the nerves was compared between male and female, and left and right sides of the body. Results The mean size of the median nerve, musculocutaneous nerve, radial nerve and ulnar nerve was 0.099, 0.032, 0.179 and 0.076 cm2 (males) and 0.091, 0.022, 0.128 and 0.026 cm2 (females), respectively. There were significant differences between the size of nerves and gender in the musculocutaneous, radial and ulnar nerves (P <0.05). The correlations between the sizes of the nerves with BMI and age were not significant. The position of the radial nerves was found to be variable within the same genders and between males and females. The position of the nerves was variable between the left and right hand side. Conclusion The position and size of brachial plexus branches in axilla is very variable. This pilot study highlights the need for further research with larger sample sizes to fully understand the extent and implication of this variability.