The effect of shoulder abduction and medial epicondylectomy on ulnar nerve strain: a preliminary study

Objectives: The primary aim was to determine whether a dynamic suture marker method of measuring ulnar nerve strain yields comparable results to strain gauges. The secondary aim was to assess the effect of elbow flexion, shoulder abduction and medial epicondylectomy on strain. Methods: In four embalmed elbows, ulnar nerve strain was measured using suture markers during elbow flexion and shoulder abduction before and after medial epicondylectomy. Linear regression analysis and Wilcoxon signed-rank test were used to analyse the results. Results: Ulnar nerve strain increased in direct proportion to elbow flexion angle before and after medial epicondylectomy, with one exception. At 90° shoulder abduction, strain was 0%–17%. Strain was greatest at 90° and least at 110° before and after medial epicondylectomy, P > 0.05. The effect of medial epicondylectomy varied. Strain was reduced at 90° by 5%, at 110° by 0% and at 120° by 1%; P > 0.05. Conclusions: The suture marker method yielded comparable results to strain gauges. Both shoulder abduction and medial epicondylectomy did not have statistically significant effects on ulnar nerve strain. However, only four embalmed elbows were studied in this preliminary study, so a large difference would be needed to produce a significant change. The finding that medial epicondylectomy fails to reduce strain raises questions about its role in treating cubital tunnel syndrome and highlights the need for further research. The authors believe that the technique described for dynamic strain assessment is applicable in an in vivo setting and therefore, should be used to compare strain properties of cadaveric and in vivo nerves.