Tension of the Ulnar, Median, and Radial Nerves During Ulnar Nerve Neurodynamic Testing: Observational Cadaveric Study

Abstract

Background The ulnar nerve upper limb neurodynamic test (ULNT3) uses upper limb positioning to investigate symptoms arising from the ulnar nerve. It is proposed to selectively increase tension of the nerve; however, this property of the test is not well established. Objective The aim of this study was to determine the upper limb position that results in: (1) the greatest tension of the ulnar nerve and (2) the greatest difference in tension between the ulnar nerve and the other 2 major nerves of the upper limb: median and radial. Design This was an observational cadaver study. Methods Tension (in newtons) of the ulnar, median, and radial nerves was measured simultaneously using 3 buckle force transducers in 5 upper limb positions in 10 embalmed human cadavers (N=20 limbs). Repeated-measures analysis of variance (ANOVA) with Bonferroni post hoc tests determined differences in tension among nerves and among limb positions. Results The addition of shoulder horizontal abduction (H.Abd; 12.62 N; 95% confidence interval [95% CI]=10.76, 14.47) and combined shoulder abduction and internal rotation (H.Abd+IR; 11.86 N; 95% CI=9.96, 13.77) to ULNT3 (scapular depression, shoulder abduction and external rotation, elbow flexion, forearm pronation, and wrist and finger extension) produced significantly greater ulnar nerve tension compared with the ULNT3 alone (8.71 N; 95% CI=7.25, 10.17). The ULNT3+H.Abd test demonstrated the greatest difference in tension among nerves (mean difference between ulnar and median nerves=11.87 N; 95% CI=9.80, 13.92; mean difference between ulnar and radial nerves=8.47 N; 95% CI=6.41, 10.53). Limitations These results pertain only to the biomechanical plausibility of the ulnar nerve neurodynamic test and do not account for other factors that may affect the clinical application of this test. Conclusions The ULNT3+H.Abd is a biomechanically plausible test for detecting peripheral neuropathic pain related to the ulnar nerve. In situations where the shoulder complex will not tolerate the combination of shoulder external rotation in abduction, performing upper limb neurodynamic tests with internal rotation instead of external rotation is a biomechanically plausible alternative.