The influence of scapular depression on upper limb neurodynamic test responses

Abstract

Objectives: Upper limb neurodynamic testing (ULNT) can be used clinically to assist in identifying neural tissue involvement in patients with upper quarter pain and dysfunction. Consideration for scapular positioning is a crucial component of ULNT standardization, as variations in positioning may dramatically impact sensory and motor responses. This study aimed to determine if there was a meaningful difference in test outcomes when the ULNT was performed in alternative scapular positions.

Methods: This cross-sectional study included 40 asymptomatic individuals. Repeated ULNT testing was performed on the dominant limb with the scapula blocked in neutral (ULNTb) and in scapular depression (ULNTd). Sensory responses, muscle activity, and range of motion outcomes were compared between the two test variations.

Results: Pre-positioning in scapular depression (ULNTd) led to reduced elbow extension range of motion, provoked greater upper trapezius muscle activity and an earlier onset and broader area of sensory responses compared to ULNTb.

Discussion: During ULNTb, the limbs were taken further into range and elicited reduced muscle activation and more localized sensory response providing a less vigorous version of the test. This study demonstrates that scapular positioning has a meaningful impact on ULNT test outcomes in healthy, asymptomatic individuals. The ULNTd can be considered a more vigorous version that may be appropriate when the cervical motions commonly utilized for structural differentiation are limited or contraindicated.

Keywords: Mechanosensitivity; Neurodynamics; Range of motion.

Figures

Figure 1

Elbow extension range of motion at the end of the ULNT test sequence for ULNTb (y-axis) and ULNTd (x-axis). Line represents the absolute y = x condition indicated by the slope 1/1. Data points above the line are indicative of more elbow extension range during ULNTb compared to ULNTd. Data points below the y = x line are indicative of less elbow extension range during ULNTb compared to ULNTd. Right handed individuals are represented with blue circles and left handed individuals are represented with red circles. Full elbow extension is defined as 180°.

Figure 2

Muscle activity during ULNT is represented as percent increase above resting levels with error bars representing the SD. The numbers within each bar graph represent the frequency of muscle activity above the threshold (three SDs above resting muscle activity level). The horizontal red line indicates the average threshold for muscle activation. Asterisk (*) indicates significant increase muscle activity above resting levels and cross (†) indicates significant differences between ULNTb and ULNTd (P<0.05).

Figure 3

Sensory responses during ULNT are presented. Blue data points represent the ULNTb and red data points represent the ULNTd. The onsets of sensory responses are indicated by boxes with a solid line showing the cumulative percentages throughout the testing sequences. The number of areas within the limb that were reported to have sensory responses is presented as circles (one area reported), diamonds (two areas reported) and triangles (all three areas reported) with the dashed line. Asterisks (*) indicate significant differences between ULNTb and ULNTd.