Sciatic nerve stiffness is not changed immediately after a slump neurodynamics technique

Abstract

Background: Neurodynamics techniques aim to assess and improve neural mechanosensitivity. However, there is no in vivo evidence regarding the mechanical effects of these techniques in the nerve stiffness. This study examined the immediate effects of a slump neurodynamics technique in the sciatic nerve shear wave velocity (SWV. i.e. an index of stiffness) using ultrasound-based elastography.

Methods: Fourteen healthy participants were included in this experiment. Sciatic SWV and ankle passive torque were measured during a passive ankle dorsiflexion motion (2°/s), before and immediately after 3 minutes of slump neurodynamics technique, randomly applied to one lower limb. The contralateral limb served as control.

Results: The slump intervention did not change the sciatic SWV (P=0.78), nor the dorsiflexion passive torque (P=0.14), throughout the ankle dorsiflexion motion. Excellent values of intra-rater repeatability (ICC=0.88, 0.68-0.96), and low values of standard error of measurement (0.59 m/s, 0.35-1.15m/s), were observed for the SWV measurements.

Conclusions: The sciatic nerve stiffness of healthy participants did not change immediately after a slump neurodynamics technique, suggesting a compliance of the neural tissue to tensile loads. However, these results ought to be confirmed using other neurodynamics techniques and in other populations (e.g. peripheral neuropathies).

Level of evidence: III.

Keywords: elastography; nerve biomechanics; shear wave velocity.

Figure 1 A–D

(A) Testing set-up. B-mode sonograms of sciatic nerve in (B) cross-sectional and (C) longitudinal views. The (D) elastogram window was defined over the nerve section, and the largest area within the epineurium was considered as region of interest. Legend: 1, Sciatic nerve cross-sectional area; 2, Sciatic nerve longitudinal view; 3, Sciatic nerve elastogram region of interest.

Figure 2

Slump test position.

Figure 3 A, B

(A) Shear wave velocity of the sciatic nerve and (B) ankle passive torque during the ankle passive rotation from 40° of plantar flexion (0%) to 80% of maximal dorsiflexion range of motion (ROM) before (pre) and after (post) the slump and control interventions. * Statistical different from the initial ankle position (0% of ROM).