The effects of neurodynamic mobilization on fluid dispersion within the tibial nerve at the ankle: an unembalmed cadaveric study

Abstract

Objective: To evaluate the effects of neurodynamic mobilization on the fluid dynamics of the tibial nerve in cadavers.

Background: Evidence showing patients benefit from neural mobilization is limited. Mechanisms responsible for changes in patient symptoms are unclear.

Methods: Bilateral lower limbs of six unembalmed cadavers (n = 12) were randomized into matched pairs and dissected to expose the tibial nerve proximal to the ankle. Dye composed of Toulidine blue and plasma was injected into the nerve. The longitudinal dye spread was measured pre- and post-mobilization. The experimental group received the intervention consisting of 30 repetitions of passive ankle range of motion over the course of 1 minute. The matched control limb received no mobilization. Data were analysed using a 2×2 repeated measures ANOVA with subsequent t-tests for pairwise comparisons.

Results: Mean dye spread was 23.8±10.2 mm, a change of 5.4±4.7% in the experimental limb as compared to 20.7±6.0 mm, a change of -1.5±3.9% in the control limb. The ANOVA was significant (P⩽0.02) for interaction between group (experimental/control) and time (pre-mobilization/post-mobilization). t-test results were significant between pre- and post-mobilization of the experimental leg (P = 0.01), and between control and experimental limbs post-mobilization (P⩽0.02).

Conclusion: Passive neural mobilization induces dispersion of intraneural fluid. This may be clinically significant in the presence of intraneural edema found in pathological nerves such as those found in compression syndromes.

Keywords: Cadaver; Compression; Entrapment; Nerve; Neurodynamic; Neuropathy; Tibial.

Figure 1

Pathophysiological responses due to nerve injury. Edema propagates the cycle.

Figure 2

Before dye injection, location of window for dissection was identified and marked starting just proximal to the distal tip of the medial malleolus. The skin flap was incised and the neurovascular bundle was separated in order to free the tibial nerve from all adjacent tissue. This was necessary in order to visualize and measure the nerve. The injection site was marked with a coloured marker as well as a T-pin.

Figure 3

Dye injection (pilot study). The injection amount and method were piloted on embalmed cadavers. The amount of dye needed was determined by the ability to create a bolus without leaking from the nerve. The needle was injected just beneath the external epineurium.

Figure 4

Caliper measurements. The measurements were made by one investigator who was blinded to the digital reading. The average of three successive measurements at each 2-minute interval was recorded.

Figure 5

Neural mobilization was performed through 30 repetitions of ankle dorsiflexion/plantar flexion to end range.

Figure 6

Mean fluid dispersion after mobilization. Statistical significance based on t-test results. At pre-test, the experimental group data were normalized to the control group data. **P⩽0.05, significantly different from pre-mobilization condition (P = 0.009); ^#P⩽0.05, significantly different from control group (P = 0.022).