Long-term invasive electrical stimulation of peripheral nerve in the functional recovery of neuromuscular complex in experiment

Abstract

Background. Limb damage dominates in the structure of combat trauma, making up to 75 % in modern wars and the number of wounded with peripheral nerve injuries of the limbs can be up to 25 %. The degree of disability of patients is 65–70 %, which makes the problem of restoring peripheral nerves extremely actual. The purpose of the study was to determine the effect of long-term invasive electrical stimulation on the functional restoration of the neuromuscular complex in experiment. Materials and methods. The study was performed on 29 white outbred rabbits (2500 ± 250 g, 5–6 months) according to all norms of bio­ethics. Animals were divided into the following experimental groups: group 1 (n = 8, controls) — epineural suture of the sciatic nerve and implantation of a non-working antenna of the electrical stimulation device; group 2 (n = 7): similar operation of epineural suture of the sciatic nerve with implantation of the electric stimulator antenna and stimulation on beginning at the 2nd day after the operation; group 3 (n = 7): a similar operation of the sciatic nerve epineural suture with implantation of an electric stimulator antenna and the start of stimulation after 2 weeks, when the initial signs of nerve regeneration were observed; group 4 (n = 7): autografting of the sciatic nerve and implantation of an electrical stimulator and the beginning of stimulation at a time point that will coincide with the signs of nerve regeneration. Results. Therefore, in group 2, where electrical stimulation was started the day after the operation, the indicators of functional recovery of the neuromuscular complex were better than in its absence, as well as under the conditions of starting the stimulation in the period when the initial signs of regeneration were observed. Therefore, it can be assumed that the invasive electrical stimulation of the peripheral nerve, started in the acute period after the injury, has a positive effect on the regeneration of the peripheral nerves, as well as on the results of the functional restoration of the neuromuscular complex. The positive effect of electrical stimulation on the functional state of muscles is indirectly evidenced by the larger amplitude of the compound muscle action potential (CMAP) in the group where the stimulation was started faster. A larger amplitude of the CMAP during the observation indicates a greater number of axons that reached the muscle during 8 weeks. Given that the growth cone of the regenerating nerve contains a certain number of axons that first grow to the effector organ, in this case the muscle, with a relatively unchanged action potential latency, it can be assumed that direct electrical stimulation of the peripheral nerve leads to an increase speed of axons sprouting, with their relatively unchanged number. The absence of a significant difference in the action potential latency in the groups where autografting and suture were performed under the same conditions of stimulation indicates a positive effect of stimulation on the myelination of nerve fibers. A better CMAP indirectly indicates a satisfactory functional state of the muscle, which in conditions of denervation allows to preserve its potential for recovery and prevent atrophy. Conclusions. Summarizing all of the above, according to the data of electrophysiological research, we can indirectly conclude that: 1) the impact of invasive electrical stimulation on the regeneration of the neuromuscular complex is positive, and is accompanied by a better effect if it is performed early after the injury; 2) invasive electrical stimulation of the peripheral nerve is a procedure that allows to accelerate the growth of nerve fibers, improve their myelination and prevent the loss of functional capacity of the denervated muscle.