Restoration of motor innervation by the «end-to-side» neurorraphia: experimental modeling and clinical and instrumental control of reinnervation
Authors: Nisht Aleksey Yur’evich , Fomin Nikolay Fedorovich , Imelbaev Artur Ilgizjvich , Mikulich Anastasia Arturovna 
Published: February 2020

The high probability of permanent loss of professional fitness and a significant risk of disability of the injured as a result of limb injuries with peripheral nerve damage contribute to both the continuous improvement of surgical techniques on the peripheral nerves, and the implementation of experimental and anatomical studies aimed at developing new ways to restore the lost innervation. Various types of peripheral nerve injuries are observed in peace and wartime victims in 2-6% and 9.8% of cases, respectively. The high degree of disability of patients with the consequences of peripheral nerve injuries requires improvement of diagnostic and reconstructive plastic approaches in this category of patients. A promising method of restoration of the distal part of the crossed nerve with extensive defects of the nerve trunk is its connection with the lateral surface of the intact donor nerve by the end-to-side neurorraphia. The lack of unambiguous views on the nature of reinnervation in this case, even in the presence of single publications on the positive outcomes of such interventions allow us to use this method only in the absence of the possibility of using autonerval transplants to replace extensive defects of peripheral nerves.
The purpose of the study: in experiments on laboratory animals to determine the features of modeling trauma of nerve trunks in relation to the development of the main stages of recovery of lost innervation by connecting peripheral nerves by the end-to-side neurorraphia and to determine the range of simple and demonstrative methods of clinical and instrumental control of the functional state of the restored peripheral nerves in a long-term experiment on laboratory animals.
Methods. A comprehensive experimental surgical and clinical-instrumental study was performed on 61 laboratory animals (Chinchilla rabbits of both sexes, phenotypically healthy individuals). In the experimental operating room under intravenous anesthesia, modeling of peripheral nerve defect was performed by resection of the total peroneal nerve with a length of 1 cm at the level of the middle third of the thigh. In animals of the studied group (n=39) to restore innervation, the "end-to-side" neurorraphia of the distal portion of the crossed common peroneal nerve with a specially formed defect of the perineural membrane on the lateral surface of the tibial nerve was performed. In the comparison group (n=22) no replacement of the defect of the common peroneal nerve was performed. The follow-up period after experimental interventions ranged from 1 to 290 days. Morphofunctional state of restored nerve trunks was determined by clinical, radiological and electrophysiological methods.
Research results. Performing unilateral resections of the common peroneal nerve in laboratory animals (rabbits) with subsequent restoration of the distal portion of the crossed nerve by connecting it by the end-to-side neurorraphia with a nearby intact donor nerve allows to obtain reproducible in the experiment positive results of tissue reinnervation. Indirect assessment of the functional state of the restored nerves is possible using simple and accessible clinical tests, for example, the amplitude of the abduction of the toes of experimental animals in the study of the unconditional reflex of preparation for landing characterizes the conductivity of the common peroneal nerve. When performing experimental studies with multi-stage reconstructive plastic interventions on the peripheral nerves of laboratory animals, the inclusion of radiological methods in the complex of diagnostic measures allows performing in vivo visualization of the surgical intervention area, the restored nerve trunk, as well as the tissues innervated by its branches, which makes it possible to adjust the plan of subsequent morphological studies.
Conclusions

Performing resection of the common peroneal nerve of laboratory animals (rabbits) at the level of the middle third of the femur as a model of peripheral nerve injury allows to practice the technique of restoration of the distal section of the crossed nerve by connecting it with the adjacent intact donor nerve of the end-to-side neurorraphia.
Performing a simple test with the initiation of an unconditional reflex of preparation for landing allows us to qualitatively assess the functional state of the common peroneal nerve in experimental animals.

3. The inclusion of radiological research methods in the program of comprehensive assessment of the peripheral nerves allows to perform their visualization in vivo with the definition of the main morphological characteristics of the restored in experimental reconstructive plastic interventions of nerve trunks.