Contralateral L-6 nerve root transfer to repair lumbosacral plexus root avulsion: experimental study in rhesus monkeys

Abstract

Nerve transfer is used for brachial plexus injuries but has rarely been applied to repairs in the lower extremities. The aim of this study was to evaluate the feasibility and effectiveness of using the contralateral L-6 nerve root to repair lumbosacral plexus root avulsions. Eighteen rhesus monkeys were randomized into 3 groups. In the experimental group, the left L4-7 and S-1 nerve roots were avulsed and the right L-6 nerve root was transferred to the left inferior gluteal nerve and the sciatic nerve branch innervating the hamstrings. In the control group, the left L4-7 and S-1 nerve roots were avulsed and nerve transfer was not performed. In the sham operation group, the animals underwent a procedure that did not involve nerve avulsion and nerve transfer. Functional outcomes were measured by electrophysiological study, muscle mass investigation, and histological study. The mean amplitudes of the compound muscle action potentials from the gluteus maximus and biceps femoris in the experimental group were higher than those in the control group but lower than those in the sham group (p < 0.05). The muscle mass and myofiber cross-sectional area of these muscles were heavier and larger than those in the control group (p < 0.05). The number of myelinated nerve fibers of the inferior gluteal nerve and the branch of the sciatic nerve innervating the hamstrings in the control group was significantly smaller than the number in the experimental and sham groups (p < 0.01). In this animal model, the contralateral L-6 (analogous to S-1 in humans) nerve root can be used to repair lumbosacral plexus root avulsion.