Reinnervation of Skeletal Muscle: A Comparison of Nerve Implantation with Neuromuscular Pedicle Transfer in an Animal Model

Abstract

In recent years there has been increased interest in the possibility of reinnervating paralyzed muscles, particularly the muscles of the face and of the larynx. There has been dispute over the relative effectiveness of different approaches. This study was undertaken to compare direct nerve implantation with the transfer of a neuromuscular pedicle using denervated strap muscles in a rabbit model. Reinnervation was carried out both immediately after denervation and after a delay period. Evidence of return of function was obtained by a method of long-term electromyographic monitoring and was confirmed electrically by evoked electromyography and muscle tension measurement and histologically by brain stem uptake of horseradish peroxidase. Both methods of nerve transfer produced consistently functional neuromuscular units, with physiological activity and muscle strength comparable with those in normally innervated controls. Return of function was apparent within 6 weeks of both nerve implantation and neuromuscular transfer; with this model, neither method showed a clear advantage over the other.

Muscle reinnervation with nerve-muscle-endplate band grafting technique: correlation between force recovery and axonal regeneration

“…Muscle force measurement is widely used to assess the mechanical function and contractile properties of a muscle [35–41]. Our studies [28,30–33] and others [23,25,42,43] have demonstrated that force measurement is a reliable technique in determining the degree of functional recovery of a reinnervated muscle. The denervated muscle is characterized by reduced muscle mass, decreased fiber size, increased connective tissue, and reduced metabolic capacity [44,45] which can be reversed by reinnervation [28,33,46].…”

“…The only reconstructive option to reinnervate that muscle is direct nerve implantation (i.e., muscular neurotization) [17,18] or nerve-muscle pedicle (NMP) transfer. The NMP technique has been used for laryngeal [19–22] and facial reinnervation [23–25]. However, controversy exists concerning the success rate of the NMP method.…”

Nerve-Muscle-Endplate Band Grafting

“…In 1980's, Cummings and colleagues applied the NMP technique to facial reinnervation in animal experiments. 72-74 Clearly, this method has been employed primarily to treat paralyzed larynx and face. Up to date, many studies on the NMP reinnervation procedure have been reported in the literature over the past 40 years.…”

“…Some investigators 45,72,73 performed animal experiments to compare direct nerve implantation (DNI) with NMP using strap muscles such as SH and ST in rabbits. They found that neither method had a clear advantage over the other, at least in terms of function.…”

“…Studies showed that NMP transfer resulted in functional outcomes similar to the DNI when evaluated by electromyography (EMG) and muscle tension. 72,74 NMP technique has been hampered by the fact that the muscle pedicle is harvested at the motor point (entry of the nerve into the muscle) where a nerve branch enters the muscle without considering the MEP band and nerve terminals. Some authors felt it probable that the small NMP might in fact contain cut ends of the nerve that acted in a fashion similar to that of a DNI.…”