Sensory Nerve Cross-Anastomosis and Electrical Muscle Stimulation Synergistically Enhance Functional Recovery of Chronically Denervated Muscle

BACKGROUND: Long-term muscle denervation leads to severe and irreversible atrophy coupled with loss of force and motor function. These factors contribute to poor functional recovery following delayed reinnervation. The authors' previous work demonstrated that temporarily suturing a sensory nerve to the distal motor stump (called sensory protection) significantly reduces muscle atrophy and improves function following reinnervation. The authors have also shown that 1 month of electrical stimulation of denervated muscle significantly improves function and reduces atrophy. In this study, the authors tested whether a combination of sensory protection and electrical stimulation would enhance functional recovery more than either treatment alone. METHODS: Rat gastrocnemius muscles were denervated by cutting the tibial nerve. The peroneal nerve was then sutured to the distal tibial stump following 3 months of treatment (i.e., electrical stimulation, sensory protection, or both). Three months after peroneal repair, functional and histologic measurements were taken. RESULTS: All treatment groups had significantly higher muscle weight (p<0.05) and twitch force (p<0.001) compared with the untreated group (denervated), but fiber type composition did not differ between groups. Importantly, muscle weight and force were significantly greater in the combined treatment group (p<0.05) compared with stimulation or sensory protection alone. The combined treatment also produced motor unit counts significantly greater than sensory protection alone (p<0.05). CONCLUSIONS: The combination treatment synergistically reduces atrophy and improves reinnervation and functional measures following delayed nerve repair, suggesting that these approaches work through different mechanisms. The authors' research supports the clinical use of both modalities together following peripheral nerve injury.