Microscale Electrode Implantation during Nerve Repair: Effects on Nerve Morphology, Electromyography, and Recovery of Muscle Contractile Function

Background: The authors' goal is to develop a peripheral nerve electrode with long-term stability and fidelity for use in nerve/machine interfaces. Microelectromechanical systems use silicon probes that contain multichannel actuators, sensors, and electronics. The authors tested the null hypothesis that implantation of microelectromechanical systems probes does not have a detrimental effect on peripheral nerve function or regeneration. Methods: A rat hind-limb, peroneal nerve model was used in all experimental groups: intact nerve (control group, n = 10); nerve division and repair (repair group, n = 9); and nerve division, insertion of microelectromechanical systems probe, and repair (repair plus probe group, n = 9). Nerve morphology, nerve to compound muscle action potential studies, walking tracks, and extensor digitorum longus muscle function tests were evaluated following an 80-day recovery. Results: Repair and repair plus probe showed no differences in axon count, axon size, percentage nonneural area, compound muscle action potential amplitude, latency, muscle mass, muscle force, or walking track scores. Although there was some local fibrosis around each microelectromechanical systems probe, this did not lead to measurable detrimental effects in any anatomical or functional outcome measurements. Conclusion: The absence of a significant difference between the repair and the repair plus probe groups regarding histology, compound muscle action potential, walking tracks, and muscle force suggests that microelectromechanical systems electrodes are compatible with regenerating axons and show promise for establishing chemical and electrical interfaces with peripheral nerves.