The outcome of polyethylene glycol fusion augmented by electrical stimulation in a delayed setting of nerve repair following neurotmesis in a rat model

Purpose: Polyethylene glycol is known to improve recovery following its use in repair of acute peripheral nerve injury. The duration till which PEG works remains a subject of intense research. We studied the effect of PEG with augmentation of 20Htz of electrical stimulation (ES) following neurorrhaphy at 48 h in a rodent sciatic nerve neurotmesis model. Method: Twenty-four Sprague Dawley rats were divided into 4 groups. In group I, the sciatic nerve was transected and repaired immediately. In group II, PEG fusion was done additionally after acute repair. In group III, repair and PEG fusion were done at 48 h. In group IV, ES of 20Htz at 2 mA for 1 h was added to the steps followed for group III. Weekly assessment of sciatic functional index (SFI), pinprick, and cold allodynia tests were done at 3 weeks and euthanized. Sciatic nerve axonal count and muscle weight were done. Results: Groups II, III, and IV showed significantly better recovery of SFI (II: 70.10 ± 1.24/III: 84.00 ± 2.59/IV: 74.40 ± 1.71 vs I: 90.00 ± 1.38) (p < 0.001) and axonal counts (II: 4040 ± 270/III: 2121 ± 450/IV:2380 ± 158 vs I: 1024 ± 094) (p < 0.001) at 3 weeks. The experimental groups showed earlier recovery of sensation in comparison to the controls as demonstrated by pinprick and cold allodynia tests and improved muscle weights. Addition of electrical stimulation helped in better score with SFI (III: 84.00 ± 2.59 vs IV: 74.40 ± 1.71) (p < 0.001) and muscle weight (plantar flexors) (III: 0.49 ± 0.02 vs IV: 0.55 ± 0.01) (p < 0.001) in delayed repair and PEG fusions. Conclusion: This study shows that PEG fusion of peripheral nerve repair in augmentation with ES results in better outcomes, and this benefit can be demonstrated up to a window period of 48 h after injury.