Helicoid end-to-side and oblique attachment technique in repair of the musculocutaneous nerve injury with the phrenic nerve as a donor: An experimental study in rats

Comparison of End-to-End Technique, Helicoid Technique, and Modified Helicoid Weave Repair Technique in a Rat Sciatic Nerve Model: A Pilot Study

Background

The gold standard for nerve repair is end-to-end (ETE) repair. Helicoid technique (HT) has also been previously described. In this pilot study, HT was compared to ETE and a modified helicoid weave technique (MHWT). In MHWT, recipient nerve is passed through rather than around the donor nerve, allowing for greater nerve-to-nerve interaction.

Methods

Eighteen adult male Lewis rats received a 2-cm sciatic nerve transection and were divided into three groups: ETE, HT, and MHWT. Five months later, electromyography (EMG), tetanic force of contraction, and wet weight of the extensor digitorum longus muscle were recorded in both the operated and non-operated sides. Nerve biopsies were taken proximal and distal to the site of the nerve graft for histological examination.

Results

One rat died following repair surgery and three rats died during the second surgery. The mean threshold of stimulation for ETE, HT, and MHWT were 183.3 µA, 3707.5 µA, and 656.6 µA, respectively. EMG analysis revealed that latency and duration are both affected by surgical repair type and injured or uninjured conditions. Threshold ratio (injured:non-injured) revealed pilot-level significant differences between HT and both MHWT (p = 0.069) and ETE (p = 0.082). Nerve biopsy demonstrated fascicles distally in all three groups.

Conclusions

While HT and MHWT function as a nerve repair technique, they are not superior to ETE. ETE remains the gold standard for nerve repair. While mean values were in favor of ETE, no statistical significance was attained.

End-to-side neurotization with the phrenic nerve in restoring the function of toe extension: an experimental study in a rat model

The phrenic nerve being transferred to the posterior division of the lower trunk with end-to-end neurorrhaphy is reported to be effective in restoring the function of digit extension in literature. However, the phrenic nerve is extremely important in respiration. We designed an animal experiment to discover whether the phrenic nerve being transferred to the posterior division of the lower trunk with end-to-side neurotization was feasible and provided the theoretical basis. A sum of 36 Sprague-Dawley rats was randomly assigned to one of two groups. In Group A, the phrenic nerve was transferred to the posterior division of the lower trunk with end-to-side neurotization. In Group B, the posterior division of the lower trunk was directly sutured. The results of behavioral assessment, electrophysiology, histology and nerve fiber count and muscle weight at 12 weeks postoperatively were recorded. In Group A, none of the rats experienced tachypnea. The motion of slight toe extension was observed. The results of electrophysiology, histology and nerve fiber count and muscle weight in Group A were not as well as those of Group B, but gradually improved with time. The phrenic nerve being transferred to the posterior division of lower trunk with end-to-side neurotization can partially restore the function of toe extension in a rat model. Whether the function of digit extension can be restored by the phrenic nerve with end-to-side neurotization in humans still needs more practice in clinic.

Repair of the musculocutaneous nerve using the vagus nerve as donor by helicoid end-to-side technique: an experimental study in rats

Although several donor nerves can be chosen to repair avulsed brachial plexus nerve injury, available nerves are still limited. The purpose of this study is to validate whether the vagus nerve (VN) can be used as a donor. Eighteen Sprague-Dawley male rats were divided into three groups (n = 6). The right musculocutaneous nerve (McN) was transected with differing subsequent repair. (1) HS-VN group: a saphenous nerve (SN) graft-end was helicoidally wrapped round the VN side (epi-and perineurium was opened) with a 30 ° angle, distal SN end was coapted to the McN with end-to-end repair. (2) EE-PN group: a SN was interpositionally grafted between the transected phrenic nerve (PN) and the McN by end-to-end coaptation. (3) Sham control group: McN was transected and not repaired and postoperative vital signs were checked daily. At three months, electrophysiology, tetanic force, wet biceps muscle weight, and histology were evaluated. Every tested mean value in HS-VN group was significantly greater than the EE-PN or the sham control groups (p < 0.05 or p < 0.005). The mean recovery ratio of regenerated nerve fibers was 96% and, in HS-VN group, the mean recovery ratio of CMAP was 79%. No vital signs changed in any group. There was no statistical difference (p > 0.5) between the mean VN nerve-fiber numbers of the segments proximal (2237 ± 134) and distal (2150 ± 156) to the VN graft-attachment site. Histological analysis revealed no axon injury or intraneural scarring at any point along the VN. This study demonstrated that VN is a practical and reliable donor nerve for end-to-side nerve transfer. © 2017 Wiley Periodicals, Inc.

Novel Atraumatic End-to-Side Repair Model Exhibits Robust Collateral Sprouting Independent of Donor Fiber Injury

BACKGROUND

A central issue underlying end-to-side neurorrhaphy technique is whether injury to the donor nerve fibers is necessary for successful reinnervation of the recipient nerve. To address this question, the authors developed a novel atraumatic end-to-side neurorrhaphy model that uses the preexisting anatomical structure of the median nerve as the Y-chamber to study the mechanism of collateral sprouting.

METHODS

In this rat forelimb model, the authors transected the musculocutaneous nerve and the lateral head of the median nerve, and coapted their distal stumps together. In this model, the authors use the medial head of the median nerve as the donor nerve, and the lateral head of the median nerve (distal stump) as a Y-shaped chamber, which provided structural connection to the recipient musculocutaneous nerve in end-to-side fashion.

RESULTS

Three months after surgery, converging histologic, electrophysiologic, and behavioral observations confirmed the successful reinnervation of the recipient nerve. Retrograde labeling indicated that sensory fibers exhibited greater collateral sprouting than observed for motor fibers. Interestingly, fluorescence of these collateral sprouting fibers was present only when the median nerve lateral head was attached to the musculocutaneous nerve of the biceps, indicating that factors derived from the denervated tissue likely induced the collateral sprouting in this model.

CONCLUSIONS

The authors' findings provide strong evidence that collateral sprouting can be robustly initiated independent of donor nerve fiber injury. The authors' model can accelerate the understanding of the mechanism underlying end-to-side neurorrhaphy and the optimization of its clinical use.

Epineurial Window Is More Efficient in Attracting Axons than Simple Coaptation in a Sutureless (Cyanoacrylate-Bound) Model of End-to-Side Nerve Repair in the Rat Upper Limb: Functional and Morphometric Evidences and Review of the Literature

End-to-side nerve coaptation brings regenerating axons from the donor to the recipient nerve. Several techniques have been used to perform coaptation: microsurgical sutures with and without opening a window into the epi(peri)neurial connective tissue; among these, window techniques have been proven more effective in inducing axonal regeneration. The authors developed a sutureless model of end-to-side coaptation in the rat upper limb. In 19 adult Wistar rats, the median and the ulnar nerves of the left arm were approached from the axillary region, the median nerve transected and the proximal stump sutured to the pectoral muscle to prevent regeneration. Animals were then randomly divided in two experimental groups (7 animals each, 5 animals acting as control): Group 1: the distal stump of the transected median nerve was fixed to the ulnar nerve by applying cyanoacrylate solution; Group 2: a small epineurial window was opened into the epineurium of the ulnar nerve, caring to avoid damage to the nerve fibres; the distal stump of the transected median nerve was then fixed to the ulnar nerve by applying cyanoacrylate solution. The grasping test for functional evaluation was repeated every 10-11 weeks starting from week-15, up to the sacrifice (week 36). At week 36, the animals were sacrificed and the regenerated nerves harvested and processed for morphological investigations (high-resolution light microscopy as well as stereological and morphometrical analysis). This study shows that a) cyanoacrylate in end-to-side coaptation produces scarless axon regeneration without toxic effects; b) axonal regeneration and myelination occur even without opening an epineurial window, but c) the window is related to a larger number of regenerating fibres, especially myelinated and mature, and better functional outcomes.