A new technique in peripheral nerve repair: establishment of a new neurovascular relationship in the repair line (Neo-neurovascularization) and its effect on nerve recovery and muscle atrophy

Peripheral nerve injuries and their repair techniques are one of the most emphasized issues in the field of plastic surgery today. The gold standard form of repair recommended for a nerve cut is tension-free coaptation. But this is not always the method that can be applied. Although nerve autograft is the gold standard method recommended for defected nerve injuries, the results obtained with this method are not optimal. Alternatively, vein conduits, artificial conduits, mesenchymal stem cell or VEGF supported conduits have been tried. The main limitation of nerve grafts or other conduits is the lack of their own vascular supply. For this reason, pedicled, prefabricated and free nerve flaps were also tried. These flaps showed superior results than normal nerve grafts. However, they also have disadvantages such as requiring microsurgical anastomosis, limited flap options and the risk of developing thrombosis. In this study, we aimed to vascularize the repair line of the repaired nerve by re-creating the neurovascular relationship with the adjacent brachial artery and to investigate its effect on both histological and functional recovery. In this study, we investigated the newly defined technique on a total of 42 rats, on 7 groups, with 7 rats in each group. Group 1 (Sham): It consisted of the left median nerves of Group 2 and did not undergo any surgical procedure. Group 2 (control): the median nerves in this group were cut and repaired as primary coaptation. Group 3 (nerve graft): A segment of 7 mm was removed from the median nerves in this group and reversed and coapted to the proximal and distal stumps of the nerve. Group 4 (vein graft): 7 mm segment from the median nerves in this group was removed, the defect was repaired with a vein graft taken from the external jugular vein. Group 5 (primary coaptation + arterialization): median nerves in this group were fixed to the brachial artery at three points after primary coaptation. Group 6 (nerve graft + arterialization): Unlike Group 3, in this group the nerve graft was fixed to the brachial artery, the median nerve also was fixed proximal and distal to the repair line. Group 7 (vein graft + arterialization): Unlike Group 4, in this group the vein graft was fixed to the brachial artery, the median nerve also was fixed proximal and distal to the repair line The weights of all animals were recorded before starting the study. Two weeks after the experiment, nocisecptive stimulus, Von Frey and grasping strength tests were checked weekly. The study was terminated at week 13. Before terminating the study, animals were reweighed, Gait-walk test and EMG tests were performed. The brachial arteries of the rats were catheterized to ensure the passage of the vessels and to check the pulse and blood pressure values while taking the samples. Then, the FCR muscle weights of the rats were recorded. For histopathological and immunohistochemical evaluation, only the nerves of the first 4 groups and the nerves of the other groups together with their arteries were taken as en-bloc. In the grasping strength test, a significant difference was found starting from the 8th week in Group 3-6 comparison, and from the 7th week in Group 3-7 (p<0.05). A significant difference was found at the 4th week in the group 4-5 comparison, and at the 5th week in the group 4-6 comparison (p<0.05). In group 4-7 comparison, a significant difference was detected starting from the 6th week (p<0.05). No significant difference was found in other comparisons (p>0.05). In the Von Frey test, a significant difference was found in Group 2-4 and Group 4-6 comparisons starting from the 5th week (p<0.05). Group 3-5, group 4-5, group 5-7 and group 6-7 comparisons showed a significant difference starting from the 9th week (p<0.05). Group 3-6, group 3-7 and group 4-7 comparisons showed a significant difference from the 8th week (p<0.05). There was a significant difference in inflammation, fibrosis and asconal degeneration between the nerve grafting groups (group 3 and group 6) (p<0.05). Group 3 showed more inflammation, fibrosis and axonal degeneration with mean values of 1.57, 2.14 and 1, respectively. A statistically significant difference was found between the vein grafted groups (group 4 and group 7) in terms of fibrosis, axonal degeneration, fiber count, myelination, disorganization and S100 staining intensity (p<0.05). There was no statistically significant difference in muscle weight, animal weight, walking test and EMG test (p>0.05). In conclusion, vascularizing the repair line provided better functional and histological recovery in nerve graft and vein graft. Consistent with the literature, vascularized grafts showed earlier and full functional recovery than non-vascularized grafts. Sensory recovery was the same as for the nerve that had no surgery at Week 12. The technique we describe, unlike the vascularization techniques performed in the literature, does not require microsurgical anastomosis, does not carry the risk of thrombosis, and other nerve conduits such as ven grafts can be vascularized with this technique.