Epineurial repair

Cross Section of Epineurium
Transverse section of human tibial nerve. (Epineurium labeled at upper right.)
Nerve structure
Anatomical terminology [edit on Wikidata]

Perineurial repair involves the individual fascicles and placing sutures through the perineurium, the protective sheath surrounding fascicles, the nerve fibers enclosed by the perineurium. Trauma to the nerve by cutting out each fascicle and fibrosis, a build up of tissue as a reaction, that develops due to the dissections and number of sutures is a problem.^[5] Group fasicular repair involves suturing group fascicles in the intraneural epineurium to line up the groups of fascicles. This is only applicable when fascicles are grouped.^[5] Intraneural scarring due to the amount of dissection and manipulation of the repair is a potential result that may counteract the advantage of alignment of the fascicles.^[2]

Epineurial repair was shown to be as good as perineurial repair in acute nerve laceration, a small cut to the nerve, in cats by evaluating the ambulation pattern, fanning of claws and sensation. The objective measures were efficiency, absolute strength and weight of the flexor carpi ulnaris muscle.^[6] The anterior tibial nerves of dogs were cut to determine which of fascicular, interfascicular and epineural suture techniques were best. There was not a significant difference between the results of fascicular and epineural, but a significant difference between the two and interfascicular.^[7] In a study of 18 children with a 2:1 ratio of male to female, the children showed a recovery of motor and sensory functions assessed by the Bruininks–Oseretsky test, a test used to measure motor skills such as balance or cutting out a circle from a piece of paper.^[8][9]

Research for the use of neurotrophic factors such as N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) to aide in the nerve regeneration was started in 2011. Assessments using a grasp test (a test to measure how well an object is grab) were performed weekly for 12 weeks in order to know functional recovery of the flexor muscle (the muscle that is flexed when the end of the finger is brought to the palm) in fingers along with median nerve regeneration. The results showed that MDP with fibrin tissue adhesive (FTA) and epineurial sutures were the best performing group among the sutures and sutures combined with FTA.^[10]

When nerve repair cannot be performed without tension, nerve grafting can be used and is considered the most suitable treatment of peripheral nerve injuries, injuries to nerves outside of the brain and spinal cord. Nerve grafts are used to avoid tension at the proximal and distal ends, to reduce the likelihood of postoperative distraction. A nerve graft will be about 10 percent longer than the gap between the nerves, and the cross-section of the nerve end will be a quite larger than the diameter of the nerve graft to allow for growth. The use of harvested nerve grafts from a donor nerve provider contain Schwann cells and basal lamina endoneurial tubes that provide growth factors and surfaces for molecules to regenerate the axons.^[11]

Sensory loss, scarring and neuroma formation can cause morbidity to the donor site of the patient the nerve is harvested from. Therefore, alloplastic nerve graft research is being conducted for nerve repair. Silicone has been used previously, but long-term use of tubes produces compression and decreased conduction, requiring surgery to remove the tube. Conduits made from polyglycolic acid, a bioabsorbable substance used for dissolvable sutures, reduce the problems associated with silicone and eliminate problems associated with nerve grafts taken from donors. In a study on nerve repair comparing nerve grafts and polyglycolic acid conduits, there was no statistical differences, but 2-point discrimination showed that the conduit group was better at eliminating donor-site morbidity as a result of the graft.^[5]

Nerve tissue loss is associated with the more severe nerve injuries. 50-60% of sensory and motor neurons has been calculated from experiments after the use of nerve grafts Schwann cells form myelin, insulation to the nerve to allow better conduction along the axon, around the nerve fibers and secrete growth factors that play a major role in the regeneration process. The cells can align themselves to provide directional support to the regrowth of axons after injury and possibly increase the level of secretion of growth factors by being modified genetically. The time needed to grow and harvest the cells may be too long for less severe injury because it takes 10 weeks to culture or grow enough.^[12]

Cell therapy to improve nerve regeneration is also being researched. In one study mononuclear cells, cells with one nucleus, were used to repair the sciatic nerve, a large nerve running through the leg to the butt, followed by epineurial repair. Wistar rats were divided into groups of a control, epineurial sutures, medium after suture and injection of 10 microliters of medium into the nerve to allow for growth of cells still there, and mononuclear cells combined with medium after structure in the epineurium region. Results of sciatic functional index, histological and morphometric analyzes showed that the mononuclear group was the best.^[13]