Purpose: Peripheral nerve repair is often complicated by connective tissue proliferation, nerve dysfunction, and neuroma formation. Use of bio-absorbable implants in peripheral nerve surgery may improve outcomes of these repairs. The purpose of this study was to histologically compare the incidence of neuroma formation, perineural tissue proliferation, and axon regrowth in transected rat sciatic nerves repaired with and without a tubular collagen nerve protector, NeuraWrapTM.
Methods: Twenty-four Sprague-Dawley rats underwent unilateral sharp sciatic nerve transection and repair with two epineurial sutures and were randomly divided into two groups: Group I, no additional treatment; and Group II, perineurally-placed collagen nerve protector. After three months, the nerves were evaluated for neuroma formation, perineural scarring, fascicular healing, and axon regeneration. Sections were taken at the site of repair and 6mm proximally and distally outside the boundary of the nerve protector. Histolopathologic examination and morphometry was performed on toluidine blue stained sections. Morphometric data was collected on perineural tissue area (including adherent connective tissue); fascicular, axon, and myelinated fiber area; myelinated fibers per nerve; myelinated fiber density; myelin thickness; and G-ratio. The mean data from proximal and distal sections for each nerve were statistically compared between groups.
Results: There were no neuromas identified histologically and all nerves appeared grossly healed. Pilot data of six nerves (3 in each group) revealed no significant difference in total fascicular area (0.78mm2, 0.64mm2), myelinated fibers per nerve (5801, 5374), fiber density (8251 axons/mm2, 8710 axons/mm2), myelin area per nerve (0.189mm2, 0.152mm2), myelinated fiber diameter (6.70µm, 6.25µm), axon diameter (3.34µm, 3.16µm), myelin thickness (1.68µm, 1.55µm), or G-ratio (0.50, 0.51). A mean perineural tissue area of 0.49mm2 was observed in Group I versus 0.29mm2 in Group II (p=0.044). The ratio of perineural tissue area to fascicular area was 0.77 in Group I versus 0.50 for Group II (p=0.001).
Conclusions: Collagen nerve protectors provided similar axonal healing and regeneration compared to traditional suture repair in sharply transected rat sciatic nerves as observed by similar histologic characteristics. Fascicular healing was similar in both groups except that perineural tissue proliferation was inhibited by the presence of a collagen nerve protector. Clinically, the use of a collagen nerve protector following repair of peripheral nerve transection, even if primary repair is possible, results in less perineural fibrosis which may preserve nerve glide and minimize symptoms of traction neuromata.
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