Repair of peripheral nerve defect with direct gradual lengthening of the proximal nerve stump in rats

Abstract

ABSTRACT:We investigated the effect of direct gradual lengthening on the proximal nerve stump and subsequent nerve regeneration in rats. A 10-mm-long nerve segment was resected from the sciatic nerve of each rat. The proximal nerve stump was directly lengthened at a rate of 1 mm/day using an original external nerve distraction device. Experiment I: After distraction periods of 10, 15, and 20 days, the length of each nerve was evaluated, and the lengthened nerve stump was also examined by immunohistochemical analysis. Experiment II: After a distraction period of 20 days, both nerve stumps were refreshed and direct end-to-end neurorrhaphy was performed. For control, 10-mm nerve grafting was immediately performed after nerve resection. Nerve regeneration was evaluated electrophysiologically and histologically 7, 9, and 15 weeks after nerve resection in both groups. The whole proximal nerve stump, including the endoneurium and the axon, could be lengthened in proportion to the distraction period. There were no significant differences in motor nerve conduction velocity and tetanic muscle contraction force between both groups. Histologically, the total number of myelinated fibers was significantly greater in the nerve lengthening group than in the autografting group. This study demonstrated that the whole proximal nerve stump including the endoneurium and the axon could be lengthened by direct gradual distraction, and that this method might have potential application in the repair of peripheral nerve defects. ß

Gradual stretching of the proximal nerve stump induces the growth of regenerating sprouts in rats

“…6,8,9 In addition to this, our previous study also showed that nerve regeneration after repair of a segmental nerve defect by gradual lengthening of the proximal nerve stump was as good as that of autologous nerve grafting. 6 Thus, primary nerve lengthening might have potential application in the repair of peripheral nerve defects. However, little is known about the effect of direct gradual stretching on the nerve stump.…”

“…As described in our previous study, nerve lengthening was achieved via the stretching of the ring. 6 The stretching was performed at the same time daily while the rats were under sodium pentobarbital (20 mg/kg i.p.) anesthesia.…”

“…Thus, it was indicated that the axonal lengthening occurred at the same rates as those of the nerve stump during gradual stretching. 6 However, the mechanism by which the transected proximal nerve lengthened during the gradual stretching was not clear. Moreover, following the clinical application of leg lengthening in the orthopedic field, it has become well understood that the peripheral nerve could be gradually lengthened without any significant damage during this procedure.…”

“…7 Therefore, primary nerve lengthening has been studied as a new technique for repair of segmental peripheral nerve defects. 6,8,9 Furthermore, recently, an increasing number of studies have demonstrated that repair of nerve defect with gradual nerve lengthening can achieve results comparable to autologous nerve grafting. However, little is known about the mechanism of adaptation of the proximal nerve stump to direct gradual stretching.…”

New treatment for peripheral nerve defects: Reconstruction of a 2 cm, monkey median nerve gap by direct lengthening of both nerve stumps

“…There is much research being conducted to overcome these issues, and we also have developed a nervelengthening method as a new strategy for repair of a segmental peripheral nerve defect. [3][4][5] This method involves grasping both nerve stumps and attaching traction sutures to an external fixator, then using the external fixator to gradually stretch both nerve stumps simultaneously to the point where they can be sutured together. With this nerve-lengthening method, there is only one anastomosis site, a low incidence of nerve stump shape/diameter mismatch, and no interposition of avascular tissue.…”