Reconstruction of a 10-mm-long median nerve gap in an ischemic environment using autologous conduits with different patterns of blood supply: A comparative study in the rat

Abstract

The aim of this study was to evaluate in the Wistar rat the efficacy of various autologous nerve conduits with various forms of blood supply in reconstructing a 10-mm-long gap in the median nerve (MN) under conditions of local ischemia. A 10-mm-long median nerve defect was created in the right arm. A loose silicone tube was placed around the nerve gap zone, in order to simulate a local ischemic environment. Rats were divided in the following experimental groups (each with 20 rats): the nerve Graft (NG) group, in which the excised MN segment was reattached; the conventional nerve flap (CNF) and the arterialized neurovenous flap (ANVF) groups in which the gap was bridged with homonymous median nerve flaps; the prefabricated nerve flap (PNF) group in which the gap was reconstructed with a fabricated flap created by leaving an arteriovenous fistula in contact with the sciatic nerve for 5 weeks; and the two control groups, Sham and Excision groups. In the latter group, the proximal stump of the MN nerve was ligated and no repair was performed. The rats were followed for 100 days. During this time, they did physiotherapy. Functional, electroneuromyographic and histological studies were performed. The CNF and ANVF groups presented better results than the NG group in the following assessments: grasping test, nociception, motor stimulation threshold, muscle weight, and histomorphometric evaluation. Radial deviation of the operated forepaw was more common in rats that presented worse results in the other outcome variables. Overall, CNFs and ANVFs produced a faster and more complete recovery than NGs in the reconstruction of a 10-mm-long median nerve gap in an ischemic environment in the Wistar rat. Although, results obtained with CNFs were in most cases were better than ANVFs, these differences were not statistically significant for most of the outcome variables.

Functional and Physiological Methods of Evaluating Median Nerve Regeneration in the Rat

“…Similarly, although several authors use walking track analysis to evaluate forelimb nerve repair in the rat, other authors argue that single MN lesions frequently fail to produce reproducible changes in pawprints 10,58,59 . Furthermore, some have stated that these changes may not be proportional to muscle recovery 10,60 .…”

“…Similarly, although several authors use walking track analysis to evaluate forelimb nerve repair in the rat, other authors argue that single MN lesions frequently fail to produce reproducible changes in pawprints 10,58,59 . Furthermore, some have stated that these changes may not be proportional to muscle recovery 10,60 . Bearing this in mind, some researchers have advocated the use of walking track analysis in the forepaw mainly when assessing recovery after crushing neve lesions rather than after segmental nerve reconstruction 10,50,61 .…”

“…Furthermore, some have stated that these changes may not be proportional to muscle recovery 10,60 . Bearing this in mind, some researchers have advocated the use of walking track analysis in the forepaw mainly when assessing recovery after crushing neve lesions rather than after segmental nerve reconstruction 10,50,61 .…”

“…Furthermore, it is difficult to distinguish between the strength generated by the digital flexor muscles (solely innervated by the MN in the rat and the object of the Grasping Test 9 ) from the strength produced by the wrist flexors, which include the flexor carpi ulnaris that receives its innervation from the ulnar nerve 9,10,27 . In order to try to circumvent these potential biases, this protocol uses an ordinal scale similar to the Medical Research Council Scale commonly used to grade muscle strength in humans 10,11,62 . Alternatively, other authors have described detailed assessment of grasping using video analysis and a video-based scoring system 11,63 .…”

“…The weight and morphology of the flexor carpis radialis muscle were dependent on MN recovery, as this muscle is innervated exclusively by the MN 9,10 . Thus, normal weight and morphology were observed in the Sham group.…”