Reverse end-to-side neurotization in a regenerating nerve.

Bypass grafting around a neuroma-in-continuity entails coapting a nerve graft above and below the injured segment using two sequential end-to-side repairs. The proximal repair is analogous to what has been classically described as an end-to-side repair; the axons from the intact nerve sprout into the end of a recipient nerve and travel distally. At the distal connection, however, axons in the graft must enter the side of the intact nerve and find their way to appropriate end organs. This process has not been well investigated. To examine this, a reverse end-to-side repair, suturing the distal end of the peroneal nerve to the side of a transected and repaired tibial nerve, was performed in 20 rats. A primary end-to-end repair of the tibial nerve was performed in 10 additional rats. Twelve weeks later, contraction forces of the gastrocnemius muscle were measured following proximal stimulation. Measurements were repeated following elimination of potential axonal pathways to identify which axons (peroneal or tibial) had achieved greater reinnervation. The results indicated that both groups of axons had achieved significant reinnervation. This study supports the idea that a reverse end-to-side repair can result in axonal invasion of an intact but regenerating nerve and achieve functional recovery

Effects of nandrolone on recovery after neurotization of chronically denervated muscle in a rat model.

OBJECT: Suboptimal recovery following repair of major peripheral nerves has been partially attributed to denervation atrophy. Administration of anabolic steroids in conjunction with neurotization may improve functional recovery of chronically denervated muscle. The purpose of this study was to evaluate the effect of the administration of nandrolone on muscle recovery following prolonged denervation in a rat model. METHODS: Eight groups of female Sprague-Dawley rats (15 rats per group, 120 in all) were divided into 3- or 6-month denervated hind limb and sham surgery groups and, then, nandrolone treatment groups and sham treatment groups. Evaluation of treatment effects included nerve conduction, force of contraction, comparative morphology, histology (of muscle fibers), protein electrophoresis (for muscle fiber grouping), and immunohistochemical evaluation. RESULTS: Although a positive trend was noted, neither reinnervated nor normal muscle showed a statistically significant increase in peak muscle force following nandrolone treatment. Indirect measures, including muscle mass (weight and diameter), muscle cell size, muscle fiber type, and satellite cell counts, all failed to support significant anabolic effect. CONCLUSIONS: There does not seem to be a functional benefit from nandrolone treatment following reinnervation of either mild or moderately atrophic muscle (related to prolonged denervation) in a rodent model