Sutures bridging nerve defects

A new and simple method for the repair of nerve defects, in which sutures alone are used to guide regeneration between the nerve endings, was developed. Bilateral seven to 17 mm rat sciatic nerve defects were bridged by continuous longitudinal sutures with or without different modifications, by conventional autologous nerve grafts or direct repair under tension as controls. Evaluation was performed from two to 12 weeks postoperatively with routine histology, immunocytochemistry, morphometry, tetanic force measurement and wet weight of the target muscle. I found that both resorbable and non-resorbable sutures supported the formation of a new nerve structure. The sutures appeared to act as an intrinsic framework for fibrin matrix formation which subsequently supported migration of Schwann cells, formation of vessels and axonal regeneration. Although no differences with respect to the regenerative outcome was observed between the two suture types, resorbable sutures were easier to work with. The new nerve structure formed along the sutures was well defined and compartmented. The distribution of a subtype of macrophages (ED2) indicated an importance of these cells for perineurium formation. The number of suture laps bridging a simple nerve defect had some influence on the regeneration process. Bifurcated nerve defects could also be reconstructed successfully by suture guidance. When the muscle bed adjacent to the nerve defect was traumatized, regeneration took place in the suture model, but in some respects in a less favourable way. Axonal counts and recovery of muscle force or weight using the suture model did not differ significantly from those of nerve grafts across seven or 10 mm defects or those of direct repair of a seven mm defect. Regeneration was enhanced when a short nerve segment - a “stepping stone” of Schwann cells – was threaded onto the sutures and centered in the gap. The sutures could be pretreated with Triiodothyronine, T3, as a growth promoting factor to be released during at least three weeks in vitro. In vivo, this release gave rise to an increased myelin area in the regenerating nerve structure. In conclusion, longitudinal sutures can be used to bridge peripheral nerve defects. The model may be of clinical value as a cheap and easily available alternative to nerve grafts or other conduits when dealing with limited nerve defects.