Epineurial sheath tube (EST) technique: an experimental peripheral nerve repair model

Objective: Here we present the epineurial sheath tube (EST) technique as a modified microsurgical rat sciatic nerve model. The EST technique provides a cavity or pouch consisting of an outer epineurial sleeve that has been freed from nerve fascicles. This cavity may be appropriate to test the effectiveness and biocompatibility of implanted growth factors, cell suspensions (embedded in solutions or gels), or bioartificial nerve guide constructs. Methods: A total number of 10 rats underwent the surgical procedure for the EST technique. Cylinders made of fibrin gel served as implants and place-holders. Three animals were euthanized directly after operation, while the others survived for 6 weeks. After immersion fixation (3.9% glutaraldehyde), both conventional histology [semi-thin sections (1 mm), toluidine blue] and scanning electron microscopy were performed. Results: Conventional histology and scanning electron microscopy of samples that had been fixed directly after the surgical procedure displayed the integrity of the closed epineurial tube with the fibrin cylinder in its center. Even after 6 weeks, the outer epineurium was not lacerated, the stitches did not loosen, and the lumen did not collapse, but remained open. Discussion: The practicability of the EST technique could be verified regarding feasibility, reproducibility, mechanical stability, and openness of the lumen. The EST technique can be adapted to other nerve models (e.g. median or facial nerve). It provides a cavity or pouch, which can be used for different neuroscientific approaches including concepts to improve the therapeutic benefit of autologous nerve grafting or therapies to be used as an alternative to autologous nerve grafting.