LONG-TERM OUTCOMES OF RAT SCIATIC NERVE INJURY AND ITS GRAFTING WITH SILICON WIRES-BASED CONDUIT: DISTAL NERVE STUMP HISTOLOGY AND ELECTROMYOGRAPHY RESULTS

Abstract

Relevance. The investigations on trauma epidemiology have shown that both combat- and noncombat-related extremity injuries are often accompanied by nerve injuries. These injuries disproportionately affect young healthy civilians and military officers and has a devastating impact on a patients’ quality of life.
 Severe nerve injuries, such as nerve trunk injury in continuity (Sunderland 5), that cannot be treated by neurorraphy without tension, require use of nerve gap bridging strategies with different materials and techniques.
 Objective. This study was aimed to evaluate any positive or negative impact of implanted silicon wires on the quality of nerve fibers at distal nerve stump.
 Materials and Methods. An experiment was performed on 40 male Whistar rats 2-4 month that were divided to the next groups:
 I, (n=10) sham-operated, only surgical access to sciatic nerve was performed.
 II (n=10) with 10 mm sciatic nerve gap that was bridged with autoneurografting.
 III (n=10) with 10 mm nerve gap that was bridged with allogenic decell aorta filled with 4% carboxymethylcellulose hydrogel.
 IV (n=10) with 10 mm nerve gap that was bridged with allogenic decell aorta filled with 4% carboxymethylcellulose hydrogel and aligned p-type silicon microvires.
 Decellularization of allogenic aortas was performed by freeze-thaw cycles.
 Silicon whiskers were fabricated by Vapor-Liquid-Solid (VLS) method in a cold wall Catalytic Chemical Vapor Deposition (Cat-CVD) chamber, pre-cleaned with hydrofluoric acid and sterilized via 180*C dry heat.
 12 weeks after surgery under general anesthesia all rats underwent invasive needle electroneurpmyography with proximal nerve stump stimulation and registration from gastrocnemius muscle. Myograms were recorded and compared by the shape of M-reflex and its amplitude.
 After myography rats were euthanized under thiopentone overdosage and distal stumps of injured sciatic nerves were harvested for light microscopy.
 Sciatic nerve transverse slices were stained with nitric silver by modified Bielschowsky method Nerve fiber diameter, axon diameter, myelin sheath thickness and axon-to-nerve fiber diameter ratio (g-ratio) were measured.
 Results. Performed analysis showed that rats from ІІ and IV groups demonstrated the best quality of nerve fibers in distal nerve stump. That was evidenced by bigger nerve fibers diameter in rats from autologous nerve grafting group and aorta with gel and wires grafting group in comparison with aorta with gel grafting group. Rats from IV demonstrated higher voltage and lower latency of M-reflexes during electromyography.
 Conclusions. It can be concluded about the possible pro-regenerative impact of implanted silicon wires that was evidenced by better nerve fibers quality at distal nerve stump.