Resorbable Nerve Wraps: Can They Be Overtightened?

Abstract

Nerve wrapping has been advocated to minimize scarring and adhesion following neurorrhaphy or neurolysis. A wrap should provide an enclosure that is snug enough to protect and support the affected nerve without strangulating the nerve. The degree to which resorbable wraps should be ": tightened" around the nerve is largely subjective with scant literature on the subject. The purpose of this study was to evaluate the effects of tightly fitting resorbable nerve wraps around intact rat sciatic nerves. Twenty-four Sprague-Dawley rats underwent exposure and circumferential measurement of the right sciatic nerve. Porcine-derived extracellular matrix (ECM) wraps were trimmed and sutured to enclose the nerve with a tight (same as that of the nerve, n = 8) or loose (2.5x that of the nerve, n = 8) circumference. Sham-surgery control animals (n = 8) had no wrap treatment. Functional outcome was recorded biweekly by sciatic functional index (SFI) with walking track analysis and electrical stimulation. Animals were sacrificed at 12 weeks for histologic analyses. No withdrawal response could be evoked in the tight-wrap group until week 9, while significant improvement in SFI first occurred between weeks 5 and 7. By week 12, the tight-wrap group required 60% more current compared with baseline stimulation to produce a withdrawal response. They recovered 81% of SFI baseline values but also demonstrated significantly greater intraneural collagen content (p < 0.001) and lower axon density (p < 0.05) than in the loose-wrap and sham groups. The loose-wrap group had comparable functional and histologic outcomes to the sham control group. Resorbable ECM nerve wraps applied tightly around intact rat sciatic nerves caused significant functional impairment and histological changes characteristic of acute nerve compression. Significant but incomplete functional recovery was achieved by the tight-wrap group after 12 weeks, but such recovery may not apply in humans.