Characterizing the viscoelastic behavior of neonatal peripheral nerves is critical in understanding stretch-related peripheral nerve injuries (PNIs) in neonates. This study investigated the in-vitro viscoelastic stress relaxation response of neonatal piglet brachial plexus (BP) and tibial nerves at two different strain levels (10% and 20%) and stress relaxation testing durations (90- and 300-seconds). BP and tibial nerves from 20 neonatal piglets were harvested and pre-stretched to either 10% or 20% strain at a dynamic rate of 100 mm/min to simulate conditions, such as shoulder dystocia, that may lead to stretch-related PNIs in neonates. At constant strain, the reduction in stress was recorded for 90- or 300-seconds. The biomechanical data were then fit to a viscoelastic model to acquire the short- and long-term stress relaxation time-constants. Though no significant differences in the degree of stress relaxation were found between the two tested strain levels after 90 seconds in both nerve types, reduction in stress was moderately greater (p = 0.056) at 10% strain than at 20% for BP after 300 seconds. The reduction in stress was significantly higher in nerves subjected to a 300 second testing duration than 90 second for both strain levels and nerve types. When comparing BP and tibial nerve stress relaxation response, BP nerve relaxed significantly more than tibial at both strain levels after 90 seconds, but no significant differences were observed after 300 seconds. Our results confirm that neonatal peripheral nerve tissue is highly viscoelastic. These novel biomechanical data can be incorporated into finite element and computational models studying neonatal PNIs.

表征新生儿周围神经的粘弹性行为对于理解新生儿与牵张相关的周围神经损伤 (PNI) 至关重要。本研究调查了体外新生仔猪臂丛神经 (BP) 和胫神经在两种不同应变水平（10% 和 20%）和应力松弛测试持续时间（90 秒和 300 秒）下的粘弹性应力松弛反应。采集 20 头新生仔猪的 BP 和胫神经，并以 100 毫米/分钟的动态速率预拉伸至 10% 或 20% 应变，以模拟可能导致新生儿拉伸相关 PNI 的情况，例如肩难产. 在恒定应变下，记录应力减少 90 或 300 秒。然后将生物力学数据拟合到粘弹性模型以获得短期和长期应力松弛时间常数。尽管在 90 秒后两种神经类型的两种测试应变水平之间没有发现压力松弛程度的显着差异，但压力减轻程度略大（p = 0.056)在 10% 应变下比在 20% BP 下 300 秒后。对于应变水平和神经类型，经受 300 秒测试持续时间的神经的压力减少明显高于 90 秒。当比较 BP 和胫神经应力松弛反应时，在 90 秒后，BP 神经在两个应变水平上的松弛明显多于胫骨，但在 300 秒后没有观察到显着差异。我们的结果证实新生儿周围神经组织是高度粘弹性的。这些新的生物力学数据可以纳入研究新生儿 PNI 的有限元和计算模型。