Biomechanical Responses of Neonatal Brachial Plexus to Mechanical Stretch.

Shania Shaji,Anita Singh,Sriram Balasubramanian,Maria Delivoria-Papadopoulos

doi:10.1055/s-0038-1669405

Shania Shaji, Anita Singh + Show 2 more

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https://doi.org/10.1055/s-0038-1669405

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Abstract

This study investigated the biomechanical responses of neonatal piglet brachial plexus (BP) segments—root/trunk, chord, and nerve at two different rates, 0.01 mm/second (quasistatic) and 10 mm/second (dynamic)—and compared their response to another peripheral nerve (tibial). Comparisons of mechanical responses at two different rates reported a significantly higher maximum load, maximum stress, and Young's modulus (E) values when subjected to dynamic rate. Among various BP segments, maximum stress was significantly higher in the nerve segments, followed by chord and then the root/trunk segments except no differences between chord and root/trunk segments at quasistatic rate. E values exhibited similar behavior except no differences between the chord and root/trunk segments at both rates and no differences between chord and nerve segments at quasistatic rate. No differences were observed in the strain values. When compared with the tibial nerve, only mechanical properties of BP nerves were similar to the tibial nerve. Mechanical stresses and E values reported in BP root/trunk and chord segments were significantly lower than tibial nerve at both rates. When comparing the failure pattern, at quasistatic rate, necking was observed at maximum load, before a complete rupture occurred. At dynamic rate, partial rupture at maximum load, followed by a full rupture, was observed. Occurrence of the rate-dependent failure phenomenon was highest in the root/trunk segments followed by chord and nerve segments. Differences in the maximum stress, E values, and failure pattern of BP segments confirm variability in their anatomical structure and warrant future histological studies to better understand their stretch responses.

Highlights

Despite improvements in obstetrical care, neonatal brachial plexus palsy (NBPP) continues to occur in 1.1 to 2.2 per 1,000 births and remains a challenge for the affected families and treating physicians.[1]
This study investigated the biomechanical responses of neonatal piglet brachial plexus (BP) segments—root/trunk, chord, and nerve at two different rates, 0.01 mm/second and 10 mm/second—and compared their response to another peripheral nerve
A major risk factor for NBPP is shoulder dystocia, where the fetal shoulder is impacted against the maternal pubic bone during vaginal birth resulting in stretching of the brachial plexus (BP) nerve or avulsion of its roots.[2,3,4,5,6,7]

Summary

Introduction

Despite improvements in obstetrical care, neonatal brachial plexus palsy (NBPP) continues to occur in 1.1 to 2.2 per 1,000 births and remains a challenge for the affected families and treating physicians.[1] A major risk factor for NBPP is shoulder dystocia, where the fetal shoulder is impacted against the maternal pubic bone during vaginal birth resulting in stretching of the brachial plexus (BP) nerve or avulsion of its roots.[2,3,4,5,6,7] Because in vivo measurements of the exerted forces, the fetal shoulder deformation, and the resulting response of BP are technically difficult, computational and physical models are used to simulate these events.[4,5,7] While the data obtained from these models help demonstrate the effects of forces on the BP, they are based on the nonlinear mechanical properties of the rabbit tibial nerve.[8] BP is a complex structure formed by received February 12, 2018 accepted July 18, 2018.

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