Methods for In Vivo Biomechanical Testing on Brachial Plexus in Neonatal Piglets

Summary

Presented here are methods to perform in vivo biomechanical testing on brachial plexus in a neonatal piglet model.

Abstract

Neonatal brachial plexus palsy (NBPP) is a stretch injury that occurs during the birthing process in nerve complexes located in the neck and shoulder regions, collectively referred to as the brachial plexus (BP). Despite recent advances in obstetrical care, the problem of NBPP continues to be a global health burden with an incidence of 1.5 cases per 1,000 live births. More severe types of this injury can cause permanent paralysis of the arm from the shoulder down. Prevention and treatment of NBPP warrants an understanding of the biomechanical and physiological responses of newborn BP nerves when subjected to stretch. Current knowledge of the newborn BP is extrapolated from adult animal or cadaveric BP tissue instead of in vivo neonatal BP tissue. This study describes an in vivo mechanical testing device and procedure to conduct in vivo biomechanical testing in neonatal piglets. The device consists of a clamp, actuator, load cell, and camera system that apply and monitor in vivo strains and loads until failure. The camera system also allows monitoring of the failure location during rupture. Overall, the presented method allows for a detailed biomechanical characterization of neonatal BP when subjected to stretch.

Introduction

Despite recent advances in obstetrics, the problem of NBPP caused by stretch injury to the BP complex continues to be a global health burden, with an incidence of 1.5 cases per 1,000 live births^1,2. Associated risk factors can be maternal (i.e., excessive weight, maternal diabetes, uterine abnormalities, history of BP paralysis), fetal (i.e., fetal macrosomia), or birth-related (i.e., shoulder dystocia, prolonged labor, assisted delivery with forceps or vacuum extractors, breech presentation³). While these complications are unavoidable in certain circumstances, prevention and treatment ....

Protocol

Institutional Animal Care and Use Committee at Drexel University approved all procedures (#20704).

1. Animal Arrival and Acclimation

1. Quarantine 1–2 day-old piglets for at least 24 h after arrival.
2. House piglets in clean and sanitized stainless-steel cages (36 in x 48 in x 36 in) on aspen chip bedding and feed ad libitum with pig milk replacer.
3. Maintain the room temperature at 85 °F to ensure a thermo-neutral environment.

Discussion

Available literature on the biomechanical responses of stretch on the BP tissue exhibit a wide range of threshold values as well as methodological discrepancies^{4,6,8,18,19,20,21,22,23}. Variations in published results could.......

Materials

Name	Company	Catalog Number	Comments
Omega Subminature Tension & Compression Load Cell	Omega	LCM201-200N	200N load cell
Basler acA640-120uc camera	Basler	acA640-120uc
Feedback Linear Actuator	Progressive Automations	PA-14P	10" stroke, 150lb force, 15mm/s speed
Motion Tracking Software	Kinovea	N/A	Open Source
Proramming Software - MATLAB	Mathworks	N/A	version 2018A
Surgical instruments
Forceps	Fine Science Tools Inc	11006-12 and 11027-12 or 11506-12
Hemostats	Fine Science Tools Inc	13009-12
Scissors	Fine Science Tools Inc	14094-11 or 14060-09