Experimental Biomechanics of Neonatal Brachial Plexus Avulsion Injuries Using a Piglet Model

Abstract

Background: A brachial plexus avulsion occurs when the nerve root separates from the spinal cord during birthing trauma, such as shoulder dystocia or a difficult vaginal delivery. A complete paralysis of the affected levels occurs post-brachial plexus avulsion. Despite being reported in 10-20% of brachial plexus birthing injuries, it remains poorly diagnosed during the acute stages of injury, leading to poor intervention approaches. The poor diagnosis of brachial plexus avulsion injury can be attributed to the currently unavailable biomechanics of brachial plexus avulsion. While the biomechanical properties of neonatal brachial plexus are available, the forces required to avulse a neonatal brachial plexus remain unknown.

Methods: This study aims to provide detailed biomechanics of the required forces and corresponding strains for neonatal brachial plexus avulsion. Biomechanical tensile testing was performed on an isolated, clinically relevant piglet spinal cord and brachial plexus complex, and the required avulsion forces and strains were measured.

Results: The reported failure forces and corresponding strains were 3.9 ± 1.6 N at a 27.9 ± 6.5% strain, respectively.

Conclusion: The obtained data are required to understand the avulsion injury biomechanics and provide the necessary experimental data for computational model development that serves as an ideal surrogate for understanding complicated birthing injuries in newborns.

Keywords: avulsion; biomechanics; birthing; brachial plexus; load; neonatal; palsy; strain; stretch.

Figure 1

Study flowchart detailing a summary of the steps involved in this study.

Figure 2

Biomechanical testing setup details. The custom-built setup includes a control box, load cell, actuator, and clamps. A 3D camera system placed above the testing sample acquired the images for the strain analysis.

Figure 3

Biomechanical testing of the spinal cord–BP complex. Ink markers placed on the spinal cord adjacent to the rootlets and root/trunk segment of the BP were tracked for strain analysis.

Figure 4

Avulsion strains (%) reported in the tested upper, middle, and lower trunks of the BP segments.

Figure 5

Avulsion loads (N) reported in the tested upper, middle, and lower trunks of the BP segments. *: p < 0.05 indicates a significant difference between the groups.