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1. Available Computational and Physical Models to Understand the Mechanisms of Neonatal Brachial Plexus Injury During Shoulder Dystocia

   Singh, Anita (January 2019, Open access journal of neurology neurosurgery)

   Neonatal brachial plexus palsy is a devastating complication occurring during complicated birthing scenarios including shoulder dystocia. To understand the effects of maneuvers that reduce forces required for delivery following shoulder dystocia, tools that simulate the birthing scenarios are needed. Incorporation of brachial plexus responses is further required to help understand the mechanism of neonatal brachial plexus palsy and devise strategies that can help prevent them. Given the inability to measure forces and tissue strains during actual birthing process, computer and physical models serve as optimal tools with its known limitations. This mini-review highlights and summaries available computational and physical models that can help understand brachial plexus injury mechanisms in neonates following complicated delivery including shoulder dystocia. 

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2. A Systematic Review of the Tensile Biomechanical Properties of the Neonatal Brachial Plexus

   https://doi.org/10.1115/1.4051399  

   Orozco, Virginia; Magee, Rachel; Balasubramanian, Sriram; Singh, Anita (June 2021, Journal of Biomechanical Engineering)

   null (Ed.)

   Abstract Brachial plexus birth injury has a reported incidence of 1 to 4 per 1000 live births. During complicated deliveries, neonatal, maternal, and other birth-related factors can cause over-stretching or avulsion of the neonatal brachial plexus leading to injury. Understanding biomechanical responses of the neonate brachial plexus when subjected to stretch can offer insight into the injury outcomes while guiding the development of preventative maneuvers that can help reduce the occurrence of neonatal brachial plexus injuries. This review article aims to offer a comprehensive overview of existing literature reporting biomechanical responses of the brachial plexus, in both adults and neonates, when subjected to stretch. Despite the discrepancies in the reported biomechanical properties of the brachial plexus, the studies confirm the loading rate and loading direction dependency of the brachial plexus tissue. Future studies, possibly in vivo, that utilize clinically-relevant neonatal large animal models can provide translational failure values of the biomechanical parameters for the neonatal brachial plexus when subjected to stretch. 

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3. An in vitro Study to Investigate Biomechanical Responses of Peripheral Nerves in Hypoxic Neonatal Piglets

   https://doi.org/10.1115/1.4051283  

   Singh, Anita; Magee, Rachel; Balasubramanian, Sriram (May 2021, Journal of Biomechanical Engineering)

   null (Ed.)

   Abstract Despite occurrence of neonatal hypoxia and peripheral nerve injuries in complicated birthing scenarios, the effect of hypoxia on the biomechanical responses of neonatal peripheral nerves is not studied. In this study, neonatal brachial plexus and tibial nerves, obtained from eight normal and eight hypoxic 3-5 days old piglets, were tested in uniaxial tension until failure at a rate of 0.01 mm/s or 10 mm/s. Failure load, stress, and modulus of elasticity were reported to be significantly lower in hypoxic neonatal brachial plexus (BP) and tibial nerves than respective normal tissue at both 0.01 and 10 mm/s rates. Failure strain was significantly lower in the hypoxic neonatal BP nerves only at 10 mm/s rate when compared to normal BP nerve. This is the first available data that indicates weaker mechanical behavior of hypoxic neonatal peripheral nerves as compared to normal tissue, and offers an understanding of the biomechanical responses of peripheral nerves of hypoxic neonatal piglets. 

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4. A Quantitative Study of Transport of Surfactant Boli in a Three-Dimensional Lung Model of Neonates

   https://doi.org/10.1115/1.4055428  

   Combs, Hannah; Shark, Taylor; Heiss, Jacob; Raessi, Mehdi; Tavana, Hossein (October 2022, Journal of Biomechanical Engineering)

   Abstract Neonatal respiratory distress syndrome is mainly treated with the intratracheal delivery of pulmonary surfactants. The success of the therapy depends on the uniformity of distribution and efficiency of delivery of the instilled surfactant solution to the respiratory zone of the lungs. Direct imaging of the surfactant distribution and quantifying the efficiency of delivery is not feasible in neonates. To address this major limitation, we designed an eight-generation computational model of neonate lung airway tree using morphometric and geometric data of human lungs and fabricated it using additive manufacturing. Using this model, we performed systematic studies of delivery of a clinical surfactant either at a single aliquot or at two aliquots under different orientations of the airway tree in the gravitational space to mimic rolling a neonate on their side during the procedure. Our study offers novel insights into effects of the orientation of the lung airways and presence of a pre-existing surfactant film on how the instilled surfactant solution distributes in airways. 

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5. Effects of Prestretch on Neonatal Peripheral Nerve: An In Vitro Study

   https://doi.org/10.1055/s-0042-1743132  

   Singh, Anita; Majmudar, Tanmay; Magee, Rachel; Gonik, Bernard; Balasubramanian, Sriram (January 2022, Journal of Brachial Plexus and Peripheral Nerve Injury)

   Abstract Background Characterizing the biomechanical failure responses of neonatal peripheral nerves is critical in understanding stretch-related peripheral nerve injury mechanisms in neonates. Objective This in vitro study investigated the effects of prestretch magnitude and duration on the biomechanical failure behavior of neonatal piglet brachial plexus (BP) and tibial nerves. Methods BP and tibial nerves from 32 neonatal piglets were harvested and prestretched to 0, 10, or 20% strain for 90 or 300 seconds. These prestretched samples were then subjected to tensile loading until failure. Failure stress and strain were calculated from the obtained load-displacement data. Results Prestretch magnitude significantly affected failure stress but not the failure strain. BP nerves prestretched to 10 or 20% strain, exhibiting significantly lower failure stress than those prestretched to 0% strain for both prestretch durations (90 and 300 seconds). Likewise, tibial nerves prestretched to 10 or 20% strain for 300 seconds, exhibiting significantly lower failure stress than the 0% prestretch group. An effect of prestretch duration on failure stress was also observed in the BP nerves when subjected to 20% prestretch strain such that the failure stress was significantly lower for 300 seconds group than 90 seconds group. No significant differences in the failure strains were observed. When comparing BP and tibial nerve failure responses, significantly higher failure stress was reported in tibial nerve prestretched to 20% strain for 300 seconds than BP nerve. Conclusion These data suggest that neonatal peripheral nerves exhibit lower injury thresholds with increasing prestretch magnitude and duration while exhibiting regional differences. 

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