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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. Biomechanical Responses of Neonatal Brachial Plexus to Mechanical Stretch

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

   Singh, Anita; Shaji, Shania; Delivoria-Papadopoulos, Maria; Balasubramanian, Sriram (January 2018, Journal of Brachial Plexus and Peripheral Nerve Injury)

   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. 

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3. A Systematic Review of the Electrodiagnostic Assessment of Neonatal Brachial Plexus

   Orozco Virginia, Balasubramanian Sriram (May 2020, Neurology and Neurobiology)

   Despite improvements in obstetric care, neonatal brachial plexus palsy continues to significantly impact infants’ lives worldwide, with an incidence of 1 to 4 per 1000 live births. While a majority of affected infants recover spontaneously by three months, 20-30% suffer permanent functional deficits that significantly impair their quality of life. Anatomical complexity of the brachial plexus results in varying degrees of injury and pathological changes at multiple levels within the plexus. Current clinical diagnosis relies on electrodiagnostic techniques such as nerve conduction (i.e., motor and sensory) and electromyography studies. These techniques not only aid clinicians to differentiate between axonal and demyelinating lesions, evident by changes in signal shape and conduction, but also provide prognostic information in cases of brachial plexus injuries. The presented study offers a comprehensive review of existing literature on electrodiagnostic techniques employed for assessing neonatal brachial plexus injuries. 

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4. 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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5. Understanding Patterns of Neonatal Brachial Plexus Palsy Using a 3D Finite Element Model

   https://doi.org/10.5772/intechopen.1010022  

   J_Wright, Sarah; J_Grimm, Michele (May 2025, IntechOpen)

   Taiar, Redha (Ed.)

   Neonatal brachial plexus palsy is a birth process-related injury that affects 1–2/1000 infants, with about 10% of those having a permanent deficit that can affect the muscle strength, range of motion, and sensation of the upper extremity. While computational models make the most sense for investigation of injury mechanisms in the vulnerable infant population, the models remain very simplified – incorporating only a single indicator nerve that mimics the response of the C5 nerve root rather than taking into consideration the complex, 3D anatomy of the plexus. Two existing finite element models of the adult brachial plexus have been published – but neither attempts to model the complex anatomy of the plexus through the divisions, cords, and terminal nerves. This project involved the development of an anatomically appropriate 3D model of the infant brachial plexus. This is the first published finite element model of the full, complex anatomy of the brachial plexus and the first that includes an appropriate anatomy for an infant. The model was then used to better understand the pattern and progression of brachial plexus injury that has been observed clinically in neonates. The model was able to predict a stress distribution that aligns with the C5 nerve root being the location of initial injury. It also demonstrated how the stress in remaining, intact nerve roots will increase when rupture or avulsion of C5 and then C6 occurs – which matches the progression of the injury from the upper plexus (an Erb’s Palsy) to the middle and lower plexus. 

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