Department of Electrical and Computer Engineering, San Diego State University, San Diego, California, USA.
Department of Occupational Therapy, Huntington University, Fort Wayne, Indiana, USA.
Clin Anat. 2021 Sep;34(6):884-898. doi: 10.1002/ca.23739. Epub 2021 Jun 1.
The inherent variable anatomy of the neonate and the uniquely-shaped maternal birth canal that is associated with the evolution of human bipedalism constitute risk factors for neonatal brachial plexus palsy (NBPP). For example, those neonates with a prefixed brachial plexus (BP) are at greater risk of trauma due to lateral neck traction during delivery than those with a normal or postfixed BP. Compared to adults, neonates also have extremely large and heavy heads (high head: body ratio) set upon necks with muscles and ligaments that are weak and poorly developed. Accordingly, insufficient cranial stability can place large torques on the cervical spinal nerves. In addition, the pelvic changes necessary for habitual bipedal posture resulted in a uniquely-shaped, obstruction-filled, sinusoidal birth canal, requiring the human fetus to complete a complicated series of rotations to successfully traverse it. Furthermore, although there are many risk factors that are known to contribute to NBPP, the specific anatomy and physiology of the neonate, except for macrosomia, is not considered to be one of them. In fact, currently, the amount of lateral traction applied to the neck during delivery is the overwhelming legal factor that is used to evaluate whether a birth attendant is liable in cases of permanent NBPP. Here, we suggest that the specific anatomy and physiology of the neonate and mother, which are clearly not within the control of the birth attendant, should also be considered when assessing liability in cases of NBPP.
新生儿固有可变的解剖结构和与人类两足行走进化相关的独特形状的母体产道，构成了新生儿臂丛神经麻痹（NBPP）的危险因素。例如，那些前置臂丛（BP）的新生儿在分娩时由于颈部侧向牵引而受伤的风险比正常或后置 BP 的新生儿更大。与成人相比，新生儿的头部也非常大且沉重（高头身比），头部位于肌肉和韧带薄弱且发育不良的颈部上。因此，头部不稳定可能会对颈椎神经产生很大的扭矩。此外，为了适应习惯性双足姿势而发生的骨盆变化导致了独特形状的、充满阻塞的、正弦形的产道，需要人类胎儿完成一系列复杂的旋转才能成功通过。此外，尽管有许多已知的危险因素会导致 NBPP，但新生儿的特定解剖结构和生理学（除了巨大儿）并不被认为是其中之一。事实上，目前，分娩过程中对颈部施加的侧向牵引力是评估分娩助手在永久性 NBPP 病例中是否有责任的压倒性法律因素。在这里，我们建议在评估 NBPP 病例的责任时，也应考虑新生儿和母亲的特定解剖结构和生理学，这些因素显然不在分娩助手的控制范围内。
