Mathematical Dynamic Modeling (MADYMO) of the Maternal Pelvis and Neonate for Simulating Shoulder Dystocia and Delivery Maneuvers
Authors:   , Iaconianni Joy Anita , Balasubramanian Sriram , Throckmorton Amy 
Published: July 2022

Shoulder dystocia (SD) is an obstetric emergency in which the neonate's shoulder is impacted behind the symphysis pubis of the maternal pelvis. This is a highly unpredictable event, occurring in about 1.5% of vaginal deliveries. Some complications of SD for the neonate include injury to the brachial plexus (BP), humerus or clavicle fractures, and hypoxia. Clinicians then perform a series of sequential maneuvers to minimize injury to the neonate and mother. These maneuvers include the McRoberts maneuver, application of suprapubic pressure (SPP), rotational maneuvers, and delivery of the posterior arm. The maneuvers increase in invasiveness and skill level in the order in which they are attempted. The most common injury associated with SD is BP injury due to overstretch resulting from the impaction of the shoulder itself, forces applied by the mother and clinician, and/or the maneuvers to manage SD. The BP is a network of nerves beginning below the C5-T1 vertebrae and provides innervation to the arms. Neonatal brachial plexus palsy (NBPP) can result in temporary or permanent injury with loss of function of the arms. BP stretch cannot be studied in clinical deliveries due to ethical limitations, and therefore 3-dimensional computational models are utilized. Only a few such computational models are reported in the literature creating a gap to investigate them further. In this study, computational models of the neonate and maternal pelvis were developed using MADYMO, and maneuvers that are used to manage SD were simulated and their effects on BP were investigated. The models were created based on a 90th percentile neonate and a 50th percentile adult female pelvis. The BP was modeled as a 7.5 cm nonlinear spring with properties obtained from an in vitro study of the failure response of neonatal piglet BP nerves. The neonate model was subjected to forces applied by the mother due to contractions only and contractions with voluntary pushing, as well as clinician-applied traction (CAT) force to compare the resulting BP stretch. Then, maternal forces along with clinician-applied suprapubic pressures (SPP), and oblique and posterior arm maneuvers were simulated to investigate the resulting BP stretch. The simulations resulted in a decrease in CAT force and BP stretch with more advanced maneuvers such as oblique maneuver and delivery of the posterior arm. CAT force and BP stretch also decreased as SPP increased. A decrease in CAT force was observed as maternal forces increased with only a slight increase in BP stretch in all maneuvers. The trends found using these MADYMO models are valuable for determining the risk of BP injuries associated with SD maneuvers which are unable to be quantified clinically. These trends could help guide clinicians by effectively correlating magnitudes of CAT forces during maneuvers with BP stretch that are associated with SD, and also provide the data needed to create clinical training tools in the future.