Developing a Biomechanical Model to Study OASIS

Childbirth-related injuries, such as perineal lacerations and Obstetric Anal Sphincter Injuries (OASIS), can lead to maternal complications. Finite element (FE) models have been used to study childbirth biomechanics, but these models often lack a comprehensive representation of the perineal region. This study aimed to develop a FE model of the pelvic floor muscles (PFM), perineal structures, and anal sphincter. The model included the PFM, superficial and deep perineal structures, and the anal sphincter region. A combination of MRI images and anatomical information was used to develop the model. Different constitutive models were employed to represent the mechanical properties of the muscles and sphincters. Simulations were performed to mimic a vaginal delivery, and the stretch and maximum principal stresses were analysed in various regions of interest. The results showed significant stretching of the perineal body, particularly in the lower portion near the urogenital hiatus. The maximum stresses were observed in the region connected to the perineal body in the anal sphincter, indicating its vulnerability to perineal tears and OASIS. The study highlighted the importance of incorporating the perineal region into computational models and understanding the biomechanics of the anal sphincter to prevent complications during childbirth. However, simplifications and limitations in the model were acknowledged.