Rupture Warning of Scar Uterus in Vaginal Delivery by Finite Element Analysis / 医用生物力学

ABSTRACT

Objective To analyze the relationship between scar uterine stress and scar thickness/position by using finite element method, so as to study risk factors of scar uterus rupture. Methods Firstly, SolidWorks was used to establish a three-dimensional (3D) model of the uterus with variable scar thickness and position based on uterine size of the pregnant woman at 40th week of gestation, and then the intrauterine pressure was set in the ANSYS software with pressure range of 4.83-23.9 kPa to calculate the uterine stress. Results During the contraction process, the maximum stress was located in uterine scar, the maximum stress on the uterus with scar thickness smaller than 3 mm was greater than tensile strength of the uterus; 3 mm was used as thickness limit of the lower uterine body. If the thickness was smaller than 3 mm, cesarean section should be selected immediately. Otherwise, transvaginal delivery could be selected. When the scar thickness was 3.0 mm, the maximum stress experienced by the uterus decreased at first and then increased with the distance from the uterine floor increasing. The stress at the uterine scar was the smallest when the distance from the uterine floor was 295 mm; when the scar was 285-305 mm from the uterine floor, the ultimate stress on the scar was smaller than its tensile strength, and it was safer to choose a vaginal delivery. Conclusions Risk factors of scar uterine rupture were studied based on ANSYS finite element analysis. The analysis results were consistent with the clinical data, which provided analysis method and theoretical guidance for the choice of delivery method in clinic.