Stress distribution and deformation of uterosacral ligament and cardinal ligament under different working conditions simulated by the finite element model / 中华妇产科杂志

ABSTRACT

Objective To establish the finite element model of uterosacral ligament (USL) and cardinal ligament (CL) and analyze the stress distribution and deformation with USL and CL under different working conditions. Methods Patients with stage Ⅲ-Ⅳpelvic organ prolapse (POP) and healthy female volunteers were selected for research subject, and divided into anterior uterus group and posterior uterus group. Two POP patients and two volunteers were selectd into the anterior uterus group and posterior uterine group respectively. Pelvic MRI scan was performed in two groups. Based on the original MRI data sets, the finite element model of USL and CL was constructed by using the software such as the Mimics, and the stress distribution and deformation of USL and CL were simulated. Results Under the premise of the elastic modulus fixed and three different working conditions such as 60 cmH2O, 99 cmH2O and 168 cmH2O (1 cmH2O=0.098 kPa) with abdominal pressure generated by maximum Valsalva maneuver, according to the present conditions and the simulation, the trend was analyzed the stress and deformation of the uterus, anterior vaginal wall, USL and CL in two groups were mainly distributed in the middle and lower part of the anterior vaginal wall or the ligament and the cervix-vagina junction, the maximum stress and the maximum displacement were mainly concentrated in the lower region of the anterior vaginal wall. With increasing of abdominal pressure generated by the maximum Valsalva maneuver, the maximum stress values of the POP patient in anterior uterus group under three different working conditions were 0.027 9, 0.046 0, 0.078 0 MPa, and the maximum displacement values were 9.145 5, 15.090 0, 25.607 0 mm. The maximum stress values of the volunteer in anterior uterus group under three different working conditions were0.012 6, 0.020 8, 0.035 3 MPa, and the maximum displacement values were 1.816 7, 2.997 5, 5.086 7 mm. The maximum stress values of the POP patient in posterior uterine group under three different conditions were 0.069 4, 0.114 6, 0.194 5 MPa, and the maximum displacement values were11.658 0, 19.236 0, 32.643 0 mm. The maximum stress values of the volunteer in posterior uterus group under three different working conditions were0.009 1, 0.015 1, 0.025 6 MPa, and the maximum displacement values were2.581 6, 4.259 6, 7.228 4 mm. The maximum stress values and the maximum displacement values were all increased with increasing of abdominal pressure in the two groups. The maximum stress values and the maximum displacement values of the POP patients were greater than those of volunteers. Under different working conditions, the maximum stress values and maximum displacement values of the posterior uterus POP patient were all greater than those of the anterior uterus POP patient. Conclusions The finite element model of USL and CL is completely based on the MRI technology and the model is real and reliable. The increase of abdominal pressure will produce a larger stress and deformation of USL and CL, which is one of the reasons causing the injury of the ligament.