Biomechanics of pathological pelvic floor: Finite element comparative analysis of the prolapsed pelvic floor

To establish a 2D biomechanical finite element model of a pathological pelvic floor and explore mechanisms driving pelvic organ prolapse (POP) progression from mild to severe stages based on a Stage I POP-Q patient.

We developed a two-dimensional biomechanical finite element model based on the clinical presentation of a patient with POP-Q stage I prolapse at rest. The biomechanical interactions between the morphological characteristics and mechanical support were investigated by considering the effects of genital hiatus, intra-abdominal pressure, and combined injuries.

A more severe prolapse occurred on the pelvic floor during a resting genital hiatus, with an abdominal pressure of 83. 9 cmH₂O and a posterior vaginal wall injury rate of 75%. However, when the genital hiatus changed from a resting state to a prolapsed state, the uterus and the anterior vaginal wall prolapsed from the orificium vaginae. Compared to the case of a resting genital hiatus, a prolapsed genital hiatus results in a 101. 6% and 56. 9% increase in the maximum downward displacement of the cervix and mid-portion of the anterior vaginal wall, respectively.

Under the influence of combined injuries, abdominal pressure and the prolapsed genital hiatus, the pathologic pelvic floor may progressively evolve from mild prolapse to moderate or severe prolapse of the anterior vaginal wall and bladder, as well as the uterus. The overall morphological characteristics are dominated by downward prolapse displacement. The combined force directs downward toward the orificium vaginae and the main mechanical support gradually shifts to the perineal body.