Three-Dimensional Modeling of the Pelvic Floor Support Systems of Subjects with and without Pelvic Organ Prolapse.

 Ren S, Xie B, Wang J, Rong Q.  BioMed Research International. 2015; Article ID 845985: 1-9.
http://dx.doi.org/10.1155/2015/845985
Pelvic PT Distance Journal Club December 9, 2015 MJ Strauhal

Purpose and Background:

·         Develop three-dimensional finite element models of the whole pelvic support systems of subjects with and without pelvic organ prolapse (POP) that can be used to simulate anterior and posterior wall prolapses

o    Prevalence of POP by symptoms report and “bother” is 3-6%; by clinical exam is 50% (different reference than Bo et al, but similar #’s)

o    Subtle injuries of the pelvic floor support system may lead to POP

o    Numerical simulations provide a tool to study pelvic function and the effect of support defects

o    Previous studies did not take into account the vaginal cavity which is of “great significance” when evaluating the mechanical behavior of POP

§  Previous studies oversimplified the structure of the ligaments and the vagina

Definitions:

·         Finite element analysis (FEA) is a computerized method for predicting how a product reacts to real-world forces, vibration, heat, fluid flow, and other physical effects.

·         Newton’s second law can be expressed as:

F = ma where F is the net force acting on the body, m mass of the body, and a the acceleration of the body in the direction of the net force

Materials and Methods:

• One healthy female age 55, para 2, BMI 20.9 w/o POP and one female age 56, para 1, BMI 27.8 w/ anterior vaginal wall POP (POPQ stage is not reported)
• Neither subject had previous pelvic surgery or “other contraindications to this procedure”
• Both underwent pelvic MRI and images were segmented into significant components by a trained GYN and senior radiologist for 3D reconstruction

Results:

• Axiel MRI and 3D models show:
• Healthy wm w/o POP
• LA is thicker, V-shaped
• Cardinal and uterosacral ligaments thicker
• Wm w/ POP
• LA is thinner, U-shaped, significant LA defect on the right
• Cardinal and uterosacral ligaments thinner
• Loss of attachment to the lateral pelvic wall
• The FEA showed that tissue damage and loss of anatomical integrity were the trigger for POP
• The support structures moved downward and backward when anterior POP occurred

Discussion:

• POP patient model revealed defects on the *right side and loss of LA muscle fibers
• LA muscle defects usually appears more often in the pubic vs iliococcygeal portion as shown in previous and in this study
• They did not separate the LA into subdivisions due to areas of overlap
• The cardinal and uterosacral ligaments have a common region of insertion at the cervix and upper vagina and were merged as one entity in this model
• 3D finite element models can be applied to study the mechanism of POP and provide help for clinical prevention and treatment.  This study improves upon the modeling of the entire pelvic floor support system and establishes more realistic contacts between various structures
• This study does not simulate paravaginal supports
• Does the description of perineal body and vaginal canal support agree with what you have previously read/studied?
• Would knowing the degree/stage of POP have made a difference in their model?
• How does this model demonstrate the complexity of pelvic floor structures and the variability of possible defects in anatomy postpartum?
• How does this study speak to the complexity of studying PFMT in wm with POP?