3D Analysis of the Impact of Pelvic Organ Prolapse Repair

Background

Pelvic Organ Prolapse (POP) is a condition found in women in which internal organ(s) start protruding out of the body cavity. In the United States alone, almost 3% of women have some form of prolapse. Age, genetic predispositions, and traumatic injuries are possible causalities of POP. While there are different types of surgeries that help repair pelvic anatomy, POP often recurs.

The mechanism behind recurring Pelvic Organ Prolapse following prolapse surgery is still not very well understood. Understanding the anatomical features involved in POP may lead to a better understanding of its mechanisms and so also help improve the possible surgical outcomes.

Hypothesis/Objectives

The main objective is to compare the vaginal anatomy amongst three groups. The three groups are the following: women who underwent Native Tissue Repair(NTR N=34) for prolapse, women who underwent Vaginal Mesh Repair(VM N=28) for prolapse, and nulliparous women who never had prolapse with “normal” anatomy(N=5), who were used as a control. The postoperative MRIs were taken 30-42 months. A subset of the group includes surgical success (prolapse did not recur) and failure (surgical failures (prolapse did recur).

The measurables for this project include the following: the coordinate positions, as shown in the image below, the lower sagittal vaginal angle, the upper sagittal vaginal angle, and the upper-lower sagittal vaginal angle.

It is hypothesized that a more posteriorly-inferiorly deviated vagina (smaller upper/lower vaginal angle and y-/z-position, larger upper-lower vaginal angle) is associated with NTR(vs VM), failure(vs success), and postoperative anatomy(vs normal). The diagram below shows the angle layout mentioned earlier.

Methodology/Analysis

The 3D models were produced using the program 3D Slicer. The MRI file viewed in the axial view had snapshots the pelvic area at 3 mm intervals. At each interval depth, the vaginal cavity was highlighted. Highlighting the cavity at every depth the vagina was visible in resulted in the 3D model shown below on the right. These models were smoothed and refined before being analyzed.

After all the models were produced, a code was created, through Mathematica, to process the models and give the vagina’s axis positions, based on the 3D coordinate system seen earlier, as well as the vaginal angles, as described in the picture in the next slide.

Methodology/Analysis (cont.)

To analyze the results of this experiment, a Wilcoxon Rank-Sum Test was used with a p value of 0.05.18/34 NTR and 10/28 VM operations were failures. No significant differences were observed when comparing surgical groups or outcomes.

When comparing postoperative patients to normal patients, the postoperative patients had a statistically significant posteriorly positioned vagina (y = 40 mm vs 49 mm), inferiorly positioned vagina (z = -14 mm vs -2 mm), smaller sagittal upper and lower angle (44° vs 60°) and (52° vs 83°) and larger sagittal upper-lower vaginal angle(172° vs 159°).

Conclusion/Future Directions

Pelvic Organ Prolapse repair surgery fails to restore the pelvic anatomy back to normal. The postoperative group, more than half of which were considered successes, had vaginal angles and coordinate positions statistically significantly different than the normal anatomical values. There was not a statistically significant difference in vaginal angles and positioning amongst surgery type or outcome. This means that NTR and VM both restored the vaginas to similar positions and that the successes and failures were not that different from each other.

To ensure better surgical outcomes for POP in the future, the restored anatomy must be closer to the normal positioning.

The future work of this project is to run a statistical shape analysis of the 3D vaginal models to identify shape-specific differences while ignoring size/dimension and position/orientation.