Table 2. Model-estimated differences in physiological vaginal characteristics between groups.
Data presented as mean (standard error). All estimates are derived from linear models featuring surgery group, outcome, and their interaction. Significant p-values are indicated in bold.
CI, confidence interval; SE , standard error
a Recurrence is defined as prolapse beyond the hymen with strain.
b A more medial position is given by values closer to zero and a more lateral position is given by values further away from zero.
c A more anterior position is given by more positive or larger values and a more posterior position is given by more negative or smaller values.
d A more superior position is given by more positive or larger values and a more inferior position is given by a more negative or smaller values.
e A more horizontal (more acute) sagittal angle (towards the sacrum) is given by smaller values and a more vertical (straighter or obtuse) sagittal angle is given by larger values.
f A more medial coronal angle (aligned with the midline) is given by values closer to zero and a more lateral coronal angle (tilted to the left or right) is given by values further away from zero.
Figure 1. Illustration of the data processing steps of the vaginal analysis. (A ) Axial magnetic resonance (MRI) scan of the participant at recovery (rest period following strain without prolapse reduced). The vagina was manually segmented with the lumen excluded. Vaginal segmentations across multiple MRI slices were stacked to reconstruct a 3D surface model of the vagina with zero thickness. To remove aliasing (sharp edges) from the 3D vaginal model, a non-biased smoothing algorithm was applied such that the model’s original shape and volume was preserved. (B ) The 3D vaginal model was then placed in a morphometry algorithm to perform model-based vaginal measurements through anatomical landmark detection. First, the 3D model was iteratively sliced in the axial direction every 1.5 mm (half of the MRI slice thickness). For each 3D vaginal slice (represented as a thin ribbon), the right (red point) and left (blue point) lateral edges were extracted and the centroid (black point) of the vaginal slice was calculated. The straight-line distance between the lateral edges defined the transverse width of the vaginal slice. This iterative process was used to find the maximum transverse width and establish the right (red points) and left (blue points) lateral margins and centerline (black points) of the vagina. The vaginal centerline points were split in half to represent the upper (green points) and lower (purple) vagina. A line of best fit was calculated for each set to define the upper (green line) and lower (purple) vaginal axes. The pelvic coordinate system (PCS, dashed arrows) was then applied to calculate physiological vaginal position (black points) and morphology (angulation, dimension) measures in 3D space.
Figure 2. Visualization of the vaginal position and morphology (angulation, dimension) measures. (A ) Vaginal position measures. Position (black points) of the vaginal apex and mid-vagina in the coronal and sagittal plane with respect to the 3D pelvic coordinate system (PCS). The X-, Y-, and Z-coordinates of each point correspond to the medial-lateral, anterior-posterior, and superior-inferior position, respectively. The orientation of the axes PCS indicates the positive direction. (B ) Vaginal angle measures. Angles of the upper (green angle) and lower (purple angle) vagina in the coronal and sagittal plane. The coronal angles are with respect to the Z- (superior-inferior) axis and the sagittal angles are with regard to the Y- (anterior-posterior) axis. The upper-lower vaginal coronal angle is the difference between the upper and lower vaginal coronal angles. The upper-lower vaginal sagittal angle is the sum of the upper and lower vaginal sagittal angles. (C ) Vaginal dimension measures. The vaginal length (black dotted double arrow) is given by the length of the vaginal centerline. The maximum transverse width (solid black double arrow) is given by the largest straight-line distance between the right (red point) and left (blue point) lateral margin of the vagina across all vaginal slices along the total vaginal length. The vaginal surface area and volume are given by the surface area and the amount of space enclosed by the surface of the 3D vaginal model, respectively.