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.