Objective
To determine the variation in vaginal axis and posterior cul-de-sac depth when the lowest suture used to attach the sacrocolpopexy mesh to the anterior longitudinal ligament is anchored at different levels.
Study Design
At five lumbosacral mesh attachment sites, the anterior vaginal wall axis angle was measured relative to a line between the lowest border of the pubic symphysis and fourth sacral (S4) foramen in 9 unembalmed cadavers. The vertical distance from S4 to the posterior mesh was measured as a surrogate of cul-de-sac depth.
Results
From a mesh fixation point at the lower border of S2 to a point at the lower border of L5, there was a 3-fold increase in both vaginal axis angle (13.04 ± 3.19 vs 42.88 ± 4.16 cm) and distance from S4 to the posterior mesh (2.50 ± 0.61 vs 7.38 ± 1.30 cm) between these points.
Conclusion
During sacrocolpopexy, progressively cephalad sacral attachment increases vaginal axis angle and cul-de-sac depth.
Sacrocolpopexy is an effective surgical procedure for vaginal apical prolapse. In the initial description of the technique in 1957, the uterus, cervix, or vagina was sutured directly to the anterior longitudinal ligament at the L5-S1 level using permanent suture. Graft material was subsequently introduced to reduce excessive tension, and the procedure has continued to evolve with numerous modifications aimed at improving outcomes, reducing complications, or restoring normal anatomy.
On the basis of radiographic studies suggesting that the normal vaginal axis was aimed toward the sacral hollow, the procedure was modified to restore the vaginal axis to the more anatomic S3-S4 level. In response to brisk and life-threatening hemorrhage at this location, fixation closer to the promontory has been advocated to permit easier visualization of the middle sacral vessels.
Contemporary descriptions of the procedure recommend graft attachment site at the sacral promontory (SP). The presacral space is highly vascular and variable, and surgeons may anchor the graft at different sacral levels to avoid vessels or nerves. In addition, the angle from L5 to S1 can range from 40–90 degrees. With the advent of laparoscopic and robotic technologies, this angle may be technically difficult to negotiate for dissection and suturing, favoring a higher attachment site with further anterior deviation of the vaginal axis. However, the effects of different sacral fixation points on the vaginal axis angle is unknown, and we hypothesized that fixation at the SP may result in significant anterior deviation of the vaginal axis with potential implications for recurrent prolapse, urinary incontinence, and bowel obstruction. Thus, the objectives of this study were to determine the variation in vaginal axis angle and posterior cul-de-sac depth when sacrocolpopexy mesh is anchored at different levels of the sacrum and lowest lumbar vertebra.
Materials and Methods
This study was exempt from institutional review board approval, at the University of Texas Southwestern Medical Center, in accordance with the Code of Federal Regulations, Title 45, Part 46. A total of 9 unembalmed female cadavers were obtained from the Willed Body Program at the University of Texas Southwestern Medical Center in Dallas. Age, race, and cause of death were collected.
The pelvis was transected in a sagittal plane at mid sacrum. A paramedian incision was made through the bladder, vagina, and rectum to preserve the majority of the vaginal tube. The bladder was dissected off the anterior vaginal wall to the upper border of the trigone, and the excess bladder wall excised above the trigone. The rectovaginal space was developed to the upper margin of the perineal body.
To standardize the procedure, separate polypropylene mesh strips 2 cm in width, were each attached to the vagina with 6-8 interrupted stitches of 2-0 ethibond (Ethicon, Somerville, NJ). The anterior vaginal wall mesh was secured from a level 1 cm above the upper border of the bladder trigone to 1 cm from the apical closure site. The posterior mesh was attached from a level 1 cm above the upper margin of the perineal body to 1 cm from the apical closure site. Colored metal pins were placed in the lumbar and sacral vertebrae at 5 levels for mesh fixation and angle measurement: (1) lower border of L5; (2) mid portion of L5–S1 disk; (3) SP; (4) lower border of S1; and (5) lower border of S2. A sixth pin was placed at the level of the fourth sacral foramen (S4) for reference.
A vaginal manipulator was placed in the upper part of the vagina and the apex was directed to the lowest point of intended sacral fixation. Care was taken to avoid overstretching the vagina by displacement of the vaginal apex beyond the vaginal length. For each cadaver, both mesh strips were then anchored to the sacrum at the level of each metal pin with care to avoid stretching or undue tension of the intervening portion of mesh ( Figure 1 ).
A reference line was selected extending from the lower border of the pubic symphysis (PS) to the S4 foramina (PS-S4 line) to approximate the pubococcygeal line previously described in imaging studies using MRI to measure the vaginal axis after colpopexy. During our preparatory dissections, we observed that the S4 foramen, which is found on the lowest border of the S4 vertebra, was more accurately and consistently identified in cadavers than the tip of the coccyx; therefore, we chose the S4 foramen instead of the coccyx in an attempt to increase reproducibility of our measurements. The vaginal axis angle was then measured from the PS-S4 line to each to each vertebral point and recorded using a 15 cm orthopedic goniometer (Quint Measuring Systems, Inc., San Ramon, CA) ( Figure 2 ). In addition, the length of the intervening segment of mesh from the apex to each anchor point was measured. A leveling device (Hopkins Manufacturing Company, Emporia, KS) was attached to the goniometer such that the goniometer straight edge was zero degrees to the horizontal when the leveling bubble was centrally located, and the vertical distance from S4 to the posterior mesh was measured as a surrogate marker of posterior cul-de-sac depth ( Figure 3 ). All measurements were taken 3 times for each cadaver and the average used in data analysis. Between different lumbosacral levels, the mesh was removed and reattached to the new point using the same vaginal elevation technique and measurements were repeated.
Additional measurements included the urethral length, from external to internal urethral meatus, and the total vaginal length (TVL). Angles were recorded in degrees and all other measurements were recorded in centimeters (cm). All measurements are reported as mean ± standard deviation (SD).
Results
Limited demographic information was available for the study cadavers. All cadavers were white, and average age at the time of death was 79.3 ± 12.3 (range, 63–96 years). The most common causes of death were cardiopulmonary disease and nongynecologic cancer; none of the cadavers had conditions affecting the vaginal walls, apex, or lower urinary tract. Two cadavers had the uterus and cervix removed before study initiation, and a supracervical hysterectomy was performed in the remainder.
The average TVL and urethral length were 9.4 ± 1.0 and 3.7 ± 0.8 cm, respectively. The vaginal axis angles and posterior cul-de-sac depth for the various lumbosacral levels are presented in the Table . From the sacral fixation point at the lower border of S2 to the point at the lower border of L5, there was a 3-fold increase in the vaginal axis angle ( Figure 4 ). If only the lower border of S1 to the middle of the L5-S1 disk are considered, the angle doubled. Similarly the vertical distance from S4 to the posterior mesh increased 3-fold from a sacral anchor point at lower S2 to lower L5 vertebrae ( Figure 4 ).
| Mesh fixation level | Vaginal axis angle (degrees) | Posterior cul-de-sac depth, cm |
|---|---|---|
| L5 | 42.9 ± 4.2 | 7.4 ± 1.3 |
| L5-S1 disc | 40.0 ± 4.6 | 6.7 ± 1.5 |
| Promontory | 35.8 ± 4.2 | 6.2 ± 1.5 |
| S1 | 23.0 ± 5.1 | 4.3 ± 1.2 |
| S2 | 13.0 ± 3.2 | 2.5 ± 0.6 |
Results
Limited demographic information was available for the study cadavers. All cadavers were white, and average age at the time of death was 79.3 ± 12.3 (range, 63–96 years). The most common causes of death were cardiopulmonary disease and nongynecologic cancer; none of the cadavers had conditions affecting the vaginal walls, apex, or lower urinary tract. Two cadavers had the uterus and cervix removed before study initiation, and a supracervical hysterectomy was performed in the remainder.
The average TVL and urethral length were 9.4 ± 1.0 and 3.7 ± 0.8 cm, respectively. The vaginal axis angles and posterior cul-de-sac depth for the various lumbosacral levels are presented in the Table . From the sacral fixation point at the lower border of S2 to the point at the lower border of L5, there was a 3-fold increase in the vaginal axis angle ( Figure 4 ). If only the lower border of S1 to the middle of the L5-S1 disk are considered, the angle doubled. Similarly the vertical distance from S4 to the posterior mesh increased 3-fold from a sacral anchor point at lower S2 to lower L5 vertebrae ( Figure 4 ).
