Proximity Of Uterosacral Ligament Suspension Sutures And S3 Sacral Nerve To Pelvic Landmarks

A common approach for surgical management of apical vaginal prolapse is use of the high uterosacral ligament suspension (USLS) procedure. Definitions of success for this procedure vary; its demonstrated efficacy for apical prolapse ranges from 59% to 98.3%. Reported adverse events associated with use of USLS procedures include suture erosion and vascular, nerve, and lower urinary tract injury. A serious complication, neuropathy, has been increasingly recognized. There is risk of sacral nerve entrapment with placement of USLS sutures. Limited data are available on methods of optimal suture placement to avoid nerve injury.Cadaver studies have been performed to optimize the safety of suture placement during USLS. A commonly used reference point for placement of the first USLS suture is the ischial spine. Few studies have examined the relative distances from the ischial spine to the sacral nerves. A previous cadaver study examined the distances from USLS sutures to specified points along the S1, S2, and S3 nerves and noted that all 3 S3 nerve points were closer to each USLS suture than either the S2 or S1 nerve points.The aim of this study was to describe the spatial relationships between the sacral nerve S3, the uterosacral ligament sutures, and discrete pelvic bony landmarks. The authors attempted to develop strategies for reducing the risk of nerve injury during USLS procedures. Unembalmed female human cadavers were used. After hysterectomy, 3 transvaginal USLS sutures were placed bilaterally in the uterosacral ligaments beginning at the level of the ischial spine. Three select bony pelvic landmarks (the ischial spine, pubic symphysis, and coccyx) were identified and marked with pins. Using the ischial spine as a landmark, distances were measured from each landmark to each suture and nerve point. The distance from each bony landmark to the S3 nerve points S3a, S3b, and S3c was extended radially to map out 3 arbitrary zones (zones A, B, C) where sutures may be placed and thus are sites of potential nerve injury. Zone A is closest to the sacral nerve root, and zone C is closest to the landmark. Descriptive statistics were used, and comparisons between measurements were made using Student t test and analysis of variance.Measurements were taken from 10 unembalmed dissected cadaver specimens. Distances for the ischial spine to points S3a, S3b, and S3c were 6.3, 5.4, and 4.6 cm, respectively. Approximately two thirds of the sutures were noted beyond zone C, indicating an increasing risk of nerve injury froma suture placed in zones farthest fromthe ischial spine (given their proximity to the sacral nerve).These measurements indicate that the ischial spine is the most clinically useful pelvic landmark of the 3 bony landmarks examined. Increased sacral nerve injury could result from sutures placed beyond the mean distance of 4.6 cm from the ischial spine. Using bony landmarks to avoid sacral nerve injury may be as important as suture depth and angle of suture placement.These spatial relationships can help surgeons recognize an additional risk for nerve entrapment and injury from each sequential USLS suture placed. Despite evidence that 3 sutures may provide more support to the vaginal apex, surgeons may consider placement of only 2 sutures to minimize the additional risk of nerve injury (when anatomical complexity may preclude safe placement of a third suture).