8: Inferior gluteal neurovascular anatomy in female cadavers: Clinical applications to pelvic reconstructive surgeries

Abstract

Gluteal pain is common following sacrospinous ligament fixation (SSLF) procedures. Reported rates range from 12.4-55.4% in the postoperative period and from 4.3-15.3% at 4-6 weeks postoperatively. The neuroanatomy associated with the sacrospinous ligament (SSL) has not been thoroughly examined from a gluteal perspective relative to SSLF. The inferior gluteal nerve has not been carefully evaluated and data on thickness and height of SSL at its midportion is scarce. This information should provide insights into safe suture placement and on the source of gluteal pain following SSLF. The objectives of this study were to characterize the IGN and other neurovascular anatomy associated with the SSL, to determine thickness and height of SSL at its midpoint, and to correlate findings to prolapse repair procedures that use the SSL as a fixation site. Detailed dissections were performed in unembalmed female cadavers. From a gluteal approach, distances from nerves and vessels to ischial spine (IS) and to midpoint of SSL were recorded. Origin and width of the IGN were documented. Closest neurovascular structure to IS and to midpoint of SSL was noted. Length and height of SSL and thickness of coccygeus-sacrospinous ligament (C-SSL) complex were documented. Distance from IS to fusion point of SSL and sacrotuberous ligament (STL) was recorded. From a pelvic approach, sacral nerves perforating the ventral surface of coccygeus muscles were documented. Closest structure to superior border of midpoint of SSL was examined. Branches from sacral plexus that coursed between the SSL and STL were noted and their origin and termination determined. Descriptive statistics were used for data analysis. Ten cadavers were examined. From a gluteal perspective, the closest structure to dorsal surface of IS was the pudendal nerve, median distance 2mm (range 0–8mm). Median distance from IGN to IS and to midpoint of SSL was 31.5mm (21-53mm) and 30.5mm (10-47mm), respectively. The IGN arose from dorsal surface of L5-S1 nerves in 100% of specimens; a contribution from S2 was noted in 47% of hemipelvises. Median thickness of C-SSL complex at its midpoint was 4 mm (2-7mm) and median height of SSL was 14mm (3-20mm). Fusion of SSL and STL was noted a median distance of 19mm (10-36mm) from IS. From a pelvic perspective, the closest structure to superior border of SSL at its midpoint was the S3 nerve, median distance 3mm (0–11mm). In 70% of specimens, 1-3 branches from S3 and/or S4 nerves perforated or coursed ventral to the STL, before perforating the gluteus maximus or the cutaneous tissue just superficial to the muscle. Branches from S3 and/or S4 perforated the ventral surface of coccygeus muscles in all specimens. It is improbable that the inferior gluteal nerve is implicated in postoperative gluteal pain following SSLF procedures. More likely, direct branches from S3 and/or S4, coursing between the SSL and STL may be injured with deep penetration of the SSL. Nerve branches to the coccygeus muscles are likely to be disrupted, even when sutures are placed in the recommended location. Suture placement should be kept on the lower portion of the SSL to avoid nerve injury.