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Reported rates of gluteal pain after sacrospinous ligament fixation range from 12–55% in the immediate postoperative period and from 4–15% 4–6 weeks postoperatively. The source of gluteal pain often is attributed to injury to the nerve to levator ani or pudendal nerve. The inferior gluteal nerve and other sacral nerve branches have not been examined thoroughly as potential sources of gluteal pain.
The purpose of this study was to further characterize anatomy of the inferior gluteal nerve and other nerves that are associated with the sacrospinous ligament from a combined gluteal and pelvic approach and to correlate findings to sacrospinous ligament fixation.
Dissections were performed in female cadavers that had not been embalmed with gluteal and pelvic approaches. From a pelvic perspective, the closest structure to the superior border of the sacrospinous ligament midpoint was noted, and the sacral nerves that perforated the ventral surface of coccygeus muscle were examined. From a gluteal perspective, the closest distances from ischial spine to the pudendal, inferior gluteal, posterior femoral cutaneous, and sciatic nerves were measured. In addition, the closest distance from the midpoint of sacrospinous ligament to the inferior gluteal nerve and the origin of this nerve were documented. The thickness and height of the sacrospinous ligament at its midpoint were measured. Sacral nerve branches that coursed between the sacrospinous and sacrotuberous ligaments were assessed from both a pelvic and a gluteal approach. Descriptive statistics were used for data analysis.
Fourteen cadavers were examined. From a pelvic perspective, the closest structure to the superior border of sacrospinous ligament at its midpoint was the S3 nerve (median distance, 3 mm; range, 0–11 mm). Branches from S3 and/or S4 perforated the ventral surface of coccygeus muscles in 94% specimens. From a gluteal perspective, the closest structure to ischial spine was the pudendal nerve (median distance, 0 mm; range, 0–9 mm). Median closest distance from inferior gluteal nerve to ischial spine and to the midpoint of sacrospinous ligament was 28.5 mm (range, 6–53 mm) and 31.5 mm (range, 10–47 mm), respectively. The inferior gluteal nerve arose from dorsal surface of combined lumbosacral trunk and S1 nerves in all specimens; a contribution from S2 was noted in 46% of hemipelvises. At its midpoint, the sacrospinous ligament median thickness was 5 mm (range, 2–7 mm), and its median height was 14 mm (range, 3–22 mm). In 85% of specimens, 1 to 3 branches from S3 and/or S4 nerves pierced or coursed ventral to the sacrotuberous ligament and perforated the inferior portion of the gluteus maximus muscle.
Damage to the inferior gluteal nerve during sacrospinous ligament fixation is an unlikely source for postoperative gluteal pain. Rather, branches from S3 and/or S4 that innervate the coccygeus muscles and those coursing between the sacrospinous and sacrotuberous ligaments to supply gluteus maximus muscles are more likely to be implicated. A thorough understanding of the complex anatomy surrounding the sacrospinous ligament, limiting depth of needle penetration into the ligament, and avoiding extension of needle exit or entry point above the upper extent of sacrospinous ligament may reduce nerve entrapment and postoperative gluteal pain.
Reported rates of serious adverse events that are associated with SSLF are low and similar to comparable vaginal prolapse repair procedures, such as the uterosacral ligament suspension. In a recent randomized trial that compared outcomes of SSLF and uterosacral ligament suspension, the rates of gluteal or posterior thigh pain that persisted 4–6 weeks postoperatively were higher in the SSLF group (4%) compared with the uterosacral ligament suspension group (0.5%).
As previously described, “the SSL consists of dense connective tissue that attaches to the ischial spine laterally and to the lower part of the sacrum and coccyx medially. The SSL, along with the sacrotuberous ligament (STL), divides the sciatic notches of the ischium and ilium into the lesser and greater sciatic foramen (GSF), respectively. The internal pudendal and inferior gluteal vessels, pudendal and sciatic nerves, and other branches of the sacral nerve plexus pass through the GSF in close proximity to the ischial spine and SSL. The coccygeus muscle lies on the ventral or pelvic surface of the SSL and together with the levator ani muscles comprises the pelvic diaphragm. The coccygeus muscle has the same bony attachments and runs an identical course to the SSL.”
Because of this relationship, needle entry into the SSL requires passage through the coccygeus muscle and overlying layer of fascia.
Suture placement into the SSL can be achieved with various ligature carriers, such as the Deschamps, Capio, Miya hook or a Mayo needle and straight needle driver. Various rates of gluteal or thigh pain have been reported with the use of different devices. For example, 55.4% gluteal or thigh pain was noted in the immediate postoperative period in a retrospective study of women who underwent SSLF in which the Capio device was used.
In this study, pain persisted in 15.4% of patients at 6 weeks follow up. Another retrospective review compared 3 different techniques for suture placement (Deschamps, Miya hook, and standard needle driver) showed an 18% rate of nerve injury with the use of Deschamps; no nerve injuries were reported with the use of the Miya hook or the standard needle driver.
These striking differences in the rates of gluteal or thigh pain with the use of different devices may be explained by depth of needle penetration into the SSL, number of ligament punctures, extent of ligament spanned, and surgeon experience with a specific device.
The neuroanatomy that is associated with the SSL has been described mainly from a transabdominal or pelvic approach.
These studies have emphasized the relationship of the pudendal nerve and vessels and that of the nerve to levator ani to the C-SSL complex. The inferior gluteal nerve (IGN) exits the pelvis between the piriformis muscle and C-SSL complex and supplies the gluteus maximus muscle and overlying skin. Thus, injury to this nerve may lead to gluteal pain after SSLF. However, the course and anatomic relationships of the IGN has not been examined thoroughly. The objectives of this study were to further characterize the anatomy of the IGN and other nerves that are associated with the SSL from a combined gluteal and pelvic approach and to correlate findings to SSLF.
Materials and Methods
Detailed dissections were performed in female cadavers that had not been embalmed that were obtained from the Willed Body Program at the University of Texas Southwestern Medical Center in Dallas, TX. This study was considered exempt from review by the University of Texas Southwestern Medical Center Institutional Review Board in accordance with the Code of Federal Regulations, Title 45. Age, race, height, weight, and cause of death were available for all donated bodies.
Cadavers were transected above the level of aortic bifurcation, at mid thigh, and in the midsagittal plane to facilitate exposure. Dissections were first performed from a pelvic approach before midsagittal transection (Figure 1). The peritoneum overlying the iliac vessels and the fascia that covers the piriformis muscles was resected to expose the lumbosacral trunk (L4, L5), first through fourth sacral nerves (S1–S4), and the inferior gluteal and internal pudendal arteries. These vessels were tagged with sutures for later identification during gluteal dissections. The visceral branches of the internal iliac artery and internal iliac veins were removed to expose the ventral surface of the coccygeus muscle and its superior fascial layer. Sacral nerve branches that perforated the coccygeus muscle were dissected carefully, and their origin was documented. The tip of the ischial spine was identified and marked with a metal pin. Dissections were then continued through a gluteal approach. The skin and subcutaneous tissue overlying the gluteus maximus muscles and posterior thigh were removed sharply starting at the midline of the sacrum. The gluteus maximus was then cut from its attachments at the sacrum and iliac crest and carefully reflected laterally to preserve the inferior gluteal neurovascular bundle. Once identified, the inferior gluteal artery and nerve were tagged with sutures. The dorsal surface of STL was exposed between the lateral sacrum and ischial tuberosity, and neurovascular structures that were noted in proximity to the ligament were dissected carefully. The STL was then transected in its midpoint, perpendicular to its long axis, and the pudendal neurovascular bundle was identified on the dorsal surface of the SSL. The length of the SSL was measured from the tip of the ischial spine to the ligament attachment on the lateral and lower aspect of the sacrum, and a metal pin was placed at the ligament’s midpoint. The transected edges of the STL were reflected, and the point at which the sacrotuberous and SSLs fused was identified. The distance from the ischial spine to this fusion point was measured. Other structures that exited the pelvis through the GSF were then identified. These included the piriformis muscle and the sciatic and posterior femoral cutaneous nerves.
From a gluteal perspective, the closest distances from the tip of the ischial spine to the pudendal, inferior gluteal, posterior femoral cutaneous, and sciatic nerves were measured. In addition, the closest distance from the midpoint of SSL to the IGN and the origin of this nerve were documented. The width of these nerves and that of the piriformis muscles in the midgluteal region were also documented. Last, the ventral to dorsal (thickness) and superior to inferior (height) extents of the C-SSL complex at its midpoint were measured. From a pelvic perspective, the closest structure to the superior border of the SSL midpoint and the origin of sacral nerves that perforated the ventral surface of the coccygeus muscle were documented. Sacral nerve branches that coursed between the sacrospinous and STLs were examined from both the gluteal and pelvic approaches, and their origin and termination was documented.
All measurements were taken twice by the same examiner who used the same caliper and 10-cm plastic ruler. Photographs of all dissections were taken, and descriptive statistics were used for data analysis and reporting.
Fourteen female cadavers that had not been embalmed were examined. All cadavers were white, with median age of 74.5 years (range, 59–94 years). The median body mass index was 20 kg/m2 (range, 13–30 kg/m2). The most common cause of death was lung disease. Dissections and available medical histories revealed no evidence of previous pelvic surgery or pelvic disease such as cancer, fractured pelvic bones, or trauma.
In 50% of specimens, the closest structure to the superior border of SSL at its midpoint was the S3 nerve, with a median distance of 3 mm (range, 0–11 mm; Figure 2). In the remaining specimens, the pudendal nerve (35%) or S4 (15%) were the closest structures. Branches from S3 and/or S4 were noted to perforate the ventral surface of the coccygeus muscles in 94% of specimens. An S5 nerve, 1–2 mm wide, was identified coursing beneath the coccygeus fascia in 43% of hemipelvises. When identified, it joined the S4 nerve close to the fourth sacral foramen and contributed to coccygeus muscle innervation.
The closest distances from the ischial spine to the pudendal, inferior gluteal, posterior femoral cutaneous, and sciatic nerves and the widths of these nerves in the midgluteal region are presented in the Table. In 82% of cadavers, the closest structure to the tip of the ischial spine was the pudendal nerve (median distance, 0 mm; range 0–8 mm). In all specimens, this nerve coursed medial to the ischial spine (Figure 3). In remaining 18% of specimens, the internal pudendal artery was the closest structure to the ischial spine (median distance, 4 mm; range, 0–8 mm). The median distance from the midpoint of SSL to IGN was 31.5 mm (range, 10–47 mm). The closest median distance from the inferior gluteal artery to ischial spine was 19 mm (range, 4–33 mm). The IGN arose from the dorsal surface of the combined lumbosacral trunk and S1 nerves in all specimens; a contribution from S2 was noted in 46% of hemipelvises.
TableClosest distances from ischial spine to nerves and widths of these structures in mid gluteal region
Ischial spine: median distance, mm (range)
Width, mm (range)
Posterior femoral cutaneous
Florian-Rodriguez et al. Nerves associated with sacrospinous ligament. Am J Obstet Gynecol 2016.
The median length of the SSL was 50 mm (range, 24–59 mm). Excluding the 24-mm length, a value obtained in a 94-year-old female cadaver with a body mass index of 13 kg/m2, the length of the SSL ranged from 38–59 mm. At its midpoint, the median thickness and height of C-SSL complex were 5 mm (range, 2–7 mm) and 14 mm (range, 3–22 mm), respectively. Fusion of SSL and STL was noted a median distance of 15.5 mm (range, 6–36 mm) from the ischial spine.
In 85% of specimens, between 1 and 3 branches from S3 and/or S4 nerves pierced or coursed between the sacrospinous and the STLs (Figures 4 and 5). These nerves perforated the lower and medial border of the gluteus maximus muscle or the subcutaneous tissue medial to the ischial tuberosity.
Nerve branches from S3 and/or S4 that coursed between the STL and SSL and perforated the gluteus maximus muscles were found in the majority of cadavers. Importantly, these branches did not join the pudendal nerve, which is also formed by contributions from S3 and S4 nerves. Although small nerve branches that pass between the STL and SSL have been described, detailed depictions of their origin, termination, and course relative to the midpoint of SSL and ischial spine are limited.
In these cases, the inferior rectal nerve did course on the dorsal surface of the SSL and supplied branches to the external anal sphincter and perianal skin. Our current findings, which included the nerves’ independent origin from S3 and/or S4 and their frequent course through the STL and gluteus maximus muscle, suggest that these nerves are independent from the inferior rectal and pudendal nerve. The anatomic course and termination of the nerves that were found in our study closely resemble that of the perforating cutaneous nerve, which is a nerve that arises from the S2 and S3 dorsal nerve roots of the sacral plexus.
The perforating cutaneous nerve exits the pelvis by piercing the STL eventually to supply the skin over the inferomedial aspect of the gluteus maximus. However, the branches that we noted arose from S3 and/or S4 and often perforated the substance of the gluteus maximus muscles. Our findings may represent anatomic variants to the perforating cutaneous nerves. In this anatomic study, the IGN was found approximately 3 cm superior to the midpoint of the SSL and ischial spine. Thus, direct injury to this nerve is an unlikely source of postoperative gluteal pain after SSLF. Injury to the IGN would lead to motor deficits, which include impaired hip extension and gluteal muscle wasting, which are not common sequela of SSLF. Our findings differ from those reported by Sagsoz et al,
where the IGN was found to be an average distance of 1.4 cm from the ischial spine in 9 embalmed female pelvic halves. The relatively long distance from the IGN to the SSL and ischial spine could be explained by the origin of this nerve from the upper part of the sacral plexus, specifically L5 and S1.
Nerve branches from S3–S5 to the coccygeus muscle where noted in 94% of specimens. This finding suggests that injury to these nerves is possible, even when sutures are placed in the recommended mid segment of the ligament, approximately 2–3 cm medial to the ischial spine.
Our findings are similar to those of Roshanravan et al
Needle entry or exit point over the superior extent of the C-SSL complex is more likely to disrupt S3 or the pudendal nerve and to lead to both sensory and motor deficits in the regions that are innervated by these nerves.
Clinical presentations of S3 nerve entrapment may range from sensory deficits in the perineal area to potentially sciatic type pain or involvement. If the sensory component that contributes to the pudendal nerve was affected, paresthesias, numbness, or pain in the perineum may be experienced. If the motor component of S3 was affected, urinary and/or fecal incontinence may develop from partial denervation of the striated urethral and external anal sphincter muscles. Entrapment of S3 and/or S4 branches that innervate the coccygeus and gluteus maximus muscles potentially may lead to postoperative pelvic floor dysfunction and gluteal pain, respectively. Pelvic floor dysfunction may manifest as dyspareunia or defecatory or voiding dysfunction from coccygeus or levator ani muscle irritation.
Given the high rates of transient gluteal and/or thigh pain that have been reported after SSLF, these findings should always be part of the discussion during the consent process. Similar to suggestions provided by Montoya et al
in the treatment of patients after uterosacral ligament suspension, daily and targeted questioning about unilateral or bilateral buttock pain and associated symptoms, such as radiation to the posterior thigh or perineum, should be incorporated in the postoperative care. When pain is elicited, gait should be observed, and a neurological assessment should be performed. Prompt suture removal should be considered strongly in those patients with severe gluteal pain that radiates to the posterior thigh or in those with motor deficits, because these findings suggest disruption of the sciatic nerve. In such cases, prompt suture removal should prevent prolonged recovery and long-term disability. In the absence of motor deficits or radiculopathy, pain generally resolves or improves within 4–6 weeks, and patients can be reassured and closely observed.
Limitations of this study are those that are inherent to any cadaver study; the effects of tissue degradation and absence of physiologic muscle tone may alter findings. In addition, all of our subjects were white, of advanced age, and had a lower body mass index, which may limit the generalizability of our findings to other patient populations. Despite these limitations, we carefully examined the nerves that are associated with the SSL through a combined pelvic and gluteal approach, and our findings may have important clinical implications in the genesis of gluteal pain that is observed commonly after SSLF.
Entrapment or irritation rather than transection or laceration of the sacral nerves that supply the coccygeus muscle or those that course between the SSL and STL may be mechanisms that contribute to the transient nature of gluteal pain after SSLF. Because nerves would likely be entrapped as part of a larger tissue purchase, irritation is likely to subside with time.
The higher rates of reported gluteal pain with the use of the Capio device
compared with other ligature carriers may be explained by several mechanisms. First, a deeper depth of penetration into the C-SSL may be achieved with this device. Second, direct exposure of the ventral surface of the coccygeus muscle and covering fascia may be limited; thus, the nerve to the coccygeus muscles may be entrapped more frequently. Third, if 4 separate needle punctures are placed into the ligament, a wider extent of the ligament is used, and a closer proximity to the ischial spine may be reached. This latter theory may increase the risk of pudendal nerve perforation or entrapment, because this nerve courses on the dorsal surface on the SSL, just medial to the ischial spine. Interestingly, Unger and Walters
reported greater need for intervention for gluteal pain when 4 sutures were placed in the ligament compared with 2 or 3 sutures.
Branches from S3 and/or S4 that innervate the coccygeus muscles and those coursing between the sacrospinous and STLs to supply the gluteus maximus muscles or surrounding skin likely are implicated in postoperative gluteal pain that commonly is reported after SSLF. We believe that entrapping or “irritating” the nerve to the coccygeus is largely unavoidable, given the nerves’ small size and anatomic course in a deep pelvic space filled with abundant loose connective tissue. Careful exposure and visualization of the anterior surface of the C-SSL complex may allow visualization and avoidance of larger caliber nerves. However, many surgeons prefer to limit the extent of the exposure to reduce the risk of bleeding from vessel avulsion. We continue to support suture placement at the midportion of the ligament, 2–3 cm from the ischial spine, because suture placement too close to the sacrum may lead to S4 nerve entrapment and placement too close to the ischial spine may lead to pudendal nerve and/or vessel injury. A thorough understanding of the complex anatomy surrounding the SSL, limiting the depth of needle penetration into the ligament, and avoiding the extension of needle exit or entry point above the upper extent of SSL may reduce nerve entrapment and postoperative gluteal pain and other neurologic sequelae.
Gluteal and posterior thigh pain in the postoperative period and the need for intervention after sacrospinous ligament colpopexy.