The sacrospinous ligament is a flat, triangular band of connective tissue that stretches from the lateral edge of the sacrum and coccyx to the ischial spine on each side of the pelvis. It sits deep within the buttock, hidden beneath layers of muscle, and most people never think about it unless a surgeon brings it up. Despite its obscurity, this ligament plays a meaningful role in stabilizing the pelvis and has become one of the most important anatomical landmarks in pelvic reconstructive surgery, particularly for treating pelvic organ prolapse.
Where It Sits and What It Looks Like
The sacrospinous ligament fans out from the lower sacrum and coccyx, narrowing as it travels laterally to attach at the ischial spine, a bony projection you can sometimes feel deep in the buttock. It lies just in front of the sacrotuberous ligament, and the two overlap so closely that some anatomists describe them as partially fused. The ligament is intimately connected to the coccygeus muscle, which lies directly on its pelvic surface. Surgeons often refer to this combined structure as the “sacrospinous ligament–coccygeus complex” because, in practice, it is difficult to separate the ligament fibers from the muscle during dissection.
In humans, the pelvic floor muscles and fascia insert on the ischial spines either directly or through the sacrospinous ligament and the tendinous arch of the pelvic fascia. This arrangement creates a medial pull on the ischial spines, producing a more rigid and narrower pelvic floor that helps support the pelvic organs against gravity in our upright posture.1PubMed Central. Evolution of the ischial spine and of the pelvic floor in the Hominoidea
Its Role in Pelvic Stability
The sacrospinous ligament contributes to holding the sacrum in place relative to the rest of the pelvis. Along with the sacrotuberous ligament, it resists the tendency of the sacrum to rotate forward under body weight. A computational study of pelvic load distribution found that the stiffness of the sacrotuberous and sacrospinous ligaments together influenced how much the pelvis moved under load, though the sacroiliac joint cartilage and the interosseous sacroiliac ligament had even larger effects on pelvic motion.2PubMed. Ligamentous influence in pelvic load distribution In short, the sacrospinous ligament is one member of a team of structures that keep the pelvis from flexing and shifting during everyday activities like walking, sitting, and lifting. It is not the star player, but removing or weakening it changes how forces travel through the pelvic ring.
The Nerves and Blood Vessels Next Door
What makes the sacrospinous ligament so consequential for surgeons is not the ligament itself but what runs right next to it. The pudendal nerve, the pudendal artery, and branches of the inferior gluteal artery all pass within millimeters of the ligament or directly across its surface. Understanding this crowded neighborhood is critical for any procedure that involves stitching into the ligament.
Cadaver dissections have repeatedly mapped these relationships. In one study, the pudendal nerve sat right at the ischial spine, with a median distance of zero millimeters from the spine itself.3PubMed. Inferior gluteal and other nerves associated with sacrospinous ligament: a cadaver study The internal pudendal artery passes behind or just medial to the ischial spine, and the inferior gluteal artery courses above the top edge of the ligament, leaving only a narrow window of about 3 to 5 millimeters where the vessel is exposed between the upper border of the ligament and the sciatic nerve plexus above.4PubMed. Anatomy of pelvic arteries adjacent to the sacrospinous ligament: importance of the coccygeal branch of the inferior gluteal artery The inferior gluteal artery averaged about 24 millimeters from the ischial spine along the upper border of the ligament.5PubMed. Neurovascular anatomy of the sacrospinous ligament region in female cadavers: Implications in sacrospinous ligament fixation
Because of this anatomy, surgeons placing sutures for pelvic prolapse repair aim for a spot roughly two centimeters medial to the ischial spine, toward the sacral end of the ligament. Research on this medial portion confirms it is the most suitable zone for suture placement to minimize nerve and vessel injuries, though even in this area, small nerves supplying the coccygeus and levator ani muscles may cross the ligament surface.6SpringerLink / International Urogynecol J. The anatomy of the sacrospinous ligament: how to avoid complications related to the sacrospinous fixation procedure for treatment of pelvic organ prolapse
Sacrospinous Ligament Fixation for Pelvic Organ Prolapse
The procedure that has made this ligament famous in gynecologic surgery is sacrospinous ligament fixation, commonly abbreviated SSLF. It is a vaginal surgery designed to re-support the top of the vagina (or the uterus, in a uterus-preserving version) when the pelvic floor has weakened enough to allow organs to drop. The basic idea is straightforward: a surgeon passes sutures through the sacrospinous ligament and then anchors the vaginal apex to it, essentially giving the vagina a new point of suspension inside the pelvis.
The approach is performed entirely through the vagina. The surgeon opens the back wall of the vagina, works through the tissue planes to reach the ischial spine and palpate the ligament, then places sutures through the ligament–coccygeus complex about two centimeters medial to the spine. Those sutures are then attached to the vaginal cuff. Once healing is complete, the vaginal epithelium fuses with the ligament, and the vault stays elevated.7PubMed Central. Transvaginal Sacrospinous Ligament Fixation for Pelvic Organ Prolapse Stage III and Stage IV Uterovaginal and Vault Prolapse The suspension is typically done on the patient’s right side because a right-handed surgeon can pass the needle more easily, and retracting the rectum to that side tends to be more straightforward.
SSLF is considered a “native tissue” repair because it does not use synthetic mesh. This distinction matters because mesh-based repairs carry their own set of complications, and regulators in several countries have restricted or banned certain types of transvaginal mesh. SSLF offers patients a mesh-free alternative with a long track record.
How It Compares to Other Prolapse Surgeries
SSLF is not the only way to re-support a prolapsed vaginal vault. The two procedures it is most frequently compared to are uterosacral ligament suspension (USLS), another native-tissue vaginal approach, and abdominal sacrocolpopexy (ASC), which uses mesh placed through an abdominal incision or laparoscopically.
SSLF Versus Uterosacral Ligament Suspension
A meta-analysis comparing SSLF to USLS found no meaningful difference in surgical success rate, anatomical outcomes, recurrence, or overall complication rates between the two procedures.8PubMed. Sacrospinous Ligament Fixation vs Uterosacral Ligaments Suspension for Pelvic Organ Prolapse: A Systematic Review and Meta-Analysis The OPTIMAL trial, a large randomized study, followed patients for five years and estimated failure rates of about 70% for SSLF and about 62% for USLS, though the difference was not statistically significant.9PubMed Central. Effect of Uterosacral Ligament Suspension vs Sacrospinous Ligament Fixation With or Without Perioperative Behavioral Therapy for Pelvic Organ Vaginal Prolapse on Surgical Outcomes and Prolapse Symptoms at 5 Years in the OPTIMAL Randomized Clinical Trial Those failure numbers sound alarming, but the definition of “failure” in prolapse research is broad, including any measurable anatomical descent beyond a threshold, even if the patient has no symptoms and needs no further treatment. Many women who meet the study definition of anatomical failure are functionally fine.
A retrospective database study found that USLS was associated with about 25% lower odds of a composite complication outcome (excluding urinary tract infections) compared with SSLF, but USLS itself had a higher rate of urinary tract infections. There was no significant difference in serious complications, readmission, or reoperation between the two.10Urogynecology. Complications After Uterosacral Ligament Suspension Versus Sacrospinous Ligament Fixation at Vaginal Hysterectomy: A Retrospective Cohort Study of the National Surgical Quality Improvement Program Database For most patients, the choice between SSLF and USLS comes down to surgeon experience, the specific anatomy of the prolapse, and patient preference rather than a clear superiority of one approach.
SSLF Versus Abdominal Sacrocolpopexy
The comparison to sacrocolpopexy is more lopsided in certain metrics. A meta-analysis found that sacrocolpopexy had a higher overall success rate (about 91% versus 88% for SSLF), lower recurrence, and substantially less painful sex afterward. SSLF, however, offered shorter operating times (about 25 minutes shorter on average), less bleeding, fewer wound infections, and fewer gastrointestinal complications.11PubMed Central. Comparison of the effectiveness of sacrospinous ligament fixation and sacrocolpopexy: a meta-analysis A separate study comparing laparoscopic sacrocolpopexy to SSLF found that both achieved similar apical success rates and that both groups had significant quality-of-life improvements, though the SSLF group actually showed greater improvements in bowel and urinary function.12PubMed. Medium-term outcomes of laparoscopic sacrocolpopexy or sacrohysteropexy versus vaginal sacrospinous ligament fixation for middle compartment prolapse
A systematic review attempting to determine whether mesh-based sacrocolpopexy or native-tissue vaginal repair led to fewer reoperations found highly inconsistent results across studies. Some trials showed more reoperations after sacrocolpopexy, others showed more after SSLF, and the evidence quality was rated very low.13PubMed Central. Sacrocolpopexy Compared With Native Tissue Vaginal Repair: A Systematic Review and Meta-analysis The upshot is that sacrocolpopexy tends to produce slightly better anatomical outcomes, but SSLF avoids mesh-related risks and offers a quicker, less invasive procedure. Neither is universally superior.
One Side or Both
SSLF is traditionally performed on one side only (unilateral), but some surgeons have begun performing bilateral fixation, attaching the vaginal vault to the sacrospinous ligament on both sides of the pelvis. The theoretical advantage is a more midline suspension, since unilateral fixation can pull the vaginal apex slightly toward the side of the repair. A study comparing the two approaches using a minimally invasive anchoring device found no significant difference in anatomical improvement, recurrence, complication rates, blood loss, or operative time between unilateral and bilateral fixation.14PubMed Central. Comparison of Unilateral and Bilateral Sacrospinous Ligament Fixation Using Minimally Invasive Anchorage The bilateral approach does not appear to offer clear advantages, but it also does not seem to add risk, so some surgeons prefer it for patients whose anatomy would benefit from more symmetric support.
Sexual Function After SSLF
One of the first questions patients ask about prolapse surgery is whether it will affect sexual function. The evidence here is generally reassuring. A prospective multicenter study using validated questionnaires found that overall sexual function scores improved after SSLF, with improvements in desire, arousal, orgasm, satisfaction, and pain. Among women who had painful sex before surgery, nearly half had complete resolution of that pain. No women who were pain-free before surgery developed new pain afterward.15Scientific Reports. Sexual function after Anchorsure repair of sacrospinous ligament suspension in patients with pelvic organ prolapse: a prospective multicenter study
Earlier studies reported similar findings. One found that sexually active patients reported either improvement or no change in sexual function after SSLF unless vaginal narrowing occurred, which caused inability to have intercourse in a small number of patients.16PubMed. Sexual function after sacrospinous ligament fixation for vaginal vault prolapse Another reported that three patients developed new painful sex after the procedure, but the pain resolved in two of the three after the offending stitch was removed.17PubMed. Sexual function after sacrospinous fixation for vaginal vault prolapse: bad or mad? Overall, the risk of sexual function worsening is low, and the more common outcome is improvement because the prolapse itself was interfering with sex.
What Makes Prolapse Come Back After Repair
Prolapse recurrence after SSLF does happen, and the risk factors are worth knowing. A prospective cohort study found that having a body mass index above 25 was a strong predictor, carrying roughly six times the risk of apical prolapse recurrence. Developing postoperative complications also dramatically raised recurrence risk. On the protective side, undergoing vaginal hysterectomy at the same time as SSLF was associated with much lower recurrence.18PubMed Central. Recurrence Rate and Risk Factors for Apical Prolapse After Sacrospinous Ligament Fixation: A Prospective Cohort Study
A separate analysis looking at risk factors across both SSLF (with uterus preservation) and USLS found that higher BMI, smoking, and the degree of anterior wall prolapse before surgery all independently predicted failure. Interestingly, vaginal hysterectomy in this study was a risk factor for posterior wall recurrence when compared with uterus-sparing sacrospinous fixation.19American Journal of Obstetrics & Gynecology. Risk factors for pelvic organ prolapse recurrence after sacrospinous hysteropexy or vaginal hysterectomy with uterosacral ligament suspension This apparent contradiction between the two studies likely reflects different definitions of failure and the fact that uterus preservation versus removal shifts the mechanical stresses in the pelvis in different ways depending on which compartment you measure.
Pregnancy After Sacrospinous Fixation
A question that occasionally arises, especially for younger women with prolapse, is whether pregnancy and delivery are possible after SSLF. The data are limited but suggest it is feasible. An early case series reported six successful vaginal deliveries in five patients who had undergone sacrospinous fixation, with normal anatomy restored in all but one.20PubMed. Successful pregnancies and vaginal deliveries after sacrospinous uterosacral fixation in five of nineteen patients A more recent study looking specifically at sacrospinous hysteropexy (where the uterus is preserved and suspended) found that pregnancies reached at least 37 weeks, though all eight pregnancies in that series were delivered by cesarean section.21European Journal of Obstetrics & Gynecology and Reproductive Biology. Evaluation of pregnancy outcomes following transvaginal sacrospinous hysteropexy Mode of delivery after SSLF remains a judgment call. Some clinicians recommend cesarean delivery to protect the repair, while others feel that vaginal delivery is reasonable if the patient’s anatomy has healed well.
Ossification and Other Rare Problems
The sacrospinous ligament can, in rare cases, turn to bone. This process, called ossification, has been documented in isolated case reports. In one such case, the ossified ligament compressed the sciatic nerve, causing pain radiating down the leg. Surgical removal of the bony ligament eliminated the symptoms. The suspected cause was that abnormal mechanical stresses on the ligament triggered the tissue to transform into bone through a process called osseous metaplasia.22Elsevier / Orthopaedics & Traumatology: Surgery & Research. Sciatic nerve compression related to ossification of the sacrospinous ligament secondary to pelvic balance abnomalities
Another clinical context where the sacrospinous ligament matters is pudendal nerve entrapment. The pudendal nerve passes between the sacrospinous and sacrotuberous ligaments before entering the pudendal canal, and compression at this point can cause chronic pain in the genital, anal, and perineal areas. The hallmark symptom is pain that appears when sitting and eases when standing or lying down. Diagnostic nerve blocks and, in refractory cases, surgical release of the ligament can provide relief.
Imaging the Sacrospinous Ligament
Seeing the sacrospinous ligament on imaging is not straightforward. On standard MRI sequences, the ligament’s signal can appear discontinuous on routine axial slices, making injuries easy to miss. Oblique sagittal scanning provides a much clearer view and allows more reliable assessment of ligament integrity, which matters in the context of pelvic fractures where ligamentous injury changes the stability classification and treatment plan.23ResearchGate. Magnetic resonance imaging for the evaluation of ligamentous injury associated with pelvic anterior–posterior compression fracture In prolapse surgery planning, the ligament is typically identified by palpation rather than imaging, since the surgeon accesses it through a vaginal approach and uses the ischial spine as a tactile landmark.
Learning to Operate on It Safely
SSLF is a technically demanding procedure because the ligament sits deep in the pelvis, visibility is limited, and critical nerves and vessels are right next door. Simulation training has become increasingly recognized as essential for surgeons learning the technique. A cadaveric simulation study found that while trainees felt more confident about the procedure’s steps and anatomy after practice, their existing theoretical knowledge did not always translate into safe suture placement, suggesting that hands-on repetition is needed beyond didactic training.24PubMed. A Cadaveric Simulation Model to Teach Suture Placement During Sacrospinous Ligament Fixation Cadaver labs allow trainees to practice identifying the ischial spine, palpating the ligament, and placing sutures at the correct distance from neurovascular structures before performing the procedure on patients. Suture-capturing devices have also been developed to standardize the point of needle entry and reduce the risk of hitting nerves or vessels, and cadaveric studies have been used to evaluate how close these devices place sutures relative to surrounding anatomy.25PubMed. Cadaveric Nerve and Artery Proximity to Sacrospinous Ligament Fixation Sutures Placed by a Suture-Capturing Device