The Sacrospinous ligament (small/anterior sacrosciatic ligament of the sacroiliac joint) is a pelvic ligament. It is a thin triangular band and about 3.8-4.6cm in length.
The sacrospinous ligament's fibers are intermingled with the sacrotuberous ligament. Posteriorly, the sacrotuberous ligament passes behind the sacrospinous ligament. Anteriorly, The sacrospinous ligament covers the coccygeus muscle. It is attached from the spine of the ischium and the outer edge of the sacrum and coccyx.
The sacrospinous ligament acts as a border for the greater and lesser sciatic foramen. The greater sciatic foramen lies above the ligament giving way for superior gluteal nerves and vessels to emerge from the pelvis while acting as a passage for the inferior gluteal vessels and nerve, sciatic and posterior femoral cutaneous nerves to pass through and exit the pelvis.
The lesser sciatic foramen is below the ligament, transmitting the tendon of the obturator internus, its nerve, and the internal pudendal vessels and nerve
The sacrospinous and sacrotuberous ligaments assist in pelvic stability. The ligament works with the sacrotuberous ligament to prevent rotation of the illum past the sacrum thus preventing excessive twisting of the pelvis, low back pain, and SIJ strain.
Sacrospinous fixation/ Illeococcygeus suspension is a procedure where the apex of the vagina is sutured to the sacrospinous ligament. this procedure is recommended to patients with uterine and vaginal prolapse as it may offer sturdier support than the weakened pelvic prolapse.
Pudendal nerve entrapment between the sacrotuberous and sacrospinous ligament is one of the common causes of pudendal entrapment neurological manifestations that can cause pelvic pain. With a tight ligament, the pain is referred down to the central aspect back of the thigh.
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