The sacrospinous ligament (small or anterior sacrosciatic ligament) is a thin, triangular

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

in the

human pelvis The pelvis (plural pelves or pelvises) is the lower part of the Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pel ...

. The base of the ligament is attached to the outer edge of the

sacrum The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part ...

and

coccyx The coccyx ( : coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates (e.g. humans and othe ...

, and the tip of the ligament attaches to the

spine of the ischium The ischial spine is part of the posterior border of the body of the ischium bone of the pelvis. It is a thin and pointed triangular eminence, more or less elongated in different subjects. Structure The pudendal nerve travels close to the isch ...

, a bony protuberance on the

. Its fibres are intermingled with the

sacrotuberous ligament The sacrotuberous ligament (great or posterior sacrosciatic ligament) is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends. Structure It runs from the sacrum (the lower ...

Structure

The

passes behind the sacrospinous ligament. In its entire length, the sacrospinous ligament covers the equally triangular

coccygeus muscle The coccygeus muscle or ischiococcygeus is a muscle of the pelvic floor, located posterior to levator ani and anterior to the sacrospinous ligament. Structure The coccygeus muscle is posterior to levator ani and anterior to the sacrospino ...

, to which its closely connected.Gray's Anatomy 1918

Function

The presence of the ligament in the

greater sciatic notch The greater sciatic notch is a notch in the ilium (bone), ilium, one of the bones that make up the human pelvis. It lies between the posterior inferior iliac spine (above), and the ischial spine (below). The sacrospinous ligament changes this notch ...

creates an opening (

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

), the

greater sciatic foramen The greater sciatic foramen is an opening (foramen) in the posterior human pelvis. It is formed by the sacrotuberous and sacrospinous ligaments. The piriformis muscle passes through the foramen and occupies most of its volume. The greater sci ...

, and also converts the

lesser sciatic notch Below the ischial spine is a small notch, the lesser sciatic notch; it is smooth, coated in the recent state with cartilage, the surface of which presents two or three ridges corresponding to the subdivisions of the tendon of the Obturator internus ...

into the

lesser sciatic foramen The lesser sciatic foramen is an opening (foramen) between the pelvis and the back of the thigh. The foramen is formed by the sacrotuberous ligament which runs between the sacrum and the ischial tuberosity and the sacrospinous ligament which runs b ...

.Platzer (2004), p 188 The greater sciatic foramen lies above the ligament, and the

lies below it. The

pudendal vessels The pudendal arteries are a group of arteries which supply many of the muscles and organs of the pelvic cavity. The arteries include the internal pudendal artery, the superficial external pudendal artery, and the deep external pudendal artery. Th ...

and

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

pass behind the sacrospinous ligament directly medially and inferiorly to the ischial spine. The

inferior gluteal artery The inferior gluteal artery (sciatic artery), the smaller of the two terminal branches of the anterior trunk of the internal iliac artery, is distributed chiefly to the buttock and back of the thigh. It passes down on the sacral plexus of nerves a ...

, from a branch of the

internal iliac artery The internal iliac artery (formerly known as the hypogastric artery) is the main artery of the pelvis. Structure The internal iliac artery supplies the walls and viscera of the pelvis, the buttock, the reproductive organs, and the medial compart ...

, pass behind the sciatic nerve and the sacrospinous ligament and is left uncovered in a small opening above the top of the sacrospinous ligament. The coccygeal branch of the inferior gluteal artery passes behind the mid-portion of the sacrospinous ligament and pierces the sacrotuberous ligament at multiple locations. The main body of the inferior gluteal artery leaves the pelvis posteriorly to the upper border of the sacrospinous ligament, to follow the inferior portion of the sciatic nerve out of the greater sciatic foramen.Thompson ''et al.'' (1999) The main function of the ligament is to prevent rotation of the ilium past the

. Laxity of this ligament and the sacrotuberous ligament allows this rotation to occur. Stresses to these ligaments occur most often when leaning forward or getting out of a chair.

Clinical significance

Vaginal prolapse Pelvic organ prolapse (POP) is characterized by descent of pelvic organs from their normal positions. In women, the condition usually occurs when the pelvic floor collapses after gynecological cancer treatment, childbirth or heavy lifting. In m ...

uterine prolapse Uterine prolapse is when the uterus descends towards or through the opening of the vagina. Symptoms may include vaginal fullness, pain with sex, trouble urinating, urinary incontinence, and constipation. Often it gets worse over time. Low back ...

may occur in women when other pelvic ligaments and supportive structures are weakened. One treatment is sacrospinous fixation. In this surgery, the apex of the

vagina In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...

is sutured to the sacrospinous ligament, which may offer a sturdier support than weakened pelvic ligaments, ideally preventing further

prolapse In medicine, prolapse is a condition in which organs fall down or slip out of place. It is used for organs protruding through the vagina, rectum, or for the misalignment of the valves of the heart. A spinal disc herniation is also sometimes ca ...

.Vasavada ''et al.'' (2004), p 661

Additional images

File:Gray1243.png , Nélaton’s line and Bryant’s triangle. File:Gray320.png, Articulations of pelvis. Posterior view.

Notes

References

* * (ISBN for the Americas 1-58890-159-9.) *

External links

* - "Posterior view of the bones and ligaments of the hip joint."
Johns Hopkins
{{Authority control Ligaments of the torso