Generality
The ischium is one of the three bony components of the ilium, along with the ilium and pubis.
Precisely, it represents the lower and posterior part of the iliac bone, which is the hip bone. Located inferior to the ilium and posterior to the pubis, the ischium has three anatomically relevant sections: the ischium body, the superior branch of the ischium and the inferior branch of the ischium.
Among the anatomical structures that distinguish the aforementioned ischium sections, the following deserve a mention: the acetabulum (N.B: the ischium forms a part of it), the ischial spine, the minor ischial notch, the obturator hole and the ischial tuberosity.
Through the formation of the acetabulum, the ischium contributes to the constitution of a very important joint: the hip joint.
The pathologies of the ischium include: avulsion fractures of the ischial tuberosity, pathologies of the hip and ischial bursitis.
What is the ischium?
The ischium is one of the three bony portions that make up the iliac bone.
The other two portions of the ilium are the ilium and the pubis.
WHAT IS ILIAC BONE?
The iliac bone, also known as the hip bone, is the even and symmetrical bone which, together with the sacrum and the coccyx, constitutes that anatomical structure identified with the name of pelvic girdle.
POSITION OF THE ISCHIO WITH RESPECT TO ILIO AND PUBE
The ischium represents the lower and posterior part of the iliac bone.
It resides inferior to the ilium - which is the upper portion of the iliac bone - and behind the pubis - which is the lower, anterior portion of the ilium.
Briefly, the ilium is important for its relationship with the sacrum: with the latter it forms the sacro iliac joint. The pubis, on the other hand, is important because it makes contact with the pubis of the contralateral iliac bone, forming a joint known as the pubic symphysis.
THE ISCHIO IS PART OF THE BONES OF THE PELVIS
The iliac bone - with its three sections ilium, ischium and pubis - and the combination of sacro-coccyx represent the so-called pelvic bones.
Anatomists call the pelvis, or pelvis, or pelvic region, the lower torso of the human body.
Located between the abdomen and the thighs, the pelvis comprises, in addition to the pelvic bones: the so-called pelvic cavity, the so-called pelvic floor and the so-called perineum.
Anatomy
Anatomists recognize three regions of some importance in the ischium: the body of the ischium, the upper branch of the ischium and the lower branch of the ischium.
BODY OF THE ISCHIO
The body of the ischium is the bony region bordering the ilium and under which the upper and lower branches of the ischium develop in order.
The body of the ischium comprises an external surface, an internal surface and a posterior border:
- There outer surface of the body of the ischium forms part of the acetabulum, to be precise 2/5 of the latter. human: the hip joint;
- There inner surface of the body of the ischium forms part of the wall of the small pelvis. The small pelvis is the lower portion of the pelvic cavity, hence the lower part of the pelvis.
In fact, it is the back of the outer surface; - The rear edge of the body of the ischium is anatomically important, because it has a triangular eminence, called the ischial spine, and a small hollow just below the ischial spine, called the minor ischial incisura.
The deep transverse muscle of the perineum, the superficial transverse muscle of the perineum and some fibers of the internal obturator muscle originate from the body of the ischium.
UPPER BRANCH OF THE ISCHIO
The superior branch of the ischium (or descending branch) develops inferiorly to the body of the ischium, with a slightly backward orientation.
The superior branch of the ischium has three anatomically interesting portions: an external surface, an internal surface and a posterior surface.
- Outer surface. Delimited anteriorly by the so-called obturator foramen, the external surface gives rise to some fibers of the external obturator muscle, to some fibers of the quadratus muscle of the femur and to some fibers of the adductor major muscle;
- Internal surface. It is the back of the external surface, therefore it has a similar shape to the latter and, at the front, it is delimited by the obturator hole.
Constituting part of the wall of the small pelvis, the internal surface is the seat of origin of some fibers of the transverse muscles of the perineum, some fibers of the ischiocavernosus muscle and some fibers of the internal obturator muscle; - Posterior surface. It is the portion in which a bony prominence is recognizable, called ischial tuberosity (or ischium tuberosity).
On the ischial tuberosity, the human being places the weight of the body on it when it is in a sitting position.
LOWER BRANCH OF THE ISCHIO
Thin and flattened, the lower branch of the ischium (or ascending branch) is the region that continues the upper branch and connects to the pubis (or pubic bone); to be precise, it connects to the lower branch of the pubis. at the pubis, it forms a structure called the ischio-pubic branch. The ischio-pubic branch contributes significantly to the constitution of the aforementioned obturator hole. The obturator nerve, the obturator artery and the obturator vein pass through the obturator foramen.
Returning to the inferior branch of the ischium, this includes four anatomically interesting portions: the external surface, the internal surface, the medial border and the lateral border.
- Outer surface. On the external surface of the inferior branch of the ischium some fibers of the external obturator muscle and some fibers of the great adductor muscle originate;
- Internal surface. In fact it is the back of the outer surface. It forms part of the wall of the small pelvis;
- Medial border. It is thick, rough and slightly everted. It delimits part of the opening formed by the small pelvis.
It has two ridges, one external and one internal, which are the continuation of two other ridges located on the lower branch of the pubis.
On the external crest s "inserts the deep layer of the so-called Colles fascia; on the internal ridge, s" inserts the lower fascia of the urogenital diaphragm.
At a certain point in their path, the two crests join: this happens at the point of origin of the transverse muscles of the perineum; - Side border. It is thin and sharp. Contributes to the formation of the obturator hole.
LIGAMENTS
The ischium inserts into the terminal end of the sacrotuberous ligament and the initial end of the sacrospinous ligament.
Formed by three large bands of fibrous tissue, the sacrotuberous ligament plays an important stabilizing action during the nutation movements of the sacrum.
Thinner than the sacrotuberous ligament, the sacrospinous ligament has the task of opposing the forward inclination of the sacrum, with respect to the two iliac bones.
Origin
Term
Sacrotuberous ligament
Lateral margin of the wing of the sacrum
Ischial tuberosity
Sacrospinous ligament
Ischial spine
In part, on the lateral margin of the "wing of the sacrum" and, in part, on the transverse process of the coccyx
Development
The three sections of the iliac bone - ilium, ischium and pubis - are fused together.
The fusion of the aforesaid sections is a process that, in the human being, takes place around the 14th / 15th year of life.
Function
The bones of the pelvis, of which the ischium is in fact one of the various components, have at least three noteworthy tasks:
- Support the upper body;
- Connect the axial skeleton (which includes the skull, the vertebral column, the rib cage, etc.) to the lower limbs;
- Giving insertion to muscles, ligaments and tendons, essential for walking and more.
ISCHIO AND HIP JOINT
By participating in the formation of the acetabulum, the ischium enters the list of components that make up the hip joint.
The hip is important because it allows the human being to stand upright, walk, run, jump, etc.
Please note: all three portions of the ilium participate in the formation of the acetabulum, therefore not only the ilium but also the ischium and pubis.
Associated pathologies
Among the pathologies that can affect the ischium, avulsion fractures of the ischial tuberosity, hip pathologies, with specific involvement of the acetabulum, and ischial bursitis certainly deserve a mention.
HIP PATHOLOGIES
The two most important pathologies of the hip, which can derive from an anomaly of the acetabulum, are: coxarthrosis (or osteoarthritis of the hip) and congenital dysplasia of the hip.
ISCHIATIC BUNCH
Ischial bursitis is inflammation of the synovial bursa located between the gluteus maximus muscle and the ischial tuberosity. Typically, this condition is caused by sitting for many hours on hard surfaces.
AVULSION FRACTURES OF THE ISCHIO
Doctors define avulsion fractures as all bone fractures that arise as a result of a sharp and violent muscle contraction.
Avulsion fractures of the ischial tuberosity are typical injuries of those who practice sports, as these individuals are more exposed, than sedentary people, to muscle problems (contractions, strains, etc.).
Sports activities in which it is easiest to get a ischium avulsion fracture are: soccer, American football, basketball, martial arts and obstacle course.
