Ischium

definition

The ischium (Os ischii) is a flat bone of the human pelvis. It borders the pubic bone (Pubis) and the iliac bone (Os ilium) and together with these forms the so-called hip bone (Os coxae). This closes the complete pelvic ring with the sacrum and thus forms the basis of the bony pelvis.

anatomy

The structure of the ischium can be divided into 3 parts, the ischial body and an upper and lower ischial branch, which merge into one another. Of the Body of the ischium the largest part the acetabulum and its posterior limitation. It has two characteristic notches on its back (Incisura ischiadica major / minor). The larger of the two ends in a sharp bone spine, which serves as the starting point for the sacrum-ischial spine ligament (Sacrospinal ligament) acts. This is part of the Sacrum-iliac joint and contributes to its stabilization. Together with another band, it also forms the boundary of the small ischial hole at the small notch, which is an important one Passage point for ducts from the pelvis to the thigh and groin region.

Together with the upper branch of the pubic bone, the upper ischial branch (Ramus superior ossis ischii) the overhead limitation of the hip hole (Obturate foramen), through which several ducts run from the pelvis to the leg.

A prominent bone edge delimits the outside of the branch from the back and serves as the point of origin of various thigh muscles. The inside is part of the bony wall of the small pelvis and also has a sharp edge in its lower part. This forms the starting point for another tether of the sacrum-iliac joint. It also serves as the point of origin for part of the pelvic floor muscles.

The lower ischial branch has an uneven surface on its outside from which the Obturator muscle externus arises. The inside is part of the bony front wall of the small pelvis and, with its bone edges, forms the starting point for connective tissue parts of the pelvic floor.

On of their At the back, the two ischial branches run together into the large ischial tuberosity (Sciatic tuberosity) out.

Sciatic tuberosity

The ischial tuberosity is a prominent bone protrusion, which forms the lower end of the bony pelvis. It has a rough surface and essentially fulfills two functions.

On the one hand, he makes that Origin point for a whole group of Muscles of the thigh and gluteus muscles, the so-called thigh flexors. These pull from there over the back of the thigh to below the knee, where they attach to the lower leg bone. They mainly serve to flex the knee joint and stretch the hips, which e.g. in movements like climbing stairs.

On the other hand, the ischial tuberosity serves as a Support point when sitting and is overlaid by an extensive pad of fat.

function

Due to its anatomical position, the ischium has three main functions.

On the one hand, as the name suggests, it serves with its large ischial tuberosity as the lowest point of the bony pelvis and thus for the Support point when sitting.

On the other hand, with its numerous bone edges and points, it functions as a Point of origin of several muscles of the thigh and the pelvic floor.

However, its main role is mainly the Stabilization of the bony pelvic ring. It fulfills this on the one hand through its firm connection with the pubic and iliac bone, on the other hand through its function as the starting point of several ligaments of the sacrum-iliac joint. These are stretched very tightly between the bones and thus provide the necessary stability in the pelvis.

Ischial pain

Ischial pain can have a variety of causes. These can best be classified according to the group of structures that are affected.

On the one hand, processes on the bone itself can be the cause of the pain. The main causes here are fractures caused by falls or accidents, inflammation of the bone tissue and tumors. In adolescents, jerky leg movements or excessive strain, e.g. by hurdles, as well as long and high jump also to so-called Apophysiolysis come. These are demolitions of the ossification centers, which play a decisive role in bone growth.

Another reason for pain in the ischium can be injuries to the connective or muscle tissue. These are mainly bruises e.g. from falls, as well as strains and muscle fiber tears from overuse. There is also frequent irritation and inflammation of the muscle tendons on the ischial tuberosity due to friction between the tendons and the bones. Inflammation of the muscles themselves is less common.

The os ischii and its adjacent structures form several passageways for nerves that run from the pelvis to the leg. These can also cause irritation and, in particular, entrapment, which can cause severe pain as a result.

Also read on this topic: Ischial tuberosity pain

Inflammation of the ischium

In principle, inflammation can develop in any of the structures on the ischium. Inflammation of the bones is rather rare. They usually arise as a result of other inflammations in the area, e.g. Inflammation of the bladder, which then spreads to the ischium. Essential inflammation of the muscles or especially their tendons of origin. These usually arise as a result of overstressing the muscles through excessive training or an unfamiliar load. Furthermore it can be too Inflammation of the so-called Bursa come. These are structures that mainly occur on joints. They are filled with liquid and serve to dampen pressure and thus relieve the joints. Bursitis is also often caused by excessive stress, but also by bacterial infections, arthritis, osteoarthritis, gout, tuberculosis or gonorrhea.

Irrespective of their localization, inflammations are usually expressed in the so-called cardinal symptoms: Swelling, redness, overheating, pain and impaired function the affected structure.

They are usually treated with nonsteroidal anti-inflammatory drugssuch as Ibuprofen® or Voltaren®, as well as immobilization and cooling. Depending on the severity of the pain, pain medication can also be given. In addition, physiotherapeutic exercises are recommended, which primarily serve to strengthen the trunk and pelvic floor muscles, as well as stretching the thigh muscles attached to the ischium. This is to prevent future inflammation and injuries from overuse.

Ischial fracture

Fractures of the ischium go usually with injuries to the pubic bone and are also called anterior pelvic ring fractures designated. They can exist as stable or unstable fractures.

As stable are fractures that are either unilateral or bilateral but without shifting the break lines. Unstable Accordingly, fractures are accompanied by a shift in the breakline.

Since the entire pelvic ring is a very robust and strong bony structure, fractures are in this area almost always the result of massive violencee.g. due to accidents or serious falls. It manifests itself in very severe pain and the loss of mobility of the leg on the affected side.

An X-ray or CT scan will be taken to confirm the fracture. The therapy usually consists of 1-2 days of strict bed rest and subsequent stress, as is possible in the context of the pain. If necessary, a belt or bandage is put on to stabilize the pelvis. Painkillers and drugs are used to prevent inflammation. Surgical intervention may be necessary depending on the type and severity of the fracture. This is the case, for example, if the break lines have to be straightened again or if, as a result of the causal force, damage to neighboring organs, e.g. originated in the kidneys or urinary tract, liver, spleen, intestine or pelvic nerves.

With adequate treatment, the fractures usually heal again without permanent damage.