spoke

As spoke (Latin radius) a bone of the forearm is called. The radius lies on the side of the thumb and is stronger in mammals than the opposite ulna. The radius is a long bone.

What is a spoke?

Anatomical graphics with outward and inward rotation of the forearm. Click to enlarge.

Of the radius is a long bone in the forearm, which in German-speaking countries is often called spoke is titled. According to assumptions, this name is based on the similarity that the radius exhibits to the spoke of a wagon wheel.

The long bone is connected to the upper arm and runs to the bones of the wrist (lat. Ossa carpalia). Like almost every other human long bone, the radius is divided into three sections: the radial head, which connects to the upper arm (Caput radii), the following radius neck (Collum radii) and the shaft or body of the radius (Corpus radii).

Anatomy & structure

In anatomy, the spoke is divided into three sections. It consists of the radius head, the radius neck and the radius body or shaft.

The upper end of the spoke is directed towards the middle of the body and thus represents the proximal (near-body) end of the spoke (Epiphysis proximalis radii called). The spoke head is covered by cartilage and acts like a wheel that rests on the spoke neck. There is an indentation on the joint surface of the radius neck at the connection with the humerus (Fovea capitis radii called), which for the humerus head (lat. Capitulum humeri) is intended. A partial joint is located above this indentation (the Articulatio humeroradialis) that goes to the elbow joint (Articulatio cubiti) heard. The spoke head is also surrounded by a wreath-like joint surface (circumferentia articularis), which creates a movable connection to the ulna.

The middle part of the spoke is called the spoke shaft or spoke body. Together with the ulna, this part forms a unit that influences the function of the forearm. This can also be seen from the fact that these two bones are coupled to one another and thus connected in different ways.

They have a proximal, but also a remote (distal) connection to one another. Furthermore, a stable ligament stretches between the two bones (the Membrana interossea antebrachii), which extends almost through the entire forearm. This tape is also called tape-like and ensures a tight pull in the entire arm, which is created at the spoke and a kind of edge towards the ulna (Margo interosseus) forms. This edge can even be felt through the skin. There are two more borders on the front (Margo anterior) as well as on the back (Margo posterior) the spoke. The rear edge, however, is not as sharp-edged and therefore not as easy to feel as there is less tension on it. The radius widens steadily from the center of the body so that the lower end is an articular surface for the carpal bones (Ossa carpi) having. A protruding bone protrudes from the side for the wrist. Medicine calls this projection the stylus process (lat. Radial styloid process). Here the muscle of the upper arm spoke (the Brachioradialis muscle) on. The distal end of the spoke (Epiphysis distalis radii called) also has a notch (lat. Ulnar incisura), which together with the ulna forms the distant spoke-ulnar joint.

Function & tasks

The spoke has two important functions and thus tasks: On the one hand, it represents a part of the wrist. As a result, it also influences the musculoskeletal system from this. On the other hand, the radius belongs to the elbow joint and also ensures that it can be moved within the known framework. Overall, however, the spoke represents a connection between the upper arm and the wrist and only supports the wrist and elbow joint in their tasks.

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Illnesses & ailments

The most common types of injury and disease that can affect the spoke is a fracture. Both usually occur as a result of trauma caused by an accident or other external influences. In older people or people with a disease of the bone substance, a fracture of the spoke can also be caused by wear and tear.

In addition, the radius is usually also affected if the opposite ulna suffers a break or fracture. This is due to the fact that both bones partially stabilize and can only fulfill their full function together. A fracture or fracture of the spoke is usually stabilized for several weeks with a plaster of paris or a splint so that the bone can heal.

The radius can also be affected by an Essex-Lopresti injury or subluxation of the radial head. Radial head subluxation is a joint blockage that mostly affects children.

An Essex Lopresti injury is an extremely rare combination of injuries to the arm, most of which also affect the ulna and radial head. Here too, severe trauma is often the cause. However, the healing process is more complicated and tedious. Often parts of the head have to be restored through an operation in order to be able to guarantee the function of the spoke and the affected joint again.