Radius bone

The radius bone is a large bone present in the forearm of a human. It extends from the lateral side of the elbow and runs parallel to another large bone of the forearm called the ulna. It is a long bone and is shorter than the ulna. Radius bone form joints at the elbow and at the wrist.

At the elbow, the radius joins with capitulum and also joins with the ulna at the radial notch. At the wrist, it joins with the ulna bone.

structure

This bone has a proximal part, distal part, and a body. The upper or proximal part consists of a head that articulates with the ulna and humerus. It’s upper part also consists of the neck and radial tuberosity. The distal or the lower part is quadrilateral in shape and possess the articular surfaces for the ulna, scaphoid, and the lunate bones. It’s lower part also consists of the styloid process and the Lister tubercle.

The interosseous membrane originates from its body and attaches the ulna and radius.

1.The proximal or upper region

The upper part consists of a head, neck, and radial tuberosity.

Head
The head is medially thicker, and a disc-shaped structure. It consists of a concave articulating surface. The thicker part of the head of the radius takes parts in the proximal radioulnar joint.

Neck
It is a narrow region that is present between the head and tuberosity.

Tuberosity
It is a bony projection that provides the attachment site to biceps brachii muscle.

 

2.Radius shaft

The shaft of this bone is the part that is present between the proximal and distal parts. From proximal to distal it expands in diameter. The shaft has three surfaces and borders. On its lateral surface, a small roughened area is present to which pronator trees muscle is attached.

Borders of the shaft

There are three borders of the shaft of this bone that at the anterior border, posterior border, and the medial border.

Anterior border
This border starts below the tuberosity and runs laterally to the styloid process.

Posterior border
This border is not well defined in all the regions of the shaft except the middle third of the shaft where it is well defined.

Medial border
It is a sharp border that extends from the radial tuberosity to the triangular area on the medial side of the distal end.

Surfaces of the shaft

The shaft of this bone has three surfaces that are the anterior surface, the posterior surface, and the lateral surface.

Anterior surface. This surface is concave and is present between the anterior and medial borders.

Posterior surface
This surface of the shaft is present between the medial and posterior borders.

Lateral surface
This surface of the shaft is present between the anterior and posterior borders of the shaft.

the distal or lower part

The lower part of this bone consists of the styloid process and the ulnar notch. The styloid process is formed when the lateral surface of the radius project distally. The ulnar notch is the concavity present at the medial side of this bone. The ulnar notch takes part in the distal radioulnar joint. The distal end of the radius also has two articulating facets for the scaphoid and lunate bones.

Joints in which the radius takes place

This bone takes part in the formation of four joints that are the elbow joint, proximal radioulnar joint, wrist joint, and the distal radioulnar joint.

Elbow joint
This joint is not completely but partly formed by the head and the capitulum of the humerus.

Proximal radioulnar joint
This joint is formed by the radial head and the radial notch of the ulna.

Wrist joint
This joint is formed by the distal end of the radius and the scaphoid and lunate
bones.

Distal radioulnar joint
This joint is formed by the ulnar notch and ulna.

Development of the radius

This bone ossified from the three centers among which the two ossify the proximal and the distal regions while the other one ossifies the body. The one that ossifies the body appears in the eighth week of the prenatal development.
Borders of the shaft of the radius
There are three borders of the shaft of this bone that are the anterior border, posterior border, and the medial border.

What are the muscles attached to the radius bone?

The muscles attached to the radius bone are

1. Flexor pollicis longus muscle
2.   Flexor digitorium superficialis muscle radial head
3.   Abductor  pollicis longus
4.   Extensor pollicis brevis
5.   Biceps brachii
6.    supinator muscle
7.    Pronator teres
8.    Brachioradialis
9.     Pronator quadratus

Movement

The radius bone is mainly involved in pronation and supination.

In pronation, the lower end of this bone rotates around the ulna from the lateral side to the medial side.

In supination, the lower end of the radius moves around the ulna from the medial side to the lateral side.

Clinical notes

clinical cases

1.Radial aplasia

This is a congenital condition in which the child born either has no radius bone or short radius bone in his one or both forearms. Radial aplasia can cause difficulty for a person while performing many activities in daily life.

Radial aplasia may also affect the thumb of the hand due to which the thumb partly formed or completely absent.

2.Fractures of the radius

There are various types of fractures that occur in this bone. The fractures in the radius are more common than the ulna.  These various fractures are

1. Proximal fracture
2.  Essex Lopresti fracture
3.   Galeazzi fracture
4.   Colles fracture
5.   Smiths fracture
6.   Barton’s fracture.

3.Madelung deformity

It is a congenital disorder in which the anterior bowing of the distal end occurs.  The bowing of the distal end occurs due to the abnormal growth of the distal epiphysis. Madelung deformity occurs between the age of 10 to 14.

This bone is present on the lateral side of the forearm. To understand its sides kept the following points in your mind.

Radius bone sides determination

1. The upper head is a disc-like structure.
2.  The lower end of this bone is expanded.
3.   The medial border is the sharpest border.
4.   Radial tuberosity is present at the upper end of the medial border.
5.   The tubercle of lister is present at the lower end on the posterior surface.

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