Comprehensive Anatomy and Ossification of the Radius Bone

 

RADIUS

Similar to the tibia in the lower limb, the radius is the lateral bone of the forearm. It features a shaft, an upper rounded end, and a lower broad end with a styloid process.

Side Determination

1. The lower end is enlarged with a styloid process, while the upper end has a disc-shaped head and a slender neck. It exhibits a radial tuberosity around the neck.
2. The anterior surface is shaped like a thick, noticeable ridge at the bottom. Four grooves are present on the posterior surface for the extensor tendons.
3. The lower end displays a tubercle known as the Lister dorsal tubercle on the posterior side.
4. The medial margin of the shaft is the sharpest.

Features

Upper End

1. The disc-shaped head has hyaline cartilage covering it. Its superior concave surface articulates at the elbow joint with the humerus's capitulum. Additionally articular is the head's circumference. The superior radioulnar joint is created when it fits into a socket that is created by the annular ligament and the radial notch of the ulna.
2. The annular ligament's small bottom edge encloses the neck. There is no capsular attachment on the head or neck, allowing them to freely spin inside the socket.
3. Directly beneath the medial aspect of the neck is the radial tuberosity. Its anterior section is smooth, whereas its posterior part is rough.

Shaft

It features three surfaces as well as three boundaries.

Borders

• The anterior border descends near the styloid process from the anterior margin of the radial tuberosity. In the top half of the shaft, it is oblique, and in the lower half, vertical. The lowest point resembles a spiky crest. The anterior oblique line refers to the oblique portion.
• The posterior border is the anterior border's mirror image, however it is only distinctly defined in the middle third of the border. The posterior oblique line refers to the higher oblique portion.
• The medial or interosseous border is the sharpest of the three borders. The interosseous membrane is attached to it slower three-fourths. In its lower part, it forms the posterior margin of an elongated triangular area.

Surfaces

1. Between the anterior and interosseous borders is the anterior surface. Its upper portion opens to reveal an upward-directed nutrition foramen. Anterior interosseous artery branches out to become the nutritional artery.
2. Between the posterior and interosseous boundaries is the posterior surface.
3. Between the anterior and posterior boundaries is the lateral surface.
4. Its central section has a roughened area visible.

Lower End

The bone's widest region is toward the bottom. There are five surfaces on it.

1. The anterior surface resembles a thick, noticeable ridge. This surface is used to palpate the radial artery.
2. Four extensor tendon grooves are visible on the posterior surface. An oblique groove is located lateral to Lister's dorsal tubercle.
3. The ulnar notch for the ulna's head is located on the medial surface.
4. The styloid (Greek pillar) process is formed by the lateral surface being extended downward.
   
5. The lunate bone is located in a medial quadrangular area on the inferior surface, while the scaphoid bone is located in a triangular location. This area contributes to the formation of the wrist joint.

 

Attachments

1. Insert the biceps brachii (Latin for "two heads") into the rough posterior region of the radial tuberosity. A bursa covers the anterior portion of the radial tuberosity.
2. The upper portion of the lateral surface receives the supinator, which is Latin for "to bend back."
3. The middle of the lateral surface is where the pronator teres is inserted.
4. Directly above the styloid process, the brachioradialis is inserted into the lowest portion of the lateral surface.
   
5. The anterior oblique line and the top portion of the anterior border serve as the origin of the flexor digitorum superficialis' radial head.
6. The upper two-thirds of the anterior surface serve as the origin of the flexor pollicis longus, or Latin thumb.
7. The pronator quadratus is placed into the triangle formed by the medial side of the lower end and the lower portion of the anterior surface. The radial artery is palpated for the "radial pulse" since it is located on the pronator quadratus, lateral to the tendon of the flexor carpiradialis and medial to the acute anterior edge of the radius.
8. The posterior surface gives rise to the extensor pollicis brevis and abductor pollicis longus.
9. The medial aspect of the neck is where the quadrate ligament is attached.
10. On the medial side, immediately below the radial tuberosity, the oblique cord is attached.
11. The front and posterior edges of the inferior articular surface are where the wrist joint's articular capsule is joined.
12. The lower edge of the ulnar notch is where the articular disc of the inferior radioulnar joint is joined.
13. The lower portion of the acute anterior border is where the extensor retinaculum is attached.
14. The bottom three-fourths of the interosseous border are where the interosseous membrane is attached.
15. The abductor pollicis longus and extensor pollicis brevis have passage through the first groove between the styloid process and the pointed, crest-like lowest portion of the anterior border.
16. The extensor carpi radialis longus and extensor carpi radialis brevis tendons are located in the second groove that forms between the styloid process and the dorsal tubercle.
17. The extensor pollicis longus tendon passes via the third oblique groove, which is located medial to the dorsal tubercle.
18. The tendons of the extensor digitorum, extensor indicis, posterior interosseous nerve, and anterior interosseous artery travel through the fourth groove on the medial surface.
19. Moreover, the tendon extensor digiti minimi can pass through the fifth groove at the point where the ulna and lower ends of the radius converge.
20. Last but not least, the tendon of the extensor carpi ulnaris traverses the sixth groove, which is located between the ulna's head and styloid process. compartments/grooves under the extensor.
21. There are six retinaculum of the wrist: four relate to the radius, five are at the radius-ulna intersection, and the sixth is on the ulna itself, between the styloid process and head.

OSSIFICATION

During the eighth week of development, a major center emerges, from which the radius shaft ossifies. The growing end of the bone is the lower end, which ossifies from a secondary center that occurs during the first year and fuses with the shaft at the twentieth year. The upper end, or head, ossifies from a secondary center that appears during the fourth year and fuses with the shaft at the eighteenth year.

MEDICAL ANATOMY

Commonly, a radius fracture (Colles' fracture) occurs approximately 2 centimeters above its lower end. An outstretched hand fracture is the result of a fall. The radial styloid process moves proximally to the ulnar styloid process as the distal fragment is pushed both upward and backward. In most cases, it is located distal to the ulnar styloid process. This type of fracture is known as Smith's fracture if the distal fragment shifts anteriorly. A child's hand may suddenly and violently jerk, releasing the radius head from the annular ligament's hold. Subluxation of the head of the radius (pulled elbow) is the term for this. Usually, the head is felt in a hollow behind the humerus' lateral epicondyle.