Radius

Radius


Parts of Radius

1. Upper End
  • Head 
  • Neck 
  • Radial tuberosity 

2. Lower end 

3. Shaft 

 

Upper end


Head 
Its shape is disc-like.
In living it is covered with articular hyaline cartilage.
During the full flexion, it articulates superiorly with the capitulum to form a humero-radial joint.
It articulates medially with the radial notch of the ulna.
All the parts are encircled by annular ligament except the articular part.

 

Neck 

→ It is the constricted part.
→ It lies below the head.
→ The quadrate ligament is attached to the side of the neck.

 

Radial tuberosity 

It has two-part

  1. Smooth anterior part 
  2. Rough posterior part 

Smooth anterior part is covered by synovial bursa which separates this part from biceps tendon.

• The rough posterior part gives insertion to the biceps tendon.

 

Shaft

It has three borders 
  1. Anterior border 
  2. Posterior border 
  3. Medial/interosseous border

It has three surfaces 

  1. Anterior surface 
  2. Posterior surface 
  3. Lateral surface 

 

Anterior border
It starts from the anterolateral part of the radial tuberosity.
It runs downward and laterally to the styloid process.
It has two parts, the upper part (Anterior oblique line) and the lower part (Sharp).
Anterior oblique line
Gives origin to the radial head of the flexor digitorum superficialis.

 

Posterior border 
• It is clearly distinguishable in its middle third of the shaft.
The posterior oblique line is formed when it runs upward and medially to the radial tuberosity.

Medial/interosseous border 
It is the sharpest border among three borders.
Above→ it is up to the radial tuberosity 
Below→ it forms the posterior margin of the small triangular area on the medial side of the lower end of the bone.

Three-fourth parts of this border gives attachment to the interosseous membrane.

 

Anterior surface 
This is the area between the anterior and interosseous border.
Nutrient foramen present in this surface which lies just above the middle part of the surface.
The direction of the nutrient canal is upward from where the nutrient artery passes which is a branch of the anterior interosseous artery.
Upper two-fourth
Gives origin to the Flexor pollicis longus 
Lower one-fourth
Gives insertion to the Pronator Quardatus.


Posterior surface 
It is the area between the interosseous and posterior border.
Middle one-third
Gives origin of the abductor pollicis longus
Lower part of this surface
Give origin of the Extensor pollicis brevis


Lateral surface
It is the area between the anterior and posterior border.
Upper one-third Give insertion to the supinator 
Middle of the surface on the rough area
Gives insertion to the pronator trees.

 

Lower end

Its has five surfaces 
  1. Anterior surface 
  2. Posterior surface 
  3. Medial surface 
  4. Lateral surface 
  5. Inferior surface 
¶ Anterior surface
• A thick ridge is present on this surface provides attachment to the palmar radio-carpel ligament of the wrist joint. 
¶ Posterior surface
• Here lister’s tubercle and dorsal tubercle of the lister present. 
Dorsal tubercle of the lister
• Lateral to this tubercle, a grove is present.
• That is the groove for the extensor pollicis longus and other extensor tendons.
Lister’s tubercle 
• Lateral to this tubercle a grove is present which is transversed by the tendons of extensor carpi radialis longus and extensor carpi radialis brevis.
• Medial to this grove extensor pollicis longus passes which is a common tendon of extensor digitorum and extensor indicis.
¶ Medial surface 
• A notch called ulna notch is present on this surface.
• It gives articulation to the head of the ulna and forms the radioulnar joint.
• Articular disc of the inferior radio-ulnar joint is attached to the lower margin of the ulnar notch.

Note:
Articular Disc
• Fibrocartilagenous Structure
• Due to its presence, Ulnar doesn't take part in the formation of wrist joint
• Wrist Joint is also called Radio-carpal Joint
¶ Lateral surface 
• It is projected downward as the styloid process.
• It is related to the tendons of the abductor pollicis longus and extensor pollicis brevis.
• The base of the styloid process gives insertion to the brachioradialis.
• Tip of styloid gives attachment to the radial collateral ligament of the wrist joint.
¶ Inferior surface 
   It has two parts 
Lateral triangular area
• Articulate with the scaphoid bone

Medial quadrangular area
• Articulate with lateral part of lunate bone