Anatomy and Attachment of the Radius Bone, Lecture notes of Medicine

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Radius

ANATOMY AND ATTACHMENT AND APPLIED

Introduction

 The radius (plural: radii ) is one of the two long bones

present in the forearm, located laterally in the

supinated anatomical position.

 The radius is shorter than the ulna and has a

small proximal end that articulates with the

humerus, and a broad distal end that articulates with

the carpal bone at the wrist.

Articulations of radius  (^) Proximal end -  (^) Radial head: capitellum of the humerus (elbow flexion and extension)  (^) Radial head: radial notch of the proximal ulna (site of supination and pronation)  (^) Distal end -  (^) Distal radius facet: scaphoid and lunate fossae separated by a small ridge  (^) Ulnar notch: ulna head (site of supination and pronation)

Proximal Region of the Radius

 The proximal end of the radius articulates in

both the elbow and proximal radioulnar joints.

 Important bony landmarks include -

 Head , neck and radial tuberosity

 (^) Head of radius ( upper end ) – A disk shaped structure, with a concave articulating surface covered with hyaline cartilage.

1. It has a superior concave surface which articulates with the capitulum of the humerus at the elbow joint.  (^) Neck - A narrow area of bone, which lies between the radial head and radial tuberosity.  (^) Radial tuberosity – A bony projection, which serves as the place of attachment of the biceps brachii muscle.

Shaft – Borders of radius  (^) Anterior border - lies on the medial aspect of the bone. It starts just distal to the radial tuberosity and crosses diagonally to the lateral aspect of the shaft.  (^) Posterior border - The posterior border lies on the posterior aspect of the radius  (^) Medial or Interosseous border - The sharp interosseous border faces the ulna medially. It extends from the radial tuberosity above to the posterior margin of the ulnar notch below.

Surfaces of the radius Radius has three surfaces  (^) Anterior surface - anterior surface lies between anterior and interosseous borders.  (^) Posterior surface - posterior surface lies between posterior and interosseous borders.  (^) Lateral surface - It is lies between anterior and posterior borders.

Lower end of radius  (^) Medial surface - The medial surface of the lower end of the radius bone provides the ulnar notch for articulation with the head of ulna.  (^) Lateral surface - The lateral surface of the lower end of the radius bone projects downward to form styloid process. The brachioradialis is inserted to the base of styloid process.  (^) Inferior surface - This surface takes part in forming wrist joint. Inferior surface bears a triangular area for the scaphoid bone, and a medial quadrangular area for the lunate bone.

Attachment s  (^) Biceps brachii - The biceps brachii is inserted into the rough posterior part of the radial tuberosity.  (^) Supinator - The supinator muscle is inserted into the upper part of the lateral surface.  (^) Pronator teres - The pronator teres is inserted into the middle of the lateral surface.  (^) Brachioradialis - The brachioradialis is inserted into the lower part of the lateral surface just above the styloid process.  (^) Flexor digitorum superficialis - The radial head of flexor digitorum superficialis takes origin from the anterior oblique line and the upper part of anterior border.

Attachments - Ligament  (^) Oblique cord is attached on the medial side just below the radial tuberosity.  (^) The articular capsule of the wrist joint is attached to the anterior and posterior margins of the inferior articular surface.  (^) The articular disc of the inferior radioulnar joint is attached to the lower border of the ulnar notch.  (^) The quadrate ligament is attached to the medial part of the neck.  (^) The extensor retinaculum is attached to the lower part of the sharp anterior border.  (^) The interosseous membrane is attached to the lower three-fourth of the interosseous border.

Attachments - Groove

 First groove - lowest part of anterior border and styloid process

gives passage to abductor pollicis longus and extensor pollicis

brevis.

 Second groove - gives passage to extensor carpi

radialis longus and extensor carpi radialis brevis tendon.

 Third groove - provide passage to extensor pollicis longus tendon.

 Fourth groove - gives passage to tendons of extensor digitorum,

extensor indicis, posterior interoseous nerve and

anterior interosseous artery.

Clinical Anatomy  (^) Colle's fracture -  (^) A Colles' wrist fracture is a distal radius fracture, also known as a dinner- fork deformity of the wrist.  (^) Colles fractures are very common extra- articular fractures of the distal radius that occur as the result of a fall onto an outstretched hand.  (^) The distal fragment is displaced upward and backward, and the radial styloid process comes to lie proximal to the ulnar styloid process.

Clinical Anatomy  (^) Smith's Fracture is a fracture of the distal end of the radius caused by a fall on the back of the hand (flexed), resulting in a volar displacement of the fractured fragment.  (^) It is also known as a reverse Colles fracture.