Topic Overview

Radius

General Features

• Lateral bone of the forearm (in anatomical position).

• Shorter than ulna.

• Bone of mobility – takes part in wrist joint.

• Lies parallel to ulna, connected by interosseous membrane.

Parts of Radius

1. Upper End

   • Head → disc-shaped, articulates with capitulum of humerus (superior surface) and radial notch of ulna (circumference).

   • Neck → constricted below head.

   • Radial tuberosity → on medial side, insertion of biceps brachii.

2. Shaft

   • Has three borders (anterior, posterior, interosseous) and three surfaces (anterior, posterior, lateral).

   • Anterior surface → flexor pollicis longus, pronator quadratus.

   • Posterior surface → abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus.

   • Lateral surface → pronator teres insertion.

3. Lower End

   • Broad and quadrilateral.

   • Carpal articular surface → for scaphoid and lunate.

   • Ulnar notch → articulates with head of ulna (distal radioulnar joint).

   • Styloid process → lateral projection, palpable.

   • Dorsal tubercle (Lister’s tubercle) → pulley for tendon of extensor pollicis longus.

Ossification of Radius

• Primary center: shaft, appears in 8th week intrauterine life.

• Secondary centers:

  • Lower end → appears at 2 years, fuses at 20 years.

  • Upper end (head) → appears at 5 years, fuses at 17 years.

• Total centers: 1 primary + 2 secondary = 3 centers.

Clinical Anatomy

• Fractures of Radius

  • Colles’ fracture → fracture at lower end (about 2 cm above wrist joint), common in elderly → “dinner fork deformity”.

  • Smith’s fracture → reverse of Colles’, distal fragment displaced anteriorly.

  • Fracture of neck of radius → common in children.

  • Isolated radial shaft fractures rare; usually associated with ulna fractures.

• Dislocations

  • Head of radius may dislocate in children (pulled elbow/nursemaid’s elbow).

• Clinical landmarks

  • Radial styloid process more distal than ulnar styloid process → important in wrist alignment.

  • Radial artery palpable at distal end (lateral to flexor carpi radialis tendon).

• Ossification centers useful for age determination in forensic practice.