Lower extremity of radius
The radius and ulna of the left forearm, posterior surface. The top is proximal (elbow) and bottom is distal (wrist).
|Latin||Extremitas distalis radii|
|Anatomical terms of bone|
The distal end of the radius is large and of quadrilateral form.
- The carpal articular surface is triangular, concave, smooth, and divided by a slight antero-posterior ridge into two parts. Of these, the lateral, triangular, articulates with the scaphoid bone; the medial, quadrilateral, with the lunate bone.
- The articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is narrow, concave, smooth, and articulates with the head of the ulna.
These two articular surfaces are separated by a prominent ridge, to which the base of the triangular articular disk is attached; this disk separates the wrist-joint from the distal radioulnar articulation.
This end of the bone has three non-articular surfaces - volar, dorsal, and lateral.
- The volar surface, rough and irregular, affords attachment to the volar radiocarpal ligament.
- The dorsal surface is convex, affords attachment to the dorsal radiocarpal ligament, and is marked by three grooves. Enumerated from the lateral side:
- The first groove is broad, but shallow, and subdivided into two by a slight ridge; the lateral of these two transmits the tendon of the extensor carpi radialis longus muscle, the medial the tendon of the extensor carpi radialis brevis muscle.
- The second is deep but narrow, and bounded laterally by a sharply defined ridge; it is directed obliquely from above downward and lateralward, and transmits the tendon of the extensor pollicis longus muscle.
- The third is broad, for the passage of the tendons of the Extensor indicis proprius and Extensor digitorum communis.
- The lateral surface is prolonged obliquely downward into a strong, conical projection, the styloid process, which gives attachment by its base to the tendon of the brachioradialis, and by its apex to the radial collateral ligament of the wrist joint. The lateral surface of this process is marked by a flat groove, for the tendons of the abductor pollicis longus muscle and extensor pollicis brevis muscle.
X-Ray of a closed fracture of the distal radius with 10° of lateral angulation, subject is the left arm of 11-year-old male