Distal radius
Extremitas distalis radii
- Synonyms: Distal extremity of radius, Lower extremity of radius
Definition
The distal radius (Distal extremity of radius) is the broadened lower (distal) end of the radius where the bone widens from its shaft and articulates with the carpus and the ulna. It is not and official term in Terminologia Anatomica and in clinical/fracture terminology it is commonly defined as the region within approximately 3 cm of the radiocarpal joint.
Key anatomic features:
Articular surfaces (three facets): the scaphoid fossa and lunate fossa, which together form the platform on which the carpus rests (separated by a dorsal–volar ridge), and the sigmoid notch medially, which articulates with the head of the ulna at the distal radioulnar joint.
Radial styloid: the lateral projection that extends distally, forming the most distal bony landmark on the radial side.
Surface contours: a convex dorsal lip that acts as a fulcrum for the extensor tendons, and a concave volar (anterior) surface over which the median nerve and finger flexor tendons pass.
Column concept: for fracture management it is often conceptualized in three columns—radial, intermediate, and ulnar—supported by the shaft.
Normal radiographic parameters used to define the intact distal radius include radial inclination (~21–25°), volar tilt (~2–20°, mean ~11°), and radial length (~10–13 mm, with the radius normally ~11 mm longer than the ulna).
