The radial styloid is a tapered projection from the lateral surface of the distal radius, extending about 1 cm further distally than the articular surface of the ulnar head (normal radial length about 11-12 mm). The brachioradialis tendon inserts at its base, and the first extensor compartment (APL and EPB) passes over a groove at its lateral aspect. The radial collateral ligament of the wrist originates from the styloid tip. It forms the proximal end of the anatomical snuffbox.
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| Ossification | Part of the distal radial epiphysis, whose secondary centre appears at about 1 year and extends into the styloid; it fuses with the shaft at about 17-19 years. |
The radial styloid is involved in three important fracture patterns: it may fracture as an isolated process (chauffeur fracture or Hutchinson fracture), as part of a comminuted distal radius fracture, or as an avulsion. A radial styloid fracture extending into the scaphoid fossa signals potential radiocarpal instability and is often associated with scapholunate ligament injury. Radial length, measured from the styloid tip to the ulnar head articular surface on a PA radiograph, is used to judge shortening after distal radius fractures. Radial styloidectomy relieves impingement between the styloid and the scaphoid, for example in early SLAC wrist arthritis. De Quervain tenosynovitis affects the first compartment tendons as they pass over the styloid process.
Follow the outer (thumb) side of the radius down to the wrist. The bony point at the end, just above the base of the thumb and at the top of the anatomical snuffbox, is the radial styloid. It reaches about 1 cm further toward the hand than the ulnar styloid.
Intra-articular radial styloid fracture from direct impaction of the scaphoid against the styloid in a fall on an outstretched hand, producing lateral wrist pain and requiring fixation when displaced, as the fracture line extends into the scaphoid fossa of the radiocarpal joint.
Tenosynovitis of the first extensor compartment as APL and EPB tendons cross the radial styloid produces lateral wrist and styloid pain with a positive Finkelstein test, managed with immobilisation, injection, and surgical release of the first compartment roof when conservative measures fail.
