Overview
The radius is, with the ulna, one of the two bones of the forearm and the one that transmits the weight of the humerus to the carpus. In cattle it is short, broad and flattened dorsopalmarly, with a slight dorsal curve. The ulna runs along its caudolateral surface and, in the adult, fuses with it over much of its length; for this reason the bovine forearm cannot pronate or supinate, and its movement is limited to flexion and extension of the elbow and carpus.
Proximal end
- Head of the radius (caput radii): broad, with an articular surface (fovea capitis radii) that takes up almost the whole width of the elbow and articulates with the humeral condyle.
- Radial tuberosity (tuberositas radii): on the medial surface, distal to the head; insertion of the biceps brachii.
- Proximal interosseous space (spatium interosseum antebrachii proximale): an elongated slit between the radius and ulna, distal to the elbow, through which vessels reach the dorsal surface of the forearm.
Shaft and distal end
- Shaft: convex and smooth on its dorsal surface, which is covered by the extensors of the carpus and digits; the ulna lies against its caudolateral surface.
- Distal interosseous space: a small opening between the two bones near the distal end.
- Trochlea of the radius (trochlea radii): the oblique distal articular surface for the radial and intermediate carpal bones.
- Medial styloid process (processus styloideus medialis): palpable on the medial side of the carpus. The lateral styloid process belongs to the ulna.
Clinical relevance
- Radius and ulna fractures: less common than metacarpal and metatarsal fractures; because the two bones are fused they usually involve both. Being so high on the limb, a cast that stops at the elbow does not immobilise them well; they are treated with a Thomas splint combined with a cast, or with internal or external fixation.
- Physeal fractures of the distal radius in calves.
- Haematogenous osteomyelitis: in calves with septicaemia or navel infection it settles in the physes and metaphyses of long bones, the distal radius among them.