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M01.03.015 Radius
The radius is one of the two long bones of the forearm, lying laterally and parallel to the ulna. It plays a key role in forearm movement, pivoting around the ulna to facilitate motion at the proximal and distal radio-ulnar joints.
Key Articulations of the Radius
The radius forms articulations at four distinct locations:
| Joint | Articulating Structures |
|---|---|
| Elbow Joint | Head of the radius and capitulum of the humerus. |
| Proximal Radioulnar Joint | Radial head and the radial notch of the ulna. |
| Wrist Joint | Distal radius and carpal bones (scaphoid and lunate). |
| Distal Radioulnar Joint | Ulnar notch of the radius and the head of the ulna. |
Anatomy of the Radius
1. Proximal End
Key bony landmarks:
- Head: Disc-shaped structure with a concave articulating surface; medially thickened for the proximal radioulnar joint.
- Neck: Narrow section between the head and radial tuberosity.
- Radial Tuberosity: Bony projection serving as the attachment site for the biceps brachii muscle.
2. Shaft
- Triangular in cross-section with three borders and three surfaces.
- A small roughened area on the lateral surface serves as the attachment site for the pronator teres muscle.
- Expands in diameter as it moves distally.
3. Distal End
- Styloid Process: Lateral projection of the distal radius.
- Ulnar Notch: Medial concavity articulating with the ulna’s head, forming the distal radioulnar joint.
- Articular Facets: Two surfaces on the distal radius articulate with the scaphoid and lunate bones to form the wrist joint.
Clinical Relevance
Common Fractures of the Radius
| Fracture Type | Mechanism | Key Features |
|---|---|---|
| Colles’ Fracture | Fall onto an outstretched hand. | Distal radius fractures with posterior displacement; results in a ‘dinner fork deformity’. |
| Smith’s Fracture | Fall onto the back of the hand. | Distal radius fractures with anterior displacement. |
| Radial Head Fracture | Fall onto an outstretched hand with force directed into the capitulum. | Commonly involves the elbow joint. |
Combined Radius and Ulna Fractures
| Fracture Name | Mechanism | Features |
|---|---|---|
| Monteggia | Force impacting the posterior ulna. | Proximal ulna fracture with anterior dislocation of the radial head. |
| Galeazzi | Trauma to the distal radius. | Distal radius fracture with dislocation of the ulna head at the distal radioulnar joint. |
Points to Remember:
- The radius and ulna are connected by the interosseous membrane, which transmits forces between them.
- Trauma to one bone can often lead to associated injuries to the other.
- Proper diagnosis and management of radial fractures are crucial to prevent long-term functional deficits.