Lecture on Forearm Anatomy and Function
Functions of the Forearm
- Fine-tunes hand position for manipulation of objects.
- Essential for various occupations.
- One degree of freedom: Pronation and Supination.
- Involves two joints, typically seen as one: proximal and distal radioulnar joints.
Proximal Radioulnar Joint
- Radial head moves around the radial notch.
- Anular ligament secures the radial head, allowing it to spin without much movement.
Distal Radioulnar Joint
- Contains the interosseous membrane between radius and ulna, providing stability.
- Ulna head articulates with the ulnar notch, stabilized by multiple ligaments.
- Key ligament: Triangular Fibrocartilage Complex (TFCC).
Forearm Movement
- Axis of motion: virtual line from radial head to ulnar head.
- Radial bone moves around the ulna, ulna has minimal movement (<3 degrees).
- Normal range of pronation/supination: 0 to 80 degrees.
- Functional range: 0 to 50 degrees.
Muscles Involved in Pronation and Supination
Pronation
- Primary Movers: Pronator Quadratus and Pronator Teres
- Quadratus is stronger, active in most pronation tasks.
- Teres assists in fast pronation and against resistance.
Supination
- Primary Movers: Biceps Brachii and Supinator
- Biceps Brachii most effective at 90° elbow flexion.
- Supinator most effective with elbow in extension.
Summary of Muscle Actions
- Elbow Flexion: Biceps Brachii, Brachialis, Brachioradialis
- Elbow Extension: Triceps Brachii, Anconeus
- Forearm Pronation: Pronator Quadratus, Pronator Teres
- Forearm Supination: Biceps Brachii, Supinator
Common Elbow and Forearm Pathologies
- Lateral Epicondylitis (Tennis Elbow): Overuse of wrist/hand extensors.
- Medial Epicondylitis (Golfer's Elbow): Overuse of wrist/finger flexors.
- Pulled Elbow (Nursemaid's Elbow): Common in children, caused by traction or tear of anular ligament.
- Dislocation: Rare, usually due to falls or accidents.
- Cubital Tunnel Syndrome: Compression of ulnar nerve at the elbow, second most common nerve compression after carpal tunnel syndrome.
Note: Detailed discussion on wrist complex and related ligaments to follow in subsequent lectures.