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Forearm muscles
- 2. Compartments • Forearm is divided into • Anterior and posterior compartments by • Lateral intermuscular septum • Aninterosseousmembrane • Attachment of deepfasciaalongtheposterior border of the ulna
- 3. Anterior (flexor) compartment of forearm • Muscles are in threelayers • Superficial • Intermediate • Deep • Thesemusclesassociatedwith • Movements of wristjoint • Flexionof fingers • Pronation • All muscles in anterior compartment of forearm • Innervated by median nerve • Except for Flexor carpi ulnaris muscle and medial half of Flexor digitorum profundus muscle • Innervated byulnarnerve
- 4. Anterior compartment of forearm • Superficial group • Five muscles cross the elbow joint • Three musclesdonot • Flexor compartment is much more bulky • Than extensor compartment • Necessary power of grip
- 5. Pronator Teres • Origin • Humeral head • Medial epicondyle of humerus • Ulnar head • Medial border of coronoid process of ulna • Action • Lateral aspect of shaft of radius • Nerve supply • Median nerve • Action • Pronation and flexion of forearm
- 6. Flexor carpi radialis • Origin • Medial epicondyle of humerus • Insertion • Bases of second and third metacarpal bones • Nerve supply • Median nerve • Action • Flexes and abducts hand at wrist joint
- 7. Palmaris longus • Origin • Medial epicondyle of humerus • Insertion • Flexor retinaculum and palmar aponeurosis • Nerve supply • Median nerve • Action • Flexes hand
- 8. Flexor Carpi Ulnaris • Origin • Humeral head • Medial epicondyle of humerus • Ulnar head • Medial aspect of olecranon process and posterior border of ulna • Insertion • Pisiform bone, hook of the hamate, base at fifth metacarpal bone • Nerve supply • Ulnar nerve • Action • Flexes and adducts hand at wrist joint
- 9. Flexor Digitorum Superficialis • Origin • Humeroulnar head • Medial epicondyle of humerus; medial border of coronoid process of ulna • Radial head • Oblique line on anterior surface of shaft of radius • Insertion • Middle phalanx of medial four fingers • Nerve supply • Median nerve • Action • Flexes middle phalanx of fingers and assists in flexing proximal phalanx and hand
- 10. Deep group • 3 muscles • Flexor digitorum profundus • Flexor pollicis longus • Pronator quadratus
- 11. Flexor digitorum profundus • Origin • Anteromedial surface of shaft of ulna • Insertion • Distal phalanges of medial four fingers • Action • Flexes distal phalanx of fingers; then assists in flexion of middle and proximal phalanges and wrist • Nerve supply • Ulnar (medial half) and median (lateral half) nerves
- 12. Flexor pollicis longus • Origin • Anterior surface of shaft of radius • Insertion • Distal phalanx of thumb • Action • Flexes distal phalanx of thumb • Nerve supply • Anterior interosseous branch of median nerve
- 13. Pronator quadratus • Origin • Anterior surface of shaft of ulna • Insertion • Anterior surface of shaft of radius • Action • Pronates forearm • Nerve Supply • Anterior interosseous • Branch of median nerve
- 14. Space of Parona • Space in front of pronator quadratus • Deep to long flexor tendons of fingers and their synovial sheaths • Limited proximally by • Oblique origin of flexor digitorum superficialis • Space involved in proximal extensions of synovial sheath infections • Can be drained through radial and ulnar incisions to the side of the flexor tendons
- 15. Posterior compartment of forearm • Muscles are arranged in 2 layers • Superficial • Deep • Muscles are associated with • Movement of the wristjoint • Extension of the fingers and thumb • Supination • All the muscles of posterior compartment are supplied by • Radial nerve
- 16. Arrangement of posterior compartment muscles • Upper part • Anconeus (superficial) • Supinator (deep) • Lateral part of humerus • Pass along the radial side • Brachioradialis • Extensors carpi radialis longus • Extensors carpi radialis brevis • Passing along posterior surface of the forearm • Extensor digitorum • Extensor digiti minimi and • Extensor carpi ulnaris • At lower end of forearm • These two groups are separated by three muscles • They emerge from deeply in between them and go to the thumb • Abductor pollicis longus • Extensors pollicis longus and • Extensors pollicis longus brevis • One muscle for the forefinger runs deeply to reach the back of the hand • Extensor indicis
- 17. Superficial muscles of the back of forearm • There are 7 muscles • Common extensor origin • Four of the superficialmuscles • Arisefromthetipoflateralepicondyleof thehumerus • Extensor carpi radialis brevis • Extensor digitorum • Extensor digiti minimi, and • Extensor carpi ulnaris • All seven muscles cross elbow joint
- 18. Superficial muscles of back of forearm • Categorized into two groups • Lateral and posterior • Each group consists of three muscles • Lateral group • Brachioradialis • Extensor carpi radialis longus • Extensor carpi radialis brevis • Posterior group • Extensor digitorum • Extensor digiti minimi • Extensor carpi ulnaris • In the upper end • Anconeus
- 19. Brachioradialis • Origin • Upper 2/3rd of lateral supracondylar ridge of humerus • Insertion • Into base of styloid process of radius • Nerve Supply • Radial nerve • Action • Flexion of the forearm (specially in midprone position)
- 20. Extensor carpi radialis longus • Origin • From the lower 1/3rd of the lateral supracondylar ridge of the humerus • Insertion • Into the posterior surface of the base of the 2nd metacarpal bone • Nerve Supply • Radial nerve • Action • Extension of the hand at wrist joint Abduction of the hand at wrist joint
- 21. Extensor carpi radialis brevis • Origin • Lateral epicondyle of humerus (common extensor origin) • Insertion: • Posterior surface of base of 3rd metacarpal bone • Nerve Supply • Posterior interosseous nerve • Action • Extension & abduction of the hand at wrist joint
- 22. Extensor digitorum • Origin • Lateral epicondyle of humerus (common extensor origin) • Insertion • Extensor expansion of the medial 4 fingers • Nerve Supply • Posterior interosseous nerve • Action • Extension of metacarpophalangeal and interphalangeal joints of the medial 4 fingers • Extension of the hand at wrist joint
- 23. Extensor digiti minimi • Origin • Lateral epicondyle of the humerus (common extensor origin) • Insertion • Extensor expansion of the little finger • Nerve Supply • Posterior interosseous nerve • Action • Extension of metacarpophalangeal and interphalangeal joints of the little finger
- 24. Extensor carpi ulnaris • Origin • Lateral epicondyle of the humerus (common extensor origin) • Insertion • Posterior surface of the base of the 5 th metacarpal bone • Nerve Supply • Posterior interosseous nerve • Action • Extension & Adduction of the hand at wrist joint
- 25. Anconeus • Origin • Posterior aspect of the lateral epicondyle of the humerus • Insertion • Lateral surface of olecranon process of ulna • Nerve Supply • Posterior interosseous nerve • Action • Helps the triceps in extension of the elbow joint
- 26. Deep Layer • There are five deep muscles • Three deepextensorsof the forearm • Function on thumb • Abductor pollicis longus(APL) • Extensor pollicis brevis (EPB) • Extensor pollicis longus (EPL) • To acquire insertion on the three bones of thumb ‘crop out’ • From furrow in lateralelementof forearmbetweenlateral andposterior groupsof superficial extensor • One muscle • Function onindex finger • Extensor indicis • In the upper part • Supinator
- 27. Supinator • Origin • Lateral epicondyle of the humerus • Annular ligament of the superior radio-ulnar joint • Supinator fossa and crest of the ulna • Insertion • Upper 1/3rd of the lateral surface of shaft of radius • Nerve Supply • Posterior interosseous nerve • Action • Supination of the forearm • At radio-ulnar joint
- 28. Abductor pollicis longus • Origin • Middle of the posterior surface of radius and ulna • Interosseus membrane • Insertion • Posterior surface of the base of the 1st metacarpal bone • Nerve Supply • Posterior interosseous nerve • Action • Abduction and extension of the thumb at the carpo-metacarpal joint
- 29. Extensor pollicis brevis • Origin • Posterior surface of the shaft of radius • Insertion • Posterior surface of the base of the proximal phalanx of the thumb • Nerve Supply • Posterior interosseous nerve • Action • Extension of the metacarpophalangeal joint of the thumb
- 30. Extensor pollicis longus • Origin • Posterior surface of ulna • Insertion • Posterior surface of the base of the distal phalanx of the thumb • Nerve Supply • Posterior interosseous nerve • Action • Extension of the interphalangeal joints of the thumb
- 31. Extensor indicis • Origin • Posterior surface of ulna (below extensor pollicis longus) • Insertion • Extensor expansion of the index finger. • Nerve Supply • Posterior interosseous nerve • Action • Extension of the interphalangeal joints of the thumb
- 32. Wrist Drop • Sign of radial nerve injury • There are two common characteristic sites of damage • Axilla • Injured viahumeral dislocationsor fractures of the proximal humerus • Radial groove of the humerus • Injured via a humeral shaft fracture • Radial nerve innervates • All muscles in extensor compartment of forearm • In radial nerve lesion • These muscles are paralysed • Muscles that flex the wrist • Innervated by median nerve • Flexor muscles produces unopposed flexion at the wrist joint – wrist drop