Anatomy of forearm power point prese.pptx

Anatomy of the forearm

1. FOREARM (Posterior Compartment) TAMALE NICHOLAS Mmed Surg

2. Bones of the forearm

3. Compartments of the forearm 2-3 (Depends on reference) ie Anterior & Posterior +/- proximolateral (mobile wad) Formed by deep fascial sheath, Interosseous membrane & fibrous intermuscular septa. Flexors and pronators (anterior compartment) Extensors and supinators (posterior compartment)

4. Interosseous membrane Broad thin collagenous structure between the shafts radius and ulna. (syndesmosis) Acts in conjuction with the radial head to restrain the radius from proximal migration and stabilize the fore arm Provides attachment to related muscles Apertures for conduction of anterior and posterior interosseous vessels

5. Forearm compartments and interosseous membrane

6. Muscles of the posterior & proximolateral compartment 12 muscles divided into a superficial and deep layer

7. Superficial layer Muscle Proximal attachment Distal attachment Innervation Main action Brachioradialis Proximal 2/3 of supra-epicondylar ridge of humerus Lateral surface of distal end of radius proximal to styloid process Radial nerve (C5, C6, C7) Relatively weak flexion of forearm; maximal when forearm is mid pronated Extensor carpi radialis longus (ECRL) Lateral supra-epicondylar ridge of humerus Dorsal aspect of base of 2nd metacarpal Radial nerve (C6, C7) Extend & abduct hand at the WJ; active during fist clenching Extensor carpi radialis brevis (ECRB) Common extensor origin Dorsal aspect of base of 3rd metacarpal Deep branch of radial nerve ( C7, C8) Extend and abduct hand at the WJ; Active during fist clenching

8. Superficial layer cont.. Muscle Proximal attachment Distal attachment Innervation Main action Extensor digitorum Common extensor origin Extensor expansions of medial 4 digits Deep branch of radial nerve ( C7, C8) Extends medial four digits at MPJ, secondarily at IPJ Extensor digiti minimi (EDM) Common extensor origin Extensor expansion of 5th digit Deep branch of radial nerve ( C7, C8) Extends 5th digit at MPJ, secondarily at IPJ Extensor carpi ulnaris (ECU) Lateral epicondyle of humerus ; posterior border of ulna (shared aponeurosis) Dorsal aspect of base of 5th metacarpal Deep branch of radial nerve ( C7, C8) Extends and adducts hand at WJ (also active during fist clenching)

9. Superficial layer cont.. Muscle Proximal attachment Distal attachment innervation Main action Anconeus Lateral epicondyle Lateral side of olecranon Radial nerve- branch from trunk in radial groove (C7,C8) Small amount of posterolateral movt of ulna during pronation

10. Deep layer Muscle Proximal attachment Distal attachment Innervation Main action Supinator Lateral epicondyle; radial collateral and anular ligs ; supinator & crest of ulna Lateral, posterior, and anterior surfaces of proximal 1/3 of radius Deep branch of radial nerve (C7, C8 ) Supinates forearm; rotates radius to turn palm anteriorly Extensor indicis Posterior surface of distal 1/3 of ulna and interosseous membrane Extensor expansion of 2nd digit Posterior interosseous nerve ( C7, C8), continuation of deep Branch of radial Extends 2nd digit independently; helps extend hand at wrist Abductor pollicis longus (APL) Posterior surface of proximal ulna radius interosseous membrane Base of 1st metacarpal Posterior interosseous nerve ( C7, C8), continuation of deep Branch of radial Abducts thumb and extends it at carpometacarpal joint

11. Deep layer cont muscle Proximal attachment Distal attachment Innervation Main action Extensor pollicis longus (EPL) Posterior surface of middle third of ulna and interosseous membrane Dorsal aspect of base of distal phalanx of thumb Posterior interosseous nerve (C7, C8 ), Extends distal phalanx of thumb at IPJ; extends MP and CM joint Extensor pollicis brevis (EPB) Posterior surface of distal third of radius and interosseous membrane Dorsal aspect of base of proximal phalanx of thumb Posterior interosseous nerve (C7, C8 ) Extends proximal phalanx of thumb At MPJ; extends CM joint

12. Arterial supply of posterior compartment of forearm

13. Arterial supply cont. Main supply Radial recurrent artery Posterior interosseous artery Other sources Anterior interosseous artery Radial collateral branch of profunda brachii

14. Venous drainange Deep veins ( veni comitantes of radial, ulna, anterior an posterior interosseous veins) connected to median cubital vein Superficial veins (cephalic, median vein of the fore arm and basilic vein +/- accessory cephalic vein)

15. Superficial Venous drainage

16. Lymphatic drainange Supratrochlear nodes Nodes along radial, ulnar and interosseous vessels.

17. Extensor retinaculum Band like thickening in the deep fascia of the forearm lying obliquely across extensor surface of the wrist. From anterolateral boarder of radius above styloid process to pisiform and triquetral bones. Fibrous septa run from its deep surface to divide the extensor tunnel into 6 compartments each lined by a separate synovial sheath for passage of long extensor tendons.

18. ER cont

19. Anatomical snuff box Concavity formed between extensor tendons drawn up on the radial side of the wrist If the thumb is fully extended. Tendons include; extensor pollicis longus (ulnar side) and extensor pollicis brevis plus abductor pollicis longus (radial side) Contents include start of cephalic vein in the roof, radial artery on the floor Proxima to distal side floor contents include radial styloid, scaphoid, trapezium & 1 st metacarpal

20. Clinical correlates for discussion regarding the forearm Fractures Fracture of the olecranon Fracture of the head and neck of the radius Fracture of the shafts of the ulna and radius Monteggia’s Fracture Galeazzi’s fracture Colle’s Fracture Smith’s fracture Humeral fractures that affect forearm structures

21. Clinical Correlates cont.. Olecranon bursitis Volkmann’s ischaemic contracture Compartment syndrome of the forearm Cubital tunnel syndrome Carpal tunnel syndrome Pronator syndrome Tennis elbow and lateral epicondylitis Stenosing Synovitis of the Abductor Pollicis longus and Extensor Pollicis Brevis Tendons Rupture of extensor pollicis longus tendon

22. Clinical correlates cont.. Median, ulnar and radial nerve injuries in the fore arm Synovial cyst of the wrist. (common areas of occurrence) Mallet or baseball finger

23. END Thanks for your attention and fruitful discussion