MSK 3c: posterior forearm Flashcards
Superficial and deep muscles or posterior forearm?
Superficial: (from lateral to medial) Brachioradialis Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorum Extensor digiti minimi Extensor carpi ulnaris Anconeus (small at top)
Deep: Supinator Extensor indices Abductor pollicis longus Extensor pollicis longus Extensor pollicis brevis
Method to remember all 12 muscles in posterior forearm?
3 to the wrist: ECRL, ECRB, ECU
3 to the fingers: ED, EDM, EI
3 to the thumb: AbPL, EPL, EPB
3 random: B, S, A
Brachioradialis? (most lateral, rotates into anterior compartment)
O: proximal supraepicondylar ridge of humerus
I: lateral distal end of radius (just prox to radial styloid)
N: radial (C5, C6, C7)
A: flexion at elbow
Fusiform
Testing brachioradialis?
Elbow flexed against resistance with forearm midpronated. If normal the muscle can be seen/palpated
Extensor carpi radialis longus? (active during fist clenching)
O: lateral supraepicondylar ridge of humerus
I: dorsal aspect of base of 2nd metacarpal
N: radial (C6, C7)
A: extends and ABducts hand at wrist
Extensor carpi radialis brevis
O: lat epicondyle of humerus
I: dorsal base of 3rd metacarpal
N: radial posterior interosseous(C7, C8)
A: extend and ABduct hand at wrist
Extensor digitorum
O: lat humeral epicondyle
I:extensor expansion of medial 4 fingers
N: radial posterior interosseous(C7, C8)
A: extends medial 4 digits (mainly @ MCP, some action on IP)
Test extensor digitorum?
Pronated forearm, fingers extended against resistance
Extensor digiti minimi? (fusiform shape)
O: lat humeral epicondyle
I: extensor expansion of 5th digit
N: radial posterior interosseous(C7, C8)
A: extends 5th digit at MCPJ and some action at IPJ
Extensor carpi ulnaris (long and fusiform)
O: lat humeral epicondyle, posterior ulnar border
I: base of 5th metacarpal
N: radial posterior interosseous(C7,C8)
A: extension and ADduction at wrist
Anconeus?
Blended with triceps fibres, sometimes indistinguishable
O: lat epicondyle humerus
I: posterior and lateral part of olecranon
N: radial (C7, C8)
A: moves ulna during pronation and extends at elbow
Supinator?
O: lat epicondyle of humerus and posterior surface of ulna
I: proximal 1/3 radius surfaces
N: radial deep (c7, c8)
A: supinates forearm by rotating radius to turn arm anteriorly or superiorly if elbow is flexed
Floor of cubital fossa, deep branch of radial nerve passes through its two heads
Extensor indices?
O: posterior surface of distal ulna and interosseous membrane
I: extensor hood of 2nd finger
N: radial deep C7,C8
A: extends 2nd digit, helps wrist extension
Abductor pollicis longus?
O: posterior proximal ulna, radius and interosseous membrane
I: base of 1st metacarpal
N: radial-post interosseous C7, C8
A: ABducts thumb and extends it at MCPJ
Extensor pollicis longus?
O: posterior middle of ulna and interosseous membrane
I: dorsal distal phalynx of thumb
N: posterior interosseous c7 c8
A: extends CMC, MCP and IP joints in thumb
