Posterior forearm - lectures

Question 1

gash on lateral forearm, cut through brachioradialis muscle;
coin-shaped area of numbness near base of 1st & 2nd metacarpal region
which nerve damaged?

Answer 1

superficial branch of radial n.

Question 2

superficial layer of posterior forearm (radialis group)

Answer 2

• bracioradialis
• extensor carpi radialis longus
• extensor carpi radialis brevis

Question 3

superficial layer of posterior forearm (non-radialis group)

Answer 3

• extensor carpi ulnaris
• extensor digiti minimi
• extensor digitorum

Question 4

deep layer of posterior forearm

Answer 4

• supinator
• extensor pollicis longus
• abductor policis longus
• extensor pollicis brevis
• extensor indicis

Question 5

ALL muscles of the posterior forearm are innervated by

Answer 5

• radial nerve (deep branch)

- posterior interosseous n.

Question 6

most superficial extensors attach to the

Answer 6

lateral epicondyle of humerus

but not brachioradialis!

Question 7

superficial radial nerve supplies

Answer 7

sensation to lateral half of distal wrist, hand, and thumb

Question 8

muscles supplied by radial n. before it branches to dep radial n.

Answer 8

brachioradialis

extensor carpi radialis longus

Question 9

muscles supllied by deep radial n.

Answer 9

extensor carpi radialis brevis

supinator

Question 10

responsible for somatosensory innervation to posterior forearm

Answer 10

posterior cutaneous nerve (from radial nerve)

Question 11

brachioradialis ABI

Answer 11

A: flexes forearm when pronated (about midprone position)
B: radial collateral, recurrent radial and radial arteries
I: radial nerve (C5, 6, 7)

Question 12

extensor carpi radialis longus ABI

Answer 12

A: extend and abduct hand at wrist
B: radial collateral a., radial recurrent a., recurrent interosseous a., posterior interosseous a.
[ 2 radial and 2 interosseous]
I: radial nerve (C6, 7)

Question 13

extensor carpi radialis brevis ABI

Answer 13

A: extend and abduct hand at wrist
B: radial collateral, radial recurrent, recurrent interosseous and psoterior interosseous a.
I: deep branch of radial n. (C7, C8)

Question 14

extensor digitorum ABI

Answer 14

A: extends medial 4 fingers at MP joints and somewhat at interphalangeal joints
B: posterio rinterosseous a., recurrent interosseous and perforating branch of anterior interosseous a.
I: posterior interosseous n. (C7, C8)

Question 15

extensor digiti minimi ABI

Answer 15

A: extends 5th finger at MP joint and secondarily a tIP joint
B: posterio rinterosseous, recurrent interosseous and perforating branch of anterior interosseous a.
(same B & I as digitorum)
I: posterior interosseous nerve (C7, C8)

Question 16

extensor digitorum and lumbricals pull on this structure to cause IP joints to extend

Answer 16

extensor hood

Question 17

extensor carpi ulnaris ABI

Answer 17

A: extends and adducts hand at wrist
B: radial collateral, radial recurrent, recurrent interosseous and posterior interosseous a.
I: posterior interosseous n. (C7,C8)

Question 18

35 y/o male fractures arm at midshaft and damages his radial nerv.e has diminished ability to supinate his forearm
why is supination only diminished, but not entirely impossible?

Answer 18

musculocutaneous n. innervating biceps brachii!!

- powerful supinator of the forearm, attachign to radial tuberosity

Question 19

the “outcropping” muscles deep extensors to thumb

APL, EPL, EPB are all innervated by?

Answer 19

deep branch of radial nerve or posterior interosseous n. (continuation of same nerve)

Question 20

supinator ABI

Answer 20

A - supinates forearm, bringing radius back to anatomical position
B- radial artery, posterior interosseous, radial recurrent, recurrent interosseous, and middle collateral arteries
I - deep branch of radial n.

Question 21

extensor indicis ABI

Answer 21

A - independent extension of 2nd finger, also helps w/ extension of wrist
B - posteiror interosseous and perforating branch of anterior interosseous arteries
I - posterior interosseous nerve

Question 22

abductor pollicis longus ABI

Answer 22

A - abducts thumb and extends it at carpometacarpal joint
B - posterior interosseous a.
I - posterior interossoeus n.

Question 23

extensor pollicis brevis ABI

Answer 23

A - extends proximal phalans of thumb at its MCP joint, also extends carpometacarpal joint
B - posterior interosseous and perforating branch of anterior interossoeus a.
I - posterior interosseous n.

Question 24

extensor pollicis longus ABI

Answer 24

A - extends distal phalanx of thumb at its IP joint and extends MCP and CMC joint
B - posteiror interossoeus and perforating branch of anterior interosseous a.
I - posterior interossoeus n.

Question 25

arterial supply to posterior forearm and hand

Answer 25

radial a. via deep palmar arch or via dorsal carpal arch (hand)

• common interosseus a. (posterior interosseus a.)
• perforating (posterior) branch of anterior interosseous a.

Question 26

nervous supply to posterior forearm

Answer 26

radial n.

• superficial branch of radial n. (lateral, runs beneath brachioradialis)
• deep branch of radial n. (posterior, becomes posterior interosseous n.)

Question 27

radial n. injury from fracture to humeral shaft can lead to

Answer 27

wrist-drop
paralysis of extensors of wrist and fingers resulting in inability to extend and thus the flexors “take-over” and wrist assumes a partially flexed position while in a relaxed posture

Question 28

fell on outstretched hand - wrist fracture - artery passing through anatomical snuff box damaged, what is one potential damage

Answer 28

avascular necrosis of scaphoid bone (floor of snuff box)

Question 29

describe the muscular borders of the anatomical snuff box

Answer 29

• EPL (ulnar border - more medial) - coming more posterior to the styloid process of radius
• EPB (radial border) - the extensors are NOT together!
• APL (runs with EPB)