Posterior Forearm and Dorsal Hand

Question 1

Which group of the posterior compartment of the forearm crosses the elbow?

Answer 1

the SF group, the deep group does not

Question 2

What is the innervation rule for the posterior forearm?

Answer 2

radial nerve (C5-C8)

Question 3

What are the actions of the posterior compartment of the forearm?

Answer 3

extend wrist and fingers

Abduct and adduct the wrist

supinate forearm

Extend, abduct and reposition the thumb

Question 4

What is the extensor retinaculum?

Answer 4

band of deep fascia that holds long extensor tendons in place as they cross the wrist, tendons are surrounded by synovial sheaths for movement

Question 5

What are synovial “ganglionic” cysts?

Answer 5

fluid filled swellings that can develop within the synovial sheaths, unknown cause

movement enlarges cysts

most common: synovial sheath of extensor carpi radialis brevis

Question 6

What is the origin for the superficial group of the posterior compartment of the forearm?

Answer 6

lateral epicondyle of the humerus

Question 7

What is lateral epicondylitis (tennis elbow)?

Answer 7

inflammation of common extensor origin and periosteum of the lateral epicondyle

Question 8

What are the muscles of the SF group of the posterior compartment of the forearm?

Answer 8

brachioradialis

extensor carpi radialis longus

extensor carpi radialis brevis

extensor carpi ulnaris

extensor digiti minimi

Question 9

Insertion of brachioradialis? Action?

Answer 9

distal radius

flex elbow joint*

Question 10

What does the brachioradialis reflex test assess?

Answer 10

radial nerve and the C6 spinal level

Question 11

Insertion of extensor carpi radialis longus and extensor carpi radialis brevis? Action?

Answer 11

radial side of hand

extend and abduct wrist joint

Question 12

Insertion of extensor carpi ulnaris? Actions?

Answer 12

ulnar side of hand

extend wrist, adduct wrist

Question 13

Insertion of extensor digitorium? actions?

Answer 13

forms extensor expansions of digits 2-5

extend digits (MCP, PIP and DIP) extend wrist joint

Question 14

insertion of extensor digiti minimi? action?

Answer 14

helps form extensor expansion of digit 5

extend digit 5 (MCP, PIP, DIP)

Question 15

Origins of the deep group of the posterior compartment of the forearm?

Answer 15

ulna, radius, interosseous membrane

most do not cross elbow

Question 16

What are the muscles of the deep group of the posterior compartment of the forearm?

Answer 16

abductor pollicis longus

extensor pollicis brevis

extensor pollicis longus

extensor indicis

supinator

Question 17

Insertion of abductor pollicis longus? Actions?

Answer 17

base of MC1

abduct and extend thumb at CMC joint

Question 18

Insertion of extensor pollicis brevis? Action?

Answer 18

proximal phalanx of pollux

extend thumb at CMC and MCP joints

Question 19

Insertion of extensor pollicis longus? Action?

Answer 19

distal phalanx of pollux

extend thumb at CMC, MCP and IP joints

Question 20

Insertion of extensor indicis? action?

Answer 20

extensor expansion of digit 2

extend digit 2 (MCP, PIP and DIP joints)

Question 21

Insertion of supinator? Action?

Answer 21

proximal radius

supinate forearm

Question 22

Name the pronators. What innervates them?

Answer 22

pronator teres

pronator quadratus

both innervated by median nerve

Question 23

Name the supinators. What innervates them?

Answer 23

supinator- radial n.

biceps brachii-musculocutaneous n.

Question 24

What resides in the dorsal hand?

Answer 24

long extensor tendons only

no intrinsic muscles

Question 25

Anatomical stuff box

Answer 25

depression proximal to thumb on dorsal hand

Lateral border: tendons of abductor pollicis longus & extensor pollicis brevis

Medial border: tendon of extensor pollicis longus

Question 26

What makes up the floor of the anatomical snuff box? What are its contents?

Answer 26

scaphoid and trapezium

contents: radial artery

Question 27

Why is the anatomical snuff box clinically relevant?

Answer 27

pain and tenderness of the snuff box may indicate a scaphoid fracture

Question 28

Where does the radial nerve travel?

Answer 28

in the radial groove with the deep artery and vein of the arm

Question 29

posterior cutaneous nerve of the forearm

Answer 29

branch off the radial nerve, innervates the skin on the posterior forearm

Question 30

Deep branch of the radial nerve (posterior interosseous n.)

Answer 30

motor to posterior compartment of the forearm

Question 31

What does the superficial branch of the radial n. innervate?

Answer 31

sensory to skin of lateral wrist (snuff box) and lateral aspect of dorsal hand

Question 32

What would happen if you severe your radial nerve in the axilla (proximal lesion)?

Answer 32

• extension of elbow lost
• flexion of elbow weakened (biceps brachii and brachialis intact)
• supination weakened (biceps brachii intact)
• extension of wrist loss (wrist drop)
• extension of MCP joints lost
• weakened abduction/adduction of wrist
• weakened extension of PIP and DIP joints digits 2-5
• abduction of thumb weakened
• extension of thumb lost
• sensory deficits of posterior arm, forearm and dorsolateral wrist/hand

Question 33

How can you test the radial nerve?

Answer 33

extension of elbow, wrist and MCP joints

cutaneous sensation of dorsolateral hand