Lecture 14: Forearm extensor aspect

Question 1

Answer 1

Question 2

what causes wrist drop?

Answer 2

damage to radial nerve( e.g. upper humeral fracture) -> loss of innervation to the extensor muscles of the forearm-> cannot extend the wrist-> loses grip power-> cannot get any good strength from the forearm flexors( not in the optimal position)

Question 3

what are the 7 superficial extensor muscles of the forearm?

Answer 3

anconeus
extensor carpi ulnaris
extensor digiti minimi
extensor digitorum
extensor carpi radialis longus
extensor carpi radialis brevis

brachioradialis

Question 4

which 2 digits have their own extensor muscles?

Answer 4

2nd and 5th digits

extensor digiti minimi( pinky)
extensor indicis( index finger)

Question 5

what is the insertion of abductor pollicis longus?

Answer 5

1st metacarpal

Question 6

what is the insertion of extensor pollicis brevis

Answer 6

base of proximal phalanx of the 1st digit(thumb)

Question 7

what is the insertion of extensor pollicis longus?

Answer 7

base of distal phalanx of the 1st digit
(thumb)

Question 8

what is the insertion of extensor indicis?

Answer 8

DDEH(dorsal digital expansion hood)

Question 9

the anatomical snuff box serves as a landmark for what?

Answer 9

-scaphoid bone forms the floor of the snuff box
-radial artery
-formed by abductor pollicis longus, extensor pollicis brevi, and extensor pollicis longus

Question 10

O of the deep head of the supinator

Answer 10

Ulnar crest (Lateral olecranon)

Question 11

O of superficial head of supinator

Answer 11

lateral epicondyle of humerus

Question 12

supinator is a useful landmark for?

Answer 12

radial nerve

Question 13

is supination or pronation stronger on average?

Answer 13

pronation

Question 14

between which 2 muscles in the front arm can the radial nerve be found?

Answer 14

between brachialis and brachioradialis

Question 15

what muscles in the arm and forearm are innervated directly by the radial nerve( main branch)?

Answer 15

triceps and anconeus
brachioradialis
extensor carpi radialis longus

Question 16

what muscles are innervated by the deep branch of the radial nerve?

Answer 16

extensor carpi radialis brevis
supinator

Question 17

what muscles are innervated by the posterior interosseous nerve( branch of the radial n)?

Answer 17

extensor digitorum
extensor digiti minimi
extensor carpi ulnaris
abductor pollicis longus
extensor pollicis longus
extensor indicis
extensor pollicis brevis

Question 18

Answer 18

Question 19

Answer 19

Question 20

which muscles are stronger in the forearm: flexor or extensor?

Answer 20

flexor

Question 21

what is the defining characteristic of the extensor compartment?

Answer 21

all muscles of the extensor compartment are innervated by radial n

Question 22

how are the long tendons of extensor digitorum insert onto the fingers?

Answer 22

the long tendons of the the ED form the extensor expansion or hood over metacarpophalangeal joints and proximal phalanges and insert by three bands, a central one into the base of the middle phalanx and 2 lateral ones into the base of the distal phalanx.

Question 23

what is the cutaneous innervation/distribution of the forearm?

Answer 23

Medially(forearm): medial cutaneous nerve of the forearm from medial cord of brachial plexus.

Laterally(forearm): the lateral cutaneous nerve of the forearm(terminal portion of musculocutaneous nerve from the lateral cord)

Posteriorly: the posterior cutaneous nerve of the forearm ( a branch of radial n)

Question 24

what is the name of the branch of the radial nerve that passes in between the heads of the supinator m?

Answer 24

deep branch

when the nerve emerges in the posterior compartment it is the posterior interosseous nerve

Question 25

what branches does the radial nerve divide into as it enters the lateral aspect of the cubital fossa?

Answer 25

superficial branch(runs under brachioradialis)

deep branch