L36 Extensor Arm and Forearm

Question 1

What is the main nerve and artery in the extensor compartment of the arm?

What is the main action of the extensor arm?

Answer 1

Deep artery of the arm (profunda brachii artery)

Radial nerve

extension

Question 2

What is the radial groove?

Answer 2

bony feature on the posterior side of the humerus

divides triceps

where the radial nerve and deep artery of the arm course

Question 3

Triceps brachii

Answer 3

PA: long: infraglenoid tubercle

lateral: humerus superior to radial groove
medial: humerus inferior to radial groove

DA: olecranon process

Act: extends forearm

Inn: radial n

Question 4

Anconeus

Answer 4

PA: lateral epicondyle of humerus
DA: proximal ulna
Act: extend & stabilize elbow
Inn: radial n

Question 5

What muscles have PA attachment to the lateral epicondlye of the humerus?

Answer 5

Anconeus

extensor carpi ulnaris

extensor digiti minimi

extensor digitorum

extensor carpi radialis brevis

supinator

Question 6

What is an Olecranon Fracture?

Answer 6

“fractured elbow”

avulsion of triceps brachii attachment site (muscle breaking bone)

Question 7

What is bursitis of the elbow?

Answer 7

can be caused by a fall or repeated friction

“student’s elbow”

Question 8

Deep artery of the arm

Answer 8

main artery of extensor compartment

courses with radial nerve in radial groove

terminates at branching of radial collateral and middle collateral aa.

Question 9

Radial nerve

Answer 9

main extensor nerve of arm

courses with deep artery of the arm in radial groove

muscular and cutaneous branches

can be damaged with humerus fracture at midshaft

Question 10

Where do you test radial nerve reflex?

What spinal nerve is this testing?

Answer 10

triceps reflex tested on posterior portion of arm right above elbow

tests C7

Question 11

What are the main arteries and nerve of the extensor compartment of the forearm?

What are the main actions of the extensor compartment of the forearm?

Answer 11

radial and ulnar aa.

radial n.

supination of the forearm

extension, abduction, adduction of the wrist

extension of the digits

Question 12

What is a common extensor origin?

Answer 12

lateral epicondyle

Question 13

What muscles have a PA of the lateral supracondylar ridge?

Answer 13

brachioradialis

extensor carpi radialis longus

Question 14

Extensor carpi ulnaris

Answer 14

PA: lateral epicondyle of humerus
DA: 5th metacarpal (base)
Act: extends & adducts hand
Inn: radial n (deep branch)

Question 15

Extensor digiti minimi

Answer 15

PA: lateral epicondyle of humerus

DA: extensor expansion of digit 5

Act: extends hand & digit 5

Inn: radial n (deep branch)

Question 16

Extensor digitorum

Answer 16

PA: lateral epicondyle of humerus
DA: extensor expansion of digits 2-5
Act: extends hand & digits 2-5
Inn: radial n (deep branch)

Question 17

Brachioradialis

Answer 17

PA: lateral supracondylar ridge
DA: distal radius
Act: flexion of mid-pronated forearm (drinking water)
Inn: radial n

Question 18

Extensor carpi radialis longus

Answer 18

PA: lateral supracondylar ridge
DA: 2nd metacarpal (base)
Act: extend & abduct hand
Inn: radial n

Question 19

Extensor carpi radialis brevis

Answer 19

PA: lateral epicondyle of humerus
DA: 3rd metacarpal (base)
Act: extend & abduct hand
Inn: radial n (deep branch)

Question 20

Extensor pollicis longus

Answer 20

PA: ulna, interosseous membrane
DA: distal phalanx of digit 1
Act: extends digit 1
Inn: radial n (deep branch)

Question 21

Extensor indicis

Answer 21

PA: distal ulna
DA: extensor expansion of digit 2
Act: extends hand & digit 2
Inn: radial n (deep branch)

Question 22

What is the pulley for EPL tendon?

Answer 22

dorsal tubercle

Question 23

Supinator

Answer 23

PA: lateral epicondyle of humerus, proximal ulna
DA: proximal radius
Act: supinates forearm
Inn: radial n (deep branch)

Question 24

Abductor pollicis longus

Answer 24

PA: ulna, radius, interosseus membrane
DA: 1st metacarpal (base)
Act: abducts & extends digit 1 (thumb)
Inn: radial n (deep branch)

Question 25

Extensor pollicis brevis

Answer 25

PA: radius, interosseous membrane DA: proximal phalanx of digit 1 Act: extends digit 1 (but not at IP joint) Inn: radial n (deep branch)

Question 26

What is the bradioradialis reflex? Where is it tested and what spinal nerve does it test?

Answer 26

C6

Question 27

What is the extensor retinaculum?

Answer 27

CT that holds down tendons multiple tunnels, not a single tunnel like carpal tunnel

Question 28

What do the intertendinous connections do?

Answer 28

limit extension of individual digits

Question 29

What is lateral epicondylitis?

Answer 29

inflammation of common extensor origin and periosteum of the lateral epicondyle "tennis elbow"

Question 30

What are synovial cysts? What tendon is most common?

Answer 30

inflammation of synovial sheath also called "ganglionic" "myxoid" "mucous" cysts Most common is Extensor carpi radialis brevis

Question 31

What are the two branches of the radial nerve in the extensor forearm? What do they do?

Answer 31

**Superficial branch**: sensory in hand, digits 1-4.5, fingertips are median nerve **Deep branch**: motor to extensor forearm, distal portion often referred to as "posterior interosseous n." because it travels with the posterior interosseous artery

Question 32

What is the extensor expansion?

Answer 32

aponeurosis on dorsum of digits lateral bands go to distal phalanx median band to middle phalanx

Question 33

What is lateral band avulsion/rupture?

Answer 33

rupture/avulsion of distal extensor expansion loss of extension of distal phalanx "mallet finger" or "baseball finger"

Question 34

What is central band avulsion/rupture?

Answer 34

PIP flexed, DIP extended "Boutonniere deformity"

Question 35

What are the boundaries and contents of the anatomical snuffbox?

Answer 35

**Boundaries: **EPL medially EPB laterally APL even more laterally extensor retinaculum proximally **Contents**: Radial artery and nerve (superficial branch) scaphoid and trapezium

Question 36

What is a scaphoid fracture?

Answer 36

most frequently broken carpal bone often misdiagnosed as sprained wrist poor blood supply: slow healing/avascular necrosis

Question 37

What is the nerve innervation on the dorsum of the hand?

Answer 37

**ulnar n. (dorsal branch)**: 5th and half of 4th digit **radial n. (superficial branch)**: 1st to 4.5 digits except fingertips **median n. (proper digital branches):** fingertips of digits 1-4.5 no motor n. in dorsal hand

Question 38

What is the dorsal venous network comprised of?

Answer 38

basilic v on medial side and cephalic vein on lateral side

Question 39

What is the arterial supply of dorsal hand?

Answer 39

most blood supply in hand comes from palmar arches, but: dorsal carpal arch, a branch of the radial artery in snuffbox contributes