3.6

Question 1

Superficial extensor group of the posterior forearm

Answer 1

1. brachioradialis
2. extensor carpi radialis longus
3. extensor carpi radialis brevis
4. extensor digitorum
5. extensor digiti minimi
6. extensor carpi ulnaris

Question 2

Deep extensor group of the posterior forearm

Answer 2

1. supinator
2. abductor pollicis longus
3. extensor pollicis longus
4. extensor pollicis brevis
5. extensor indicis

Question 3

Extensor expansion

Answer 3

Extensor digitorum tendon flares outward at digits
Central band inserts on middle phalanx
Two lateral bands insert onto distal phalanx
Also known as extensor hood because of how it wraps around digits.

Question 4

Radial nerve

Answer 4

Courses in radial groove of posterior humerus
Give off cutaneous branches
Anterior to lateral epicondyle
Splits into superficial and deep branches in cubital fossa
Innervates extensor muscles of arm and forearm
Sensory innervation to dorsal hand

Question 5

Superficial branch of radial nerve

Answer 5

Cutaneous to dorsum of hand
- Courses deep to brachioradialis
- Crosses anatomical snuffbox to enter hand

Question 6

Deep branch of radial nerve

Answer 6

Motor to forearm muscles
- Pierces supinator to enter posterior compartment of forearm
- Name changes to posterior interosseous nerve

Question 7

Radial nerve injury

Answer 7

Common causes:
- Humeral fracture (mainly shaft)
- Constriction of wrist from tight bracelet or handcuff affects superficial branch
- Crutch palsy: compression of the axilla from crutches
- Saturday night palsy: leaning arm over back of chair and falling asleep
- Honeymoon palsy: compression from another sleeping on arm overnight

Question 8

Posterior forearm arteries

Answer 8

The ulnar artery gives off the common interosseous branch soon after is originates at the brachial artery bifurcation. The interosseous artery quickly splits to form anterior and posterior interosseous arteries that course along each side to the interosseous membrane.
The posterior interosseous artery joins the posterior interosseous nerve. They run together between the superficial and deep muscle group in the posterior forearm.

Question 9

Avulsion of the medial epicondyle

Answer 9

Most common epicondyle fracture
Typically occurs in children. The epiphysis of the medial epicondyle has not yet fused to the humerus.
Potential damage to ulnar nerve.
Lateral epicondyle fractures are much less common. When they do occur the radial nerve is endangered

Question 10

Lateral epicondylitis

Answer 10

Also called tennis elbow
Inflammation or degeneration of the common extensor tendon
Primary cause:
- Overuse, usually repetitive motions requiring vigorous use of forearm
- Extensor carpi radialis brevis is usually involved

Question 11

DeQuervain’s Tenosynovitis

Answer 11

Thickening of tendons and synovial sheaths of extensor pollicis brevis and abductor pollicis longus.
Idiopathic or related to overuse
Pain, swelling at base of thumb
Grip difficulty

Question 12

Anatomical snuffbox

Answer 12

Boundaries:
- tendons of extensor pollicis brevis and abductor pollicis longus
- tendon of extensor pollicis longus
Overlies the scaphoid - palpate fractures
Scaphoid is easily fractured by fall on outstretched hand.

Question 13

Clinical important of anatomical snuffbox

Answer 13

Scaphoid is most easily palpable here. Scaphoid is the most frequently fractured carpal bone, which leads to pain in the snuffbox.
Radial pulse is palpable here as it crosses the floor.

Question 14

Synovial cysts

Answer 14

Also called ganglion cysts
Non-tendon swelling usually on the dorsum of wrist (extensor tendons) caused by leakage of joint fluid into surroundings
Cause is unknown
May cause pain with wrist flexion
Often treated by bashing cyst with a large book