Posterior forearm

Question 1

Deep fascia

Answer 1

Antebrachial fascia

Question 2

Cutaneous innervation of the posterior forearm

Answer 2

Intercostobrachial n.
Cutaneous branches of radial n.
Lateral cutaneous n. of forearm from musculocutaneous n.
Superficial branch of radial n.
Dorsal cutaneous branch of ulnar n.
Medial cutaneous n. of forearm

Question 3

Muscles of the posterior forearm

Answer 3

Primarily extensors of the and/or fingers
Can ABduct or ADduct the hand
ABduct towards radius
ADduct towards ulan
All innervated by radial n. and its branches

Question 4

Brachioradialis muscle

Answer 4

O: Proximal 2/3 of supracondylar ridge of humerus
I: distal radius (near styloid process of radius)
Inn: Radial n.
Actions: Weak flexor or forearm, strongest when forearm is in mid-pronate position
Well defined in baseball players

Question 5

Extensor carpi radialis longus muscle

Answer 5

O: lateral supracondylar ridge of humerus
I: Dorsal base of 2nd metacarpal
Inn: Radial n.
Actions: Extends and ABducts hand (active during fist clenching)

Question 6

Extensor carpi radilais brevis muscle

Answer 6

O: Lateral epicondyle of humerus
I: Dorsal base of 3rd metacarpal
Inn: Deep branch of radial n.
Actions: Extends and ABducts hand

Question 7

Extensor digitorum muscle

Answer 7

O: Lateral epicondyle of humerus
I: Middle and distal phalanx of digits 2-5 (via extensor hoods)
Inn: Deep branch of radial n.
Actions: Extends primarily at MCP (metacarpal phalange joint) and secondarily at IP (interphalange joint) joints of digits 2-5

Question 8

Extensor hoods and expansions

Answer 8

Aponeurotic hood
Flattening out of tendon
Formed from the 4 tendons of extensor digitorum m.
Median band - attached at base of middle phalanx
Lateral bands (2) - attaches at base of distal phalanx
Help muscles extend distally
Allow for attachment of intrinsic muscle of hand

Question 9

Extensor digiti minini muscle

Answer 9

O: Lateral epicondyle of humerus
I: 5th digit (extensor hood)
Inn: Deep branch of radial n.
Actions: extends 5th digit primarily at MCP and secondarily at IP joints

Question 10

Extensor carpi ulnaris muscle

Answer 10

O: lateral epicondyle and posterior proximal ulna
I: dorsal base of 5th metacarpal
Inn: Deep branch of radial n.
Actions: extends and ADducts the hand (active during fist clenching)

Question 11

Lateral epicondylisitis

Answer 11

“Tennis” elbow
Most common overuse injury
Repeated forceful flexion and extension of wrist
Strains the common extensor tendon
Produces inflammation of periosteum of lateral epicondyle (micro tears of muscle separating from bone)
Pain at lateral epicondyle that radiates down posterior forearm
Pain with opening door and lifting glass (supination)

Question 12

Supinator muscle

Answer 12

O: Lateral epicondyle of humerus, supinator crest of ulna
I: Lateral, anterior, and posterior aspect of radius
Inn: Deep branch of radial n.
Actions: supinates forearm
Deep branch of radial n. dives in and comes out as the posterior interossesous n.

Question 13

ABductor pollicis longus muscle

Answer 13

O: proximal posterior ulna, radius, and interosseous membrane
I: Base of 1st metacarpal
Inn: posterior interosseous n.
Actions: ABducts thumb

Question 14

Extensor pollicis brevis muscle

Answer 14

O: Distal 1/3 of posterior radius and interosseous membrane
I: Proximal phalanx of 1st digit
Inn: Posterior interosseous n.
Actions: extends thumb

Question 15

Extensor pollicis longus muscle

Answer 15

O: middle 1/3 of posterior ulna and interosseous membrane
I: distal phalanx of 1st digit
Inn: posterior interosseous n.
Actions: extends thumb

Question 16

Extensor indicis muscle

Answer 16

O: posterior distal 1/3 of ulna and interosseous membrane
I: 2nd digit (extensor hood)
Inn: Posterior interosseous n.
Actions: extends digit 2

Question 17

Synovial tendon sheaths

Answer 17

Extensor retinaculum - holds extensor tendons in place at wrist - prevents bow strining
Synovial tendon sheaths - cover tendons to reduce friction
Intertendinous connections - restrict independent extension of the fingers

Question 18

De Quervain Tenosynovitis

Answer 18

“Mommy’s thumb” or “Texting thumb”
Connected to activities involving extension of the thumb
Symptoms: pain or tenderness when moving thumb, turning wrist, grasping, or making fist
Swelling on radial side of dorsum of the hand
Tendons of extensor pollicis brevis and Abductor pollisic longs mm.

Question 19

Radial nerve

Answer 19

Divides into deep and superficial branches around cubital fossa
Deep branch of radial n. provides innervation as posterior interosseous n.