Posterior Aspect of the Forearm

8/11/2019 Posterior Aspect of the Forearm

1/17

1


2/17

2

In two layers:

a superficial layera deep layer.


3/17

3

Common origin lateral

epicondyle of the humerus

Except for the

brachioradialis and

anconeus, extend as

tendons into the hand.

Brachioradialis

Extensor carpi radialis longus

Extensor carpi radialis brevis

Extensor carpi ulnaris

Extensor digitorum

Extensor digiti minimi

Base of 2nd

metacarpal

Base of 3rd

metacarpalBase of 5th

metacarpal

Anconeus

Proximal part of

supraepicondylar ridge of

humerus

Lateral surface of distal

end of radius proximal

to styloid process

Distal part of supraepicondylar

ridge of humerus

Base of 2nd metacarpal

Lateral epicondyle of

humerus

common extensor origin

Base of 3

rd

metacarpals


humerus

common extensor origin

Base of the 5th

metacarpal


humerus

dorsal aspects of the

bases of the middle

and distal phalanges of

the medial four digits

Lateral

epicondyle of

humerus

Extensor

expansion

(hood) ofthe 5thdigit

Lateral epicondyle

of humerus

Olecranon and proximal

posterior surface of ulna


4/17

4


5/17

5


6/17

6

Except for the supinator muscle, all these deep layer muscles originate from the

posterior surfaces of the radius, ulna, and interosseous membrane and pass into

the thumb and fingers.

Supinator

Abductor pollicis longus

Extensor pollicis brevis

Extensor pollicis longus

Extensor indicis

Superficial (humeroulnar) head

lateral epicondyle of

humerus

radial collateral and anular

ligaments

Deep (ulnar) headSupinator crest of the ulna

Lateral surface of radius

superior to the anterior

oblique line

Posterior surface of proximal

halves of ulna, radius, and

interosseous membrane

Base of 1st

metacarpal

Posterior surface of middle third of ulna and


Dorsal surface of base of distal phalanx of thumb

Posterior surface of distal third of radius and


Dorsal surface of base of proximal phalanx of the

thumb

Posterior surface of

distal 1/3 of ulna

and

interosseous

membrane

Extensor

expansion

(hood) of 2nd

digit


7/17

7


8/17

8


9/17

9


10/17

10


11/17

11


12/17

12

Muscle Main Action

Brachioradialis Relatively weak flexion of forearm; maximal when forearm is in

midpronated position; an accessory of flexor of the elbow joint

Extensor carpi

radialis longus(ECRL)

Extend and abduct hand at the wrist joint; ECRL active during fist

clenching

Extensor carpi

radialis brevis

(ECRB)

Extensor

digitorum Extends medial four digits primarily at metacarpophalangeal joints,secondarily at interphalangeal joints ; can also extend the wrist

Extensor digiti

minimi (EDM)

Extends the little finger

Extensor carpi

ulnaris (ECU)

Extends and adducts hand at wrist joint (also active during fist

clenching)

Anconeus Abduction of the ulna in pronation; accessory extensor of the elbow

joint; assists triceps in extending forearm


13/17

13

Muscle Muscle Action

Supinator Supinates forearm; rotates radius to turn palm anteriorly or superiorly (if

elbow is flexed)

Extensor indicis Extends 2nd digit (enabling its independent extension); helps extend hand

at wrist

Abductor

pollicis longus

(APL)

Abducts carpometacarpal joint of thumb; accessory extensor of the thumb

Extensor

pollicis longus

(EPL)

Extends distal phalanx of thumb at interphalangeal joint; extends

metacarpophalangeal and carpometacarpal joints

Extensor

pollicis brevis

(EPB)

Extends proximal phalanx of thumb at metacarpophalangeal joint; extends

carpometacarpal joint


14/17

14

Brachioradialis

Extensor carpi radialis longus

Radial nerve Main nerve)

Supinator

Extensor carpi radialis brevis

Deep branch of radial nerve

Rest

Posterior interosseous nerve

continuation of deep branch ofradial nerve


15/17

15

Radial artery

Posterior interosseous

artery

origin:

common interosseous branch of

the ulnar artery

recurrent interosseous artery

nd by joining to dorsal

carpal arch of the wrist

Anterior interosseous

artery

origin:

common interosseous branch of

the ulnar artery


16/17

16

Deep branch becomes posterior interosseous nerve

after emerging from between 2 heads of supinator

Posterior interosseous nerve

passes deep to extensor pollicis longus to reach

the wrist.
http://www.jaaos.org/content/19/7/430/F4.expansionhttp://www.jaaos.org/content/19/7/430/F4.expansion


17/17

17

Deep branch becomes posterior interosseous nerve

after emerging from between 2 heads of supinator

Documents

Posterior Aspect of the Forearm