The posterior compartment of the forearm contains extensor muscles, the posterior interosseous nerve and arteries. It has superficial muscles like brachioradialis and deep muscles like supinator. The extensor retinaculum attaches proximally to the radius and distally to carpal bones. It divides the extensor tunnel into compartments for tendons like abductor pollicis longus and extensor pollicis brevis.

1. Posterior or Extensor
compartment of forearm

2. • Posterior Compartment of Forearm
• The posterior compartment of the forearm
contains extensor muscles, posterior
interosseous nerve and posterior
interosseous arteries.

3. Superficial Muscles
1. Brachioradialis
2. Extensor carpi radialis
longus
3. Extensor carpi radialis
brevis
4. Extensor digitorum
5. Extensor digiti minimi
6. Extensor carpi ulnaris.
7. Anconeus
Deep Muscles
1. Supinator
2. Abductor pollicis longus
3. Extensor pollicis longus
4. Extensor pollicis brevis
5. Extensor indicis.

4. SUPERFICIAL LAYER

5. DEEP LAYER

6. Muscles of the Lateral Fascial Compartment of
the Forearm

7. Brachioradialis

8. Brachioradialis
• Origin
• Lateral supracondylar
ridge of humerus
• Insertion
• Base of styloid
process of radius

9. • Action
• Flexes forearm atridge of humerus elbow joint
rotates forearm to the midprone position
• Nerve supply
• Radial nerve

10. Extensor carpi
radialis longus

11. Extensor carpi
radialis longus
• Origin
• Lateral supracondylar
ridge of humerus
• Insertion
• Posterior surface of base
of second metacarpal
bone

12. • Action
• Extends and abducts hand at wrist joint
• Nerve supply
• Radial nerve

13. POSTERIOR COMPARTMENT OF
FOREARM

14. Extensor carpi radialis
brevis

15. Extensor carpi
radialis brevis
• Origin
• Lateral epicondyle of
humerus
• Insertion
• Posterior surface of base
of third metacarpal
bone

16. • Action
• Extends and abducts hand at wrist joint
• Nerve supply
• Deep branch of radial nerve

17. Extensor
digitorum

18. Extensor digitorum
• Origin
• Lateral epicondyle of
humerus
• Insertion
• Middle and distal
phalanges of medial four
fingers

19. • Action
• Extends fingers and hand
• Nerve supply
• Deep branch of radial nerve

20. Extensor digiti
minimi

21. Extensor digiti minimi
• Origin
• Lateral epicondyle of
humerus
• Insertion
• Extensor expansion of little
finger

22. • Action
• Extends metacarpal phalangeal joint of little
finger
• Nerve supply
• Deep branch of radial nerve

23. Extensor carpi ulnaris

24. Extensor carpi ulnaris
• Origin
• Lateral epicondyle of
humerus
• Insertion
• Base of fifth metacarpal
bone

25. • Action
• Extends and adducts hand at wrist joint
• Nerve supply
• Deep branch of radial nerve

26. Anconeus

27. Anconeus
• Origin
• Lateral epicondyle of
humerus
• Insertion
• Lateral surface of olecranon
process of ulna

28. • Action
• Extends elbow joint
• Nerve supply
• Radial nerve

29. Supinator

30. Supinator
• Origin
• Lateral epicondyle of
humerus, anular ligament
of proximal radioulnar
joint, and ulna
• Insertion
• Neck and shaft of radius

31. • Action
• Supination of forearm
• Nerve supply
• Deep branch of radial nerve

32. Abductor pollicis
longus

33. Abductor pollicis
longus
• Origin
• Posterior surface of
shafts of radius and ulna
• Insertion
• Base of first metacarpal
bone

34. • Action
• Abducts and extends thumb
• Nerve supply
• Deep branch of radial nerve

35. Extensor
pollicis brevis

36. Extensor pollicis
brevis
• Origin
• Posterior surface of shaft
of radius
• Insertion
• Base of proximal phalanx
of thumb

37. • Action
• Extends metacarpophalangeal joints of thumb
• Nerve supply
• Deep branch of radial nerve

38. Extensor
pollicis longus

39. Extensor pollicis
longus
• Origin
• Posterior surface of shaft
of ulna
• Insertion
• Base of distal phalanx of
thumb

40. • Action
• Extends distal phalanx of thumb
• Nerve supply
• Deep branch of radial nerve

41. Extensor
indicis

42. Extensor indicis
• Origin
• Posterior surface of shaft of
ulna
• Insertion
• Extensor expansion of index
finger

43. • Action
• Extends metacarpophalangeal joint of index
finger
• Nerve Supply
• Deep branch of radial nerve

44. Extensor retinaculum

46. Its proximal attachment is to the anterolateral
border of the radius above the styloid
process.
It is not attached to the ulna; its distal
attachment is to The Pisiform and
triquetral bones.

47. Extensor retinaculum
From the deep surface of the extensor
retinaculum fibrous septa pass to the
bones of the forearm, dividing the
extensor tunnel into six compartments.

49. Extensor
retinaculum
1. The most lateral compartment lies over the lateral surface of
the radius at its distal extremity, and through it pass the
tendons of abductor pollicis longus and extensor pollicis
brevis, each usually lying in a separate synovial sheath.
2. The next compartment extends as far as the dorsal
tubercle, and conveys the tendons of the radial extensors
of the wrist (longus and brevis), each lying in a separate
synovial sheath.
3. The groove on the ulnar side of the radial tubercle lodges
the tendon of extensor pollicis longus, which lies within its
own compartment invested with a synovial sheath.

50. Extensor retinaculum
3. Between this groove and the ulnar border of the radius is a
shallow depression in which all four tendons of extensor
digitorum lie, crowded together over the tendon of extensor
indicis. All five tendons in this compartment are invested with
a common synovial sheath.
4. The next compartment lies over the radioulnar joint and
transmits the tendon of extensor digiti minimi in a synovial
sheath.
5. Lastly, the groove near the base of the ulnar styloid transmits
the tendon of extensor carpi ulnaris in its synovial sheath.

53. Structures on the Posterior Aspect of
the Wrist
Superficial to the extensor retinaculum from medial
to lateral
Dorsal (posterior) cutaneous branch
of the ulnar nerve
Basilic vein
Cephalic vein
Superficial branch of the radial nerve

54. Structures on the Posterior Aspect
of the Wrist
Deep to the extensor retinaculum from medial to lateral
Extensor carpi ulnaris
tendon
grooves the posterior aspect of the head
of the ulna
Extensor carpi ulnaris tendon grooves the posterior aspect of the head of
the ulna
Extensor carpi ulnaris tendon grooves the posterior aspect of the head of the
ulna
Extensor pollicis longus
tendon
winds around the medial side of the
dorsal tubercle of the radius.
Extensor carpi radialis
longus and brevis
tendons
share a common synovial sheath and are
situated on the lateral part of the posterior
surface of the radius.
Abductor pollicis longus and
the extensor pollicis brevis
tendons
have separate synovial sheaths but
share a common compartment.

56. Thanks