describes all the features of back of forearm and dorsum of hand. also describes the clinical importance of the structures.

1. Back of forearm and
dorsum of hand
Dr. Laxman Khanal
Assistant Professor
Department of Human Anatomy
11-11-2016

2. Objectives
• Learn the skeletal components of posterior
forearm and dorsum of hand.
• Identify the seven superficial and five deep
muscles of posterior forearm.
• Find the posterior interosseous nerve and artery.
• Find extensor retinaculum and identify the
structures on the dorsal aspect of the wrist.
• Know the boundaries and content of anatomical
snuff box.
• Different components of dorsum of hand.

3. Q. Posterior interosseous artery is the branch of.
a. Radial artery b. Ulnar artery
c. Brachial artery d. Axillary artery
Q. How many muscles are found on back of forearm?
a. 8 b. 10
c. 12 d. 7
Q. Posterior interosseous nerve is the branch of.
a. Radial nerve b. Ulnar nerve
c. Median artery d. Axillary nerve

4. Q. Identify the bone.
a.Trapezium
b.Scaphoid
c. Triquetral
d.Lunate

5. Q. Which is not true for the marked triangular space?
a. It contain radial artery
b. Floor is formed by scaphoid
c. Roof contain cephalic vein
d. Skin area is supplied by ulnar nerve

6. A
B
C
A
B
C
Median nerve
Ulnar nerve
Axillary nerve
Radial nerve
Musculocutaneous nerve

7. Introduction
• Forearm is divided into two compartments (flexor
and the extensor) by the partition formed by
radius, ulna and interosseous membrane.
• Posterior interosseous nerve and artery are chief
neurovascular structures of back of forearm.
• Seven superficial and 5 deep group of muscles are
present in this compartment.
• Wrist drop is the common sign in paralysis of these
muscles.

8. SLTP

9. Fracture of distal end of radius
Distal end displaces dorsally
Distal end displaces ventrally

11. Colle’s or Smith ???

12. Muscles of extensor compartment of
forearm
Superficial group- seven 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
All the superficial muscles (except three)takes origin from
common extensor origin of lat epicondyle.

13. BR
ExDigi
ExDigimi
ExCU
Superficial muscles
1. Brachioradialis
2. Ex carpi radialis longus
3. Ex carpi radialis brevis
4. Ex digitorum
5. Ex digiti minimi
6. Ex carpi ulnaris
7. Anconeus

14. Extensor
retinaculum
Superficial muscles
1. Brachioradialis
2. Ex carpi radialis longus
3. Ex carpi radialis brevis
4. Ex digitorum
5. Ex digiti minimi
6. Ex carpi ulnaris
7. Anconeus

15. Superficial muscles
1. Brachioradialis
2. Ex carpi radialis longus
3. Ex carpi radialis brevis
4. Ex digitorum
5. Ex digiti minimi
6. Ex carpi ulnaris
7. Anconeus

16. Deep group of muscles- 5 in number
1. Abductor pollicis longus
2. Extensor pollicis longus
3. Extensor pollicis brevis
4. Extensor indicis
5. supinator
None of these muscles cross elbow joint.

17. 1. Abductor pollicis longus
2. Extensor pollicis brevis
3. Extensor pollicis longus
4. Extensor indicis
5. Supinator
Anatomical snuff box

18. Common interosseous artery
Anterior interosseous artery
posterior interosseous artery
Ulnar artery

19. • Posterior interosseous nerve
comes to the posterior
compartment through the gap
between two layers of supinator
muscle.
• Posterior interosseous artery
comes to the posterior
compartment through the gap in
proximal part of IOM.

20. Anatomical snuff box
The anatomical snuff box is a surface anatomy feature. It
appears as a triangular depression on the lateral surface of
the wrist on full extension of the thumb.
Medial boundary- EPL
Lateral boundary- AbPL +EPB
Roof- Cephalic vein and superficial b/o radial nerve.
Floor- Scaphoid bone
Content- radial artery
Tenderness in the box signifies fracture of scaphoid bone.

21. Anatomical snuff box, remember !!
1 bone- scaphoid
1 artery- radial artery
1 vein- cephalic vein
1 nerve- superficial b/o radial nerve
3 tendons- APL+EPB and EPL

22. U
R
Compartment 1= lat boundary of anatomical snuff box
Compartment 3= medial boundary of anatomical snuff box
Compartment 4= four structures
Extensor retinaculum and its compartments
5th compartment for little finger

23. Nerve supply of posterior
compartment
•All the muscles on the back of
forearm are supplied by the
posterior interosseous nerve except
brachioradialis, extensor carpi
radialis longus, and anconeus,
which are supplied by the radial
nerve directly.
These three muscles ????

24. Superficial
muscle
Common interosseous artery
Post interosseous artery
Ant interosseous artery

25. Wrist drop: This condition is
caused by a radial nerve injury
that results in paralysis of the
extensor muscles in the forearm.
De Quervain’s tenosynovitis:
caused by repetitive movement
and involve abductor pollicis
longus and extensor pollicis
brevis. Movements of the thumb
are painful.

26. Dorsum of hand

27. Dorsum of hand
• Skin
• Superficial fascia- contain dorsal venous arch
• Superficial branch of radial nerve
• Dorsal branch of ulnar nerve
• Deep fascia
• Extensor tendons
Median nerve

28. Superficial veins on the dorsal
aspect of the hand are often
visible and can be accessed for
numerous procedures.
Basilic vein
Cephalic vein

29. Cutaneous innervation of dorsum of hand
Radial Nerve
Ulnar Nerve
Median Nerve

30. Extensor tendons and
Dorsal digital expansion
Expansion of tendon of Ext Digitorum over the MP joint
which covers dorsal and lateral side of proximal phalanx like
a hood.

31. Dorsal digital expansion
• It is triangular flat sheet of aponeurosis related
with the tendon of extensor digitorum (Expansion)
Found in dorsum (Dorsal) of proximal phalanx
(Digital).
• Also called as extensor hood.
• Provides the insertion of the lumbrical and
interosseous muscles and the extensor indicis and
extensor digiti minimi muscles.

33. • Mallet finger
• Baseball finger
• Cricketer’s finger
Insertion of extensor tendon to the distal phalanx
is torn by forceful blow to the tip of finger.

34. Conclusion
• Muscles: 7+5
• Nerve: post interosseous nerve
• Artery: post interosseous artery
• Extensor retinaculum: 6 compartment with 9
muscles+1 artery +1 nerve.
• Anatomical snuff box : boundaries and contents.
• Formation of dorsal digital expansion.