1. POSTERIOR COMPARTMENT OF
ARM AND FOREARM (AN12.11-
12.15)
DR RAJEEV PANWAR
ASSISTANT PROFESSOR
DEPT. OF ANATOMY
SSSMCRI
2. SPECIFIC LEARNING OBJECTIVE
To understand the gross anatomy of posterior compartment of arm and forearm.
To understand about applied anatomy related to posterior compartment of arm
and forearm
3. CONTENT
Posterior compartment of arm
• Muscles
• Blood supply
• Nerve supply
Posterior compartment of forearm
• Muscles
• Blood supply
• Nerve supply
Extensor retinaculum
Applied anatomy
5. CONTENT
• Muscle: Triceps muscle
• Nerve supply to muscle: Radial nerve
• Blood supply: Profunda brachii and ulnar collateral arteries
• Structures passing through compartment :Radial nerve and ulnar nerve
6. TRICEPS MUSCLE
• Origin:
• Long head (L): infraglenoid tubercle of the scapula
• Lateral head (Lat): Upper half of posterior surface of shaft of humerus
• Medial head (M): Lower half of posterior surface of shaft of humerus
• Insertion: Into upper surface of olecranon process of ulna
• Nerve Supply: radial nerve.
• Action: Extension of forearm at elbow joint.
L
Lat
M
7. RADIAL NERVE
• Origin - from posterior cord of brachial plexus in axilla
• Winds around back of arm in spiral groove
• In spiral groove - accompanied by profunda vessels, and it lies
directly in contact with shaft of humerus.
• Pierces lateral fascial septum above elbow
• Continues downward into cubital fossa in front of elbow,
between brachialis & brachioradialis muscles.
8. BRANCHES OF
RADIAL NERVE
• In axilla
• Muscular branches to long & medial heads of triceps
• Posterior cutaneous nerve of arm
9. BRANCHES OF RADIAL NERVE
• In spiral groove
• Muscular branches to lateral & medial
heads of triceps
• To anconeus muscle
• Lower lateral cutaneous nerve of arm
• Posterior cutaneous nerve of forearm
10. BRANCHES OF
RADIAL NERVE
• In axilla
• Muscular branches to long & medial heads of triceps
• Posterior cutaneous nerve of arm
• In spiral groove
• Muscular branches to lateral & medial heads of triceps
• To anconeus muscle
• Lower lateral cutaneous nerve of arm
• Posterior cutaneous nerve of forearm
• In anterior compartment of arm
• Muscular branches to
• Brachialis,
• Brachioradialis
• Extensor carpi radialis longus muscles.
• Articular branches to elbow joint
• Terminal branches
11. ULNAR NERVE
• Branch of medial cord of brachial plexus
• Pierces medial fascial septum & descends behind
septum
• Accompanied by superior ulnar collateral vessels
• At elbow - lies behind the medial epicondyle of
humerus
• Continues downward to enter forearm between two
heads of origin of flexor carpi ulnaris
12. PROFUNDA BRACHII ARTERY
• Arises from brachial artery near its origin.
• Accompanies radial nerve through spiral groove
• Supplies triceps muscle
• Takes part in anastomosis around elbow joint.
Superior and Inferior Ulnar Collateral Arteries
• Arise from brachial artery
• Take part in anastomosis around elbow joint
16. BRACHIORADIALIS
• Origin:
• From upper 2/3rd of lateral supracondylar ridge of humerus.
• Insertion:
• Into base of styloid process of radius.
• Nerve Supply: From radial nerve
• Action:
• Flexion of the forearm (specially in midprone position).
• Restoration of the forearm into the midprone position.
17. EXTENSOR CARPI
RADIALIS LONGUS
• Origin:
• From the lower 1/3rd of lateral supracondylar ridge of
humerus.
• Insertion:
• Into the posterior surface of the base of the 2nd metacarpal
bone.
• Nerve Supply: From radial nerve.
• Action:
• Extension of the hand at wrist joint.
18. EXTENSOR CARPI
RADIALIS BREVIS
• Origin:
• from the lateral epicondyle of the humerus (common
extensor origin).
• Insertion:
• Into the posterior surface of the base of the 3rd metacarpal
bone.
• Nerve Supply: From deep branch of radial nerve
(posterior interosseous nerve).
• Action:
• Extension of the hand at wrist joint.
• Abduction of the hand at wrist joint.
19. EXTENSOR
DIGITORUM
• Origin:
• From lateral epicondyle of humerus (common extensor
origin).
• Insertion: Into the extensor expansion of the medial 4
fingers.
• Nerve Supply: From deep branch of radial nerve.
• Action:
• Extension of metacarpophalangeal and interphalangeal joints
of medial 4 fingers.
20. EXTENSOR DIGITI
MINIMI
• Origin:
• from the lateral epicondyle of the humerus (common
extensor origin).
• Insertion: Into the extensor expansion of the little
finger
• Nerve Supply: From the deep branch of radial nerve.
• Action:
• Extension of metacarpophalangeal and interphalangeal joints
of the little finger
21. EXTENSOR CARPI
ULNARIS
• Origin:
• from lateral epicondyle of the humerus (common extensor
origin)
• Insertion: Into posterior surface of base of 5th metacarpal
bone
• Nerve Supply: From the deep branch of radial nerve.
• Action:
• Extension of the hand at wrist joint.
• Adduction of the hand at wrist joint.
22. ANCONEUS • Origin:
• From posterior aspect of lateral epicondyle of humerus.
• Insertion: Into lateral surface of olecranon process of ulna.
• Nerve Supply: From radial nerve.
• Action:
• Helps triceps in extension of elbow joint..
24. SUPINATOR • Origin:
• Lateral epicondyle of the humerus
• Annular ligament of the superior radio-ulnar joint
• Supinator fossa and crest of the ulna..
• Insertion: Into upper 1/3rd of lateral surface of shaft of radius.
• Nerve Supply: From deep branch of radial nerve..
• Action:
• Supination of the forearm at the radio-ulnar joints
25. ABDUCTOR
POLLICIS LONGUS
• Origin:
• From middle of the posterior surface of radius and ulna
• Interosseus membrane
• Insertion: Into posterior surface of base of 1st metacarpal
• Nerve Supply: From the deep branch of radial nerve..
• Action:
• Abduction and extension of thumb at carpo-metacarpal joint
26. EXTENSOR
POLLICIS BREVIS
• Origin:
• From posterior surface of shaft of radius (below abductor
pollicis longus)
• Insertion: : Into posterior surface of base of proximal
phalanx of thumb.
• Nerve Supply: From deep branch of radial nerve..
• Action:
• Extension of the metacarpophalangeal joint of the thumb.
27. EXTENSOR
POLLICIS LONGUS
• Origin:
• From the posterior surface of ulna (below abductor pollicis
longus)
• Insertion: Into posterior surface of base of the distal
phalanx of thumb.
• Nerve Supply: From deep branch of radial nerve..
• Action:
• Extension of the interphalangeal joints of the thumb
28. EXTENSOR INDICIS • Origin:
• From posterior surface of ulna (below extensor pollicis
longus)
• Insertion: Into extensor expansion of the index finger
• Nerve Supply: From deep branch of radial nerve..
• Action:
• Extension of all joints of the index finger
• helps in extension of the wrist joint.
29. RADIAL NERVE
• At lateral epicondyle, it divides into superficial
and deep branches
• Branches:
i. Muscular branches to
• Brachioradialis
• Extensor carpi radialis longus
• a small branch to lateral part of brachialis
muscle
ii. Articular branches to elbow joint
iii. Superficial branch of radial nerve
iv. Deep branch of radial nerve (posterior
interosseous nerve) enters posterior
compartment of forearm.
30. SUPERFICIAL
BRANCH OF RADIAL
NERVE
• Direct continuation of radial nerve
• Runs down under cover of brachioradialis muscle on lateral side
of radial artery
• Reaches posterior surface of wrist, divides into terminal
branches & supply skin on lateral two thirds of posterior surface
of hand and posterior surface over proximal phalanges of lateral
three & a half fingers
31. DEEP BRANCH OF
RADIAL NERVE
(POSTERIOR
INTEROSSEOUS
NERVE)
• Arises from radial nerve in front of lateral epicondyle of
humerus in cubital fossa .
• Pierce supinator to reach posterior compartment of
forearm.
• Descends in the interval between the superficial and deep
groups of muscles.
• Branches
• (1) Muscular branches to:
• Extensor carpi radialis brevis
• Supinator,
• Extensor digitorum
• Abductor pollicis longus,
• Extensor digiti minimi
• Extensor pollicis brevis
• Extensor carpi ulnaris
• Extensor pollicis longus,
• Extensor indicis
• (2) Articular branches - the wrist and carpal joints
32. RADIAL ARTERY
• Origin - Smaller of terminal branches of
brachial artery.
• Course
• Begins in cubital fossa at level of neck of radius.
• Passes downward and laterally and resting on
deep muscles of forearm.
• Radial artery leaves forearm by winding around
lateral aspect of wrist to reach posterior surface of
33. BRANCHES IN THE FOREARM
• Muscular branches to neighboringmuscles
• Radial recurrent artery- takes part in arterial anastomosis
around elbow joint
• Superficial palmar branch
• Arises just above wrist, enters the palm of the hand
• Joins ulnar artery to form superficial palmar arch
34. EXTENSOR RETINACULUM
• Strong, fibrous band which extends obliquely
across the back of the wrist.
• Attachment:
• Laterally - anterior border of distal end of
radius
• Medially - triquetral and pisiform bones
• Function
• Prevents projection of tendons across wrist joint.
35. STRUCTURES PASSING BELOW THE RETINACULUM (FROM LATERAL TO
MEDIAL )
I. Abductor pollicis longus (APL) & Extensor
pollicis brevis (APB)
II. Extensor carpi radialis longus (ECRL)
&Extensor carpi radialis brevis (ECRB)
III. Extensor pollicis longus (EPL)
IV. Extensor digitorum (ED) & Extensor indicis
(EI)
Posterior interosseous nerve
Anterior interosseous artery
V. Extensor digiti minimi (EDM)
VI. Extensor carpi ulnaris (ECU)
39. INJURY OF RADIAL
NERVE IN AXILLA
• Radial nerve may be injured by pressure of upper end of crutch
(crutch palsy)
• Motor loss
• Loss of extension of elbow—due to paralysis of triceps.
• Loss of extension of wrist—due to paralysis of wrist extensors
(wrist drop due to unopposed action of flexor muscles of
forearm)
• Loss of extension of digits—due to paralysis of ED, EI, EDM, EPL
• Loss of supination in extended elbow because supinator and
brachioradialis are paralyzed
• Sensory loss
• Sensory loss on small area of skin over posterior surface of
lower part of arm.
• Sensory loss along narrow strip on back of forearm.
• Sensory loss on lateral part of dorsum of hand at base of
thumb and dorsal surface of lateral 3½ digits.
40. INJURY OF RADIAL
NERVE IN RADIAL
/SPIRAL GROOVE
Radial nerve may be injured due to:
• Midshaft fracture of humerus,
• Wrongly placed intramuscular injection
• Direct pressure on radial nerve by a drunkard falling asleep with arm
over back of chair (Saturday night paralysis)
• Most commonly in distal part of groove beyond origin of nerve to
triceps & cutaneous nerves.
• Motor loss
• Loss of extension of the wrist and fingers.
• Wrist drop.
• Loss of supination when the arm is extended.
• Sensory loss
• Restricted only to a variable small area over dorsum of hand
between first and second metacarpals.
Saturday night
paralysis
41. INJURY OF RADIAL
NERVE AT ELBOW
Radial tunnel syndrome:
• Entrapment neuropathy of deep branch of radial nerve at
elbow.
• Compression of radial nerve at elbow may be caused by :
• Fibrous bands, which can tether the radial nerve to radio-
humeral joint.
• Sharp tendinous margin of ECRB
• Leash of vessels from radial recurrent artery.
• Arcade of Frohse, a fibro-aponeurotic proximal edge of
superficial part of supinator muscle
• Characteristic clinical features:
• Loss of extension of wrist and fingers but no wrist drop.
