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RADIAL NERVE 

Terminal branch of posterior cord 

C5, 6, 7, 8, T1 

Arises posterior to 3rd part of axillary artery 

In spiral groove of humerus it is accompanies by profunda brachii artery 

Fracture of shaft of humerus injures radial nerve & profunda brachii artery 

Anterior to lateral epicondyle it gives posterior interroseous branch & continues downwards as superficial radial nerve 

Passes deep to brachioradialis 

LINK: Radial nerve - 3D anatomy *** 

https://www.youtube.com/watch?v=3M6dzH1i-GI

RADIAL NERVE INJURY 

In axilla (Saturday night paralysis) 

Motor 

Loss of elbow extension 

Loss of forearm pronation 

Wrist drop & finger drop 

Sensory 

Loss at base of thumb 

In spiral groove 

Same as above + CAN extend arm 

POSTERIOR INTEROSSEOUS NERVE 

Branch of radial 

Pierces supinator muscle 

Branches 

Supplies 2 muscles BEFORE piercing supinator 

extensor carpi radialis 

supinator 

Supplies 7 muscles AFTER piercing supinator 

Extensor carpi ulnaris 

Extensor digitorum 

Extensor digiti minimi 

Extensor indices 

ABDuctor pollicis longus 

Extensor pollicis brevis 

Extensor pollicis longus 

INJURY 

Only finger drop (No extension of IP joints) 

In fracture of shaft of humerus:

If patient cannot extend wrist but there is no sensory effect - injury to posterior interosseous nerve. 

If patient cannot extend wrist & sensation is affected - injury to radial nerve 

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DERMATOMAL DISTRIBUTION UPPER LIMB 

C4 

Supraclavicular nerve (C2, 3, 4)

Cholecystitis or subphrenic abscess --> shoulder tip pain (same root as phrenic nerve) 

C6

Lateral border of forearm 

Thumb 

C7

Middle finger 

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MUSCULOCUTANEOUS NERVE 

Origin

continuation of lateral cord of brachial plexus

formed from anterior divisions of superior and middle trunks

Course

it leaves the axilla by piercing coracobrachialis muscle

it then passes down the arm beneath biceps muscle

it ends as the lateral cutaneous nerve of forearm

Sensory supply

skin of lateral forearm

Motor supply

anterior compartment of arm (BBC)

biceps – flexes elbow, supinates forearm

brachialis – flexes elbow

coracobrachialis – flexes and adducts the arm at the glenohumeral joint

CLINICAL FEATURES OF MUSCULOCUTANEOUS NERVE PALSY

SENSORY LOSS

numbness over lateral forearm

MOTOR DEFICIT

paralysis of anterior compartment of arm – very weak elbow flexion and weak forearm supination

absent biceps reflex

DEFORMITY

wasting of anterior compartment of arm

elbow usually held in extension with forearm pronated

A stab wound in the axilla with loss of sensation in lateral forearm indicates injury to musculoskeletal nerve (BBC muscles) 

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AXILLARY NERVE 

From posterior cord of brachial plexus

C5, 6

Passes through quadrangular space 

Passes around surgical neck of humerus 

Injury 

In fracture of surgical neck of humerus 

Motor - paralysis of deltoid muscle & teres minor 

Sensory - loss of skin sensation over lateral 1/2 of deltoid 

Deformity - flattened shoulder 

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BRACHIAL PLEXUS INJURIES 

Complete brachial plexus injury 

Motor changes - affects all muscles of upper limb 

Sensory changes - anaesthesia of whole upper limb EXCEPT:

Medial side forearm (intercosto-brachial nerve) 

Skin over upper part of deltoid (supraclavicular nerve from cervical plexus) 

UPPER TRUNK INJURY (C5-C6): ERB-DUCHENNE PARALYSIS

Motor changes - policeman tip deformity (aka waiter’s tip deformity) 

Sensory changes - anaesthesia over deltoid muscle

LOWER TRUNK INJURY (C8-T1): KLUMPKE’S PARALYSIS 

Motor changes - complete claw hand 

Sensory changes - anesthesia along medial aspect of forearm & medial 3 1/2 fingers 

Horner’s syndrome - due to sympathetic paralysis (T1)

MEDIAL CORD INJURY

Motor changes - Paralysis of long flexors of fingers & paralysis of all intrinsic muscles of hand 

Sensory changes - loss of cutaneous sensation over anterior surface of palm & fingers 

THORACIC OUTLET SYNDROME 

C8-T1 

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BRACHIAL PLEXUS 

Branches

Lateral cord 

Lateral pectoral nerve (C5, 6, 7) 

Lateral root of median nerve (C5, 6, 7)

Musculocutaneous nerve (C5, 6, 7) 

Medial cord 

Medial pectoral nerve (C8, T1) 

Medial root of median nerve (C8, T1)

Medial cutaneous nerve of forearm (C8, T1) 

Ulnar nerve (C7, 8, T1) 

Posterior cord 

Upper subscapular nerve (C5, 6)

Lower subscapular nerve (C5, 6)

Nerve to latissimus dorsi (C6, 7, 8)

Axillary (circumflex) nerve (C5, 6) 

Radial nerve (C5, 6, 7, 8, T1) 

Roots are posterior to scalenus anterior 

Cord is medial to axillary artery 

LINK: Drawing the brachial plexus 

https://www.youtube.com/watch?v=GLJuSRYamus

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VENOUS DRAINAGE OF UPPER LIMB 

Cephalic vein drains into axillary vein 

Basilic vein continues as axillary vein 

LINK: Upper limb veins : 3D anatomy 

https://www.youtube.com/watch?v=0bBHUcGK7P0

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Deep palmar arch 

Formed mainly by radial artery & completed by branch of ulnar artery 

Superficial palmar arch 

Formed mainly by ulnar artery & completed by a branch of radial artery 

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BRACHIAL ARTERY 

Begins at lower border of teres minor 

Ends in cubital fossa opposite neck of radius (divides into ulnar & radial arteries) 

RELATIONS

Anterior to triceps, coracobrachialis & brachialis muscles 

Medial to biceps 

Crossed by median cubital vein in cubital fossa 

Crossed by median nerve 

BRANCHES 

1- Profunda brachii 

Arises just below lower border of teres major 

enters spiral groove with radial nerve 

branches 

ascending branch (shares in anastomosis around surgical neck of humerus) 

2 descending branches (elbow anastomosis) 

2- Nutrient artery to humerus 

3- Superior & inferior ulnar collateral arteries 

In supracondylar fracture of humerus + distal pulse --> damage to brachial artery 

LINK: Brachial artery & its branches 

https://www.youtube.com/watch?v=o8HIFZYBDiI

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AXILLARY ARTERY BRANCHES 

1st part 

Superior thoracic artery 

2nd part 

Thoraco-acromial artery (* damaged when opening clavipectoral fascia) 

Lateral thoracic artery 

3rd part 

Scapular circumflex artery 

Anterior circumflex humeral artery 

Posterior circumflex humeral artery 

STEAL PHENOMENON

Diagnosed by duplex scan 

Presentation: patients have syncopal attacks when exercising the upper limb  (With any effort of upper limb - vasodilation occurs & blood shifts from the vertebral artery to upper limb - results in brain ischemia - leads to the syncopal attacks)

Obstruction proximal to thyro-cervical trunk 

LINK : Axillary artery with easy mnemonics: 

https://www.youtube.com/watch?v=MZFEt_3ng-0

LINK: Axillary artery branches 

https://www.youtube.com/watch?v=-5SNkcrWXvo

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DUPUYTREN’S CONTRACTURE

A contracture of palmar aponeurosis

Affects medial part

Leads to - MP FLEXION (Sometimes proximal IP joint)

DIP JOINT IS NOT AFFECTED

Seen in patients with liver cirrhosis

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ANATOMICAL SNUFFBOX

Boundaries

Medially - Extensor pollicis longus (3rd compartment)

Laterally - Abductor pollicis longus & extensor pollicis brevis (1st compartment)

CONTENTS

Radial artery

Cephalic vein

Trapezium

Scaphoid

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CUBITAL FOSSA 

*CONTENTS OF CUBITAL FOSSA 

From medial to lateral:

Median nerve 

End of brachial artery 

Biceps tendon 

Radial nerve 

Supra-trochlear LN’s 

Median cubital vein of forearm is formed by junction between basilic & cephalic vein - in the superficial cubital fossa 

Good explanation about BOUNDARIES and CONTENTS:

https://www.youtube.com/watch?v=QYbDlxJ-DJM

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UPPER TRIANGULAR SPACE 

CONTENTS: Circumflex scapular artery (from subscapular artery) 

LOWER TRIANGULAR SPACE 

CONTENTS: Radial nerve & profunda brachii artery 

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QUADRANGULAR SPACE 

Boundaries 

Medially - long head of triceps 

Laterally - surgical neck of humerus 

Inferiorly - teres major 

Superiorly

Subscapularis (anteriorly) 

Teres minor (posteriorly) 

CONTENTS - Axillary nerve & posterior circumflex humeral vessels 

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EXTENSORY COMPARTMENTS (6 COMPARTMENTS)

COMPARTMENT 1 

APL (abductor pollicis longus)

EPB (extensor pollicis brevis)

COMPARTMENT 2

ECRB (extensor carpi radialis brevis)

ECRL (extensor carpis radialis longus)

COMPARTMENT 3 

EPL (extensor pollicis longus)

COMPARTMENT 4 

EDC (extensor digitorum communis)

EI (extensor indicis)

COMPARTMENT 5

EDM (extensor digiti minimi)

COMPARTMENT 6

ECU (extensor carpi ulnaris)

* Extensor indices is medial to digitorum 

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FLEXOR RETINACULUM 

Attachments 

Medially - pisiform & hook of hamate 

Laterally - tubercles of scaphoid bone & crest of trapezium 

Superiorly - Deep fascia of forearm 

Inferiorly - Central portion of palmar fascia 

Structures passing superficially to flexor retinaculum:

Ulnar nerve 

Ulnar vessels 

Palmar cutaneous branch of ulnar nerve 

Palmar cutaneous branch of median nerve 

Tendon of palmaris longus 

Structures passing deep to flexor retinaculum (CARPAL TUNNEL):

Flexor digitorum superficialis tendons 

Flexor digitorum profundus tendons 

Unlar bursa enclosing flexor digitorum superficialis & profundus tendons

Flexor pollicis longus tendon 

Radial bursa enclosing flexor pollicis longus tendon 

Flexor carpi radialis tendon & its synovial sheath (special canal)

Median nerve 

Palmaris longus muscle is cut in carpal tunnel release