Anatomy of the hand

ANATOMY OF THE HAND

BY

Dr. J . M . Hassanain

Hand function is an important feature in humans over other primates who lack fine control and precision

EMBRYOLOGY OF THE UPPER LIMB

Limb buds first appear as small elevations on ventro lateral body end of fourth week.

Each limb bud :

Mesenchyme derived from somatic mesoderm which is covered by a layer of ectoderm

Distal end of bud form flipper like limbs.

Later bones develop and myoblast aggregate to develop muscle mass .

Upper limb rotates laterally 90 degrees

Specific dermatone ( which is skin area supplied by a single spinal nerve )

ANATOMY

Bony skeleton Muscles and soft tissues Vessels and nerves

BONY SKELETON

Wrist joint composed of multiple carpal bone articulating with the radius proximally and five metacarpals distally

Proximal row of carpal bone (radial to ulnar)

scafoid , lunate , traquetral , pisiform

Distal rowtrapezium , trapazoid , capitate ,

hamate

BONES OF THE HAND

5 Metacarpals Thumb is no. 1 Little finger is no. 5

PHALANGES

All fingers have 3 phalanges proximal

middle

distal Except thumb has 2

proximal distal

Most of tendon in the hand originate in muscles arising from the forearm

Flexor on volar aspect of forearm must arise from common flexor tendor (medial epicondyle )

Extensors on dorsal aspect of the forearm arise from common extensor tender on lateral epicondyl

In the hand ulnar side hypo thenar muscles acting on the little fingers:

Abductor digitiminimi Flexor digitiminimi brevis Opponens digitiminimi

Radial side thenar muscle acting on the thumb

Flexor, adductor pollices Abductor pollices brevis Opponen pollices brevis

Long flexors fl. digitorum

superficialus fl. digitorum profundus

Act on all the fingers

Intrinsic

Lumbrical Dorsal Ventral interrosies

Vascular Supply of Hand

Radial artery : Superficial palmer branch superficial palmer

arch ,which arises above the wrist Common palmer digital Deep palmer branches Deep palmer arch palmer metacarpal arteries

which joins the common digital Ulnar artery superficial palmer branch joins on

side of pisiform of superficial palmer branch

VENOUS DRAINAGE OF HAND

Via : Dorsal digital vein dorsal venous arch

Basillic vein in front of forearm

Peripheral nerve entrapment

There is a disproportion between volume of the peripheral nerve and space within the extremity through which it passes

Applied Anatomy of Ulnar Nerve

Arises directly from the medial cord of brachial plexus (C8-T1)

Lies between axillary artery laterally and axillary vein medially

At inferior border of subscapularis muscle nerve receives fiber of C7 ( lat. root of ulnar nerve )

Descend in arm post. to pectoralis major muscle ( posterio medial to brachial artery)

8 cm above medial epicondyl with branch of superior ulnar collateral artery diverge medially from brachial artery to pierce medial intramuscular septum

Together descend on medial head of triceps

Nerve passes in ulner groove dorsal aspect of medial epicondyl

It innervates fl. carpi ulnaris 0.5-1 cm above medial epicondyl

Potential points of compression in the arm

Ulnar nerve fibers ( medial cord ) 1st rib as nerve passes between rib & clavicle

8 cm proximal to medial condyl as nerve pierce intramuscular septum ( arcade of Struther )

Hypertrophy of medial head of triceps may force nerve anteriorly, as triceps contract, nerve get compressed

Ulnar Nerve at Elbow &Forearm

In cubital fossa ulnar nerve passes through fibro-osseous tunnel

As it leaves the canal it lies between the flexor corpi ulnanis and flexor digitorum profundus till middle of forearm

In distal 1/3 lies just radial to the flexor corpi ulnaris

Straight line drawn from medial epicondyl to radial margin of pisiform marks the line of the nerve

Supply of ulnar nerve in forearm

Muscular branch to fl. Digitorum profundus ( i.e. ulner ½ ) 3 cm distal to medial epicondyl

Palmer cutanous branch Dorsal cutanous branch

Ulnar nerve enters hand

From under fl corpi ulnaris muscle , nerve and artery

Radial to pisiform , superficial to transverse carpel lig. and dorsal to superficial palmer lig.

Ulnar nerve divide to : deep terminal branch superficial palmer branch

Muscle supplied by ulnar nerve

Flexor corpi ulnaris Flexor digitorum profundus ( medial 2

tendons ) Flexor digiti minimi 2 ,3 ,4th web space interossei 3rd & 4th lumbricle Adductor pollicis 1st dorsal interosseous

Sensory Supply of Ulnar Nerve Dorsal cutanous branch of

ulnar : skin dorsoulnar side of hand , little finger and ulnar ½ of index finger

Medial cutanous nerve of forearm : C8-T1 skin over biceps elbow crease middle 1/3 of arm palmer skin down to forearm

Anatomical Sites of Compression

Points in elbow and forearm Anconeus epitrochlearis muscle Fibrous arcade between 2 heads of

fl. carpi ulnaris

Site of compression in hand &wrist

Palmaris brevus muscle Fibrous origin of fl digitiminmi Ulnar artery aneurysm or

thrombosis Distal ulnar tunnel ganglia

MEDIAN NERVE

Arises from lateral & medial cords of brachial plexus

Contain fibers C5 –T1 Forms antrolat to 3rd portion of axillary

artery in upper 1/3 of arm

In the arm it descends post. to pectoralis major muscle, lateral to brachial artery, antromedial to brachialis muscle, posteromedial to biceps

In mid portion of arm, median nerve crosses ant to brachial artery to lie on its medial side to enter the cubital fosse

The nerve enters forearm between humeral and ulnar head of pronater teres

Then runs between fl digitorum superficialis and fl digitorum profundus, later emerges 5 cm above wrist radial to tendon of palmaris longus

MEDIAN NERVE IN THE WRIST

It enters the wrist dorsal to transverse carpal lig through the carpal tunnel

Boundaries Of Carpal Tunnel

Dorsally: radio carpal lig. Radially: scaphoid & trapezium Palmorly: transverse carpal lig. Ulnary: hood of hamate & pisiform

After exiting carpal tunnel

Median nerve splits to two parts Common digital nerve to thumb Proper digital nerve to radial side of index Ulnar division of median nerve; common

digital to 2nd & 3rd web

Muscle supplied by median nerve

Forearm Pronator teres Flexor digitorum superficialis Flexor carpi radialis Palmaris longus Flexor digitorum profundus Flexor pollicis longus Pronator quadratus

HAND

Flexor pollicis brevis Abductor pollicis brevis Opponens pollicis First lumbrtical Second lumbrical

Anatomical compression points of the median nerve

ARM: Pectoralis minor muscle Anomalous axillary arch muscles Anomalous vascular arches in the axilla Deltopectoral fascia Supracondyloid process Ligament of Struthers

FOREARM

Lacertus fibrosus Pronator teres muscle Flexor digitorum superficialis arch Anomalous muscles Ulnar collateral or radial artery branches

HAND / WRIST

Carpal tunnel Palmar cutaneous branch within the

transverse retinacular ligament

RADIAL NERVE

Arises from the post cords of the brachial plexus behind 3rd part of axillary artery

Neural element of C5 – C8 Proximal 1/3 of arm nerve descends behind

brachial artery ant to subscapularis ,teres major ,latissmus dorsi muscle and long head of triceps

At junction of upper and middle 1/3 of arm deviates dorsolaterally between medial and long head of triceps lying adjacent to spiral groove of humerus

10 cm above lat humeral epicondyl lying between the brachialis and brachioradialis then lies between brachialis and extensor carpi radialis ant to tip of lat epicondyl dividing into : Superficial

Deep branches

Radial Nerve In Forearm

Superficial branch ant to supinator muscle proximal 1/3 then deep to brachioradialis

The sup branch pierces the fascia on the brachioradialis on the ulnar side of tendons 7cm above wrist

On the dorsoradial side of wrist it divides into 5 dorsal digital nerves and only one branch to extensor carpi radilalis brevus muscle

Post interosseous nerve (deep terminal branch of radial nerve ) innervates extensor muscle of wrist

It is seperated from the radium by deep head of supinator

After leaving the supinator it lies between the abductor pollies and other extensors of forearm

In distal forearm it penetrates the extensor pollies brevus to lie in the interosseous membrane

Distally it divides to give sensory innervation to the wrist

Muscles supplied by radial nerve

Triceps : long head medial head lateral head

Anconeus Brachioradialis Extensor carpi longus Extensor carpi radialis brevis

Muscles supplied by radial nerve

Extensor carpi ulnaris Extensor digitorum communis Extensor digiti minimi Abductor pollicis longus Extensor pollicis longus Extensor pollicis brevis Extensor indicis proprius

Anatomical compression points of the radial nerve

ARM: Accessory subscapularis teres latissimus Lateral head of the triceps muscle Lateral intermuscular septum

FOREARM: Posterior interosseous nerve within radial

tunnel Fibrous bands attached to radiocapitelar

joint Extensor carpi radialis brevis muscle Arcade of Frohse Fibrous bands within the supinator muscle

Superficial radial nerve Between brachioradialis muscle & radial

shaft Between brachioradialis and extensor carpi

radialis longus tendons

THANK YOU

THE END