Wrist and Hand Anatomy

Moderator: Dr. Asif Sultan

Presented by: Qazi Manaan

Overview

• The anatomy of the hand is complex, intricate, and fascinating.

• Absolutely essential for our everyday functional living.

Bone Anatomy

• Total of 27 bones in hand and wrist.

• These are grouped into carpals, metacarpals, and phalanges.

• The wrist is the most complex joint in the body. It is formed by 8 carpal bones grouped in 2 rows with very restricted motion between them.

• All carpal bones participate in wrist function

o except for the pisiform.

• The scaphoid serves as link between each row; therefore, it is vulnerable to fractures.

• The distal row of carpal bones is strongly attached to the base of the second and third metacarpals, forming a fixed unit.

• The hand contains 5 metacarpal bone.

• First Metacarpal articulates proximally with the trapezium.

• The other 4 metacarpals articulate with the trapezoid, capitate, and hamate at the base.

• The hand contains 14 phalanges.

JOINTS

•  All 4 distal carpal bones articulate with the metacarpals at the carpometacarpal (CMC) joints.

• At the metacarpophalangeal joints, lateral motion is limited by the collateral ligaments

• At the CMC joint, the volar plate is part of the joint capsule that attaches only to the proximal phalanx, allowing hyperextension.

• At the interphalangeal joints: extension is limited by the volar plate, which attaches to the phalanges at each

side of the joint. Radial and ulnar motion is restricted by

collateral ligaments.

Muscles and Tendons

• The muscles of the hand are divided into:

Intrinsic and

Extrinsic group.

Extrinsic extensors

• All extensors are extrinsic and supplied by radial nerve.

• Except for the interosseous-lumbrical complex.

•  Group contains:3 wrist extensors A larger group of thumb and digit

extensors.

• The main extensors at wrist are:

The extensor carpi radialis brevis (ECRB)

extensor carpi radialis longus (ECRL)

extensor carpi ulnaris (ECU)

• At the digits, extension occurs due to:

The extensor digitorum communis,

extensor indicis proprius, and

extensor digiti minimi

• Extension at the thumb is bought about by:

The abductor pollicis longus,

extensor pollicis brevis, and

extensor pollicis longus

Extrinsic Flexors

• 3 wrist flexors

• A larger group of thumb and digit flexors

• Innervated by the median nerve

• Except for the FCU, and the FDP to the

small and ring finger, which are

innervated by the ulnar nerve.

• The main Flexors at the wrist joint are:

The flexor carpi radialis

the flexor carpi ulnaris and

the palmaris longus

• The digital flexors include:

Flexor Digitorum Superficialis

Flexor Digitorum Profundus

Flexor Pollicis Longus

Intrinsics

• Situated totally within the hand• Divided into 4 groups: the thenar, hypothenar, lumbrical, and interossei muscles.

• The thenar group consists of:

the abductor pollicis brevis,

flexor pollicis brevis,

opponens pollicis, and

adductor pollicis muscles.

• The hypothenar group consists of:

the palmaris brevis,

abductor digiti minimi,

flexor digiti minimi, and

opponens digiti minimi.

• The lumbrical muscles contribute to

the flexion of the MCP joints and

extension of the interphalangeal joints.

• The interossei group consists of:

3 palmar and 4 dorsal muscles • All innervated by

the ulnar nerve.

Zones of the Hand

Flexor Zones

Extensor Zones

NERVES

•  3 nerves:

Median

Ulnar 

Radial

Median nerve• Crucial in the gripping mechanism by the thumb.•  It originates from the lateral and medial cords of

the brachial plexus (C5-T1).• In the forearm, the motor branches supply the

pronator teres, flexor carpi radialis, palmaris longus, and flexor digitorum superficialis muscles.

•  The anterior interosseus branch innervates the flexor pollicis longus, flexor digitorum profundus (radial part), and pronator quadratus muscles.

• Palmar cutaneous branch provides sensation at the thenar eminence. Also sensory digital branches provide sensation to the radial three and a half fingers and corresponding palm area

• As the median nerve passes through the carpal tunnel, the recurrent motor branch innervates the thenar muscles

• It also innervates the index and middle finger lumbrical muscles

Signs of a Lesion:

• Benediction Sign :

• Ape Thumb Deformity:

• Median Claw Hand:

Pen Test

Ulnar nerve• Controls fine movement of the

fingers•  It originates at the medial cord

of the brachial plexus (C8-T1)• Sensory to the: hypothenar eminenceThe palmar and dorsal ulnar

one and a half fingers

• The deep motor branch passes through the Guyon canal in company with the ulnar artery. It innervates the

hypothenar muscles all interossei, the 2 ulnar lumbricals, the adductor pollicis, and the deep head of the flexor pollicis brevis

Signs of a lesion:

• Ulnar Claw Hand:

Froment’s Sign

Egawas’ Test

Card Test

Radial nerve

• Innervates the wrist extensors.•  Originates from the posterior cord of the

brachial plexus (C6-8).•  At the elbow, motor branches innervate

the brachioradialis and extensor carpi radialis longus muscles.

• At the proximal forearm, the radial nerve divides into the superficial and deep branches.

• The deep posterior interosseous branch innervates all the muscles in the extensor compartment.

• The superficial branch provides sensation at the radial aspect of the dorsum of the hand, the dorsum of the thumb, and the dorsum of the radial three and a half digits proximal to the distal interphalangeal joints.

Signs of a lesion

• Wrist Drop

• Loss of Supination:

Blood Supply

• Complex and rich vascular network

Radial Artery

• Course

• A superficial branch arises at the level of the wrist and contributes to the superficial palmar arch.

• In the palm it gives off:Princeps pollicis artery and Radialis Indicis artery, before terminating

in the deep palmar arch.

Ulnar Artery

• It travels into the hand through the Guyon canal, where it divides into:

• the deep palmar branch and • the superficial palmar branch.

 Superficial Palmar Arch

• Lies directly deep to the palmar fascia. • It gives rise to the: volar common digital arteries and multiple branches to intrinsic muscles and

skin.

• Distally,the common digital arteries bifurcate into the proper digital arteries.

Deep Palmar Arch

• Lies at the base of the metacarpals, deep to the flexor tendons.

• From its convexity it gives off three palmar metacarpal arteries.

• Dorsally it gives off three perforating arteries.

• Recurrent branches arise from the concavity to supply the carpal bones

Dorsal Carpal Arch

• Formed by: the posterior interosseous artery and a dorsal perforating branch of the anterior

interosseous artery. • Dorsal metacarpal arteries arise from a

dorsal carpal arch

MODIFIED ALLEN TEST

Veins

• Veins generally follow the deep arterial system as venae comitantes.

• A superficial venous system also exists at the dorsum of the hand and contributes to the cephalic and basilic veins in the upper extremity.

Deep Fascia

• The Flexor Retinaculum• The Palmar Fascia• Fibrous flexor sheaths in fingers • The Extensor Retinaculum

• FLEXOR RETINACULUM

• The Palmar fascia consists of resistant fibrous tissue arranged in longitudinal, transverse, oblique, and vertical fibers.

• The transverse fibers are concentrated in the mid palm and web spaces and serve as pulleys for the flexor tendons proximal to the digital pulleys.

•The digits contain 2 fascial bands of clinical importance:

the Grayson ligament and

the Cleland ligament

Pulley

• The pulley system is critical to flexion of the finger.

• The retinacular system for each of the fingers contains 5 annular pulleys and 3 cruciate pulleys.

• The thumb has 2 annular pulleys and 1 oblique pulley.

• The system supplies mechanical advantage by maintaining the flexor tendons close to the joint's axis of motion. In doing so, the pulleys prevent bowstringing.

.

Extensor Retinaculum and the 6 compartments

Compartments of the Hand

• 10 separate osteofascial compartments:     - dorsal interossei (4 compartments)      - palmar interossei (3 compartments)      - adductor pollicis    - thenar and hypothenar 

• Typically can be released with carpal tunnel release and 2 dorsal incisions         

SKIN

• The skin of the dorsum of the hand is thin and pliable.

• It is attached to the hand's skeleton only by loose areolar tissue, where lymphatics and veins course.

• explains why edema of the hand is manifested predominantly at the dorsum.

• The skin of the palmar surface of the hand is unique

ThickGlabrousLess Pliable• This enhances skin stability for

proper grasping function.

• The skin is most firmly anchored to the deep structures at the palmar creases.

• Blood supply is through numerous small, vertical branches from the common digital vessels.

• High concentration of sensory nerve organs essential to the hand's normal function.

Thank You