ANATOMY OF THE HAND

BONES OF HAND

Total of 27 bones in hand and wrist.

These are grouped into carpals, metacarpals, and phalanges.

CARPAL BONES

All carpal bones participate in wrist functionexcept 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.

METACARPALS

The hand contains 5 metacarpals. 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.

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

joints .

COMPARTMENTS OF THE HAND

11 separate Osteofascial compartments: •DORSAL INTEROSSEI (4 COMPARTMENTS)•PALMAR INTEROSSEI (4 COMPARTMENTS)•ADDUCTOR POLLICIS•THENAR•HYPOTHENAR 

         

EXTRINSIC MUSCLES OF HAND

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:•Extensor carpi radialis brevis (ECRB) •Extensor carpi radialis longus (ECRL) •Extensor carpi ulnaris (ECU)

EXTRINSIC EXTENSORS

At the digits, extension occurs due to:•The Extensor digitorum communis •Extensor indicis proprius•Extensor digiti minimi

EXTENSOR CARPI RADIALIS BREVIS

The extensors of the wrist are on the Dorsal side of the forearmA majority of the wrist extensors begin at the lateral epicondyle of humerus

:Extensor Carpi Radialis Brevis Origin: Lateral epicondyle of humerus

Insertion: Base of 3rd metacarpal

Action: Extends and radially deviates the wrist

Innervation: radial nerve (C7 and C8)

EXTENSOR CARPI RADIALIS LONGUS

Origin Lateral supracondylar ridge of humerus Insertion Base of 2nd metacarpal Action Extends and radially deviates at the wristInnervation Radial nerve (C6 and C7)

EXTENSOR CARPI ULNARIS

Origin Lateral epicondyle of humerusInsertion Base of 5th metacarpal Action Extends and ulnar deviates hand at wrist joint Innervation - Radial nerve

EXTENSOR DIGITORUM

Origin Lateral epicondyle of humerus Insertion Extensor expansions of medial four digits Action Extends the four digits and the wrist Innervation Posterior interosseous nerve

EXTENSOR DIGITI MINIMI

Origin Lateral epicondyle of humerus

Insertion 5th digit

Action Extends 5th digit at metacarpophalangeal and interphalangeal joints

Innervation Posterior interosseous nerve

EXTENSOR INDICIS

Origin: Posterior sufrace of ulna and interosseous membrane Insertion: Extensor expansion of 2nd digit Action: Extends 2nd digit and helps to extend hand Innervation : Posterior interosseous nerve

EXTRINSIC EXTENSORS

Extension at the thumb is brought about by:•The Abductor pollicis longus•Extensor pollicis brevis•Extensor pollicis longus

EXTENSOR POLLICIS BREVIS

Origin : Posterior surface of radius and interosseous membrane Insertion : Base of proximal phalanx of thumb Action : Extends proximal phalanx of thumb at carpometacarpal joint Innervation: Posterior interosseous nerve

EXTENSOR POLLICIS LONGUS

Origin : Posterior surface of middle 1/3 of ulnaInsertion : Base of distal phalanx of thumb Action: Extends distal phalanx of thumb at carpometacarpal and interphalangeal joints Innervation: Posterior interosseous nerve

ABDUCTOR POLLICIS LONGUS

Origin Posterior surfaces of ulna, Insertion Base of 1st metacarpal Action Abducts thumb Innervation the radial nerve

EXTRINSIC FLEXORS

The muscles that flex the wrist are on the palmer side.

A group of them begin at the medial epicondyle of the humerus at the elbow

EXTRINSIC FLEXORS

3 wrist flexors A larger group of thumb and digit flexorsAre innervated by the median nerveExcept for the FCU, and the FDP to the small and ring finger, which are innervated by the ulnar nerve.

EXTRINSIC FLEXORS

The main Flexors at the wrist joint are:

•The Flexor carpi radialis

•The Flexor carpi ulnaris

•The Palmaris longus

PALMARIS LONGUS

Origin Medial epicondyle of humerus

Insertion Distal half of flexor retinaculum and palmar aponeurosis

Action Flexes hand at the wrist

Innervation Median nerve (C7 and C8)

FLEXOR CARPI RADIALIS

Origin Medial epicondyle of humerus Insertion Base of 2nd metacarpal Action Flexes and radial deviates the hand (at wrist) Innervation Median nerve (C6 and C7)

FLEXOR CARPI ULNARIS

Origin medial epicondyle of humerusInsertion Pisiform bone, hook of hamate bone, and 5th metacarpal boneAction Flexes and ulnar deviates hand (at wrist)Innervation Ulnar nerve (C7 and C8)

FLEXOR DIGITORUM SUPERFICIALIS

Origin medial epicondyle of humerus Insertion middle phalanges of digits 2 - 5 Action Flexes middle phalanges at proximal inter phalangeal joints also flexes proximal phalanges at metacarpo phalangeal joints and hand Innervation Median nerve (C7, C8 and T1)

FLEXOR DIGITORUM PROFUNDUS

Origin Proximal 3/4 of ulnaInsertion Base of the distal phalanx of digits 2 – 5Action Flexes distal phalanges at distal interphalangeal joints Innervation Medial part: ulnar nerveLateral part: median nerve

 FLEXOR POLLICIS LONGUS

Origin Anterior surface of radius and adjacent interosseous membrane Insertion Base of distal phalanx of thumb Action Flexes phalanges of 1st digit (thumb) Innervation Anterior interosseous nerve from median nerve (C8 and T1)

PRONATOR QUADRATES

Origin Distal 1/4 of anterior surface of ulna Insertion Distal 1/4 of anterior surface of radius Action Pronates forearm; Innervation median nerve

PRONATOR TERES

Origin Medial epicondyle of humerusInsertion Middle of lateral surface of radius Action PronatesInnervation Median nerve (C6 and C7)

INTRINSIC MUSCLES OF HAND

Situated totally within the handDivided into 4 groups:- •Thenar•Hypothenar•Lumbricals•Interossei muscles

THE THENAR GROUP

The Thenar group consists of: •The Abductor pollicis brevis •Flexor pollicis brevis•Opponens pollicis•Adductor pollicis muscles

ABDUCTOR POLLICIS BREVIS

Origin Scaphoid and Trapezium Insertion Lateral side of base of proximal phalanx of thumb Action Abducts thumbInnervation median nerve (C8 and T1)

FLEXOR POLLICIS BREVIS

Origin Flexor retinaculum and tubercles of scaphoid and trapezium Insertion Lateral side of base of proximal phalanx of thumb Action Flexes thumb Innervation Recurrent branch of median nerve (C8 and T1)

OPPONENS POLLICIS

Origin Flexor retinaculum and tubercles of scaphoid and trapezium Insertion Lateral side of 1st metacarpal Action Draws 1st metacarpal laterally to oppose thumb toward center of palmInnervation Recurrent branch of median nerve (C8 and T1)

ADDUCTOR POLLICIS

It has 2 heads that are separated by a gap through which the radial artery passesOrigin: Oblique head – bases of 2nd and 3rd metacarpals, capitate and adjacent carpal bones

Transverse head – anterior surface of body of 3rd metacarpal boneInsertion: medial side of base of proximal phalanx of thumbInnervation: ulnar nerveAction: adducts thumb towards middle digit

THE HYPOTHENAR GROUP

Hypothenar muscles

1 .Opponens Digiti Minimi

2.Abductor Digiti Minimi

3.Flexor Digiti Minimi Brevis

4.Palmaris Brevis

OPPONENS DIGITI MINIMI

Origin Hook of hamate and flexor retinaculum Insertion Medial border of 5th metacarpal Action Brings little finger (5th digit) into opposition with thumb Innervation Deep branch of ulnar nerve (C8 and T1)

ABDUCTOR DIGITI MINIMI

The most superficial of the hypothenar muscles forming the hypothenar eminenceOrigin: Pisiform boneInsertion: Medial side of base of proximal phalanx of 5th digitAction: Abducts 5th digit

FLEXOR DIGITI MINIMI BREVIS

Origin Hook of hamate and flexor retinaculum Insertion Medial side of base of proximal phalanx of little finger Action Flexes proximal phalanx of little (5th) finger Innervation ulnar nerve

PALMAR BREVIS

It lies in the fascia deep to the skin of the hypo thenar eminenceA relatively unimportant muscle except that it covers and protects the ulnar nerve and arteryOrigin: Flexor retinaculum and palmar aponeurosisInsertion: Skin on the medial side of the palmAction: Wrinkles the skin on the medial side of the palm and deepens the hollow of the palm, as in cupping of the hand, thereby aiding the grip

INTEROSSEI MUSCLESInterosseous MusclesThey are located between the metacarpal bonesArranged in 2 layers: 4 Palmar and 4 DorsalLocated between bones1. Dorsal interossei 1 to 4Origin: Adjacent sides of 2 metacarpal bonesInsertion: Extensor expansion's and bases of proximal phalanges of digit 2 to 4Action: Abducts digits and assist lumbricals2. Palmar interossei 1 to 4Origin: Palmar surfaces of 2nd, 3th , 4th and 5th metacarpal bonesInsertion: Extensor expansion of digits and bases of proximal phalanges of digits 2, 4, and 5Action: Adducts digits and assist lumbricals

LUMBRICAL MUSCLES

They are named as such because of their elongated wormlike form

1. Lumbricals 1 and 2 Origin: lateral 2 tendons of flexor digitorum profundus

2. Lumbricals 3 and 4Origin: medial 3 tendons of flexor digitorum profundus

Insertion: lateral sides of extensor expansions of digits 2 to 5Action: To flex digits at MCP joints and extend IP joints

THE PULLEY SYSTEM

The pulley system is critical to flexion of the finger.The retinacular system for each of the fingers contains 5 annular pulleys and 4 cruciform 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..

THE PULLEY SYSTEM OF THE THUMBPULLEY SYSTEM OF THE THUMB

ARTERIES

Radial and ulnar arteries and their branches provide all the blood to the hand

A. Radial ArterySmaller of the 2 terminal branches of the brachial artery1. superficial palmar branch superficial palmar arterial arch2. princeps pollicis artery – supplies the thumb3. radialis indicis – supplies lateral side of digit 2

4. deep palmar arterial arch – formed mainly by the radial artery which joins the deep branch of the ulnar arterypalmar metacarpal arteries – arise from the deep palmar arch, run distally and join the common palmar digital arteries which arise from the superficial palmar arterial arch

DORSAL ARTERY OF HAND

Dorsal carpal branch of ulna and radius

Dorsal carpal arch

Dorsal metacarpal artery

Dorsal digital artery

Middle & distal phalanges Palmar proper digital

arteries

ARTERIES

B. Ulnar Artery

Enters the palm on the lateral side of the ulnar nerve superficial to the flexor retinaculum - passes lateral to the pisiform bone

1. deep palmar branch deep palmar arterial arch, passes deep through the hypothenar muscles and anastomoses with the radial artery2. superficial palmar arterial arch

- formed mainly by the ulnar artery- located distal to the deep palmar arch- gives rise to the three common digital arteries that

anastomoses with the palmar metacarpal arteries from the deep palmar arch

each common digital artery divides into a pair of proper palmar digital arteries which run along the sides of the 2nd to 4th digits

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.

ULNAR NERVE1 .Ulnar (C(7)8-T1): through Guyon's canal, past

hook of hamateSensory: Medial palm & 1 1/2 digits via: palmar,

palmar digital branches  Medial dorsal hand & 1 1/2 digits via:

dorsal, dorsal digital, & proper digital branches

  Nerve divides at hypothenar eminenceMotor: Superficial Branch @[lateral to pisiform]

  Palmaris brevis  Deep (Motor) Branch [around hook of

hamate]  Adductor pollicis  THENAR MUSCLES  Flexor pollicis brevis [FPB] [with median]  HYPOTHENAR MUSCLES  Abductor digiti minimi [ADM]  Flexor digiti minimi brevis[FDMB]  Opponens digiti minimi [ODM]  INTRINSIC MUSCLES  Dorsal interossei [DIO] [abduct DAB]  Volar interossei [VIO] [adduct PAD]  Lumbricals [medial two (3,4)]

MEDIAN NERVE

Median (C(5)6-T1) : runs through carpal tunnel, then cutaneous branches off at (risk in Carpal Tunnel release)Sensory: Palmar Cutaneous Branch

  Dorsal distal phalanges of 3 1/2 digits: via proper palmar digital branches

  Volar wrist capsule  Volar 3 1/2 digits and lateral palm: via palmar

& palmar digital branches (multiple variations of thumb sensory innervation)

Motor: Motor Recurrent (Thenar motor) Branch: Usually branches off median before carpal tunnel

  THENAR  Abductor pollicis brevis [APB]  Opponens pollicis  Flexor pollicis brevis [FPB]  <l>(Joint innervation with ulnar nerve)</l>  INTRINSIC  Lumbricals [lateral two (1,2)]

RADIAL NERVE

Radial (C5-T1):

 

Sensory: Dorsal 3 1/2 digits and hand: via superficial branch (dorsal digit branches)

  Dorsal wrist capsuleotor: NONE (in hand)

FLEXOR ZONE OF HAND ZONE BOUNDARIES COMMENT

I FDS insertion to distal tip

Injuries amenable to repair (e.g. Jersey finger)

II Midpalm fibroosseous tunnel to FDS insertion

Called “No man's land” because high rate of complications.

III Transverse Carpal ligament to fibro-osseous tunnel

Injuries often associated with Median nerve or arterial arch injuries. Explore and repair all.

IV Transverse carpal ligament (carpal tunnel)

Uncommon site of injury. Repair usually requires carpal tunnel release and repair. Median nerve at risk.

V Proximal to the TCL Injuries require end-to-end repair

Thumb I Thumb IP to distal tip

Similar to finger

Thumb II Thumb CMC to IP Similar to fingerThumb III Thenar eminence Repair may require lengthening or

graft procedure

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