WRIST AND HAND ANATOMY
BONY ANATOMY
- Three main groups of bones constitute the skeleton of the hand.
- From proximal to distal, these include the carpal bones, metacarpal
bones, and the phalanges .
- Additionally, the hand also contains some small bony structures
termed sesamoid bones.
Carpal bones
- The hand contains 8 carpal bones made up of 2 rows of 4 bones
each.
- From lateral to medial, the proximal row consists of the scaphoid,
lunate, triquetrum, and pisiform bones. In the same order, the distal
row consists of the trapezium, trapezoid, capitate, and hamate bones.
- The anterolateral margins of the scaphoid and trapezium elevate and
protrude forward to make an attachment site for the flexor
retinaculum.
- The hamate bone has a bony hook volarly, and the pisiform stands
on the triquetrum; thus, these 2 protrusions provide the medial
attachment side for the flexor retinaculum.
- The distal row of the carpal bones joins to the metacarpal bones to
form the carpometacarpal joint. The carpus is cartilaginous at
birth.
- The capitate begins to ossify during the first year, and the others
begin to ossify at intervals thereafter until the 12th year, when
all bones are ossified.
Metacarpal bones
- The hand has 5 metacarpal bones.
- From proximal to distal, each has a base, a shaft, and a head.
- The first metacarpal bone constitutes the skeleton of the thumb
and is the shortest and most mobile. It is in contact with the
trapezium proximally.
- The other 4 metacarpals contact with the trapezoid, capitate and
hamate, and lateral-medial surfaces of metacarpal bones. The heads
of the metacarpal bones, which form the knuckles, articulate with
the proximal phalanges.
- The shaft of each metacarpal bone is slightly concave forward
and is triangular in transverse section, with medial, lateral, and
posterior surfaces.
Phalanges
- The hand has 14 phalanges.
- Each finger contains 3 phalanges, but each thumb only has 2.
- The hand contains some complex joints, including, from proximal
to distal order, the radiocarpal, intercarpal, carpometacarpal,
MCP, and interphalangeal joints.
top
|
home
|
back
|
MUSCLES OF THE WRIST AND HAND
- The hand is multitalented - it can perform powerful grasping tasks
as well as delicate ones.
- The large, forceful muscles for the former have their proximal
attachments in the arm and forearm in order to achieve the desired
angle of pull.
- They attach to appropriate parts of the hand and wrist by means of
long tendons, but their muscle bellies and origins are far from the
hand - hence the designation "extrinsic".
- Intrinsic muscles are small and are entirely confined to the
region distal to the long bones of the forearm.
- Keeping track of all these muscles is made simpler by grouping
them according to where they are, what they do, or both.
- The forearm has the convenient dividing line of its 2 long bones
(radius and ulna) and the strong interosseous membrane that
connects them.
- The muscles on the volar side are said to lie in the anterior
compartment, and generally flex or pronate the hand. They can be
envisioned as being in 3 groups- superficial, middle, and deep.
- Muscles on the dorsal side of the interosseous membrane are said
to lie in the posterior compartment, and generally extend or
supinate the hand.
- They can be further subdivided according to their actions (acting on
the wrist joint, fingers, or thumb).
- The intrinsic muscles can be grouped according to the digit they
move.
- Thenar muscles affect the thumb, hypothenar muscles the 5th or
little finger, and "short finger muscles" affect mostly digits 2-5
(index finger- little finger).
·Anterior compartment (flexor-pronator group)
1. Superficial
2. Middle
3. Deep
· Posterior compartment (extensor-supinator group)
4. Wrist-level hand motion
5. Finger motion
6. Thumb motion
Intrinsic muscles
1. thenar group
2. Hypothenar group
3. Short finger muscles
Superficial muscles of the anterior compartment
1. PRONATOR TERES
ORIGIN: Humeral head: medial epicondyle, medial supracondylar
ridge and medial intermuscular septum. Ulnar head: medial
border of coronoid process
INSERTION: Just posterior to most prominent part of lateral
convexity of radius
ACTION: Pronates forearm and flexes elbow
NERVE: Median nerve (C6,7) (from lateral and medial cords)
2. FLEXOR CARPI RADIALIS
ORIGIN: Common flexor origin of medial epicondyle of humerus
INSERTION: Bases of 2nd and 3rd metacarpals via groove in
trapezium and slip to scaphoid
ACTION: Flexes and abducts wrist
NERVE: Median nerve (C6, 7) (from medial and lateral cords)
3. PALMARIS LONGUS
ORIGIN: Common flexor origin of medial epicondyle of humerus
INSERTION: Flexor retinaculum and palmar aponeurosis
ACTION: Flexes wrist and tenses palmar aponeurosis
NERVE: Median nerve (C7, 8) (from medial and lateral cords)
4. FLEXOR CARPI ULNARIS
ORIGIN: Humeral head: common flexor origin of medial epicondyle.
Ulnar head: aponeurosis from medial olecranon and upper
three quarters subcutaneous border of ulna
INSERTION: Pisiform, hook of hamate, base of 5th metacarpal via
pisohamate and pisometacarpal ligaments
ACTION: Flexes and adducts wrist. Fixes pisiform during action
of hypothenar muscles
NERVE: Ulnar nerve (C6, 7) (by communication from lateral cord)
middle muscle of anterior compartment
1.FLEXOR DIGITORUM SUPERFICIALIS
ORIGIN: Humeral head: common flexor origin of medial epicondyle
humerus, medial ligament of elbow. Ulnar head: medial border
of coronoid process and fibrous arch. Radial head: whole
length of anterior oblique line
INSERTION: Tendons split to insert onto sides of middle phalanges
of medial four fingers
ACTION: Flexes proximal interphalangeal joints and secondarily
metacarpophalangeal joints and wrist
NERVE: Median nerve (C7, 8) (from medial and lateral cords)
Deep 3 muscles of the anterior compartment
1. FLEXOR POLLICIS LONGUS
ORIGIN: Anterior surface of radius below anterior oblique line
and adjacent interosseous membrane
INSERTION: Base of distal phalanx of thumb
ACTION: Flexes distal phalanx of thumb
NERVE: Anterior interosseous nerve (C7, 8)
2. FLEXOR DIGITORUM PROFUNDUS
ORIGIN: Medial olecranon, upper three quarters of anterior and
medial surface of ulna as far round as subcutaneous border and
narrow strip of interosseous membrane
INSERTION: Distal phalanges of medial four fingers. Tendon to
index finger separates early
ACTION: Flexes distal interphalangeal joints, then secondarily
flexes proximal interphalangeal and metacarpophalangeal joints
and wrist
NERVE: Median nerve (anterior interosseous) (C6, 7) / ulnar
nerve (C7, 8)
3. PRONATOR QUADRATUS
ORIGIN: Lower quarter of anteromedial shaft of ulna
INSERTION: Lower quarter of anterolateral shaft of radius and
some interosseous membrane
ACTION: Pronates forearm and maintains ulna and radius opposed
NERVE: Anterior interosseous nerve (C8)
Muscles of the posterior compartment that act
on the hand at the wrist joint
1. EXTENSOR CARPI RADIALIS LONGUS
ORIGIN: Lower third of lateral supracondylar ridge of humerus
and lateral intermuscular septum
INSERTION: Posterior base of 2nd metacarpal
ACTION: Extends and abducts hand at wrist
NERVE:Radial nerve (C6, 7)
2. EXTENSOR CARPI RADIALIS BREVIS
ORIGIN: Common extensor origin on anterior aspect of lateral
epicondyle of humerus
INSERTION: Posterior base of 3rd metacarpal
ACTION: Extends and abducts hand at wrist
NERVE: Posterior interosseous nerve (C7, 8)
3. EXTENSOR CARPI ULNARIS
ORIGIN: Common extensor origin on anterior aspect of lateral
epicondyle of humerus
INSERTION: Base of 5th metacarpal via groove by ulnar styloid
ACTION: Extends and adducts hand at wrist
NERVE: Posterior interosseous
Muscles of the posterior compartment that act on the fingers (digits 2-5)
1. EXTENSOR DIGITORUM
ORIGIN: Common extensor origin on anterior aspect of lateral
epicondyle of humerus
INSERTION: External expansion to middle and distal phalanges
by four tendons. Tendons 3 and 4 usually fuse and little finger
just receives a slip
ACTION: Extends all joints of fingers
NERVE: Posterior interosseous nerve (C7, 8)
2. EXTENSOR INDICIS
ORIGIN: Lower posterior shaft of ulna (below extensor pollicis
longus) and adjacent interosseous membrane
INSERTION: Extensor expansion of index finger (tendon lies on
ulnar side of extensor digitorum tendon)
ACTIONExtends all joints of index finger
NERVEPosterior interosseous nerve (C7, 8)
3. EXTENSOR DIGITI MINIMI
ORIGIN: Common extensor origin on anterior aspect of lateral
epicondyle of humerus
INSERTION: Extensor expansion of little finger-usually two tendons
which are joined by a slip from extensor digitorum at
metacarpophalangeal joint
ACTION: Extends all joints of little finger
NERVE: Posterior interosseous nerve (C7, 8)
Muscles of the posterior compartment that act on the thumb
(digit 1)
1. ABDUCTOR POLLICIS LONGUS
ORIGIN: Upper posterior surface of ulna and middle third of
posterior surface of radius and interosseous membrane
between
INSERTION: Over tendons of radial extensors and brachioradialis
to base of 1st metacarpal and trapezium
ACTION: Abducts and extends thumb at carpometacarpal joint
NERVE: Posterior interosseous nerve (C6, 7)
2. EXTENSOR POLLICIS BREVIS
ORIGIN: Lower third of posterior shaft of radius and adjacent
interosseous membrane
INSERTION: Over tendons of radial extensors and brachioradialis
to base of proximal phalanx of thumb
ACTION: Extends metacarpophalangeal joint of thumb
NERVE: Posterior interosseous nerve (C7, 8)
3. EXTENSOR POLLICIS LONGUS
ORIGIN: Middle third of posterior ulna (below abductor pollicis
longus) and adjacent interosseous membrane
INSERTION: Base of distal phalanx of thumb via Lister's tubercle
(dorsal tubercle of radius).
ACTION: Extends interphalangeal and metacarpophalangeal joints
of thumb
NERVE: Posterior interosseous nerve (C7 , 8 )
Intrinsic muscles of the hand - thenar group
1. OPPONEN POLLICIS
ORIGIN: Flexor retinaculum and tubercle of trapezium
INSERTION: Whole of radial border of 1st metacarpal
ACTION: Opposes (medially rotates and flexes ) carpometacarpal
and metacarpophalangeal joints of thumb
NERVE: Recurrent (muscular) branch of median nerve (C8,T1)
( may also be from deep branch of ulnar nerve (T1))
2. ABDUCTOR POLLICIS BREVIS
ORIGIN: Tubercle of scaphoid & flexor retinaculum
INSERTION: Radial sesamoid of proximal phalanx of thumb &
tendon of extensor pollicis longus
ACTION: Abducts thumb at metacarpophalangeal &
carpometacarpal joints
NERVE: Recurrent (muscular) branch of median nerve(C8, T1)
occasionally by ulnar nerve
3. FLEXOR POLLICIS BREVIS
ORIGIN: Flexor retinaculum and tubercle of trapezium
INSERTION: Base of proximal phalanx of thumb (via radial
sesamoid)
ACTION: Flexes metacarpophalangeal joint of thumb
NERVE: Recurrent (muscular) branch of median nerve (C8, T1)
(may also be from deep branch of ulnar nerve (T1))
4. ADDUCTOR POLLICIS
ORIGIN: Oblique head: base of 2nd and 3rd metacarpals, trapezoid
and capitate. Transverse head: palmar border and shaft of 3rd
metacarpal
INSERTION: Ulnar sesamoid then ulnar side of base of proximal
phalanx and tendon of extensor pollicis longus
ACTION: Adducts carpometacarpal joint of thumb
NERVE: Deep branch of ulnar nerve (T1)
Intrinsic muscles of the hand - hypothenar group
1. ABDUCTOR DIGITI MINIMI (hand)
ORIGIN: Pisiform bone, pisohamate ligament and flexor retinaculum
INSERTION: Ulnar side of base of proximal phalanx of little
finger and extensor expansion
ACTION: Abducts little finger at metacarpophalangeal joint
NERVE: Deep branch of ulnar nerve (C8, T1)
2. FLEXOR DIGITI MINIMI BREVIS
ORIGIN: Flexor retinaculum and hook of hamate
INSERTION: Ulnar side of base of proximal phalanx of little
finger
ACTION: Flexes metacarpophalangeal joint of little finger
NERVE: Deep branch of ulnar nerve (C8, T1)
3. OPPONEN DIGITI MINIMI HAND
ORIGIN: Flexor retinaculum and hook of hamate
INSERTION: Ulnar border of shaft of 5th metacarpal
ACTION: Opposes (flexes and laterally rotates) carpometacarpal
and metacarpophalangeal joints of little finger
NERVE: Deep branch of ulnar nerve (C8, T1)
Intrinsic muscles of the hand — short finger muscles
1. LUMBRICALS
ORIGIN: Four tendons of flexor digitorum profundus.
Radial 2: radial side only (unipennate).
Ulnar 2: cleft between tendons ( bipennate)
INSERTION: Extensor expansion (dorsum of proximal phalanx )
of fingers 2-5 radial side
ACTION: Flex metacarpophalangeal joints and extend
interphalangeal joints of fingers
NERVE: Lateral 2: median nerve (C8, T1). medial 2: deep branch
of ulnar nerve (C8, T1)
2. DORSAL INTEROSSEI
ORIGIN: Bipennate from inner aspects of shafts of all metacarpals
INSERTION: Proximal phalanges and dorsal extensor expansion
on radial side of index and middle fingers and ulnar side of
middle and ring fingers
ACTION: Abduct from axis of middle finger. Flex
metacarpophalangeal joint while extending interphalangeal
joints
NERVE: Deep branch of ulnar nerve (T1)
3. PALMAR INTEROSSEI
ORIGIN: Anteriorshafts of 1, 2, 4, 5 metacarpals (unipennate)
INSERTION: Proximal phalanges and dorsal extensor expansion
on ulnar side of index and radial side of ring and little
fingers and to ulnar sesamoid of thumb
ACTION: Adduct to axis of middle finger. Flex
metacarpophalangeal joint while extending interphalangeal
joints
NERVE: Deep branch of ulnar nerve (T1)
top
|
home
|
back
|
JOINTS AND LIGAMENTS OF THE HAND
Radiocarpal joint
- This joint constitutes the distal articular surfaces of the radius
and the scaphoid, lunate, and triquetral bones.
- An articular disk is present between the distal and proximal
osteal structures.
- The proximal articular surface has a shallow depression, and the
distal articular surface has a fitting protrusion.
- The type of joint is synovial spheroid.
- The capsule of the joint encloses it and includes the articular
cartilaginous structures.
- Radial and ulnar collateral ligaments strengthen both sides of the
joint.
- Palmar and dorsal radiocarpal ligaments cover the back and
front of the wrist joint.
- The anterior interosseous nerve and a deep branch of the radial
nerve innervate it.
- The main movements of the wrist joint are flexion, extension,
abduction, and adduction.
- They can move in circumduction when a combination of these
movements is used.
Intercarpal joints
- An intercarpal joint occurs between the distal and proximal row of
the carpal bones and between every individual carpal bone.
- It is a synovial and plane-type joint.
- The articular capsule surrounds these structures.
Carpometacarpal joints
- An intercarpal joint occurs between the distal and proximal row
of the carpal bones and between every individual carpal bone.
- It is a synovial and plane-type joint.
- The articular capsule surrounds these structures.
Metacarpophalangeal joints
- The 5 MCP joints are located between the head of the metacarpal
bones and the base of the proximal phalanges.
- They are synovial condyloid joints surrounded by a synovial
capsule.
- The capsule is pliable in the front and back and rigid on the sides.
- MCP joints can flex, extend, abduct, and adduct.
- Using a combination of these movements, they can move in
restricted circumduction.
- Strong and tight palmar and collateral ligaments support the joints
volarly, radially, and ulnarly.
- Additionally, the deep transverse metacarpal ligaments connect
the medial 4 joints to each other and hold the head of the
metacarpal bones together.
Interphalangeal joints
- These are located between the phalanges and are synovial hinge
joints.
- Palmar and collateral ligaments support the joints in the front and
sides.
- Interphalangeal joints can be flexed or extended
top
|
home
|
back
|