THE HAND

By Dr Idorenyin Umoh
 Introduction
• The human hand is designed:
I. For grasping
II. For precise movements
III. For serving as a tactile organ
• There is a big area in the motor cortex of the
brain for muscles of the hand
• The hand has two surfaces
➢ The dorsal or back of the hand
➢ The ventral or the Palmar surface which is called
the palm
• The skin of the palm is:
➢Thick for protection of the underlying tissues
➢Immobile because of its firm attachment to
the underlying palmar aponeurosis
➢Creased. All of these characters increased the
efficiency of the grip
➢The skin is supplied by spinal nerves C6, C7,
C8, through the median and ulnar nerves.
 The palmar aponeurosis
aponeurosis. :
An aponeurosis of the palm of the hand that
consists of a superficial longitudinal layer
continuous with the tendon of the palmaris
longus and of a deeper transverse layer. —
called also palmar fascia.
The palmar aponeurosis
 The palmar aponeurosis
• The palmar aponeurosis lies immediately deep to
the subcutaneous tissue of the palm.
• It extends distally from the flexor retinaculum
and divides into four slips, one to each finger, to
be attached to the fibrous flexor sheath.
• The palmar aponeurosis is clinically important as
it can be affected by Dupuytren's contracture in
its medial part.
• In this condition the aponeurosis undergoes
fibrosis to produce flexion deformity of the
medial two fingers.
The palmar aponeurosis
The palmar aponeurosis
 Bones of the Hand

• Proximal to the hand there are 8 carpal bones.

• The radius articulates with the cashew shaped
scaphoid bone laterally and the croissant-shaped
lunate.
• The ulna articulates with the pyramid-shaped
triquetrum via a pad of triangular fibrocartilage.
• The trapezium articulates with the first
metacarpal (hence ‘trapezium with the thumb’),
next to which lies the trapezoid.
 Bones of the Hand
• The capitate connects to the middle
metacarpal and the hamate (which has a
hook on its palmar surface) articulates with
the remaining two metacarpals on the ulnar
side.
• The pisiform is a pea-shaped sesamoid bone
that sits on the triquetrum and lies within the
tendon of flexor carpi ulnaris.
Bones of the Hand
 Bones of the Hand
• The metacarpals articulate with the proximal
phalanges, which articulate with the middle
phalanges, which finally articulate with the
distal phalanges.
• The thumb has only a proximal and distal
phalanx.
➢ It opposes the tips of the other fingers and is
essential for precision grip.
diagram
 Bones of the Hand
• The wrist links the hand to the arm.
• The wrist is a complex mechanical system of 8 small bones known
as the carpal bones.
• The carpal bones are arranged in 2 interrelated rows. One row
connects with the ends of the bones in the forearm—radius and
ulna.
• If you hold your hand in the thumbs-up position, the bone on the
top of your forearm is the radius; the one on the bottom is the ulna.
• The other row of carpal bones connects with the bones of the palm
of the hand.
• There are synovial joints between the carpal bones and the wrist.
• The joint surfaces, where the bones meet, are covered with
articular cartilage which helps movement.
 Bones of the Hand
• Knuckle cracking does not serve any beneficial purpose and may be
harmful to the fingers due to the stretching of the joint capsule.
• The hand has 19 bones: 5 elongated metacarpal bones, which are
next to the wrist and make up the palm; 14 phalanges which make
up the fingers.
• Each finger has 3 phalanges, the thumb has 2.
• These 19 bones collectively form 14 separate joints.
• The knuckle joints, metacarpophalangeal (MCP) joints, join the
fingers to the palm.
• The interphalangeal (IP) joints are the finger joints.
• There are synovial joints between the metacarpals and phalanges—
these bones are also covered with articular cartilage
 Muscles of the Hand
• The muscles in the forearm and palm (thenar muscles)
all work together to keep the wrist and hand moving,
stable, and aligned
• The muscles that move the fingers and thumb are
above the wrist in the forearm.
• Long flexor tendons extend from the forearm muscles
through the wrist and attach to the small bones of the
fingers and thumb.
• When you bend or straighten your finger, these flexor
tendon slide through a snug tunnel, called the tendon
sheath, that keeps the tendon in place next to the
bones.
 Tendons
• Tendons are white, flexible fibrous cords at the
ends of muscles that attach the muscles to the
radius, ulna, carpals, metacarpals and phalanges.
When the muscles contract, they pull on the
tendons to move the bone.
• The tendons that run down our fingers are held
in place by a series of ligaments, called pulleys,
that arch over the tendons forming a “tunnel-
like” sheath.
• Normally, the tendons glide easily through the
tunnel. Some tendons also serve as stabilizers.
Tendons
• A series of ligaments in a tunnel-like
arrangement hold the tendons in place on the
bones.
• A slippery coating, called tenosynovium,
surrounds the tendons and keeps the tendons
moving smoothly under the ligaments when
the hand grasps objects.
 Ligaments

• Ligaments of the back of the hand

• Hand Ligaments are tough bands of fibrous
tissue that join bones together.
• Six major ligaments give stability to the wrist
by joining the radius to the carpal bones and
binding the two rows of carpal bones
together.
• These ligaments joint with others to link the
wrist to the hand.
 Joint Capsule

• Other stabilizers in the hand include joint

capsules, which are made of fibrous
connective tissue that surrounds the joints.
• A synovial membrane inside the joint
capsules provides synovial fluid to lubricate all
the joints
 Muscles of the hand
• Muscles acting on the hand can be divided into two
groups:
➢ extrinsic and
➢ intrinsic muscles.
• The extrinsic muscles are located in the anterior and
posterior compartments of the forearm.
• They control crude movements and produce a forceful
grip.
• The intrinsic muscles of the hand are located within the
hand itself.
• They are responsible for the fine motor functions of the
hand.
 Intrinsic muscles
• These include
• the adductor pollicis,
• palmaris brevis,
• interossei,
• lumbricals,
• thenar and
• hypothenar muscles.
 Muscles of the Hand

Interossei Muscles
• The interossei muscles originate between the
metacarpals.
• There are 4 dorsal and 3 palmar interossei muscles.
• They insert onto the proximal phalanx and extensor
hood of each finger.
• Palmar interossei ADduct the fingers, and dorsal
interossei ABduct the fingers (hence PAD/DAB).
• The radial artery enters the hand by passing between
the two heads of the first dorsal interosseous.
 Interossei

• The interossei muscles are located between the

metacarpals.
• They can be divided into two groups:
➢ the dorsal and
➢ palmar interossei.
• In addition to their actions of abduction (dorsal
interossei) and adduction (palmar interossei) of
the fingers,
• the interossei also assist the lumbricals in flexion
and MCP joints and extension at the IP joints.
 Palmar Interossei

Palmar Interossei
• These are located anteriorly on the hand.
• There are three palmar interossei muscles – although
some texts report a fourth muscle at the base of the
proximal phalanx of the thumb.
• Attachments:
➢ Each interossei originates from a medial or lateral surface
of a metacarpal, and
➢ attaches into the extensor hood and proximal phalanx of
same finger.
• Actions: Adducts the fingers at the MCP joint.
• Innervation: Ulnar nerve.
Palmar interossi
 Dorsal Interossei

Dorsal Interossei
• The most superficial of all dorsal muscles, these can be
palpated on the dorsum of the hand. There are four
dorsal interossei muscles.
• Attachments:
➢ Each interossei originates from the lateral and medial
surfaces of the metacarpals.
➢ They attach into the extensor hood and proximal
phalanx of each finger.
• Actions: Abduct the fingers at the MCP joint.
• Innervation: Ulnar nerve
Dorsal interossi
 Lumbricals

• These are four lumbricals in the hand, each associated

with a finger.
• They are very crucial to finger movement, linking the
extensor tendons to the flexor tendons.
• Denerveration of these muscles is the basis for
the ulnar claw and hand of benediction.
• Attachments:
➢ Each lumbrical originates from a tendon of the flexor
digitorum profundus.
➢ They pass dorsally and laterally around each finger,
and inserts into the extensor hood.
• Actions: The flex at the MCP joint, and extend
at the interphalangeal (IP) joints of each
finger.
• Innervation: The lateral two lumbricals (of the
index and middle fingers) are innervated by
the median nerve.
• The medial two lumbricals (of the little and
ring fingers) are innervated by the ulnar nerve
 Lumbricals

• The 4 lumbricals are thin worm-like muscles

that flex the metacarpophalangeal joints and
• extend the interphalangeal joints.
• They arise from the tendons of flexor
digitorum profundus.
Lumbricals
 Thenar and Hypothenar eminence

Thenar eminence (thumb side)

• Opponens pollicis is deep
• Flexor pollicis brevis is on the ulnar side of the
eminence
• Abductor pollicis brevis is on the radial side of
the eminence
 Thenar Muscles

• Thenar Muscles
• The thenar muscles are three short muscles
located at the base of the thumb.
• The muscle bellies produce a bulge, known as
the thenar eminence.
• They are responsible for the fine movements of
the thumb.
• The median nerve innervates all the thenar
muscles.
Thenar Muscles
Diagram
 Opponens Pollicis

• Opponens Pollicis
• The opponens pollicis is the largest of the thenar
muscles, and lies underneath the other two.
• Attachments:
➢ Originates from the tubercle of the trapezium, and the
associated flexor retinaculum.
➢ It inserts into the lateral margin of the metacarpal of
the thumb (i.e. the first metacarpal).
• Actions: Opposes the thumb, by medially rotating and
flexing the metacarpal on the trapezium.
• Innervation: Median nerve.
 Abductor Pollicis Brevis

Abductor Pollicis Brevis

• This muscle is found anteriorly to the opponens pollicis
and proximal to the flexor pollicis brevis.
• Attachments:
➢ Originates from the tubercles of the scaphoid and
trapezium, and from the associated flexor retinaculum.
➢ Attaches to lateral side of proximal phalanx of the
thumb.
• Actions: Abducts the thumb.
• Innervation: Median nerve.
 Flexor Pollicis Brevis

Flexor Pollicis Brevis

• The most distal of the thenar muscles.
• Attachments:
➢ Originates from the tubercle of the trapezium and from the
associated flexor retinaculum.
➢ Attaches to the base of the proximal phalanx of the thumb.
• Actions: Flexes the metacarpophalangeal (MCP) joint of the
thumb.
• Innervation: Median nerve.
• The deep head is innervated by the deep branch of the
ulnar nerve.
 Hypothenar eminence (little finger
side)

• Opponens digiti minimi is deep

• Flexor digiti minimi is on the radial side of the
eminence
• Abductor digiti minimi is on the ulnar side
Diagram
 Hypothenar Muscles

• The hypothenar muscles produce the

hypothenar eminence – a muscular
protrusion on the medial side of the palm, at
the base of the little finger.
• These muscles are similar to the thenar
muscles in both name and organisation.
• The ulnar nerve innervates the muscles of the
hypothenar eminence.
 Opponens Digiti Minimi

Opponens Digiti Minimi

• The opponens digit minimi lies deep to the other
hypothenar muscles.
• Attachments:
➢ Originates from the hook of hamate and
associated flexor retinaculum,
➢ inserts into the medial margin of metacarpal V.
• Actions: It rotates the metacarpal of the little
finger towards the palm, producing opposition.
• Innervation: Ulnar nerve.
 Abductor Digiti Minimi

Abductor Digiti Minimi

• The most superficial of the hypothenar muscles.
• Attachments:
➢ Originates from the pisiform and the tendon of
the flexor carpi ulnaris.
➢ It attaches to the base of the proximal phalanx of
the little finger.
• Actions: Abducts the little finger.
• Innervation: Ulnar nerve.
 Flexor Digiti Minimi Brevis
Flexor Digiti Minimi Brevis
• This muscles lies laterally to the abductor digiti
minimi.
• Attachments:
➢ Originates from the hook of hamate and adjacent
flexor retinaculum.
➢ It is inserted into the base of the proximal
phalanx of the little finger.
• Actions: Flexes the MCP joint of the little finger.
• Innervation: Ulnar nerve.
 Spaces of the Hand
• It is a potential space in the palm of the hand
that is continuous with the facial spaces of the
forearm through the flexor retinaculum.
• This space is found medial to the lateral
palmar septum.
• In front – skin, superficial fascia, the flexor
tendon compartment with the tendons of the
5th, 4th and 3rd digits.
Spaces
 SPACES OF THE HAND
• The arrangement of fasciae and the fasciae
septa in the hand is such that many spaces are
formed.
• These spaces are of surgical importance
because they may become infected and
distended with pus.
The important spaces are as follows
A. Palmer spaces
1. Pulp spaces of the fingers
2. Midpalmer space
3. Thenar space
B. Dorsal spaces
1. Dorsal subcutaneous space
2. Dorsal subaponeurotic space
C. The forearm space of parona.
 Pulp Space of the Fingers
• The tip of the fingers and thumbs contain
subcutaneous fat arranged in tight compartments
formed by fibrous septa which pass from the skin
to the posterior of the terminal phalanx.
• Infection of this space is known as whitlow
• The rising tension in the space gives rise to
severe throbbing pain.
• Infections in the pulp space (whitlow) can be
drained by a lateral incision which opens all
compartments and avoids damage to the tactile
tissue in front of the finger.
• If neglected, a whitlow may lead to necrosis of
the distal four-fifths of the terminal phalanx
due to occulation of the vessel by tension.
• The proximal one-fifth (epiphysis) escapes
because its artery does not transverse the
fibrous septa
Features Midpalmer space Thenar space
1. Shape Triangular Triangular
2. Situation Under the inner half of the hollow Under the outer half of the hollow
of the palm of the palm
3. Extent:
Proximal Distal margin of the flexor Distal margin of the flexor
retinaculum retinaculum
Distal Distal palmer crease Proximal transverse palmer crease

4 Communication:
Proximal Forearm space Forearm space
Distal Fascial sheaths of the 3rd and 4th Fascial sheath of thr first lumbrical
lumbricals

5. Boundaries:
Anterior • flexor tendons of 3rd, 4th and 5th • Short muscle of thumb
fingers • Flexor tendons of the index finger
•2nd , 3rd, and 4th lumbricals • first lumbricals
• palmer aponeurosis • Palmer aponeurosis
Features Midpalmer space Thenar space
Posterior Fascia covering interossei and Transverse head of adductor
metacarpals pollicis
Lateral Intermediate palmer septum Tendon of flexor pollicis longus
with radial bursa
Lateral palmer septum
Medial Medial palmer septum Intermediate palmer septum
6. Drainage Incision in either the 3rd or 4th Incision in the first web,
web space posteriorly
 Forearm Space of Parona
• Rectangular space situated deep in the lower part of
the forearm just above the wrist.
Boundaries
• Lies in front of the pronator quadratus, and deep to the
long flexor tendons
• Superiorly, the space extends up to the oblique region
of the flexor digitorum superficialis.
• Inferiorly, it extends up to the flexor retinaculum, and
communicates with the midpalmer space
• The proximal part of the flexor synovial sheath
portrudes into the forearm space.
 Forearm Space of Parona
• The forearm space may be infected through
infections in the related synovial sheath,
especiallyof the ulnar bursa.
• Pus points at the margins of the distal part of
the forearm where it may be drained.
 SYNOVIAL SHEATHS
• Many of the tendons entering the hand are
surrounded by synovial sheaths.
• The extent of these sheaths is of surgical
importance as they can be infected.
Digital Synovial Sheaths
• The synovial sheaths of the 2nd, 3rd and 4th are
independent and terminate proximally at the
levels of the heads of the metacarpals.
 Digital Synovial sheaths contd…
• The synovial sheath of the little finger is
continuous proximally with the ulnar bursa,
and that of the thumb with the radial bursa.
• Therefore, infections of the little finger and
thumb are more dangerous because they can
spread into the palm and even 2.5cm above
the wrist.
 Ulnar Bursa
• Infections of this bursa is usually secondary to
the infection of the little finger, and
• s this in turn may spread to the forearm space
of the parona.
• It results in an hour-glass swelling also called a
compound palmer ganglion
 Nerves of the Hand

• The ulnar nerve (C8-T1) supplies

• all of the intrinsic muscles of the hand,
• apart from the muscles of the thenar
eminence and the radial two lumbricals
(these muscles are supplied by the median
nerve (C5-T1).
 Nerves of the Hand
• The median nerve supplies sensation to the
radial 3 and a half fingers on the palmar
aspect, as well as the nail beds.
• Sensation to the palmar and dorsal side of the
ulnar one and half fingers is supplied by the
ulnar nerve.
• The radial nerve supplies the radial 3 and a
half fingers on the dorsal side.
Nerves of the Hand
Nerves of the Hand
 Blood Supply and Drainage of the
Hand
• The superficial palmar arch is the main
continuation of the ulnar artery.
• It receives a small superficial branch from the
radial artery and supplies the fingers with
blood via the proper digital arteries.
• The deep palmar arch is the main branch of
the radial artery and supplies the deep hand
structures.
• Paired veins accompany the arterial arches
and share the same names (i.e. radial and
ulnar).
• The more superficial cephalic and basilic
veins drain the dorsal venous network of the
hand.
 Clinical significance
Carpal tunnel syndrome
• If the median nerve becomes compressed
within the carpal tunnel, there is paraesthesia
in the radial 3 and a half fingers as well as
thenar muscle wasting.
Ulnar paradox

• Usually, the more proximal a nerve injury, the worse

it is. The opposite is true when we consider the ulnar
nerve.
• This is because one of the muscles that flexes the
fingers (Flexor digitorum profundus, which lies in the
forearm) is partially innervated by it.
• Hence a proximal injury will remove innervation to
the forearm muscles and the hand muscles.
• A distal injury only takes out the hand
muscles; hence the still functioning finger
flexors give the patient a clawed appearance
in the ring and little finger.
• With a proximal injury leading to an open
palm, there is more capacity for hand function
Dupuytren’s contracture
• The palmar aponeurosis is a thick area of
fascia that is tightly attached to the skin. It
may thicken and contract which causes the
little and ring finger to flex abnormally.
Scaphoid fracture
• The scaphoid receives its blood supply from a
nutrient branch of the radial artery.
• It enters at the distal pole of the bone and runs
to its proximal part.
• A fracture of the scaphoid (which can result from
a fall onto an outstretched hand) can, therefore,
lead to avascular necrosis of the proximal bony
fragment.
• Symptoms include a tender anatomical
snuffbox.
 Problems in the Hand and Wrist
(Summary)
• Inflammation
• Muscle Tightness
• Muscle Strain
• Muscle Tear
• Muscle Spasm
• Tendinitis
• de Quervain’s Tenosynovitis
• Trigger Finger
• Jammed Finger
• Arthritis
• Carpal Tunnel Syndrome
• Cubital Tunnel Syndrome: Cubital Tunnel Syndrome is a
condition that involves pressure or stretching of the ulnar
nerve (also known as the “funny bone” nerve), which can
cause numbness or tingling in the ring and small fingers,
pain in the forearm, and/or weakness in the hand
• Wrist Drop
• Fracture
• Dislocation