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Wrist & Hand
Long Nguyen
Past exam q’s
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Diagram of a cross section of Radius, Ulna and tubes provided with the
caption: “At the lower end of the forearm there is an extensor retinaculum.
Septa attach the retinaculum to the radius and ulna forming six osseofascial
tunnels for the extensor tendons”. List the tendons corresponding to each of
the numbered tunnels above. (Oct 00)
What is the arrangement of structures passing from the forearm to the wrist
at the level of the carpal tunnel within the flexor retinaculum.
Write short notes on the anatomy of the lunate bone. (Sept 04)
Draw a clear diagram and anatomical relations of the scaphoid bone. (April
04)
Write notes on the supernumerary bones of the hand. (?)
In the embryological development of the hand and foot, many of the bones
are homologous (for example the radius is a homologue of the tibia and the
ulna is homologous to the fibula). Which carpal bones and tarsal bones are
homologues? (Sept 02)
Regarding the thumb: (Oct 01) a what muscles are responsible for thumb
flexion? b extension? c abduction? d adduction? e what is the nerve supply
of each of these muscles
Write short notes on the arterial supply to the hand. (April 04)
Bones of the hand
• 8 carpal bones, 5
metacarpal bones, 14
phalanges
• 8 carpal bones lie in two
semicircular rows
separated by S-shaped
midcarpal joint
• Prox row – S, L, Tqm, P
• Distal row – Tpzm, Tpzd,
C, H
• Carpal bones articulate
with each other by
intercarpal joints
Carpal bones
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Scaphoid bone (boat shaped)
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Most commonly fractured carpal bone
Convex articular proximal surface for radius
Flat surface medially for lunate
Concave distomedially for capitate
Convex distal articulation with trapezium &
trapezoid
Tubercle on the volar aspect of distal lateral
surface
Narrow waist perforated by vascular
foramina more numerous distally
In 15%, blood supply to scaphoid is solely
supplied from nutrient arteries which pass
distal to proximal
Fracture trhough the waist can produce
avascular necrosis of proximal portion
Lunate
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Most commonly dislocated carpal bone
(displaced anteriorly)
Convex proximal facet for radius
Concave distally for capitate
Facet for adjoining bones on either side
Carpal bones
• Triquetral
– Oval fact on distal palmar surface for pisiform
• Pisiform
– Flat surface for articulation with triquetral
• Trapezium
– Saddle-shaped distal articular surface with 1st MC
– Tendon of flexor carpi ulnaris lies in a vertical groove on the palmar
surface
• Trapezoid
• Capitate
– Convex proximal surface for lunate articulation
– Articulates with 3rd MC and small facet for 4th MC
• Hamate
– hook projects from the distal part of the palmar surface, and is directed
laterally
Metacarpals & phalanges
• 1st MC (saddle joint) articulates solely with
trapezium
• Remaining MC’s had expanded bases and
articulate with each other and the distal
row of carpal bones
• Middle MC has prominent styloid process
projecting dorsally into angle between
trapezoid and capititate
• MCJ and IPJ are hinged synovial joints
Ossification
• Carpus cartilagenous at birth
• Ossification in a clockwise
direction from capitate
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Capitate & hamate 1 year
Triquetral 2-3 year
Lunate 3-5 year
Scaphoid, trapezium,
trapezoid: 6 year
– Pisiform 10-12 year
• MC & phalangeal shafts ossify
in utero
• Radiographs of the left hand
are obtained for bone age
assessment by comparing
features such as epiphyseal
appearance and fusion
18m
3y 9m
7y 1m
5y 4m
13y
Ossification - variable timing
2y 11m
5y 4m
6y 11m
7y 1m
Supernumery bones
• Sesamoid in the tendon of the flexor pollicis brevis near
MC head of thumb
• Os centrale found between scaphoid, trapezoid and
capitate. May represent tubercle of scaphoid that has not
fused with upper pole
• Os radiale externum immediately distal to radial styloid
Wrist Joint
• Condyloid/ellipsoid synovial joint
• Radius articulates with scaphoid and lunate. Articulation
with triquetral only on ulnar deviation
• Ulna shorter than distal radius. Fibrocartilaginous disc
projects laterally from ulna styloid to the radius. It
articulates with lunate and triquetral
• Fibrous capsule lined by synovium incloses the joint
• Strengthened by dorsal and palmar radiocarpal
ligaments which run distally and medially from radius
• Radial and ulnar collateral ligaments
Wrist Joint
Wrist Movements
• Flexion (80º)
– Flexor carpi radialis & flexor carpi ulnaris
– Palmaris longus, flexors of fingers and thumb, abductor pollicis longus
• Extension (60º)
– Extensor carpi radialis longus, extensor carpi radialus
brevis, extensor carpi ulnaris
– Extensors of fingers and thumb
• Abduction (15º radial)
– FCR, ECRL, ECRB
– APL
• Adduction (45º ulna)
– FCU, ECU
Extensor retinaculum
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Antebrachial fascia thickened
posteriorly at the wrist to form a
transverse 2.5cm band
Proximal attachment: anterolateral
border of radius above styloid
process
Distal attachment: pisiform &
triquetral
6 shealths containing 9 tendons
occupy the six osseofibrous
tunnels deep to the extensor
retinaculum
– A) 3 for thumb in 2 shealths (EPL)
(EPB,APL)
– B) 3 for extensors of the wrist in 2
sheaths (ECU) (ECRL,ECRB)
– C) 3 for extensors of the digits in 2
sheaths (EDigitorum, E Indicis)
(Extensor digiti minimi)
Extensor retinaculum
Anatomical snuff box
Palmar Aponeurosis
• Fascia of the forearm continues distally as the
deep fascia of the palm
• Fascia is thickened in the palm (thin over the
thenar and hypothenar eminences)
• Overlies long flexor tendons of the palm
• Proximal end continuous with flexor retinaculum
• Distal ends of the aponeurosis divides at the
roots of the digits into four longitudinal bands
which attaches to base of prox phalanx
Fascial compartments
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Central compartment
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Flexor tendons and shealths
Superficial palmar arch
Branches of median and ulnar nerves
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Superior boundary: palmar aponurosis
Inferior boundary: deep muscles of palm (adductor pollicis)
Bounded on either side by septa passing from medial and lateral edges of
aponeurosis to 1st and 5th MC bones
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Medial/hypothenar compartment
Lateral thenar compartment
• Potential space between central compartment
and the deep muscles of the palm: midpalmar
space
• Retroadductor space between adductor pollicis
and 1st dorsal interosseous muscle
Carpal tunnel
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Carpal bones angled producing anterior
concavity
Hollow formed by these bones is bounded
anteriorly by flexor retinaculum
Flexor retinaculum attachments
– Medially: hook of hamate & pisiform
– Laterally: ridge of trapezium & scaphoid
tubercle
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Contents:
– Median nerve immediately deep to
retinaculum
– Flexor pollicis longus tendon
– Tendons of flexor digitorum superficialis (x4)
and flexor digitorum profundus (x4)
– Tendon of flexor carpi radialis grooves the
trapezium and lies in separate compartment
of tunnel
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Relations
– Ulnar artery superficial to flexor retinaculum,
lateral to ulnar nerve
Intrinsic hand muscles
• Palmar aspect
• 3 groups
– Thenar muscles
– Hypothenar muscles
– Lumbricals and interossei
Thenar muscles
• Produce thenar eminence
• Oppose thumb
• Supplied by recurrent branch of median nerve
Muscle
Prox
attachment
Abductor
pollicis brevis
Flex
retinaculum,
tubercles of
scaphoid &
trapezium
Flexor pollicis
brevis
Oppones
pollicis
Adductor
pollicis
Flex
retinaculum,
tubercle of
trapezium
Oblique:
base or 2nd &
3rd MC,
capitate
Transverse:
anterior body
of 3rd MC
Distal
attachment
Lateral
aspect base
of prox 1st
phalanx
Innervation
Action
Median n.
recurrent
branch
Abduction
Opposition
Flexion
Opposition
Lateral
aspect 1st
MC
Medial
aspect base
of prox 1st
phalanx
Opposition
Medial
rotation
Ulnar n. deep
branch
Adduction
(grasp)
Movements of the thumb
Movement
Muscles
Innervation
Flexion at MCP/IPJ
Flexor pollicis longus
Flexor pollicis brevis
Median (anterior interosseous n)
Median (recurrent branch)
Extension at MCP/IPJ
Extensor pollicis longus
Extensor pollicis brevis
Radial (posterior interosseous)
Radial (posterior interosseous)
Flexion (flexion/transpalmar
adduction)
Flexor pollicis brevis
Adductor pollicis
Median (recurrent branch)
Ulnar (deep branch)
Extension (radial abduction)
Abductor pollicis longus
Extensor pollicis brevis
Radial (posterior interosseous)
Radial (posterior interosseous)
Abduction (palmar)
Abductor pollicis longus
Abductor pollicis brevis
Radial (posterior interosseous)
Median (recurrent branch)
Adduction (ulnar adduction)
Adductor pollicis
Ulnar (deep branch)
Opposition
Oppones pollicis
Flexor pollicis brevis
Abductor pollicis brevis
Median (recurrent branch)
Hypothenar muscles
Muscle
Prox attachment
Abductor digiti minimi
Pisiform bone
Flexor digiti minimi
brevis
Opponens digiti
minimi
Distal attachment
Innervation
Action
Abduction
Medial aspect base
of 5th prox phalanx
Flexion
Ulnar n. deep branch
Hook of hamate and
flex retinaculum
Medial border of 5th
MC
Opposition (towards
thumb)
Short muscles in the hand
• 4 Lumbricals
– act on medial 4 digits
– Flex digits at the MCPJ and extend IPJ
• 7 Interossei
– 3 palmar adduct (PAD)
– 4 dorsal abduct (DAB)
Muscle
Lumbricals 1 & 2
Prox attachment
Lateral 2 tendons of
flexor digitorum
profundus
Lumbricals 3 & 4
Medial 3 tendons of
FDP
Palmar interossei
Palmar surface of
2nd, 4th, 5th MC
Dorsal interossei
Adjacent sides of
two MC bones
Distal attachment
Lateral aspect of
extensor expansion
of digits 2-5
Extensor
expansions & bases
of prox phalanges of
digits 2, 4, 5
Extensor
expansions & bases
of prox phalanges of
digits 2-4
Innervation
Action
Median n.
Flex digits at the
MCPJ and extend
IPJ
Ulnar n. deep
branch
Adduct digits &
assist lumbricals
Ulnar n. deep
branch
Abduct digits &
assist lumbricals
Long flexor tendons
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Flexor digitorum superficialis tendon
– Enters the fibrous flexor shealth on the
palmar surface of the flexor digitorum
profundus
– Splits into 2 and wraps around the profundus
and meets on deep surface in a chiasma
– Distal to chiasma, superficialis tendon is
attached to margins of the front of middle
phalanx
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Profundus tendon
– enters fibrous sheath deep to the
superficialis
– then lies superficial distal to the split of the
superficialis tendon
– attaches to base of terminal phalanx
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Each tendon receives blood vessels
invested in synovial membrane called
vincula
Long extensor tendons
• Extensor tendon blends in with
a triangular fibrous expansion
on the dorsum of the proximal
phalanx
• Margins of expansion
thickened by attachments of
the tendons of lumbrical and
interossei
• Extensor tendon splits into
middle and two collateral slips
as it approaches PIPJ
• Middle slip attached to base of
middle phalanx
• Collateral slips joined by
thickened margins of
expansion and converge to
insert into base of distal
phalanx
Arterial supply
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Ulnar artery continues as superficial
palmar “arch”
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Usually not complete arch
Continuous with superficial palmar
branch of radial artery if complete
Gives rise to 3 common palmar digital
arteries which run distally to the webs
between the fingers and divides into
proper palmar digital arteries (run
alongside 2nd-4th digits)
Radial artery
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Princeps pollicis artery (thumb)
Radialis indicis artery (lateral side of
2nd digit)
Joins deep branch of ulnar artery to
form deep palmar arterial arch
Arch gives rise to 3 palmar metacarpal
arteries which run distally and join the
common palmar digital arteries
Cutaneous nerves of the hand