SummaryThe wrist is comprised of the carpus and the radiocarpal joint. The carpus is
the complex of eight carpal bones
(scaphoid, lunate, triquetrum,
pisiform, trapezium, trapezoid,
capitate, and hamate), while
the radiocarpal joint is the region of articulation between the carpus and radius. Distally, the carpus articulates with the
metacarpal bones, which, together with the
phalanges, make up the bones of the hand. The
forearm (lower arm or antebrachium) has an anterior compartment, which consists of the flexor group of muscles and is innervated by the ulnar and
median nerve, and a posterior compartment,
which consists of the extensor group of muscles and is innervated by the radial nerve. The flexor group of muscles is involved in
pronation of the forearm and flexion of the wrist and fingers,
while the extensor group of muscles is involved in supination of the forearm and extension of the wrist and fingers. Both groups of muscles are also involved in the
abduction and adduction of the wrist. The intrinsic muscles of the hand are responsible for hand and finger movement and consist of the thenar,
hypothenar, lumbrical, and
interossei muscles. The forearm, the wrist, and the hand are
perfused by the radial and ulnar artery and their branches. They are drained by the
superficial cephalic and basilic veins and the
deep radial and ulnar veins. OverviewBones and
joints Ulna Radius (bone)Radioulnar jointInjury
to the radial or ulnar diaphysis can disrupt the
proximal or distal
radioulnar joints. Interosseous membrane of the forearm Bones of the wrist
(carpal bones)
| Rows | Carpal bones | Characteristics |
|---|
Proximal row (lateral to
medial) | Scaphoid bone | - Located deep to the
anatomical snuff box
- Articulates with the radius proximally, trapezoid and
trapezium distally, capitate
and lunate medially
- Forms the lateral border of the
carpal tunnel, along with the
trapezium
- Origin of the
abductor pollicis brevis
- Most commonly fractured carpal bone (see
“Scaphoid fracture”)
- Vascular supply
- Deficient in the
proximal part of the bone
- At risk of
nonunion or
avascular necrosis after a
scaphoid fracture
|
|---|
| Lunate bone | - Articulates with the radius proximally, capitate and
hamate distally, scaphoid
laterally, and triquetrum medially
- Fracture or dislocation can cause acute carpal tunnel syndrome.
|
|---|
Triquetrum (formerly cuneiform) | - Wedge-shaped bone
- Articulates with the radius, the
pisiform anteriorly, the hamate
distally, and the lunate laterally
- Second most common carpal bone fracture
|
|---|
| Pisiform | - Sesamoid bone located in the
tendon of the flexor carpi ulnaris muscle
- Does not
articulate with the radius
- Origin of the abductor digiti minimi
- Forms the
medial border of the carpal tunnel and the
medial border of the Guyon canal (along with
the hook of hamate)
|
|---|
Distal row (lateral to medial) | Trapezium | - Articulates with the thumb metacarpal bone to form the
carpometacarpal joint of the thumb
- Forms the
lateral border of the carpal tunnel, along with the
scaphoid
- Insertion of
flexor pollicis brevis, opponens
pollicis, abductor pollicis brevis, and distal
attachment of the radial collateral ligament of the thumb
- Has a deep groove for the
flexor carpi radialis tendon
|
|---|
| Trapezoid bone | - Smallest carpal bone of the distal row
- Articulates with the
scaphoid proximally, the second
metacarpal distally, with the
trapezium laterally, and with the
capitate medially
- Origin of the
adductor pollicis
|
|---|
| Capitate | - Largest carpal bone
- Articulates with the scaphoid and lunate proximally, with the base of the 3rd
metacarpal and base of the 2nd and 4th
metacarpal bones distally, with the trapezoid laterally, and the
hamate medially
- Origin of the oblique head of the
adductor pollicis
|
|---|
| Hamate | - The hook of the hamate is a bony projection on the
palmar surface that is the point of insertion for the
flexor carpi ulnaris.
- Articulates with the lunate proximally, with the 4th and 5th
metacarpals distally, the
capitate laterally, and the
triquetrum medially
- The hook forms the medial
border of the carpal tunnel and
Guyon canal
- Origin of the
flexor digiti minimi brevis and
opponens digiti minimi
|
|---|
“Stubborn Larry Tried Pills That Triumphantly Cured Him:” Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate
(carpal bones from lateral to
medial and proximal to
distal). Anatomical snuffboxPain and tenderness in the
anatomical snuffbox after trauma to the wrist suggest a
scaphoid fracture. These
fractures can be difficult to see on plain
x-ray. Muscles and
fascia Muscles of the forearm [1]The
median nerve innervates all the forearm flexors, with the exception of the
flexor carpi ulnaris and the ulnar portion of the
flexor digitorum profundus, which are innervated by the
ulnar nerve. De Quervain syndrome involves
inflammation of the tendons on the radial side of the wrist, the
extensor pollicis brevis, and the
abductor pollicis longus. Supinator syndrome is a relatively rare entrapment syndrome in which the
deep branch of the radial nerve is trapped in the supinator tunnel between the heads of the
supinator muscle, resulting in weak finger extension. Causes include trauma or overuse of the
supinator muscle. The forearm extensors are innervated by the
radial nerve or by its branch, the
posterior interosseous nerve. The
superficial flexors originate from the medial epicondyle of
the humerus, and the superficial extensors from the
lateral epicondyle of the humerus.
Thenar muscles These muscles form the thenar eminence (the muscular prominence on the
palmar aspect at the base of the thumb) of the palm and exert their action mainly on the 1st
MCP. Hypothenar muscles These form the
hypothenar eminence (the muscular prominence located on the
palmar aspect at the base of the 5th finger) and exert their action mainly on the
5th MCP. The muscles of the
hypothenar eminence are innervated by the
ulnar nerve.
Lumbricals and interossei PAD: Palmar
interossei ADduct the fingers. DAB: Dorsal
interossei ABduct the fingers.
Fascia and retinacula of the wrist and hand [1]
| Characteristics of the fascia and retinacula of the wrist and hand |
|---|
| Structure | Definition | Attachments |
Structures/contents | Function |
|---|
Flexor retinaculum of the hand (flexor retinaculum;
transverse carpal ligament) | - Fibrous thickening of the
palmar deep
fascia located at the proximal part of the palm
| - Medial: pisiform and hook of
hamate
- Lateral:
scaphoid and trapezium
| - From medial to lateral:
ulnar nerve,
ulnar artery, the
palmar cutaneous branch of the
ulnar nerve, palmaris
longus tendon, the
palmar cutaneous branch of the
median nerve
| - Forms the roof of the carpal tunnel
- Holds the flexor
tendons in place
|
|---|
Extensor retinaculum (dorsal carpal
ligament) | - Fibrous thickening of the deep
fascia of the forearm that is located on the dorsal aspect of the
wrist
| - Medial: pisiform and
triquetrum
- Lateral:
distal radius
| - Superficial branch of radial
nerve
| - Holds the extensor tendons in place
|
|---|
| Palmar aponeurosis | - A triangular thickening of the
palmar deep
fascia that invests the muscles of the hand
| - The apex: continuation of the palmaris longus
tendon
- The base: divides into 4 slips that insert into the
skin overlying the MCP joints of the fingers
| - Consists of fibers in multiple directions that distally go on to form the pretendinous bands
| - Creates a semirigid barrier between the skin and the neurovascular and
tendon structures
- Forms part of the flexor tendon pulley
|
|---|
| Carpal tunnel | - An osteofibrous channel bound by the
carpal bones at the deep aspect and the
flexor retinaculum superficially
| - Medial: hook of the hamate and
pisiform bone
- Lateral: the
trapezium and scaphoid
| - Boundaries
- Roof: flexor retinaculum
- Floor: carpal groove
- Medial: lateral surface of hamate
- Lateral: medial surface of
trapezium
- Contents: 9
tendons and 1 nerve
- Median nerve
-
Tendon of the
flexor pollicis longus
- 4
tendons of the
flexor digitorum profundus
- 4
tendons of the
flexor digitorum superficialis
| - Passageway from the forearm to the anterior hand
|
|---|
Ulnar canal (Guyon canal) | - An osteofibrous channel on the
medial aspect of the palm
| - Medial: pisiform bone
-
Lateral: hook of the hamate
| - Boundaries
- Roof: palmar carpal
ligament
- Floor: flexor retinaculum and
hypothenar muscles
- Medial:
pisiform
- Lateral: hook of the
hamate
- Contents
|
|---|
The palmar aponeurosis is the structure that
hypertrophies and contracts in Dupuytren disease. Vasculature and lymphatic drainageInnervationThe forearm and hand are innervated by branches of the brachial plexus. The
median, radial, and ulnar nerves are terminal branches of the brachial plexus that provide motor and sensory innervation. Motor innervation - For further
information on motor innervation of the forearm and hand, see “Neurovasculature of the upper limbs.”
Sensory innervation- The
sensory innervation of the hand is provided by the median nerve,
radial nerve, and
ulnar nerve.
- The sensory innervation of the forearm is provided by the
lateral cutaneous nerve of the forearm,
medial cutaneous nerve of the forearm, and
posterior cutaneous nerve of the arm.
- For further information on sensory innervation of the forearm and hand, see
“Neurovasculature of the upper limbs.”
Dermatomal distribution of the forearm and hand - C6:
posterolateral forearm, thumb, and lateral side of the index finger
- C7:
ventral forearm, middle finger, medial side of the index finger, and
lateral side of the ring finger
- C8:
distal third of the medial forearm, the little finger, and
medial side of the ring finger
- T1:
proximal two-thirds of the medial forearm
Clinical
significanceBones and joints-
Ulna
- Ulnar fractures
- Ulnar styloid
fracture (associated with distal radius fractures)
- Radius
- Distal radius fractures (e.g.,
Colles fracture,
Smith fracture)
- Radial head subluxation
-
Radioulnar joint
-
Carpal bones
- Scaphoid fracture
- Lunate dislocation
- Metacarpal bones: boxer's fracture
(metacarpal neck fracture)
-
Joints of the wrist and hand
-
Trapeziometacarpal osteoarthritis
(rhizarthrosis)
- The saddle joint of the
thumb is susceptible to cartilaginous degeneration, resulting in
osteoarthritis.
- Approximately 8–12% of the population is affected by carpometacarpal
osteoarthritis. [2]
- Clinical features:
pain and swelling at the base of the thumb
- Diagnostics [2]
- Thumb grind test: performed by applying axial compression along the
plane of the metacarpal bone and rotating the thumb
metacarpal base. Pain or
crepitus indicates a positive grind test, suggesting carpometacarpal
osteoarthritis.
- Thumb lever test: performed by grasping the first
metacarpal just distal to the base and moving it back and
forth in the lateral and medial directions.
Pain or crepitus indicates a positive lever test, suggesting
carpometacarpal osteoarthritis.
- MCP extension test: performed by placing one finger on the
interphalangeal joint and applying resistance against extension while the patient tries to extend the thumb.
Pain or crepitus indicates a positive
MCP extension test, suggesting carpometacarpal
osteoarthritis.
- Treatment: may involve excision of the
trapezium.
-
Metacarpophalangeal joint: 1st
MCP joint is affected early by
rheumatoid arthritis
-
Interphalangeal joints
-
Bouchard nodes (in
osteoarthritis) and
Boutonniere deformity (in
rheumatoid arthritis) affect the
PIP.
-
Heberden nodes (in
osteoarthritis) and
Swan neck deformity (in rheumatoid arthritis) affect the DIP.
Muscles and fascia- De Quervain tenosynovitis
- Dupuytren contracture
- Carpal tunnel syndrome
- Guyon canal syndrome
- Supinator syndrome
Innervation- Ulnar nerve entrapment
- Median nerve neuropathy
- Radial neuropathies
Other- Finger injuries
- Volkmann ischemic contracture
- Compartment syndrome
References-
Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences ; 2016
- Model Z, Liu AY, Kang L, Wolfe SW, Burket JC, Lee SK. Evaluation of Physical Examination Tests for Thumb Basal Joint Osteoarthritis. Hand. 2016; 11 (1): p.108-112. doi: 10.1177/1558944715616951 . |
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Which nerve is involved in carpal tunnel syndrome?
Carpal tunnel syndrome is caused by pressure on the median nerve. The carpal tunnel is a narrow passageway surrounded by bones and ligaments on the palm side of the hand. When the median nerve is compressed, symptoms can include numbness, tingling, and weakness in the hand and arm.
What is the cause of carpal tunnel syndrome?
This abnormal pressure on the nerve can result in numbness, tingling, pain, and weakness in the hand. Carpal tunnel syndrome is caused by pressure on the median nerve as it travels through the carpal tunnel.
Lower Median Nerve Palsy is a general term that refers to nerve injuries of the wrist that are most commonly caused by untreated compression conditions, such as Carpal Tunnel Syndrome.
What is ulnar nerve pain?
Ulnar neuropathy occurs when there is damage to the ulnar nerve. This nerve travels down the arm to the wrist, hand, and ring and little fingers. It passes near the surface of the elbow. So, bumping the nerve there causes the pain and tingling of "hitting the funny bone."
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