33. Functional anatomy of the hand and wrist

Question 1

What do the bones of the wrist and hand do?what makes up the wrist joint?

Answer 1

• The bones of the wrist and hand provide support and flexibility to the soft tissues.
• The wrist joint comprises the distal radius, the triangular fibrocartilage complex (TFCC), the scaphoid and the lunate.
• The ulna is not part of the wrist joint; it articulates with the radius at the distal radioulnar joint.
• The carpal bones form a convex surface which articulates with the concave surface of the radius and the triangular fibrocartilage

Question 2

What type of joint is the wrist joint and what movements can it perform

Answer 2

ellipsoid type of synovial joint, allowing for movement in two axes; flexion, extension, adduction (also known clinically as ulnar deviation of the wrist) and abduction (radial deviation) all occur at the wrist.
Circumduction is a composite of all four of these movements (‘wind your hand round in circles’).

Question 3

What 4 ligaments stabilise the wrist joint?

Answer 3

• Dorsal + palmar radiocarpal ligaments = attach radius to carpal on the dorsal and palmar surface
• Ulnar + radial collateral ligaments

Question 4

Why are the radiocarpal ligaments important?

Answer 4

play an important role in ensuring that the hand follows the radius during pronation and supination of the forearm

Question 5

Which muscles are responsible for flexion of the wrist?

Answer 5

 Flexor carpi ulnaris
 Flexor carpi radialis
 Palmaris longus (very weak flexor)
The long flexors that cross the wrist also assist flexion at that joint i.e. flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus

Question 6

Which muscles are responsible for extension of the wrist?

Answer 6

 extensor carpi radialis longus
 extensor carpi radialis brevis
 extensor carpi ulnaris
with assistance from the extensor digitorum.
- Other muscles that cross the dorsum of the wrist also assist in extension i.e. extensor indicis, extensor digiti minimi, extensor pollicis longus, extensor pollicis
brevis and abductor pollicis longus.

Question 7

Which muscles are responsible for adduction (ulnar deviation) of the wrist?

Answer 7

 extensor carpi ulnaris

 flexor carpi ulnaris

Question 8

Which muscles are responsible for abduction (radial deviation) of the wrist?

Answer 8

 extensor carpi radialis longus
 extensor carpi radialis brevis
 flexor carpi radialis.

Question 9

How many carpal, metacarpals + phalanges?

Answer 9

eight carpal bones, five metacarpals and 14 phalanges. Each finger has three phalanges; proximal, middle and distal. The thumb has two; a proximal and a distal phalanx.

Question 10

What are the 8 carpal bones in the proximal and distal rows from radial (lateral) to ulnar?

Answer 10

PROXIMAL = Scaphoid, Lunate, Triquetrum, Pisiform
DISTAL = Trapezium, trapezoid, capitate hamate

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Question 11

What is important about the hamate

Answer 11

It has a projection on its palmar surface called the hook

Forms the ulnar border of the carpal tunnel and the radial border of guyons canal

Numbers of structure attach to the hook or hamate e.g flexor retinaculum

Question 12

What is the blood supply of the scaphoid?

Answer 12

The major blood supply to the scaphoid is via a dorsal carpal branch of the radial artery. This enters the dorsal
surface of the scaphoid distally and supplies the proximal 80% of the scaphoid by retrograde flow (i.e. flow back towards the wrist).

Question 13

Describe the articulations of the 5 metacarpals (radial to ulnar)

Answer 13

1 = trapezium + prox. phalanx of thumb
2 = trapezoid + prox. phalanx of index
3 = capitate + prox. phalanx of middle finger
4 = hamate + prox. phalanx of ring
5 = hamate + prox. phalanx of little

Question 14

Describe the structure of metacarpals

Answer 14

Each metacarpal consists of a base, shaft and a head. The medial and lateral surfaces of the shaft are concave and accommodate the interossei muscles

Question 15

Discuss the phalanges

Answer 15

The fingers have 3 phalanges (proximal, middle and distal)

The thumb only has 2 (proximal and distal)

Question 16

Name the movements of the thumb

Answer 16

• Flexion
• extension
• opposition
• reposition
• retropulsion
• palmar abduction
• radial abduction
• adduction
• circumduction

Question 17

What are the 2 divisions of hand muscles?

Answer 17

 Intrinsic muscles of the hand – muscles that originate within the hand and insert within the hand
 Extrinsic muscles of the hand – muscles that originate within the forearm and insert within the hand

Question 18

What are the 4 compartments of intrinsic hand muscles?

Answer 18

 Thenar compartment (thenar = thumb):
 Adductor compartment: Adductor pollicis
 Hypothenar compartment (hypothenar = little finger): Abductor digiti minimi, Flexor digiti minimi, Opponens digiti minimi
 Central compartment – Lumbricals, Interossei, `Palmaris Brevis

Question 19

What are the thenar muscles? what are they responsible for? what are the innervated by?

Answer 19

• Abductor pollicis brevis, Flexor pollicis brevis, Opponens pollicis
• They are responsible for the thenar eminence, which is the muscular prominence on the radial aspect of the palm.
• All supplied by the median nerve, except the deep head of flexor pollicis brevis which is supplied by
the ulnar nerve.
• Opponens pollicis is the largest of the thenar muscles and lies deep
to flexor pollicis brevis and abductor pollicis brevis.

Question 20

Describe the Opponens pollicis:
• Where does it originate
• Where does it insert
• What is its action
• What is it innervated by

Answer 20

• origin is Trapezium and flexor retinaculum
• insert on the Lateral border of 1st metacarpal
• Opposes thumb (by medially rotating and flexing 1st metacarpal)
• innervated by median nerve

Question 21

Describe the Abductor pollicis brevis:
• Where does it originate
• Where does it insert
• What is its action
• What is it innervated by

Answer 21

• origin is scaphoid, trapezium and flexor retinaculum
• inserts to lateral border of proximal phalanx of thumb
• action: palmar adducts the thumb
• innervated by median nerve

Question 22

Describe the Flexor pollicis brevis:
• Where does it originate
• Where does it insert
• What is its action
• What is it innervated by

Answer 22

• Superficial head originates at: Trapezium and flexor retinaculum
Deep head originates at: trapezoid and capitate
• inserts at Ulnar aspect of base of proximal phalanx of thumb (with adductor pollicis)
• action: Flexes metacarpophalangeal joint of thumb
• superficial head innervated by median nerve and deep head innervated by ulnar nerve

Question 23

What is the adductor compartment supplied by?

Answer 23

ulnar nerve

Question 24

What is the only muscle in the adductor compartment?

Answer 24

adductor pollicis

Question 25

Describe the Adductor pollicis:
• Where does it originate
• Where does it insert
• What is its action
• What is it innervated by

Answer 25

• origin:
Transverse head: Shaft of 3rd metacarpal
Oblique head: capitate and base of 2nd and 3rd metacarpals
• insert at Ulnar aspect of base of proximal phalanx of thumb (with flexor pollicis brevis)
• action: Adductor of the thumb - adduction from both both radial abduction and palmar abduction
• innervated by ulnar nerve

Question 26

What are the hypothenar muscles responsible for?

Answer 26

responsible for the hypothenar eminence, a muscular prominence on the ulnar aspect of the palm

Question 27

What are all the hypothenar muscles innervated by?

Answer 27

ulnar nerve

Question 28

Describe the Opponens digiti minimi:
• Where does it originate
• Where does it insert
• What is its action
• What is it innervated by

Answer 28

• originat at Hook of the hamate, flexor retinaculum
• insert at the Ulnar margin of 5th metacarpal
• action: Rotates the 5th metacarpal towards the palm, enabling opposition against the thumb.
• innervated by ulnar nerve

Question 29

Describe the abductor digiti minimi:
• Where does it originate
• Where does it insert
• What is its action
• What is it innervated by

Answer 29

• originate at Pisiform and tendon of flexor carpi ulnaris (FCU)
• insert at Base of proximal phalanx of little finger
• action: Abducts little finger (Note: abduction of the little finger only takes place in the coronal plane i.e. parallel to the palm)
• innervated by ulnar nerve

Question 30

Describe the flexor digiti minimi brevis:
• Where does it originate
• Where does it insert
• What is its action
• What is it innervated by

Answer 30

• originate at Hook of hamate and flexor retinaculum
• insert at Base of proximal phalanx of little finger
• action: Flexion of metacarpophalangeal joint of little finger
• innervated by ulnar nerve

Question 31

What does the central compartment contain?

Answer 31

contains palmaris brevis, the palmar and dorsal interossei and the four lumbricals

Question 32

What are the muscles in the central compartment innervated by?

Answer 32

The radial two lumbricals (to the index and middle finger) are supplied by the median nerve.
The ulnar two lumbricals (to the ring and little finger), the palmar and dorsal interossei and palmaris brevis are all supplied by the ulnar nerve.

Question 33

Describe the palmar brevis:
• Where does it originate
• Where does it insert
• What is its action
• What is it innervated by

Answer 33

Palmaris brevis is a small, thin muscle situated very superficially in the subcutaneous tissue overlying the hypothenar eminence.
• originate at Palmar aponeurosis and flexor retinaculum
• insert at Dermis of skin on medial margin of hand
• action: Dermis of skin on medial margin of hand
• innervated by ulnar nerve

Question 34

What is the role of the lumbricals?

Answer 34

There are four lumbricals in the hand, one for each of the fingers. Their role is to link the flexor digitorum profundus tendon on the palmar surface, to the extensor digitorum tendon on the dorsum. When they contract, they flex the fingers at the metacarpophalangeal (MCP) joint and extend at the interphalangeal (IP) joints

Question 35

Describe the lumbricals to the index and middle finger (I and II):
• describe the structure 
• Where does it originate
• Where does it insert
• What is it innervated by

Answer 35

• unipennate
• originate from the tendon of the flexor digitorum profundus (FDP) to their respective finger and insert into the extensor expansion
• they form a bridge from flexor tendon to extensor tendon.
• supplied by the median nerve

Question 36

Describe the lumbricals to the ring and little fingers (III and IV):
• describe the structure 
• Where does it originate
• Where does it insert
• What is it innervated by

Answer 36

• bipennate
• The lumbrical to the ring finger originates from the FDP tendons to both the middle and ring finger and inserts into the extensor expansion of the ring
finger.
• The lumbrical to the little finger originates from the FDP tendons to the ring and little finger and inserts into the extensor expansion of the little finger.
• The lumbricals to the ring and little finger are supplied by the ulnar nerve.

Question 37

What is the action of the lumbricals?

Answer 37

Flexion at metacarpophalangeal joint (MCPJ), extension at interphalangeal joints (IPJs)

Question 38

Where are the interossei located?

Answer 38

located between the metacarpals (interossei = between the bones)

Question 39

What are the groups of interossei?

Answer 39

dorsal interossei and palmar interossei

Question 40

What are the actions of the dorsal interossei and palmar interossei?

Answer 40

Their actions can be recalled using the mnemonics DAB (dorsal abduct) and PAD (palmar adduct). Through their insertion into the extensor expansion, they also assist the lumbricals in flexing the MCPJs and extending the IPJs. All of the interossei are supplied by the ulnar nerve.

Question 41

Describe the origin, insertion and action of all 4 of the dorsal interossei

Answer 41

1. • originates from the first and second metacarpals
   • inserts into the radial side of the base of the proximal phalanx and the extensor expansion of the index finger.
   • action:Abducts index finger and assists lumbricals in flexing MCP joint and extending IP joints
2. • origin: second and third metacarpals
   • insert at Radial aspect of base of proximal phalanx of
   middle finger and extensor expansion
   • action:Radially abducts (or radially deviates) middle finger and assists lumbricals in flexing MCP joint and
   extending IP joints
   3.
   • origin: third and fourth metacarpals
   • insert at Ulnar aspect of base of proximal phalanx of middle finger and extensor expansion
   • action: Ulnar abducts (or ulnar deviates) middle
   finger and assists lumbricals in flexing MCP joint and extending IP joints
   4.
   • origin:fourth and fifth metacarpals
   • insert at Ulnar aspect of base of proximal phalanx
   and extensor expansion of ring finger
   • action: Abducts ring finger and assists lumbricals
   in flexing MCP joint and extending IP joints

Question 42

Describe the origin, insertion and action of all 3 of the palmar interossei

Answer 42

1. palmar interosseous muscle to the index finger
   • origin: Shaft of second metacarpal
   • insertion:Ulnar side of base of proximal phalanx and extensor expansion to index finger
   • action: Adducts index finger toward middle finger
2. palmar interosseous muscles to the ring finger
   • origin: Shaft of 4th metacarpal
   • insertion: Radial side of base of proximal phalanx and extensor expansion to ring finger
   • action: Adducts ring finger toward middle finger

3.palmar interosseous muscles to the little finger
• origin: Shaft of 5th metacarpal
• insertion: Radial side of base of proximal phalanx and extensor expansion to little finger
• action: Adducts little finger toward middle and ring finger

Question 43

What are the three extrinsic muscles of the hand that insert into the digits?

Answer 43

 extensor digitorum
 flexor digitorum profundus
 flexor digitorum superficialis

Question 44

Describe the Extensor digitorum (extensor digitorum communis):
• Where does it originate
• Where does it insert
• What is it innervated by

Answer 44

• arises from the common extensor origin on the lateral epicondyle of the humerus
• At the dorsum of the wrist, it divides into four tendons which diverge on the dorsum of the hand and are inserted into the index, middle, ring and little fingers. Each tendon divides into a central slip that inserts into the base of the middle phalanx and two lateral slips that converge to insert into the base of the distal phalanx
• supplied by the posterior interosseous branch of the radial nerve.

Question 45

Describe the Flexor digitorum profundus (FDP):
• Where does it originate
• Where does it insert

Answer 45

• originates from the proximal two thirds of the shaft of the ulna and the adjacent interosseous membrane on the anterior forearm
• At the wrist, it divides into four tendons that pass through the carpal tunnel to insert into the base of the distal phalanx of each of the four fingers

Question 46

Describe the Flexor digitorum superficialis (FDS):
• Where does it originate
• Where does it insert

Answer 46

• humero-ulnar head originates from the medialepicondyle of the humerus, the ulnar collateral ligament and the coronoid process of the ulna, and the radial head originates from the superior half of the radius.
• divides into four tendons at the wrist that pass through the carpal tunnel but, unlike FDP, these tendons insert into the base of the middle phalanx of the four fingers.

Question 47

What is the relationship between FDP and FDS?

Answer 47

The FDS tendons divide into two slips at the proximal phalanx and the FDP tendon passes through the gap created. They then recombine to insert into the base of the middle phalanx. The FDP continues to insert into the
distal phalanx.

Question 48

What is the carpal tunnel?

Answer 48

a narrow passageway on the anterior (volar or palmar) surface of the wrist that serves as an entrance to the palm for numerous tendons and the median nerve.

Question 49

What are the borders of the carpal tunnel?

Answer 49

The deep border is comprised of the carpal bones which form a concavity. The superficial border is formed by the flexor retinaculum (also known as the transverse carpal ligament).

Question 50

What are the attachments of the flexor retinaculum?

Answer 50

 lateral (radial): scaphoid, trapezium

 medial (ulnar): hook of hamate, pisiform.

Question 51

What are the structures passing through the carpal tunnel?

Answer 51

 Flexor pollicis longus tendon
 Flexor digitorum superficialis tendons x 4
 Flexor digitorum profundus tendons x 4
 Median nerve

Question 52

Where is the palmar cutaneous branch of the median nerve given off? And why is it clinically important?

Answer 52

The palmar cutaneous branch of the median nerve (supplying sensation to the radial 2/3rds of the palm) is given off proximal to the carpal tunnel. This is clinically
important in carpal tunnel syndrome as, when the median nerve becomes compressed in the carpal tunnel, sensation to the palm is unaffected

Question 53

What is the Guyon’s canal?

Answer 53

a semi-rigid longitudinal canal in the wrist that allows passage of the ulnar nerve and artery into the hand.

Question 54

Why is the ulnar nerve not involved in carpal tunnel syndrome?

Answer 54

Guyon’s canal is superficial to the flexor retinaculum (transverse carpal ligament) and therefore the ulnar nerve is not involved in carpal tunnel syndrome

Question 55

Where is the Guyons canal palpated?

Answer 55

The canal can be palpated just radial (lateral) to the pisiform bone, passing between the pisiform and the hook of the hamate

Question 56

What forms the roof of the Guyon’s canal?

Answer 56

The roof is formed by the palmar carpal ligament, which is distinct from the transverse carpal ligament (flexor retinaculum)

Question 57

Why is the Guyon’s canal clinically important?

Answer 57

Guyon’s canal is clinically important as a site of ulnar nerve compression

Question 58

What is the anatomical snuff box?

Answer 58

The anatomical snuffbox ( also known as the radial fossa) is a triangular depression on the radial aspect of the dorsum of the hand, at the level of the carpal bones. It is best seen when the thumb is radially abducted.

Question 59

What are the borders of the anatomical snuff box?

Answer 59

 radial (lateral) border – tendons of abductor pollicis longus (sited most laterally) and extensor pollicis brevis
 ulnar (medial) border - tendon of extensor pollicis longus
 proximal border - styloid process of the radius
 floor - scaphoid and trapezium
 roof - skin

Question 60

What are the contents of the anatomical snuff box?

Answer 60

 radial artery
 superficial branch of the radial nerve
 cephalic vein

Question 61

What are the two arteries supplying the hand?

Answer 61

The radial artery and ulnar artery supply the hand via the deep and superficial palmar arches

Question 62

Describe the ulnar artery in the hand

Answer 62

• The ulnar artery may be palpated as it crosses anterior to the flexor retinaculum in company with the ulnar nerve in Guyon’s canal. Here, the artery lies radial (lateral)
to the pisiform bone and the ulnar nerve.
• In the hand, it divides into two branches, superficial and deep, both of which anastomose with corresponding branches of the radial artery to form
the superficial and deep palmar arches.
• The superficial palmar arch gives off the common palmar digital arteries which supply the fingers.
• In most people, the ulnar artery contributes mainly to the superficial palmar arch and therefore to the blood supply of the fingers.

Question 63

Describe the raidial artery in the hand

Answer 63

• The radial artery enters the hand between the tendons of brachioradialis and flexor carpi radialis.
• It gives off a superficial branch that anastomoses with the superficial palmar arch, then passes dorsally to cross the floor of the anatomical snuffbox on the dorsum of the hand before re-entering the palm between the two heads of adductor pollicis.
• The radial artery anastomoses with the deep branch of the ulnar artery to form the deep palmar arch.
• In most people, the radial artery contributes mainly to the deep palmar arch and therefore to the blood supply of the thumb and the radial side of the index finger

Question 64

Which nerves supply the hand?

Answer 64

There are three branches of the brachial plexus that supply motor and sensory function to the hand. These are the median, radial and ulnar nerves

Question 65

What are the intrinsic muscles of the hand supplied by?

Answer 65

The ulnar nerve supplies all of the intrinsic muscles of the hand except for a few.
These exceptions are supplied by the median nerve and can be recalled using the mnemonic LOAF:
 Lumbricals – radial (lateral) two lumbricals
 Opponens pollicis
 Abductor pollicis brevis
 Flexor pollicis brevis (superficial head; the deep head is supplied by the ulnar nerve)

Question 66

Why is the nailbed and dorsal skin overlying the distal phalanx of each finger innervated by the nerve that innervates the palmar aspect?

Answer 66

In the embryo, fingernails initially develop on the volar aspect of the hand and are dragged over to the dorsal aspect. As they migrate, they take their nerve supply with them.

Question 67

What is the nerve supply to the palm of the hand derived from?

Answer 67

derived from the palmar cutaneous branch of the median nerve, which arises proximal to the carpal tunnel, and the palmar cutaneous branch of the ulnar nerve which arises proximal to Guyon’s canal

Question 68

Describe the palmar digital branches of the median and ulnar nerves

Answer 68

The palmar digital branches of the median and ulnar nerves branch from their respective nerves (median nerve and superficial branch of the ulnar nerve) in the
palm. The palmar digital branches of the median nerve supply the thumb, index finger, middle finger and radial border of the ring finger. The palmar digital branches
of the ulnar nerve supply the ulnar border of the ring finger and the little finger. They also innervate the dorsum of these digits over the distal phalanx and nail bed.

Question 69

decribe the dorsal cutaneous branch of the ulnar nerve

Answer 69

The dorsal cutaneous branch of the ulnar nerve branches from the main nerve in the forearm and supplies the skin over the dorsal aspect of the ulnar border of the hand and the skin over the dorsum of the ulnar 1½ digits, as far distally as the distal interphalangeal joint (DIPJ).

Question 70

Where do you test sensation of the peripheral nerve territories?

Answer 70

As with the dermatomes, there is some overlap between the cutaneous territories of the peripheral nerves. Hence it is important to always test sensation in those regions known to have a consistent supply:
 Radial nerve: dorsum of the first webspace
 Median nerve: palmar surface of the tip of the index finger
 Ulnar nerve: ulnar border of the hand