S9) The Wrist

Question 1

What is the wrist joint?

Answer 1

The wrist joint (aka radiocarpal joint) is a synovial joint in the upper limb, marking the area of transition between the forearm and the hand

Question 2

What are the structures forming the wrist joint?

Answer 2

• Distally – proximal row of the carpal bones (except the pisiform)
• Proximally – distal end of the radius and the articular disk

Question 3

Does the ulna form part of the radiocarpal joint?

Answer 3

No, it articulates with the radius at the distal radioulnar joint but is prevented from articulating with the carpal bones by the articular disk

Question 4

Describe the blood supply to the wrist joint

Answer 4

Arterial supply via branches of the dorsal and palmar carpal arches, which are derived from the ulnar and radial arteries

Question 5

Describe the innervation of the wrist joint

Answer 5

• Median nerve – anterior interosseous branch
• Radial nerve – posterior interosseous branch
• Ulnar nerve – deep and dorsal branches

Question 6

Identify the 4 ligaments which ensure the stability of the wrist joint

Answer 6

Question 7

Describe the location and function of the palmar radiocarpal ligament

Answer 7

• Location: anterior side of the hand, passes from the radius to both rows of carpal bones
• Function: increases stability, ensures the hand follows the forearm during supination

Question 8

Describe the location and function of the dorsal radiocarpal ligament

Answer 8

• Location: posterior side of the hand, passes from the radius to both rows of carpal bones
• Function: increases stability of the wrist, ensures that the hand follows the forearm during pronation

Question 9

Describe the location and function of the ulnar collateral ligament

Answer 9

• Location: runs from the ulnar styloid process to the triquetrum and pisiform
• Function: prevents excessive medial joint displacement (in union with other collateral ligament)

Question 10

Describe the location and function of the radial collateral ligament

Answer 10

• Location: runs from the radial styloid process to the scaphoid and trapezium
• Function: prevents excessive lateral joint displacement (in union with other collateral ligament)

Question 11

What type of joint is the wrist joint?

Answer 11

The wrist is an ellipsoid type synovial joint, allowing for movement along two axes

Question 12

Identify the four different types of movement possible at the radiocarpal joint as well as the individual muscles involved

Answer 12

• Flexion – flexor carpi ulnaris and flexor carpi radialis (assistance from the flexor digitorum superficialis)
• Extension – extensor carpi radialis longus and brevis and extensor carpi ulnaris (assistance from the extensor digitorum)
• Adduction – extensor carpi ulnaris and flexor carpi ulnaris
• Abduction – abductor pollicis longus, flexor carpi radialis, extensor carpi radialis longus and brevis

Question 13

What is the carpal tunnel?

Answer 13

The carpal tunnel is a narrow passageway on the anterior portion of the wrist, serving as the entrance to the palm for several tendons and the median nerve

Question 14

Describe the borders of the carpal tunnel

Answer 14

• The deep carpal arch (formed by carpal bones) forms a concave surface acting as the floor
• The overlying superficial flexor retinaculum acts as the roof

Question 15

Identify the carpal bones forming the carpal arch laterally and medially

Answer 15

• Lateral: scaphoid and trapezium tubercles
• Medial: hook of hamate and pisiform

Question 16

State the structure and function of the flexor retinaculum

Answer 16

• Structure: thick connective tissue
• Function: turns the carpal arch into the carpal tunnel

Question 17

State the origin and attachment of the flexor retinaculum

Answer 17

• Origin: lateral side of carpal arch
• Attachment: medial side of the carpal arch

Question 18

Briefly describe the contents of the carpal tunnel

Answer 18

The carpal tunnel contains a total of 9 tendons, surrounded by synovial sheaths, and the median nerve

Question 19

Identify the different tendons found in the carpal tunnel

Answer 19

• The tendon of flexor pollicis longus
• Four tendons of flexor digitorum profundus
• Four tendons of flexor digitorum superficialis

Question 20

The synovial sheaths in the carpal tunnel allow free movement of the tendons.

How many are there?

Answer 20

• Tendons of the flexor digitorum profundus and flexor digitorum superficialis are surrounded by a single synovial sheath
• The tendon of flexor pollicis longus is surrounded by its own synovial sheath

Question 21

Describe the course of the median nerve once it passes through the carpal tunnel

Answer 21

Median nerve divides into 2 branches: recurrent branch and palmar digital branch

Question 22

Which structures do the palmar digital and recurrent branches of the median nerve innervate respectively?

Answer 22

• Palmar digital nerves give sensory innervation to the palmar skin and dorsal nail beds of the lateral 3½ digits and motor innervation to the lateral two lumbricals
• Recurrent branch supplies the thenar muscle group

Question 23

What is the anatomical snuffbox?

Answer 23

The anatomical snuffbox is a triangular depression found on the lateral aspect of the dorsum of the hand, at the level of the carpal bones

Question 24

Identify the different borders of the anatomical snuffbox as well as the structures forming them

Answer 24

- Medial border: tendon of extensor pollicis longus

• Lateral border: tendons of abductor pollicis longus and extensor pollicis brevis
• Proximal border: styloid process of the radius
• Floor: carpal bones; scaphoid and trapezium
• Roof: skin

Question 25

Identify the contents of the anatomical snuffbox

Answer 25

Question 26

Where can the radial pulse be palpated?

Answer 26

The radial pulse can be palpated in some individuals by placing two fingers on the proximal portion of the anatomical snuffbox

Question 27

What is De Quervain’s tenosynovitis?

Answer 27

• De Quervain’s tenosynovitis is a painful condition involving the inflammation of tendons on the side of the wrist at the base of the thumb
• These tendons include the extensor pollicis brevis and the abductor pollicis longus tendons, which extend the joints of the thumb

Question 28

How do we test for De Quervain’s tendosynovitis?

Answer 28

Finkelstein’s Test:

• Thumb is flexed across the palm and the fingers are then wrapped around it, the the wrist is passively adducted
• This causes a disproportionate amount of pain over the radial styloid on the affected side

Question 29

What is Carpal tunnel syndrome?

Answer 29

- Carpal tunnel syndrome is a condition involving the compression of the median nerve due to thickened ligaments and tendon sheaths

• It presents with numbness, tingling and pain along the distribution of the median nerve

Question 30

Describe the onset of the symptoms of Carpal tunnel syndrome

Answer 30

Sensations usually develop gradually and start off being worse during the night (diurnal variation of cortisol)

Question 31

How do we test for carpal tunnel syndrome?

Answer 31

• Tinel’s sign – tapping the nerve in the carpal tunnel to elicit pain in median nerve distribution
• Phalen’s manoeuvre – holding the wrist in flexion for 60 seconds to elicit numbness/pain in median nerve distribution

Question 32

What is Guyon’s canal syndrome?

Answer 32

- Guyon’s canal syndrome is a clinical condition caused by the entrapment of the ulnar nerve in the Guyon canal as it passes through the wrist

• It presents with paraesthesia in the ring and little fingers before progressing to a loss of sensation and/or impaired motor function of the intrinsic muscles of the hand

Question 33

Where is Guyon’s canal syndrome found?

Answer 33

Ulnar tunnel syndrome is commonly seen in regular cyclists due to prolonged pressure of the Guyon’s canal against bicycle handlebars