Joints - Wrist

Question 1

What structures are involved in the wrist joint?

Answer 1

Distally - Proximal row of carpal bones

Proximally - Distal end of radius and articular disc

Note: The ulna is not apart of the wrist joint. It articulates with the radius at the distal radioulnar joint.

The carpal bones provide a convex surface to articulate with the concave surface of the radius and articular disc.

Question 2

Joint capsule

Features?

Answer 2

Like any synovial joint, it is double layered.

It has a fibrous outer layer and a synovial membrane that secretes fluid for lubrication.

Question 3

Ligaments of the wrist

Answer 3

There are four ligaments per joint:

1) Palmar radiocarpal - palm side - passes from radius to both rows of carpal bones. Apart from stability, ensures supination of hand with forearm.
2) Doral radiocarpal - dorum of hand - passes from radius to both rows of carpal bones. Apart from stability, ensures of the hand with forearm.
3) Ulnar collateral - ulnar styloid process to triquetrium and pisiform. Prevents excessive lateral displacement.
4) Radial collateral - Radial styloid process to scaphoid and trapezium.

Question 4

Neurovascular supply of the wrist

Answer 4

Blood supply:

Dorsal and palmar branches from the ulnar and radial arteries.

Innervation:

1) Median nerve - anterior interroseous branch
2) Radial nerve - posterior interroseous branch
3) Ulnar nerve - deep and dorsal branches

Question 5

Movements of the wrist

Type of joint?

Answer 5

Type of synovial joint - condyloid joint

Movement is done by the muscle of the forearm.

1) Flexion - flexor carpi ulnaris, flexor carpi radialis, with assistance of the flexor digitorum superficialis.
2) Extension - extensor carpi radialis longus and brevis, extensor carpi ulnaris, with assistance of the extensor digitorum.
3) Adduction - extensor carpi ulnaris and flexor carpi ulnaris.
4) Abduction - abductor pollicis longus, flexor carpi, extensor carpi radialis longus, and brevis.

Question 6

Clinical relevance: scaphoid fracture

Answer 6

Occurs as a result of FOOH.

Charasteric of pain and tenderness of the anatomical snuffbox.

At risk of avascular necrosis after fracture, due to its ‘retrograde blood supply’, which enters at the distal end. Fracture at the middle of the scaphoid may interrupt blood supply to the proximal part of the scaphoid bone, rendering it avascular.

Patients are likely to develop osteoarthritis later in life.

Question 7

Clinical relevance: anterior dislocation of the lunate

Answer 7

Falling on dorsiflexed wrist. Hand is forced anteriorly, and compresses carpal tunnel, causing symptoms of carpal tunnel syndrome.

Causes paraesthesia in the sensory distribution of the median nerves and weakness of the the thenar muscles. Lunate fracture can also cause avascular necrosis.

Question 8

Clinical relevance: Colle’s fracture

Answer 8

Most common fracture of the wrist.

Cause by FOOH.

Radius fractures - distal fragment displaced posteriorly. Ulnar styloid process can be avulsed in most cases.

Causes ‘dinner fork deformity’.