Posterior of the Thumb

Question 1

What does the extensor of the thumb approach?

Answer 1

Approach their attachments, they become long tendons passing on the radial side of the arm, forming the boundaries of the anatomical snuff box.

Question 2

What is an anatomical snuff box?

Answer 2

A shallow depression on the lateral aspect of the wrist when the thumb is extended fully.

Question 3

Answer 3

Question 4

What are the anatomical snuff box boundaries?

Answer 4

Medial border (1 tendon)- Tendon of the Extensor pollicis longus

Lateral Border (2 tendons)- Tendons of Abductor pollicis longus and Extensor pollicis brevis

Floor (2 carpal bones)- Scaphoid and Trapezium

Question 5

What artery can you feel pulsating on the floor of the anatomical snuff box?

Answer 5

Radial artery

Question 6

What is the innervation of the extensor pollicis longus, extesor pollicis brevis and abductor pollicis longus?

Answer 6

Posterior interosseous nerve

Question 7

What is the action of the extensor pollicis longus?

Answer 7

Extension of thumb

Question 8

What is the action of the extensor pollicis brevis?

Answer 8

Extension of proximal phalnx of thumb

Question 9

What is the action of the abductor pollciis longus?

Answer 9

Abducts the thumb at the wrist joint

Question 10

What is a distal forearm fracture?

Answer 10

Distal forearm fractures make up a large percentage of broken bones following a mechanical fall – e.g. hand stretched out to cushion impact.

These can be classified into different names according to their clinical findings on x-ray.

Question 11

What is a colles fracture?

Answer 11

This is a common fracture of the distal radius in which there is anterior displacement (movement) of the shaft of the radius on the distal aspect of the bone

This is known as a dinner fork deformity and is caused by falling onto an extended wrist

Question 12

What is a smiths frature?

Answer 12

Reverse of this, in which there is posterior displacement of the radius on the distal aspect of the bone.

This is cause by falling onto a flexed wrist, or by a direct blow to the forearm

Question 13

What are scaphoid fractures?

Answer 13

This has a similar mechanism of injury to a Colle’s fracture, but more often occurring in the elderly.
It is the most fractured carpal bone

The pain from this fracture is felt during palpation of the anatomical snuff box.

If left there is a risk of malunion of the bone, or avascular necrosis

The latter is due to bone death (necrosis), as on fracturing the bone, the blood supply from the radial artery has been interrupted