Conference 5: Elbow, Wrist, Hand

Question 1

Describe the pathway of force transmission from hand to axial skeleton

Answer 1

1. scaphoid and lunate to radius 2. radius to ulna via the interosseous membrane (must be in supinated position when tendon is taut) 3. ulna (trochlear notch) to humerus (trochlea) 4. humeral head to glenoid fossa of the scapula 5. scapula to clavicle 6. clavicle to sternum

Question 2

Thinking about *force transmission* why is it particularly bad to try to catch yourself when falling? In other words, why should you not protonate your arm and try to catch yourself?

Answer 2

This relaxes the interosseous membrane and prevents the force from being transmitted from the radius to the ulna. Therefore the *proximal* radius can become weight-bearing (instead of the proximal ulna). This helps to explain the frequency of radial head and neck fractures.

Question 3

What artery and what bone can be palpated in the anatomical snuff box?

Answer 3

Radial artery and scaphoid bone

Question 4

What are the boundaries of the anatomical snuff box

Answer 4

The TENDONS of: Abductor pollicis longus Extensor pollicis brevis Extensor pollicis longus

Question 5

If the carpal tunnel is compressed (for whatever reason), why can you still feel your palm?

Answer 5

There is no sensory loss on the palm due to the fact that the palmar cutaneous branch of the median nerve does not go through the tunnel; the palmar cutaneous branch of the median nerve supplies the sensory innervation of the palm of the hand

Question 6

Difficulty / inability in opposing the thumbs is a sign of what?

Answer 6

median nerve lesion at wrist

Question 7

A median nerve lesion at wrist can have what manifestations?

Answer 7

inability to oppose thumbs weakness in simultaneous flexion of MP joints and extension of IP joints

Question 8

Answer 8

1. Hamate
2. Capitate
3. Trapezoid
4. Trapezium

the arrow points to the flexor retinaculum

Question 9

Answer 9

1. flexor retinaculum
2. Hamate
3. Capitate
4. Trapezoid
5. Trapezium

Note how much larger the trapezium is compared to the trapezoid in cross sectional view

Question 10

Name what this cavity is showing, then list the contents counterclockwise starting at the arrow at the distal ulnar side of the hand

Answer 10

This shows the carpal tunnel and its contents:

1. Flexor digitorum superficialis =median
2. Flexor digitorum profundus = median AND ulnar nerves
3. Flexor pollicis LONGUS = median
4. Median nerve

Question 11

Label this starting at the top righthand arrow and going clockwise

Answer 11

1. Humerus
2. Olecranon process
3. Coronoid process of the ulna
4. Ulna
5. radius
6. Neck of the raidus
7. Head of the radius
8. Capitulum

Question 12

What does the head of the radius articulate with?

Answer 12

THE CAPITULUM

think about head / caput

Question 13

talk about the coronoid process

Answer 13

sharp, triangular eminence of the ulna which projects from the anterior portion of the proximal ulna

the proximal surface forms the lower part of the trochelar notch

anterior surface allows brachialis muscle to attach

Question 14

Is the radial tuberosity proximal or distal compared to the neck of the radius?

Answer 14

it is more distal (further “down” toward the wrist

also remember that it is the attachment site of the biceps

Question 15

Where does the triceps insert

Answer 15

olecranon ?