part 4 forearm and hand

Question 1

Superficial forearm muscle

• name and from where
• major movement

Answer 1

Superficial forearm flexors are from medial epicondyle.
4+1
1. Pronator teres (pronation)
2. Flexor carpi radialis (flex wrist)
3. Palmaris longus (flex wrist)
4. Flexor carpi ulnaris (flex wrist)
-------------
5. Flexor digitorum superficialis (split and attach to middle phalanges so flex digits EXCEPT DIP + assist wrist flex)

Question 2

Why can’t we pick up skin from palm easily?

Answer 2

Palmar aponeurosis

Question 3

Deep forearm muscle

Answer 3

Deep forearm flexors are from bones and interrosseous membrane.
2+1
1. Flexor pollicis longus (flex thumb + assist wrist flex)
2. Flexor digitorum profundus (flex 4 digits, all MCP, PIP DIP)
————-
3. Pronator quadratus (pronation)

Question 4

Why little finger extend more easily?

Answer 4

besides extensor digitorum, has an extra extensor digiti minimi

Question 5

Forearm extensor superficial muscle

Answer 5

3+2
extensor carpi radialis longus
extensor carpi radialis brevis
extensor carpi ulnaris 
---------
extensor digitorum
extensor digiti minimi (medial)

Question 6

Forearm extensor deep muscle

Answer 6

5
supinator
abductor pollicis longus
extensor pollicis brevis
extensor pollicis longus
extensor indicis

Question 7

Anatomical snuff box (landmark)

Answer 7

between extensor pollicis brevis and extensor pollicis longus
superficial radial nerve, radial artery, floor being scaphoid

Question 8

Where does brachioradialis attach to

Answer 8

styloid process of radius

Question 9

Flexion of elbow

Answer 9

BBB
biceps brachii
brachialis
brachioradialis (from mid-pron position)

Question 10

Where does flexor digitorum profundus tendon attach to ? what movement?

Answer 10

distal phalanges

since it is attached to distal p, it flexes all finger joints MCP, PIP, DIP

Question 11

Where does flexor digitorum superficialis tendon attach to and what movement?

Answer 11

middle phalanges (at the two sides coz it split)
so MCP PIP but not DIP

Question 12

which muscles are involved in supination

Answer 12

supinator and biceps contract

pronator quadratus and pronator teres relax

Question 13

Muscles for wrist extension/flexion

Answer 13

Wrist extention:
extensor carpi radialis longus + brevis
extensor carpi ulnaris
(extensor digitorum)
Flexion:
flexor carpi radialis
flexor carpi ulnaris 
(flexor digitorum profundus/superficialis)

Question 14

Muscles for wrist adduction/abduction

Answer 14

Wrist adduction:
Flexor carpi ulnaris
Extensor carpi ulnaris

Question 15

Loss of sensation on both dorsal and palmar side of the hand related to the medial 1.5 digits

Answer 15

medial 1.5 digits sensory by ulnar nerve
this area is innervated by dorsal cutaneous branch of ulnar nerve which branches out at 5cm proximal to the wrist.
so the damage of ulnar nerve happened at or between cubital tunnel and 5cm proximal to wrist

Question 16

Loss of sensation on palmar side of the hand related to the medial 1.5 digits but not the dorsal side

Answer 16

medial 1.5 digits sensory by ulnar nerve
ulnar nerve damage happened at the Guyon’s canal (not more than 5cm proximal to wrist) where palmer cutaneous branch comes out but dorsal cutaneous has already travelled to dorsal side

e.g. Cyclist’s pulsy = prolonged pressing,
 hook of halmate fracture 
pisiform damage
d, affect motor function and sensation loss of of digits

Question 17

How to test for median nerve injury and why?

Answer 17

Make a fist –> Hand of Benediction
Median nerve supplies most forearm flexor except flexor carpi ulnaris and medial half of flexor digitorum profundus.

If median nerve is damaged, only the two medial digits can flex when asked to make a fist as medial half of the flexor digitorum profundus is supplied by ulnar nerve instead.
The thumb, and lateral 2 digits cannot flex due to paralysis of flexor pollicis longus, flexor digitorum superficialis and lateral profundus.

Question 18

Where are the common sites for median nerve injury

Answer 18

1. nerve entrapment at pronator teres

2. compression at carpal tunnel

Question 19

What does median nerve innervate?

Answer 19

Forearm flexor:
except flexor carpi ulnaris and medial half of flexor digitorum profundus (by ulnar instead).
Hand:
Thenar muscles and lateral two lumbricals
Cutaneous:
3.5 palmer surface + 3.5 finger nails

Question 20

Median nerve block

Answer 20

Two sites:

1. Elbow joint: TAM
2. lateral to the palmaris longus tendon

Question 21

Structures within the carpal tunnel

Answer 21

1. Median nerve
2. tendon of flexor pollicis longus
3. tendon of flexor digitorum profundus and superficialis

Question 22

in the paralysis of thenar

what movement is lost and which nerve is responsible

Answer 22

abduction, flexion and opposition
median nerve supply thenar muscle, damaged in carpal tunnel syndrome
Ape hand
thenar atrophy (compare with the normal thenar)

Question 23

Carpal tunnel syndrome

Answer 23

median nerve is compressed but it has already sent out the palmar branch which runs above the tunnel –> innervates the skin over the base and central palm –> no sensation loss in palmar side

only the 3.5 finger tips lose sensation (numbness, tingling)

cannot pick things up, Ape hand cannot do opposition and finger tips can’t feel

Question 24

What causes hand of benediction?

Answer 24

flexor digitorum superficialis and lateral profundus are not working, they are innervated by median nerve originally,
so the damage must have occurred before it innervate flexor compartment (i.e. near elbow joint e.g. supracondylar fracture but not in Carpal tunnel syndrome)

Question 25

describe the course of radial nerve at the elbow joint

Answer 25

anterior to the lateral epicondyle, before spliting into deep and superficial branch. the radial nerve has sent out branches to brachioradialis and extensor carpi radialis longus. Deep branch pierce through the supinator muscle, goes to the back and become posterior interosseous nerve. superficial branch does not go to the back but continue to be underneath the brachioradialis

Question 26

which nerve is damaged in wrist drop

Answer 26

Radial nerve

cannot extend, nerve that supply extensor carpi ulnaris/radialis longus/bevis –> Radial nerve supply extensor muscle

Question 27

if radial nerve is damaged at ? site then no wrist drop

Answer 27

below elbow at deep branch /posterior interosseous nerve (PIN)describe the branches coming from the radial nerve near elbow
because it has sent branches to supply the extensor carpi radialis longus, which can extend the wrist to prevent wrist drop

Question 28

Where to test for radial nerve loss

Answer 28

dorsal skin between 1st and 2nd metacarpel, least overlapping of nerve innervation more specific to radial nerve

Question 29

Where to do radial nerve block

Answer 29

1. lateral to TAM

2. next to the radial styloid

Question 30

Potential radial nerve injury

Answer 30

Deltoid injection
Compression (saturday night)
Shoulder joint dislocation
these are injuries high up, so cannot even extend tricep, wrist drop, finger drop, ;loss all sensation

Midshaft fracture: can extend tricep but wrist drop, finger drop

Dislocation or fracture of radial head or nerve entrapment in supinator damage deep branch –>