part 4 forearm and hand Flashcards
Superficial forearm muscle
- name and from where
- major movement
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)
Why can’t we pick up skin from palm easily?
Palmar aponeurosis
Deep forearm muscle
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)
Why little finger extend more easily?
besides extensor digitorum, has an extra extensor digiti minimi
Forearm extensor superficial muscle
3+2 extensor carpi radialis longus extensor carpi radialis brevis extensor carpi ulnaris --------- extensor digitorum extensor digiti minimi (medial)
Forearm extensor deep muscle
5 supinator abductor pollicis longus extensor pollicis brevis extensor pollicis longus extensor indicis
Anatomical snuff box (landmark)
between extensor pollicis brevis and extensor pollicis longus
superficial radial nerve, radial artery, floor being scaphoid
Where does brachioradialis attach to
styloid process of radius
Flexion of elbow
BBB
biceps brachii
brachialis
brachioradialis (from mid-pron position)
Where does flexor digitorum profundus tendon attach to ? what movement?
distal phalanges
since it is attached to distal p, it flexes all finger joints MCP, PIP, DIP
Where does flexor digitorum superficialis tendon attach to and what movement?
middle phalanges (at the two sides coz it split) so MCP PIP but not DIP
which muscles are involved in supination
supinator and biceps contract
pronator quadratus and pronator teres relax
Muscles for wrist extension/flexion
Wrist extention: extensor carpi radialis longus + brevis extensor carpi ulnaris (extensor digitorum) Flexion: flexor carpi radialis flexor carpi ulnaris (flexor digitorum profundus/superficialis)
Muscles for wrist adduction/abduction
Wrist adduction:
Flexor carpi ulnaris
Extensor carpi ulnaris
Loss of sensation on both dorsal and palmar side of the hand related to the medial 1.5 digits
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
Loss of sensation on palmar side of the hand related to the medial 1.5 digits but not the dorsal side
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
How to test for median nerve injury and why?
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.
Where are the common sites for median nerve injury
- nerve entrapment at pronator teres
2. compression at carpal tunnel
What does median nerve innervate?
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
Median nerve block
Two sites:
- Elbow joint: TAM
- lateral to the palmaris longus tendon
Structures within the carpal tunnel
- Median nerve
- tendon of flexor pollicis longus
- tendon of flexor digitorum profundus and superficialis
in the paralysis of thenar
what movement is lost and which nerve is responsible
abduction, flexion and opposition
median nerve supply thenar muscle, damaged in carpal tunnel syndrome
Ape hand
thenar atrophy (compare with the normal thenar)
Carpal tunnel syndrome
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
What causes hand of benediction?
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)
describe the course of radial nerve at the elbow joint
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
which nerve is damaged in wrist drop
Radial nerve
cannot extend, nerve that supply extensor carpi ulnaris/radialis longus/bevis –> Radial nerve supply extensor muscle
if radial nerve is damaged at ? site then no wrist drop
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
Where to test for radial nerve loss
dorsal skin between 1st and 2nd metacarpel, least overlapping of nerve innervation more specific to radial nerve
Where to do radial nerve block
- lateral to TAM
2. next to the radial styloid
Potential radial nerve injury
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 –>
