Forearm muscles - posterior compartment Flashcards
How many layers in the posterior/extensor compartment?
- Superficial layer (7)
- Deep layer (5)
What muscles are in the superficial layer?
- Brachioradialis (note: flexor)
- Extensor Carpi Radials Longus
- Extensor Carpi Radialis Brevis
- Extensor Digitorum
- Extensor Digiti Minimi
- Extensor Carpi Unlaris
- Anconeus
What are the muscles in the deep layer?
- Supinator
- Abductor Pollicis longus
- Extensor Pollicis brevis
- Extensor Pollicis longus
- Extensor Indices
What nerve innervates the posterior forearm?
Radial n
What are the primary actions of the posterior forearm muscles?
- Wrist extension
- Digit extension
- Supination
What common origin does the superficial group share?
Lateral epicondyle (except brachioradialis & extesnor carpi radials longus - supracondylar ridge of humerus)
What common origin does the deep layer share?
Either posterior ulna, radius or interosseous membrane.
Brachioradialis O, I & Function?
O: Humerus (supracondylar ridge)
I: Radius (proximal to styloid process)
F: Flex forearm
Extensor Carpi Radialis Longus O, I & function?
O: humerus (spracondylar ridge)
I: Base of 2nd metacarpal
Function:
1. Extend wrist
2. Radial deviate
3. Flex forearm (weak)
Extensor Carpi Radialis Brevis O, I & function?
O: lateral epicondyle via CET
I: base of 3rd metacarpal
Function:
1. Extend Wrist
2. Radial deviate
What muscles make the mobile wad?
Found in lateral compartment of arm:
1. Brachioradialis
2. ECRL
3. ECRB
Extensor digitorum O, I & function?
O: Lateral epicondyle via CET
I: Dorsal digital expansion ( distal & middle phalanges 2-5)
Function:
1. Extend wrist
2. Extend digits 2-5 at MCP, PIP & DIP Joints
3. Extend Forearm (weak)
Extensor Digiti Minini O, I & function?
O: Lateral epicondyle via CET
I: Dorsal digital expansion - distal & middle phalange of digit 5
Function:
1. Extend wrist
2. Extend digit 5 & MCP, PIP & DIP joints
3. Extend forearm (weak)
Extensor Carpi Ulnaris O, I & function?
O: lateral epicondyle via CET
I: base of metacarpal 5
Function:
1. Extend wrist
2. Ulnar deviate
3. Extend forearm (weak)
Anconeus O, I & function?
O: lateral epicondyle (NOT CET)
I: Olecranon + posterior surface of ulna
F: Weak extension of elbow
(helps triceps)
What is the dorsal digital expansion?
- triangular tendinous aponeurosis that wraps around the MCP joints and extends along proximal and middle phalanges across PIP & DIP Joints.
-FNC: pulls PIP & DIP joints into complete extension + flexion of MCP joint “TATA”
Supinator O, I & function? (2 origins)
O: Ulna (supinator crest) & lateral epicondyle
I: lateral radius
F: supination
Abductor Pollicis Longus O, I & function?
O: Ulna, Radius & interosseous membrane
I: Base of 1st metacarpal
Function:
1. Abduction of thumb @ CMC joint
2. Extension of thumb @ CMC joint
3. Radial deviation
Extensor Pollicis Brevis O, I & function?
O: Radius & interosseous membrane
I: base of proximal phalanx
Function:
1. Extend wrist
2. Extend thumb @ MCP joint
3. Radial deviation (weak)
Extensor Pollicis Longus O, I & function?
O: Ulna & interosseous membrane
I: Base of distal phalanx
Function:
1. Extend wrist
2. Extend thumb @ MCP & IP joints
3. Radial deviation (weak)
Extensor Indicis O, I & function?
O: Ulna
I: dorsal digital expansion - distal & middle phalanx of 2nd digit
Function:
1. Extend wrist
2. Extend digit 2 @ MCP, PIP & DIP joints
What makes up the borders or the anatomical snuff box & what can you find in it?
Borders:
Lateral: extensor pollicis brevis (inside) & Abductor pollicis longus (outside)
Medial: extensor pollicis longus
Inside:
1. Median n
2. Scaphoid
3. trapezium
What is golf elbow/ medial epicondylitis?
-tiny ruptures of CFT from forceful & repeated bending of wrists/fingers
-symptoms: tenderness & pain @ medial epicondyle made worst from flexing wrist
What is tennis elbow/ lateral epicondylitis?
-painful/tender CET from strain/overuse/direct bang
-symptoms: tenderness & pain @ lateral epicondyle
Damage to posterior cord of brachial plexus.. what nerves, muscles, movements, sensory & long term deficients?
NERVES:Posterior cord forms axillary & radial n.
M: thus, deltoid & teres minor + all posterior arm/forearm muscles affected.
MOVEMENTS:
1. loss of extension: elbow, wrist, fingers
2. Weakness in abduction & external rotation
3. Weakness in supination (biceps also supinates diff nerve)
Loss of sensation:
1. Lateral shoulder
2. Posterior forearm
3. Lateral 3.5 digits
Long term deficits: wrist drop & deltoid atrophy
