Part 8: Posterior Compartment of the Forearm Flashcards
Brachioradialis origin, insertion, action and innervation
O: Upper 2/3 lat supracondylar ridge humerus
I: Base styloid process radius
A: Flexes elbow, weak pronation (to neutral)
N: Radial (5,6)
Extensor Carpi Radialis Longus origin, insertion, action and innervation
O: Lower 2/3 lat supracondylar ridge humerus
I: Posterior base 2nd MC
A: Extends and abducts wrist
N: Posterior interosseous n (branch of radial - C6,7)
Extensor Carpi Radialis Brevis origin, insertion, action and innervation
O: CEO
I: Posterior base 2nd MC
A: Extends and abducts wrist joint
N: Posterior interosseous n (branch of radial - C6,7)
Describe the common extensor origin
What arises from it?
smooth area in front of lateral epicondyle
ECRB, ED, EDM, ECU
Extensor digitorum origin, insertion, action and innervation
O: CEO
I: Extensor expansion of all 4 fingers
A: Extends fingers
N: PIN (branch of radial - C7,8)
Extensor digiti minimi origin, insertion, action and innervation
O: CEO
I: Extensor expansion of little finger (usually 2 tendons)
A: Extends little finger
N: PIN (branch of radial - C7,8)
Extensor carpi ulnaris origin, insertion, action and innervation
O: CEO and aponeurotic sheath ulna
I: Base 5th MC via groove ulnar styloid
A: Extends and Adducts at wrist
N: PIN (C6,7)
Aconeus origin, insertion, action and innervation
O: Lower lat epicondyle
I: Lateral side olecranon
A: Weak elbow extensor
N: Radial n (C7,8)
Supinator origin, insertion, action and innervation
O: Deep part - supinator crest and fossa of ulna
Superficial part - lat epicondyle and lat lig of elbow
I: Neck and shaft of radius
A: Supination (only acts alone in extended elbow)
N: PIN (C5,6) - passes between the two parts
Abductor Pollicis Longus origin, insertion, action and innervation
O: Upper post ulnar and radius and IOM
I: Base 1MC and trapezium
A: Abducts thumb
N: PIN (C7,8)
Extensor pollicis brevis origin, insertion, action and innervation
O: Lower 1/3 post radius and IOM
I: Base proximal phalanx
A: Extends MPCJ of thumb
N: PIN (C7,8)
Extensor pollicis longus origin, insertion, action and innervation
O: Middle 1/3 posterior ulnar and IOM
I: Base distal phalanx
A: Extends IPJ and MCPJ of thumb
N: PIN (C7,8)
Extensor Indicis origin, insertion, action and innervation
O: Lower post shaft of ulna and IOM
I: Extensor expansion of index finger
A: Extension of PIPJ and DIPJ of index finger
N: PIN (C7,8)
Describe the borders of the anatomical snuffbox
and bony floor
Ulnar side - EPL
Radial side - EPB and APL
Proximally radial styloid then scaphoid, trapezium and then base MC of thumb distally
Important structures in the anatomical snuffbox
radial artery
cephalic vein begins in snuffbox
Path of posterior interosseous nerve
Branch of radial at elbow, passes between deep and superficial supinator, appears in extensor compartment and goes over APL to IOM. Supplies muscles from CEO and deep muscles
Describe the extensor retinaculum
Ribbon band lies obliquely across distal extensor surface of wrist. Proximally attached near styloid process and distally to pisiform and triquetreum. Not attached to ulnar.
Extensor tunnel divided into 6 compartments.
