L9: Cubital fossa and Musculo-neuro-vascular systems of the posterior forearm Flashcards
cubital fossa; boundaries
triangular region anterior to elbow joint
Boundaries:
superior: imaginary line between medial and lateral epicondyles
medial: pronator teres (lateral border)
lateral: brachioradialis (medial border)
roof: fascia of forearm + bicipital aponeurosis
floor: overlies elbow joint capsule: biceps tendon [superficial], brachialis [deep], supinator [deep]
contents of cubital fossa
from lateral to medial
Really Need Booze To Be At My Nicest
Radial Nerve
Biceps Tendon
Brachial Artery
Median Nerve
extensor retinaculum
Similar to flexor retinaculum except located on dorsum of wrist
Extensor muscle tendons pass under it as they make their way to the hand
Prevents bowstringingof extensor tendons during wrist extension
Extensor tendons covered in synovial sheaths as they pass under retinaculum. Reduces friction during movement
posterior compartment of forearm (11)
> superficial muscles (6)
- brachioradialis
- extensor carpi radialis longus
- extensor carpi radialis brevis
- extensor carpi ulnaris
- extensor digitorum
- extensor digiti minimi
posterior compartment (11)
> deep muscles (5)
- supinator
- abductor pollicis longus
- extensor pollicis brevis
- extensor pollicis longus
- extensor indicis
- general rule*
posterior forearm innervation
posterior forer]arm muscles supplied by the posterior interosseous branch of the radial nerve
EXCEPT
- brachioradialis > supplied by radial nerve directly
- Extensor carpi radialis longus > supplied by radial nerve directly
general rule:
superficial muscles of posterior compartment
superficial muscles of posterior compartment are attached to the lateral epicondyle through the common extensor tendon
brachioradialis; origin + insertion
origin: proximal 2/3 of lateral supracondylar ridge
insertion: lateral surface of distal end of radius and styloid process
brachioradialis; innervation + actions
innervation: radial nerve directly
actions: when forearm is pronated, BR supinates forearm and flexes elbow. When forearm is supinated, BR pronates forearm
extensor carpi radialis longus; origin + insertion
origin: lateral supracondylar ridge
insertion: dorsal aspect of base of 2nd metacarpal
extensor carpi radialis longus; innervation + actions
innervation: radial nerve directly
actions: extends & abducts wrist at radiocarpal joint
extensor carpi radialis brevis; origin + insertion
origin: lateral epicondyle (common extensor origin)
insertion: dorsal aspect of base of 3rd metacarpal
extensor carpi radialis brevis; innervation + actions
innervation: posterior interosseous branch of radial nerve
actions: extends and abducts wrist at radiocarpal joint
extensor carpi ulnaris; origin + insertion
origin: lateral epicondyle (common extensor origin)
insertion: dorsal aspect of base of 5th metacarpal
extensor carpi ulnaris; innervation + actions
innervation: posterior interosseous branch of radial nerve
actions: extends & adducts wrist at radiocarpal joint
extensor digitorum; origin + insertion
origin: common extensor origin
insertion: dorsal aspect of base of middle and distal phalanges 2-5 [as a large extensor expansion]
extensor digitorum; innervation + actions
innervation: posterior interosseous branch of radial nerve
actions: extends digits 2-5 at proximal & distal interphalangeal joints. Extends wrist [radiocarpal joint]
tendons of extensor digitorum
Form an extensor expanse3 bands unite all 4 tendons over dorsal aspect of digits 2-5, proximal to the MCP joints (knuckles)
Restricts independent action of fingers
A single finger can remain fully flexed while 1 other is fully extended.
Fully flex your index finger, fully extend your little finger. Now try to fully flex or extend your other 2 fingersNote that you can’t! This is due to the intertendinous connections of the extensor expanse
insertions of extensor digitorum
At the distal end of the extensor digitorum tendons, the tendon flattens and forms an extensor expansion which has 3 bands
1 median band
*The median slip inserts into the dorsal aspect of the middle phalanx
2 outer bands
*The 2 outer slips reunite on the dorsal aspect of the distal phalanx
The proximal extensor expansion also inserts into the underlying MCP joint capsule
extensor digiti minimi; origin + insertion
origin: common extensor origin
insertion: dorsal aspect of digit 5, base of middle and distal phalanx
extensor digiti minimi; innervation + actions
innervation: posterior interosseous branch of radial nerve
actions: extends little finger at distal and proximal interphalangeal joints
supinator; origin + insertion
origin:
- deep head: supinator crest of ulna
- superficial head: common extensor tendon
supinator; innervation + actions
innervation: posterior interosseous branch of radial nerve
actions: supinates forearm
abductor pollicis longus; origin + insertion
origin: posterior ulna, interosseous membrane & ulna
insertion: lateral aspect of base of 1st metacarpal
abductor pollicis longus; innervation + actions
innervation: posterior interosseous branch of radial nerve
actions: extends & abducts thumb at CMC joint
extensor pollicis longus; origin + insertion
origin: posterior surface of middle third ulna and interosseous membrane
insertion: dorsal aspect of base of thumb distal phalanx
extensor pollicis longus; innervation + actions
innervation: posterior interosseous branch of radial nerve
actions: extends proximal and distal phalanges of thumb. Extends 1st MC joint
extensor pollicis brevis; origin + insertion
origin: posterior surface of distal radius and interosseous membrane
insertion: dorsal aspect of base of proximal phalanx of thumb
extensor pollicis brevis; innervation + actions
innervation: posterior interosseous branch of radial nerve
actions: extends proximal phalanx of thumb. Extends 1st MC joint
extensor indices; origin + insertion
origin: posterior surface of ulna and interosseous membrane
insertion: dorsal aspect of index finger (extensor expansion)
extensor indices; innervation + actions
innervation: posterior interosseous branch of radial nerve
actions: extends index finger
arterial supply to forearm
As brachial artery enters forearm deep to bicipital aponeurosis it bifurcates:
*Radial artery
*Ulnar arteryElbow joint supply: (anastomotic network)
*Superior and inferior ulnar collateral arteries anastomose with ulnar recurrent arteries
*Radial collateral artery anastomoses with radial recurrent arteries
forearm nerves
- median nerve and anterior interosseous branch
- ulnar nerve
- radial nerve and posterior interosseous branch
