23 - Forearm extensor compartment Flashcards
What do I need to know?
- Muscle insertions, passage of tendon into wrist, MECHANISM of action
- Describe the actions of muscles during pronation/supination
- Disposition of radial nerve
What is this compartment important for?
- extending fingers/thumb and wrist during release of grip or making a fist or facilitating the POWER grip
- EXCEPT BR and ECRL which pass in FRONT of the elbow so FLEX it
In what position of the wrist do the digit flexors get the most power?
Slightly extended
Where are the extensor muscles?
All are posterior EXCEPT brachioradialis which is anterior laterally and actually FLEXES the elbow even though is in the extensor compartment
What group does anconeus belong to?
Extensor forearm even though aids triceps in ELBOW extension (posterior lateral epicondyle/common extensor tendon to ulna)
How many extensor muscles are there and how can you classify them?
12 - classify by 4 lots of 3 3 act on wrist (carpi) 3 act on thumb (pollicis) 3 extend fingers 3 only act on the forearm (there is 7 superficial and 5 deep)
3 muscles that act on the wrist and where do they insert?
Extensor Carpi Radialis Longus > Base of 2nd MC
Extensor Carpi Radialus Brevis > Base of 3rd MC
Extensor Carpi Ulnaris > Base of 5th MC
3 muscles that act on the thumb and where do they insert?
-3 bones in the thumb and they all insert on 1
Abductor Pollicis Longus > Base of 5th MC
Extensor Pollicis Longus > Distal Phalynx
Extensor Pollicis Brevis > Proximal Phalynx
3 muscles that act on the fingers and where do they insert?
- Extensor Digitorum
- Extensor Indices
- Extensor Digiti Minimi
> all digit extensors insert at the dorsal digital expansion hood of respective digit
3 muscles that act on the forearm, what do they do and where do they insert?
- Supinator > Supinates > Radial Tuberosity
- Anconeus > posterior ulna proximally > extends elbow
- Brachioradialis > Anterior radius > Flexes elbow
What are the superficial muscles and where are there inserts?
7 (from lateral to medial)
- Brachioradialis - lateral radius
- Anconeus - posterior ulna/olecranon
- ECRL - Base of 2nd MC
- ECRB - Base of 3rd MC
- ED - dorsal digital expansion hood of all 4 fingers
- EDM - dorsal digital expansion hood of DM
- ECU - Base of 5th MC
What muscles run from the common extensor tendon?
ECRB, ED, EDM, ECU
What muscles run from the lateral supracondylar ridge?
Anconeus and ECRL
Brachioradialis?
- lateral humerus to lateral radius anteriorly
- shunt muscle to stop radial dislocation when you pile on heavy loads
Extensor Retinaculum?
Is arranged in compartments NOT a tunnel like flexor
What are the deep muscles of the extensor compartment and where do they insert?
5 (lateral to medial and superior to inferior) 1. Supinator > Radial Tuberosity 2. 3. 4. 5.
What are the deep muscles of the extensor compartment and where do they insert?
5 (lateral to medial and superior to inferior)
- Supinator > Radial Tuberosity
- Abductor Pollicis Longus > base 5th MC
- Extensor Pollicis Brevis > distal phalynx
- Extensor Pollicis Longus > prox phalynx
- Extensor Indices > DDEH of index finger
What does Extensor Digitorum have that the other muscles don’t?
Intertendinous Bands - stop oversplaying of of ED tendons