MSK > 23 - Forearm extensor compartment > Flashcards

23 - Forearm extensor compartment Flashcards

(46 cards)

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1
Q

What do I need to know?

A
  1. Muscle insertions, passage of tendon into wrist, MECHANISM of action
  2. Describe the actions of muscles during pronation/supination
  3. Disposition of radial nerve
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2
Q

What is this compartment important for?

A
  • 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
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3
Q

In what position of the wrist do the digit flexors get the most power?

A

Slightly extended

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4
Q

Where are the extensor muscles?

A

All are posterior EXCEPT brachioradialis which is anterior laterally and actually FLEXES the elbow even though is in the extensor compartment

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5
Q

What group does anconeus belong to?

A

Extensor forearm even though aids triceps in ELBOW extension (posterior lateral epicondyle/common extensor tendon to ulna)

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6
Q

How many extensor muscles are there and how can you classify them?

A 
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)
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7
Q

3 muscles that act on the wrist and where do they insert?

A

Extensor Carpi Radialis Longus > Base of 2nd MC
Extensor Carpi Radialus Brevis > Base of 3rd MC
Extensor Carpi Ulnaris > Base of 5th MC

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8
Q

3 muscles that act on the thumb and where do they insert?

A

-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

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9
Q

3 muscles that act on the fingers and where do they insert?

A
  • Extensor Digitorum
  • Extensor Indices
  • Extensor Digiti Minimi
    > all digit extensors insert at the dorsal digital expansion hood of respective digit
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10
Q

3 muscles that act on the forearm, what do they do and where do they insert?

A
  • Supinator > Supinates > Radial Tuberosity
  • Anconeus > posterior ulna proximally > extends elbow
  • Brachioradialis > Anterior radius > Flexes elbow
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11
Q

What are the superficial muscles and where are there inserts?

A

7 (from lateral to medial)

  1. Brachioradialis - lateral radius
  2. Anconeus - posterior ulna/olecranon
  3. ECRL - Base of 2nd MC
  4. ECRB - Base of 3rd MC
  5. ED - dorsal digital expansion hood of all 4 fingers
  6. EDM - dorsal digital expansion hood of DM
  7. ECU - Base of 5th MC
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12
Q

What muscles run from the common extensor tendon?

A

ECRB, ED, EDM, ECU

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13
Q

What muscles run from the lateral supracondylar ridge?

A

Anconeus and ECRL

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14
Q

Brachioradialis?

A
  • lateral humerus to lateral radius anteriorly

- shunt muscle to stop radial dislocation when you pile on heavy loads

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15
Q

Extensor Retinaculum?

A

Is arranged in compartments NOT a tunnel like flexor

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16
Q

What are the deep muscles of the extensor compartment and where do they insert?

A 
5 (lateral to medial and superior to inferior)
1. Supinator > Radial Tuberosity
2. 
3.
4.
5.
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17
Q

What are the deep muscles of the extensor compartment and where do they insert?

A

5 (lateral to medial and superior to inferior)

  1. Supinator > Radial Tuberosity
  2. Abductor Pollicis Longus > base 5th MC
  3. Extensor Pollicis Brevis > distal phalynx
  4. Extensor Pollicis Longus > prox phalynx
  5. Extensor Indices > DDEH of index finger
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18
Q

What does Extensor Digitorum have that the other muscles don’t?

A

Intertendinous Bands - stop oversplaying of of ED tendons

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19
Q

What is the purpose of the Dorsal Digital Expansion Hood?

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A

Extensor tendons insert and also stops the extensor tendons slipping out the SIDE of the hand

20
Q

Where would you find ECRL AND ECRB?

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A

Laterally BEHIND brachioradialis

21
Q

Anconeus?

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A
  • Lateral epicondyle > posterior ulna

- extends elbow

22
Q

ECRL?

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A

O: Supracondylar Ridge
I: 2nd MC
> extends wrist

23
Q

ECRB?

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A

O: Common extensor tendon
I: 3rd MC
> extends wrist

24
Q

Deep muscles from lateral and superior to middle and inferior?

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A
  • Supinator
  • Abductor Pollicis Longus
  • Extensor Pollicis BREVIS
  • Extensor Pollicis LONGUS
  • Extensor Indices
25
Nerve to posterior arm?
Radial
26
Superficial muscles form lateral to medial?
- Brachioradialis - Anconeus - ECRL - ECRB - Extensor Digitorum - Extensor Digiti Minimi - Extensor Carpi Ulnaris
27
Extensor Digitorum?
O: Common Extensor Tendon I: DDEH of 4 fingers > extends wrist and fingers
28
Extensor Digiti Minimi?
O: Common Extensor Tendon I: DDEH of index
29
Extensor Carpi Ulnaris?
O: Common Extensor Tendon I: Base of 5th MC
30
Abductor Pollicis Longus?
O: Medial ulna, interosseous membrane, radius I: Base of 1st MC (highly mobile carpo-metacarpal joint) and often trapezium > thick often split tendon
31
Extensor Pollicis BREVIS?
O: Medial ulna, interosseous membrane, radius I: proximal phalynx of thumb > thin tendon compared to AbPL
32
Extensor Pollicis Longus
O: Medial ulna, interosseous membrane, radius I: Distal phalynx of thumb > crosses and affects 3 joints
33
Extensor Indices?
O: Medial ulna, interosseous membrane, radius I: DDEH of index finger > enables you to pinch things
34
Borders of anatomical snuffbox?
Lateral: EPB and AbPL Medial: EPL Superiorly: ECRL
35
What is in anatomical snuffbox?
Scaphoid and Radial Artery
36
How many carpi muscles are there and where are they located?
5 (FCU/FCR/ECU/ECRL/ECRB) with tendons located at the corners of the wrist
37
Why are there 2 extensor carpi radialis muscles?
to oppose the thumb. When you flex the thumb alone, the tendon also crosses the wrist joint so tries to flex this too. These extensors hold the wrist in place during thumb flexion
38
How do you get pure wrist flexion or extension?
The carpi muscle tendons are located at the corners of the wrist so if fired alone they would pull on an angle and BOTH flex/extend AND abduct/adduct. In order to get a pure movement you need to fire BOTH flexor/extensor carpi muscles at both corners of the wrist
39
Why are the extensors needed?
- flexor muscles operate at an optimal length and this is when the wrist is slightly extended - NO strength when the wrist is flexed as are not at optimal length
40
What occurs during a midshaft fracture of the forearm?
- take out radial nerve - extensor muscles are taken out so can not lift the wrist so can't get optimal length for flexion and have no strength trying to pick things up (T-rex like) - results in wrist drop and decreased flexor EFFICIENCY
41
Why can you not independently extend middle and ring fingers?
Only have extensor tendons by ED which are all connected by intertendinous bands so when ED contracts it tries to extend all fingers. > Index and minimi have own extensors the BYPASS the bands
42
Describe how supinator inserts
FOLDED PIECE OF PAPER - folded bit wraps around radius and INSERTS at anterior radial tuberosity superficial head (superior): Posterior lateral epicondyle of humerus deep head (inferior): Back of radial notch and annular ligament of ulna
43
How does pronation and supination occur?
Pronation: Internally rotate radius so distal end comes over ulna. The radial tuberosity then rotates medially and disappears between the 2 bones Supination: Biceps and supinator insert at/near radial tuberosity. When they contract they pull it and externally rotate the radius distally over the ulna
44
What muscles are outcropping muscles?
Abductor Pollicis Brevis and Extensor Pollicis Brevis (lat border of snuff.) stick out laterally and cover the tendons of 2 superficial muscles ECRL and ECRB in order to get to the thumb
45
Through which muscle does the RADIAL nerve run in the forearm?
> runs laterally with medial head of triceps then between brachioradialis and brachialis > Through supinator laterally posteriorly and divides > Deep radial nerve runs between the 2 heads of supinator and re-enters the posterior compartment after going anteriorly round lateral epicondyle > Superficial branch is CUTANEOUS and runs under brachialis and around supinator
46
What branches/parts of the radial nerve supply what?
``` Radial (4) - triceps - anconeus - ECRL - brachioradialis Deep Branch (2) - ECRB - Supinator Posterior Interosseous N (6) - ED - EDM - EI - AbPL - EPB - EPL ```
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