Extensor Forearm and Dorsum of Hand

Question 1

Interosseus Membrane

Answer 1

• Dense CT
• Partially divides forearm into flexor and extensor compartments

Question 2

Antebrachial Fascia

Answer 2

• Deep fascia of the forearm

Question 3

Posterior Compartment

Answer 3

• Most originate via a common extensor tendon on lateral epicondyle
• Action: extensors of wrist
  
  • Except:
    
    • Brachioradialis: flexes elbow
    • Suppinator (wraps around head of radius)
• Innervation: Radial n.
  
  • ​Superficial branch (sensory)
  • Deep Branch/Posterior Interosseus (motor)
• Blood Supply:
  
  • Posterior Interosseus a.
  • Anterior interosseous a. (distal part)

Question 4

Brachioradialis

Answer 4

Innervation:

• Radial n.

Attachments:

• Humerus to distal radius

Action:

• Flexes elbow during pronation

Question 5

Extensor Carpi Radialis Longus

Answer 5

Innervation:

• Radial n.

Insertion:

• Base of 2nd metacarpal

Action:

• Extend and ABduct the wrist

Question 6

Extensor Carpi Radialis Brevis

Answer 6

Innervation:

• Radial n.

Insertion:

• Base of the 3rd metacarpal

Action:

• Extends and ABduct wrist

Question 7

Extensor Digitorum

Answer 7

Innervation:

• Radial n.

Action

• Extends all wrist and MP joints (digits 2-5)

Question 8

Extensor Digiti Minimi

Answer 8

Innervation:

• Radial n.

Insertion:

• Extensor expansion 5th digit

Action:

• Extends 5th digit

Question 9

Extensor Carpi Ulnaris

Answer 9

Innervation:

• Radial n.

Insertion:

• Base of 5th metacarpal

Action:

• Extend and ADduct wrist

Question 10

Supinator

Answer 10

Innervation:

• Radial n.

Action:

• Suppinates forearm

Question 11

Abductor Pollicis Longus

Answer 11

Innervation:

• Radial n.

Insertion:

• Base of 1st metacarpal

Action:

• Abducts thumb

Question 12

Extensor Pollicis Longus

Answer 12

Innervation:

• Radial n.

Insertion:

• Distal phalanx of thumb

Action:

• Extends thumb and wrist

Question 13

Extensor Pollicis Brevis

Answer 13

Innervation:

• Radial n.

Insertion:

• Proximal phalanx of thumb

Action:

• Extends thumb and wrist

Question 14

Extensor Indicis

Answer 14

Innervation:

• Radial n.

Insertion:

• Extensor expansion of 2nd digit

Action:

• Independently extends digit 2

Question 15

Anatomic Snuff Box

Answer 15

• Lateral side of wrist
• Bounded by tendons of:
  
  • Abductor pollicis longus
  • Extensor pollicis brevis
  • Extensor pollicis longus
• Radial a. travels through here
• Scaphoid bone forms floor

Question 16

Scaphoid Fracture

Answer 16

• Distal, Waist or Proximal fracture
  
  • Clinical Relevance: lose blood supply due to proximal fracture requires screw back together

Question 17

Lateral Forearm Cutaneous Innervation

Answer 17

• Lateral cutaneous nerve of forearm (continuation of musculocutaneous)

Question 18

Medial Cutaneous Innervation of Forearm

Answer 18

• Medial cutaneous nerve of forearm (from medial cord)

Question 19

Posterior Cutaneous Nerve of Forearm

Answer 19

• Superficial branch of radial n.

Question 20

Branches of Radial Nerve

Answer 20

Deep Branch of Radial:

• MOTOR
• After it pierces supinator is renamed posterior interosseous n.

Superficial Branch of Radial:

• Sensory only
• Deep to brachioradialis
• Lateral/dorsal hand

Question 21

Where is the radial n. prone to injury?

Answer 21

• Axilla
• Fracture shaft of humerus

Question 22

Where is deep branch of radial n. prone to injury?

Answer 22

• Fracture neck of radius
• Subluxation of head of radius (pierces supinator which wraps around head of radius)

Question 23

Where is superficial branch of radial n. prone to inury?

Answer 23

• Wound to forearm (through brachioradialis)

Question 24

Injury to deep branch of radial n.

Answer 24

• Problems:
  
  • Extending wrist
  • Abducting thumb
  • Extending thumb
  • Suppination

Question 25

Injury to superficial branch of radial n.

Answer 25

• Sensory loss to posterior/lateral hand

Question 26

What symptoms will you experience if you injure the radial n. in the cubital fossa or along the humeral shaft?

Question 27

What symptons will you experience if you injure the radial nerve in the axilla?