Axilla II, Brachial Plexus, Arm Flashcards
What would injury to the superior trunk of the brachial plexus (C5 + C6 roots) present as?
Paralysis of:
- Deltoid
- Supraspinatus
- Infraspinatus
- Teres minor
- Biceps
- Brachialis
- Brachioradialis
- Erb-Duchenne’s palsy
Presentation:
- ADducted shoulder joint (can’t ABduct)
- Medial rotation (can’t laterally rotate)
- Extended elbow (can’t flex forearm)
- Waiter’s tip position
Common causes of injury to the superior trunk of the brachial plexus
- Fall landing on shoulder/neck w/ hyperextension
- Delivery of baby by pulling on head + stretching neck,
What would injury to the inferior trunk of the brachial plexus (C8 + T1) present as?
Paralysis of:
- All small muscles of hand
Presentation:
- Fingers of hand are noticeably bent
- Claw hand
What is Erb-Duchenne’s palsy?
- Superior trunk lesion
- Involve C5 + C6 nerve roots
- Mechanism: Injuries that widely separate neck + shoulder
Walk through the components of the brachial plexus
5 Roots:
- C5, C6, C7, C8, T1
3 Trunks:
- Superior
- Middle
- Inferior
6 Divisions:
- Anterior (each)
- Posterior (each)
3 Cords:
- Lateral
- Medial
- Posterior
6 Branches:
- Musculocutaneous
- Median
- Ulnar
- Radial
- Axillary
What nerve branches off of nerve roots C5-C7?
Long thoracic nerve
What does the long thoracic nerve innervate?
Serratus anterior muscle
What 2 nerves immediately branch off of the C5 nerve root?
- Dorsal scapular
- Phrenic
What 2 nerves branch off of the superior trunk?
- Suprascapular
- Subclavius
What 3 nerves branch from the lateral cord?
- Lateral pectoral nerve
- Musculocutaneous nerve
- Median nerve (lateral root)
What 5 nerves branch from the medial cord?
- Median nerve (medial root)
- Ulnar nerve
- Medial pectoral nerve
- Medial brachial cutaneous nerve
- Medial antebrachial cutaneous nerve
What 5 nerves branch from the posterior cord?
- Upper subscapular
- Thoracodorsal
- Lower subscapular
- Radial
- Axillary
What structure are the brachial plexus cords named in relation to?
Axillary artery
What are some additional contributions to the brachial plexus outside of C5-T1?
- C4 to C5 (pre-fixed)
- T2 to T1 (post-fixed)
What is Klumpke’s palsy?
- Inferior trunk lesion
- Roots involved: C8 and T1
- Mechanism: Injuries that cause excessive abduction of the arm
Common causes of injury to inferior trunk of brachial plexus (C8 + T1)
- Hyperabduction of arm
- Pulling on prolapsed limb during baby delivery
Nerve avulsion
- Dorsal + ventral roots of spinal nerves are completely torn away from spinal cord
- No treatment available
Nerve rupture
- Spinal nerve is completely torn at intervertebral foramen
- No treatment available
Nerve praxis/stretch
- Spinal nerve is injured/damaged but not torn
- May heal on its own
Nerve neuroma
- Scar tissue developed around nerve as it heals
- Can be debrided
What would injury to the long thoracic nerve present as?
Inability to:
- Rotate scapula during ABduction
- Difficulty raising arm above head (brushing hair)
Presentation:
- Medial winging scapula
Primary scapular winging causes
- Dysfunction in one or more of the scapulothoracic stabilizers (serratus anterior, trapezius, rhomboids)
- Muscular imbalance in scapular alignment
Secondary scapular winging causes
- In association with other pathologies (subacromial bursitis, disorders of the glenohumeral joint)
How to test for medial scapular winging
- Arm flexion
- Push up motion against wall
How to test for lateral scapular winging
Superior angle laterally displaced:
- Arm ABduction
- External rotation against resistance
Inferior angle laterally displaced:
- Arm extension from full flexion
What would injury to the spinal accessory nerve present as?
Lateral winging scapula w/ superior angle displaced laterally
What would injury to the dorsal scapular nerve present as?
Lateral winging scapula w/ inferior angle displaced laterally
Median nerve palsy
Roots involved:
- C5-T1
Mechanism:
- Lacerations at the wrist
- Lacerations at the elbow
Paralysis of:
- All pronator + flexor muscles of wrist + fingers (except for FCU + medial half of FDP)
- 3 thenar muscles
Long thoracic nerve lesion/injury
Roots involved:
- C5, C6, C7
Mechanism:
- Injury during surgery (iatrogenic injury)
Paralysis of:
- Serratus anterior muscle
- Inability to rotate scapula during abduction
- Difficulty raising arm above head
What would median nerve palsy present as?
- Thenar atrophy
- Hand of papal benediction (after being asked to make a fist)
Radial nerve palsy
Roots involved:
- C5-T1
Mechanism:
- Fracture of the humerus
- Poorly-fitted crutches
- “Saturday night palsy” from drunkenness
Paralysis of:
- Extensors of wrist & fingers
What would radial nerve palsy present as?
Wrist-drop after patient is asked to lift hand + fingers
Ulnar nerve palsy
Roots involved:
- C7-T1
Mechanism:
- Fracture of the medial epicondyle
- Superficial cuts and stab wounds at the wrist
Paralysis of:
- 1 and 1/2 muscles in the forearm (FCU, medial half of FDP muscles)
- Hypothenar muscles, adductor pollicis muscle, all interosseous muscles
What would ulnar nerve palsy present as?
- Hypothenar atrophy
- Ulnar claw-like hand
- Unable to ABduct/ADduct fingers or thumb
- Unable to flex digits 4-5
Quick clinical test for axillary nerve
Abduct arm from 15-90 degrees
Quick clinical test for musculocutaneous nerve
Flex elbow
Quick clinical test for radial nerve
Extend wrist
Quick clinical test for median nerve
Bring thumb in opposition with base of little finger
Quick clinical test for ulnar nerve
ABduct + ADduct fingers (in anatomic plane)
Hill-Sachs lesion (or fracture)
- Cortical depression in posterolateral head of the humerus
- Results from forceful impaction of humeral head against anteroinferior glenoid rim when shoulder dislocates anteriorly
What would an anterior inferior shoulder dislocation present as?
- Axillary nerve palsy
- “Regimental badge” - assess supero-lateral arm for absence of sensory nerve
Weakness in:
- Abduction (15-90 degrees)
- Flexion
- Extension
- External rotation
Bankart lesion/fracture
Bony or cartilaginous fracture of anterior/inferior glenoid labrum
How does an anterior glenohumeral dislocation usually occur?
Forced external rotation in abduction (e.g., blocking volleyball strike)
What allows for blood supply to the arm if the axillary artery becomes compromised?
- Retrograde flow through collateral circulation made possible by arterial anastomoses occuring around the scapula
- Include dorsal scapular, suprascapular, subscapular nerves
Biceps brachii (origin + insertion)
Origin:
- Short head: Tip of coracoid process of scapula
- Long head: Supraglenoid tubercle of scapula
Insertion:
- Tuberosity of radius + antebrachial fascia via bicipital aponeurosis
Biceps brachii (function + innervation)
Function:
- Supinates forearm
- Flex forearm
- Weakly flex arm
Innervation:
- Musculocutaneous nerve (C6) (C5)
Brachialis (origin + insertion)
Origin:
- Distal 1/2 of anterior surface of humerus
Insertion:
- Tuberosity of ulna
- Coronoid process of ulna
Brachialis (function + innervation)
Function:
- Flex forearm
- “One action, one joint muscle”
Innervation:
- Musculocutaneous nerve (C6) (C5)
Coracobrachialis (origin + insertion)
Origin:
- Tip of coracoid process of scapula
Insertion:
- Middle 1/3 of medial surface of humerus
Coracobrachialis (function + innervation)
Function:
- Flex arm
- Adduct arm
Innervation:
- Musculocutaneous nerve (C6) (C5,C7)
Triceps brachii (origin + insertion)
Origin:
- Long head: infraglenoid tubercle of the scapula
- Lateral head: posterior surface of humerus superior to spiral groove
- Medial head: posterior surface of humerus inferior to spiral groove
Insertion:
- Proximal end of olecranon
Triceps brachii (function + innervation)
Function:
- Extend arm
- Extend forearm
Innervation: Radial nerve (C7, C8) (C6)
Anconeus (origin + insertion)
Origin:
- Lateral epicondyle of humerus
Insertion:
- Lateral surface of olecranon
Anconeus (function + innervation)
Function:
- Assist triceps in extension of forearm
- Prevents hyperextension of elbow
Innervation:
- Radial nerve (C7, C8, T1)
What are the ulnar + median nerves doing in the arm?
Nothing, they are just “nerves of passage”, passing through on the way to the forearm.
What nerve pierces the coracobrachialis muscle?
Musculocutaneous nerve
