L7: Musculo-neuro-vascular systems of arm and glenohumeral joint

Question 1

scapulohumeral (shoulder) muscles

Answer 1

Rotator cuff:
- supraspinatus
- infraspinatus
- teres minor
- subscapularis

Deltoid
teres major

Question 2

Rotator cuff

Answer 2

Supraspinatus
Infraspinatus
Teres Minor
Subscapularis

Together, their tendons form a sheath as they insert onto the proximal humerus (greater and lesser tubercles)
Active stabilisers of the glenohumeral joint

Question 3

supraspinatus; origin + insertion

Answer 3

origin: supraspinous fossa of scapula

insertion: greater tubercle of humerus ( superior facet)

Question 4

Supraspinatus; innervation + actions

Answer 4

innervation: suprascapular nerve [C5,6] from superior trunk

actions: abducts arm 0-15, assists deltoid with abduction from 15-90

Question 5

rotator cuff tear [especially supraspinatus] common in:

Answer 5

overhead athletes

Question 6

Infraspinatus; origin + insertion

Answer 6

origin: infraspinous fossa of scapula

insertion: greater tubercle of humerus (middel facet)

Question 7

Infraspinatus; innervation + actions

Answer 7

innervation: suprascapular nerve [C5,6] from superior trunk

actions: externally rotates arm at GH joint

Question 8

suprascapular nerve

Answer 8

Origin: C5, C6
Course:
*Arises from superior trunk of brachial plexus
*Passes inferiorly through the scapular notch into the supraspinous fossa innervates supraspinatus
*Curves around the spine of the scapula entering the Infraspinous fossa > innervates infraspinatus

Structures innervated:
*Supraspinatus
*Infraspinatus
*Glenohumeral joint

Question 9

Teres minor; origin + insertion

Answer 9

origin: infraspinatus fossa (inferior to infraspinatus)

insertion: greater tubercle of humerus (inferior facet)

Question 10

Teres minor; innervation + actions

Answer 10

innervation: axillary nerve C5

actions: external rotation of humerus at GH joint, adduction of the GH joint

Question 11

axillary nerve

Answer 11

Origin: Terminal branch of posterior cord (C5, C6)
Course:
*Passes laterally through quadrangular space reaching the posterior of the surgical neck
*Quadrangular Space Borders:
*Teres Minor
*Surgical Neck (Humerus) *Teres Major
*Long head of triceps

Structures innervated:
*Glenohumeral joint
*Teres minor
*Deltoid muscles
*Skin of superolateral arm

Question 12

Subscapularis; origin + insertion

Answer 12

origin: subscapular fossa of scapula

insertion: lesser tubercle of humerus (anterior)

Question 13

Subscapularis; innervation + actions

Answer 13

innervation: upper and lower subscapular nerves from posterior cord (C5,C6)

actions: internal rotation of humerus at GH joint, stabilises GH joint

Question 14

Subscapularis tear results in:

Answer 14

weak internal rotation of the humerus

Question 15

subscapular nerve

Answer 15

Origin: Posterior cord
Upper: C5
Lower: C6

Course:
*Upper: passes posteriorly to enter subscapularis directly
*Lower: Passes inferolaterally, deep to subscapular artery and vein

Structures innervated:
*Subscapularis (Upper and Lower)
*Teres major (Lower)

Question 16

rotator cuff tears

Answer 16

Tears of one or more rotator cuff tendons
Supraspinatus most frequently injured
Acute (sudden, powerful movement) tear
Chronic (tendon rubs against bone) tearing
MRI of joint might show tendon tear
Operative/non-operative treatment

Question 17

deltoid; origin + insertion

Answer 17

overlies rotator cuff

origin: lateral 1/3 clavicle, acromion, lateral 1/3 spine of scapula

insertion: deltoid tuberosity on humerus

Question 18

deltoid; innervation + action

Answer 18

innervation: axillary nerve [C5,C6]

actions on GH joint: anterior fibres; flexion, middle fibres; abduction, posterior fibres; extension

Question 19

Teres major; origin + insertion

Answer 19

origin: inferior 1/3 of lateral border of scapula

insertion: medial lip of bicipital groove (intertubercular sulcus)

Question 20

Teres major; innervation + actions

Answer 20

innervation: lower subscapular nerve [C5,C6]

actions on GH joint: internal rotation, adduction, extension

Question 21

quadrangular space syndrome

Answer 21

Repeated injury and subsequent scar tissue formation (fibrosis) can reduce the size of quadrangular space
Compression of the axillary nerve as it passes through the quadrangular space
Shoulder pain and paraesthesia in distribution of axillary nerve
Weakness of muscles innervated by axillary nerve.
NB: Over the shoulder athletes at risk

Question 22

shoulder impingement

Answer 22

During glenohumeral abduction, the supraspinatus tendon or its overlying subacromial bursa can be “impinged” between the head of the humerus and the inferior surface of the acromion.
If this happens repeatedly, the tendon can become inflamed “tendonitis”, or the bursa can become inflamed “subacromial bursitis’’

Patients with shoulder impingement usually have Painful Arc Syndrome.

Question 23

painful arc syndrome

Answer 23

Pain during shoulder abduction, but only within a specific range
Usually 60-120°
Why?
Because this is when the inflamed supraspinatus tendon or bursa becomes pressed between the head of the humerus and the acromion of the scapula

Question 24

arterial blood supply - GH joint

Answer 24

• anterior and posterior circumflex humeral arteries from the axillary artery
• suprascapular artery (branch of thyrocervical trunk from subclavian)

Question 25

arterial blood supply - acromioclavicular joint

Answer 25

- suprascapular artery - acromial branch of thoracodorsal artery, axillary artery

Question 26

arterial blood supply - supraspinous fossa

Answer 26

suprascapular artery

Question 27

arterial blood supply - infraspinous fossa:

Answer 27

dorsal scapular, thoracodorsal and circumflex scapular arteries

Question 28

arterial blood supply - subscapular fossa:

Answer 28

anastomosis between subscapular and thoracodorsal arteries with transverse cervical and dorsal scapular arteries

Question 29

venous drainage of GH joint & shoulder region

Answer 29

Axillary Vein: 3 divisions like axillary artery 1.Proximal to pectoralis minor 2.Deep to pectoralis minor 3.Distal, between lower border of pectoralis minor and lower border of teres major Formed by union of basilic vein and the brachial veins. Proximally it also receives the cephalic vein. Receives venous tributaries that generally correspond to axillary counterparts with some exceptions – don’t worry about these.

Question 30

arm compartment: muscles

Answer 30

anterior compartment: flexors - biceps brachii - brachialis - coracobrachialis posterior compartment: extensors - triceps brachii - anconeus - the 2 compartments separated by intermuscular septa: a connective tissue partition between muscles

Question 31

biceps brachii; origin + insertion

Answer 31

origin: long head; supraglenoid tubercle short head; coracoid process of scapula insertion: radial tuberosity, bicipital aponeurosis and fascia of forearm

Question 32

Biceps brachii; innervation + actions:

Answer 32

innervation: musculocutaneous nerve [C5-7] actions(3 joints): flexes elbow, supinates forearm via radioulnar joint, weak GH flexor, long head weak GH abductor when arm is externally rotated, short head weak GH adductor

Question 33

biceps brachii

Answer 33

Long Head of biceps passes superiorly through bicipital groove Transverse Humeral Ligament forms a roof over this groove Long head of biceps then turns medially and pierces through the joint capsule of GH joint Then inserts onto supraglenoid tubercl

Question 34

brachialis; origin + insertion

Answer 34

origin: distal 1/2 of anterior surface of humerus insertion: ulnar tuberosity

Question 35

brachialis; innervation + actions

Answer 35

innervation [dual]: -musculocutaneous nerve [C5-C7] -in 20% of people, it also receives input from radial nerve (C5,C6) actions: flexes elbow joint main flexor of elbow joint Lies deep to biceps

Question 36

coracobrachialis; origin + insertion

Answer 36

origin: coracoid process of scapula insertion: antero-medial aspect of humeral midshaft

Question 37

coracobrachialis; innervation + actions

Answer 37

innervation: musculocutaneous nerve [C5-C7] actions: flexes arm at GH joint, adducts arm at GH joint, weak internal rotator of arm

Question 38

musculocutaneous nerve

Answer 38

Origin: Arises from lateral cord of brachial plexus and its fibres come from C5-C7. Course: *Lies lateral to axillary artery *Pierces and passes through coracobrachialis *Descends between biceps and brachialis *Emerges inferolateral at elbow and supplies elbow joint Continues as Lateral Cutaneous Nerve of the Forearm Structures innervated: *Muscles of anterior compartment of arm: Coracobrachialis, biceps brachii, brachialis *Skin of lateral aspect of forearm

Question 39

triceps brachii; origin + insertion

Answer 39

main muscle of the posterior compartment of arm, has 3 heads, medial head is deep to long and lateral heads. origin: long head; infraglenoid tubercle lateral head; posterior humerus (superior to radial groove) medial head: posterior humerus (inferior to radial groove) insertion: olecranon process of ulna and fascia of forearm

Question 40

triceps brachii; innervation + actions

Answer 40

innervation: radial nerve [C6-C8] actions: extends elbow joint, long head: weak adductor and extensor of GH joint

Question 41

anconeus; origin + insertion

Answer 41

origin: lateral epicondyle of humerus insertion: lateral part of olecrannon process of ulna, elbow joint capsule

Question 42

anconeus; innervation + actions

Answer 42

innervation: radial nerve [C7-T1] actions: extends elbow joint, tenses elbow joint capsule, so that it is not pinched by olecranon in olecranon fossa during elbow extension

Question 43

radial nerve

Answer 43

Origin: Larger terminal branch of posterior cord (largest branch of brachial plexus) form C5-T1 Course: *Lies posterior to axillary artery *Passes through triangular interval and descends inferolaterally within the radial groove of the humerus *Gives branches supplying triceps as it descends *In ~20% of people it also gives a branch to brachialis Continues as Posterior Cutaneous Nerve of the Forearm supplying dorsum of upper limb

Question 44

triangular interval; borders and contents

Answer 44

borders: humeral shaft, teres major, long head of triceps contents: radial nerve, profunda brachii

Question 45

triangular interval syndrome

Answer 45

weakness in muscles innervated by radial nerve and paraesthesia in sensory distribution of radial nerve

Question 46

radial nerve injury

Answer 46

Effect is dependent on what level the injury occurs Injury at axilla: *Triceps denervated, weak or absent elbow extension *Wrist drop due to denervated wrist extensors *Loss of cutaneous sensation in the areas that the radial nerve normally supplies Injury at humeral mid shaft: *Triceps still mostly functions *Wrist Drop due to denervated wrist extensors *Loss of cutaneous sensation in the areas that the radial nerve normally supplies

Question 47

median nerve

Answer 47

Origin: *Lateral root of median nerve: terminal branch of lateral cord (C6, C7) *Medial root of median nerve: terminal branch of medial cord (C8, T1) Course: *Lateral to axillary artery *Descends through arm adjacent to brachial artery *Crosses brachial artery from lateral to medial and lies medial to artery in cubital fossa Structures innervated: *Muscles of anterior forearm compartment *Thenar half of palm of hand *Palmar skin

Question 48

ulnar nerve

Answer 48

Origin: *Larger terminal branch of medial cord (C8, T1) Course: *Descends medial arm *Passes posterior to medial epicondyle of humerus *Descends ulnar aspect of forearm to hand Structures innervated: *Flexor carpi ulnaris *Ulnar half of flexor digitorum profundus *Intrinsic muscles of hand *Skin of hand medial to axial line of digit 4

Question 49

arterial supply to arm

Answer 49

Brachial artery is the continuation of axillary artery past lower border of teres major Relatively superficial, medial to biceps and superficial to coracobrachialis / brachialis At elbow, runs deep to biceps aponeurosis and divides into radial and ulnar arteries Relations *Median nerve crosses anteriorly over artery *Ulnar nerve is posteromedial to artery

Question 50

branches of brachial artery

Answer 50

1.Profunda Brachii *Profunda means “deep” in latin *This is the deep artery of the arm, supplying triceps and the humerus *Initially profunda brachii passes between long and medial heads of triceps *Then courses inferolaterally through radial groove very close to radial nerve *Terminates by dividing into Radial and Middle Collateral Arteries 2.Brachial artery gives off superior and inferior ulnar collateral arteries 3.Brachial artery terminates as radial and ulnar arteries which supply forearm

Question 51

venous drainage of arm (1)

Answer 51

Brachial Vein *Accompanies brachial artery but drains deoxygenated blood back towards heart *Sometimes appears as multiple small veins around brachial artery called venae comitantes *These may also be referred to as deep brachial veins Basilic Vein *Courses proximally along medial surface of superficial arm *About ½ way along arm, dives deep, piercing the brachial fascia and entering deep compartment of arm *Proximally, the basilic vein unites with the brachial vein and they drain proximally. Upon reaching the lower border of teres major this vein becomes known as the axillary vein

Question 52

venous drainage of arm (2)

Answer 52

Cephalic vein drains lateral superficial region of arm Courses proximally until it turns medially and runs in the deltopectoral groove *Groove between deltoid anterior fibres and pectoralis major At proximal deltopectoral groove, cephalic vein pierces through clavipectoral fascia and drains into axillary vein.