L7: Musculo-neuro-vascular systems of arm and glenohumeral joint Flashcards
scapulohumeral (shoulder) muscles
Rotator cuff:
- supraspinatus
- infraspinatus
- teres minor
- subscapularis
Deltoid
teres major
Rotator cuff
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
supraspinatus; origin + insertion
origin: supraspinous fossa of scapula
insertion: greater tubercle of humerus ( superior facet)
Supraspinatus; innervation + actions
innervation: suprascapular nerve [C5,6] from superior trunk
actions: abducts arm 0-15, assists deltoid with abduction from 15-90
rotator cuff tear [especially supraspinatus] common in:
overhead athletes
Infraspinatus; origin + insertion
origin: infraspinous fossa of scapula
insertion: greater tubercle of humerus (middel facet)
Infraspinatus; innervation + actions
innervation: suprascapular nerve [C5,6] from superior trunk
actions: externally rotates arm at GH joint
suprascapular nerve
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
Teres minor; origin + insertion
origin: infraspinatus fossa (inferior to infraspinatus)
insertion: greater tubercle of humerus (inferior facet)
Teres minor; innervation + actions
innervation: axillary nerve C5
actions: external rotation of humerus at GH joint, adduction of the GH joint
axillary nerve
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
Subscapularis; origin + insertion
origin: subscapular fossa of scapula
insertion: lesser tubercle of humerus (anterior)
Subscapularis; innervation + actions
innervation: upper and lower subscapular nerves from posterior cord (C5,C6)
actions: internal rotation of humerus at GH joint, stabilises GH joint
Subscapularis tear results in:
weak internal rotation of the humerus
subscapular nerve
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)
rotator cuff tears
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
deltoid; origin + insertion
overlies rotator cuff
origin: lateral 1/3 clavicle, acromion, lateral 1/3 spine of scapula
insertion: deltoid tuberosity on humerus
deltoid; innervation + action
innervation: axillary nerve [C5,C6]
actions on GH joint: anterior fibres; flexion, middle fibres; abduction, posterior fibres; extension
Teres major; origin + insertion
origin: inferior 1/3 of lateral border of scapula
insertion: medial lip of bicipital groove (intertubercular sulcus)
Teres major; innervation + actions
innervation: lower subscapular nerve [C5,C6]
actions on GH joint: internal rotation, adduction, extension
quadrangular space syndrome
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
shoulder impingement
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.
painful arc syndrome
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
arterial blood supply - GH joint
- anterior and posterior circumflex humeral arteries from the axillary artery
- suprascapular artery (branch of thyrocervical trunk from subclavian)
arterial blood supply - acromioclavicular joint
- suprascapular artery
- acromial branch of thoracodorsal artery, axillary artery
arterial blood supply - supraspinous fossa
suprascapular artery
arterial blood supply - infraspinous fossa:
dorsal scapular, thoracodorsal and circumflex scapular arteries
arterial blood supply - subscapular fossa:
anastomosis between subscapular and thoracodorsal arteries with transverse cervical and dorsal scapular arteries
venous drainage of GH joint & shoulder region
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.
arm compartment: muscles
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
biceps brachii; origin + insertion
origin:
long head; supraglenoid tubercle
short head; coracoid process of scapula
insertion:
radial tuberosity, bicipital aponeurosis and fascia of forearm
Biceps brachii; innervation + actions:
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
biceps brachii
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
brachialis; origin + insertion
origin: distal 1/2 of anterior surface of humerus
insertion: ulnar tuberosity
brachialis; innervation + actions
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
coracobrachialis; origin + insertion
origin: coracoid process of scapula
insertion: antero-medial aspect of humeral midshaft
coracobrachialis; innervation + actions
innervation: musculocutaneous nerve [C5-C7]
actions:
flexes arm at GH joint, adducts arm at GH joint, weak internal rotator of arm
musculocutaneous nerve
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
triceps brachii; origin + insertion
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
triceps brachii; innervation + actions
innervation: radial nerve [C6-C8]
actions: extends elbow joint, long head: weak adductor and extensor of GH joint
anconeus; origin + insertion
origin: lateral epicondyle of humerus
insertion: lateral part of olecrannon process of ulna, elbow joint capsule
anconeus; innervation + actions
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
radial nerve
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
triangular interval; borders and contents
borders: humeral shaft, teres major, long head of triceps
contents: radial nerve, profunda brachii
triangular interval syndrome
weakness in muscles innervated by radial nerve and paraesthesia in sensory distribution of radial nerve
radial nerve injury
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
median nerve
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
ulnar nerve
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
arterial supply to arm
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
branches of brachial artery
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
venous drainage of arm (1)
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
venous drainage of arm (2)
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.
