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Rotator Cuff Muscles (5)
- use acronym SITS
- Supraspinatus
- Infraspinatus
- Teres Minor
- Subscapularis: Upper & Lower
- muscles join to form a tendon that acts as a sleeve around the head of the humerus; rotates it medially or laterally or abducts it (supraspinatus specifically)
- all insert around head of humerus
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Subscapularis
- medially rotates the humerus
- a large triangular muscle that fills (originates in) the subscapular fossa (anterior part of the scapula) → crosses the shoulder joint anteriorly → inserts into the lesser tubercle of the humerus
 - supplied by the upper & lower subscapular nerves
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Upper & Lower Subscapular Nerves
- branches of the posterior cord
- supply the subscapularis muscle
- middle = thoracodorsal nerve (also known as), supplies latissimus dorsi
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Upper Middle & Lower Subscapular Nerves
- supply muscles in the posterior part of the axilla
- branch off of the Posterior cord (posterior divisions ← all 3 trunks)
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Supraspinatus Muscle
- initiates the abduction of the humerus (to the 1st 15o of elevation; then the deltoid takes over)
- originates in the supraspinous fossa of scapula
- → comes underneath the acromion → inserts on the superior part of the greater tubercle of humerus
- supplied by suprascapular nerve (from the superior trunk, C5 & C6 nerve roots)
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Infraspinatus Muscle
- rotates the humerus laterally
- originates on the posterior part of the scapula → crosses the shoulder joint posteriorly → inserts on the greater tubercle of the humerus
- supplied by suprascapular nerve (from superior trunk, C5 & C6 nerve roots)
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Teres Minor Muscle
- rotates the humerus laterally
- originates on the posterior part of the scapula → crosses the shoulder joint posteriorly → inserts on the greater tubercle of the humerus
- supplied by axillary nerve (from the posterior cord) – same nerve that supplies the deltoid
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What 3 muscles of the Rotator Cuff insert on the greater tubercle of the humerus?
- Supraspinatus, Infraspinatus, & Teres minor
- [the Subscapularis inserts on the lesser tubercle (tuberosity)]
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Where does blood supply to shoulder come from?
branches of both the subclavian & axillary arteries
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suprascapular & transverse cervical arteries originate off the__________ artery
- subclavian
- the suprascapular artery supplies the supra & infraspinatus
- the transverse cervical artery runs down the medial edge of the scapula then anastamoses w/ the suprascapular
- also have circumflex arteries
- the posterior circumflex humeral artery passes through the quadrangular space & anastamoses w/ the suprascapular
- the circumflex branch of the suprascapular artery also provides collateral circulation to the shoulder joint
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Glenoid Labrum
- a fibrocartilaginous rim that deepens the glenoid fossa, allows more contact btwn the head of the humerus & the socket glenoid fossa
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Gleno-humeral Ligament
- reinforces the shoulder joint anteriorly & prevents anterior displacement of the head of the humerus
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Subacromial (Subdeltoid) Bursa
- lies below the acromion & above the tendon of the Supraspinatus
- also 'spills' over to insert between the deltoid muscle & the humerus itself
- reduces friction on the Deltoid & Supraspinatus muscles
- bursa around the shoulder prevent wear & tear of the muscles as they pass over bones
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Subacromial Bursitis
- can happen in people who are constantly moving their arm
- pain & inflammation around the shoulder joint
- white = fluid buildup from inflammation
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Rotator Cuff Injuries
- tendons that are most COMMONLY injured are those of the Supra & Infraspinatus
- overuse of these tendons can lead to calcification, pain around the bursa → bursitis
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What is this depicting?
- right = a supraspinatus tear
- left = normal shoulder
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Frozen Shoulder (Adhesive Capsulitis)
- when the shoulder joint loses significant range of motion
- caused by tendinitis, bursitis, rotator cuff injury leading to inflammation, or thickening of tissues around shoulder joint
- symptoms: pain & stiffness
- treatment: anti-inflammatory injections & physical therapy
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Muscles in the Anterior Compartment of the Arm (3)
- 1. Biceps Brachii
- 2. Brachialis
- 3. Coracobrachialis
- these muscles FLEX the arm & forearm
- are all supplied by branches of the Musculotaneous nerve (comes off the lateral cord)
- (BBC)
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Biceps Brachii Muscle
- supinates & flexes the forearm
- has 2 heads: long head originates on the supraglenoid tubercle, runs down the intertubercular groove, & comes down on the lateral part of the arm
- the short head originates on the coracoid process, runs down more medially to form the muscle belly with the long head
- both form a tendon that crosses the elbow joint anteriorly & inserts on the radial tuberosity
- innervated by the Musculotaneous nerve (C5 & C6)
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Brachialis Muscle
- flexes the forearm at the elbow joint (assists the biceps in doing so)
- originates ~halfway down the shaft of the humerus → crosses the elbow joint anteriorly (deep to the biceps) → inserts on the ulnar tuberosity
- innervated by the Musculotaneous nerve (C5 & C6)
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Coracobrachialis Muscle
- MAIN flexor of the arm at the shoulder joint (flexes & abducts the humerus)
- originates off the coracoid process → crosses the SHOULDER joint anteriorly → then inserts on the humerus ~mid-shaft
- innervated by the Musculotaneous nerve (C5 & C6)
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Musculotaneous Nerve
- distinctive feature of this nerve is that it PIERCES the Coracobrachialis muscle, & gives motor branches to it, the Biceps Brachii, & the Brachialis muscles
- (those in the anterior compartment of the arm)
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What is the purpose of the Musculotaneous nerve after it provides motor innervation to the 3 muscles in the anterior compartment of the arm?
- it travels down to the lateral part of the forearm & is renamed the Lateral Cutaneous Nerve of the Forearm
- here (in the lateral forearm) it serves as a SENSORY nerve
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Biceps Tendon Rupture
- if someone tries to flex their forearm against a lot of resistance, that puts a lot of stress on the biceps (particularly the LONG head attached at the supraglenoid tubercle)
- too much will SNAP the tendon → large, painful bulge on the anterior part of the arm
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What structures can be found on the medial side of the Biceps Brachii muscle between it & the Triceps Brachii muscle?
- Median nerve
- Brachial artery
- Ulnar nerve
- the 3 structures run in a groove formed between the biceps & triceps – good place to palpate the Brachial artery pulse
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Biceps Tendon Reflex
- tests the integrity of the biceps brachialis & musculocutaneous nerve (C5,C6)
- use a rubber hammer to tap over the tendon of the biceps at the elbow joint → sensory nerves send a signal back to the spinal nerves, C5 & 6 especially → returns signal to the musculotaneous nerve, which flexes the forearm
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Muscles in the Posterior Compartment of the Arm (2)
- 1. Triceps Brachii
- 2. Anconeous
- are both supplied by the Radial nerve (comes off of the posterior cord of the brachial plexus)
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Triceps Brachii Muscle
- extends the forearm
- has 3 heads: long, lateral, & medial
- long head originates on the infraglenoid tubercle (below glenoid fossa)
- lateral head originates on the humerus shaft
- medial head originates on the posterior part of the humerus lower down
- all inserts at the olecranon of the ulna
- innervated by the Radial nerve (a branch of the posterior cord, C6, 7, & 8)
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Which head of the triceps crosses the shoulder joint?
- the LONG head
- can also help EXTEND the arm at the shoulder joint in addition to extending the forearm at the elbow joint
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Anconeus Muscle
- assists the triceps in extending the forearm
- innervated by the Radial nerve (C5, 6, & 7)
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Quadrangular, Triangular Spaces
- Medial Triangular Space
- Quadrangular Space
- Lateral Triangular Space
- if you look at the back of the shoulder, the muscles form quadrangular or triangular areas that important structures can pass through
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Medial Triangular Space
- x: Teres Major
- y: long head of triceps
- hypotenuse: Teres Minor
- circumflex branch of the subscapular artery passes through (provides collateral circulation around the shoulder joint)
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Quadrangular Space
- left: long head of triceps
- right: lateral head of triceps
- top: Teres Minor
- bottom: Teres Major
- AXILLARY nerve passes through from the axilla → winds around the upper shaft of the humerus → then supplies the deltoid & teres minor muscles
- posterior circumflex humeral artery takes the same path
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Lateral Triangular Space
- x: Teres Major
- y: lateral head of triceps
- hypotenuse: long head of triceps
- Radial nerve + the deep branch of the Brachial artery pass through this space
- note how these 2 structures travel together in the spiral groove of humerus
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Inferior Dislocation of the Humerus Head
- could damage the Axillary nerve & result in paralysis of the deltoid ((inability to abduct arm) & teres minor (partial loss of ability to laterally rotate arm)
- also a loss of sensation to the upper lateral part of arm (Axillary nerve itself)
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Mid-shaft Humeral Fracture
- can damage the radial nerve & deep brachial artery which run down the spiral groove
- this would paralyze the extensor muscles of the forearm leading to “Wrist Drop”
- unable to extend hand at the wrist/digits b/c the radial nerve would likely be damaged
- would also lose general sensation down the posterior part of the forearm & the dorsolateral part of the hand itself
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