Upper Limb

Shoulder Region

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Overview


The shoulder is a highly mobile joint which permits movement of the arm in several planes; flexion, extension, abduction, adduction, internal rotation, external rotation and circumduction. 

Several muscle groups enable this variety of movements. The most frequently discussed and examined is the rotation cuff. This is composed of four muscle; supraspinatus, infraspinatus, subscapularis and teres minor. In addition to contributing to the movements possible at the glenohumeral joint, these muscles provide additional "dynamic stability".

Gross Anatomy


There are 4 main muscles that make up the rotator cuff muscles; supraspinatus, Infraspinatus, Teres Minor and Subscapularis. Each of these insert onto the scapula and attach onto the humerus.

 The supraspinatus muscle originates at the medial two-thirds of the supraspinous fossa of the scapula and the deep fascia that covers the muscle and inserts onto the most superior facet on the greater tubercle of the humerus. The supraspinatus muscle is supplied by the suprascapular Artery and Circumflex Artery and their corresponding veins. It is innervated by the suprascapular nerve from C5-C6 of the brachial plexus. The supraspinatus initiates abduction of the arm to 15o at the glenohumeral joint.

The infraspinatus muscle originates at the medial two-thirds of the infraspinous fossa of the scapula and the deep fascia that covers the muscle and inserts onto the middle facet on the greater tubercle of the humerus. The infraspinatus muscle is supplied by the suprascapular artery and circumflex scapular artery and their corresponding veins. It is innervated by the suprascapular nerve from C5-C6 of the brachial plexus. The infraspinatus laterally rotates the arm at the glenohumeral joint and holds the humeral head in the glenoid cavity of the scapula.

The teres minor muscle originates at the upper two-thirds of a flattened bone on the posterior surface of the scapula immediately adjacent to the lateral border of the scapula and inserts onto the most inferior facet on the greater tubercle of the humerus. The teres minor is supplied by the subscapular artery and circumflex scapular Artery and their corresponding veins. It is innvervated by the axillary nerve from C5-C6 of the brachial plexus. The teres minor rotates the arm laterally at the glenohumeral joint.

The subscapularis muscle originates at the subscapular fossa of the scapula and inserts onto the lesser tuberosity of the humerus. The subscapularis muscle is supplied by the suprascapular artery and its corresponding vein. It is innvervated by the upper and lower subscapular nerves from C5, C6, C7 of the brachial plexus. The subscapularis medially rotates the arm, adducts the arm and holds the humeral head in the glenoid cavity of the scapular.



Clinical Anatomy


Supraspinatus

Empty Can Test – arms out in front with thumbs pointing down, resisting against downward force. Positive test – Weakness (and pain)

Infraspinatus and Teres Minor

External Rotation examination – Arms by their side, elbow flexed at 90o, actively externally rotated against resistance Positive test – weakness (and pain)

Lag Sign - Arms by their side in a neutral position, Supporting the elbow, passively externally rotate the arm, Release the hand. Positive test - Hand/Arm will rotate inwards/back to midline on it’s own

Subscapularis

Lift off Test – arm placed behind the back with the hand on the lumbar spine region. Ask the patient to lift their hand off their back against resistance of your hand.  Positive test – inability to lift the hand off the back.

Impingement

Painful Arc –Active/Passive abduction of the shoulder in the plane of the body. Positive test is where there is pain on active abduction between 60-120o

Neers Test – full flexion of the shoulder with a pronated hand and thumb pointing backwards Positive test is pain at any point. Measure the degree at which pain occurs.

Hawkin’s Kennedy Test – 90o flexion of glenohumeral joint and elbow. Actively internally rotate the arm. Positive test is if pain is elicited.

Painful arc testing is most useful when used in conjunction with the Neer and Hawkins-Kennedy tests and increases specificity.


Quick Anatomy


Key Facts

Origin

Insertion

Arterial Supply

Innervation

Function

Supraspinatus

Medial two-thirds of the supraspinous fossa of the scapula and the deep fascia that covers the muscle

Most superior facet on the greater tubercle of the humerus

Suprascapular Artery and Circumflex Artery

Suprascapular N. – C5 (C6)

Initiation of abduction of arm to 15o at glenohumeral joint

Infraspinatus

Medial 2/3 of the infraspinous fossa of the scapula and the deep fascia that covers the muscle

Middle facet on posterior surface of the greater tubercle

Suprascapular A and Circumflex Scapular Artery

Suprascapular Nerve (C5,C6)

Lateral rotation of the arm at the glenohumeral joint, hold humeral head in glenoid cavity of the scapula

Teres Minor

Upper 2/3 of a flattened strip of bone on the posterior surface of the scapula immediately adjacent to the lateral border of the scapula

Inferior facet on greater tuberosity of humerus

-          Subscapular and circumflex scapular art

Axillary N (C5,C6)

Lateral rotation of the arm at the glenohumeral joint

Teres Major

Elongate oval area on the posterior surface of the inferior angel of the scapula

 Medial lip of the intertubercular sulcus on the anterior surface of the humerus

Subscapular and circumflex scapular arts

 Inferior subscapular N. (c5,c6,c7)

Medial rotation and extension of the arm at the glenohumeral joint, adduction

Subscapularis

Subscapular fossa of the scapula

Lesser Tuberorsity of the humerus

Subscapular Artery

Upper and lower subscapular Nerves (C5, C6, C7)

Medial rotation of the arm, adduction of the arm, Holds humeral head in the glenoid cavity of the scapular.


Aide-Memoire



Summary


The supraspinatus muscle inserts onto the greater tubercle of the humerus and is involved in the initial abduction of the arm to 15o.  You can test its function using the ‘empty-can test’

The infraspinatus inserts onto the greater tubercle and externally rotates the arm. The lag test identifies any pathology in the infraspinatus muscle.    

The teres minor muscle inserts onto the greater tuberosity and externally rotates the arm. 

The subscapularis muscle is the only rotator cuff muscle that inserts onto the lesser tubercle. The subscapularis is involved in medial rotation of the arm, adduction and stability of the glenoid cavity. It can be tested by the lift-off test.    

References


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