Myology of the Shoulder Myology 2 (HS 201) Lecture 2 Myology of the Shoulder

Scapular Ranges of Motion Each student should be able to describe and demonstrate the following movements: Scapular Elevation Scapular Depression Protraction Retraction Upward Rotation Downward Rotation

Humeral Ranges of Motion Each student should be able to describe and demonstrate the following movements: 1. Humeral Flexion 2. Humeral Extension 3. Humeral Abduction 4. Humeral Adduction 5. Humeral Lateral (External) Rotation 6. Humeral Medial (Internal) Rotation

Palpation of the shoulder Spine of the scapula: Prone; Lay your hand across the upper back and slide your fingers inferiorly until they roll over the superficial spine. Palpate from the root of the spine to the acromion process. Medial border: Prone; Place your partner’s hand on the small of the lumbar spine to lift the medial border. Follow the medial border superiorly and inferiorly. Inferior angle: Prone; With the patient’s hand still on the small of the back glide your fingers inferiorly until the scapula begins to raise superiorly and laterally. This is the inferior angle. Superior angle: Prone; Scoop the anterior shoulder with your hand and lift it off the table. Again locate the medial border and locate the superior angle approximately an inch superior to the root of the scapular angle. Lateral border: Prone; Again find the inferior angle and slide your fingers laterally in the direction of the axilla. Infraspinous and Supraspinous Fossa: Prone; Again find the scapular spine and move inferiorly placing you on the infraspinous fossa. Cross the scapular spine superiorly and your fingers will be on the supraspinous fossa. Subscapular Fossa: Side lying: Place your thumb at the middle of the lateral border. Slowly sink and curl your thumb into the surface of the fossa. With the other hand, move the scapula and arm so your thumb can sink in more easily. You may only sink in about an inch or two.

Palpation of the shoulder (cont.) Acromion process and AC joint: Sitting: locate the high point of the shoulder or find the scapular spine again and follow it laterally and superiorly to the acromion. Moving your fingers slightly anterior and inferior find the AC joint. Have the patient shrug their shoulders and feel the AC joint move. Clavicle and the sternoclavicular joint: Sitting; Find the acromion again and move your fingers medially and inferior to the shaft of the clavicle. Follow the clavicle to where it articulates with the manubrium. Again have the patient shrug the shoulders and feel the SC joint move. Coracoid Process: Sitting; Palpate the lateral half of the clavicle where it is concave. Move your fingers inferiorly about an inch or so and push in posteriorly. Deltoid tuberosity: Sitting; Locate the acromion again. Slide down the lateral aspect of the arm. When you reach the halfway point between the shoulder and elbow there is a small tuberosity on the lateral arm. Greater tubercle: Sitting; Again locate the acromion. Slide off the acromion inferiorly and laterally approximately one inch. Intertubercular groove: Sitting; From the greater tubercle, move your fingers anteriorly until it sinks into a narrow canal or groove. Lesser tubercle: Sitting; Still in the intertubercular groove internally rotate the patient’s humerus and you will feel your fingers raise slightly. This is the lesser tubercle.

6 Muscles that move the scapula Trapezius Levator Scapula Rhomboid Major Rhomboid Minor Pectoralis Minor Serratus Anterior

Trapezius O: EOP, Superior Nuchal Line, Nuchal ligament, and the SP of C7 through T12 I: Upper Traps: Lateral 1/3 of clavicle & Acromion Middle Traps: Spine of scapula and acromion Lower Traps: Root of the Spine of the scapula A: Upper Traps: Elevates, upwardly rotates, and retracts the scapula Middle Traps: Retracts the scapula Lower Traps: Depresses, upwardly rotates, and **Reversed muscle action: Bilaterally allows for extension of the neck. Unilaterally laterally flexes the neck to the same side and rotates to the opposite side. N: CN XI (Spinal accessory nerve) and posterior rami of C3 and C4

Levator Scapulae O: TP’s of C1 – C4 I: Medial border of the scapula, from the superior angle to the root of the spine of the scapula A: Elevates retracts, and downwardly rotates scapula. **Reversed muscle action: Bilaterally allows for extension of the neck. Unilaterally laterally flexes the neck to the same side and rotates the to the same side. N: Dorsal Scapular nerve

Rhomboid Major and Minor O: Rhomboid Major: Sp’s T2-T5 Rhomboid Minor: Sp’s C7-T1 I: Medial border of the scapula from the root of the spine of the scapula to the inferior angle of the scapula A: Retracts, elevates, and downwardly rotates the scapula. **Reversed muscle action: Unilaterally causes contralateral rotation of the trunk N: Dorsal scapular nerve

Pectoralis Minor O: Anterior borders of ribs # 3 through 5 I: Coracoid process of the scapula A: Protracts, Depresses, and downwardly rotates the scapula **Reversed muscle action includes elevation of the 3rd through 5th ribs N: Medial pectoral nerve

Serratus Anterior O: Outer borders of the 1st through 9th ribs I: Anterior surface of the entire medial border of the scapula A: (PUSS) Protracts, upwardly rotates, and stabilizes the scapula N. Long thoracic nerve (of Bell)

Muscles that move the humerus Supraspinatus Infraspinatus Teres Minor Subscapularis Rotator Cuff Muscles Deltoid Biceps Triceps Coracobrachialis Latissimus Dorsi Teres Major Pectoralis Major

Rotator Cuff Muscles Consists of the Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis (SITS) Called “Rotator Cuff” group because their tendons all conjoint to form a cuff across the greater and lesser tubercles of the humerus These muscles act as a group to stabilize the head of the humerus into the glenoid fossa during shoulder movement Their role as stabilizers are vital because the ligaments of the shoulder are very loose

Supraspinatus O: Supraspinous Fossa of the scapula I: Greater tubercle of the humerus A: Initiates abduction of the humerus N: Suprascapular Nerve

Infraspinatus O: Infraspinous Fossa of the scapula I: Greater tubercle of the humerus A: Lateral rotation and extension of the humerus N: Suprascapular Nerve

Teres Minor O: Upper lateral border of the scapula I: Greater tubercle of the humerus A: Lateral rotation and extension of the humerus N: Axillary Nerve

Subscapularis O: Subscapular Fossa I: Lesser tubercle of the humerus A: Medial rotation of the humerus N: Upper and lower subscapular Nerve

Deltoid O: Anterior Head: Lateral Clavicle Middle Head: Acromion process Posterior Head: Spine of scapula I: Deltoid tuberosity of the humerus A: The entire muscle is a powerful abductor of the arm Anterior Head: flexes, medially rotates and horizontally adducts the arm Middle Head: abducts the arm Posterior Head: extends, laterally rotates, and horizontally abducts the arm N: Axillary nerve

Biceps Brachii O: Long Head: Supraglenoid tubercle of the scapula Short Head: Corocoid process of the scapula I: Radial tuberosity A: Shoulder: Flexes the arm Elbow: Flexes the elbow and assists in supination when power is required. N: Musculocutaneous nerve

Triceps Brachii O: Long Head: Infraglenoid tubercle of the scapula Lateral Head: Posterior aspect of the shaft of the humerus (proximal ½) Medial Head: Posterior aspect of the shaft of the humerus (distal ½) I: Olecranon Process of the Ulna A: Shoulder: Extends the arm Elbow: Extends the elbow N: Radial nerve

Coracobrachialis O: Coracoid process of the scapula I: Medial aspect of the shaft of the humerus A: Flexes and adducts the arm N: Musculocutaneous nerve

Latissimus Dorsi O: Thoracolumbar aponeurosis, posterior sacrum, posterior iliac crest, lower 3 or 4 ribs, and inferior angle of the scapula I: Medial lip of the Bicipital Groove of the humerus A: Extends, medially rotates, adducts the arm (handcuff position) ** Reversed muscle action bilaterally causes anterior tilt of the pelvis. Unilateral contraction causes elevation of the pelvis, contralateral rotation of the trunk, and lateral deviation of the trunk. N: Thoracodorsal nerve

Teres Major “Twin to the Lats” O: Inferior lateral border of the scapula. I: Medial lip of the bicipital groove of the humerus A: Extends, medially rotates, adducts the arm (handcuff position) N: Lower subscapular nerve

Pectoralis Major O: Clavicular Head: Medial clavicle Sternal Head: Sternum and the upper costal cartilages I: Lateral lip of the bicipital groove A: Adduction, medial rotation, and horizontal adduction of the arm. The clavicular head also causes flexion of the arm. Secondarily depresses and protracts the scapula. **Reversed muscle action causes elevation of the trunk, lateral deviation, and ipsilateral rotation. N: Medial and Lateral Pectoral nerves