Lab 6: Shoulder Christopher Ramnanan, Ph.D. October 27th, 2016 Contrast the stability and mobility between the hip joint and shoulder joint. Identify the bony features of the shoulder girdle and the structural features of the shoulder joint. Describe the primary muscles responsible for the movements of the shoulder joint, including the rotation of the scapula.

Joints involved in Upper Limb Movement Movements of the upper limb at the shoulder joint involves the sternoclavicular, acromioclavicular, and glenohumeral joints; loss-of-fx at any one of these joints can impair R.O.M. Proper motion involves not only function of these joints, but also the ‘scapulothoracic joint’ (concept of the scapula moving on the thoracic cage, not a true joint) Note: Shoulder girdle = clavicle + scapula

Comparison of Lower Limb with Upper Limb Glenohumeral joint vs. Hip joint >50% of head of femur fits with socket; highly congruent Fibrous layer of joint capsule has stout ligamentous specializations Extensive supporting muscles but w/o required ‘rotator cuff’ mechanism ~33% humeral head fits in glenoid cavity Relatively lax fibrous layer of joint capsule Tonus of rotator cuff critical to stability Mobility Stability

Anterior Osteology Acromion Anatomical Neck Greater Tubercle Lesser Tubercle Surgical Neck Bicipital Groove (Intertubercular sulcus) Glenoid fossa Coracoid Process Acromial end of clavicle Subscapularis fossa Medial border Lateral border Superior border Superior angle Inferior angle Features of the Humerus Features of the Scapula

Posterior Osteology Anatomical Neck Surgical Neck Spiral (Radial) Groove Deltoid tuberosity Head of humerus Spine of scapula Supraspinous fossa Infraspinous fossa Acromial end of clavicle Features of humerus Features of the Scapula

-Ball-in-socket synovial joint; most mobile of all our joints -Articulation: head of the humerus, glenoid fossa of the scapula Glenohumeral (GH, shoulder) joint

Glenohumeral (GH) joint Glenoid Fossa Lateral view, opened (GH) joint Coronal view, opened GH joint Glenoid Labrum Rotator Cuff Tendons Note: The glenoid labrum and the rotator cuff tendons increase joint stability and partly compensate for the poor congruency (‘fit’) b/w the humeral head and the glenoid fossa

Rotator cuff tendons (cut); add stability to joint capsule Transverse humeral ligament; tendon of long head, biceps brachii Joint capsule (FYI: reinforced by glenohumeral ligaments); relatively lax, especially inferiorly Coracoacromial ligament (strong extrinsic structure preventing superior shoulder dislocation) Anterior View Note: Most dislocations occur in direction where joint capsule is weakest (inferiorly and anteriorly) Glenohumeral (GH) joint, anterior view

Acromioclavicular (AC) joint -Articulation: distal (acromial) end of clavicle, acromion of scapula -supported by acromioclavicular ligament -bulk of stability of AC joint derived from the extrinsic coracoclavicular ligament and its two components (FYI; conoid and trapezoid ligaments) Acromion Clavicle Coracoclavicular ligament Acromioclavicular ligament

Shoulder (AC joint) separations

Superior rotation of Glenoid fossa: Serratus Anterior -Trapezius (superior & inferior fibres) Inferior rotation of Glenoid fossa: -Levator scapula -Rhomboids (acting with pectoralis major, latissimus dorsi, and gravity) Rotation of scapula: Powerful muscles pull on bony struts.

Normal superior rotation: Abnormal superior rotation:

Movements at shoulder Glenohumeral Scapular Rotation

Muscles of the Shoulder, on Posterior Body Wall (Superficial Back) Trapezius ( 3 parts): elevate, retract, depress scapula; superior/inferior fibres can rotate scapula superiorly Deltoid (3 parts): flex, abduct, extend arm Latissimus dorsi: extend, adduct, medially rotate arm Levator scapula: elevate, rotate scapula inferiorly Rhomboids: retract, rotate scapula inferiorly Teres Major: adducts, medially rotates humerus Supraspinatus: abduct arm Infraspinatus: laterally rotate arm Teres minor: laterally rotates arm

Superior View Posterior View Anterior View Subscapularis Rotator Cuff Muscles (4) Supraspinatus Infraspinatus Teres minor Subscapularis: medially rotates, adducts humerus Supraspinatus: abducts humerus (first 15 degrees) Infraspinatus: laterally rotates humerus Teres minor: laterally rotates the humerus

Subdeltoid / Subacromial bursa Coracoacromial Ligament Deltoid Subscapularis These bursae help reduce friction and protect the tendons from wear as they move across bones (acromion) and ligaments (coracoacromial lig.). The supraspinatus is particularly vulnerable.

Trapezius: Large muscle with 3 functional parts (FYI: all originating on midline structures, like the spinous processes, nuchal ligament, etc) -Superior fibres elevate (FYI- insert lateral 1/3 of clavicle) -Middle fibres retract (FYI- insert acromion) -Inferior fibres depress (FYI- insert spine of scapula) - Acting together, the superior and inferior fibres will rotate scapula superiorly Superior Middle Inferior

Latissimus Dorsi: -Extends, adducts and medially rotates humerus -FYI: originates on iliac crest, thoracolumbar fascia, and thoracolumbar spinous processes; inserts on floor of bicipital groove

Anterior Deltoid: 3 parts -Anterior: flexion, medial rotation of humerus -Middle: abduction of humerus -Posterior: extension, lateral rotation of humerus --FYI: originates on lateral clavicle, acromion, scapula spine; inserts on deltoid tuberosity of humerus Posterior

Teres Major: -Adduction, medial rotation of humerus -FYI: originates on inferior angle of scapula; inserts on medial lip of bicipital groove; this posterior muscle will course anteriorly to attach to humerus Levator Scapula: -Elevation, Inferior rotation of scapula FYI: originates on C1-C4 transverse processes; inserts into superior angle of scapula) Rhomboids (major, minor) -Retraction, Inferior rotation of scapula FYI: originates spinous processes of C7-T5; inserts on medial scapula from spine to inferior angle

Clavicular Sternocostal Pectoralis Major: 2 parts - Together: adduction, medial rotation - Clavicular head: flexion - Sternocostal head: extension -FYI: originates on anterior thoracic wall, inserts on lateral lip of bicipital groove Pectoralis Minor: - Deep to Pectoralis Major - Functions to protract scapula - Will be landmark in axilla (next lab) -FYI: originates on ribs 3-5, inserts on corocoid process of scapula Muscles of the Shoulder, on Anterior Body Wall

Winged Scapula: Damage to innervation of Serratus Anterior (long thoracic nerve) Serratus Anterior: - Protracts scapula (holds it against thoracic wall, boxer’s muscle) -Superior rotation of scapula -FYI: originates on upper ribs, inserts into anterior surface of medial border of scapula

All three anterior arm muscles supplied by musculocutaneous nerve Biceps brachii: supination + flexion (shoulder, elbow) Coracobrachialis: weak flexion / adduction (shoulder) Brachialis: flexes at the elbow, but does not cross the shoulder joint and therefore does not function at shoulder Muscles of the Shoulder, Anterior Arm Biceps brachii Coracobrachialis Brachialis

Muscles of the Shoulder, Posterior Arm All three heads of triceps brachii muscles supplied by radial nerve, and extend at the elbow Only the Long head crosses the shoulder joint and can extend the shoulder; the lateral and medial heads only cross the elbow the joint Clinical Note: The radial nerve runs in the radial (spiral) groove. The axillary nerve runs posterior to the surgical neck of the humerus to innervate the deltoid and teres minor. Both locations are common sites of fractures, putting the respective nerves at risk. Long head Lateral head Medial head (observed when lateral head has been resected) Radial N Axillary N

Unofficial Template for Practical Midterm (FYI)

LAB 6 CHECKLIST – SHOULDER LIGAMENTS and CARTILAGE and BURSA -Glenoid labrum -Coracoacromial ligament -Transverse humeral ligament -Coracoclavicular ligament -Glenohumeral ligaments* -Subdeltoid bursa -Subacromial bursa BONES -Clavicle -Scapula -Acromion -Coracoid process -Subscapular fossa -Glenoid cavity -Spine -Supraspinous fossa -Intraspinous fossa -Humerus -Anatomical neck -Surgical neck -Greater tubercle -Lesser tubercle -Bicipital groove -Deltoid tuberosity -Radial groove MUSCLES Rotator Cuff -Supraspinatus -Infraspinatus -Subscapularis -Teres minor Rotators -Trapezius -Serratus anterior -Levator scapulae -Rhomboids Anterior -Pectoralis major -Pectoralis minor Posterior -Teres major -Latissimus dorsi Arm -Deltoid -Biceps – long and short head -Brachialis -Coracobrachialis -Triceps – long, medial and lateral NB: Items italicized are conceptual, those denoted with a * are FYI