CHAPTER 5 Shoulder Complex

Shoulder girdle has 3 joints: Introduction Shoulder complex is the shoulder joint (GH joint) and the shoulder girdle. Shoulder girdle has 3 joints: Sternoclavicular Acromioclavicular scapulo-thoracic (aka scapulo-costal) Only a functional joint – not a structural joint

General considerations: The shoulder maximizes mobility, but at the sake of stability. Primary purpose is to position hand for function.

Bones Scapula Flat triangular bone Vertebral border positioned between T2 and T7 Provides location for glenohumeral (GH) muscles to originate and provides stable base from which GH joint can operate

Bones Scapula Works in concert with clavicle to enhance total shoulder range of motion (ROM) Has many unique bony prominences: Superior and inferior angles; spine; borders Glenoid fossa; acromion; coracoid process Supraspinatus/infraspinatus/subscapular fossas Supraglenoid and infraglenoid tubercles

Bones Scapula Glenoid fossa Deepened 50% by glenoid labrum

Shoulder girdle movements Joints Shoulder girdle movements Elevation/depression Protraction/retraction Upward rotation/downward rotation Scapular tilting—A-P; M-L

Joints Sternoclavicular Connects upper extremity to axial skeleton Saddle joint with three degrees of freedom Elevation/depression Protraction/retraction Rotation Acromioclavicular Scapulothoracic

Joints Glenohumeral joint Ball and socket; three degrees of freedom Inherently unstable Humeral head more than twice the size of glenoid Labrum deepens socket Large capsule; redundant inferiorly

Joints Glenohumeral joint Capsular reinforcements Superior/middle/inferior GH ligaments Coracohumeral ligament Long head of biceps/triceps Rotator cuff tendons blend with capsule

Rotator Cuff Supraspinatus Infraspinatus Subscapularis Teres minor

Glenohumeral joint—osteokinematics Joints Glenohumeral joint—osteokinematics Abduction/adduction—frontal—A-P axis Flexion/extension—sagittal—M-L axis Medial/lateral rotation—transverse—superior-inferior axis

Glenohumeral joint—arthrokinematics Joints Glenohumeral joint—arthrokinematics Flexion/extension—spin Abduction—superior roll; inferior glide Lateral rotation—posterior roll; anterior glide Medial rotation—anterior roll; posterior glide

Scapulohumeral Rhythm Pairing of shoulder girdle movement with shoulder joint movement Example: abduction of arm at shoulder joint With Upward rotation of shoulder girdle (scapula)

Muscles of the Shoulder Complex Glenohumeral stabilizers Supraspinatus Infraspinatus/teres minor Subscapularis Biceps/triceps brachii

Muscles of the Shoulder Complex Large movers Deltoid Latissimus dorsi Teres major Pectoralis major Coracobrachialis

Function of Muscles of the Shoulder Complex Synergistic muscle actions—force couples Upward scapular rotation Upper Trapezius—Lower Trapezius—Serratus Anterior Downward Scapular Rotation Pectoralis minor—levator scapulae—rhomboids Shoulder elevation Deltoid and rotator cuff

Summary Shoulder is composed of three real joints; one pseudojoint Shoulder provides extensive ROM GH joint is inherently unstable Rotator cuff and scapular muscles provide dynamic support to GH joint and scapula

Total shoulder motion is a result of: Summary Total shoulder motion is a result of: Intricate balance between joints of shoulder Proper functioning and synchronization of muscles Shoulder injuries are common and occur when a “breakdown” of any one of the links occurs