CHAPTER 5 Shoulder Complex

Review Degrees of freedom - # of planes in which joint moves Closed packed vs. loose packed position Closed packed Maximum area of surface contact; taut capsule; mechanically compressed joint, difficult to distract Loose/Open-packed Allowance of motion (spin, roll, slide, etc.) Resting position: point of least amount of congruency; capsule and ligaments are loosest/slack

Diarthrodial (synovial) joints: Review Diarthrodial (synovial) joints: Cartilage Ligaments Articular discs Joint capsule Synovial fluid Bursae

Introduction The shoulder is composed of three synovial joints and one pseudojoint. The shoulder maximizes mobility, but at the sake of stability. Primary purpose is to position hand for function.

Bones Manubrium Clavicle Superior aspect—contains shallow depression for medial clavicular attachments Sternal or jugular notch Clavicle S-shaped; similar to a crank Tubular at sternal end; flatter at acromial end

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

Bony Landmark Trails - 1 & 2

Bones of the Shoulder and Arm

Bones Humerus Bony prominences Greater tuberosity—three facets Lesser tuberosity Intertubercular groove Surgical neck

Bones of the Shoulder and Arm Review tubercles (greater and lesser) Intertubecular groove

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

Joints Sternoclavicular Ligaments Anterior/posterior Interclavicular Costoclavicular—clavicle to first rib

Trail 3 - S/C Joint Sternoclavicular Joint

Joints Acromioclavicular Plane synovial joint; three degrees of freedom Variable presence of articular disc Likely due to degeneration Ligaments Superior/inferior acromioclavicular; coracoclavicular

Acromioclavicular—osteokinematics Joints Acromioclavicular—osteokinematics 25–30° of upward rotation; A-P axis Small amounts of tilting Medial/lateral tilt about a superior-inferior axis Anterior/posterior tilt about an M-L axis Recommend inserting Figure 5-13

Trail 3 - Acromion, Clavicle “Springboard Ledge” Acromion Clavicle

Trail 3 - A/C Joint Acromioclavicular Joint

Joints Scapulothoracic Subscapular bursae/serratus anterior Functions include: Maintain length-tension relationship of rotator cuff/deltoid Position glenoid to receive humeral head Absorb shock Permit elevation of body (via scapular depression) Enhance shoulder ROM

Review Bony landmarks: acromion process, scapular spine, coracoid process, infraspinatous fossa, supraspinatous fossa, inferior angle, medial border, Humerus, deltoid tuberosity, manubrium body, articulating surfaces of sternal and acromial ends Joints: SC joint, AC joint, GH joint

Joints Scapulothoracic Subscapular bursae/serratus anterior Functions include: Position glenoid to receive humeral head Absorb shock Permit elevation of body (via scapular depression) Enhance shoulder ROM

Joints Scapulothoracic—kinematics 60° of upward rotation 30°from sternoclavicular joint; 30° from acromioclavicular joint Elevation/depression 10 cm/2 cm Protraction/retraction 10 cm/5 cm

Synergists - Scapula, Adduction and Abduction (scapulothoracic joint)

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

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

Joints Glenohumeral joint Coracoacromial arch Forms “roof” of GH joint Subacromial space between humeral head and acromion Coracoacromial ligament Subacromial impingement syndrome (SAIS)

Joints Glenohumeral joint Bursae Subacromial Subdeltoid Recommend inserting Figure 5-19

Subacromial bursae Subdeltoid bursae

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

Joints Glenohumeral joint Bicipital groove Biceps tendon restrained by coracohumeral and transverse humeral ligament. During shoulder motion, humerus moves on tendon. Tendon subject to wear and tear as well as impingement.

Scapulohumeral Rhythm “Setting phase”—highly variable After 30°, 2:1 ratio evident 120° from GH; 60° from scapula (acromioclavicular + sternoclavicular) Migrating axis of rotation Starts from medial root; moves laterally toward acromioclavicular joint 2:1 - for every 2 degrees @ GH joint, 1 degree @ scalpula thoracic joint. Setting phase: It preserves the length-tension relationships of the glenohumeral muscles; the muscles do not shorten as much as they would without the scapula's upward rotation, and so can sustain their force production through a larger portion of the range of motion. It prevents impingement between the humerus and the acromion. Because of the difference in size between the glenoid fossa and the humeral head, subacromial impingement can occur unless relative movement between the humerus and scapula is limited. Simultaneous movement of the humerus and scapula during shoulder elevation limits relative (arthrokinematic) movement between the two bones.

Muscles of the Shoulder and Arm - Posterior

Muscles of the Shoulder and Arm - Lateral

Muscles of the Shoulder and Arm - Anterior

Muscles of the Shoulder Complex Scapular stabilizers Serratus anterior Trapezius Rhomboid major/minor Pectoralis minor Levator scapulae

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 Passive stabilizers Sternoclavicular and acromioclavicular joints rely on ligaments for support. GH and scapulothoracic joint rely on muscles for support. At rest, humeral head suspended by: Ligaments—superior GH; coracohumeral Negative Intra-articular pressure Clavicle and scapula rest on thorax.

Function of Muscles of the Shoulder Complex Dynamic stabilizers Upper trapezius—low-level activity at rest Rotator cuff Biceps

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

Function of Muscles of the Shoulder Complex Muscle forces and moment arm length Shoulder elevation 30–60° of abduction—supraspinatus > leverage than deltoid Lever arm length for supraspinatus—remains constant throughout elevation range of motion Deltoid lever arm length—increases with elevation

Finally….! Finished with the shoulder! Complete trial Guide: pgs 34-38; p.47 (1-10); p.49 1,5,8 You may see these questions on the exam! Research paper outlines feedback tomorrow!