The Shoulder Complex and Girdle
The Shoulder Complex and Girdle EXSC 322
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This 13 page Class Notes was uploaded by Ticynn London on Friday March 18, 2016. The Class Notes belongs to EXSC 322 at Old Dominion University taught by Phil Sabatini in Spring 2016. Since its upload, it has received 66 views. For similar materials see Anatomical Kinesiology in Physical Education at Old Dominion University.
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Date Created: 03/18/16
The Shoulder Complex Shoulder Girdle Have four articulations: • Sternoclavicular • Acromioclavicular • Coracoclavicular • Scapulothoracic Sternoclavicular (SC) Articulation Articulation between the sternum and clavicle – Ball-and-socket joint – Freely mobile in frontal and transverse plane – Limited sagittal movement Site of most movement of shoulder girdle – Elevation: depression (shrugging shoulders, 60°) – Protraction: retraction (rowing, 30°) – Anterior: posterior rotation (raising your hand, 30-45°) Ligamentous support – Anterior sternoclavicular ligament – Posterior sternoclavicular ligament – Costoclavicular & interclavicular ligaments Anterior Posterior Acromioclavicular (AC) Articulation Articulation between the acromion process and distal end of clavicle Motion most noticeable during arm elevation (shoulder abduction) Ligamentous support – Superior acromioclavicular ligament – Inferior acromioclavicular ligament – Coracoacromial ligament Coracoclavicular (CC) Articulation Articulation between coracoid process of scapula and clavicle Assists in reinforcement of the weak AC articulation Ligamentous support – Coracoclavicular ligaments i.e., conoid & trapezoid Scapulothoracic Articulation • “articulation” between the anterior surface of the scapula (scapular fossa) and the thoracic wall – supported dynamically by muscles – no ligamentous support • acts to stabilize shoulder region during lifting (shrugging) - e.g. picking up a suitcase • facilitates overhead movements through elevation and upward rotation of the glenohumeral joint Clavicle • Roles: – Helps facilitate scapular motion – Site of muscular attachment – Provides a barrier to protect underlying structures – Acts strut to stabilize the shoulder and prevent medial displacement when the muscles contract – Prevents an inferior migration of the shoulder girdle. Scapula Primary function is to provide muscle attachment sites for shoulder muscles. Shoulder Girdle Movements Abduction (protraction) scapula moves laterally away from spinal column Adduction (retraction) scapula moves medially toward spinal column Downward rotation returning inferior angle inferomedially toward spinal column & glenoid fossa to normal position Upward rotation turning glenoid fossa upward & moving inferior angle superolaterally away from spinal column Depression downward or inferior movement i.e., returning to normal position Elevation upward or superior movement i.e., shrugging shoulders • Shoulder girdle muscles – Stabilize scapula • maintain scapula in a relatively static position during shoulder joint actions • Provide stable base for shoulder muscles to move humerus – Move shoulder girdle • enhance movement of upper extremity when shoulder goes through extreme ranges of motion • Synergy with muscles of glenohumeral joint – At the extreme ranges of motion: • Scapular muscles move shoulder girdle to position glenoid fossa • Allows humerus more mobility – Without the accompanying scapula movement humerus can only be raised into approximately 90 of total shoulder abduction & flexion. – Synergy between scapula & shoulder joint muscles enhances movement of entire upper extremity Scapulohumeral Rhythm scapular rotation to facilitate shoulder abduction 1st 30 of abduction little scapular rotation e.g., shoulder = 30 , scapula ≈ 6 o beyond 30 o for every 2 of shoulder movement, scapula rotates 1 o 2:1 ratio Five Primary Muscle Involved in Shoulder Girdle Movement 1. levator scapulae 2. trapezius 3. rhomboids 4. serratus anterior 5. pectoralis minor Shoulder Girdle Muscles Rhomboids Rhomboids Trapezius Trapezius Levator Levator Scapulae Scapulae Trapezius Pectoralis Minor Serratus Anterior Pectoralis Minor Rhomboids Pectoralis Minor Trapezius Levator Scapulae Serratus Anterior Trapezius muscle Upper fibers: elevation upward rotation Middle fibers: elevation retraction Lower fibers: depression upward rotation retraction Levator scapulae muscle elevation downward rotation Rhomboid muscles - major & minor retraction elevation downward rotation Pectoralis Minor Muscle depression protraction downward rotation Subclavius Muscle Serratus Anterior Muscle Stabilization & protection of SC joint depression protraction protraction upward rotation Scapula Protraction (abduction) Scapula moving laterally away from spinous processes without rotation e.g., Push-up & bench press (upward phase) Agonists Pectoralis minor Serratus anterior Scapula Retraction (adduction) Scapula moving medial toward the spinous processes without rotation (i.e, return from abduction) Agonists e.g., rowing Middle trapezius Rhomboids Scapula Upward Rotation Lateral & upward movement e.g., reaching arm over head Scapula Downward Rotation Downward & Medial Movement Glenoid Fossa is rotated downward when downward movement of shoulder joint occurs e.g., lat pull downs Agonists Pectoralis minor Rhomboid Scapula Elevation Superior movement of the scapula without rotation e.g., Shoulder shrugs Agonists Rhomboid Levator scapula Upper trapezius Scapula Depression Inferior movement of the scapula without rotation Agonists Lower trapezius Pectoralis minor Shoulder Joint Glenohumeral (GH) articulation – Articulation of the humerus and glenoid fossa – Designed for mobility (Most mobile in body) – Lacks bony and ligamentous support – Shallow glenoid fossa – Half-spherical humeral head • Wide range of motion of the shoulder joint in many different planes requires a significant amount of laxity • Common to have instability problems – Rotator cuff impingement – Subluxations & dislocations • The price of mobility is reduced stability • The more mobile a joint is, the less stable it is & the more stable it is, the less mobile Stability of GH – Passive, Static stabilizers- • articular surface, glenoid labrum, joint capsule and ligaments. – Fully sealed, which provides suction and resists a dislocating force at lower loads. – Dynamic support • occurs mostly at midrange of motion and is provided by the muscles as they contract in a coordinated pattern to compress the humeral head in the glenoid cavity. – Posterior Stability • The posterior rotator cuff muscles – Anterior Stability • Subscapularis • Long head of the biceps (superior humeral head translation) – The Deltoid and the other scapulothoracic muscles position the scapula to provide maximum GH stability. Supporting structures for shoulder Glenoid fossa is ¼ - ⅓ size of humeral head Glenoid labrum – Lip of cartilage surrounding the joint – Increases width and depth of fossa – Assists in holding the humerus in place Coracohumeral ligament – Stabilizes the humerus against superior and lateral displacement Glenohumeral ligament – Stabilizes the humerus against anterior displacement – Superior – Middle – Inferior Shoulder Joint Movements Abduction superior & lateral movement of humerus away from body Adduction inferior & medial movement of humerus toward body Flexion movement of humerus straight anteriorly Extension movement of humerus straight posteriorly Horizontal adduction aka - transverse flexion movement of humerus in transverse plane toward & across chest Horizontal abduction aka - transverse extension movement of humerus in transverse plane away from chest Internal (medial) rotation movement of humerus medially around its long axis toward midline External (lateral) rotation movement of humerus laterally around its long axis away from midline Shoulder Joint Shoulder Girdle Abduction Upward rotation Adduction Downward Rotation Flexion Elevations & Upward Rotation Extension Depression & Downwards Rotation Internal Rotation Protraction External Rotation Retraction Horizontal Adduction Protraction Horizontal Abduction Retraction Glenohumeral internal rotation deficit (GIRD) – difference in internal rotation range of motion between an individual’s throwing & non throwing shoulders – overhead athletes with a GIRD of greater than 20% had a higher risk of injury – stretching exercises recommended to regain internal rotation • improve performance • reduce likelihood of injury Muscles that Attach or Cross the Glenohumeral 1. Deltoid 2. Coracobrachialis 3. Teres major 4. Subscapularis 5. Supraspinatus 6. Infraspinatus 7. Teres minor 8. latissimus dorsi 9. pectoralis major Rotator Cuff Muscles Supraspinatus Infraspinatus Teres minor Subscapularis Deltoid Anterior fibers: abduction flexion horizontal adduction internal rotation Middle fibers: abduction flexion Posterior fibers: abduction extension horizontal abduction external rotation Coracobrachialis Muscle horizontal adduction flexion adduction internal rotation extension adduction Latissimus dorsi’s “little helper” Pec Major Clavicular head: flexion (up to 60 ) o horizontal adduction internal rotation o adduction (<90 ) abduction (>90 ) o Sternal head: extension horizontal adduction internal rotation adduction Latissimus Dorsi Muscle adduction extension internal rotation horizontal abduction downward rotation of the scapula Supraspinatus Stabilization of humeral head in the glenoid fossa abduction Infraspinatus Muscle Stabilization of humeral head in the glenoid fossa external rotation horizontal abduction extension Teres Minor Muscle Stabilization of humeral head in the glenoid fossa external rotation horizontal abduction extension Subscapularis Muscle Stabilization of humeral head in the glenoid fossa internal rotation adduction extension Glenohumeral Flexion Agonists Anterior deltoid Pectoralis major (clavicular head) Glenohumeral Extension Agonists Teres major Latissimus dorsi Pectoralis major (sternal head) Deltoid Glenohumeral Abduction Agonists Deltoid Supraspinatus Pectoralis major (clavicular head) Glenohumeral Adduction Agonists Latissimus dorsi Teres major Pectoralis major (sternal head) Glenohumeral Internal Rotation Agonists Latissimus dorsi Teres major Subscapularis Pectoralis major (sternal head) Glenohumeral External Rotation Agonists Infraspinatus Teres minor Glenohumeral Horizontal Abduction Agonists Posterior deltoid Infraspinatus Teres minor Glenohumeral Horizontal Adduction Agonists Anterior deltoid Pectoralis major Coracobrachialis