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Anatomy of Shoulder Part 2. Ligaments. Sternoclavicular Joint Ligaments Extremely weak because of boney arrangement Anterior sternoclavicular Prevents upward displacement of clavicle Posterior sternoclavicular Prevents upward displacement of clavicle Interclavicular
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Ligaments • Sternoclavicular Joint Ligaments • Extremely weak because of boney arrangement • Anterior sternoclavicular • Prevents upward displacement of clavicle • Posterior sternoclavicular • Prevents upward displacement of clavicle • Interclavicular • Prevents lateral displacement of clavicle • Costoclavicular • Prevents lateral and upward displacement of clavicle
Ligaments • Consists of Anterior, posterior, superior, and inferior portions • Coracoclavicular ligaments joins the coracoid process and clavicle helps maintain the position of the clavicle relative to the acromion • Coracoclavicular • Divided into • Coniod and trapezoid ligaments • Coracoacromial ligament • Connects the coracoid to the acromion
Ligaments • Glenohumeral Joint Ligaments • Superior Ligament • Middle Ligament • Inferior Ligament • Produce major restraint in shoulder flexion, extension and rotation
Ligaments • Glenohumeral Joint Ligaments • Anterior • Tense in extension, abduction or external rotation • Posterior • Tension is in extension with external rotation • Middle • Tension in flexion and external rotation • Inferior • Tense in abduction, extended or externally rotated
Ligaments • Glenohumeral Ligaments • Inferior GH Ligament • Primarily a check against both anterior and posterior dislocation of humeral head • Transverse ligament • Retains the long biceps tendon within the bicipital groove
Muscles • Dynamic motion • Establish stability to compensate for a great deal of mobility • Flexion, extension, abduction, adduction, horizontal adduction/abduction, internal/external rotation and circumduction
Muscles • 1st group • Originate on axial skeleton • Attach to humerus • Latissiumus dorsi • Pectoralis major • 2nd group • Originates on scapula • Attach to humerus • Deltoid • Teres major • coracobrachialis • Rotator cuff muscles • Subscapularis, supraspinatus, infraspinatus and teres minor • Tendons adhere to the articular capsule and serve as reinforcing structures • Biceps and triceps • Attach on the glenoid and effect elbow motion
Muscles • Scapular Muscles • 3rd group • Levator scapulae • Trapezius • Rhomboids • Serratus anterior • Important in providing dynamic stability to the shoulder complex
Bursae • Most important Subacromial Bursa • Between coracoacromial arch and glenohumeral capsule • Reinforced by the supraspinatus tendon • Subacromial bursa • Easily subjected to trauma in overhead position • Compressed under coracoacromial arch
Nerve Supply • Spinal nerve roots • 5th cervical vertebra through 1st Thoracic vertebra • Create the brachial plexus • Innervate muscles of upper extremity • Axillary (C5-C6) • Musculocutaneous (C5-C7) • Subscapular (C5-C6) • Suprascapular (C5-C6) • Dorsal scapular (C5) • Pectoral (C5-T1) • Radial (C5-T1)
Functional Anatomy • Rotator Cuff Muscles • Subscapularis, infraspinaturs, supraspinatus and teres minor (along with long head of biceps) • Provide dynamic stability • Control position • Prevent excessive displacement of the humeral head • Supraspinatus • Compresses humeral head • Infraspinatus, teres minor and subscapularis • Depress the humeral head during overhead movements
Functional Anatomy • Glenohumeral joint capsule • As muscle contracts they dynamically tighten the joint capsule • Which helps center the humeral head to the glenoid • Dynamic movement and stabilization of shoulder • Also needs scapulothoracic, acromioclavicular and sternocalvicular joint to move as well
Functional Anatomy • Muscles that produce movement of the scapula on the thorax help maintain the position of the glenoid relative to the moving humerus • Levator scapula and upper trapezius (elevate scapula) • Middle trapezius and rhomboids (adduct scapula) • Lower trapezius (adducts and depresses scapula) • Serratus anterior (abducts and upwardly rotates the scapula)
Scapulohumeral Rhythm • Describes the movement of the scapula relative to the movement of the humerus throughout a full range of abduction • Humerus elevates to 30 degrees: no movement of scapula • Setting phase • 30 to 90 degrees: scapula abducts and upwardly rotates • 90 degrees to full abduction: scapula abducts and upwardly rotates 1 degree for each 1 degree of humeral elevation • Clavicular movement must occur at both the SC and AC joints • Clavicle must elevate 40 degrees and rotate in a poster superior direction at least 10 degrees