Shouler joint

shoulder joint complex, SC joint anatomy, Biomechanics of SC joint, AC joint anatomy, Biomechanics of AC joint, ST joint anatomy, GH joint anatomy

1. THE SHOULDER COMPLEX

2. INTRODUCTION Connects the upper limb to the axial skeleton Composed of the clavicle, scapula and humerus. Has greater mobility and less stability Anteriorly, the clavicle reaches the sternum and articulates with it at the sterno-clavicular joint The clavicle and the scapula are united to each other at acromio-clavicular joint

3. STERNO- CLAVICULAR JOINT Plane Synovial joint Compound joint Saddle shaped surface 3 degree of freedom It has a synovial capsule, joint disk and three major ligaments Medial end of the clavicle, clavicular notch of the manubrium sterni and the upper surface of the first costal cartilage Clavicular surface is convex from above downwards and slightly concave from front to back and vice versa for sternal surface

4. The superior portion of the medial clavicle does not contact the manubrium; serves the attachment of the SC joint disk and the inter clavicular joint. At rest, the SC joint space is wedge- shaped and open superiorly

5. SC DISK Has a fibrocartilage joint disk or meniscus Increases congruence between joint surfaces Upper portion is attached laterally to the clavicle on a rough area above and posterior Lower portion is attached inferiorly to the sternum, first costal cartilage and anterior and posterior aspects to the fibrous capsule In elevation and depression of the clavicle, the medial end of the clavicle rolls and slides in relation to the stationary disk (upper point of the disk serving as a pivot point

6. In protraction/retraction the SC disk and medial clavicle rolls and slide together on the manubrium facet (lower part serving as pivot point) Disk is part of manubrium in elevation/depression and part of the clavicle in protraction/retraction Mechanical axis for these two movements located at the more laterally located costo - clavicular ligament

7. SC JOINT LIGAMENTS SC ligament Anterior and posterior SC ligaments reinforce the capsule Primary function is to check anterior and posterior translatory movements of the medial end of the clavicle Attached laterally to the margins of the articular surface of the clavicle, and medially to the margins of the articular surface of the sternum

8. Costo - clavicular ligament: Very strong ligament Between the clavicle and the first rib Attached above to the rough area on the inferior aspect of the medial end of the clavicle Inferiorly to the first costal cartilage and to the first rib Has two segments or laminae Anterior segment is directed laterally from the first rib to the clavicle. Posterior segment is directed medially from the first rib to the clavicle

9. Both segments check elevation of the lateral end of the clavicle and when the limits of the ligament are reached inferiorly glide the medial clavicle.

10. Inter- clavicular ligament Passes between the sternal ends of the right and left clavicles Resists excessive depression of the distal clavicle and superior glide of the medial end of the clavicle.

11. Blood supply: internal thoracic and suprascapular arteries Nerve supply: medial supraclavicular nerve

12. BIOMECHANICS ELEVATION/DEPRESSION OF THE CLAVICLE: Occur around an approximately AP axis Between a convex clavicular surface and a concave surface With elevation the lateral end of the clavicle rotates upward and medial end slides inferiorly and with depression lateral end of the clavicle rotates downwards and medial end slides superiorly.

13. PROTRACTION/RETRACTION OF THE CLAVICLE: Occurs around an approximately vertical axis With protraction, the lateral end of the clavicle rotates anteriorly and the medial end of the clavicle is expected to slide anteriorly With retraction, the lateral end of the clavicle rotates posteriorly and the medial end of the clavicle is expected to slide posteriorly

14. Anterior and posterior rotation of the clavicle: Occurs as a spin between the saddle shaped surfaces of the medial clavicle and manubrio - costal facet The clavicle can rotate in only posterior direction from the neutral, bringing the inferior surface of the clavicle to face anteriorly. From its fully rotated position, the clavicle can rotate anteriorly again to return in neutral.

15. ACROMIO- CLAVICULAR JOINT Plane synovial joint 3 rotational and translational degrees of freedom Has a joint capsule and 2 major ligaments, a joint disk may or may not be present Formed by the articulation between a small facet at the lateral end of the clavicle and on the medial margin of the acromion process of the scapula

16. AC JOINT CAPSULE AND LIGAMENTS CAPSULE: Weak Can not maintain integrity of the joint Superior AC ligament assists the capsule in apposing articular surfaces and in controlling A-P joint stability Coracoclavicular ligament: Provides joint stability Divided into lateral portion (trapezoid ligament), and a medial portion ( conoid ligament)

17. Trapezoid ligament: Quadrilateral in shape Nearly horizontal in orientation Provides the majority of resistance to posterior translator forces applied to the distal clavicle Conoid ligament: Triangular in shape Vertically oriented Provides the primary restraint for the AC joint in the superior and inferior directions

18. Both portions of the coracoclavicular ligament limit upward rotation of the scapula at the AC joint Blood supply: suprascapular and thoracoacromial arteries Nerve supply: lateral supraclavicular nerve

19. BIOMECHANICS OF AC JOINT Internal and external rotation: IR/ER of the scapula in relation to the clavicle occurs around approximately vertical axis through the AC joint IR= glenoid fossa of the scapula anteromedially ER= glenoid fossa of the scapula posterolaterally

20. Anterior and posterior tipping: Anterior/posterior tipping or tilting of the scapula in relation to the clavicle around an oblique coronal axis. Anterior tipping: acromion tipping forward and the inferior angle tipping backward. Posterior tipping: acromion tipping backward and the inferior angle tipping forward

21. Upward/ downward rotation: Occur about an oblique A-P axis approximately perpendicular to the plane of the scapula. Upward rotation: tilts the glenoid fossa upward Downward rotation: tilts the gelnoid fossa downward.

22. SCAPULOTHORACIC JOINT Formed by the articulation of the scapula with the thorax Not a true anatomic joint; functional joint The articulation depends on the integrity of the anatomic AC and SC joint Normally the scapula rests at a position on the posterior thorax approximately 2 inches from the midline, between the second through seventh ribs IR 30 degrees to 45 degrees from the coronal plane Anterior tipping approximately 10 degrees to 20 degrees from vertical

23. BIOMECHANICS OF ST JOINT Upward/downward rotation: As AC joint Elevation/depression: Elevation: shrugging the shoulder up Depression: depressing the shoulder downward Protraction/retraction: Translatory motions Protraction: vertebral border away from the midline Retraction: vertebral border towards the midline.

24. SHOULDER JOINT Ball and socket joint Synovial type of joint 3 rotational and 3 translational degree of freedom Has a joint capsule, ligaments and bursae Articulation is between the humeral head and the glenoid fossa of the scapula Stability is maintained by: The coracoacromial arch The RC muscles of the shoulder The glenoid labrum

25. Humeral head faces medially, superiorly and posteriorly Angle of inclination: 130 degrees to 150 degrees Angle of torsion: 30 degrees

26. GLENOID LABRUM Attached to the periphery of the glenoid fossa Total articular surface of the glenoid fossa is enhanced by the glenoid labrum Superiorly is loosely attached Inferior portion is firmly attached and relatively immobile.

27. GH CAPSULE Very loose Permits free movements Taut superiorly and slack anteriorly and inferiorly Twists on itself and tightens when the arm is abducted and internally rotated (CPP of the GH joint) Medially, attached to the scapula beyond the supraglenoid tubercle and the margins of the labrum Laterally, attached to the anatomical neck of the humerus Inferiorly extends down to the surgical neck Superiorly deficient for passage of the tendon of the long head of the biceps brachii

28. Anteriorly reinforced by the superior, middle and inferior GH ligaments. Superior GH ligament: passes from the superior glenoid labrum to the upper neck of the humerus deep to the coracohumeral ligament Middle GH ligament: runs obliquely from the superior anterior labrum to the anterior aspect of the proximal humerus below the superior GH ligament Inferior GH ligament complex: anterior and posterior bands and axillary pouch

29. GH LIGAMENTS Coracohumeral ligament: extends from the root of the coracoid process to the neck of the humerus opposite the greater tubercle; gives strength to the capsule Transverse humeral ligament: bridges the upper part of the bicipital groove of the humerus ; tendon of the long head of the biceps brachii passes deep to the ligament

30. CORACOACROMIAL ARCH Formed by the coracoid process, the acromion and the coracoacromial ligament Forms an osteoligamentous vault that covers the humeral head and forms a space within which the subacromial bursa, the RC tendons and the portion of the tendon of the long head of the biceps brachii Protects the structures beneath it from the direct trauma from above. Prevents the head of the humerus from dislocating superiorly, because an unopposed upward translator force on the humerus would cause the head of the humerus to hit the coracoacromial arch

31. As a consequence, however, the contact of the humeral head with the undersurface of the arch can cause painful impingement or mechanical abrasion of the structures lying in the subacromial space. When the subacromial space is narrowed, the impingement of the RC tendons and subacromial bursa during elevation of the humerus increases.

32. BURSAE Subacromial ( subdeltoid ) bursa These bursa separate the supraspinatus tendon and head of the humerus from the coracoid process, acromion, coracoacromial ligament and deltoid muscle Permits smooth gliding between the humerus and supraspinatus tendon Subscapularis bursa Infraspinatus bursa

33. Blood supply: Anterior circumflex humeral vessels Posterior circumflex humeral vessels Suprascapular vessels Subscapular vessels

34. Nerve supply: Axillary nerve Musculocutaneous nerve Suprascapular nerve