The shoulder joint is a synovial ball-and-socket joint between the head of the humerus bone and the shallow glenoid cavity of the scapula. It has a thin, lax capsule strengthened by rotator cuff muscles and ligaments. The joint allows wide range of movement including flexion, extension, abduction, adduction, medial and lateral rotation, and circumduction. It is prone to dislocations, especially anterior dislocations, due to its anatomy. Recurrent dislocations often require surgical repair to reattach the capsular ligaments.

4. Articular surface covered by hyaline articular cartilage.

7. Laterally to the anatomical neck of humerus.Thin and lax, allow wide range of movement. Strengthened by slips of tendons of subscapularis m., supraspinatus m., infraspinatus m. & teres minor (rotator cuff muscles).

14. Extends between coracoid process of scapula and acromion.

18. Subscapularis bursa

21. Extends through the anterior wall of the capsule to form the subscapularis bursa beneath the subscapularis muscle.

24. Posterior circumflex humeral vessels

25. Suprascapular vessels

28. Suprascapular nerve

30. Subacromial bursa

31. Coracoacromial ligament

33. Axillary nerve

35. Coracobrachialis

36. Short head of biceps brachii

38. Teres minor

39. DeltoidWithin the joint - Tendons of long head biceps brachii

40. Movements

43. Adduction – Arm moves towards the trunk.MAIN ACCESSORY MOVEMENT

45. Lateral rotation – Hand moves laterally.MAIN ACCESSORY MOVEMENT

47. Disproportionate area of articular surfacesOccurs when the arm is abducted 3 types of shoulder joints: Glenohumeral joint Acromioclavicular joint Sternoclavicular joint

48. Applied Anatomy Dislocation of glenohumeral joint Glenohumeral joint Extremely mobile Providing wide movement at the expense of stability Relatively small bony glenoid cavity Supplemented by : Robust fibrocartilagiousglenoid labrum Ligamentous support Make it susceptible to dislocation Divided into : Anterior dislocation Posterior dislocation

49. Applied Anatomy Anterior dislocation Occurs most frequently. Usually associated with an isolated traumatic incident. Clinically, all anterior dislocation are anteroinferior. Once joint capsule and cartilage disrupted Joint is susceptible to further (recurrent) dislocation When dislocation occurs, During abduction, the head of humerus presses against the lower unsupported part of capsular ligament Thus, almost always the dislocations primarily subglenoid,later it may become subcoracoid,subclavicular or subspinous. Dislocations ends with : Axillary nerve injured (by direct compression of humeral head on the nerve inferiorly as it passes through quadrangular space) Lengthening effect of humerus may stretch the radial nerve which cause radial nerve paralysis

50. Applied Anatomy Occasionally, anteroinferior dislocation associated with fracture and require surgical reduction. Posterior dislocation Rare Most common cause : Extremely vigorous muscle contraction associated with An epileptic seizure caused by electrocution

55. Applied Anatomy Fractures of the clavicle and dislocations of the acromioclavicular and sternoclavicular joints Its relative size and the potential forces that it trasmits from the upper limb to the trunk, it is not surprising that it is often fractured. The typical site of fracture is the middle third. The medial and lateral thirds are rarely fractured. The acromial end of the clavicle tends to dislocate at the acromioclavicular joints with trauma The outer third of the clavicle is joined to the scapula by the conoid and trapezoid ligaments of the coracoclavicular ligament. Minor injury, tends to Tear the fibrous joint capsule and ligaments of the acromioclavicular joint resulting Acromioclavicular separation on a plain radiograph

58. Applied Anatomy More severe trauma disrupt the conoid and trapezoid ligaments of coracoclavicular ligament results in elevation and upward subluxation of the clavicle The typical injury at the medial end of the clavicle is an anterior or posterior dislocation of the sternoclavicular joint. Importantly, a posterior dislocation of the clavicle may impinge on the great vessels of the superior mediastinum and compress or disrupt them.

70. The MRI findings are typical for an anterior inferior dislocation

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