Lecture 19---Shoulder joint

At the end of this lecture the students should be able to: Enlist bones forming shoulder joint. Explain the shoulder joint with its ligaments. Identify the movements of the shoulder joint. Enumerate the blood and nerve supply of the shoulder joint. Identify clinical application.

References: - Clinical anatomy by regions 9 th edition (Pages 362 – 367). - Gray’s anatomy for student, 2ed edition (Pages 668 – 675).

Two bones: – Humerus-rounded head – Scapula- glenoid cavity

Type: Synovial, ball-and-socket joint Articular surfaces are covered by hyaline cartilage, and the glenoid cavity is deepened by a rim of fibrocartilage called the glenoid labrum. Capsule: thin and lax (but strong), and is attached to – Anatomical neck of the humerus – Margin of glenoid cavity (outside the labrum)

Synovial membrane: – Lines the capsule and attached to the margins of the hyaline cartilage – Synovial sheath and subscapularis bursa Ligaments: – Glenohumeral (between glenoid and humerus) – Coracohumeral(between coracoid process and humerus) – Coracoacromial(between acromion and coracoid pro – Transverse humeral Nerve supply: axillary and suprascapular Blood supply: axillary vessels

Rotator cuff: It is the name given to the sheath of tendons of the short muscles of the shoulder which covers and blends with all but the inferior aspect of that joint. The muscles are: – Supraspinatus, infraspinatus and teres minor (inserted from above down into the humeral greater tubercle), – And subscapularis (inserted into the lesser tubercle). All originate from the scapula.

The stability of the shoulder joint depends almost entirely on the strength of the surrounding muscles: – 1. Closely related short muscles of the ‘rotator cuff’. – 2. Long head of biceps, arising from the supraglenoid tubercle and crossing over the head of the humerus, thus lying actually within the joint, although enclosed in a tube of synovium. – 3. Long muscles of the shoulder; the deltoid, long head of triceps, pectoralis major, latissimus dorsi and teres major.

Movements: – Flexion – Extension – Abduction(supraspinatus initiates it) – Adduction – Lateral rotation – Medial rotation – Circumduction

Principal muscles acting on the shoulder joint: Abductors Adductors supraspinatus pectoralis major deltoid latissimus dorsi Flexors Extensors pectoralis major teres major coracobrachialis latissimus dorsi deltoid (anterior fibres) deltoid (posterior fibres) Medial rotators Lateral rotators pectoralis major infraspinatus latissimus dorsi teres minor teres major deltoid (posterior fibres) deltoid (anterior fibres) subscapularis

Clinical Correlates Dislocations of the Shoulder Joint: it is the most commonly dislocated large joint. – Anterior Inferior Dislocation. – Posterior Dislocations Shoulder pain: The joint is supplied by axillary and suprascapular nervesand it is sensitive to pain, pressure, excessive traction, and distention.