The Shoulder Joint PDF

The Shoulder Joint By Dr. Muhamad Saeed Sulaivany Overview The shoulder joint (or glenohumeral joint) is formed between the articular surfaces of the glenoid cavity of the scapula and the head of the humerus. It is a ball and socket synovial joint which allows a wide range of movem...

The Shoulder Joint By Dr. Muhamad Saeed Sulaivany Overview The shoulder joint (or glenohumeral joint) is formed between the articular surfaces of the glenoid cavity of the scapula and the head of the humerus. It is a ball and socket synovial joint which allows a wide range of movements in multiple planes. The bone conformation and range of movement affects joint stability. Movement of the shoulder occurs at both the glenohumeral and scapulothoracic joints.  Glenohumeral joint Synovial membrane The joint is lined by synovium and enclosed by a fibrous capsule. The glenoid cavity is deepened by a rim of fibrocartilage – the glenoid labrum – but despite this the glenohumeral joint is still unstable. This is due to the shallowness of the glenohumeral joint and the disproportion of articular surfaces. Stability is provided by a capsule, various ligaments and the rotator cuff SITS muscles. Capsule The capsule is attached to the glenoid labrum, the scapula and the anatomical head of the humerus. It bridges the intertubercular groove of the humerus and extends medially to the surgical neck of the humerus. It is a tough fibrous capsule but is relatively lax to allow movement to occur in many planes. It is thickened in some areas due to the attachment of three glenohumeral ligaments anteriorly and a coracohumeral ligament above. There is a small opening anteriorly in the capsule where the synovial membrane communicates with the subscapular bursa. (A bursa is a sack of synovial fluid between two articulating surfaces to reduce friction). The subscapular bursa separates the tendon of the subscapularis. The synovium and the joint cavity are continuous with the subscapular bursa through this gap in the capsule. The second opening is smaller and allows the tendon of the long head of biceps brachii to arise from the supraglenoid tubercle. The tendon passes through the joint outside the synovial membrane. The tendon of the long head of the biceps brings with it a prolongation of the synovial membrane. This tubular sleeve of synovium is reflected around the biceps tendon like a tube.  Ligaments Intracapsular ligaments There are three intracapsular ligaments which are fibrous bands between the glenoid labrum and the humerus. These ligaments are continuous with the fibrous capsule and reinforce the capsule anteriorly. They are: Superior glenohumeral ligament Left shoulder Middle glenohumeral ligament Inferior glenohumeral ligament  Extracapsular ligaments There are also three extracapsular ligaments: Coracoacromial ligament □ Q links the acromion and the ② coracoid process Coracohumeral ligaments □ passes fro the base of the coracoid process to the anterior part of the greater tubercle of the humerus ③ Transverse humeral ligament □ holds the tendon of the long head of the biceps in Intracapsular (Sup. Mid. Inf.) place during shoulder movement  Coraco Acromial Arch The coracoarcomial arch is a strong, osseoligamentous structure which provides a smooth under-surface of the acromion, the coracoacromial ligament and the coracoid process. It overlies the humeral head and prevents the upper displacement of the humerus The tendon of the supraspinatus muscle is separated from the coracoacromial arch by the subacromial bursa. There is a small space between the acromion and the head of the humerus, within this space are: – The subacromial bursa – Rotator cuff tendons – Tendon of the long head of the biceps During abduction there is risk of soft tissue impingement between the head of the humerus and the acromion.  Bursae around the glenohumeral joint There is the subscapular bursa ① which facilitates the movement of the tendon of subscapularis over the scapula. A bursa is a sack of synovial fluid between 2 articulating surfaces to reduce friction on movement. The subscapular bursa separates the tendon of subscapularis from the joint. The synovium and the joint cavity are continuous with the subscapular bursa through a gap in the capsule. ② Subacromial bursa facilitates the movement of the supraspinatus tendon under the coraco acromial arch and the deltoid muscle over the shoulder joint and the greater tubercle of the humerus Inflammations of the bursa can occur: Subacromial bursitis causes pain on abduction of the arm between 50-130 degrees, this is painful arch syndrome  Movements of the Glenohumeral Joint Flexion□ pectoralis major, anterior fibres of deltoid, ① coracobrachialis and biceps brachii Extension□ latissimusdorsi ② and the posterior fibres of the deltoid Abduction□ supraspinatus (initiator of abduction up to 15-20 degrees), central deltoid fibres (20-90 degrees of abduction) and the rotation of the scapular achieved by trapezius and serratus anterior (abduction above 90 degrees)  Neurovascular Supply to the Glenohumeral Joint The blood supply is via the ① ② anterior and posterior circumflex humeral arteries and the suprascapular artery. ③ The joint is innervated by the suprascapular, axillary and lateral pectoral nerves. These are all from the brachial plexus roots C5 and C6 therefore upper brachial plexus injuries affect shoulder movement.  Neurovascular relations and clinical application Axillary nerves and circumflex artery are vulnerable when administering an intramuscular injection and during shoulder dislocation. Rotator cuff problems: – Tendons rubbing under coracoid acromion arch – Causes irritation and inflammation of tendons – Can lead to problems  Shoulder Disorders and Injuries Rotator cuff problems – Rotator cuff tendons rubbing under the coraco acromial arch causing irritation and inflammation of the rotator cuff tendons and the subacromial bursa. This can lead to sub acromial bursitis, supraspinatus tendonitis, rotator cuff injury and degeneration or rupture of tendons – Causes of rotator cuff injuries may be due to overuse such as in sports or work involving the overhead use of arms – In older people there are degenerative changes in tendons – Alternatively they may be caused by the avascularity of the supraspinatus tendon or slight differences in anatomy (which may make impingement of the tendons under the coraco acromial arch more likely) – Rotator cuff problems result in painful arc/impingement syndrome where on abduction of the arm there is pain experienced between 70-120 degrees of abduction  Stability of the shoulder joint provided by: Tendons of the rotator cuff (anteriorly, posteriorly and ① superiorly) & Gleno humeral intracapsular ligaments (anteriorly, inferiorly) ③ Coraco humeral ligament (superiorly) ① Coraco acromial arch (superiorly) ⑤ Deepening of the glenoid cavity by the glenoid labrum Splinting effect of the long head of the biceps above and the long head of the triceps below  Dislocation of the glenohumeral joint The inferior aspect of the gleno humeral joint is the least protected and dislocation in the inferior direction is common. The pectoralis major tends to pull the arm anteriorly as it is a powerful adductor so that the humeral head lies below the coracoid process Although a dislocation in the inferior direction, this is clinically defined as an anterior dislocation because the humeral head locates anteriorly due to powerful adductors. The capsule and the rotator cuff tendons may tear, if they heal poorly recurrent dislocation may be experienced  Axillary nerve injury Injured during dislocation due to its close relation to the inferior part of the joint capsule Axillary nerve injury is indicated by: – Paralysis of the deltoid muscle with loss of abduction – Loss of sensation in a small area of the skin (regimental badge area) over the central part of the deltoid.  Adhesive capsulitus Capsulitus Frozen Shoulder Adhesive fibrosis and scarring between: – The inflamed capsule – Rotator cuff – Subacromial bursa – Deltoid Difficulty in abducting the arm Lack of movement of the glenohumeral joint causes strain on the acromioclavicular joint that results in pain when elevating the shoulder In older individuals dislocation, tearing of rotator cuffs, calcific supraspinatus tendonitis and bicipital tendonitis may cause frozen shoulder.  Glenoid Labrum tears Common in athletes and people who have shoulder instability and partial dislocation (sublaxation) of the glenohumeral joint Usual symptom is pain or a popping/snapping feeling  Osteoarthritis of the glenohumeral joint Relatively uncommon cause of shoulder complaints Due to degenerative changes of articular cartilage It tends to be secondary to trauma is most cases, this trauma may have occurred years previously and includes: – Previous dislocation – Humeral head or neck fracture – Large rotator cuff tendon tears Primary osteoarthritis of the shoulder joint is more common in women and those over 60 years Symptoms are similar to frozen shoulder with pain predominating X rays are diagnostic