The Shoulder Joint

Define the difference between shoulder separation and shoulder dislocation. lA

shoulder separation involves injury to the ligaments of the Acromial-clavicular joint.

l lThe

ligaments involved are the acromialclavicular ligament and the coracoclavicular ligament.

A shoulder dislocation is when the head of the humerus dislocates from the glenoid fossa

Joints of the upper limb

lMovement

of the pectoral girdle involves the sternoclavicular, acromioclavicular, and glenohumeral joints usually all moving simultaneously. lFunctional defects in any of the joints impair movements of the pectoral girdle. Mobility of the scapula is essential for free movement of the upper limb.

lIn

the overall movement of fully elevating the arm, the movement occurs in a 2:1 ratio: l2/3 in glenohumeral and 1/3 in shoulder girdle. This is known as scapulohumeral rhythm.

Shoulder joint (glenohumeral joint) l synovial

joint. l Ball and socket type l Head of the humerus articulates with the glenoid cavity of scapula.

Shoulder joint l Articular

surfaces are most incongruent. l More dynamic joint but less stable. l Dislocations are common.

Fibrous capsule l The

fibrous capsule is loose and lax to provide mobility. l Inferiorly it is not supported-- so dislocations are common here.

A posterior view of a dissected glenohumeral joint. An incision has been made into the joint capsule and the humerus has been retracted laterally and rotated posteriorly.

Factors strengthening the joint lCoraco

acromial arch(additional socket for the head) lRotator cuff lGlenohumeral ligaments(inside the capsule) lLong head of

A note about coracoacromial arch

The coracoacromial arch is so strong that a forceful superior thrust of the humerus will not fracture it; the humeral shaft or clavicle fractures first!!!!.

Shoulder Joint vThe

glenoid labrum deepens the socket. vThe tendon of the long head of the biceps brachii passes through the shoulder joint cavity.

Biceps tendon

SITS(rotator cuff)

SYNOVIAL MEMBRANE

Movements l Abduction---middle

fibres of deltoid,supraspinatus,serratus anterior l Adduction-subscapularis,latissimus dorsi l Flexion-P.Major,anterior fibres of deltoid l Extension- posterior fibres of deltoid,latissimus dorsi l Circumduction

Abduction at the shoulder l 0-15º

by supraspinatus l 15º- 90º by the deltoid l >90º(over head abduction) by serratus anterior l

Blood supply

The glenohumeral joint is supplied by the anterior and posterior circumflex humeral arteries and branches of the suprascapular artery

Nerve supply The suprascapular, axillary, and lateral pectoral nerves supply the glenohumeral joint

Bursae vVarious

bursae are present between the tendons of rotator cuff muscles and the shoulder joint. vInflammation of any of these ( e.g.subacromial bursa) may result in painful shoulder.

Subacromial bursa

Subacromial bursitis l This

bursa lies between the supraspinatus tendon and acromion to protect the tendon. l It is continued below the deltoid as “subdeltoid bursa” and is the largest bursa in the body. l If it is inflamed, the person will have pain during abduction and no pain at all in adduction of the shoulder.

Dawbarn’s sign l In

subacromial bursitis, pain is elicited by pressure on deltoid just below the acromion when the arm is adducted but no pain will be felt when the arm is abducted to 90º( Dawbarn’s sign)

Normal AP view of the shoulder Humeral head slightly overlaps the glenoid -

“crescent sign”

Anterior (inferior) dislocation ( 95% ) Humeral head is located antero medially and inferiorly to glenoid

Posterior dislocation Absence of “crescent sign”

Axillary Nerve Injury The axillary nerve may be injured when the glenohumeral joint dislocates because of its close relation to the inferior part of the joint capsule of this joint. The subglenoid displacement of the head of the humerus into the quadrangular space damages the axillary nerve. .

Axillary nerve injury is indicated by paralysis of the deltoid (manifest as an inability to abduct the arm to or above the horizontal level) and loss of sensation in a small area of skin covering the central part of the deltoid.

Shoulder pain vRotator

cuff Syndrome Fibrosis & calcification of supraspinatus tendon.

vFrozen

shoulder Adhesive capsulitis - stiff and painful due to immobilization

vTendinitis

and Bursitis. The supraspinatus and long head of the biceps are especially susceptible.

Shoulder joint in MRI

Shoulder replacement