SHOULDER JOINT (ANATOMY ) Part I

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 SHOULDER JOINT 

STRUCTURE PRESENT IN THE SHOULDER JOINT

  1. Glenohumeral joint 
  • labrum
  • Rotator cuff muscles
  • Ligaments of the Glenohumeral joint 
  • Rotator interval
      2.Acromioclavicular joint 
  • Ligaments of the acromioclavicular joint
      3.Sternoclavicular joint 
  • Ligaments of the sternoclavicular joint 
       4.Scapulothoracic joint


GLENOHUMERAL JOINT 


  • Multiaxial , ball and socket , synovial joint that depends primarily on the muscles and ligaments rather the bone for its support , stability and integrity .
  • LABRUM which is the ring of fibrocartilage , surrounds and deepens the glenoid cavity of the scapula about 50%. 
  • GH joint has three axes and three degree of freedom 
  • RESTING POSITION OF GH JOINT is 55 degree abduction and 30 degree horizontal adduction 
  • RESTING POSITION OF THE GLENOID is 5 degree superior tilt or inclination and 7 degree retroversion ( slight medial rotation ) .
  • The angle between the humeral head and shaft is about 130 degree .
  • The humeral head is retroverted 30 to 40 degree relative to the line joining the epicondyle.
  • The ROTATOR CUFF MUSCLES plays an integral role in shoulder joint movements.It controls osteokinematic and arthrokinematic motion of the humeral head in the glenoid and along with bicep depresses the humeral head during movements in to elevation .
LIGAMENTS OF GLENOHUMERAL JOINT 

1.SUPERIOR GLENOHUMERAL LIGAMENTS :
  • Limiting inferior translation in adduction 
  • Restrains anterior translation and lateral rotation up to 45 degree abduction .

2.MIDDLE GLENOHUMERAL LIGAMENTS:
  • Absent in 30 % of the population 
  • Limits lateral rotation between 45 degree to 90 degree abduction 

3.INFERIOR GLENOHUMERAL LIGAMENTS:
  • Most important ligaments 
  • It support the humeral head above 90 degree abduction 
4.CORACOHUMERAL LIGAMENTS 
  • limiting inferior translation and helps limit the lateral rotation below 60 degree abduction .
  • ROTATOR INTERVAL consist of the fibers of the coracohumeral ligaments , superior glenohumeral ligament,glenohumeral joint capsule and part of the tendon of supraspinatus and subscapularis.Injury to tehse structures can lead to contractures ,bicep tendon instability and anterior glenohumeral instability .
5.CORACOACROMIAL LIGAMENT
  • Form an arch over the humeral head 
  • Acting as a block to superior translation 
6-TRANSVERSE HUMERAL LIGAMENTS
  • Form a roof over the bicipital groove to hold the head of biceps tendon with in the groove .

  • CAPSULAR PATTERN of the glenohumeral joint is lateral rotation most limited , followed by abduction and medial rotation 
  • Branches of the posterior cord of brachial plexus and suprascapular , axillary and lateral pectoral nerve innervate the joint
  • CLOSED PACK POSITION of the joint is full abduction and lateral rotation . 
ACROMIOCLAVICULAR JOINT 


  • Plane synovial joint that augments the range of motion of the humerus in the glenoid.
  • Bones making up the joint are the acromion process of scapula and lateral end of clavicle .
  • Acromion may have different undersurface shapes and types : TYPE I -Flat , TYPE 11 CURVED , TYPE III-HOOKED , TYPE IV - CONVEX (UPTURNED)
  • About 70 % of the rotator cuff tear associated with the hooked acromion .
  • Joint has three degree of freedom 
  • Capsule which is fibrous surround the joint 
  • Articular disc may be found within the joint
  • Joint depend on ligament for its strength .
LIGAMENTS OF ACROMIOCLAVICULAR JOINT 

ACROMIOCLAVICULAR LIGAMENT
  • Surrounds the joint and control horizontal motion of clavicle 
  • first ligament is injured when the joint is stressed
CORACOCLAVICULAR LIGAMENT
  • Primary support of the acromioclavicular joint 
  • It has two portion ; the conoid(medial) and trapezoid(lateral) part.
  • Control the verticle motion of clavicle 
  • If a step deformity occurs, this ligament has been torn 

  • In the RESTING POSITION OF THE JOINT , the arm rest by the side in the normal, standing position .
  • In the CLOSE PACKED POSITION , the arm is abducted to 90 degree.
  • The indication of the CAPSULAR PATTERN in the joint is the pain at the extreme ROM, especially in the horizontal adduction ( cross flexion) and full elevation .
  • This joint is innervated by the branches of the suprascapular and lateral pectoral nerve.

STERNOCLAVICULAR JOINT 


  • Enables the humerus in the glenoid to move through a full 180 degree of abduction .
  • It is a saddle shaped synovial joint with three degree of freedom 
  • Made up of the medial end of the clavicle , the manubrium sternum and the cartilage of 1st rib.
  • It is the joint that joins the appendicular skeleton to the axial skeleton.

LIGAMENTS OF STERNOCLAVICULAR JOINT 

ANTERIOR AND POSTERIOR STERNOCLAVICULAR LIGAMENT
  • It supports the joint anteriorly and posteriorly 
INTERCLAVICULAR LIGAMENT

COSTOCLAVICULAR LIGAMENT
  • Running from the clavicle to the first rib and its costal cartilage 
  • Main ligament that maintain the integrity of the joint 

  • CLOSE PACKED POSITION is full or maximum rotation of the clavicle , which occur when the arm is in full elevation.
  • In the CLOSE PACKED POSITION , the arm is abducted to 90 degree.
  • The indication of the CAPSULAR PATTERN in the joint is the pain at the extreme ROM, especially in the horizontal adduction ( cross flexion) and full elevation .
  • The joint is innervated by branches of the anterior supraclavicular nerve and nerve to the subclavius muscle . Major vessels and the trachea lie close behind the sternum and the sternoclavicular joint.

SCAPULOTHORACIC JOINT 


  • Not a true joint 
  • Function as an integral part of the shoulder complex
  • considered in any assessment because a stable scapula enables the rest of the shoulder to function correctly .
  • Also called this structure is scapulocostal joint.
  • Consist of the body of scapula and muscle covering the posterior chest wall.

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