SHOULDER JOINT

 

SHOULDER JOINT

Type: The shoulder joint is a synovial joint of ball and socket variety. The articular surface ligament and bursae related to this important joint are explained below.

Articular surface: The joint is formed by articular of the glenoid cavity of scapula and the head of the humerus. So, it is known as glenohumeral articulation. Structurally, it is a weak joint because glenoid cavity is too small and shallow to hold head of the humerus. It give more a great mobility.

 

Stability of joint is maintained by

• The coracoacromial arch for the head of the humerus.
• The musculotendinous cuff of the shoulder
• Glenoid labrum helps in depending the glenoid fossa.
• Stability is also provided by the muscle attaching the humerus to the pectoral girdle, long head of the biceps brachii and the long head of the triceps brachii.

Ligament: 

1. The capsular ligament
2. The coracohumeral ligament
3. Transverse humeral ligament
4. The glenoid labrum

The capsular ligament: It is very loose and give free movement.  It is less supported inferiorly where dislocation are common. Such dislocation damage closely related to axillary nerve.

• Medially – Capsule is attached to the scapula beyond the supraglenoid tubercle and the margins of the labrum.
• Laterally – Capsular ligament attached to the anatomical neck of the humerus,
• Inferiorly- The attachments extends down to the surgical neck
• Superiorly – Attached to the tendon of the long head of the biceps brachii.
• Anteriorly- The capsule is reinforced by sapplemental bands called the superior, middle , and inferior glenohumeral ligament.

The coracohumeral ligament –  Extends from  root of the coracoid process to  neck of the humerus opposite the greater tubercle.

 

Transverse humeral ligament – It pass the upper part of the bicipital groove of the humerus. Long head of the biceps brachii  tendon passes deep to the liagment.

The glenoid labrum: It is a fibro cartilagenous rim which covers the margins of the glenoid cavity and increase the depth of cavity. 

Bursa related to the joint:

• The subacromial bursa
• The Subscapularis bursa, commonicate withe the joint cavity.
•  Infraspinatus bursa, may communicate with the joint cavity.

Relations: 

• Superiorly: Coracoacromial arch, subacromial bursa, supraspinatus and deltoid.
• Inferiorly – Long head of the triceps brachii, Posterior  circumflex humeral artery and axiallary nerve.
• Anteriorly – Subscapularis, coracobrachialis, short head of the biceps,  brachii  and deltoid.
• Posterior – Infraspinatus, teres minor, and deltoid.

With in the joint : Tendon of the long head of the biceps brachii.

 

Blood supply: 

• Anterior circumflex humeral vessel
• Posterior circumflex humeral vessel
• Suprascapular vessels
• Subscapular vessels

Nerve supply:

• Axillary nerve
• Musculocutaneous nerve
• Suprascapular nerve

Movement of shoulder joint: 

Shoulder joint give great freedom of mobility and the stability. There is no other joint in the body  which is mobile more than shoulder joint.

• Flexion and extensions: During flexion arm move forward  medially. During extension arm move backwards and laterally.  Flexion and extenson take place in sagittal plane from axis. E.g clavicular head and pectoralis major, extension, deltoid, coracobrachialis, and lattismus dorsi.
• Abduction/adduction: In abduction  – Arm move anterolaterally away from the trunk.  Frontal olane and sagitaal axis. E.g Adduction – Pectoralis major, lattismus dorsi, biceps brachii. Abduction : Supraspinoatius, deltoid.

• Medial and lateral rotations: In this position the hand is move medially across the chest in medial rotation and laterally in lateral rotation of the shoulder joint.  E.g medial rotation- pectoralis major, lattismus dorsi. Lateral rotation – deltoid, teres major, infra spinatus and teres minor.
• Circumduction: It is a combination of different movement as a result which hand move along the circle.

• *"DISLOCATION OF THE SHOULDER"* 

• This is the commonest joint in the human body to dislocate. It occurs more commonly in adults, and is rare in children. Anterior dislocation is far more common than posterior dislocation.

Shoulder instability: This is a broad term used for shoulder problems, where head of the humerus is not stable in the glenoid. In the former, the patient may present with just pain within the shoulder, more on using the shoulder. Pain occurs due to stretching of the capsule, as the head ‘moves out’ in some direction without actually dislocating.

The instability may be in one direction (unidirectional) or more (bidirectional). It may be in multiple directions – anterior, inferior, posterior, where it is called multi-directional instability (MDI).

MECHANISM: A fall on an out-stretched hand with the shoulder abducted and externally rotated, is the common mechanism of injury. Occasionally, it results from an immediate force pushing the humerus head out of the glenoid fossa . A posterior dislocation may result from a direct blow on the front of the shoulder, driving the head backwards.

PATHOANATOMY: Classification: Dislocations of the shoulder may be of the following types:

Anterior dislocation: In this injury, the head of the humerus comes out of the glenoid cavity and lies anteriorly. It may be further classified into three subtypes depending on the position of the dislocated head.

• Preglenoid: the top lies ahead of the glenoid.

• Subcoracoid: the top lies below the coracoid process. Most common type of dislocation.

• Subclavicular: The head lies below the clavicle.

Posterior dislocation: during this injury, the top of the humerus involves lie posteriorly, behind the glenoid.

• Luxatio erecta (inferior dislocation): this is often a rare type, where the top involves dwell the subglenoid position.

Pathological changes: The following pathological changes occur in the commoner, anterior dislocation.

Bankart’s lesion: Dislocation causes stripping of the glenoidal labrum along with the periosteum from the antero-inferior surface of the glenoid and scapular neck. The head thus involves dwell front of the scapular neck, within the pouch thereby created. In severe injuries, it may be avulsion of a piece of bone from antero-inferior glenoid rim, called bony Bankart lesion.

Hill-Sachs lesion: This is a depression on the humeral head in its postero-lateral quadrant, caused by impingement by the anterior edge of the glenoid on the head as it dislocates. Rounding off of the anterior glenoid rim occurs in chronic cases because the head dislocates repeatedly over it. There may be associated injuries: like fracture of greater tuberosity, rotator-cuff tear, chondral damage etc.

Essentials of Diagnosis:

• Anterior dislocation is most common, then posterior (50:1)

• Anterior dislocation occurs with the arm abducted and externally rotated; posterior, with the arm flexed and internally rotated.

• Posterior dislocation is less painful than anterior. On physical exam, anterior dislocation produces “fullness” anteriorly and inferiorly; posterior dislocation produces fullness in back, and the coracoid is more prominent.

• Obtain orthogonal radiographic views (very important, especially with posterior dislocations, to avoid missing the diagnosis); scapular “Y” view, axillary view, and AP and “West Point” views permit visualization of occult fractures.

Differential Diagnosis:

Fracture-dislocation of the humerus.

Multidirectional instability.

COMPLICATIONS: Complications are often divided into early and late.

Early complications: Injury to the axillary nerve may occur resulting in paralysis of the deltoid muscle, with a small area of anaesthesia over the lateral aspect of the shoulder. The diagnosis is confirmed by asking the patient to try to abduct the shoulder. Though shoulder abduction may not be possible because of pain, one can feel the absence of contraction of the deltoid. Treatment is conservative, and the prognosis is good.

Late complications: The shoulder is the commonest joint to undergo recurrent dislocation. This results from the following causes: (i) anatomically unstable joint e.g., in Marfan’s syndrome;

(ii) inadequate healing after the first dislocation, or (iii) an epileptic patient.

Treatment

Closed reduction is indicated, with appropriate sedation and analgesia; gentle traction in line with the arm, using some internal and external rotation with appropriate countertraction, generally reduces the dislocation.

Bankart’s operation: The glenoid labrum and capsule are re-attached to the front of the glenoid rim. This is a technically demanding procedure, but has become simpler with the use of special fixation devices called anchors.

Putti-Platt operation: Double-breasting of the subscapularis tendon is performed in order to prevent external rotation and abduction, thereby preventing recurrences.

Immobilization for a short period (1–2 wk) to resolve pain for patients >50 y and for 3–4 wk for younger patients is indicated; the correct length of immobilization and position of immobilization have not been determined. Recurrent dislocation can be treated arthroscopically in many cases. 

TABIB SUHAIL ALAM 🤣