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Shoulder Complex

Table of Contents

The shoulder complex, composed of clavicle, scapula, and humerus, is an intricately designed combination of three joints that links upper extremity to the thorax .

  • The Glenohumeral (GH) joint : which links the humours and scapula, has greater mobility than any other joint in the body.
  • Sternoclavicular (SC) joint, it’s is the only joint in the shoulder complex that connects to the axial skeleton.
  • Acromioclavicular (AC) joint, this joint in the shoulder complex that united the scapula and clavicle at this joint.
  • Scapulothoracic (ST) joint, it is the articulation between the scapula and thorax.
shoulder complex

Sternoclavicular joint

The sternoclavicular joint is a synovial joint. This joint in the shoulder complex has three elements taking part in it; namely the medial end of the clavicle, the clavicular notch of the manubrium sternum, and the upper surface of the first costal cartilage. The sternoclavicular joint is a complex joint as its cavity is subdivided into two compartments, superomedial and inferolateral by an intra- articular disc called the sternoclavicular disc.

Articular surface:

Β The articular surface of clavicle is covered with fibrocartilage.Β  The surface is convex from above downwards and slightly concave from front and back. The sterna surface is smaller than the clavicular surface. It has reciprocal convexity and concavity. Because of the concavo-convex shape of the articular surfaces, the joint can be classified as a saddle joint.

Capsular ligament:

Β The capsular ligament is attached laterally to the margins of the articular areas on the sternum and on the first costal cartilage. It is strong anteriorly and posteriorly where it constitutes

Sternoclavicular disc:

The disc is placed laterally to the clavicle on a rough area above and posterior to the articular area for the sternum. Inferiorly, the disc is placed to the sternum and to the first costal cartilage at their junction. Anteriorly and posteriorly, disc fuses with the capsule.

Ligaments:

There are two other ligaments associated with these joints.

  1. The interclavicular ligament passes between the sterna ends of the right and left clavicles, some of its fibres being attached to the upper border of the manubrium sternum.
  2. The costoclavicular ligament is attached above to the rough area on the inferior aspect of the medial end of the clavicle. Inferiorly, it is attached to the first costal cartilage and to the first rib. It’s consists of anterior and posterior Laminae.
Blood supply: Internal thoracic and suprascapular arteries
Nerve supply:Β  Medial supraclavicular nerve.

Movement:Β 

Β Movement of the sternoclavicular joint can be best understood by visualizing the movement at the lateral end of the clavicle. These movements are elevation/ depression, protraction/retraction, and anterior and posterior rotation of the clavicle. The anterior and posterior rotation of the clavicle is utilized in the overhead movement of the shoulder complex.

Acromioclavicular joint

The acromioclavicular joint in shoulder complex is a plan and synovial joint. It is formed by the articulation of small facets present:

  1. At the lateral end of the clavicle.
  2. On the medial margin of the acromion process of the scapula

The facets are covered with fibrocartilage. The cavity of the joint is subdivided by an articular disc which may have a perforation in it. The bones are held together by fibrous capsule and by articular disc. However, the main bond of union between scapula and clavicle is the coracoclavicular ligament.

Blood supply:

Suprascapular and Thoracoacromial arteries.

Nerve supply: Lateral supraclavicular nerve.

Movement:

Elevation and depression, protraction and retraction, Lateral or forward rotation, Medial or backward rotation

Β Β SCAPULOTHORACIC JOINT

The scapulothoracic joint is the only joint in shoulder complex that is not a true anatomic joint because it is not a union of bony segments by fibrous, cartilaginous, or synovial tissue

Β GLENOHUMERAL JOINT

The shoulder joint is a synovial joint of the ball and socket type of joint in the shoulder complex.

Articular surface: The joint is formed by the articulation of the glenoid cavity ofΒ  scapula and head of humours.

Ligament:

there is two types of ligamentΒ 

  1. Capsular ligament: it consist of the medial glenohumeral ligament, superior glenohumeral ligament, inferior ligament
  2. Extracapsular ligament: it consists of coracohumeral ligament

Relation

  1. Superiorly: Coracoacromial arch, subacromial bursa, supraspinatus ,deltoid.
  2. Inferiorly: Long head of the triceps brachii, axillary nerve, and posterior circumflex humeral artery.
  3. Anteriorly: Subscapularis, coracobrachialis, the short head of biceps brachii and deltoid.
  4. Posteriorly: Infraspinatus, teres minor, and deltoid.
  5. Within the joint; Tendon of the long ,hand of the biceps brachii.

Blood supply

  1. Anterior circumflex humeral vessels.
  2. posterior circumflex humeral vessels.
  3. Suprascapular vessels
  4. Subscapular vessels

Nerve supply

  1. Axillary nerve
  2. Musculocutaneous nerve
  3. Suprascapular nerve

Movement:

Flexion and extension, Abduction and adduction, Medial and lateral rotation, circumduction.

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