Sternoclavicular Joint-Movements-Muscles Producing Movement-Important Relations-Sternoclavicular Joint Injuries-Anterior dislocation-Posterior dislocation-

Sternoclavicular Joint

■■ Articulation: This occurs between the sternal end of the clavicle, the manubrium sterni, and the 1st costal cartilage

■■ it s type of joints is: Synovial double-plane joint

■■ Capsule: This surrounds the joint and is attached to the margins of the articular surfaces.

■■ Ligaments: The capsule is reinforced in front of and behind the joint by the strong sternoclavicular ligaments.

■■ Articular disc: This flat fibrocartilaginous disc lies within the joint and divides the joint’s interior into two compartments. Its circumference is attached to the interior of the capsule, but it is also strongly attached to the superior margin of the articular surface of the clavicle above and to the first costal cartilage below.

■■ Accessory ligament: The costoclavicular ligament is a strong ligament that runs from the junction of the 1st rib with the 1st costal cartilage to the inferior surface of the sternal end of the clavicle.

■■ Synovial membrane: This lines the capsule and is attached to the margins of the cartilage covering the articular surfaces.

■■ Nerve supply: The supraclavicular nerve and the nerve to the subclavius muscle.

Movements

Forward and backward movement of the clavicle takes place in the medial compartment. Elevation and depression of the clavicle take place in the lateral compartment.

Muscles Producing Movement

The forward movement of the clavicle is produced by the serratus anterior muscle. The backward movement is produced by the trapezius and rhomboid muscles. Elevation of the clavicle is produced by the trapezius, sternocleidomastoid, levator scapulae, and rhomboid muscles. Depression of the clavicle is produced by the pectoralis minor and the subclavius muscles.

Important Relations

■■ Anteriorly: The skin and some fibers of the sternocleidomastoid and pectoralis major muscles

■■ Posteriorly: The sternohyoid muscle; on the right, the brachiocephalic artery; on the left, the left brachiocephalic vein and the left common carotid artery

Sternoclavicular Joint Injuries

The strong costoclavicular ligament firmly holds the medial end of the clavicle to the 1st costal cartilage. Violent forces directed along the long axis of the clavicle usually result in fracture of that bone, but dislocation of the sternoclavicular joint takes place occasionally.

Anterior dislocation
 results in the medial end of the clavicle projecting forward beneath the skin; it may also be pulled upward by the sternocleidomastoid muscle.

Posterior dislocation
 usually follows direct trauma applied to the front of the joint that drives the clavicle backward. This type is the more serious one because the displaced clavicle may press on the trachea, the esophagus, and major blood vessels in the root of the neck.

If the costoclavicular ligament ruptures completely, it is difficult to maintain the normal position of the clavicle once reduction has been accomplished.