AC joint separation is also known as the “separated shoulder”. It occurs when the capsule of the AC joint is damaged.
It occurs in people who participate in sports. There are 6 types of classifications to the injury. The most common type of injury that causes the separation is a fall on the tip of the shoulder or outstretched hand.
Type I: Sprain
This is an AC separation that involves trauma to the ligaments that form the joint, but no severe tearing or fracture.
Type II:
This type is an AC separation that involves complete tearing of the acromioclavicular ligament, sprain or partial tear of the coracoclavicular ligaments. This often causes a noticeable bump on the shoulder. The bump is permanent.
Type III:
Both acromioclavicular and coracoclavicular ligaments are torn. The bump is formed.
Type IV:
This is a type III injury with avulsion of the coracoclavicular ligament from the clavicle, with the distal clavicle displaced posteriorly into or through the trapezius. This injury generally requires surgery.
Type V:
This is a type III injury with an exaggeration of the vertical displacement of the clavicle from the scapula. This injury generally requires surgery.
Type VI:
This is a type III with inferior dislocation of the lateral end of the clavicle below the coracoid. This type is extremely rare, and it’s generally only involved with motor vehicle collisions. This requires surgery.