ACROMIOCLAVICULAR AND STERNOCLAVICULAR DISLOCATION
Acromioclavicular (AC) dislocations, otherwise commonly called “AC separations,” are common injuries after trauma associated with landing on the superior aspect of the shoulder. These are commonly seen in football injuries as well as from injuries sustained in bicycling or other riding accidents when someone falls from the bike or a horse and lands on the superior aspect of the shoulder. AC separation is classified into six different types depending on the amount of damage to the soft tissues and the orientation of the distal end of the clavicle:
Grade I: Sprain of the AC capsulary ligaments.
Grade II: Complete disruption of the AC capsule ligaments and the strain of the coracoclavicular ligaments.
Grade III: Complete disruption of the AC ligaments and coracoclavicular ligaments, resulting in an unstable clavicle segment. The distal clavicle appears to be superiorly displaced, but on more careful review of the radiographs or on physical examination it can be seen that the clavicles are at the same height and the scapula and humeral are displaced distally by gravity and the weight of the arm.
Grade IV: Grade III ligament injuries but with dis- ruption of the trapezius fascia, thus resulting in a posterior dislocation of the distal end of the clavi- cle through the trapezius muscle. This type of injury is best seen on the axillary radiographic view and on physical examination.
Grade V: Lesions with more extensive soft tissue damage. In addition to injury to the AC and coracoclavicular ligaments, there is complete disrup- tion of the deltotrapezial fascia and very significant displacement between the clavicle and scapular bone, usually affecting two to three widths of the distal clavicle.
Grade VI: Rare injuries that result from complete ligamental disruption and displacement of the distal end of the clavicle under the corticoid.
Most grade I, II, and III injuries are treated by non operative measures. Grade IV, V, and VI injuries are generally treated by surgical reconstruction of the ligaments and reduction of the clavicle to the acromion. In some patients with grade III lesions who either have persistent symptoms of pain or fatigue or have a high physical demand, reconstruction of the AC joint and ligament attachments is performed.
Anterior sternoclavicular dislocation is often a result of high-velocity traumatic lesions resulting from a direct blow to the anterior aspect of the shoulder. Disruption of the sternoclavicular and costoclavicular ligaments results in a complete anterior dislocation of the sternoclavicular joint. In many cases, this will result in severe deformity and significant swelling. In many of these cases, closed reduction cannot be achieved with maintenance of joint reduction. These injuries are often treated nonoperatively because many of these patients, particularly those with lower functional bands, will have minimal symptoms. If there is significant residual pain or limitations of function, then later reduction and ligament reconstruction can be performed in those selected patients. Posterior dislocation of the sternoclavicular joint is a more serious traumatic lesion because there can be injury or compression of the underlying neurovascular structures. In these cases, closed reduction under general anesthesia is performed. On occasion, an open reduction and ligament reconstruction may be required. The growth plate at the medial end of the clavicle does not close in most individuals until the early 20s. Trauma and deformity in these younger patients often result in fracture through the growth plate. These growth plate injuries heal as a fracture, the ligaments are not torn, and the clavicle after healing is not unstable. Although there may be a deformity, most of these patients are asymptomatic.