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.
