Sternoclavicular and Acromioclavicular Joint Injuries

I. STERNOCLAVICULAR INJURIES

A. General information

Anatomy and mechanism. The sternoclavicular joint is a diarthrodial joint between the medial clavicle and the clavicular notch of the sternum. Although there is little intrinsic osseous stability, the sternoclavicular ligaments are reinforced by the costoclavicular (rhomboid) ligaments, intraarticular disc ligament, interclavicular ligament, and joint capsule. Because of strong ligamentous support, injuries to the sternoclavicular joint are rare, representing only 3% of shoulder girdle injuries.¹

The sternoclavicular joint is the only true articulation between the axial and appendicular skeleton, and allows for motion in all planes. The majority of scapulothoracic motion occurs through the sternoclavicular joint, which is capable of approximately 35° of upward elevation, 35° of combined anterior-posterior motion, and 45° of rotation around its long axis.

The clavicle is the first long bone to ossify (fifth week in utero), however, the medial epiphysis is the last long bone ossification center to appear (18 to 20 years) and the last epiphysis to close (23 to 25 years).²

A sternoclavicular injury is always a high-energy event, and, therefore, other injuries should be expected. Owing to the posterior proximity of critical structures such as the great vessels, phrenic and vagus nerves, trachea, and esophagus, associated injuries should be diagnosed promptly.

The mechanism of injury can either be from a direct or indirect force applied to the shoulder. A direct blow to the anteromedial clavicle can result in a posterior dislocation behind the sternum. In an indirect mechanism, a medial force vector compresses the shoulder and loads the sternoclavicular joint. If the medial force drives the scapula posteriorly (retracted) along the thorax, the sternoclavicular joint dislocates anteriorly, and if driven anteriorly (protracted), the sternoclavicular joint dislocates posteriorly.

2. Classification. Sternoclavicular joint injuries can be classified by several ways including the degree of instability, timing, direction, and cause.¹ The sternoclavicular joint may sustain a simple sprain that is stable but painful, joint instability and subluxation, or frank dislocation, depending on the degree of ligament disruption.³ More importantly, sternoclavicular dislocations are described according to the direction of dislocation, anterior or posterior dislocation. Anterior dislocations are more common.

An important point to distinguish is the possibility of a medial clavicular physeal fracture that can displace anteriorly or posteriorly as well, thus mimicking a dislocation. This should be suspected in patients with sternoclavicular joint injuries under the age of 25. Most of these injuries heal and remodel without surgical intervention.¹

As an aside, there is an atraumatic type of dislocation due to ligamentous laxity, but emphasis in this chapter will remain on the traumatic variety.

B. Diagnosis

History and physical examination. The history is always significant for a high-energy mechanism. The patient should be asked about the presence of shortness of breath and difficulty breathing or swallowing, particularly upon recognition of a posterior dislocation. Hoarseness, persistent cough, and stridor should be documented. Patients may have distended neck veins secondary to local venous congestion. Pain is well localized and associated with swelling and ecchymosis. There is usually a palpable and mobile prominence just anterior and lateral to the sternal notch in the case of an anterior dislocation, or perhaps a puckering of the skin with a sense of fluctuance due to a posterior dislocation. Chest auscultation and a thorough neurovascular examination to the ipsilateral extremity are important to document early.
Radiographs. Anteroposterior radiographs of the chest or clavicle are often of limited usefulness when assessing for sternoclavicular joint injuries. A serendipity X-ray view of the shoulder is a 40° cephalic tilt view centered on the manubrium.² In this view, an anterior dislocation will be manifested with a superior appearing clavicular head.

Once suspected, a computed tomography (CT) examination with 2-mm interval cuts should also be obtained to visualize the location and extent of dislocation, evaluate the retrosternal region for soft tissue injury, physeal injury. If a vascular injury is suspected, the CT scan can be combined with an arteriogram of the great vessels.

An MRI can be considered to further evaluate the sternoclavicular joint anatomy and location of critical soft-tissue structures. An MRI may be helpful in distinguishing between a dislocation and physeal injury in children and young adults.

C. Treatment

Nonoperative. Most sternoclavicular injuries are anterior dislocations, and these should be treated nonoperatively with the expectation of potential cosmetic asymmetry associated with good functional results and usually with complete resolution of pain.⁴ Closed reduction can be attempted; however, the joint usually will not remain reduced, and no brace has been proven to be efficacious in this regard. This expectant result also holds true for the growth plate injuries that are displaced anteriorly.
Operative. It is mostly agreed upon that surgical intervention of anterior sternoclavicular joint dislocations is unwarranted, with the risks outweighing the benefits of an open reduction.³ A posterior dislocation should undergo a manipulative reduction to unlock the retrosternal clavicular head. The rationale for the need for closed reduction relates to the concern that impingement on critical structures may yield late sequelae from erosion or irritation.⁵

A pointed bone tenaculum may be useful to grab the head of the clavicle and pull it back to its proper relation to the manubrium. A roll between the shoulder blades while the patient is supine, in combination with lateral traction of the abducted arm, is a helpful adjunctive maneuver. A closed reduction maneuver is not always successful. Due to possible violation of critical structures in the mediastinum, anesthesia should always be on hand to manage the airway, and a thoracic surgeon should be on standby during the procedure. Performing the reduction maneuver under general anesthesia with optimum airway control should be considered.

Many authors have described techniques for stabilization of the unstable sternoclavicular joint using various tendon reconstructions, medial clavicle osteotomy or resection, and/or Kirschner wire fixation with mixed results.⁶ A warning against the use of any transfixing wires across the sternoclavicular joint is restated throughout the literature due to the reported problem of wire migration. In the patient with an open physis, sometimes a reduction of the dislocated distal fragment can be reinforced with heavy braided suture through drill holes in the distal fragment.

3. Follow-up. A sling with an abduction pillow may be used for 1 month to support the extremity during the acute phase of pain during a period of relative immobility. Motion and function should be allowed to advance as discomfort allows. The patient may need reassurance for months during a period of gradually resolving symptoms.

4. Complications. Retrosternal dislocations are frequently missed, likely due to the lack of physical examination findings in the context of a multiply injured patient.⁷ Missed or late diagnosis of associated injuries of the mediastinum and brachial plexus are well documented. With nonoperatively treated anterior dislocations, the patient should anticipate a significant prominence, which is a significant cosmetic concern for some patients. Failure of fixation, hardware migration, and redislocation have also been reported after operative stabilization and are likely due to the high forces acting on this main articulation between the upper extremity and the axial skeleton.⁸

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