ACROMIOCLAVICULAR AND

STERNOCLAVICULAR JOINT INJURIES

ACROMIOCLAVICULAR JOINT INJURY

Epidemiology

It is most common in the second decade of life, associated with contact athletic activities.

Acromioclavicular (AC) dislocations represent 9% to 10% of acute traumatic injuries to the shoulder girdle.

It is more common in males (approximately 5:1).

Anatomy (Fig. 12.1)

The AC joint is a diarthrodial joint, with fibrocartilage-covered articular surfaces, located between the lateral end of the clavicle and the medial acromion.

Inclination of the plane of the joint may be vertical or inclined medially 50 degrees.

The AC ligaments (anterior, posterior, superior, inferior) strengthen the thin capsule. Fibers of the deltoid and trapezius muscles blend with the superior AC ligament to strengthen the joint.

The AC joint has minimal mobility through a meniscoid, intra-articular disc that demonstrates an

age-dependent degeneration until it is essentially nonfunctional beyond the fourth decade.

The horizontal stability of the AC joint is conferred by the AC ligaments, whereas the vertical stability is maintained by the coracoclavicular ligaments (conoid–medial, trapezoid–lateral).

Deltoid and trapezius fascial attachments reinforce the superior AC ligament contributing to vertical stability as a secondary stabilizer.

The average coracoclavicular distance is 1.1 to 1.3 cm.

Mechanism of Injury

Direct: This is the most common mechanism, resulting from a fall onto the shoulder with the arm adducted, driving the acromion medial and inferior.

Indirect: This is caused by a fall onto an outstretched hand with force transmission through the humeral head and into the AC articulation (Fig. 12.2).

Associated Fractures and Injuries

Fractures: clavicle, acromion process, and coracoid process

Pneumothorax or pulmonary contusion with type VI AC separations

Clinical Evaluation

The patient should be examined while in the standing or sitting position with the upper extremity in a dependent position, thus stressing the AC joint and emphasizing deformity.

The characteristic anatomic feature is a downward sag of the shoulder and arm.

A standard shoulder examination should be performed, including assessment of neurovascular status and possible associated upper extremity injuries. Inspection may reveal an apparent step-off deformity of the injured AC joint, with possible tenting of the skin overlying the distal clavicle. Range of shoulder motion may be limited by pain. Tenderness may be elicited over the AC joint.

Radiographic Evaluation

A standard trauma series of the shoulder (anteroposterior [AP], scapular-Y, and axillary views) is usually sufficient for the recognition of AC injury. The Zanca view is taken with the x-ray beam in 10 to 15 degrees of cephalic tilt. This view allows better visualization of the distal clavicle.

Ligamentous injury to the coracoclavicular joints may be assessed via stress radiographs, in which weights (10 to 15 lb) are strapped to the wrists, and an AP radiograph is taken of both shoulders to compare coracoclavicular distances (difficult to do in the acute setting).

Classification

This injury is classified depending on the degree and direction of displacement of the distal clavicle (Table 12.1 and Fig. 12.3).

Treatment

Type I: Rest for 7 to 10 days, ice packs, sling. Refrain from full activity until painless, full range of motion (2 weeks).

Type II: Sling for 1 to 2 weeks, gentle range of motion as soon as possible. Refrain from heavy activity for 6 weeks. More than 50% of patients with types I and II injuries remain symptomatic at long-term follow-up.

Type III: For inactive, nonlaboring, or recreational athletic patients, especially for the nondominant arm, nonoperative treatment is indicated: sling, early range of motion, strengthening, and acceptance of deformity. Younger, more active patients with

more severe degrees of displacement and laborers who use their upper extremity above the horizontal plane may benefit from operative stabilization. Repair is generally avoided in contact athletes because of the risk of reinjury.

Types IV–VI: These are generally treated with open reduction and surgical repair or reconstruction of the coracoclavicular ligaments is performed for vertical stability, although no level-one evidence for this treatment exists.

Complications

Coracoclavicular ossification: Not associated with increased disability

Distal clavicle osteolysis: Associated with chronic dull ache and weakness

AC arthritis

STERNOCLAVICULAR JOINT INJURY

Epidemiology

Injuries to the sternoclavicular (SC) joint are rare; Cave et al. reported that of 1,603 shoulder girdle dislocations, only 3% were SC, with 85% glenohumeral and 12% AC dislocations.

Approximately 80% of dislocations of the SC joint are caused by either motor vehicle accident (47%) or are sports related (31%).

Anatomy (Fig. 12.4)

The SC joint is a diarthrodial joint, representing the only true articulation between the upper

extremity and the axial skeleton.

The articular surface of the clavicle is much larger than that of the sternum; both are covered with fibrocartilage. Less than half of the medial clavicle articulates with the sternum; thus, the SC joint has the distinction of having the least amount of bony stability of the major joints of the body.

Joint integrity is derived from the saddle-like configuration of the joint (convex vertically and concave anteroposteriorly), as well as from surrounding ligaments:

• The intra-articular disc ligament is a checkrein against medial displacement of the clavicle.

• The extra-articular costoclavicular ligament resists rotation and medial–lateral displacement.

• The interclavicular ligament helps to maintain shoulder poise.

Range of motion is 35 degrees of superior elevation, 35 degrees of combined AP motion, and 50 degrees of rotation around its long axis.

The medial clavicle physis is the last physis to close. It ossifies at 20 years and fuses with the shaft at 25 to 30 years. Therefore, many supposed SC joint dislocations may actually be physeal injuries.

Mechanism of Injury (Fig. 12.5)

Direct: Force applied to the anteromedial aspect of the clavicle forces the clavicle posteriorly into the mediastinum to produce posterior dislocation. This may occur when an athlete is in the supine position and another athlete falls on him or her, when an individual is run over by a vehicle, or when an individual is pinned against a wall by a vehicle.

Indirect: Force can be applied indirectly to the SC joint from the anterolateral (producing anterior SC dislocation) or posterolateral (producing posterior SC dislocation) aspects of the shoulder. This is most commonly seen in football “pileups,” in which an athlete is lying obliquely on his shoulder and force is applied with the individual unable to change position.

Clinical Evaluation

The patient typically presents supporting the affected extremity across the trunk with the contralateral, uninjured arm. The patient’s head may be tilted toward the side of injury to decrease

stress across the joint, and the patient may be unwilling to place the affected scapula flat on the examination table.

Swelling, tenderness, and painful range of shoulder motion are usually present, with a variable change of the medial clavicular prominence, depending on the degree and direction of injury.

Neurovascular status must be assessed, because the brachial plexus and major vascular structures are in the immediate vicinity of the medial clavicle.

With posterior dislocations, venous engorgement of the ipsilateral extremity, shortness of breath, painful inspiration, difficulty swallowing, and a choking sensation may be present. The chest must be auscultated to ensure bilaterally symmetric breath sounds.

Radiographic Evaluation

AP chest radiographs typically demonstrate asymmetry of the clavicles that should prompt further radiographic evaluation. This view should be scrutinized for the presence of pneumothorax if the patient presents with breathing complaints.

Hobbs view: In this 90-degree cephalocaudal lateral view, the patient leans over the plate, and the radiographic beam is angled behind the neck (Fig. 12.6).

Serendipity view: This 40-degree cephalic tilt view is aimed at the manubrium. With an anterior dislocation, the medial clavicle lies above the interclavicular line; with a posterior dislocation, the medial clavicle lies below this line (Fig. 12.7).

Computed tomography (CT) scan: This is the best technique to evaluate injuries to the SC joint. CT is able to distinguish fractures of the medial clavicle from dislocation as well as delineate minor subluxations that would otherwise go unrecognized.

Classification

Anatomic

Anterior dislocation: More common

Posterior dislocation

Etiologic

Sprain or subluxation

• Mild: joint stable, ligamentous integrity maintained

• Moderate: subluxation, with partial ligamentous disruption

• Severe: unstable joint, with complete ligamentous compromise

Acute dislocation: complete ligamentous disruption with frank translation of the medial clavicle

Recurrent dislocation: rare

Unreduced dislocation

Atraumatic: may occur with spontaneous dislocation, developmental (congenital) dislocation, osteoarthritis, condensing osteitis of the medial clavicle, SC hyperostosis, or infection

Treatment

Mild sprain: Ice is indicated for the first 24 hours with sling immobilization for 3 to 4 days and a gradual return to normal activities as tolerated.

Moderate sprain or subluxation: Ice is indicated for the first 24 hours with a clavicle strap, sling and swathe, or figure-of-eight bandage for 1 week, then sling immobilization for 4 to 6 weeks.

Severe sprain or dislocation (Fig. 12.8)

• Anterior: As for nonoperative treatment, it is controversial whether one should attempt closed reduction because it is usually unstable; a sling is used for comfort. Closed reduction may be accomplished using general anesthesia, or narcotics and muscle relaxants for the stoic patient. The patient is placed supine with a roll between the scapulae. Direct, posteriorly directed pressure usually results in reduction. Postreduction care consists of a clavicle strap, sling and swathe, or figure-of-eight bandage for 4 to 6 weeks. Some advocate a bulky anterior dressing with elastic tape to maintain reduction.

• Posterior: A careful history and physical examination are necessary to rule out associated

  pulmonary or neurovascular problems. Prompt closed or open reduction is indicated, usually under general anesthesia. Closed reduction is often successful and remains stable. The patient is placed supine with a roll between the scapulae. Closed reduction may be obtained with traction with the arm in abduction and extension. Anteriorly directed traction on the clavicle with a towel clip may be required. A clavicle strap, sling and swathe, or figure-of-eight bandage is used for immobilization for 4 to 6 weeks. A general or thoracic surgeon should be available in the event that the major underlying neurovascular structures are inadvertently damaged.

   

   

   

Medial physeal injury: Closed reduction is usually successful, with postreduction care consisting of a clavicle strap, sling and swathe, or figure-of-eight bandage immobilization for 4 to 6 weeks.

Operative management of SC dislocation may include fixation of the medial clavicle to the sternum using fascia lata, subclavius tendon, or suture, osteotomy of the medial clavicle, or resection of the medial clavicle. The use of Kirschner wires or Steinmann pins is discouraged, because migration of hardware may occur.

Complications

Poor cosmesis is the most common complication with patients complaining of an enlarged medial prominence.

Complications are more common with posterior dislocations and reflect the proximity of the medial clavicle to mediastinal and neurovascular structures. The complication rate has been reported to be as high as 25% with posterior dislocation. Complications include the following:

• Pneumothorax

• Laceration of the superior vena cava

• Venous congestion in the neck

• Esophageal rupture

• Subclavian artery compression

• Carotid artery compression

• Voice changes