AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Background

The clavicle derives its name from the Latin word clavicula, or small key, because of its unique curvature. Despite the high frequency of injuries to the clavicle, our understanding of its injuries and function is based on only a modest amount of data. It has long been thought that the inherent reparative capacity of the bone leads to its rapid healing with little more than symptomatic treatment. Deformity has been described as merely a cosmetic concern because function is satisfactory despite malunion.

Clavicular fractures are classified by their location. The most common injury is a type 1 fracture, which affects the middle third of the clavicle (see Images 1-2). Type 2 fractures involve the lateral third, distal to the coracoclavicular ligament (see Image 3). These can be further subdivided into fractures with or without disruption of the ligament itself. The least common injury, type 3, is a fracture of the proximal third (see Image 4).

Pathophysiology

Clavicular integrity fails most commonly in compression. The usual mechanism of injury involves a direct force applied to the lateral aspect of the shoulder as a result of a fall, sporting injury, or motor vehicle accident. The same mechanism may also result in dislocations of the 2 articulations of the clavicle (ie, the sternum in the medial aspect and the acromion process in the lateral aspect).

The middle section of the clavicle is relatively unsupported by muscular or ligamentous attachments, and it is also the transition point between the relatively flat cross-section at the lateral portion and the relatively tubular cross-section at the medial portion. This arrangement is likely the reason that most fractures of the clavicle occur in this region.

Anterior dislocations of the sternoclavicular (SC) joint, which are more common than posterior dislocations, are usually the result of a posterolateral blow that thrusts the shoulder forward (see Image 5). Likewise, most acromioclavicular (AC) dislocations are the result of a direct force on the point of the shoulder. This forces the scapula downward and medially. When this force occurs, the relatively weak AC ligaments are the first to rupture. With increasing force, the coracoclavicular ligament ruptures, and the attachments of the deltoid and trapezius muscles are torn from the distal clavicle. The proximal fragment is generally displaced superiorly and posteriorly due to the pull of the sternocleidomastoid muscle.

Frequency

United States

Injuries to the clavicle account for 5% of all fractures, and the clavicle is the most commonly fractured bone during childhood. According to the American Academy of Orthopaedic Surgeons, clavicular fractures occur with a frequency of about 1 case per 1000 people per year. Epidemiologic studies in adults have documented an annual incidence of roughly 40 cases per 100,000 individuals, with a male-to-female ratio of 2:1 . Midshaft fractures account for approximately 85% of all clavicular fractures, whereas distal injuries account for 10%, and proximal fractures, 5%.

Clavicular fractures also represent more than 90% of obstetric fractures and have a prevalence of 1 in every 213 live births. They occur equally in male and female individuals and on both sides of the body.

Although the SC joint is the least stable joint in the body, SC dislocations represent less than 1% of all joint dislocations and 3% of shoulder injuries. Anterior dislocations are 20 times more common than posterior dislocations. Almost 9% of shoulder-girdle injuries involve damage to the AC joint, and more than 40% of AC joint injuries occur in adults in their 20s. AC dislocations are 5 times more common in males than in females.

Mortality/Morbidity

Fractures of the middle third of the clavicle have been associated with damage to the neurovascular bundle and the pleural dome. However, more often than not, this injury is merely cosmetic.

Complications occurring after fractures of the medial third of the clavicle resemble those associated with posterior SC dislocations. Injuries to intrathoracic and superior mediastinal structures may be complications in as many as 25% of posterior dislocations. Neurovascular injury, pneumothorax, and hemothorax have been reported.

Lateral clavicular fractures and injuries to the AC joint can result in cosmetic deformity or eventually lead to the persistence of nuisance symptoms (eg, clicking, pain). Failure of the bone to unite after these injuries can also lead to progressive shoulder deformity, impaired function, and neurovascular compromise. Fractures of the coracoid process can be complications of AC joint injuries.

Sex

See Frequency, above.

Age

See Frequency, above.

Anatomy

The clavicle acts as a strut to support the upper extremity. It protects the subclavian neurovascular bundle and provides the neck with an acceptable cosmetic appearance. Although it lacks bony stability, the clavicle is firmly anchored at both ends by strong capsular ligamentous attachments, as well as by extra-articular ligaments that attach the clavicle to the first rib, sternum, and scapula.

The most medial portion of the clavicle lies anterior to the root of the internal jugular vessels and is near the trachea and esophagus. These structures are potential sites of concern with fractures of the medial aspect of the clavicle or with SC dislocations.

Epiphyseal growth plates develop at both the medial and lateral ends of the bone, but the medial ossification center is responsible for approximately 80% of the longitudinal growth of the bone. The medial ossification center radiographically appears around 15 years of age and does not fuse until approximately 25 years of age. This timing is critical to bear in mind because many medial clavicle fractures and SC injuries in young adults are actually physeal insults.

Unlike the SC joint, the AC joint derives meaningful stability from structures other than the joint capsule. The major stability of the AC joint comes from the trapezoid (anterior) and conoid (posterior) coracoclavicular ligaments. The AC and coracoacromial ligaments provide additional support. Muscular support includes the deltoid and trapezius muscles.

Clinical Details

The diagnosis of clavicular fractures and associated dislocations is usually straightforward and based on the mechanism of injury; the location of swelling and ecchymoses; and the findings of deformity, tenderness, and crepitus.

Patients report pain over the injured site and hold the affected extremity in adduction. With the most common site of injury, fractures to the middle third of the clavicle, the shoulder is typically slumped downward, forward, and inward. This is a result of the effect of gravity and the pull of the pectoralis major and latissimus dorsi on the distal fragment. The proximal fragment is often displaced superiorly because of the action of the sternocleidomastoid. The head is often tilted toward the injured side in an attempt to relax the effects of these displacing muscular forces.

Preferred Examination

The preferred method for radiographic evaluation of clavicle fractures varies according to the location of the injury and the need to identify potential associated injuries. In general, radiography is the only modality required, and fractures of the middle third of the clavicle are seen with an isolated anteroposterior (AP) projection centered on the midshaft of the clavicle. If clinical suspicion is high and if the AP view does not reveal a fracture, a 30° cephalic view can be helpful.

On the converse, radiographs are extremely difficult to interpret when injuries to the medial clavicle and the SC joint are being evaluated, even when both sides are included or oblique views are used. CT scanning is currently the best technique to evaluate these injuries. It provides true orthogonal views, which are unobtainable with plain radiography.

Finally, a single AP radiograph often suffices for diagnosing distal clavicular fractures and injuries to the AC joint. However, certain clinicians prefer to obtain comparison views of the opposite shoulder or stress images. Some believe that the value of stress, or weighted, images is controversial. Use of these images has essentially been abandoned in current practice. A specialized Zanca view may help to visualize the joint by eliminating overlying structures.

Limitations of Techniques

See the sections about imaging techniques below.

DIFFERENTIALS

Section 3 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Other Problems to be Considered

SC dislocation
AC dislocation

RADIOGRAPH

Section 4 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Findings

Mid clavicle

Evaluation of the clavicle requires a standard AP view centered on the midshaft of the clavicle. The image should be large enough to permit evaluation of both the AC joint and the SC joint, as well as the rest of the shoulder girdle and the upper lung fields.

Oblique views can be used to further gauge the degree and direction of displacement. In practice, an AP view with 20-60° cephalic tilt provides an adequate second view because interference with thoracic structures is minimized (see Image 6).

Because of the shape of the clavicle, these fractures represent multiplanar deformities, and accurate estimates of shortening are difficult to obtain with plain radiographs. CT scans, especially with 3-dimensional reconstructions, improve the accuracy. However, this level of accuracy is rarely required.

Medial clavicle and SC joint

Standard projections for the evaluation of the SC joint include posteroanterior (PA), lateral, and oblique views. Medial clavicular fractures and SC joint injuries may be difficult to appreciate on standard views because of the overlap of the clavicle with the sternum and the first rib. Special projections include Rockwood, Hobbs, Heinig, and Kattan views. The most popular additional view is the Rockwood, or Serendipity, view. This projection requires a 40° cephalic tilt of both SC joints centering on the manubrium (see Image 7).

The full extent of these injuries is often unclear despite the use of additional radiographic views. The diagnosis is best confirmed with CT scanning, which has the added benefit of the depiction of rib fractures, pulmonary contusion, and pneumothorax.

Of note, the secondary ossification center at the medial end of the clavicle does not appear before the age of 12 years, and it may not unite until the age of 25 years. Therefore, a physeal fracture can be confused with a dislocation of the SC joint on plain radiographs. This possibility should be carefully considered when studies in children or adolescents are being evaluated. (see CT SCAN, below.)

Lateral clavicle and AC joint

A single AP radiograph of the injured side often suffices, but some prefer to obtain comparison views of the opposite shoulder. AP views of the AC joint are performed at 15° of cephalic inclination, along the scapular spine. Normal alignment of the joint is present on an AP view when the joint space measures less than 5 mm wide and when the undersurfaces of the acromion and the distal clavicle form an uninterrupted arc.

Type 1 injuries consist of a minor tear in the AC ligament with an intact coracoclavicular ligament. This injury is clinically diagnosed when radiographs appear normal but tenderness is present over the joint.

Type 2 injuries represent a complete tear of the AC ligaments with partial tearing of the coracoclavicular ligament. The clavicle is superiorly displaced by less than half of its own width (see Image 8).

Type 3 injuries signify complete disruption of both the AC and coracoclavicular ligaments. Displacement greater than half of the width of the clavicle is present (see Image 9).

Radiographic findings are evident in 75% of type 1 and 2 AC injuries but in virtually 100% type 3 injuries.

Three additional categories have been introduced to help distinguish severe injuries for which surgical treatment may be warranted. Type 4 injuries are similar to type 3 injuries except that posterior displacement of the distal clavicle is also present. This can be verified on an axillary view. Type 5 injuries are characterized by inferior displacement of the scapula, with an increase  of the coracoclavicular interspace of 2-3 times normal. Such extreme displacement is usually associated with extensive stripping of the trapezius, pectoralis major and deltoid muscles. Type 6 injuries involve inferior displacement of the clavicle. This is a rare type of injury resulting from a direct downward blow.

In the past, stress radiographs were used to differentiate type 2 and 3 injuries (partial vs complete ligamentous tears). Because most surgeons now treat both type 2 and type 3 injuries nonsurgically, this distinction is no longer critical, and the use of stress views has fallen out of favor.

False Positives/Negatives

CT SCAN

Section 5 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Findings

Medial clavicle and SC joint

CT plays the greatest role in assessing medial clavicular fractures and injuries affecting the SC joint when plain images are not sufficient. CT scans should include the SC joints and at least half of both clavicles to allow for side-to-side comparison (see Image 10). If vascular compromise or impingement is a concern, the study can be performed with intravenous contrast enhancement.

CT scans can be acquired in a neutral position or with stress maneuvers, which increase their sensitivity. The stress maneuver requires that the ipsilateral humerus be internally rotated and brought medially across the chest by forcefully pulling against the opposite elbow.

Lateral clavicle and AC joint

CT scan is occasionally required to elucidate intra-articular fractures or stress fractures involving the AC joint. However, CT is limited in the evaluation of the surrounding soft tissues including the capsule, ligaments, and synovium.

MRI

Section 6 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Findings

Medial clavicle and SC joint

In most cases, the SC joint can be adequately evaluated with standard radiography or CT. However, MRI is superior to CT in depicting bone marrow abnormalities, disk or cartilaginous injury, and joint effusions. MRI is also better than other methods for evaluating extra-articular soft tissues. Furthermore, it lacks radiation exposure and directly provides multiplanar data rather than reformations. When vascular injury is a concern, magnetic resonance angiography (MRA) may be performed. Coronal, sagittal, axial, and oblique axial planes have been used in the MRI evaluation of the SC joint, depending on the specific area of concern.

Lateral clavicle and AC joint

MRI is occasionally required to elucidate intra-articular fractures or stress fractures involving the AC joint. MRI is now well established as an important modality in the assessment of rotator cuff disease.

ULTRASOUND

Section 7 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Findings

Clavicle

Katz et al examined 41 clavicular fractures in newborns by using both radiographic and ultrasonographic methods.¹ They found no substantial difference between the modalities. They suggested that ultrasonography is a sensitive diagnostic tool in the evaluation of clavicular fractures at birth and should be the procedure of choice in the diagnosis of neonatal clavicular fracture.

SC joint

The role of ultrasonography of the SC joint is limited. Sonography has been suggested as a screening tool to identify SC joint dislocation. In practice, it is used only if other modalities are not readily available. Ultrasonography can also be used for a quick assessment of vasculature with Doppler techniques. Finally, sonography has also been reported to be a useful intraoperative study to guide relocation of a dislocated joint.

AC joint

Recent research has focused on additional information obtained from ultrasonographic examination of the AC joint in suspected high-grade injuries. Conclusions are that ultrasonography provides additional information concerning the soft tissues and that it may be useful to delineate type 3 injuries.

INTERVENTION

Section 8 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Clavicle

Nondisplaced clavicular fractures can be treated with sling immobilization. Displaced clavicular fractures should be treated with sling immobilization, but surgical reduction may be required at a later date.

SC joint

Acute anterior dislocations can usually be treated nonsurgically with closed reduction, ice application, analgesia, and immobilization. Closed reduction for posterior dislocations may fail or may be associated with injury to the adjacent mediastinal structures. Patients with posterior SC joint dislocations frequently have associated injuries that take precedence over the dislocation. Treatment options for unreduced anterior or posterior dislocations may include open reduction with internal fixation (ORIF). The patient may need to accept some permanent instability.

AC joint

For type 1 and type 2 AC separations, treatment involves application of a sling for comfort, ice, and analgesic agents. Treatment of type 3 AC separation is controversial, but most cases are managed conservatively, as with type 2 injuries. For AC separation types 4 through 6, treatment is ORIF.

Medical/Legal Pitfalls

• Failure to diagnose fractures or dislocations
• Failure to recognize and treat associated injuries
• Failure to refer patients at risk for complications to orthopedist

Special Concerns

MULTIMEDIA

Section 9 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

Media file 1:  Type 1 clavicular fracture (middle third).
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Media file 2:  Type I comminuted clavicular fracture with skin tenting.
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Media type:  X-RAY

Media file 3:  Type 2 clavicular fracture (lateral third).
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Media type:  X-RAY

Media file 4:  Type 3 clavicular fracture (medial third).
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Media type:  X-RAY

Media file 5:  Anterior sternoclavicular (SC) dislocation.
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Media type:  Image

Media file 6:  Anteroposterior view with a cephalic tilt shows a mid-shaft clavicular fracture.
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Media type:  X-RAY

Media file 7:  Normal Rockwood (Serendipity) view of the sternoclavicular (SC) joint.
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Media type:  X-RAY

Media file 8:  Type 2 acromioclavicular (AC) dislocation.
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Media type:  X-RAY

Media file 9:  Type 3 acromioclavicular (AC) dislocation.
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Media type:  X-RAY

Media file 10:  Medial clavicle fracture without injury to the sternoclavicular (SC) joint.
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Media type:  CT

Media file 11:  Ultrasound of a clavicle fracture
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Media type:  Image

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Intervention
• Multimedia
• References

1. Katz R, Landman J, Dulitzky F, Bar-Ziv J. Fracture of the clavicle in the newborn. An ultrasound diagnosis. J Ultrasound Med. Jan 1988;7(1):21-3.
2. Browner BD, Jupiter JB. Skeletal Trauma: Basic Science, Management and Reconstruction. 3rd ed. Philadelphia, Pa: WB Saunders; 2003.
3. Burnstein MI, Pozniak MA. Computed tomography with stress maneuver to demonstrate sternoclavicular joint dislocation. J Comput Assist Tomogr. Jan-Feb 1990;14(1):159-60.
4. DeLee JC, Drez D. DeLee and Drez's Orthopaedic Sports Medicine. 2nd ed. Philadelphia, Pa: WB Saunders; 2003.
5. Ernberg LA, Potter HG. Radiographic evaluation of the acromioclavicular and sternoclavicular joints. Clin Sports Med. Apr 2003;22(2):255-75.
6. Grainger RG, Allison D, Dixon AK. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 4th ed. New York, NY: Churchill Livingstone; 2001.
7. Heers G, Hedtmann A. Correlation of ultrasonographic findings to Tossy's and Rockwood's classification of acromioclavicular joint injuries. Ultrasound Med Biol. Jun 2005;31(6):725-32.
8. Marx JA. Rosen's Emergency Medicine: Concepts and Clinical Practice. 5th ed. St Louis, Mo: Mosby; 2002.
9. Roberts JR, Hedges JR. Clinical Procedures in Emergency Medicine. 4th ed. Philadelphia, Pa: WB Saunders; 2004.

Article Last Updated: May 8, 2007