Imaging of Elbow Fractures and Dislocations in Adults 

Preferred examination

It has been suggested that radiologic imaging studies may be unnecessary for the evaluation of elbow fractures and dislocations if the active range of motion of the elbow remains normal^{[1, 2]} ; even the ability to fully extend the elbow while in a supine position may be sufficient to obviate radiography.^{[3, 4]} In such cases, patients may be advised to return in 7-10 days if their symptoms do not resolve.^[3]

The preferred study for the evaluation of elbow trauma is conventional radiography (see the images below).^[5] Radiographic examination requires the acquisition of 2 views: anteroposterior (AP) view in full extension and lateral view in 90° flexion. In children, oblique projections may be useful if the frontal and lateral projections do not show a fracture and fat pad signs are evident; internal oblique views are also valuable for providing further evaluation of lateral condylar fractures of the humerus in children.^[6]

Plain radiography is limited by the range of movement in an injured extremity, the patient's compliance, and the technique and ability of the technologist. The author recommends the careful removal of any splints prior to imaging to enable depiction of the greatest amount of radiographic detail.

On radiographs, an anterior humeral line (see the image below) is parallel to the anterior cortex of the humerus. This line should intersect the distal, middle third of the capitellum. Displacement of this line suggests the presence of subtle supracondylar fractures.

The radiocapitellar line (see Image above) extends through the axis of the radial head and neck. This line should intersect the midcapitellum on all radiographic views.

Displacement of the anterior fat pad, the radiographic sail sign (see the image below), may be present. The anterior fat pad is normally visualized on lateral radiographs as a triangular radiolucency. In the presence of joint effusion, this fat pad is displaced anteriorly, and the anterior margin becomes convex, similar to a billowing spinnaker sail. The presence of the sail sign should prompt further investigation for fractures. Fat pad signs may not be evident if the fracture is extracapsular.

Posterior fat pad displacement may be observed. The posterior fat pad is not normally seen on radiographs, and its presence is always an abnormal finding that mandates further investigation for fractures.

When a fracture of the radial head, coronoid process, or capitellum is suspected, a radial head–capitellar view should be obtained. This view is a variant of the lateral projection that magnifies the structures and eliminates the overlap of joint surfaces. The view is obtained by positioning the patient with his or her forearm resting on the ulnar side, with the elbow flexed 90° and thumb pointing upward. The beam is pointed at the radial head with a 45° angle to the forearm.

Although the elbow is one of the most stable joints in the body, elbow dislocations and fractures are common. In adults, elbow dislocations are second only to shoulder dislocations in frequency; the elbow is the most frequently dislocated joint in pediatric patients.^[7]

Elbow dislocations are classified as either simple or complex. Simple dislocations are classified by the direction of radial and/or ulnar displacement in relation to the distal part of the humerus. Complex elbow dislocations involve related fractures and/or neurovascular injuries.

Elbow fractures are classified as distal humeral, radial, and ulnar. The frequency of the different fracture types varies with the mechanism of injury and the age of the patient. In adults, radial head fracture is the most common type.

Pearls

The following pearls should help to limit the number of missed cases:

• On plain radiographs, look for the presence of the fat pad sign; a posterior fat pad sign is always an abnormal finding, and underlying bony or ligamentous injury should be investigated
• The radial head–capitellar view is a useful adjunct in assessing fractures in the posterior half of the radial head, coronoid process, and capitellum
• Look for associated fractures on postreduction radiographs of elbow dislocations; missed coronoid process fractures may lead to recurrent subluxation or dislocation
• In each case of an ulnar fracture, look for associated radial head dislocations (ie, Monteggia fracture-dislocations); conversely, in cases of radial dislocations, look for an associated ulnar fracture
• A painful posttraumatic elbow with negative plain radiographic findings warrants conservative treatment; follow-up radiographs, including repeat radial head–capitellar views, should be obtained in 7-10 days

For patient education information, see the Breaks, Fractures, and Dislocations Center, as well as Elbow Dislocation and Broken Elbow.

Elbow dislocations

Adult elbow dislocations are classified by the direction of displacement and the presence or absence of associated fractures. Simple elbow dislocations are solely soft tissue injuries. The direction can be anterior, posterior, lateral, or divergent. The most common dislocation involves posterior displacement of both the radius and ulna in relation to the distal humerus. Less common dislocations are the following: medial and lateral dislocations, anterior dislocations, translocation of the elbow, divergent dislocations, and isolated dislocations of either the radius or ulna.

Complex elbow dislocations have associated fractures that compromise joint stability. The most common associated fractures are those of the radial head and coronoid process. The combination of posterior elbow dislocation, radial head fracture, and coronoid fracture has been termed the "terrible triad".^[8] Associated injuries involving structures other than the elbow (eg, the shoulder, distal radius or ulna, and carpal bones) occur in 10-15% of cases.^[9]

The Essex-Lopresti fracture-dislocation consists of a comminuted radial head fracture and a distal radioulnar joint dislocation, along with tearing of the interosseus membrane; it typically results from high-energy trauma.^[10]

Monteggia fracture-dislocations involve ulnar fracture accompanied by dislocation of the radial head. Table 1 summarizes the Bado classification system for Monteggia fracture-dislocations.

Table 1. Bado Classification of Monteggia Fracture-Dislocation^[11] (Open Table in a new window)

Most dislocations occur as a result of a fall on an outstretched hand (FOOSH). Elbow dislocations and fractures can also occur with a high-energy direct impact.

AP and lateral radiographs of the elbow are most effective in demonstrating elbow dislocations. Postreduction films should be examined for associated fractures. Radiographic findings include displacement of the radius and/or ulna relative to the distal humerus, with or without evident fracture lines.

Elbow fractures

Elbow fractures are classified into 3 categories: (1) distal humerus fractures, (2) proximal radius fractures, and (3) proximal ulna fractures.

Table 2. Muller Classification of Distal Humerus Fractures (Open Table in a new window)

Supracondylar fractures

Supracondylar fractures are the most common elbow fractures in pediatric patients (see the image below). Typically, patients are 3-10 years old. In the immature skeleton, the collateral ligaments and joint capsule are stronger than the bone. The opposite is true in the mature skeleton. Therefore, supracondylar fractures seldom occur in adults. Two types of supracondylar fractures are possible: flexion fractures and extension fractures. These types are subdivided into categories on the basis of displacement and cortical integrity. Also, because the immature elbow has developing physes, Salter-Harris fractures may occur.

Salter-Harris type I supracondylar fractures occur most frequently in infants and toddlers. The Salter-Harris type I fracture affects only the physis, with separation of the epiphysis from the metaphysis. These fractures are minimally displaced or nondisplaced. Radiographic findings are subtle and include the presence of a posterior fat pad due to hemarthrosis or perhaps a widening of the physis.

Elbow dislocations may be mistaken for Salter-Harris type I supracondylar fractures. Correct distinction is important because an improperly treated dislocation can lead to chronic joint dysfunction. In a physeal separation, the relationship of the capitellum to the humerus is disrupted while that of the capitellum to the radial head remains normal. In an elbow dislocation, the alignment between the radial head and capitellar epiphysis is lost. Further cross-sectional imaging may be necessary to delineate the injury.

True supracondylar fractures may result from trauma during extension (eg, FOOSH with the elbow in full extension) or flexion (eg, direct impact to a flexed elbow). The preferred studies are AP and lateral radiographs, with CT as needed to assess the position of comminuted fragments. Radiographic findings include a fracture line proximal to the humeral epicondyles, joint effusion (eg, fat pad sign), and disruption of the anterior humeral line. Treatment for a nondisplaced fracture is immobilization. Patients with a displaced fracture should be referred to an orthopedist.

Transcondylar fractures

Transcondylar fractures are classified into flexion and extension types on the basis of the position of the elbow during impact. The mechanism of injury is a FOOSH. The preferred studies are AP and lateral radiographs and CT to assess the position of comminuted fragments. On the images, the fracture line extends through the condyles proximal to the articular surface. Treatment is difficult, because the amount of bone available for proper union is limited; the patient should be referred to an orthopedist.

Intercondylar fractures

These are T- or Y-shaped fractures with varying amounts of displacement between the condyles and from the humerus. The mechanism of injury is indirect trauma: the olecranon is forced against the articular surface of the humerus and splits the end of the humerus. The preferred studies are AP and lateral radiographs; CT can be used to guide surgical intervention. On the images, a fracture is present between condyles, and the condyles are separated from the humeral shaft. Treatment is open reduction and internal fixation (ORIF).

Condylar fractures

These fractures are divided into medial and lateral condylar fractures. Lateral condyle fractures are more common. The mechanism of injury with lateral fractures is direct impact to the lateral elbow during flexion; medial fractures involve an impact to the olecranon process with a flexed elbow. The preferred study is plain radiography; CT is used as needed. Radiographic findings include a widened intercondylar distance with lateral fractures; commonly, a fragment is posteriorly and inferiorly displaced. With medial fractures, the fragment is commonly anteriorly and inferiorly displaced. Fractures typically involve the joint surface and nonarticular parts of the distal humerus. Treatment for nondisplaced fractures is immobilization. Fractures that are displaced by more than 3 mm require surgical fixation.

Capitellar fractures

A capitellar fracture is one that involves the articular surface of the distal humerus. Most commonly, these occur with posterior elbow dislocations. The mechanism of injury is a FOOSH in which the radial head shears the capitellum. The preferred study is lateral elbow radiography. On radiographs, the fragment is medial relative to the normal position, with visible joint effusion. The treatment of nondisplaced fractures is immobilization.

Displaced fractures require surgical treatment.^[12] In a prospective, randomized study by McKee et al of elderly patients with displaced, intra-articular distal humeral fractures, total elbow arthroplasty (TEA) was found in many instances to provide superior results compared with open reduction and internal fixation (ORIF). Of 21 patients randomized to ORIF, 5 needed to be converted to TEA because of unstable fixation. Operative time was 32 minutes less for the TEA group. Mayo Elbow Performance Scores (MEPSs) were significantly better for TEA patients at 3 months, 6 months, 12 months, and 2 years. TEA patients also had better DASH (Disabilities of the Arm, Shoulder, and Hand) scores at 6 weeks and 6 months, but not at 1 year or at 2 years follow-up. TEA patients had a mean flexion-extension arc of 107º; ORIF patients, 95º. TEA may therefore be preferred for elderly patients with complex distal humeral fractures.^[13]

Olecranon fractures

The many classifications of olecranon fractures are based on the displacement, the number of fracture lines, and the subdivisions of the olecranon process. No classification system is universally accepted. The mechanism of injury is a direct impact or FOOSH. The preferred study is lateral radiography. Radiographs demonstrate the fracture and amount of displacement. Displaced fractures are defined by a separation of more than 2 mm or increased separation with elbow flexion. On radiographs, a fracture line is evident through the olecranon process. The treatment for nondisplaced fractures is immobilization. Displaced fractures require ORIF.

Mason fractures

Mason fractures are radial head fractures; they are classified into 4 types, as shown in Table 3.

Table 3. Mason Classification of Fractures (Open Table in a new window)

The mechanism of injury is a FOOSH that forces the radial head against the capitellum. The preferred study is lateral radiography of the anterior aspect of the radial head and the radial head and capitellum to evaluate the posterior aspect of the radial head or occult fractures. Radiographic findings vary from comminution to marginal fractures involving impaction, depression, or angulation. Nondisplaced fractures may result in only a posterior fat pad or the anterior sail sign.

The treatment of type I and type II fractures is joint aspiration followed by immobilization. Radial head osteoplasty may be required in fractures that fail to heal. Type III fractures and type II fractures with a mechanical block are treated with radial head revision. Type IV fractures are first treated for dislocation and then for the fracture, according to its Mason classification. Other indications for ORIF include cleavage fractures of the articular surface involving one third of the head or 3- to 4-mm displacement involving half of the radial head. (See the images below.)

Degree of confidence

Plain radiographs can be limited by patient positioning, patient compliance, and technique. The sail sign and posterior fat pad should always raise suspicion if fractures are not evident; in patients with these findings, the authors recommend conservative treatment and repeat plain radiography in 7-10 days. Cross-sectional imaging should be reserved for surgical planning in the acute setting and for later evaluation of associated soft tissue involvement.

CT is selectively used in acute or subacute settings to evaluate the displacement of fractures or to delineate osteochondral fragments in the joint.

If thin-section multidetector-row CT is complemented with multiplanar reconstructions, the degree of confidence in the findings is high.

MRI has a limited role in the acute setting. In the subacute setting, MRI is invaluable in the assessment of the collateral ligaments; common extensor and flexor tendon originations; articular cartilage; and, to a lesser extent, occult fractures. MRI and MRI arthrography are superior to CT arthrography for detecting occult bone injuries in the elbow.^[14] MRI can detect the osteochondral and ligamentous injuries that often accompany acute radial head fractures (Mason type II and III).

MRI may be used to assess the status of the interosseus membrane when a longitudinal radioulnar dissociation is suspected. Also, MRI can be used to visualize major neurovascular structures that cross the joint.

As peripheral magnetic resonance angiography (MRA) is more widely used, it may come to have a role in the assessment of acute vascular injury in the elbow.

Arteriography is rarely indicated in the absence of definite signs of arterial injury (eg, pulsatile hemorrhage, absent distal pulses, overt distal ischemia, audible bruit, and a palpable thrill). Arteriography is primarily used to assess the brachial artery at the elbow. Transection, thrombosis, dissection, and intimal flaps may be found.