eMedicine Specialties > Radiology > Pediatrics

Elbow Trauma, Pediatric

Richard M Shore, MD, Associate Professor, Department of Radiology, Northwestern University Feinberg School of Medicine; Head, Division of General Radiology and Nuclear Medicine, Children's Memorial Hospital
John J Grayhack, MD, MS, Assistant Professor of Orthopedics, Northwestern University Medical School; Consulting Surgeon, Department of Surgery, Division of Orthopedic Surgery, Children's Memorial Hospital

Updated: Sep 10, 2008

Introduction

The evaluation of pediatric elbow radiographs in the setting of acute trauma is challenging for many radiologists. Diagnostic difficulties stem both from the complex developmental anatomy of the elbow and from significant differences between children and adults in the patterns of injury after elbow trauma.

Understanding the developmental anatomy of the pediatric elbow helps ensure that normal ossification centers are not misinterpreted as fracture fragments. It also helps the radiologist to recognize an injury when the pattern is altered. For example, the medial epicondyle is usually present before the ossification center for the trochlea appears. Therefore, when an ossicle is seen beneath the medial aspect of the distal humeral metaphysis and when the medial epicondyle is not seen in its expected location, the findings should be interpreted as demonstrating medial epicondyle avulsion with entrapment into the joint rather than a normal trochlea.

Knowledge of the expected patterns of injury aids in the recognition of subtle fractures because the radiologist knows what to look for in the bones and surrounding soft tissues. Understanding the mechanism of injury and the expected fracture pattern helps the radiologist supervising the examination to decide which additional views may be needed.^1,2,3

Anatomy

The elbow is composed of 3 articulations. The ulna articulates with the humerus at the trochlea, which is the grooved and rounded medial articular portion of the distal humerus. The articular portion of the ulna is formed by the olecranon process proximally and by the coronoid process more distally. This humeroulnar or trochleoulnar joint is a hinged articulation that essentially permits motion in a single plane, allowing flexion and extension. The concave head of the radius articulates with the capitellum, which is the convex lateral articular surface of the distal humerus. This humeroradial or radiocapitellar joint permits the radius to rotate to any degree of flexion or extension of the trochleoulnar joint; this rotation allows supination and pronation of the forearm. Rotation also depends on proper motion of the proximal radioulnar joint (the third articulation of the elbow) and on the normal mobility of the forearm and wrist.

The distal humeral articular surface has several grooves and ridges that are important in determining anatomic stability after a fracture. Medially, the trochlear notch articulates with a corresponding ridge along the ulna. More laterally, the capitellotrochlear sulcus separates the humeral articular surface of the radius from that of the ulna. Between these grooves is the lateral crista of the trochlea, which provides lateral stability to the trochleoulnar joint.

Developmental anatomy

Ossification of the elbow region is complex, but knowledge of it is essential in analyzing elbow trauma in children. The distal humerus has 4 secondary ossification centers: those for the capitellum and trochlea (which form the articular surfaces) and those for the medial and lateral epicondyles. The capitellar ossification center extends beyond the capitellum so that the lateral crista of the trochlea is ossified from the capitellar center. Typically, none of these centers are ossified at birth.

Invariably, the capitellum is the first secondary center to ossify, usually followed by the medial epicondyle, the trochlea, and the lateral epicondyle. The age at which ossification centers are first seen varies considerably; maturation usually proceeds earlier in girls than in boys. With this in mind, the average age at which the centers are seen first in 50% of children is 3 months of age for the capitellum, 5 years for the medial epicondyle, 8 years for the trochlea, and 10 years for the lateral epicondyle.

The corresponding ages at which the ossification centers of the proximal forearm bones appear are 4.5 years for the radial head and 9 years for the olecranon.⁴ The acronym CRMTOL is used to describe the usual order of appearance of all 6 elbow centers: capitellum, radial head, medial epicondyle, trochlea, olecranon, and lateral epicondyle. These ossification centers vary not only with regard to the age of the patient at the time of development but also with regard to their radiographic appearances.

The capitellum develops as a single smooth center, whereas trochlear ossification most often has a fragmented and irregular appearance. The medial epicondyle usually develops as a single center. The lateral epicondyle may arise as either a single elongated center or as multiple centers of ossification. The lateral epicondyle usually fuses to the distal humeral epiphysis (lateral condyle) before fusing to the metaphysis. Ossification of the lateral epicondyle begins peripherally and progresses toward the epiphysis and metaphysis. The radial head ossification center is initially oval; subsequently, it becomes flattened and disk shaped. The olecranon is often ossified from 2 secondary centers that should not be misinterpreted as fracture fragments (and vice versa).

Normal anatomic variants

In addition to the findings in the multiple ossification centers described above, other normal findings may simulate pathology. A notchlike defect in the proximal radial metaphysis may be confused with a fracture (see Image 1). The proximal radius has normal angulation between the neck and shaft; therefore, the neck is angulated laterally and slightly anteriorly relative to the shaft (see Image 1). This normal angulation must not be confused with a fracture, and the orientation of the neck rather than the shaft should be used to evaluate alignment of the radiocapitellar joint.

Normal radiographic findings that may simulate nontraumatic pathology include a radial tuberosity that appears as a lytic lesion when viewed en face (see Image 2) and the olecranon fossa of the distal humerus, which may be unusually large and lucent.

Radiographic Evaluation

Standard radiographic evaluation of the elbow includes imaging in the anteroposterior (AP) and lateral views. Other views may also be helpful. In a patient in whom a lateral condyle fracture is suspected, oblique views may show a subtle fracture line to better advantage. Because supracondylar fractures often are oriented obliquely (such that they course more proximally from anterior to posterior), an AP view with cephalad angulation of the x-ray beam may help to better demonstrate such a fracture. The radiocapitellar view is a lateral view with the beam angulated toward the patient's shoulder. This arrangement projects the capitellum and radiocapitellar joints away from the trochlea and coronoid processes, which overlap the capitellum and radiocapitellar joint on a standard lateral view, allowing better evaluation of the capitellum.

Evaluation of soft tissues and joint effusions

Evaluation of the soft tissues is important in elbow trauma. Localized soft tissue swelling over the lateral aspect of the elbow is a clue for which the radiologist should carefully search when assessing a possible lateral condyle fracture. Similarly, medial epicondyle avulsion fractures are often accompanied by localized soft tissue swelling in the medial aspect of the elbow.

Displacement of the elbow fat pads is an important indicator of an elbow joint effusion (see Image 3). The elbow fat pads are external to the synovium and are present within the fibrous external joint capsule, with the posterior fat pad located in the olecranon fossa and the anterior fat pad located in the coronoid fossa. When the elbow is flexed, the posterior fat pad lies within the olecranon fossa; it is usually not demonstrated on the lateral view. Hence, depiction of the posterior fat pad indicates outward displacement by a joint effusion. This evaluation is valid only when the elbow is flexed. With elbow extension, the olecranon process of the ulna moves into the olecranon fossa and displaces the posterior fat pad, which allows it to be depicted even without an effusion. Normally, the anterior fat pad may be seen just anterior to the distal humeral cortex; if the anterior fat pad is angled outward, it indicates an elbow effusion.

If no fracture is seen and if a posterior fat pad sign is present, the index of suspicion for an occult fracture is high. However, the fat pad sign is not invariably present in cases of fracture. It is estimated that the posterior fat pad sign is present in 30-70% of cases of occult fracture.

The presence of an elbow effusion alone does not indicate a fracture. In the setting of acute trauma, the presence of an elbow effusion strongly suggests a hemarthrosis resulting from a fracture. In other settings, the etiology may be different. Joint effusions resulting from septic arthritis or juvenile rheumatoid arthritis displace the fat pads, and patients with hemophilia often have an elbow hemarthrosis in the absence of fracture or trauma. In addition, other circumstances may involve a hemarthrosis without displacement of fat pads. If a fracture fragment disrupts a joint capsule, blood may escape from the joint, preventing joint distension and fat pad displacement. Marked edema may also obscure the fat pad, preventing recognition of the fat pad, even with displacement.

The implications of identifying an elbow joint effusion in the setting of acute trauma vary between children and adults. The identification of elbow joint effusions is more useful in children than in adults. In 70-90% of children, the presence of an effusion is associated with a fracture that is recognized either initially or on follow-up examinations. However, this percentage is not especially useful because, in most cases, the fracture is identified at the initial examination.

A more important question is related to the frequency of an occult fracture in patients with an elbow effusion (ie, when an effusion is present and when no fracture is seen on initial examination). In what percentage of patients is a fracture demonstrated later, either by recognizing demineralization at the fracture site or by recognizing the development of sclerosis or periosteal new bone formation during healing? Morewood estimated that the risk of occult fracture is approximately 30%,⁵ although subsequent studies have shown considerable variability; the incidence of healing fractures recognized on follow-up examinations of these patients ranges from 17%⁶ to 76%.⁷  

Another study evaluated the use of multidetector CT in the evaluation of children with posttraumatic elbow effusions.⁸  The investigators found that overall, in children with elbow effusions for whom no fracture was radiographically identifiable, multidetector CT demonstrated fractures in approximately 50% of the patients (48% for each of 2 observers individually and 52% by consensus). Hence, although the presence of a posttraumatic elbow effusion in children raises the possibility of an occult elbow fracture, it is not necessarily the case that a fracture is present.

The clinical decision as to which patients need to be treated for a presumed fracture is made on the basis of the examination results and knowledge of the associated risks. The absence of an effusion in children is strong evidence against an intra-articular fracture.⁹ Although a torn capsule or marked edema may produce a false-negative fat pad sign, the presence of a significant injury is usually obvious on radiographs. In adults, a joint effusion is usually associated with a fracture; however, a significant number of fractures are not associated with an identifiable effusion. Therefore, the lower negative predictability of this sign makes it less useful in adults than in children.

Evaluation using lines drawn on radiographs

Two lines may be drawn on radiographs to help in evaluating elbow trauma: the anterior humeral line and the radiocapitellar line (see Image 4). On a true lateral view of the elbow, a line drawn along the anterior aspect of the distal humeral metaphysis should pass through the middle third of the capitellum, which is also part of the humerus. This anterior humeral line indicates the relative positions of 2 parts of the same bone; therefore, acute malalignment is indicative of a fracture. Specifically, if the anterior humeral line passes either through the anterior third of the capitellum or anterior to the capitellum, it indicates that the capitellum is displaced posteriorly relative to the humeral metaphysis. This displacement most frequently results from a supracondylar fracture, although posterior displacement of the capitellum may also be seen in lateral condyle fractures.

Although this sign is useful in interpreting findings in most children, caution is needed in cases involving young children. When the capitellar ossification center is small, the findings may not indicate the true center of the capitellum, most of which is still cartilage. If an early ossification center is located slightly posterior in the capitellar cartilage, the anterior humeral line may pass anterior to the ossification center, though the capitellum is not truly displaced. The exact stage of development at which the capitellum is sufficiently ossified for this sign to be reliable is not well defined; however, for children in the age range for supracondylar fractures (3-10 y), the capitellum is sufficiently developed, and interpreting this finding is not a problem.

The radiocapitellar line is used to evaluate the relationship of the proximal radius to the capitellum. Because the radius usually bends in the region of the tuberosity, the line should be drawn through only the most proximal part of the radius rather than along a greater length of the diaphysis. The line should intersect the capitellum on all views, although in young children, the capitellar ossification center may occupy an eccentric position within the largely cartilaginous capitellum. The radiocapitellar line is used to compare the relative positions of 2 adjacent bones; hence, malalignment between them indicates dislocation.

Fracture Frequency

The frequency with which various elbow fractures occur differs between children and adults. In adults, 50% of elbow fractures involve the radial head and neck; 20% involve the olecranon. These fractures are relatively uncommon in children. Conversely, supracondylar fractures account for only 10% of adult elbow fractures, but they are the most common elbow fractures in children. In children, the most common elbow fractures are supracondylar (60%), lateral condylar (15%), and medial epicondylar (10%).¹⁰

Fractures of the Distal Humerus

Supracondylar fracture

Supracondylar fractures are the most common elbow fracture in children, accounting for 50-60% of cases. Most occur in children 3-10 years of age; the peak incidence occurs in those 5-8 years of age. The fracture is located below the humeral shaft in the metaphysis. In this region, the humerus flares out into medial and lateral columns that extend into the condyles. Between these columns, the humerus is relatively thin at the olecranon and coronoid fossae. This thinning is most pronounced during childhood; the trabeculae are less well developed in children than in adults. This difference likely accounts for the greater frequency of supracondylar fractures in children.^11,12,13,14

The vast majority of supracondylar fractures are extension injuries; such fractures result from a fall on an outstretched arm, with the proximal ulna transmitting force to the distal humerus. In children, relative ligamentous laxity allows the elbow to hyperextend; with hyperextension, the olecranon transmits the load into a bending force on the distal humerus in the supracondylar region. Most supracondylar fractures involve posterior displacement or angulation of the distal fragment. Often, medial displacement accompanies supracondylar fractures. With medial displacement, loss of support for the medial aspect of the distal fragment allows the distal fragment to rotate into varus alignment. The less common supracondylar fractures that occur with anterior displacement of the distal fragment are usually caused by a direct blow to the posterior aspect of the elbow such as that sustained with a fall onto the elbow.

Radiographic findings

Supracondylar fractures are diagnosed with the help of radiographic findings by use of both direct and indirect signs. The presence of a joint effusion does not specifically indicate that a fracture is present, but a joint effusion does signal that a fracture is likely; in such cases, a careful search is required. The anterior humeral line may be extremely useful in the diagnosis of supracondylar fracture; the line passes anterior to the middle third of the capitellum in 94% of cases. Images 5-6 demonstrate typical supracondylar fractures with abnormality of the anterior humeral line. Abnormality of the anterior humeral line indicates distal humeral deformity and, therefore, either an acute or previous fracture.

Supracondylar fractures may be complete or incomplete; the range of severity of such injuries is wide. The Gartland classification as modified by Wilkins defines extension supracondylar fractures as follows¹¹ :

• Type 1 — Fractures with no or minimal posterior displacement or angulation of the distal fragment such that the anterior humeral line still intersects part of the capitellum
• Type 2 — Fractures with more posterior displacement or angulation, but with an intact posterior cortex
• Type 3 — Fractures with displacement and complete cortical disruption (see Image 7)

With complete fractures, the fracture line and displacement are obvious. Even incomplete fractures often have enough disruption in 1 of the cortices (usually the anterior cortex) to make diagnosis easy (see Image 8). However, in approximately 25% of cases, the fracture may be subtle. These cases include greenstick and plastic bowing fractures. With greenstick fractures, cortical disruption is seen on the tensile side (usually the anterior cortex), and they may be accompanied by cortical buckling of the compression side (usually the posterior cortex). With plastic bowing, no discrete fracture line is present. Only deformity is observed, as demonstrated by the anterior humeral line. Subtle cortical deformity also may be present medially or laterally, and it may be associated with varus or valgus deformity.

In searching for subtle fractures, knowing their expected location is essential. On the frontal view, supracondylar fractures typically extend transversely through the metaphysis across the region of the olecranon fossa. With subtle fractures, the fracture line may be initially seen through only a portion of the metaphysis. With healing, sclerosis is demonstrated across the entire metaphysis, indicating the full extent of the fracture (see Image 9).

In the lateral projection, the fracture may be either transverse or oblique; typically, the fracture extends from anterior and distal to posterior and proximal. Orientation of the fracture line in the sagittal plane has both diagnostic and clinical implications. Diagnostically, oblique fractures may be demonstrated more easily by use of an AP view with cephalad angulation, which shows the fracture en face. Although not routinely acquired, this view may be useful when a fracture is highly suspected but is not found on standard views. Clinically, an oblique fracture is important because it causes rotation at the fracture site, resulting in a varus or valgus deformity.

Complications

The 2 major complications of supracondylar fractures in children are cubitus varus (see Image 10), which is relatively common, and vascular injury, which is uncommon but has a considerable morbidity rate when present.

Cubitus varus results primarily from alignment of the fracture at the time that it is set rather than from physeal injury with associated deformity from asymmetric growth. Because there is individual variation in the carrying angle, cubitus varus is best assessed by comparing the injured elbow with the elbow on the contralateral side. This analysis is aided by the use of the Baumann angle, which is the angle between the humeral shaft and the distal humerus, as defined by the growth plate between the capitellum and the metaphysis.

Although the physis in this region does not define the mechanical axis of the distal humerus, it serves as a well-defined marker that allows comparison of the orientation of the distal fragment to that of the contralateral elbow (see Image 11). Care must be taken to ensure a true AP view, because rotation leads to a change in the value of the Baumann angle. Although cubitus varus after supracondylar fractures is relatively common, in most instances, cubitus varus does not cause significant morbidity. In patients with more pronounced cubitus varus, corrective valgus osteotomy may be needed.

Vascular injury may be a severe complication of supracondylar fractures. With enough posterior displacement of the distal fragment, the brachial artery is subject to injury because it stretches across the fractured surface of the proximal fragment. Vascular insufficiency or swelling may lead to Volkmann ischemic contracture of the forearm, markedly limiting function of the extremity. Clinical assessment of vascular integrity at the time of presentation and after orthopedic manipulation as long as 48 hours later is the key to preventing Volkmann ischemic contracture. Plain radiographs are not useful in the evaluation of vascular injury. In some patients, arteriography, Doppler US, or CT angiography may be ordered to evaluate arterial flow and anatomy and to guide treatment, although the appropriateness of these studies is controversial.

Nerve injuries may complicate supracondylar fractures; they occur in approximately 5% of patients. These injuries most frequently involve the anterior interosseous branch of the median nerve.

Lateral condyle fracture

Fractures of the lateral condyle are the second most common elbow fracture in children, accounting for approximately 15% of cases. Lateral condyle fractures are seen most often in children 4-10 years of age. Many pediatricians and emergency physicians are not as familiar with these fractures as they are with supracondylar fractures, and some lateral condyle fractures may be subtle. As a result, the radiologist is helpful in diagnosing lateral condyle fractures and in alerting the clinical staff to the features of the fractures and the need for orthopedic treatment.

Lateral condyle fractures have 2 primary mechanisms of injury. With a fall on an outstretched arm with the elbow extended and the forearm abducted, the radius transmits an axial load on the capitellum, causing the lateral condyle to fracture. More frequently, the fractures are the result of traction force. The lateral condyle is the origin of the forearm extensor muscles; traction from these muscles may cause the lateral condyle to fracture when acute varus stress is applied to an extended elbow with the forearm supinated. In this position, the olecranon is locked in the olecranon fossa, with the trochlear ridge of the olecranon serving as the fulcrum of the varus stress. This mechanism accounts for the finding that the fracture line usually extends toward the trochlear groove of the distal humerus. It also accounts for the association of olecranon fractures with lateral condyle fractures.

Although in the past, there was controversy concerning the classification of lateral condyle fractures, these fractures are currently considered to be Salter-Harris type IV fractures. The fracture line usually begins in the lateral aspect of the metaphysis and extends medially through the metaphysis and crosses the physis into the epiphysis (see Image 12). In most patients, the fracture involves only the cartilaginous portion of the distal humeral epiphysis; therefore, the epiphyseal component of the fracture is not seen on radiographs. In 4 of 48 patients in whom the fracture line passed across the physis into the ossified portion of the capitellum, the radiographic appearances were those of a Salter-Harris type IV fracture (see Image 13).¹⁵

More importantly, the presence of adjacent fractured bone margins of the metaphysis and epiphysis raises the risk of bone bridging occurring from the metaphysis to the epiphysis during healing. This bridging may cause focal growth plate closure, a recognized complication of Salter-Harris type IV fractures. For most patients in whom the ossified capitellum is not involved, the risk of focal growth plate closure is relatively low; the risk is similar to that seen in Salter-Harris type II or III fractures.

The stability of the distal fragment is partly determined by whether the fracture extends all the way to the articular surface or whether a cartilaginous hinge remains intact to help prevent motion of the fracture fragment. In most patients in whom fracture extends to the articular surface, the fracture passes through the lateral portion of the trochlea so that the lateral crista of the trochlea is included in the fracture fragment, leading to instability of the trochleoulnar joint.

The Milch classification scheme for lateral condylar fractures defines type I fractures as those that pass through the ossified capitellum. These fractures enter the articular surface in the capitellotrochlear groove lateral to the lateral crista of the trochlea so that elbow stability is maintained.¹⁶ Milch type II fractures, the more common type, extend into the trochlea, leading to elbow joint instability.

A staging system for classifying the severity of lateral condyle fractures is as follows:

• Stage I fractures are incomplete, with an intact cartilaginous hinge that may have some angulation but no true displacement.
• Stage II fractures are complete and have only a small amount of displacement of the distal fragment.
• With stage III fractures, the distal fragment is significantly displaced, usually laterally and proximally, with instability of the elbow joint. In addition, traction from the common extensor muscles leads to rotation so that the cartilage-covered articular surface of the fractured lateral condyle is in contact with the metaphysis; this situation may result in malunion if not corrected.

Radiographic findings

The radiographic depiction of lateral condyle fractures depends on the degree of separation at the fracture site. If separation is significant, recognition of the fracture is easy (see Image 14), although distinguishing these fractures from supracondylar fractures depends on knowing the characteristic course. When no displacement is present, findings indicating a lateral condyle fracture may be subtle. A joint effusion helps in suggesting a subtle fracture; lateral soft tissue swelling localizes the region to be examined most carefully.

Although posteriorly displaced lateral condyle fractures may show an abnormal relationship between the anterior humeral line and the capitellum, this finding is not as useful in lateral condyle fractures as in supracondylar fractures. These fractures often demonstrate only a subtle subcortical fracture line along the lateral aspect of the metaphysis (see Image 15). Therefore, only a very thin sliver of bone may be viewed; this finding represents the distal fragment that is otherwise primarily cartilage.

Oblique views may be required to depict these fractures, because these fractures may not be apparent on AP views. In particular, the presence and extent of these fractures are often demonstrated to better advantage on the internal oblique view than the AP view; more displacement and evidence of instability are apparent on the internal oblique view.¹⁷  On lateral views, cortical disruption is usually seen posteriorly rather than anteriorly, as with supracondylar fractures (see Image 16).

Because several secondary ossification centers exist in the elbow, a small flake of bone adjacent to the metaphysis may be misinterpreted as a developmental center, such as the lateral epicondyle. However, because the lateral epicondyle is the last center in the elbow to ossify, most pediatric patients with lateral condyle fractures have elbows that are too immature to have a lateral epicondyle ossification center; therefore, the flake of bone must represent a fracture.

It may be tempting to regard such a subtle finding as being insufficient to represent a significant fracture; to recognize these fractures, it is important that one be familiar with them. However, the following caution should be noted with regard to subtle lateral condyle fractures: Partial overlap of the capitellum with the metaphysis may simulate a fracture when the lucency of the physis overlaps part of the metaphysis or when the double density of the capitellar and metaphyseal cortices simulates a fracture fragment.

Although a radiologic diagnosis of lateral condyle fracture depends on plain radiographic findings, MRI, arthrography, or ultrasonography (US) may be useful in the further evaluation of the fractures, particularly with regard to the course of the fracture through the cartilaginous epiphysis (see Image 17). Other injuries that may be confused with lateral condyle fractures include supracondylar fracture and, in young infants, separation of the distal humeral epiphysis (transcondylar fracture, Salter-Harris type I).

Complications

The major complications of lateral condyle fractures in children include instability (see Image 18), malunion, and nonunion (leading to varus deformity or, less often, to valgus deformity over time). In the series by Jakob et al involving 48 patients with lateral condyle fractures, 20 patients had fractures that were minimally displaced; 28 patients had significant displacement that required surgical reduction and fixation.¹⁵ Nonunion has been considered to be more of a problem in patients with minimally displaced fractures than in patients with significant displacement, presumably because the lack of surgical fixation allows a small amount of motion and because of the development of fibrocartilage between the fragments.¹⁸ Delayed complications of lateral condyle fractures include ulnar neuritis and posttraumatic arthritis.

As discussed above, with Milch II lateral condyle fractures, the fracture separates the lateral crista of the trochlea (lateral trochlear ridge) from the rest of the trochlea; this predisposes the patient to elbow dislocation through loss of lateral support for the olecranon process (see Images 40a-42c).

Lateral condyle fractures may be associated with other elbow fractures, particularly those involving the olecranon (see Image 19). However, they tend not to be associated with fractures remote from the elbow. Although lateral condyle fractures are associated with elbow dislocation, such dislocation is not a separate injury but rather is a direct result of the fracture, with loss of the stabilizing lateral crista, as discussed above.

Medial epicondyle fracture

Fractures of the medial epicondyle account for 10% of elbow fractures in children. They most often occur in children 7-15 years of age; the peak incidence occurs in children 11-12 years of age. Approximately one half of medial epicondyle fractures are associated with elbow dislocation or subluxation. Medial epicondyle fractures are avulsion injuries caused by traction from the ulnar collateral ligament or the forearm flexor muscles that arise from the medial epicondyle.

The major mechanisms of injury include acute valgus stress during a fall on an outstretched arm, posterior stress with acute elbow dislocation, and chronic muscular traction from the flexor and pronator muscles such as that caused by throwing (eg, Little League elbow).¹⁹ Acute valgus stress may cause a compression injury on the lateral side of the elbow or a traction injury on the medial side. In adults, this stress most frequently causes a compression fracture of the radial head or neck, whereas in children, avulsion of the medial epicondyle is more common.

Radiographic findings

Medial epicondyle avulsions may include separation of the entire medial epicondyle from the metaphysis, avulsion of only part of the medial epicondyle (see Image 20), or avulsion of the epicondyle together with a small portion of the adjacent metaphysis. These injuries resemble Salter-Harris type I, III, and II fractures, respectively, though the Salter-Harris classification is usually applied to injuries of the epiphyses rather than those of the apophyses.

Owing to traction from the forearm flexors, the medial epicondyle is displaced distally. Also, it is usually medially displaced from its anatomic position (see Image 21). Localized soft tissue swelling is usually present. In most patients, the medial epicondyle is extra-articular; therefore, a joint effusion is not present. In some patients, the medial epicondyle may be intra-articular; in others, widening of the physis for the medial epicondyle may be subtle. Comparison views of the contralateral elbow may be useful.

Complications

The fractured medial epicondyle may become entrapped in the elbow joint, representing a major complication. With acute valgus stress, the medial side of the elbow joint is opened. When the medial epicondyle is pulled downward (distally) by the forearm flexor muscles, it may enter the medial joint space. When the valgus force is removed, the medial epicondyle may then become entrapped as the medial joint space closes (see Image 22). Examples of entrapment of the medial epicondyle in a young child, before ossification of the trochlea occurs, and of entrapment in an older child, after trochlear ossification has occurred, are presented (see Images 41a-41b).

Entrapment is particularly common after an elbow dislocation or subluxation. It is important that such entrapment be recognized; the diagnosis may be made on the basis of radiographic findings. To make the diagnosis, it is helpful that the radiologist be familiar with the normal developmental anatomy of the elbow. Because the entrapped medial epicondyle is positioned beneath the medial side of the distal humeral metaphysis, it may be misinterpreted as the ossification center for the trochlea. However, the trochlea does not become ossified before the medial epicondyle. Therefore, the trochlea should not be seen unless the medial epicondyle is identified as well. In addition, usually, the trochlea initially appears as multiple fragmented ossification centers; by contrast, the medial epicondyle has a smooth and regular appearance.

Entrapment of the medial epicondyle may be difficult to detect on the frontal view; such entrapment is often better depicted on the lateral view. On the lateral view, a clue that is helpful in recognizing entrapment of the medial epicondyle is widening of the medial joint space. However, widening of the joint space may be difficult to evaluate in patients in whom the elbow is immature; in such cases, the largely cartilaginous trochlea makes the normal gap between the distal humerus and ulna appear quite wide.

In the radiographic evaluation of pediatric elbow trauma, it is important to assess the status of the medial epicondyle, particularly after an elbow dislocation. If the elbow is mature enough for ossification of the medial epicondyle to be expected, the position of the medial epicondyle should be verified. If the medial epicondyle is not seen in its normal anatomic position, it should be searched for elsewhere, including within the elbow joint.

Avulsion fractures of the medial epicondyle may occur before ossification, and they cannot be detected on plain radiographs. However, such an injury may be suggested by localized tenderness and soft tissue swelling and by the presence of a posterolateral elbow dislocation. Stress radiographs demonstrating widening of the medial joint space with valgus stress indicate either avulsion of the medial epicondyle or disruption of the ulnar collateral ligament. In children, the ligaments are generally stronger than the bone; therefore, avulsion fractures occur more frequently than ligamentous injury, as with medial epicondyle injuries. MRI is useful in identifying these fractures. Conventional, magnetic resonance, or CT arthrography may be helpful in searching for a cartilaginous entrapped medial epicondyle in patients in whom the medial epicondyle is intra-articular.

Medial condyle fracture

Fracture of the medial condyle is an uncommon injury in children. As with lateral condyle fractures, these are typically Salter-Harris type IV injuries. The fracture extends through the metaphysis and into the epiphysis, typically arising just above the medial epicondyle and extending to the trochlear groove (see Image 23).

In young patients with a nonossified or only partially ossified trochlea, the epiphyseal component of the fracture is not visible, and only the metaphyseal flake is identifiable. The medial epicondyle is included in the distal fragment. As with lateral condyle fractures, medial condyle fractures are often unstable and may be complicated by nonunion. Like lateral condyle fractures, medial condyle fractures may show marked rotation of the fracture fragment (see Images 42a-42c).  Although it is important to differentiate medial condyle fractures from medial epicondyle fractures, the distinction is not always easy to make with radiographs.

The presence of a metaphyseal flake fracture is not specific because some medial epicondyle avulsions extend into the metaphysis as a Salter-Harris type II fracture. In general, medial condyle fractures (Salter-Harris type IV injuries) have larger metaphyseal components than medial epicondyle fractures that involve the metaphysis have. Joint effusion is more likely to be present with medial condyle fractures, although joint effusions may be seen with medial epicondyle avulsion fractures. Clinical features that suggest a medial condyle fracture include instability and a limitation of elbow motion.

Transcondylar fracture

The term transcondylar fracture is used for fractures that separate the entire distal humeral epiphysis from the metaphysis. In most patients, these fractures occur entirely through the growth plate, resulting in a Salter-Harris type I fracture, although the fracture may extend into the metaphysis with a Salter-Harris type II injury. Transcondylar fractures most often occur in young children (<2 y); they are reportedly associated with birth injury and child abuse. The mechanism of injury is believed to be rotational shear.²⁰

In a transcondylar fracture, the epiphysis is usually medially displaced relative to the metaphysis (see Image 24). The proximal radius and ulna maintain a normal relationship with respect to the epiphysis; hence, the forearm bones are also displaced relative to the humeral metaphysis. In young children in whom the distal humeral epiphysis is not yet ossified, this malalignment of the forearm bones and the distal humeral metaphysis may be mistaken to indicate an elbow dislocation. Often, the capitellum has ossified; in such cases, it may serve as an important marker in the otherwise cartilaginous distal humeral epiphysis.

Demonstration of normal alignment between the proximal radius and the capitellum (radiocapitellar line) and normal alignment of the proximal radius and ulna with each other are the keys to differentiating transcondylar fracture from elbow dislocation. If the capitellum is not ossified and if it cannot be used to evaluate elbow alignment, medial displacement of the forearm bones relative to the distal humeral metaphysis should suggest a transcondylar fracture because the distal fragment is usually displaced medially. Conversely, in true elbow dislocations, the radius and ulna are dislocated either laterally and posteriorly (in children > 2 y) or primarily posteriorly (in children <2 y). MRI, US, or arthrography may be used to directly depict the relationship of the cartilaginous distal humeral epiphysis to the metaphysis (see Image 25).

Some transcondylar fractures include a small portion of the metaphysis; such a finding is helpful in recognizing that a fracture is present (see Image 26). However, this finding may cause the injury to be confused with a lateral condyle fracture. The distinction of the 2 fractures is important because lateral condyle fractures are often unstable and require operative fixation, which is frequently not necessary for transcondylar fractures because of the greater stability of the after reduction.

Features that help in distinguishing the 2 fractures include alignment of the radiocapitellar joint and the direction of displacement. In transcondylar fractures, radiocapitellar alignment remains normal, whereas in lateral condyle fractures, the distal fragment is often displaced or rotated, as described above, with alteration of the radiocapitellar alignment. Because the lateral crista of the trochlea is often included in the fracture fragment, the elbow joint loses lateral support in lateral condyle fractures. Lateral displacement of the proximal forearm bones results, rather than the medial displacement that typically seen in transcondylar fractures.

In most cases, patients with transcondylar fractures have a good prognosis, although diagnosis and treatment are precarious. In some patients, impaction of the epiphysis on the medial aspect of the metaphysis may cause growth plate injury, leading to subsequent varus deformity (see Image 27). It should be borne in mind that transcondylar fractures are associated with child abuse.

Other Elbow Injuries

Fractures of the proximal radius

Although the proximal radius is the most common site of elbow fracture in adults, it accounts for only 5% of elbow fractures in children. When proximal radial fractures occur in children, they primarily involve the radial neck. Fractures of the radial head epiphysis are uncommon in children.

Fractures of the proximal radius are usually caused by a compression force from a fall on an outstretched hand. The normal valgus at the elbow transforms this initial axial load into both axial and valgus stress. In adults, this stress often results in fractures of the radial head and neck; in children, valgus stress more often causes a distraction injury on the medial side of the joint. When valgus stress does cause a proximal radial fracture in children, the compression stress usually causes fractures through the metaphysis (radial neck) rather than the epiphysis (radial head), which is largely cartilaginous.

Radiographic findings

Most proximal radial fractures in children are either Salter-Harris type II injuries that extend through the growth plate and the lateral aspect of the metaphysis or metaphyseal fractures that extend across the neck near the growth plate but do not involve the growth plate directly. Rarely, a Salter-Harris type IV fracture extends vertically through the metaphysis and epiphysis, crossing the physis. With some proximal radial fractures, no displacement of the epiphysis occurs; detection of the fracture depends on the metaphyseal component, which may show only subtle abnormal angular deformity. This finding must be distinguished from the normal angulation that is usually present at the junction of the radial neck and shaft (see Image 28).

The radial head epiphysis may show displacement with varying amounts of shift and angulation that may lead to limitation of motion of the proximal radioulnar joint.²¹ Proximal radial fractures may result in abnormal articulation of the radial head and capitellum and therefore are fracture/dislocations. Displacement of the radial head may be marked, usually with the head displaced distally, and its articular surface may be rotated into the coronal plane posteriorly. However, the displacement may also be lateral (see Image 29). In these cases, the displacement may be the result of transient posterior elbow dislocation.

When the proximal radius and ulna are forced anteriorly and the dislocation is reduced, the capitellum may shear off the radial head, leaving it posteriorly displaced. During the reduction of these completely displaced fractures, the radial head may become inverted, so that the physeal fracture surface of the radial head articulates with the capitellum. Less often, as the proximal radius and ulna are dislocating posteriorly, the capitellum causes the radial neck to become fractured, and it may force the radial head anteriorly and distally.

Complications

A major complication of a radial neck fracture is limitation of motion at the proximal radioulnar joint, which mostly limits supination. This complication is usually caused by malalignment of the radial head and neck; more severe limitation of motion may result from radioulnar synostosis. Radial head displacement or injury to the proximal radial growth plate may cause growth arrest, leading to radial shortening that may affect the wrist joint. Proximal radial fractures in children are frequently associated with other injuries; such injuries most frequently involve the olecranon. The identification of a proximal radial fracture should alert the examiner to carefully search for other injuries.

Fractures of the proximal ulna

Fractures of the proximal ulna are uncommon in children, accounting for 6% of elbow fractures. In evaluating the proximal ulna in children, the normal olecranon apophysis must not be mistaken for a fracture fragment. The olecranon apophysis usually appears in children  approximately 10 years of age, and it fuses by 18 years of age. The normal apophysis may have separate ossifications centers near its tip.

The olecranon apophysis fuses in an anterior-to-posterior direction; radiographs may reveal a residual posterior cleftlike lucency with well-defined sclerotic margins. The characteristic location of the olecranon ossification centers, their smooth uninterrupted cortical margins, and the typical appearance of the partially fused physis help in distinguishing olecranon ossification from fractures at that site.

Most proximal ulnar fractures involve the olecranon process. The 3 major mechanisms of injury include direct impaction; distraction stress from the triceps muscles; and valgus or varus stress with the elbow in extension, which locks the olecranon into the distal humerus.

Radiographic findings

Distraction stress on the olecranon may occur from falling on an arm with the elbow partially flexed so that acute hyperflexion stress is applied against the triceps; alternatively, it may result from excessive muscular activity, often in association with throwing. The incidence of distraction fractures is particularly high in patients with osteogenesis imperfecta, including patients with relatively normal-appearing bones and few fractures elsewhere (see Image 30).

Distraction fractures of the olecranon may be subtle; alternatively, significant proximal displacement of the fracture fragment may be present. These fractures are usually Salter-Harris type II injuries that include a metaphyseal fragment of variable size. Salter-Harris type I fractures that pass entirely through the physis of the olecranon apophysis may occur, but they are relatively uncommon. The detection of these fractures requires a high index of suspicion and comparison with the noninjured elbow.

When the elbow is fully extended, the olecranon becomes locked into the olecranon fossa, making it susceptible to fracture by varus or valgus stress. These fractures may be subtle and have only a linear lucent line through the trabecular region (see Image 31). In other patients, the fracture is best seen at the proximal tip of the olecranon metaphysis (see Image 32).

Complications

Valgus stress fractures may be associated with a compression fracture of the radial neck or avulsion of the medial epicondyle. Varus stress fractures may be associated with a lateral condyle fracture (see Image 33) or a lateral dislocation of the radial head (type 3 Monteggia fracture/dislocation).

Olecranon fractures are often associated with other injuries; it is believed that the most common such injury found in association with olecranon fractures are proximal radial fractures, although several are associated with lateral condyle fractures.

Fractures of the coronoid process are infrequent in children, but they may be seen with posterior elbow dislocation.

Elbow dislocation

The elbow is the most frequently dislocated joint in children, whereas in adults, dislocations of the shoulder and interphalangeal joints of the fingers are more common. Elbow dislocation accounts for approximately 5% of elbow injuries in children. The mechanisms of dislocation include a fall on an outstretched arm with the elbow partially flexed and forced hyperextension, although both mechanisms more frequently result in fractures than in dislocations. The most common direction of displacement is posterior or posterolateral (see Images 34-35), although lateral and anterior dislocations also occur.

Dislocations often are associated with fractures, most often involving the medial epicondyle and coronoid process of the ulna. Other fractures that may be associated with elbow dislocations include fractures of the proximal radius, particularly fractures in which the radial head is markedly displaced and rotated into the coronal plane; fractures of the lateral condyle; and remote fractures in the same extremity, most often the distal radius and ulna. Detection of an elbow dislocation should alert the radiologist to carefully search for the other injuries.

Radiographic findings

Elbow dislocations are usually readily apparent on radiographs. In young patients, alignment of the radiocapitellar joint is evaluated by using the radiocapitellar line, whereas in the more mature skeleton, articulating surfaces of the radial head and capitellum are revealed directly. The articular relations of the medial condyle and proximal ulna are not as easy to evaluate in the immature skeleton.

After spontaneous reduction, prior elbow dislocation may be suggested by the identification of the fractures described above. In patients younger than 2 years, elbow dislocations are exceedingly rare, and transcondylar fractures (distal humeral epiphyseal separation) are often mistaken for elbow dislocation. Radiographic findings that indicate transcondylar fracture rather than dislocation include maintenance of normal radiocapitellar relations and medial displacement of the forearm bones.

Complications

Complications of elbow dislocation in children include associated fractures, neurologic injury (usually involving the ulnar nerve or the anterior interosseous branch of the median nerve), joint contracture, and heterotopic ossification in the regions of the disrupted medial or lateral collateral ligaments. Vascular complications are less common than neurologic injury and are usually accompanied by severe injuries, often including open fractures.²²

Monteggia fracture/dislocation

Monteggia fracture/dislocation involves dislocation of the radial head accompanied by fracture of the proximal or mid ulna, with the apex of the ulnar fracture pointing in the same direction as the radial head dislocation. Normal articulation of the medial condyle and proximal ulna is maintained. In 55-85% of patients, the radial head is anteriorly dislocated, with an associated apex anterior ulnar fracture (Monteggia type 1 injury). In the remainder of patients, fractures/dislocations are divided equally between posterior (Monteggia type 2 injury) and lateral (Monteggia type 3 injury) dislocation of the radial head. Lateral (Monteggia type 3) injuries most often occur in children 5-9 years of age (see Image 36).

Simplistically, a Monteggia fracture/dislocation may be thought of as the result of a force that dislocates the radial head and simultaneously fractures the ulna in the same direction. However, in most patients, the injury is caused by a fall onto a pronated forearm, which forces the arm into hyperpronation. This motion causes the ulna to fracture and contact the proximal radius, forcing the radial head to become dislocated from the capitellum.

In children, an ulnar fracture often is manifested by plastic bowing without a discrete fracture line (see Image 38). In some patients, the finding may be subtle; recognition of this injury requires a high index of suspicion and the use of comparison views of the contralateral forearm, when needed. Most cases of isolated radial head dislocation in children are likely to actually be Monteggia fracture/dislocation with a subtle ulnar bowing fracture. Conversely, ulnar fractures in a child are often accompanied by a radial fracture or dislocation, even if the ulnar fracture is a relatively subtle greenstick injury. If an associated radial fracture is not identified, a careful search should be made for a radiocapitellar dislocation or subluxation. The elbow should be well visualized in all patients who have an ulnar injury, with or without an associated radial fracture.

A Monteggia variant has fractures of the radius and ulna. The radial fracture is so close to the joint that the injury may superficially resemble a radial head dislocation. In these cases, only the radial head is still in alignment with the capitellum. The rest of the radius appears dislocated with respect to the capitellum; however, this is a displaced fracture rather than a dislocation (see Image 37). In cases in which the radial head is not yet ossified, this injury cannot be distinguished from a true Monteggia fracture/dislocation by use of plain radiographs.

A similar situation occurs in the wrist in children; that is, a fracture through the distal ulnar physis may occur in association with a distal radial diaphyseal fracture and result in a pseudo-Galeazzi injury (see Image 39). In fact, Monteggia variant and pseudo-Galeazzi injuries are forearm fractures involving both bones, with 1 of the fractures occurring so close to the joint that a dislocation is erroneously suggested.

Pulled elbow

A pulled elbow is a distraction injury. It is also called nursemaid's elbow and other names; it usually results from a sudden pull on the hand. In children younger than 5 years, the annular ligament is relatively loose, allowing the radial head to be pulled through it when acute traction is suddenly placed on a pronated forearm (which is the usual position of the forearm when a child is being pulled along by an adult). Although the annular ligament becomes transiently interposed between the radial head and capitellum, this movement does not cause recognizable widening of the radiocapitellar joint. Therefore, elbow radiographic findings are normal in a pulled elbow. MRIs should demonstrate the abnormal relationship of the radial head and annular ligament, but such studies are seldom needed.

Summary

Radiographic evaluation of acute elbow trauma in children may be difficult because of the multiple ossification centers that appear in this region. However, acute elbow trauma provides an excellent example of how an understanding of the developmental anatomy of the region, in conjunction with knowledge of the mechanism of injury and the most frequent fracture patterns and associations, may greatly aid in the radiographic analysis.

See the eMedicine article Salter-Harris Fractures for more information. For excellent patient education resources, visit eMedicine's Breaks, Fractures, and Dislocations Center. Also, see eMedicine's patient education articles Broken Elbow and Elbow Dislocation. For additional reading, see the articles by Barton et al and Skaggs et al.^23,24

Multimedia

Media file 1: Normal notch. Two examples of the normal notchlike step off of proximal radial metaphysis in patients of different ages. A, The normal angulation between the radial neck and shaft. B, More mature elbow.

Media file 2: Normal radial tuberosity. A, On the lateral view, the radial tuberosity is seen en face and appears as a lytic defect. B, On the frontal view, radial tuberosity is clearly recognizable. This view demonstrates the normal angulation between the radial neck and shaft.

Media file 3: Fat pad signs indicate an elbow joint effusion. Lateral view shows the posterior fat pad, which is always abnormal when seen with the elbow positioned in right-angle flexion. The anterior fat pad is demonstrated and is abnormally elevated. Although the anterior fat pad may be seen without an effusion, it should not be elevated to this degree.

Media file 4: Normal lines. Lateral view shows the 2 lines used for radiographic analysis in patients with elbow trauma. The solid anterior humeral line is drawn along the anterior cortex of the distal humeral metaphysis and should pass through the middle third of the capitellum. Passage of the anterior humeral line either anterior to the capitellum or through the anterior third of the capitellum demonstrates that the capitellum is positioned too far posteriorly; this finding indicates a distal humeral fracture. The dashed radiocapitellar line is drawn through the radial neck and should pass through the capitellum. This relation should be examined on a frontal view as well. Failure of the radiocapitellar line to pass through the capitellum indicates radiocapitellar dislocation.

Media file 5: Typical supracondylar fracture. Fracture is obvious on both the anteroposterior (A) and lateral (B) views. Lateral view demonstrates an abnormal relation of the capitellum to the anterior humeral line, which passes along the anterior margin of the capitellum. Compare these images with the lateral view of the contralateral elbow (C), which shows the anterior humeral line passing normally through the middle third of the capitellum.

Media file 6: Typical supracondylar fracture. Anteroposterior (A) and lateral (B) views. Note the abnormal relation of anterior humeral line and the lateral view.

Media file 7: Supracondylar fracture. Anteroposterior (A) and lateral (B) views show significant medial and posterior displacement of a distal fragment.

Media file 8: Supracondylar fracture. Anteroposterior view shows disruption of the medial cortex.

Media file 9: Supracondylar fracture. Initial lateral view (A) shows an abnormal anterior humeral line indicative of a fracture. On the initial anteroposterior view (B), the fracture is subtle and is seen only medially. Follow-up anteroposterior (C) and lateral (D) views demonstrate the fracture better. On the anteroposterior view in C, the fracture may clearly be seen to extend all of the way across the metaphysis.

Media file 10: Supracondylar fracture. Cubitus varus. A, Anteroposterior view shows a varus deformity of the distal humerus from a previous well-healed supracondylar fracture. B, On the lateral view, the capitellum remains posteriorly positioned, a finding typical of a previous supracondylar fracture.

Media file 11: Baumann angle. A 5-year-old boy with previous left distal humeral supracondylar fracture. A, Anteroposterior view of the left elbow. B, Comparison anteroposterior view of right elbow. The Baumann angle usually is defined as the angle between the growth plate for the capitellum and a line drawn perpendicular to the humeral shaft. Rather than drawing the extra perpendicular line, the Baumann angle was measured as 90° minus the angle between the capitellar growth plate and the humeral shaft. In this patient, the uninjured right elbow has a Baumann angle of 12°, and the previously injured left elbow has a Baumann angle of only 2°. This finding indicates a varus deformity of the left distal humerus.

Media file 12: Lateral condyle fracture. Initial anteroposterior (A) and lateral (B) views show a nondisplaced lateral condyle fracture. A subsequent anteroposterior view (C) shows lateral displacement of a distal fragment. An anteroposterior tomogram (D) obtained at that time shows both the displacement and the course of the fracture line through the epiphysis to the articular surface of the trochlea. Most patients with lateral condyle fractures are young, and the epiphyseal extension of the fracture is within the growth cartilage and thus not identifiable on plain radiographs.

Media file 13: Lateral condyle fracture passing through the ossified portion of the capitellum. Anteroposterior view shows the lateral condyle with a fracture line passing through the metaphysis and capitellum, crossing the growth plate.

Media file 14: Displaced lateral condyle fracture. Anteroposterior view shows an obvious lateral condyle fracture with lateral displacement of the fragment, rotation, and downward displacement caused by muscular traction.

Media file 15: Subtle lateral condyle fracture. Anteroposterior (A) and lateral (B) views. In this patient, the only sign of the fracture is the thin metaphyseal flake on the anteroposterior view.

Media file 16: Lateral condyle fracture. Anteroposterior (A) and lateral (B) views. On the lateral view, cortical disruption is usually seen posteriorly rather than anteriorly as in supracondylar fractures.

Media file 17: Fat-suppressed T2-weighted coronal MRI shows that the fracture extends through the metaphysis into the epiphysis, although the articular surface remains intact.

Media file 18: Lateral condyle fracture with instability. Initial anteroposterior (A) and lateral (B) views show a nondisplaced lateral condyle fracture. Subsequent views (C and D) show posterior displacement of a distal fragment.

Media file 19: Lateral condyle and olecranon fractures. Anteroposterior (A) and lateral (B) views show combined fractures of the distal humeral lateral condyle and olecranon process of the ulna.

Media file 20: Medial epicondyle avulsion fracture in an 11-year-old girl with an avulsion of part of the left medial epicondyle (A). Compare the simultaneous view of the uninjured right elbow (B) and a previous view of the left elbow obtained when the patient was 10 years of age (C).

Media file 21: Medial epicondyle fracture with distal displacement of a fracture fragment. Anteroposterior views of the injured left elbow (A) compared with the uninjured right elbow (B).

Media file 22: Medial epicondyle fracture with entrapment in an 8-year-old boy. Anteroposterior (A) and lateral (B) views of the injured right elbow compared with anteroposterior (C) and lateral (D) views of the uninjured left elbow. Note the normal position of the medial epicondyle in left elbow, which is not seen in the right elbow.

Media file 23: Medial condyle fracture. Anteroposterior (A) and lateral (B) views. Vertically oriented fracture begins along the medial aspect of the distal humeral metaphysis and extends to the growth plate. Similar to lateral condyle fractures, the fracture continues through the epiphysis, but it cannot be seen in this patient because the entire trochlea is still cartilage and has not yet become ossified.

Media file 24: Transcondylar fracture. Anteroposterior (A) and lateral (B) views of the injured left elbow with anteroposterior (C) and lateral (D) views of the right elbow for comparison. The capitellum (along with the remainder of the cartilaginous epiphysis) is medially and posteriorly displaced relative to the metaphysis. Radiocapitellar alignment remains normal.

Media file 25: Transcondylar fracture. Anteroposterior (A) and lateral (B) views. The position of the tiny ossification center for the capitellum suggests that it is displaced posteriorly; this is confirmed on the arthrogram (C).

Media file 26: Transcondylar fracture. Anteroposterior (A) and lateral (B) views. Transcondylar fracture with typical posterior and medial displacement of the distal fragment. On the lateral view, a thin metaphyseal flake is present posteriorly and indicates a Salter-Harris type II injury rather than the usual Salter-Harris type I injury.

Media file 27: Transcondylar fracture. A, Initial anteroposterior view shows typical medial displacement of the capitellum and forearm bones. B, Subsequent radiograph shows abnormality of the medial condyle and varus deformity from a growth plate injury.

Media file 28: Radial neck fracture. Anteroposterior view shows a mildly abnormal angular configuration of the lateral aspect of the proximal radial metaphysis. This finding is indicative of a nondisplaced fracture.

Media file 29: Displaced proximal radial fracture. Anteroposterior view shows a Salter-Harris type II fracture of the proximal radius with lateral and distal displacement of the radial head, which is positioned along the lateral aspect of the proximal radial metaphysis.

Media file 30: Olecranon avulsion fracture. Lateral view in a patient with osteogenesis imperfecta who has had bilateral recurrent fractures in the same region. The lucent cleft in the fracture fragment is the normal olecranon growth plate. The avulsed fracture fragment is proximally retracted by the triceps muscle.

Media file 31: Olecranon fracture. A, On the anteroposterior view, the fracture is seen as a longitudinal lucent line through the medial aspect of the proximal ulna. B, On the lateral view, a small fracture line is present at the tip of the proximal ulna, and subtle discontinuity of the posterior cortex is seen.

Media file 32: Subtle olecranon fracture. Anteroposterior (A) and lateral (B) views. Fracture is at the tip of the ossified portion of the olecranon process.

Media file 33: Combined lateral condyle and olecranon fractures. Initial anteroposterior (A) and lateral (B) views show an obvious lateral condyle fracture and a relatively subtle olecranon fracture. On an anteroposterior view obtained after reduction of the lateral condyle fracture (C), the olecranon fracture is more obvious.

Media file 34: Posterolateral elbow dislocation. A, Note the avulsion of the medial epicondyle, which projects just distal to the trochlea on the anteroposterior view. B, Lateral view.

Media file 35: Posterolateral elbow dislocation, lateral view. In addition to the elbow dislocation, avulsion of the medial epicondyle is noted projecting posterior to the capitellum. Note the small fragment of metaphysis attached to the medial epicondyle; this finding indicates a Salter-Harris type II injury.

Media file 36: In a Monteggia fracture type 3, the radial head is dislocated, primarily laterally and slightly anteriorly. A, Anteroposterior view. B, The ulnar fracture has apex lateral angulation and is well aligned on the lateral view.

Media file 37: Monteggia variant. Anteroposterior (A) and lateral (B) views. An ulna fracture with apex anterior angulation is present. Apparent anterior dislocation of the proximal radius, as seen on the lateral view, is actually a proximal radial fracture with anterior displacement of the neck and shaft relative to the poorly visualized radial head that still articulates normally with the capitellum.

Media file 38: Monteggia fracture type I. Lateral view of injured forearm (A) shows anterior dislocation of the radial head and convex anterior bowing of the ulna, which is most apparent when compared with the contralateral uninjured forearm (B).

Media file 39: Pseudo-Galeazzi fracture. Anteroposterior (A) and lateral (B) views. A radial fracture with apex anterior angulation is present. Anterior displacement of most of the distal ulna relative to the wrist is due to a distal ulnar growth plate fracture, with anterior displacement of the metaphysis relative to the epiphysis, which still articulates normally with the wrist. The distal ulnar epiphysis is best depicted on the anteroposterior view, on which it is seen to overlap the ulnar metaphysis. On the lateral view, the distal ulnar epiphysis is largely obscured by the distal radius. The smooth end of the ulna is the metaphysis ending at the physeal fracture.

Media file 40a: Milch II lateral condyle fracture with elbow dislocation, frontal (A) and lateral (B) views. The distal fracture fragment is displaced laterally and posteriorly. Displacement of the lateral trochlear ridge has also resulted in elbow joint instability with dislocation of the olecranon laterally and posteriorly. Radiocapitellar alignment remains normal.

Media file 40b: Milch II lateral condyle fracture with elbow dislocation, frontal (A) and lateral (B) views. The distal fracture fragment is displaced laterally and posteriorly. Displacement of the lateral trochlear ridge has also resulted in elbow joint instability with dislocation of the olecranon laterally and posteriorly. Radiocapitellar alignment remains normal.

Media file 41a: Medial epicondyle avulsion fracture with entrapment in an older patient. A, AP view. B, AP contralateral comparison. Note the presence of the normal trochlear ossification center in this patient which was not present in the younger patient. In B, the entraped medial epicondyle is distal to the trochlea and is absent from its normal position. In B, note the normal position of the medial epicondyle along the medial aspect of the distal humeral metaphysis.

Media file 41b: Medial epicondyle avulsion fracture with entrapment in an older patient. A, AP view. B, AP contralateral comparison. Note the presence of the normal trochlear ossification center in this patient which was not present in the younger patient. In A, the entraped medial epicondyle is distal to the trochlea and is absent from its normal position. In B, note the normal position of the medial epicondyle along the medial aspect of the distal humeral metaphysis.

Media file 42a: Medial condyle fracture with markedly rotated distal fragment in a 7-year-old boy. AP view (A), oblique view (B), and lateral view (C) show markedly rotated distal fracture fragment of this medial condyle fracture. Note associated proximal radial metaphyseal fracture

Media file 42b: Medial condyle fracture with markedly rotated distal fragment, 7 year old boy. AP (A), oblique (B), and lateral (C) views show markedly rotated distal fracture fragment of this medial condyle fracture. Note associated proximal radial metaphyseal fracture

Media file 42c: Medial condyle fracture with markedly rotated distal fragment, 7 year old boy. AP (A), oblique (B), and lateral (C) views show markedly rotated distal fracture fragment of this medial condyle fracture. Note associated proximal radial metaphyseal fracture

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Keywords

elbow trauma, elbow fractures in children, pediatric elbow injury, pediatric elbow fracture, pediatric elbow dislocation, pediatric elbow trauma, elbow dislocation, supracondylar fracture, lateral condyle fracture, medial epicondyle fracture, medial condyle fracture, transcondylar fracture, proximal radius fracture, proximal ulna fracture, Monteggia fracture, Monteggia's fracture, Monteggia dislocation, Monteggia's dislocation, pulled elbow, olecranon fracture

Contributor Information and Disclosures

Author

Richard M Shore, MD, Associate Professor, Department of Radiology, Northwestern University Feinberg School of Medicine; Head, Division of General Radiology and Nuclear Medicine, Children's Memorial Hospital
Richard M Shore, MD is a member of the following medical societies: International Skeletal Society, Society for Pediatric Radiology, and Society of Nuclear Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

John J Grayhack, MD, MS, Assistant Professor of Orthopedics, Northwestern University Medical School; Consulting Surgeon, Department of Surgery, Division of Orthopedic Surgery, Children's Memorial Hospital
John J Grayhack, MD, MS is a member of the following medical societies: American Academy of Orthopaedic Surgeons
Disclosure: Nothing to disclose.

Medical Editor

Fredric A Hoffer, MD, FAAP, FSIR, Professor of Radiology, University of Washington; Section Chief of Interventional Radiology, Department of Radiology, Seattle Children's Hospital and Regional Medical Center
Fredric A Hoffer, MD, FAAP, FSIR is a member of the following medical societies: American Academy of Pediatrics, Children's Oncology Group, Radiological Society of North America, Society for Pediatric Radiology, and Society of Interventional Radiology
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington
Felix S Chew, MD, MBA, EdM is a member of the following medical societies: American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

Evidence-based care guideline for loss of elbow motion following surgery or trauma in children aged 4 to 18. Cincinnati Children's Hospital Medical Center.  2007 Dec.  9 pages.  NGC:006291

Elbow (acute & chronic).
Work Loss Data Institute.  2003 (revised 2007 Jun 11).  158 pages. [NGC Update Pending] NGC:005797

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