I N D I C AT I O N S
Plain extremity radiographs are indicated in pediatric patients with significant mechanism of injury; pain; limitation of use or motion; or physical exam evidence of deformity, swelling, or tenderness. The joint above and below the site of injury should be carefully examined, and radiographs of adjacent joints should be obtained when indicated. Occasionally, parental pressure to exclude fractures is a contributing factor in determining the need for extremity radiographs.
D IAG N O S T I C C A PA B I L I T I E S
Pediatric extremities consist of growing bones and ossifications centers, with wide variability in normal-appearing bones based on age. Despite these variations, a basic understanding of bone development physiology and time of onset of certain radiogra- phic findings, particularly ossification centers of the elbow, is important in order to accurately interpret these films. Physeal injuries, which involve the growth plate, comprise up to one- third of all pediatric fractures. Because the physis itself is radi- olucent, physeal fractures are not always evident on initial plain radiographs. Follow-up plain radiographs and, occasionally,
Figure 7.1. Physeal fractures: Salter-Harris classification. Physeal fractures occur at the physis, or growth plate. Approximately 18% to 30% of all pediatric fractures involve the physis. Physeal injuries are more common in adolescents than in younger children, with the peak incidence at 11 to 12 years of age. Most occur in the upper limb, particularly in the radius and ulna. Physeal fractures can be categorized from types 1 to 5 based on the Salter-Harris classification.
imaging with magnetic resonance or nuclear bone scan may be necessary.
Minimum views of the extremity should include anteropos- terior (AP) and lateral. Ensure that a true lateral of the elbow is obtained because fat pads may be obscured or distorted with any sort of rotated technique. Oblique views may be needed to define a fracture, particularly of the elbow or ankle. Comparison views with the contralateral extremity may be useful to deter- mine normal variants, but they should not be ordered routinely on all patients.
I MAG I N G P I T FA L L S / L I M I TAT I O N S
Negative initial plain radiographs do not exclude a Salter-Harris type 1 physeal fracture. If a pediatric patient has negative films but significant swelling or point tenderness along the physis of a bone, assume a physeal fracture and splint accordingly. Also, resist the pitfall of diagnosing sprains in children with nega- tive radiographs because ligaments tend to be stronger than the developing bones to which they are attached at the epiphyseal and perichondrial areas. The incidence of sprains and disloca- tions are much less common in children than in adults.
C L I N I C A L I MAG E S
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Figure 7.2. Salter-Harris type 1. This fracture involves separation of the metaphysis and epiphysis at the physis. It is suspected on clinical grounds if there is point tenderness or swelling at the physis. Radiographs are usually normal, but they may reveal some widening of the physis or mild displacement of the epiphysis. Note on the left image that the epiphysis appears slightly displaced dorsally and on the middle image that the epiphysis appears slightly displaced laterally. Follow-up radiographs at 1 to 2 weeks may reveal new bone formation at the physis.
Figure 7.3. Salter-Harris type 2. This fracture involves the physis and metaphysis. It is the most common physeal fracture (75%) and carries a good prognosis.
Figure 7.4. Salter-Harris type 3. Fracture through the physis and epiphysis, and intraarticular by def- inition. This can lead to growth arrest or chronic disability. ED orthopedic consultation is warranted.
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Figure 7.5. Salter-Harris type 4. Fracture through physis, metaphysis, and epiphysis, and intraartic- ular by definition. Same complications and management as type 3.
Figure 7.6. Salter-Harris type 5. Crush injury due to significant axial compression. This may appear obvious with distortion or marked narrowing of the physis, or may be subtle and radiographically similar to a type 1 fracture. Note the narrowed tibial physis and concurrent calcaneal fracture in these images. If the mechanism is suggestive, consider a type 5 fracture. Comparison views may be needed. Courtesy of Loren Yamamoto, MD.
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Figure 7.7A and B. Torus fracture. Also called a buckle fracture, this injury is common in younger children. It occurs in the meta- physeal region of bone from a compressive load. The cortex of bone “buckles” in a small area, resulting in a stable fracture pat- tern. The most common site of this fracture is the distal radius. The fracture area may be seen on one side only or bilaterally. If a distal forearm torus fracture is unilateral and minor, a short arm splint is often adequate; if bilateral or more significant, use a sugar tong splint to immobilize the elbow joint as well.
Figure 7.8. Greenstick fracture. A Greenstick fracture is an incomplete fracture that usually occurs at the diaphyseal-metaphyseal junction. Angulation of a bone causes a break on the convex side, while the periosteum and cortex on the concave side remains intact. To obtain an anatomical reduction, this fracture must often first be completed. Courtesy of Loren Yamamoto, MD.
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Figure 7.9A and B. Normal elbow ossification centers. The elbow is a common fracture site in a child, usually resulting from a fall onto an out- stretched arm. Unfortunately, pediatric elbow radiographs appear intimidating due to the mul- tiple ossification centers and various temporal– spatial relationships that need to be considered. In actuality, interpreting pediatric elbow x-rays is relatively straightforward if a simple, system- atic approach is followed. Courtesy of Loren Yamamoto, MD.
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Figure 7.10A and B. The normal ossification centers of the right elbow. They can be remembered using the mnemonic CRITOE, which stands for Capitellum, Radial head, Internal (medial) epicondyle, Trochlea, Olecra- non, and External (lateral) epicondyle. These ossification centers all appear at different ages and eventually fuse to adjacent bones. The ages at which they appear are highly variable, with the general guideline being 2, 4, 6, 8, 10, and 12 years of age for CRITOE, respectively. Although the ages at which they appear are variable in each child, it is critical to remember that these ossification centers always appear in a specific sequence, with only rare exceptions. Given this reasoning, if three bony fragments are seen, they should be the capitellum, radial head, and internal epicondyle. If the external epicondyle ossification center is seen but not the olecranon ossification center, what appears to be the external epicondyle ossification center is in actuality a fracture fragment. Also note that a true and reliable lateral of the elbow should give alignment and superimposition of the epicondyles, giving an “hourglass” or “figure of 8” sign as highlighted in (B). If this hourglass sign is not seen, it may not be a true lateral and may be obscuring important fat pads or fracture lines. Looking at the lateral view, identify the anterior fat pad, which is a somewhat triangular-shaped dark lucency just anterior to the anterior border of the distal humerus. This is a normal anterior fat pad sign. If the elbow joint capsule becomes distended due to hemarthrosis from a fracture in the elbow joint space, that anterior fat pad will be displaced anterior and superiorly to form a more prominent lucency, or “sail sign.” So a small anterior fat pad is considered normal, but a large one is considered abnormal and indicates an elbow fracture. A posterior fat pad located posterior to the distal humerus is normally not seen due to the deep olecranon fossa, but if a posterior fat pad of any size is seen, it is considered abnormal. Thus, a large anterior fat pad or a posterior fat pad of any size is considered abnormal, and an elbow fracture should be presumed, even if an obvious fracture is not seen.
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Figure 7.11. Anterior humeral and radiocapitellar lines. The anterior humeral line is an imaginary line along the long anterior axis of the humerus on the lateral view. This line should bisect the capitellum in the middle third. If the line intersects the anterior third of the capitel- lum or passes completely anterior, this most likely indicates a supra- condylar fracture with posterior displacement. The radiocapitellar line is an imaginary line through the longitudinal central axis of the radius. This line should pass through the capitellum in both the AP and lateral views. If it does not, it most likely indicates a dislocation, usually of the radial head.
Figure 7.12. Supracondylar fracture. Note the cortical break in the pos- terior supracondylar area with the large associated posterior fat pad. Also note that the anterior humeral line is abnormal and crosses the anterior third of the capitellum, indicating mild posterior displacement of the fracture.
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Figure 7.13A and B. Supracondylar fracture, occult. The only abnormality seen here is a posterior fat pad, indicating hemarthrosis and a presumed occult supracondylar fracture. In the pediatric population, supracondylar fractures are the most common type of elbow fracture, accounting for more than 50% of fractures of the elbow this age group, whereas radial head fractures are more common in adults. Typical mechanism is a fall on the outstretched arm with hyperextension. Occasionally, distal pulses may be absent; most cases are due to vasospasm or arterial compression, which should resolve after reducing the fracture. It is extremely important to document neurovascular functioning of the distal arm with elbow fractures. Complications most commonly involve the brachial artery and median nerve, which may lead to Volkman’s ischemic contracture if not properly managed. All supracondylar fractures warrant orthopedic consults in the ED for careful immobilization and close follow-up.
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Figure 7.14. Supracondylar fracture, complete displacement. This is an exam- ple of a type 3 or completely displaced fracture.
Figure 7.15. Supracondylar fracture with radius fracture. The obvious fracture is the transverse radius fracture. The sub- tle fracture is the associated occult supracondylar fracture, as indicated by the posterior fat pad sign.
Figures 7.16 (below left) and 7.17 (below right). Monteggia’s fractures. These two radiographs are examples of Monteggia’s fracture, which is a com- bination of a proximal ulnar fracture and radial head dislocation. Notice the radiocapitellar line, which does not pass through the capitellum, thus revealing the dislocation. Monteggia’s fractures comprise 2% of all elbow fractures in children. The usual mech- anism is elbow hyperextension. If the radial head dislocation is not recog- nized early and properly reduced, it could lead to permanent radial nerve damage and limited elbow motion. Needless to say, emergent orthopedic consultation is required. Most of these fractures can be closed reduced, but some will require open reduction and fixation.
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Figure 7.18A and B. Galeazzi’s fracture. The obvious fracture is the comminuted radial fracture, but the more subtle injury is the dislocation of the distal ulna, seen clearly on the lateral view. This is an example of Galeazzi’s fracture, which is classically described as fracture of the distal third of the radius with dislocation of the distal ulna. This fracture should be suspected with any angulated fracture of the radius. Like Monteggia’s injuries, most of these fractures can be closed reduced.
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Figure 7.19A and B. Lateral epicondyle fracture. Note the fracture fragment off the lateral condyle, seen best on the AP view. This is not a normal ossification center because the lateral (external) epicondyle is the last ossification center to become visible. In this patient, no other ossification centers are visible, not even the capitellum, which should be the first ossification center to be seen.
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Figure 7.20. Lateral epicondyle fracture. A: Another example of a lateral epicondyle fracture. Note the extra fracture fragment (arrow) inferior to the normal lateral epicondyle ossification center. In this patient, all ossification centers are visible. B: Comparison view of the other normal elbow of the same patient.
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Figure 7.21A and B. Elbow dislocation with epicondylar fracture. This typical posterior elbow dislocation occurred in a child who fell onto his outstretched arm. Also note the small fracture fragments off both the lateral and medial epicondyles, confirming a distal humeral epicondylar fracture.
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Figure 7.22A and B. Radial head subluxation (nursemaid’s elbow) Note that the radiocapitellar line does not go through the capitellum in all views. This patient was being swung around playfully by dad with the arms extended. The annular ligament becomes partially detached from the head of the radius and slips into the radiohumeral joint, where it is entrapped. This injury usually occurs in children a few months to 5 years of age, after which the strength of the annular ligament is such that the injury is uncommon. The usual mechanism is axial traction on an extended and pronated arm, such as when a child is lifted up or twirled around by the arms. The child usually holds the affected arm in pronation with the elbow slightly flexed. Mild tenderness may be noted with palpation of the radial head. Significant point tenderness or swelling should suggest an alternative diagnosis, such as a fracture. Radiographs are not needed unless a fracture is suspected, and certainly, closed reduction should not be attempted without films unless a fracture can comfortably be excluded on historical and clinical grounds alone. Closed reduction is attempted with your thumb on the radial head area and a combination of supination and flexion of the elbow. Frequently, you will feel a palpable “click.” If supination/flexion does not appear to work, you can try rapid hyperpronation and extension. When reduction is successful, the child typically uses the arm normally within 5 to 10 min. Postreduction radiographs are not needed unless arm use continues to be limited.
Figure 7.23. Lateral epicondylar fracture with radial head subluxation. The radiocapitellar line appears abnormal in both views. In addition, there is an avulsion fracture of lateral epicondyle. This radiograph was first interpreted as a normal lateral epicondylar ossification center, but on closer review, it is clear that the ossification centers of the radial head, medial (internal) epicondyle, trochlea, and olecranon are not yet visible radiographically (remember CRITOE); thus, the lateral epicondyle should also not be present. The only normal ossification center visible on this radiograph is the capitellum.
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Figure 7.24. Ossification sequence variant. There are rare exceptions to every rule. This radiograph is an example of the medial epicondyle ossification center becoming visible prior to the radial head ossification center. This was confirmed by a comparison view of the other elbow. There is no fracture on this film.
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Figure 7.25A and B. Toddler’s fracture. First described by Dunbar in 1964, this fracture is classically described as an oblique or spiral nondisplaced fracture of the distal tibia. It is most commonly seen in children 9 months to 3 years of age, and occurs as a result of an axial loading and twisting injury on a fixed foot, which would maximize forces in the distal leg. Although any oblique or spiral fracture of a long bone in a child should raise the possibility of nonaccidental trauma, an oblique fracture of the distal tibia in a weight-bearing infant can be explained from normal accidental forces, such as a fall, which is frequently unwitnessed. More concerning would be a spiral fracture of the mid or proximal tibia, which may more likely suggest nonaccidental trauma, as a perpetrator holding and twisting the distal portion of a leg would maximize forces in the midshaft and proximal areas of the tibia. Isolated spiral fractures of the tibia neither confirm nor dismiss the possibility of abuse.
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Figure 7.26. Osgood-Schlatter disease. This adolescent devel- oped acute knee pain while playing basketball and demonstrates an avulsion fracture and Osgood-Schlatter disease. Note the avul- sion fracture of the tibial tuberosity. Osgood-Schlatter disease is inflammation or apophysitis of ossification centers (apophyses), mainly in the proximal tibia at the insertion of the patellar ten- don. Repetitive stress due to strong muscular attachments to these apophyses can lead to microfractures, avulsions, or com- plete patellar tendon ruptures. Most are minor injuries and can be treated conservatively with symptomatic care and activity restriction.
Figure 7.27. Hip avulsion fracture. This injury occurred in a teenage track sprinter while running and without direct trauma. Note the fracture off the superior iliac crest where the sartorius muscle inserts. These hip avulsion fractures occur in active ado- lescents due to jumping, running, or kicking. The most common sites of these avulsions are the superior iliac crest (insertion of the sartorius), inferior iliac crest (insertion of the rectus femoris), and ischial tuberosity (insertion of hamstring muscles). Many of these injuries are preceded by microfractures at these insertion sites, similar to Osgood-Schlatter disease. Most of these injuries can be treated conservatively and rarely require surgery. Cour- tesy of Loren Yamamoto, MD.
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Figure 7.28. Slipped capital femoral epiphysis (SCFE). The lines demonstrate a Klein’s line, which is a linear line drawn along the supe- rior border of the proximal femoral metaphysis. This line should inter- sect the top part of the femoral epiphysis, which it does on the right hip. However, it does not pass through the epiphysis on the left hip, which is indicative of SCFE. This injury can present with chronic or acute pain in the hip, thigh, or knee, and up to 25% are bilateral. Most occur in older children and younger adolescents, which helps differen- tiate this disease from Legg-Calve-Perthes disease, which has a similar presentation but tends to occur in younger children. A frog leg view should always be including in any patient with suspected SCFE.
Figure 7.29 Septic arthritis of the hip. This toddler presented with refusal to walk and left hip pain. Note the widened joint space of the left hip compared with the right, indicating joint effusion and, in this case, pus. Hip aspiration grew out Staphylococcus aureus in this patient. If hip radiographs are equivocal, other imaging modalities such as ultrasound, MRI, or bone scan are indicated.