Musculoskeletal




▪ Normal Variants and Common Benign Entities


Probably more than in any other organ system, the normal imaging appearance of the skeletal system is strikingly different in children from its appearance in adults ( Fig. 7-1 ). This is related to the changing appearance of growing and maturing bone. The most striking changes occur near the physes and apophyses. Many of the more common mistakes made in pediatric skeletal radiology are related to the misinterpretation of normal structures as being abnormal. Textbooks such as Keats’s Atlas of Normal Roentgen Variants That May Simulate Disease are dedicated to the normal radiographic appearances and variations of bones in children. The details of all of the normal changes in the radiographic appearance throughout the maturing skeleton cannot be covered here. The following section describes several commonly misinterpreted normal variants and benign entities.




▪ FIGURE 7-1


Changes in Radiographic Appearance of Bony Structures with Age.

Radiographs of the pelvis are shown in different patients. A, At 6 months of age; B, at 2 years of age; C, at 6 years of age; D, at 10 years of age; and E, at 15 years of age. Note the dramatic changes in the appearance of the pelvis as structures ossify over time. At 6 months of age (in A ), the femoral heads are just starting to ossify. The triradiate cartilage is open, and large portions of the ischium are not yet ossified. As children age, the femoral heads ( black arrowhead on right femoral head) become more ossified, the ischium and pubis (white arrow) fuse, and the triradiate cartilage (white arrowhead) closes. As the ischiopubic synchondrosis ( black arrows in C and D ) closes, it can mimic a healing fracture to the untrained eye. The final portion of the pelvis to ossify is the iliac crest apophysis (in E , white arrow ). This starts fusing only after the triradiate cartilage is closed.


Apophyseal and Epiphyseal Irregularity


The terms apophysis and epiphysis sound similar and have similar meanings. Their differences can be confusing. The term epiphysis refers to the part of bone that articulate with the adjacent bone. The primary growth plate, or physis, of the epiphysis is typically perpendicular to the longitudinal axis of the bone. Apophyses do not have an articular surface. The physis of an apophysis often courses parallel to the long axis of the bone. Apophyses act as a site of attachment for tendons.


In the growing child, apophyses and epiphyses in various parts of the body can have variable and often somewhat irregular appearances. Separate ossicles of an apophysis can mimic fragments, irregularity can mimic periosteal reaction, and mixed sclerosis and lucency can be confused with findings of an inflammatory or neoplastic process. Common apophyses that may have this appearance include tibial tuberosity, ischeal tuberosity, ischeal pubic synchondrosis, posterior calcaneal apophysis ( Fig. 7-2 ), and medial malleolus of the ankle ( Fig. 7-3 ). Irregularity and fragmentation are commonly seen in the normal tibial tuberosity. The calcaneal apophysis can often demonstrate a strikingly sclerotic appearance (see Fig. 7-2, C ). The ischeal pubic synchondrosis can appear very prominent (see Fig. 7-1, D ) and asymmetric.




▪ FIGURE 7-2


Examples of Apophyseal Irregularity in the Calcaneus in Four Separate Children Showing the Wide Variation in Normal.

A, The calcaneal apophysis (arrow) is just beginning to ossify in this 6-year-old male. B, Both the metaphyseal and apophyseal edges of the calcaneus are irregular in this 9-year-old female. C, The calcaneal apophysis is mostly ossified in this 10-year-old male. In some children, as in this one, the normal calcaneal apophysis is sclerotic and mildly fragmented.



▪ FIGURE 7-3


Apophyseal Irregularity in the Medial Malleolus of the Distal Tibia.

Mortise view of the ankle in a 10-year-old male shows an irregular ossification center of the medial malleolus (arrow) . Fragmentation of the medial malleolus is almost always a part of normal development. The absence of soft tissue swelling helps to confirm that this is not related to trauma. Although there can be fragmentation of the medial malleolus, there should not be fragmentation of the distal fibula. When present, as in this case, it is related to trauma.


Epiphyses can also appear irregular and even fragmented. The most common epiphyses with this irregular appearance are the distal femoral epiphysis ( Fig. 7-4 ) and the capitellum ( Fig. 7-5 ). It is important to recognize these irregularities as a normal stage of development and not confuse them with osteochondral lesions (in the distal femoral epiphysis or the capitellum) or with fracture (medial malleolus).




▪ FIGURE 7-4


Epiphyseal Irregularity of the Distal Femur.

AP ( A ) and lateral ( B ) views of the knee in a 2-year-old female show developmental irregularity of the distal femoral epiphysis (arrows) . As children age, the irregularity may become more focal and can mimic an osteochondral lesion.



▪ FIGURE 7-5


Epiphyseal Irregularity of the Capitellum.

AP ( A ) and lateral ( B ) views of the elbow in a 3-year-old male show developmental irregularity of the capitellum (arrow) . The lack of soft tissue swelling and a joint effusion help to confirm that no fracture is present. Follow-up radiographs (not shown) confirmed that the findings were developmental and not related to trauma.


Distal Femoral Metaphyseal Irregularity


Distal femoral metaphyseal irregularity, also referred to as cortical desmoid or cortical irregularity syndrome, refers to the presence of irregular cortical margination and associated lucency involving the posteromedial aspect of the distal femoral metaphysis. It occurs in as many as 11% of boys aged 10 to 15 years. Although debated, its presence is thought to be related to chronic avulsion at the insertion of the adductor magnus muscle. Although this lesion can be associated with pain, it is often discovered incidentally, and its significance lies in its alarming radiographic appearance. On radiography there is cortical irregularity present along the posteromedial cortex of the distal femoral metaphysis, best seen on the lateral view ( Fig. 7-6 ). On frontal radiographs there may be an associated lucency (see Fig. 7-6, B ). Familiarity with the typical location, appearance, and patient age is important so that these lesions are not confused with aggressive malignancies. Because the lesions are often bilateral, confirmation of their benign nature can be made by demonstrating a similar lesion on radiographs of the opposite knee. In problematic cases, computed tomography (CT) or magnetic resonance imaging (MRI) can be used to demonstrate the characteristic findings: a characteristic scooplike defect with an irregular but intact cortex; no associated soft tissue mass; and a subtle contralateral lesion.




▪ FIGURE 7-6


Distal Femoral Metaphyseal Irregularity.

A, Lateral radiograph of the knee in a 14-year-old male shows irregularity (arrow) of the posterior aspect of the distal femoral metaphysis. Irregularity in this location is thought to represent chronic avulsion of the insertion of the adductor magnus muscle. B, On the AP view, the lesion appears as a well-marginated lucent lesion (arrow) along the medial aspect of the distal femoral metaphysis. In this patient a bone island is also present in the distal femoral epiphysis (arrowhead) .


Benign Fibrous Cortical Defects


Benign fibrous cortical defects, or nonossifying fibromas, are commonly encountered lesions of no clinical significance. They are seen in as many as 40% of children at some time during development and are most common between 5 and 6 years of age. The term nonossifying fibroma is typically reserved for lesions larger than 3 cm. They occur most commonly within the bones around the knee and in the distal tibia. They appear as eccentrically based, well-defined, bubbly, lucent lesions. These benign tumors have a narrow zone of transition with thin cortical rims ( Figs. 7-7 through 7-9 ) and are typically round or oval in shape. When the characteristic pattern is identified, no further imaging or follow-up is necessary. Occasionally a pathologic fracture can occur through the lesion (see Fig. 7-9 ). Over time, benign fibrous cortical defects become more sclerotic and eventually resolve (see Fig. 7-7 ). When imaged during this healing process, they are sometimes referred to as ossifying nonossifying fibromas.




▪ FIGURE 7-7


Benign Fibrous Cortical Defect.

AP radiograph of the ankle in a 14-year-old male shows an eccentrically based lucent lesion (arrow) with a narrow zone of transition and a sclerotic border. The eccentric location in bone and appearance are typical of a fibrous cortical defect. This lesion is slightly more sclerotic than the typical benign fibrous cortical defect representing early healing.



▪ FIGURE 7-8


Nonossifying Fibroma.

AP ( A ) and lateral ( B ) radiograph in a 14-year-old male shows a large, expansile lucent lesion (arrow) of the distal tibia. This lesion is eccentrically based with a narrow zone of transition and a sclerotic border. The lesion (arrow) is hypointense on both the sagittal T1-weighted ( C ) and T2-weighted ( D ) images of the ankle. The abnormal signal ( arrowheads in C and D ) in the anterior aspect of the talus is due to a stress fracture.



▪ FIGURE 7-9


Pathologic Fracture Through a Nonossifying Fibroma.

AP ( A ) and lateral ( B ) views of the ankle show a spiral fracture (arrows) centered in an eccentrically based lucent lesion of the distal tibia. This fracture extends to the physis, making it a Salter-Harris type II fracture.




▪ Trauma


Fractures in children differ from those in adults for multiple reasons. Children’s bones have higher water content and are thus more pliable with a greater propensity to deform before breaking. This is akin to a new branch on a tree. Green sticks, with their higher water content, bend and deform before breaking.


The term incomplete fracture refers to a fracture that does not extend through the entire diameter of the cortex. Because children’s bones are more elastic, incomplete fractures occur more commonly in children than adults. There are a number of types of incomplete fractures. Plastic bowing deformity ( Figs. 7-10 and 7-11 ) is diagnosed when there is a greater than expected curvature of the bone after trauma without a discrete fracture line. This type of fracture occurs almost exclusively in the radius, ulna, or fibula. At times this injury can be difficult to diagnose, and it is not until the follow-up image, when periosteal new bone is present, that the fracture can confidently be diagnosed. A buckle fracture is a concave buckling of the cortical surface of a long bone. Buckle fractures may be subtle and may appear only as an increase in acute angulation of a normally gentler curve ( Figs. 7-12 and 7-13 ). Buckle fractures are most common in the distal radius and ulna, the metacarpals and metatarsals, the phalanges, and the tibia. Finally, a greenstick fracture is an incomplete fracture along the cortex of the convex margin of the bowing ( Figs. 7-11 and 7-14 ). Greenstick fractures are most common in the forearm. Which name you give an incomplete fracture is not important. What is important is recognizing that a fracture is present when it has one of these incomplete appearances.




▪ FIGURE 7-10


Plastic Bowing Deformity.

AP radiograph of the ankle in an 11-year-old male shows a transverse fracture (arrow) of the distal tibial diaphysis and a plastic bowing deformity (arrowhead) of the distal fibula.



▪ FIGURE 7-11


Incomplete Fractures of the Radius and Ulna.

AP ( A ) and lateral ( B ) radiographs of the forearm in a 4-year-old female show a greenstick fracture of the radius (arrow) and plastic bowing deformity of the ulna (arrowhead) . The lateral view better shows the bowing and greenstick fractures. In greenstick fractures the fracture line is along the convex margin of the cortex.



▪ FIGURE 7-12


Buckle Fractures of the Distal Radius and Ulna.

AP ( A ) and lateral ( B ) radiographs of the wrist show buckle fractures of the distal radius (arrow) and ulna (arrowhead) . Buckle fractures can be very subtle on the AP view.



▪ FIGURE 7-13


Buckle Fractures of the Proximal Phalanx of the Ring and Small Fingers.

AP ( A ) and lateral ( B ) radiographs of the ring finger in a 4-year-old male show a subtle contour irregularity of the proximal aspect of the proximal phalanx of the ring finger (arrow) . On the AP view a small portion of the small finger is included and shows a similar buckle fracture (arrowhead) .



▪ FIGURE 7-14


Greenstick Fractures.

AP ( A ) and lateral ( B ) radiographs of the forearm in an 11-year-old male show incomplete fractures of the proximal third of the radius (arrow) and ulna (arrowhead) .


The potential for healing and the healing rate of fractures also differ in children and adults. Younger children heal very quickly. Periosteal reaction can be expected to be radiographically present 10 to 14 days after injuries in children. Children also tend to heal completely. Nonunited fractures are very uncommon in children. Fracture remodeling is also rapid and impressively complete in fractures of pediatric long bones. Normal alignment is typically restored.


Involvement of the Physis


One of the potential problematic issues with fractures in children is involvement of the physis. The physis is involved in as many as 18% of pediatric long bone fractures. Physeal involvement may result in growth arrest of that limb and in a higher rate of necessary internal fixation. The standard classification for physeal fractures is that by Salter and Harris. It divides fractures into five types according to whether there is involvement of the physis, epiphysis, or metaphysis, as determined by radiography ( Fig. 7-15 ). Fractures with higher numbers by the Salter-Harris classification system have a greater incidence of complications. Type 1 fractures involve only the physis ( Fig. 7-16 ). They tend to occur in children younger than 5 years of age. On radiography the epiphysis may appear to be displaced in comparison with the metaphysis. However, type 1 fractures often reduce before the radiographs being obtained, making diagnosis extremely difficult. The potential findings of a type 1 fracture include soft tissue swelling adjacent to the physis, asymmetric widening of the physis, and/or displacement of the epiphysis. Salter-Harris type 1 injuries are uncommon and may only occur at the distal fibula and the proximal femur (as in a slipped capital femoral epiphysis [SCFE]). Type 2 fractures involve the metaphysis and physis but do not involve the epiphysis ( Figs. 7-9 and 7-17 ). They are the most common type of physeal injury, accounting for up to 75% of Salter-Harris fractures. On radiography there is typically a triangular fragment of the metaphysis attached to the physis and epiphysis. Type 3 fractures involve the physis and epiphysis but not the metaphysis( Figs. 7-18 and 7-19 ). Type 3 injuries have a greater predisposition for growth arrest. Type 4 injuries involve the epiphysis, physis, and metaphysis and, like type 3 injuries, are associated with a high rate of growth arrest ( Figs. 7-20 and 7-21 ). Type 5 fractures consist of a crush injury to part of or all of the physis. Like type 1 injuries, type 5 injuries are extremely difficult to diagnose. Often a diagnosis can be made only with a suspicious clinical history and comparison to the contralateral physis. With all Salter-Harris type fractures, it is important to assess the physis on follow-up images. Posttraumatic growth arrest is detected radiographically by demonstration of a bony bridge across the physis ( Fig. 7-22 ).




▪ FIGURE 7-15


Diagram Showing Salter-Harris Classification of Fractures Involving the Physis.



▪ FIGURE 7-16


Salter-Harris Type I Fracture.

AP ( A ) and oblique ( B ) radiographs of the ankle in a 13-year-old female show widening of the distal fibular physis (arrow) compared with the distal tibial physis. There was associated lateral soft tissue swelling. AP ( C ) and oblique ( D ) images in the same patient 2 weeks later show mild healing with faint periosteal new bone formation (arrow) adjacent to the distal fibular metaphysis.



▪ FIGURE 7-17


Salter-Harris Type II Fracture.

AP radiograph of the small finger in a 9-year-old male shows a fracture of the proximal metaphysis of the proximal phalanx of the small finger. The fracture extends to the physis along its radial side (arrow) .



▪ FIGURE 7-18


Salter-Harris Type III Fracture.

AP radiograph of the ankle in a 9-year-old male shows a fracture of the epiphysis of the distal tibia (arrow) . The ankle joint is disrupted by this fracture.



▪ FIGURE 7-19


Salter-Harris Type III Fracture.

AP radiograph of the wrist in a 17-year-old male shows a fracture (arrow) of the distal epiphysis of the radius.



▪ FIGURE 7-20


Salter-Harris Type IV Fracture.

AP radiograph of the ankle in a 14-year-old male shows a fracture (arrow) of the distal tibial metaphysis and epiphysis.



▪ FIGURE 7-21


Salter-Harris Type IV Fracture.

Oblique radiograph of the hand in a 13-year-old female shows a fracture of the proximal epiphysis of the proximal phalanx of the middle finger. There are small fragments of bone (arrow) arising from the proximal metaphysis making this a Salter-Harris type IV fracture.



▪ FIGURE 7-22


Premature Physeal Fusion Secondary to a Salter-Harris Type II Fracture.

A, AP radiograph of the left ankle at time of injury in an 11-year-old female shows widening (arrow) of the medial aspect of the distal tibial physis. There are small ossific fragments adjacent to the distal metaphysis, making this a Salter-Harris type II fracture. B, AP radiographs of both ankles 1 year later show premature fusion of the left distal tibial physis (arrow) . C, The premature fusion (arrow) is confirmed on CT. The oblique lucency along the lateral aspect of the distal tibial metaphysis is related to hardware used to fix the fracture internally.


Commonly Encountered Fractures by Anatomic Location


Pediatric fractures have unique features in almost all locations. The following material reviews several of the more commonly encountered areas.


Wrist


The wrist is the most common fracture site in children. Most fractures of the distal forearm are buckle or transverse fractures of the distal metaphysis of the radius, with or without fracture of the distal ulnar metaphysis or styloid ( Figs. 7-13 and 7-23 ). It is important to assess all fractures of the distal radius for extension of the fracture line to the physis because the distal radius is also the most common area of physeal fracture (28% of physeal injuries occur in the distal radius). Displacement or obliteration of the pronator fat pad indicates a fracture or deep soft tissue injury. The normal pronator fat pad is visualized on a lateral view of the forearm as a thin line of fat with a mildly convex border. In most distal forearm fractures the convexity of the pronator fat pad is increased or the fat pad becomes obliterated by soft tissue attenuation.




▪ FIGURE 7-23


Salter-Harris Type II Fracture of the Distal Radius and Ulnar Styloid Fracture.

AP ( A ) and lateral ( B ) radiographs of the wrist in an 8-year-old female show fractures of the distal radius and ulna. The fracture of the ulna is mildly complex. There is a faint vertical component of the fracture (arrowhead) extending to the physis (seen on A ), making this a Salter-Harris type II fracture. In addition to the fracture of the radius, an ulnar styloid fracture (arrow) is also present.


Elbow


There are several unusual features that make elbow injuries in children different from those in adults. In contrast to adults, in whom fracture of the radial head is the most common injury, children most commonly experience supracondylar fractures ( Figs. 7-24 and 7-25 ). They occur secondary to hyperextension that occurs when falling on an outstretched arm. As many as 25% of such fractures are incomplete and may be subtle on radiography. On radiographs there can be posterior displacement of the distal fragment such that a line drawn down the anterior cortex of the humerus (anterior humeral line) no longer bisects the middle third of the capitellum (see Fig. 7-24 ). The fracture line is usually best seen through the anterior cortex of the distal humerus on the lateral view. A joint effusion is typically evident. Elbow effusions are identified when there is displacement of the posterior fat pad, resulting in its visualization on a lateral view ( Figs. 7-24 through 7-26 ). Normally the posterior fat pad rests within the olecranon fossa and is not visible on a true lateral view of the elbow. The anterior fat pad, which is often visible normally, may become prominent and have a prominent apex anterior convexity.




▪ FIGURE 7-24


Supracondylar Fracture.

AP ( A ) and lateral ( B ) radiographs of the elbow in a 9-year-old male show a supracondylar fracture. The fracture line is often difficult to see on the AP view. In this case there is contour deformity on the lateral aspect of the humeral metaphysis (arrow) . The fracture line extends through the metaphysis at this plane. On the lateral view the line drawn along the anterior cortex of the humerus does not intersect the capitellum. The fracture line is more visible on this view. Note the large joint effusion (arrow) .



▪ FIGURE 7-25


Supracondylar Fracture.

Lateral radiographs of the elbow in a 3-year-old female show a supracondylar fracture and large joint effusion. The fracture line (arrow) is seen along the anterior surface of the distal humerus.



▪ FIGURE 7-26


Elbow Effusion.

Lateral radiograph of the elbow in a 4-year-old male shows a moderate joint effusion, as demonstrated by the elevation of the posterior fat pad (arrow) . The anterior fat pad is also displaced. No fracture was present on this image or on subsequent follow-up (not shown).


There is much debate about the significance of a traumatic elbow effusion in the absence of a visualized fracture (see Fig. 7-26 ). It is often taught that such a joint effusion is synonymous with an occult fracture. However, studies have shown that fractures are probably present in 50% or fewer cases. The point is moot because traumatic injury to the elbow is treated by splinting, whether a subtle fracture is identified or not. If pain persists, a repeat radiograph if often obtained at the follow-up orthopedic appointment and can be used to assess for signs of healing.


Other elbow injuries include fractures of the radial neck and lateral condyle ( Fig. 7-27 ) and avulsion of the medial epicondyle (Little League elbow; Figs. 7-28 and 7-29 ). With avulsion of the medial epicondyle (10% of elbow injuries), the medial epicondyle may become displaced and even entrapped within the elbow joint (see Fig. 7-29 ). It is important to know the predictable order of maturity of the elbow ossification centers so that a displaced medial epicondyle is not missed. The order can be remembered by the mnemonic CRITOE (capitellum, radial head, internal [medial] epicondyle, trochlea, olecranon, external [lateral] epicondyle).




▪ FIGURE 7-27


Lateral Condylar Fracture.

AP ( A ) and lateral ( B ) radiographs of the elbow in a 6-year-old male show a lateral condylar fracture. The fracture is better seen on the AP view, where there is a thin sliver of bone adjacent to the fracture line (arrow) in the distal lateral humeral metaphysis. There is also considerable lateral soft tissue swelling. The fracture is harder to see on the lateral view. However, a small posterior elbow effusion is present.



▪ FIGURE 7-28


Medial Epicondyle Avulsion.

AP radiograph of the elbow in a 14-year-old female shows avulsion of the medial epicondyle (arrow) . The remainder of the physes of the elbow are fused. There is marked medial soft tissue swelling.



▪ FIGURE 7-29


Elbow Dislocation with Avulsion and Entrapment of the Medial Epicondyle.

AP ( A ) and lateral ( B ) radiographs of the elbow in a 10-year-old female show a lateral dislocation of the elbow. There is a circular ossific density (arrow) overlying the distal humerus on the AP view that represents the avulsed medial epicondyle. On the lateral view the avulsed fragment (arrow) is shown to be entrapped in the elbow joint. Note that the capitellum, radial head, trochlea, and olecranon are already ossified.


Whenever there is a fracture of the forearm, it is important to evaluate the radial-capitellar joint for potential dislocation of the radial head. The radial head should align with the capitellum on both the anteroposterior (AP) and lateral views. If it does not, radial head dislocation should be suspected ( Fig. 7-30 ). When a radiocapitellar dislocation is present, it is important to image the entire forearm to look for a fracture-dislocation injury. A Monteggia fracture is a dislocation of the head of the radius with an associated fracture of the ulnar diaphysis (see Fig. 7-30 ).




▪ FIGURE 7-30


Monteggia Fracture.

AP ( A ) and lateral ( B ) radiographs of the forearm show a fracture of the midulna diaphysis (arrow) and dislocation of the proximal radius. On both views the line drawn through the center of the radius (parallel to its long axis) does not intersect the capitellum.


Ankle


The ankle in a commonly injured joint due to combination of inversion and eversion injuries with weight bearing. There are two common fractures that are unique in adolescents, triplane fractures and juvenile Tillaux fractures. Like the name implies, a triplane fracture is a fracture in three planes: the coronal plane through the tibial metaphysis, transverse plane through the physis, and sagittal plane through the epiphysis ( Fig. 7-31 ). Because the fracture extends through the metaphysis and epiphysis, this is a Salter-Harris type IV fracture. Triplane fractures occur in adolescents in whom the growth plate is beginning to close. It is important to evaluate the fracture carefully because internal fixation is performed if there is more than 2-mm displacement of the fracture fragment. Often a CT is performed to evaluate the fracture and the degree of displacement more accurately. Fibular fractures are present approximately half of the time.




▪ FIGURE 7-31


Triplane Fracture.

Oblique ( A ) and lateral ( B ) radiographs of the ankle in a 14-year-old female show fractures of the tibia (arrow) and fibula (arrowhead) . The tibia fracture extends from the tibial metaphysis, through the physis, and into the epiphysis. The lateral epiphysis is displaced laterally. The metaphyseal component of the fracture is better seen on the lateral view. Coronal ( C ) and sagittal ( D ) images from a CT of the ankle in the same patient show the fractures more obviously. The tibia fracture (arrow) is a Salter-Harris type IV fracture extending in three different planes.


Juvenile Tillaux fractures are Salter-Harris type III fractures of the distal tibia. Like triplane fractures, they occur in adolescents in whom the growth plate is beginning to close. The fracture occurs because the medial tibial physis closes before the lateral physis. The differences in structural stability lead to this fracture pattern when there is abduction and external rotation of the ankle. On x-ray there is a fracture line through the distal tibial epiphysis and widening of the medial aspect of the ankle mortise ( Fig. 7-32 ). CT is performed to evaluate the amount of fracture displacement. Orthopedic surgeons will perform internal fixation if the fracture is displaced by more than 2 mm.




▪ FIGURE 7-32


Juvenile Tillaux Fracture.

AP ( A ) and oblique ( B ) radiographs of the ankle in a 12-year-old female show a fracture (arrow) of the lateral aspect of the distal epiphysis of the tibia. The fracture fragment is displaced laterally by 2 mm. C, Coronal CT of the ankle shows the Salter-Harris type III fracture (arrow) of the distal tibia.


Toddler Fracture


There are a number of fractures referred to as toddler fractures. The most common of these is a nondisplaced oblique or spiral fracture of the midshaft of the tibia ( Fig. 7-33 ). Such an injury is relatively common and occurs when a child first begins to walk. Most children present with failure to continue to walk or refusal to bear weight on that extremity. Oblique views often demonstrate the fracture better than do frontal or lateral views. When diagnosing this fracture, it is important to look at the patient’s age because a spiral fracture in a child who is not yet walking can be a fracture of abuse. Other types of toddler fractures include stress-type fractures involving the calcaneus or cuboid ( Figs. 7-34 and 7-35 ).




▪ FIGURE 7-33


Spiral Fracture of the Tibia.

AP ( A ), oblique ( B ), and lateral ( C ) radiographs of the ankle in a 1.5-year-old male show a spiral fracture of the distal tibia (arrows) . The fracture plane is continuous throughout its course, even though it appears as two fracture lines on the AP and lateral views.



▪ FIGURE 7-34


Stress Fractures of the Calcaneus and Cuboid.

A, Lateral radiograph of the foot at time of injury shows an oblique fracture of the distal tibia. B, Repeat radiograph of the foot performed 1 month later shows new linear areas of sclerosis in the posterior calcaneus (arrowhead) and posterior cuboid (arrow) . The tibial fracture is not well seen, related to healing.



▪ FIGURE 7-35


Stress Fractures of the Calcaneus.

Oblique ( A ) and lateral ( B ) radiographs of the foot in a 2.5-year-old male show a linear area of sclerosis in the cuboid (arrow) consistent with a stress fracture.


Avulsion Fractures in Adolescents


An avulsion injury is a structural failure of bone at a tendon or aponeurotic insertion and is related to a tensile force being applied by a musculoskeletal unit. Adolescents are prone to avulsive injuries because of a combination of their propensity to have great strength, their ability to sustain extreme levels of activity, and their immature, growing apophyses. The growing apophysis is often more prone to injury than the adjacent tendons. The sites of insertion of muscles capable of generating great forces are most predisposed to avulsion injuries.


Radiologists may encounter findings of chronic avulsion when patients are imaged for pain or incidentally when imaging is performed for other reasons. The irregularity and periostitis that can be associated with chronic avulsions should not be misinterpreted as suspicious for malignancy. In addition, if unwarranted biopsies of these areas are performed, the histologic changes associated with the healing callus of the avulsion injury may be misinterpreted as malignancy. The most common sites of avulsion occur within the pelvis, where muscles capable of great force attach. Common sites of pelvic apophyseal avulsions and their associated muscular attachments include the iliac crest (transversalis, internal oblique abdominalis, external oblique abdominalis; Fig. 7-36 ); anterior superior iliac spine (Sartorius; Fig. 7-37 ); anterior inferior iliac spine (rectus femoris; Fig. 7-38 ); ischial apophysis (hamstring muscles: biceps femoris, gracilis, semimembranosus, semitendinosus; Fig. 7-39 ); and lesser trochanter (iliopsoas). The radiographic findings of avulsion injuries include displacement of the ossified apophysis from normal position and variable, often exuberant amounts of associated periosteal new bone formation.




▪ FIGURE 7-36


Avulsion Fracture of the Iliac Crest.

AP ( A ) and frog-leg lateral ( B ) radiographs of the pelvis in a 13-year-old female show asymmetric widening of the left lateral iliac crest (arrow) . Coronal ( C ) and three-dimensional reconstructed ( D ) images from a CT confirm the findings (arrow) . E, AP radiograph of the pelvis obtained 3 weeks later shows healing with new bone formation (arrow) inferior to the avulsed fragment.



▪ FIGURE 7-37


Avulsion Fracture of the Anterior Superior Iliac Spine.

AP ( A ) and frog-leg lateral ( B ) radiographs of the pelvis in a 16-year-old male show a large avulsion fracture of the right anterior superior iliac spine (arrow) . The fracture fragment is displaced inferiorly.



▪ FIGURE 7-38


Avulsion Fracture of the Anterior Inferior Iliac Spine.

Frog-leg lateral radiograph of the pelvis in a 15-year-old male shows an avulsion fracture of the right anterior inferior iliac spine (arrow) . Pelvic avulsion fractures are often subtle as in this case.



▪ FIGURE 7-39


Avulsion Fracture of the Ischium.

AP radiograph of the pelvis in a 13-year-old female shows a large avulsion fracture of the left ischial apophysis (arrow) .


When involving a joint, avulsive injuries can occur at the cortical insertion site of a ligament or tendon. The knee is the joint most commonly associated with avulsive injuries. Many of these injuries occur exclusively in children and adolescents. Common sites of knee avulsion fractures and their associated tendinous or ligamentous attachments include the anterior medial tibial spine (anterior cruciate ligament; Fig. 7-40 ); lateral tibial rim, also known as a Segond fracture (lateral collateral ligament; Fig. 7-41 ); fibular head (conjoined tendon with biceps femoris; Fig. 7-42 ); tip of the fibular head (arcuate ligament); inferior pole of the patella, also known as the patellar sleeve (proximal patellar tendon; Figs. 7-43 and 7-44 ); and tibial tubercle (distal patellar tendon Fig. 7-45 ). Many of these injuries present with sudden pain and a joint effusion. MRI is often indicated because these injuries are associated with other internal derangement.




▪ FIGURE 7-40


Tibial Spine Avulsion Fracture.

AP ( A ) and lateral ( B ) radiographs of the knee in a 7-year-old male show an avulsion fracture of the tibial spine. The avulsed fragment (arrow) is easier to see on the AP view, where it resides just lateral to the tibial spine. On the lateral view the donor site (arrowhead) is visible and there is a large joint effusion. C, Sagittal T2-weighted MRI with fat saturation shows the avulsed fragment (arrow) as a linear area of low signal in the knee joint. The anterior cruciate ligament (arrowhead) is attached to the fragment and is no longer taut. There is also a large hemarthrosis.



▪ FIGURE 7-41


Segond Fracture.

AP ( A ) and lateral ( B ) radiographs of the knee in a 12-year-old female show an avulsion fracture of the lateral aspect of the proximal tibial epiphysis (arrow) . There is moderate lateral soft tissue swelling and a large joint effusion.



▪ FIGURE 7-42


Fibular Head Avulsion Fracture.

AP ( A ) and PA ( B ) radiographs of the knee in a 14-year-old female show an avulsion fracture of the lateral aspect of the proximal fibula (arrow) . A tibial spine avulsion is also present and better seen on the AP view.



▪ FIGURE 7-43


Patellar Sleeve Avulsion Fracture.

A, Lateral radiograph of the knee in a 10-year-old female shows an avulsion fracture (arrow) of the inferior pole of the patella. Sagittal proton density ( B ) and sagittal T2-weighted ( C ) images show the avulsed fragment (arrow) is attached to the patellar tendon. The donor site along the anterior inferior aspect of the patella is irregular.



▪ FIGURE 7-44


Patellar Sleeve Avulsion Fracture.

Lateral radiograph of the knee in a 12-year-old male shows an avulsion fracture of the inferior pole of the patella (arrow) . The patella is slightly higher than expected, in an alta position. There is thickening and irregularity of the proximal patellar tendon.



▪ FIGURE 7-45


Tibial Tubercle Avulsion Fracture.

Lateral radiograph of the knee in a 16-year-old male shows an avulsion fracture of the tibial tuberosity (arrow) . A second avulsion fragment is present adjacent to the patella tendon insertion (arrowhead) .


Chronic avulsion injuries are also common in the adolescent knee. Avulsion of the patellar tendon at its attachment to the patella is called Sinding-Larsen-Johansson syndrome. It occurs most commonly in children between the ages of 10 and 14 years. Symptoms include localized pain and swelling over the inferior aspect of the patella associated with restricted knee motion. Radiography demonstrates irregular bony fragments at the inferior margin of the patella, associated with adjacent soft tissue swelling and thickening and indistinctness of the patellar tendon ( Fig. 7-46 ). Chronic avulsive injury of the patellar tendon at its inferior attachment is referred to as Osgood-Schlatter disease (tibial tuberosity avulsion). It is a common disorder that most often affects active adolescent boys. Symptoms include pain and swelling over the tibial tuberosity. Radiography demonstrates bony fragmentation of the tibial tuberosity, associated adjacent soft tissue swelling, and thickening and indistinctness of the patellar tendon ( Fig. 7-47 ).




▪ FIGURE 7-46


Sinding-Larsen-Johansson Syndrome.

A, Lateral radiograph of the knee in a 10-year-old male with chronic knee pain shows fragmentation of the inferior pole of the patella (arrow) and thickening of the origin of the patellar tendon (arrowhead) . B, Sagittal T2-weighted image of the knee shows the ossific fragment (arrow) of the lower pole of the patella along with bone marrow edema pattern in the fragment and the inferior patella. The proximal patella tendon is thickened (arrowhead) with edema in the tendon and within Hoffa fat pad.



▪ FIGURE 7-47


Osgood-Schlatter Disease.

Lateral radiographs of the right ( A ) and left ( B ) knee in a 13-year-old male show fragmentation and irregularity of the tibial tuberosity (arrow) at the site of the patellar tendon insertion. The patellar tendon is thickened bilaterally, and there is overlying soft tissue swelling.


Child Abuse


Child abuse, also referred to as the more politically correct and less graphic nonaccidental trauma , is unfortunately common. According to data from the U.S. Department of Health and Human Services, it is estimated that approximately 750,000 children are abused and 1600 killed each year in the United States ( www.acf.hhs.gov/programs/cb/resource/cwo-08-11 ). Most abused children are less than 1 year of age and almost all are less than 6 years of age. When clinical or imaging findings are suspicious for potential abuse, a radiographic skeletal survey is typically obtained. The purpose of the skeletal survey is to document the presence of findings of abuse. In young children a head CT is often performed to identify intracranial signs of abuse. Other tests sometimes used include a repeat skeletal survey after approximately 2 weeks to look for healing injuries not seen on the initial skeletal survey, skeletal scintigraphy, abdominal CT, and MRI of the brain. The identification and reporting of findings of child abuse by the radiologist is an important task. False-positive cases can cause a nonabused child to be removed from his or her family, whereas false-negative cases can result in a child’s returning to a potentially life-threatening environment.


The radiographic findings of abuse vary in their specificity. One of the highly specific findings is the presence of posterior rib fractures occurring near the costovertebral joints ( Fig. 7-48 ). These are thought to occur when an adult squeezes an infant’s thorax. Such rib fractures may be subtle before development of callus formation. The evaluation for rib fractures should be a routine part of the evaluation of the chest radiograph of any infant. Another finding that is highly specific for abuse is the metaphyseal corner fracture ( Fig. 7-49 ). This fracture extends through the primary spongiosa of the metaphysis, the weakest portion, and usually occurs secondary to forceful pulling of an extremity. The broken metaphyseal rim appears as a corner fracture (a triangular piece of bone) when seen tangentially or as a crescentic rim of bone (referred to as a bucket-handle fracture) when seen obliquely. Other fractures associated with abuse include those of the scapula, spinous process, and sternum. Spiral long bone fractures in nonambulatory children are also highly suspicious. Multiple fractures in children of various ages (some with callus and some acute), as well as multiple fractures of various body parts, are highly suspicious for abuse (see Fig. 7-48 ). In fact, any fracture in an infant should be viewed with suspicion because as many as 30% of fractures in infants are secondary to abuse. Extraskeletal findings seen in abuse include acute or chronic subdural hematoma, cerebral edema (asphyxia), intraparenchymal brain hematoma ( Fig. 7-50 ), lung contusion, duodenal hematoma, solid abdominal organ laceration, and pancreatitis.




▪ FIGURE 7-48


Child Abuse.

Frontal view of the chest in a 1-month-old male shows multiple fractures of different ages. There are healing fractures of the left third through eighth posterior ribs (arrowheads) . In addition, there is an acute fracture of the mid left humerus (arrow) .



▪ FIGURE 7-49


Child Abuse.

AP view of the knee in a 1-month-old male shows a metaphyseal corner fracture of the distal, lateral femoral metaphysis (arrow) . A fracture in a bucket handle configuration (arrowhead) is present in the proximal tibia.



▪ FIGURE 7-50


Child Abuse.

A, Lateral view of the skull shows a diastatic fracture of the left parietal bone (arrows) . B, The fracture (arrows) is more visible on the three-dimensional, reformatted image from a subsequent CT. Note the difference between the fracture with its smooth borders and the sutures (arrowhead) with their jagged borders. Axial CT images through the lateral ventricles ( C ) and at the vertex ( D ) show edema with loss of gray matter–white matter differentiation, loss of the normal gyral pattern, and effacement of the sulci. In addition, there is a small hyperdense collection adjacent to the posterior falx cerebri (arrow) . The findings were new in comparison with a E and F CT performed 2 days earlier for a different event.


The clinical and imaging findings of abuse do not usually require differential diagnosis. However, other entities that may cause multiple fractures or that may cause radiographic findings that could be confused with injury, such as periosteal reaction, should always be considered. The other disorders that may present with multiple fractures in an infant are osteogenesis imperfecta (OI) and Menkes syndrome. Both of these entities are also associated with excessive wormian bones and osteopenia. There has been some debate about whether some patients diagnosed with child abuse do not suffer from vitamin D deficiency. Rickets, caused by vitamin D deficiency, is not a cause of the fractures specific for abuse, and most pediatric radiologists believe that the imaging appearance of child abuse and that of rickets do not overlap.

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Aug 25, 2019 | Posted by in PEDIATRIC IMAGING | Comments Off on Musculoskeletal
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