Radiol med DOI 10.1007/s11547-015-0615-0

PAEDIATRIC RADIOLOGY

Sports injury of the pediatric musculoskeletal system Karen Rosendahl1,2 · Peter J. Strouse3 

Received: 27 November 2015 / Accepted: 9 December 2015 © Italian Society of Medical Radiology 2016

Abstract  Sports related injuries are common in children and adolescents, with a reported incidence of around one in ten children each year. Boys incur more and severer sports injuries than girls, and chance for injury is greater with contact or jumping sports. Sports injuries seen in children under 10-years of age are non-specific, including contusions, mild sprains, and extremity fractures, usually Salter fractures of the physes (growth plate) or plastic fractures. In the very young athlete, sports injury of the ligaments or muscle is rare as are spine or head injuries. With growth and adolescence, the intensity of sports involvement increases. Pre-pubertal children still have open physes that are prone to injury, both acute or due to stress from a repetitive activity. In addition to injury of the physes of the long bones, injuries to the physes of apophyses are common. Ligamentous injury is uncommon before physeal closure, but can occur. After the physes fuse, ligamentous This article is based on Peter J. Strouse, Karen Rosendahl (2013) Specific Aspects of Sports Related Injuries of the Pediatric Musculoskeletal System. In: Hodler J, von Schulthess GK, Zollikofer ChL (eds) Musculoskeletal Diseases 2013–2016, Springer-Verlag Italia, Milan pp 194–202. © Springer-Verlag Italia 2013. With kind permission of Springer-Verlag Italia. All Rights Reserved. * Karen Rosendahl karen.rosendahl@helse‑bergen.no Peter J. Strouse [email protected] 1

Section of Pediatric Radiology, Haukeland University Hospital, Jonas Lies vei 65, 5020 Bergen, Norway

2

Department of Clinical Medicine, K1, University of Bergen, Bergen, Norway

3

C.S. Mott Children’s Hospital, 1540 E. Medical Center Drive, 3‑220, Ann Arbor, MI 48109, USA



injury is seen with patterns similar to adults. This review will include a description of sports related injuries seen in children and adolescents. We will concentrate on injuries that are specific for the growing skeleton, with a brief mention of those seen after fusion of the physes. Keywords  Sport · Injury · Children · Musculoskeletal · Imaging

Sports injury of the pediatric musculoskeletal system Factors affecting the incidence and anatomic distribution of sports injury in pediatric patients include age, gender, the type of sport, intensity of participation and the position played [1–3]. In a study from the United Kingdom, approximately 4 in 5 of children between the ages of 5 and 15 years old were participants in an organized sport [4]. 1 in 9 of those children involved in sport was characterized as involved with “intensive” training [4]. Sports injuries are therefore common in children and adolescents. About 1 in 10 children will present with a sports injury each year. Boys incur more sports injuries than girls, and severe injuries are more common in boys. This probably reflects the sports involved and greater aggression in boys. Chance for injury is greater with contact or jumping sports, with American football followed by wrestling, basketball, soccer and baseball in the likelihood for injury [5]. In cold weather climates, injuries due to skiing and snowboarding are also common [6]. Involvement in organized sports begins in the first decade of life. Sports injuries seen in children under 10 years of age are non-specific, consisting of contusions, mild sprains, and extremity fractures, usually Salter fractures of

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the growth plate or plastic fractures (i.e., buckle or greenstick factures). In the very young athlete, sports injury of the ligaments or muscle is rare as are spine or head injuries. With growth and adolescence, the intensity of sports involvement increases and sports become more competitive, more intense and more physical. However, prepubertal children still have open physes (growth plates) that predispose to injury. The physes are the weakest link in the anatomic chain. Injury mechanisms which cause ligament injury in individuals with closed physes are prone to cause physeal injury in a skeletally immature athlete. Physeal injury from sport may be acute or due to stress from a repetitive activity [7, 8]. In addition to injury of the physes of the long bones, injuries to the physes of apophyses are common. An apophysis is a growth center which does not contribute to longitudinal growth. Since apophyses are sites of tendon origin or insertion, they are prone to avulsive injury, which may be acute or due to repetitive stress. Ligamentous injury is uncommon before physeal closure, but can occur. After the physes fuse, ligamentous injury is seen with patters similar to adults. Adolescents are not only prone to stress injury of the physes, but also stress injury away from the growth plate within the bones. These stress injuries are very similar in clinical presentation and imaging appearance to those occurring in adults. Underlying congenital anomalies (i.e., tarsal coalition, os trigonum) may predispose to stress injury or may become symptomatically evident with increased participation in sport. Osseous tumors or infection may masquerade as a sports injury. A sports injury may provide the nidus for a musculoskeletal infection. Post-traumatic myositis ossificans may mimic an aggressive soft tissue neoplasm. Those interpreting imaging for sports injury in children need be familiar with the imaging patterns of injury and processes that may predispose to injury, mimic injury and occur as a consequence of injury. We will present sports injuries that are specific to children and adolescents. Less emphasis will be placed on injuries which are more common in adults and occur principally in older adolescents with fused physes.

Shoulder Injuries of the shoulder are more common in the latter half of the second decade, and with participation in contact sports such as wrestling, American football and hockey [9]. In younger children, injury to the physis is more common than injury of the soft tissues of the glenohumeral joint. Clavicular fractures are common at all ages. Shoulder dislocations are more frequent with skeletal maturity [10]. MR findings of glenohumeral instability post-shoulder

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Fig. 1  Little leaguer’s shoulder in a 15-year-old boy. Irregularity and widening of the lateral aspect of the proximal humeral physis are noted with extrusion of cartilage into the adjacent metaphysis (arrows)

Fig. 2  Acute medial epicondylar apophysis avulsion (arrow) in a 14-year-old boy. The patient experience acute pain while pitching a baseball

dislocation in adolescents are very similar to those seen in adults. Injuries at the acromioclavicular joint are uncommon in adolescents, but do occur. An overuse shoulder injury occurring in young adolescents is Little Leaguer’s shoulder [10]. The injury is a stress injury (physiolysis) of the proximal humeral physis due to stress like that from overhead throwing. The injury is most common in teenage baseball pitchers, but can occur in other throwing athletes or tennis players as well. On radiography of little leaguer’s shoulder, there is widening

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and irregularity of the proximal humeral physis (Fig. 1). On MRI, the physis will appear widened and irregular with adjacent bone marrow edema [11]. The clinical presentation will suggest the proper diagnosis. Treatment with cessation of activity leads to abatement of symptoms and resolution of radiologic findings. Another type of overuse injury seen at the shoulder in children, however, rare, is intra-articular disorders (i.e., internal impingement of the shoulder) [10]. Rotator cuff and labral injuries are uncommon, but may occur.

Elbow In young children, an array of elbow fractures is seen. Supracondylar and lateral condylar fractures are the most common patterns. Elbow dislocations are quite uncommon. When a skeletally immature patient suffers an elbow dislocation, the medial epicondylar ossification center should be carefully identified. The medial epicondyle is usually avulsed with the dislocation and becomes trapped in the elbow joint with reduction. Medial epicondylar avulsions more commonly occur due to throwing injury. Medial epicondyle avulsion in the throwing juvenile athlete was described by Brogdon in 1960 as “little leaguer’s elbow” [12]. Classically, the injury occurs during a throw producing acute pain and point tenderness over the medial epicondyle. On radiography, the medial epicondyle will be displaced from its normal location (Fig. 2). Comparison radiographs are usually not necessary, but may be helpful, particularly for the inexperienced observer. If minimally displaced, treatment may be conservative. Displacement of greater than 3 mm is usually considered an indication for surgical reduction and pinning. Adolescent throwing athletes are also prone to other injuries of the elbow, including osteochondritis dissecans of the capitellum, stress injury of the medial epicondyle physis, flexor tendinopathy, ulnar collateral ligament injury and stress injury of the olecranon [13]. Flexor tendinopathy and ulnar collateral ligament injuries are more common after skeletal maturity. Medial epicondylar physeal stress injury may be labeled as “medial epicondylitis” or “little leaguer’s elbow”; however, classic little leaguer’s elbow, as originally reported, is an acute medial epicondyle avulsion fracture [13]. Edema is seen within adjacent bone and soft tissues on fluid sensitive MRI sequences. Pitch or inning limits are imposed in youth baseball aim to prevent injuries to the elbow. Osteochondral injury of the capitellum is a consequence of valgus stress injury [13]. The imaging findings are similar to osteochondral injury at other sites. An irregular lenticular defect is seen within capitellum. MRI is helpful for evaluation of overlying cartilage and assessing stability.

Fig. 3  Gymnast wrist in a 12-year-old girl. The distal radial physis is widened with irregularly of its metaphyseal margin. Symmetric abnormality was noted on the contralateral side

Unstable osteochondral fragments may become loose bodies within the elbow joint. Stress injury of the olecranon is uncommon and is likely due to the stress of triceps muscle contraction occurring during the throwing motion [13, 14].

Wrist and hands Wrist injuries in child and adolescent athletes are common. Most are Salter type fractures involving the physis or plastic fractures (buckle fractures) of the distal radial metaphysis. Stress injury of the distal radial physis is a common injury in gymnasts (“gymnast wrist”) [15]. Symptoms are usually unilateral at presentation; however, both sides are usually affected. As with physeal stress injury at other sites, the physes of the distal radius appear widened and irregular and there is adjacent metaphyseal sclerosis (Fig. 3) [16]. Bone marrow edema is seen on both sides of the physis on MRI [17]. With cessation of gymnastic activity, symptoms and radiological findings resolve. However, continued gymnastic activity will predispose premature physeal fusion, resulting in relative radial shortening and positive ulnar variance (the ulna is long relative to the radius)—this predisposes to carpal impingement and triangular fibrocartilage complex injury. Injury to the carpal bones is rare in children. The carpal bones are not completely ossified and the cartilage “provides a cushion”. Normal ligamentous laxity in children may also be protective. At puberty, injury to the scaphoid bone becomes more common. Imaging findings of scaphoid injury in adolescents are similar to those seen adult

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Fig. 4  Acute avulsion of anterior superior iliac spine (ASIS, arrow) and chronic avulsion of ischial tuberosity (arrowheads) in a 16-yearold boy soccer player. The patient presented with acute pain after a kick due to the ASIS avulsion. Due to displacement of the ischial apophysis and continued activity there is exuberant callous formation

patients. With fracture, the proximal pole of the scaphoid is predisposed to avascular necrosis due to its recurrent blood supply. Other carpal bone injures are distinctly uncommon in pediatric patients. The hook of the hamate may suffer stress injury from repetitive injury occurring with racquet sports or other activity causing repetitive contact to hypothenar portion of the hand. This injury is quite rare in children. Carpal ligament injury in uncommon before puberty. Patterns of metacarpal and phalangeal injury in children are different than in adults due to the composition of the bones and the presents of the physes Active children are subject to physeal injuries of the metacarpals and phalanges which are sometime subtle on radiographs.

Pelvis and hips At the pelvis and hips, there are six apophyseal growth centers: the iliac crest, the anterior superior iliac spine (ASIS), the anterior inferior iliac spine (AIIS), the ischial apophysis, the greater trochanter and the lesser trochanter [18]. Avulsion of an apophyseal growth center is most frequently due to sports injury. Avulsion of the ASIS and the ischial apophysis are most common. Injuries often occur with a specific activity. Avulsion of the ASIS commonly occurs with kicking. Avulsion of the ischial apophysis occurs with hurdling. Iliac crest avulsions occur with wrestling or with sudden direction change while running. The acutely avulsed apophysis is displaced from its normal site (Fig. 4). Stress injuries to the apophyseal physis and healing acute avulsion injuries may appear very similar, with widening and irregularity of the physis. On MRI, there is adjacent soft tissue and bone oedema helping to identify

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Fig. 5  Slipped capital femoral epiphysis in an 11-year-old girl. Anteroposterior image (a) shows widening and irregularity of the left proximal femoral growth plate. A line extended up from the lateral margin of the left femoral neck (Klien’s line) intersects less femoral head than a similar line on the right. The right hip is normal. Posteromedial displacement of the left femoral head relative to the left femoral neck and growth plate widening are better seen on the abduction view (b)

the site of injury. Avulsions may very rarely occur prior to apophyseal ossification. Exuberant callus from a displaced acute apophyseal avulsion fracture may mimic an osseous neoplasm (Fig. 4). Slipped capital femoral epiphysis (SCFE) occurs in young adolescents in the years leading up to physeal fusion. Although SCFE may occur as a sports injury, the disorder is more often not sports related. Affected adolescents are often overweight and may be delayed in sexual maturation. If a child is unable to bear weight on the extremity, the SCFE is termed “unstable” if the child is unable to bear weight and “stable” able to bear weight [19]. Presentation varies with some patients presenting acutely, many with a more chronic indolent process and others with an “acute on chronic” presentation of SCFE. Findings may be quite subtle on radiography. Abduction (frog leg lateral) views and comparison with the unaffected contralateral side aid in diagnosis (Fig. 5). On the order of 20 % of patients will have bilateral SCFE; however, in the absence of an underlying predisposing condition

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findings are rarely symmetric at presentation. Symmetric presentation, particularly in a younger child, is suggestive of an underlying endocrinopathy. The diagnosis of SCFE is made by identifying malalignment of the femoral head and the femoral neck. Ancillary findings include external rotation of the proximal femur, sclerosis or buttressing in the femoral neck, and decrease in height of the femoral head due to its rotation on the femoral neck. If SCFE is not found, the pelvic apophyses should be carefully evaluated. In particular, ASIS avulsion mimics SCFE in clinical presentation. Femoral acetabular impingement (FAI) is increasingly being diagnosed in adolescents [20, 21]. Cam-type FAI deformity of the proximal femur has been reported with some predisposing sports activities [20]. Maldevelopment of the femoral head/neck junction has also been identified as a predisposing condition. The appearance is thought by some to represent a mild and silent slipped capital epiphysis and is seen is up to 6 % of adolescents [22]. Other authors hypothesize that an inherited anomalous development of the femoral head/neck junction leads to insufficient “waisting” of the femoral neck [21]. Patients with FAI present with locking and/or decreased range of hip motion suggestive of associated labral tears or with pain which occurs in extremes of flexion.

Knee Open physes at the knee are weaker than ligaments. In the distal femur and proximal tibia, physeal fractures are common [23]. The composition of bone in a child or young adolescent is immature. Avulsion of the tibial spine occurs in skeletally immature patient with similar mechanisms as those causing anterior cruciate (ACL) ligament injury in skeletally mature patients (Fig. 6). With tibial spine avulsion, the ACL may occasionally be injured, but is usually intact. Injuries of the collateral ligaments and menisci may also occur. A large post-traumatic knee joint effusion in a younger patient should prompt evaluation of the tibial spine for fracture. On cross-table lateral views, a fat/ fluid level is often present, indicative of an intra-articular fracture. Injury to the cruciate and collateral ligaments and menisci is uncommon before skeletal maturing. If a torn lateral meniscus is found in a young patient is an underlying discoid lateral meniscus should be suspected (Fig. 7) [24]. With a tear and displacement of meniscal fragments, it may be challenging to determine the meniscus as discoid in configuration. After skeletal maturity is attained, injuries of the cruciate and collateral ligaments and the menisci are common. Bucket handle meniscal tears with displacement of fragments are relatively common in teenagers [25].

Fig. 6  Tibial spine avulsion in a 13-year-old girl sustained while downhill ski racing. Lateral radiograph of the knee (a) shows a large joint effusion (asterisks) with a fat/fluid level (arrowhead). Irregularity of the tibial spine suggests a fracture (arrow). Sagittal proton density MR image (b) shows the tibial spine avulsion fracture (arrows). The anterior cruciate ligament (A) is attached to the fragment. A large joint effusion (asterisks) is noted

Extensor mechanism injury is common in adolescents, particularly transient lateral patellar dislocation [26]. Predisposing factors include genu valgum, shallow femoral trochlea and patella alta. Patellofemoral stress syndrome and chronic knee pain may occur with patella alta. Extensor mechanism injury and patellar tracking abnormalities

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Fig. 7  Discoid lateral meniscus (arrows) in a 15-year-old boy baseball player. Coronal proton density with fat saturation MR image shows an enlarged lateral meniscus. Ill-defined increased signal is noted within the meniscus due to degeneration. Arrowhead normal medial meniscus

are more common in girls. After dislocation, the patella often reduces immediately and the patient may be unaware that the patella had dislocated. With transient patellar dislocation, osteochondral injuries are often seen at the medial patellar facet, and less commonly, the anterolateral aspect of the lateral femoral condyle. These occur due to impaction occurring with the dislocation and relocation. On radiography, small osteochondral fractures or fragments may be seen on radiography. The fragments appear larger on MRI due to the cartilaginous component. MRI also shows bone marrow edema of the medial patella and disruption of the medial retinaculum and the medial patellofemoral ligament. Stress injuries can occur at the tibial apophysis (Osgood– Schlatter disease) or at the inferior pole of the patella (Sinding-Larsen–Johansson disease). Jumper’s knee is an injury of the patellar tendon near its origin from the patella. Osgood–Schlatter disease is a clinical diagnosis. Irregularity of the tibial apophysis is common and normal. Asymmetric overlying soft tissue swelling may suggest the diagnosis. On MRI, edema may be seen within adjacent soft tissues and or within the tibial apophysis. Rarely, a retro-patellar tendon bursa may form. Acute avulsion fractures of the tibial apophysis are rare. Patellar sleeve fractures are avulsions of the patellar tendon from lower pole of the patella with a sleeve of patellar cartilage/bone. Similar fracture rarely occurs at the upper pole of the patella. Osteochondral lesions (osteochondritis dissecans, OCD) of the femoral condyles are common in adolescent athletes. The lateral aspect of the medial femoral condyle anteriorly is the most common location. On radiography, a

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Fig. 8  Juvenile Tillaux fracture in a 14-year-old boy. The fracture courses transverse through the lateral aspect of the distal tibial physis and sagittal through the distal tibial epiphysis. Slight separation of the fracture fragments is seen at the articular surface

lenticular lucency is seen at the articular surface. MRI can be performed to evaluate the integrity of cartilage overlying the lesion. Cartilage defects, fluid between the lesion and underlying bone and small cysts are suggestive of instability of the fragment. The assessment of stability is less accurate in younger adolescents than adults [27]. Normal developmental irregularity of the posterior aspect of the femoral condyles may appear similar to OCD and must be differentiated [28]. Developmental irregularity is seen in younger patients, is not associated with symptoms, has no associated bone marrow edema and has intact overlying cartilage. Juvenile OCD is defined by the presence of open physes. Juvenile OCD has been hypothesized to represent a stress injury of the epiphyseal physis with possible difference in etiology than adult OCD [29]. Bipartite patella is a common normal variant. Symptoms may occur in bipartite patella due to stress at the synchondrosis between the accessory superolateral ossification center and body of the patella. On MRI, bone marrow edema is indicative of stress or injury.

Ankle and foot The juvenile Tillaux and triplane fractures are called “transitional fractures” as they occur in patients who are skeletal maturity in whom the distal tibial physis is partially fused. The fractures course through the unfused portion of the physis at the anterolateral aspect of the distal tibia. The juvenile Tillaux fracture is a Salter III fracture (Fig. 8). The anterior talofibular ligament (ATFL) attaches to the epiphyseal fracture fragment. The triplane fracture

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is characterized by sagittal epiphyseal, transverse physeal and coronal metaphyseal fracture lines. CT is utilized to confirm a fracture and to delineate the fracture anatomy for planning of surgery [30]. An articular surface gap of 2 mm or greater is an indicative of the need for operative fixation. The aim of treatment is minimizing subsequent premature degenerative disease as a consequence of articular offset. Ligamentous injuries at the ankle are common after skeletal maturity. Imaging of these injuries in adolescents is similar to adults. Lisfranc injuries are quite uncommon in children, but rarely do occur. Lisfranc injuries should be sought on imaging and aggressively treated to avoid permanent sequelae. Radiography may show asymmetric widening of the space between the first and second rays of the foot. Disruption of the Lisfranc ligament between the medial cuneiform and the base of the second metatarsal may be demonstrated by MRI. Associated avulsion fractures of the tarsal or metatarsal bones or frank joint disruption may be seen. Injuries of the tendons of the ankle and foot are uncommon in children. Tarsal coalition most frequently presents near the onset of the second decade as the ossification of the bones nears completion and the foot becomes less flexible [31]. Pain may be induced by increased participation in athletic activity at this age. Stress at the coalition causes symptoms. Most coalitions are talocalcaneal and calcaneonavicular, which are approximately equal in incidence. Calcaneonavicular tarsal coalitions are diagnosed by radiography on oblique foot radiographs. Talocalcaneal coalitions may suggested on radiography; however, CT or MRI is performed for diagnosis [32]. MRI will also show edema centered at the site the coalition. Tarsal coalition predisposes patients to ankle sprains, OCD of the talar dome and foot/ankle tendinopathy. An accessory navicular bone may cause symptoms due to stress at its synchondrosis with the underlying navicular bone [33]. Dancers (especially ballet) and athletes may experience posterior ankle impingement repetitive extremes of plantar flexion [33]. Impingement is accentuate by a prominent os trigonum at the posterior aspect of the talus. With impingement, MRI shows edema within the os trigonum, if present, and within adjacent soft tissues. Avulsion fracture of the fifth metacarpal tuberosity is common in adolescents [34]. These are differentiated from true Jones fractures, which approximately 1.5 cm distal to the tuberosity of the fifth metatarsal at the metadiaphyseal junction [34]. Tuberosity fractures have a good prognosis for healing while Jones fractures are more prone to non-union.

Stress fracture As with adults, active adolescents can develop stress fractures with repetitive activity [35]. Distance runners

Fig. 9  Myositis ossificans in a 9-year-old girl. Axial T2 weighted with fat saturation MR image show a high signal mass (arrows) in the deep anterior upper thigh musculature. Abundant perilesional edema is noted

Fig. 10  Myositis ossificans in a 9-year-old girl (not the same patient as Fig. 9). Axial CT image shows peripheral ossification within the mass (arrows). Non-aggressive periosteal new bone is present on the underlying femur

are most commonly affected; however, stress injury may occur with many other sporting activities. Sites common for stress fracture are the tibia, femur, calcaneus, and the metatarsals, especially the second and third [35]. Upper extremity or pelvic stress fractures are uncommon in children. First rib stress fractures may occur due to carrying of heavy school backpacks. With stress fracture, there is sclerosis, cortical thickening and non-aggressive periosteal new bone. With further activity, an ill-defined fracture line may be seen with a band of sclerosis. Extremely rarely, this may progress to a complete fracture. Patients often present prior to radiographic findings with negative

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radiographs, leading to continuation the inciting activity. MRI is often then obtained because symptoms persist and with a delay from the initial presentation and the initial radiographs. It is helpful to obtain repeat radiographs at the time of the MRI.

Myositis ossificans Frank muscle tears are rare in pediatric patients. Myositis ossificans is not infrequent in children. It is a poorly understood response to trauma. Although post-traumatic, a specific preceding traumatic episode is often not recalled. Patients complain of swelling and pain. Initial radiographs may be negative with the possible exception of show soft tissue swelling. On MRI, myositis ossificans is seen as a hyperintense, hyperenhancing mass with substantial adjacent soft tissue edema (Fig. 9) [36]. The appearance often mimics an aggressive soft tissue neoplasm. The correct diagnosis is suggested by intramuscular and preceding trauma. Radiography or CT may show characteristic peripheral ossification within the mass (Fig. 10) [37].

Spine Stress to the growing thoracolumbar spine can result in acute and overuse injuries unique to the pediatric patients. Radiography and CT are most useful for demonstrating vertebral fracture, while MRI is helpful for evaluating paraspinal musculature, spinal ligaments, intervertebral disks, and the spinal cord [38]. Fortunately, acute spine injuries from sports are rare, but constitute up to one-fourth of all acute cervical spine injuries in children. Most injuries are reported form highrisk sports including American football, diving, skiing, gymnastics and trampolining [39, 40]. Any level in the cervical spine can be affected, but most spinal injuries occurring below the age of 12 years involve C1 and C2 at the atlanto-axial or atlanto-occipital joints. Up to 2 mm of “pseudosubluxation” at the C2–3 and C3–4 levels may be seen as a physiologic variant in normal children and should not be mistaken for injury. Sports injuries of the cervical spine are most common in adolescent boys and are usually isolated injuries with a relatively low injury severity score. With approximately 75 % of these cervical spine injuries, no radiographic abnormality is detected (spinal cord injury without radiographic abnormality, SCIWORA); however, MRI demonstrates spinal cord edema and/or hemorrhage. MRI is also helpful in demonstrating occult ligamentous injury. Supervised flexion and extension may be performed to assess cervical spine stability in this situation.

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Fig. 11  Schmorl nodes in a 7-year-old female skier, presenting with lower back pain. Lateral radiograph showing a defect (arrow) in the upper end plate of the fourth lumbar vertebrae, anteriorly, and reduced disk height at level L3/L4. Similar findings are seen at T12 (arrowhead)

Intervertebral disk herniation is extremely rare in prepubertal children, but is increasingly demonstrated in adolescents participating in competitive sports. The L4–5 and L5–S1 are the most commonly affected spinal levels. Disk herniation is often associated with fracture of the adjacent vertebral ring apophyses. Radiographs are usually normal. On MRI, a focal protrusion of the disk is seen with displacement of the longitudinal ligament, reflective of focal rupture of the annulus fibrosus. Schmorl nodes represent

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Fig. 12  Early Scheuermann disease in a 10-year-old male gymnast, presenting with back pain and increased thoracic kyphosis. Lateral radiograph (a) shows anterior wedging and irregular endplates of thoracic vertebrae T4 to T9. Sagittal T2-weighted (b) and T1-weighted (c) MR images show additional marrow edema adjacent to the vertebral endplates. The findings are suggestive of Scheuermann disease, early stage

herniation of the nucleus pulposus through the vertebral end plate (Fig. 11). Schmorl nodes are common in the lower thoracic and upper lumbar spine of adolescents, and can be accompanied by pain. They may also be seen in association with Scheuermann disease (juvenile kyphosis). When nucleus pulposus herniates between the vertebral body and the ring apophysis, the label “anterior transosseous escape” is applied. This phenomenon is noted in adolescents and may represent failure of fusion of the ring apophysis (limbus vertebrae). Scheuermann disease of the spine is defined as kyphosis of the thoracic and upper lumbar spine with at least three adjacent wedge shaped vertebrae (each with anterior wedging of greater than 5º). Scheuermann disease is most commonly seen in adolescents, and particularly in gymnasts, rowers and weightlifters. The true natural history of Scheuermann disease is not well established; however, excessive physical stress near the time of end plate maturation may be the cause. Wedge shaped vertebrae are seen, often associated irregular end plates, Schmorl nodes and adjacent narrowed disk spaces (Fig. 12). When there are isolated changes confined to the lumbosacral spine it should not termed Scheuermann disease, but merely described.

Fig. 13  Spondylolysis and spondylolisthesis in a 12-year-old male football player, presenting with low back pain. Lateral radiograph shows a linear defect in the pars interarticularis (arrow) consistent with spondylolysis at L5, with grade I anterior spondylolisthesis of L5 on S1. When a pars defect is identified radiographically, further imaging usually is not needed

Spondylolysis is defined as defect within the pars interarticularis between the superior facet and inferior facet of a vertebra. Spondylolisthesis is defined as displacement of the superior vertebra on the inferior, usually anterior in direction (Fig. 13). Both spondylolysis and spondylolisthesis are thought to be consequent to repetitive or longstanding hyperextension and axial loading during childhood. Spondylolysis is considered to be a stress fatigue fracture. Rarely, it may occur as an acute injury. Spondylolysis increases in prevalence with age through childhood, especially between the ages of 5 and 7 years, to reach a prevalence of 6 % in adults. Typically, the child or adolescent presents with lower back pain with occasional focal tenderness. Gymnastics, dancing, cheerleading, football (especially offensive lineman), weightlifting and running are predisposing activities. Approximately 70 % of cases of spondylolisthesis occur at the L5–S1 level, much less commonly at L4–5, and very rarely above the L3 level. Spondylolysis is usually bilateral, but occasionally unilateral, in which case sclerosis and enlargement of the contralateral pedicle may be seen on radiography or CT. If radiography is negative or inconclusive, a tailored CT or

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MR using “reversed angle” axial images (approximately 45º caudal angulation) will demonstrate the pars defect and show any foraminal encroachment. MR findings may aid in guiding treatment by distinguishing between an acute or healing lesion and an inactive lesion representing a fibrous union.

Conclusion Modern children and adolescents are extremely active in sports. Sports are increasingly competitive and participant children often focus on a single sport or single activity within a sport. As a consequence, athletic children are at increased risk of injuries. Patterns of injury differ from those seen in adults, chiefly due to open physes and immature bone. Familiarity with characteristic injury patterns in children aids in proper diagnosis. Compliance with ethical standards  Conflict of interest  The authors declare that they have no conflict of interest. Ethical standards  This article does not contain any studies with human participants or animals performed by any of the authors.

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