Sport injuries in the paediatric and adolescent patient: a growing problem
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With an increasing number of paediatric and adolescent athletes presenting with injuries due to overuse, a greater demand is put on clinicians and radiologists to assess the specific type of injury. Repetitive forces applied to the immature skeleton cause a different type of injury than those seen in adults due to the differences in vulnerability of the musculoskeletal system, especially at the site of the growth cartilage. Intrinsic and extrinsic risk factors all play a role in the development of overuse injuries. MRI plays a key role in imaging overuse injuries due to its high potential for depicting cartilaginous and soft-tissue structures. Sport-specific biomechanics are described, since this knowledge is essential for adequate MRI assessment. An overview of several sport-related injuries is presented, based on anatomical location.
KeywordsSports imaging MRI Trauma Children
In Western societies sport injuries in the paediatric and adolescent population are a clinical entity that is being seen more frequently . Acute sport injuries are often easily recognized as there is a sudden onset of symptoms following a traumatic event, such as a direct force applied to the bones or joints. This can lead to fractures, in which the growth plate can be involved, or dislocations that often can be recognized clinically. There is appropriate awareness and the pattern of injury is known to paediatric and general radiologists. Acute soft-tissue injuries, tendon ruptures or ligamentous injury, are not so familiar and may therefore be more difficult to diagnose.
This paper focuses on overuse injuries, aiming to increase awareness amongst radiologists. Overuse injuries are caused by repetitive microtrauma with biomechanics that are sport-specific. They can lead to functional impairment and if not accurately appreciated and treated can even cause permanent disability. When a minor or trivial trauma causes disproportionate symptoms in an athlete, an overuse type of injury should be ruled out.
Special consideration has to be made for unique injuries occurring in the growing skeleton . Several contributing risk factors have been described . These can be divided into intrinsic factors, such as the increased vulnerability to stress in the growing skeleton and inability to detect injuries, and extrinsic factors, which include the growing pressure from peers, parents and trainers to perform better; also the lack of training and competition programmes adapted to the paediatric and adolescent population can play a role. Especially in the adolescent population, where there is an increasing tendency towards a professional level of sport activity, the incidence of overuse injuries is increasing rapidly . Furthermore, there is an increased awareness amongst doctors of these types of pathology, which leads to a perceived increase in the problem.
For the general and paediatric radiologist who will probably be increasingly confronted with imaging of sport injuries it is important to understand these risk factors. In order to apprehend the types of injury it is important to understand the different biomechanical forces applied to joints and surrounding structures during various sports activities. In this review both clinical and imaging findings in the most common overuse injuries of the upper and lower limbs and spine of the immature athlete are presented with an emphasis on MRI.
Intrinsic risk factors
Bone growth is initiated at the site of the physis and epiphysis. There are two types of epiphysis in the extremities: pressure and traction epiphyses (apophyses). Pressure epiphyses are found at the proximal and distal end of the longitudinal bones. Longitudinal bone growth takes place from the growth plate (physis) between the metaphysis and epiphysis; therefore injuries to the epiphysis and/or physis can result in longitudinal bone growth disturbance . Growth cartilage appears to be more vulnerable to stress than adjacent bone structures and adult cartilage, especially during periods of rapid growth [4, 5]. In children repetitive forces applied to long bones will more likely result in injury to the weaker epiphyseal plate than ligament disruption .
Traction epiphyses (or apophyses) are found at the insertion site of muscles and tendons and play a role in the development of bone shape but not in longitudinal bone growth. As a skeletal muscle and its tendon are more resistant to stress than the apophyseal growth plate, repetitive microtrauma can lead to traction apophysitis, which in turn can lead to an apophyseal avulsion [2, 5].
The growth of the musculotendinous units is secondary to longitudinal bone growth. During growth spurts the lagging muscle and tendon growth can create tightness and inflexibility around joints whilst during sport activity increased stress is applied to both joints and musculotendinous structures. Imbalance can also occur due to uneven flexibility and strength of the surrounding muscle groups. Preexisting misalignments increase the likelihood of such imbalances.
Physiological factors include decreased bone density in amenorrhoeic female athletes, skeletal maturity, muscle bulk of the individual and deconditioning and poor preparation. Finally, psychological factors such as high-risk behaviour in adolescents can play a role in developing sport injuries .
Extrinsic risk factors
The most important extrinsic risk factor is inappropriate training. Training programmes ideally are adjusted to skeletal maturity, decreased flexibility of muscles and tendons and level of condition in every individual. Coaches and trainers should pay extra attention to technique and excessive forces applied to the immature body. Sporting equipment should ideally be optimized for the less well-prepared participant. Attention should be given to the environment, especially the surface on which the activity is to be performed [3, 5]. Another extrinsic risk factor in this young athletic population is thought to be parental pressure .
The upper limb
Overuse injuries to the upper limb are mostly found in throwing athletes and gymnasts who exert great pressure forces on their arms.
Wind-up with minimal stress
Early cocking with abduction and external rotation of the shoulder
Late cocking with great shear forces applied to the glenohumeral joint mainly due to rotator cuff muscle activity
Acceleration with tremendous stress on the elbow joint, with at the same time exertion of great compression and rotational forces on the radiocapitellar joint and traction at the posterior compartment
Follow-through characterized by rapid deceleration with muscle activity aimed at glenohumeral stability and prevention of anterior luxation
Osseous and growth cartilage injuries
A well-known overuse injury in throwing athletes in the physis of the proximal humerus leading is little leaguer’s shoulder. Due to repetitive microtears widening of the physis occurs, shown on conventional radiographs; other findings include demineralization, sclerosis, fragmentation of the lateral aspect of the proximal metaphysis and cystic changes . Sometimes additional radiographs of the contralateral side are necessary. When radiographs are negative, especially in an early phase, MRI can be helpful. Besides widening of the physis there is high-intensity signal in the metaphysis on T2-weighted (T2-W) images and hypointensity on the T1-weighted (T1-W) series representing marrow oedema [9, 10]. Periphyseal oedema and subtle periosteal elevation and oedema have also been described .
Glenohumeral dislocation is relatively uncommon in the paediatric population; however it is the most common site for acute articular dislocation in adolescents. Plain radiographs in AP, axillary and lateral directions should be obtained as fractures of the glenoid (Bankart lesions) and/or posterior impression fractures of the humeral head (Hill-Sachs lesions) can occur. Labral tears and capsular laxity have been described in throwing athletes, and MR arthrography is advised to confirm the diagnosis and plan the surgical repair [7, 12].
Cuff pathology is relatively uncommon in the paediatric and adolescent population, as the epiphyses (at this site the humeral tubercle) is the weakest link of the musculoskeletal chain. MRI is the imaging modality of choice to depict pathology [7, 13].
Osseous and growth cartilage injuries
Lateral epicondylitis (tennis elbow) and medial epicondylitis (golfer’s elbow) are stress reactions at the insertion sites of extensor and flexor muscle tendons due to long-standing repetitive overuse. As the apophysis forms the weakest point in the musculoskeletal chain this type of injury is rare; imaging is seldom necessary and serves mostly to exclude other lesions. Ulnar collateral ligament ruptures are rare in children and adolescents as the ligament is stronger than the attached structures and generally occur after epiphyseal fusion .
Osseous and growth cartilage injuries
In tennis, stress-related injury with bone marrow oedema in the carpal bones is recognised.
In adolescent rock climbers presenting with chronic finger pain and decreased motion, stress reactions such as cortical hypertrophy and subchondral sclerosis, as well as stress fractures of the proximal physeal plate (Salter-Harris type II or III) of the middle phalanx (mostly of digits 3 or 4) have been described, and lead to osteoarthritis [21, 22].
Intraarticular and soft-tissue injuries
Chronic low back pain is a common complaint in the paediatric and adolescent athlete. Especially athletes such as gymnasts and wrestlers, who put excessive axial loading as well as flexion and extension forces on their spine, are at risk .
Spondylolysis is a common finding among young athletes and can occur with or without spondylolisthesis. Spondylolysis is, however, a common finding in the whole population with a prevalence of 6–8%. Thus the exact role of this finding remains an issue of discussion. There are several classification systems for spondylolysis. For children and adolescents the scheme can be as follows: (a) dysplastic, (b) developmental, (c) traumatic and (d) pathological . In the dysplastic type there is an intact pars interarticularis. In the developmental type there is a bony gap and surrounding sclerosis; in this group heredity has been demonstrated. The traumatic type can be divided into an acute and chronic form. In the chronic traumatic form there are three subtypes: stress reaction with only oedema on MRI without a bony gap; a stress fracture in which there is oedema and cortical disruption without a large bony gap; and finally, spondylolysis with a larger bony defect with sclerotic changes on both sides of the pars interarticularis.
Spondylolisthesis can be graded on lateral/sagittal views as ≤50% slippage, which is considered stable, and >50% slippage, which is unstable . Vertebral deformation with wedging and disc protrusion/degeneration appears to be secondary to spondylolisthesis instead of being a contributing factor .
Vertebral ring apophyseal injury occurs mainly in adolescent athletes, as the apophyseal ring appears to be most vulnerable in this age group that is characterized by rapid growth. Controversy exists whether the condition is the result of trauma, overload, or a growth disorder .
Anterior apophyseal injury can be the result of intravertebral disc herniation or due to traction by muscular activity or lumbar hyperextension. As cartilaginous structures are involved, MRI is considered the most sensitive modality .
Posterior ring apophyseal fracture is a rare condition in which neurological deficit can be the reason for surgical intervention. As radiographs can be negative and MRI appears to have low sensitivity, CT is the gold standard to show the fragment avulsed into the spinal canal .
Although the exact aetiology of the disease is unknown, the thoracolumbar form of Scheuermann disease is found more frequently in athletes than in non-athletes. Findings include disc degeneration, reduced disc height, Schmorl nodes and flattening of vertebral bodies with kyphotic deformation, all of which can be seen on plain radiographs .
The lower limb
Chronic or recurrent apophyseal injuries may result in irregular patterns of ossification around the pelvis that can easily be confused with other more aggressive disorders . CT is the method of choice for assessing the benign origin of the lesion. High-intensity activity might be associated with repetitive traction on an apophysis without avulsion. MRI in these athletes who present with pain shows soft tissue and bone marrow oedema. Marrow oedema, demonstrated with high signal intensity on fat-suppressed images, represents a stress response of the cancellous bone due to microfractures of the trabeculae . Stress fractures, located in the sacrum, acetabulum, and femoral neck, as well as pubic osteitis, which is a stress response, may occur in the growing skeleton .
Muscle contusions result from direct blows. A lump may be palpable and MRI might be indicated to exclude a sarcoma by depicting the intramuscular oedema and haemorrhage.
Myotendinous strains are classified as grade I (stretch injury), grade II (partial tear), and grade III (complete rupture). MRI reveals high signal oedema on T2-W and STIR images (Fig. 6), as well as high-signal haemorrhage on T1-W images . Acute tears usually occur in the hamstrings and quadriceps muscles. Dynamic US with active muscle contraction is an accurate test for diagnosing these injuries. Lateral hip pain over the greater trochanter may be due to trochanteric bursitis, apophysitis, or gluteus medius tendinopathy.
Thigh splints represent an overuse injury from continued traction of the vastus and adductor muscles to their attachment resulting in local periostitis. MRI reveals focal intramedullary oedema and periosteal reaction on the medial aspect of the femur .
Chondromalacia is the commonest cause of anterior knee pain in young athletes due to softening of the patellar articular cartilage. Patients usually have a history of pain associated with intense athletic activity requiring repetitive knee flexion. In the later stages plain films may show an ill-defined posterior border of the patella or osseous defects and sclerosis. Radiographs may also reveal coexistence of a bipartite patella. MRI is able to depict early the extent of swelling or thinning of the patellar cartilage .
Sinding-Larsen-Johansson syndrome is a self-limiting condition with calcified tendinopathy in an avulsed distal apophysis of the patellar apex. Osgood-Schlatter syndrome is the corresponding tendinopathy on the ossification centre of the tibial tubercle by the distal patellar tendon. Radiographs in both syndromes show fragmentation of the lower pole of the patella and the tibial tubercle, respectively. MRI usually is not indicated.
Chondral and osteochondral injuries are significantly more prevalent than meniscal or ligamentous injuries in young athletes. Femoral lesions are more frequently encountered in children and patellar lesions in adolescents. MRI findings include cartilaginous thickening in grade I lesions, superficial ulceration or fissuring in grade II, deep ulceration or fissuring in grade III, associated bone bruise in grade IV and separated fractures in grade V. Impaction fractures may also occur (Fig. 12).
Osteochondritis dissecans is thought to result from repetitive trauma to the weight-bearing areas and is usually seen in the lateral aspect of the medial femoral condyle. Radiographs may initially be normal, whereas in the later stages a subarticular lucency, with or without loose bodies, may be demonstrated. Signs on fat-suppressed MR images that suggest instability include: a fragment outlined by fluid; an articular fracture passing through the subchondral bone plate; a focal osteochondral defect filled with joint fluid, and a 5-mm or larger cyst deep to the lesion. The criteria above have high specificity for lesions in adults, but not in juveniles .
Many overuse lesions occur in the foot. Sever’s lesion represents a clinical situation with posterior pain in the heel bone caused by a traction apophysitis. Since fragmentation of the calcaneal apophysis on plain radiographs is seen both in symptomatic and asymptomatic feet, imaging is not helpful. Stress fractures, mostly of the second or third metatarsals, navicular and cuboid bones and of the proximal portion of the fifth metatarsal (Iselin’s disease) are also frequently encountered. The MR imaging appearance of a stress fracture is a low-signal line on T1-W and T2-W images with surrounding oedema .
Osteochondral injuries result from single or repetitive trauma. The term “osteochondral lesion” is preferred to the term “osteochondritis dissecans”. These injuries in the ankle are usually located in the talar dome and should always be suspected in sprains not responding to conservative treatment. MRI is the method of choice for classifying the lesion as stable or unstable  (Fig. 14). In the presence of a joint effusion, cartilaginous loose bodies can be detected (Fig. 14), otherwise MR arthrography may be indicated .
Soft tissue injuries
Acute ligamentous injuries are rarely treated surgically and thus imaging is not usually required. MRI is reserved for when surgical repair is contemplated in elite athletes, in those with a history of chronic instability, and in those with symptoms persisting for more than 6 weeks following injury. Swimmers may show oedema surrounding the extensor tendons and the retinacula on MRI as a result of overuse and intense training (Fig. 14). Acute injuries and chronic mucinous degeneration of the Achilles tendon are rare in the growing skeleton. Subacute or chronic disorders also include the posterior impingement syndrome resulting from an os trigonum and overuse tenosynovitis .
As overuse injuries in the paediatric and adolescent population are increasing in our society and as physicians are also increasingly occupied with this type of injury, it is very important to have a better insight into the aetiology, especially the underlying risk factors and biomechanics of sport activities, as well as a knowledge of the various possibilities of imaging techniques and findings in different injuries. As the types of injury in the immature skeleton differ from those in adults due to differences in the weak points in the musculoskeletal chain, it is important for both paediatric and general radiologists to have knowledge of these differences and the resulting injuries. Although incomplete, we have, in this article, presented the most important risk factors, biomechanics, and imaging findings in overuse injuries of the upper and lower limb and spine. The ongoing evolution and availability of imaging techniques, especially MRI, has led to more possibilities to depict injuries. As misdiagnosed injuries can lead to impairment and possible irreversible damage, an increasing demand is put on clinicians and, consequently, radiologists to assess overuse injury. Imaging can be helpful not only in the primary diagnosis, but to establish indications for invasive treatment and for follow-up.
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