Back Pain in Children and Adolescents

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CHAPTER 21 Back Pain in Children and Adolescents

The prevalence of back pain in children and adolescents is increasing. Although it is assumed that pediatric back pain is rare, more recent studies have shown that more than 50% of children note episodes of back pain by 15 years of age.¹^–⁴ A survey of teenagers revealed that 39% complained of low back pain, but few presented for medical evaluation.⁵ Although the number of children and teens complaining of pain is increasing, children and adolescents who have a distinct diagnosis are decreasing in number. A study by Hensinger⁶ in 1985 found a specific diagnosis in 84% of children presenting for treatment of back pain. In a study 10 years later, a cause for back pain was identified in only 22% of 217 children evaluated with single photon emission computed tomography (SPECT).⁷ The task of the evaluating surgeon is to identify which children are most likely to have an underlying musculoskeletal condition and require a comprehensive evaluation to identify the etiology of their pain.

Studies concur that back pain in young children is worrisome and that a pathologic abnormality can nearly always be identified as the cause of the symptoms. As children reach adolescence, their pain begins to resemble that seen in adults. As the radiologic armamentarium grows, the physician has more choices in the evaluation of these patients, but every child who presents to the physician does not need to undergo every scan available. A complete understanding of the potential causes of back pain enables the physician to evaluate the pediatric patient properly.

History

The initial step in distinguishing which children require symptomatic treatment from children who warrant a complete radiographic evaluation is obtaining a detailed history. The characteristics of the pain are most helpful. Acute pain after trauma is seen with fractures, disc herniations, and apophyseal ring separations. Insidious pain without a clear-cut antecedent event is characteristic of developmental conditions, such as Scheuermann kyphosis, and benign neoplasms. Recurrent pain associated with athletics and relieved by rest leads to suspicion of overuse injuries such as spondylolysis. Unremitting pain, especially if it is worse at night or wakes the child from sleep, is most worrisome because it is seen in malignancies and infection.^7,⁸

The location of pain is very helpful in narrowing down the differential diagnosis. Localized pain may indicate either benign or malignant neoplasms. Lumbar pain may be produced by spondylolysis or spondylolisthesis, whereas pain in the thoracic area may be due to Scheuermann kyphosis. Radiation of pain into the buttocks or legs is seen in herniated discs, apophyseal fractures, and spinal cord or vertebral tumors.

The presence or absence of constitutional symptoms is useful in deciding the potential severity of the underlying condition. Fever in a child with acute back pain points to an infectious or neoplastic etiology. It is important to question the parents about malaise, anorexia, the presence of a rash, or abnormal bruising because back pain can be the presenting complaint in children with leukemia.

Next, a detailed neurologic history must be obtained. Numbness, weakness, decreased ability to walk, and changes in coordination require prompt imaging of the spinal cord. The physician should ask specifically about changes in bowel or bladder function because adolescents are hesitant to admit to these symptoms.

The patient’s age is very helpful in directing the evaluation of back pain. Back pain in children younger than 4 years is usually due to either infection or malignancy. A history of fever, limp, and malaise should be sought, and an immediate diagnostic evaluation should be performed. Children in the 1st decade of life commonly present with discitis and osteomyelitis, and malignant neoplasms, but they also may present with benign conditions such as eosinophilic granuloma.⁸ Patients older than 10 years are most likely to have back pain secondary to trauma or overuse, resulting in spondylolysis, disc herniations, or apophyseal fractures.⁹ Scheuermann kyphosis manifests in adolescence. Teens also rarely present with malignancies, so the physician should always remain cautious while weighing the relative frequency of conditions based on age.

A family history should be taken regarding back pain. Adolescents with ill-defined pain, no constitutional symptoms, no history of excessive athletic activity, no anatomically consistent neurologic complaints, and a positive family history often do not have a musculoskeletal etiology for their pain.^2,⁸ Psychosomatic pain does occur in this age group, but remains a diagnosis of exclusion.

A complete review of systems should be obtained. Back pain associated with menses is rarely orthopaedic in nature. Flank pain may be renal in origin. A more recent study showed that 5% of children presenting to an emergency department for evaluation of back pain had urinary tract infections.¹⁰

Physical Examination

The general appearance of the child should be noted. If the child appears systemically ill, immediate evaluation for infection or malignancy is warranted. Whether or not the child can walk and the characteristics of the child’s gait are important because the inability to walk can be due to infection or spinal cord compromise. Examination of the skin for dysraphic lesions such as hairy patches or deep sinuses and for café au lait spots is required.

Palpation of the spine can identify the location of the pathologic abnormality. The spine should be inspected for sagittal and coronal alignment. The Adams forward bend test identifies patients with scoliosis, but the presence of scoliosis is usually a symptom of underlying pathology, rather than the cause of the pain. Trunk lean and decompensation may indicate benign or malignant neoplasms or irritating lesions such as herniated discs. Stiffness of the spine should be noted. Usually, thoracic kyphosis increases and lumbar lordosis reverses as a child bends forward. In the presence of significant pain, the child does not allow the spine to move and bends the knees to touch the floor rather than flex the spine. Pain with hyperextension of the spine is often seen in patients with spondylolysis. This pain can be exacerbated further by twisting during hyperextension. Lasègue sign is nearly always positive in patients with herniated discs or fractured apophyses. Straight-leg raise is also diminished in patients with tight hamstrings secondary to spondylolisthesis.

A thorough neurologic examination is crucial in the evaluation of a child with back pain. Motor and sensory function and deep tendon reflexes should be tested. Long tract signs such as clonus and the Babinski reflex must be evaluated to rule out spinal cord compression or abnormality. The abdominal reflex is tested by lightly stroking the four quadrants around the umbilicus in the supine child. Although an absent abdominal reflex is not abnormal, an asymmetrical response may indicate spinal cord abnormalities.

Diagnostic Studies

With the information obtained from the history and physical examination, a focused approach to diagnostic studies can be taken (Table 21–1). If the patient is 10 years of age or younger, if the duration of pain is 2 months or longer, if there is night pain, or if there are constitutional symptoms, standard radiographs of the spine should be obtained immediately. If the patient is older, the pain is of short duration, and the physical examination is completely normal, the patient may be observed for a short time. Most patients fall between these two groups, and the extent of the radiographic evaluation should be decided on an individual basis.

TABLE 21–1 Use of Diagnostic Tests

X-ray	History of significant trauma; night pain, fever, or inability to walk; age ≤8 yr; duration of pain >2 mo
Bone scan	Negative plain x-rays with normal neurologic examination; persistent pain; history of athletic overuse
Computed tomography	Positive plain x-ray or bone scan
Magnetic resonance imaging	Abnormal neurologic examination; painful scoliosis in patient <8 yr old; painful left thoracic scoliosis
Laboratory tests	Night pain; fever; age <8 yr; constant pain

Radiographs

Plain radiographs are the best screening examination for a child with back pain.^7,¹¹ Anteroposterior and lateral views of the spine should be obtained without pelvic shielding because the shield hides the sacrum, the sacroiliac joints, and the pelvis. The physician should carefully examine the films for alignment, disc space narrowing, endplate irregularities, and lytic or blastic lesions. Each pedicle should be identified on the anteroposterior view. If a question of a lesion arises, a focused coned-down view taken with the patient supine provides better bony detail.

The lateral film should be reviewed for the presence of spondylolysis or spondylolisthesis. As on the anteroposterior view, if there is a question of lysis on the lateral view, a spot lateral view of the lumbosacral junction better visualizes the pars interarticularis. Oblique views of the lumbosacral spine can also show the lysis.

The identification of scoliosis on screening films of a child with back pain should not lead to the conclusion that the curve is the cause of the pain. Although 33% of adolescents with the diagnosis of scoliosis complain of some back pain, it is usually located over the rib prominence and is rarely a presenting complaint.¹¹ The apex of the curve should be carefully inspected for bony lesions in a child with painful scoliosis.

Bone Scan

If plain radiographs and the neurologic examination are normal, but the patient’s symptoms suggest bony pathology, a triphasic technetium bone scan is recommended. Scintigraphy is a highly sensitive but nonspecific tool to localize bony processes. Infections, most benign and malignant bony lesions, and stress fractures have increased bone turnover, which is visualized as increased tracer uptake on scintigraphic images. Pinhole collimation is helpful in localizing the increased uptake. The study should include the sacroiliac joints and pelvis because pathology in these areas often manifests as back pain.

SPECT combines the physiology of a bone scan with the ability to localize lesions precisely within the vertebra similar to a computed tomography (CT) scan. Increased uptake can be seen in the posterior elements in stress fractures, so SPECT is particularly helpful in diagnosing spondylolysis.¹²^–¹⁵ A study of 100 patients 2 to 18 years old presenting with low back pain found that a negative SPECT scan was most helpful in ruling out an organic cause for back pain of less than 6 weeks’ duration.¹⁶

Computed Tomography

CT provides the best imaging of the vertebral anatomy. It is not used as a screening tool but is useful when a lesion is seen on plain radiography or when bone scintigraphy shows increased uptake. CT can be used to assess the status of the pars interarticularis in patients with spondylolysis. Although bone lesions can be seen on magnetic resonance imaging (MRI), surrounding edema may overestimate the extent of skeletal involvement.

Magnetic Resonance Imaging

MRI is used to image the neural axis in all children who have an abnormal neurologic examination. MRI can identify spinal neoplasms, cord abnormalities such as syringomyelia and tethers, discitis, and herniated discs. Auerbach and colleagues ¹⁶ recommended MRI as the best imaging modality for patients with low back pain of greater than 6 weeks’ duration.

Laboratory Tests

Laboratory tests should be obtained at presentation in all young children with back pain and children with night pain, fever, malaise, or easy bruising. A complete blood count with differential should be obtained. Peripheral smear should be ordered looking for abnormal cell lines consistent with leukemia. The erythrocyte sedimentation rate and C-reactive protein should also routinely be studied because they are elevated in infection and malignancy. Urinalysis should be used to screen for renal conditions.

Differential Diagnosis

Table 21–2 summarizes differential diagnoses based on the child’s age.

TABLE 21–2 Likely Diagnoses Based on Age

Age <5 yr	Tumor, discitis
Age 5-10 yr	Langerhans cell histiocytosis, discitis, tumor or leukemia
Age 10-18 yr	Scheuermann kyphosis, herniated disc or apophysis, spondylolysis, osteoid osteoma, tumor or leukemia

Disc Herniation

Intervertebral disc herniation occasionally occurs in older children and teens. The onset of symptoms is usually related to acute or repetitive trauma.¹⁷ Back pain with radiation into the legs is a complaint in 82% of affected patients.¹⁸ Pain is exacerbated by activity and relieved by rest. As in adults, pain is worsened by sneezing, coughing, or straining.

Physical examination reveals decreased spinal flexibility, with inability to touch the toes. On bending toward the floor, the patient often lists to one side. The straight-leg raise test (Lasègue sign) is positive in 85% of children with herniated discs; objective neurologic findings, such as absent reflexes, motor weakness, and decreased sensation, are less common in children than in adults.¹⁹

Radiographs are generally normal, although if the child is sufficiently symptomatic, films may show an olisthetic scoliosis or trunk lean. There is an increased incidence of concomitant spinal abnormalities in patients with herniated discs. In particular, congenital spinal stenosis is frequently seen. Other findings include transitional vertebrae or spondylolisthesis.²⁰

Disc herniation is seen best on MRI (Fig. 21–1). The involved disc is readily appreciated, and other processes that might produce sciatica, such as epidural abscess and spinal cord tumor, can be ruled out.⁸ Herniation of the disc can be differentiated from an avulsed vertebral apophysis on either MRI or CT scan. Correlation of MRI findings with the history and clinical examination is necessary because mild disc bulging can exist as a normal variant.

FIGURE 21–1 MRI of a 16-year-old girl with back and right leg pain shows herniated L4-5 disc.

Treatment is initially conservative, consisting of anti-inflammatory medication and bed rest. Prolonged nonoperative management may lead to persistent pain, however, so if the patient does not respond to symptomatic treatment, disc excision should be performed.¹⁹ Short-term results are very encouraging, with 95% good and excellent results and nearly universal resolution of back and leg pain.¹⁹ Although long-term follow-up shows deterioration in results, with 24% reoperation after 30 years,²¹ outcome studies show that patients treated by discectomy as adolescents function better than adults after similar surgery.²² Surgical technique for adult and pediatric patients is similar. Some early reports indicate pediatric patients can safely undergo endoscopic percutaneous discectomy.²³

Apophyseal Ring Fracture (Slipped Vertebral Apophysis)

The apophyseal ring fracture, also known as a slipped vertebral apophysis, occurs in adolescents and young adults. The etiology is either acute trauma resulting in rapid flexion and axial compression or cumulative microtrauma. The fracture typically develops at the junction of the posteroinferior vertebral body and the cartilaginous ring apophysis, with posterior displacement of the fragment into the spinal canal.²⁴ CT scan can show the size and location of the bony fragment, with large central fragments being most common and most likely to result in significant pain if left untreated.²⁵

Symptoms mimic a herniated disc, with the sudden onset of severe back pain radiating into the leg. Physical examination shows a positive straight-leg raise test, but as is the case with disc herniations, neurologic signs are infrequently present.

The diagnosis is made radiographically. High-quality lateral radiographs may show an arc-shaped rim of cartilage, cartilage with attached underlying bone, or a small triangular bony fragment lying posterior to the vertebral body. The fragment is best visualized on CT scan.²⁴ The levels most frequently injured are L4 or S1. Treatment is surgical removal of the avulsed fragment.

Vertebral Fractures

Pediatric patients with spinal fractures present with back pain. If the energy of injury is sufficient that fracture is possible, radiographs should be obtained at once. When compression fractures are seen in children without high-energy trauma, an immediate evaluation should be performed for underlying malignancy.

Developmental Disorders

Spondylolysis and Spondylolisthesis

Spondylolysis refers to a stress fracture of the pars interarticularis, occurring predominantly in the lower lumbar spine. The most frequent level is L5, followed by L4. It is extremely rare to have more than one vertebral level involved. Spondylolysis is bilateral in 80% of cases and unilateral in 20%. More recent studies show that 50% of young athletes presenting for evaluation of back pain have injuries to the pars interarticularis.²⁶ The mechanism of injury is repetitive microtrauma in hyperextension, overloading the pars interarticularis, over time leading to stress fracture. Sports linked to a high incidence of spondylolysis are gymnastics, diving, ballet, and football. Gymnasts and football linemen have a fourfold increase in incidence of spondylolysis compared with the general pediatric population.²⁷

Symptoms consist of low back pain that is exacerbated by athletic activity and at least partly relieved by rest. The pain is present in the lower back, but can radiate into the legs.

Physical examination may reveal hamstring tightness and loss of normal lumbar mobility. The ability to bend forward to the floor may be diminished. In hyperflexible patients (i.e., gymnasts and ballerinas), motion may seem normal. The patient is usually tender to palpation of the lumbar spine. Hyperextension usually reproduces the back pain, and axial rotation in hyperextension exacerbates the pain.

Lateral radiographs may show lysis across the pars interarticularis, and oblique radiographs can be helpful in less obvious cases (Fig. 21–2). The appearance of a collar on the “Scottie dog” suggests stress fracture. Often, plain radiographs are nondiagnostic. In these cases, scintigraphy can reveal increased tracer uptake at the involved level. The use of SPECT is particularly helpful in localizing increased uptake in the pars interarticularis (Fig. 21–3).^13,^14,²⁸ A specific scintigraphic pattern, seen as a triangle of increased signal with increased uptake in the pedicles, has been described.²⁹ Positive bone scans and SPECT imaging are generally seen in the prefracture state and in relatively acute injuries.³⁰ The bone scan may not be “hot” in chronic spondylolysis.¹⁴

FIGURE 21–2 Lateral radiograph of lumbar spine shows spondylolysis of L5 in a 16-year-old volleyball player.

FIGURE 21–3 Increased uptake in pars interarticularis of an adolescent ballerina with spondylolysis.

MRI has also been used to diagnose spondylolysis, but false-positive scans can occur.³¹ Better bony definition of the fracture is obtained using CT scans. Additionally, CT is superior to MRI in the assessment of incomplete fractures and in establishing healing in patients with spondylolysis.³² The pars is imaged by using a reverse gantry angle and obtaining thin slices on the CT scan.³³

Spondylolysis and spondylolisthesis can produce scoliosis. Curves resulting from these conditions are usually described as olisthetic, are associated with oblique takeoff of the spine from the pelvis, are small in degree, and have little rotation. Spondylolysis and spondylolisthesis occur in patients with idiopathic scoliosis more frequently than in the general population but are usually asymptomatic.

Treatment of spondylolysis is initially nonoperative and primarily involves modifying the patient’s level of athletic activity.³⁴ Cessation of sport until the resolution of symptoms is combined with a concomitant exercise program to stretch the hamstrings and strengthen the paraspinal and abdominal musculature. Resumption of activities is gradual. The patient’s technique or training should be modified to minimize recurrent fractures. Use of a antilordotic lumbar orthosis increases the success of nonoperative treatment, particularly in patients with acute injuries and “hot” bone scans.^35,³⁶ A more recent study found resolution of symptoms after bracing correlated with initial increased activity on SPECT scans and with decreased uptake on follow-up scans, whereas SPECT scans for patients whose pain did not improve showed no significant decrease in activity after bracing.³⁷

The overall success rate of nonoperative treatment ranges from 73% to 100%.³⁶ A multicenter study of 436 children and adolescents with CT-proven spondylolysis found 95% excellent results and 100% return to sport without surgery after 3 months of cessation of activity with use of a thoracolumbar orthosis.³⁸ Patients who have normal radiographs but are found to have a stress reaction without fracture on further imaging are highly likely to improve (and not progress to radiographic fracture) with conservative treatment.^39,⁴⁰ Surgery is typically reserved for the few patients whose symptoms are refractory to 6 months of conservative measures and whose pain recurs with activity after initial nonoperative success.⁴¹

Spondylolisthesis is a related condition in which anterior slippage of a vertebral body occurs on the more distal vertebra. Most often, it is due to bilateral spondylolysis, with the portion of the vertebra anterior to the pars fracture slipping anteriorly. Dysplastic spondylolisthesis occurs in teens who have an elongated but intact pars interarticularis, which allows for the anterior translation without pars fracture.⁴²

Patients with spondylolisthesis often present with complaints of low back pain. The pain may radiate into the legs. Physical findings mimic findings of spondylolysis, with the addition of a possible palpable step-off at the area of listhesis. In severe spondylolisthesis, the buttocks may appear “heart-shaped.” If there is significant hamstring tightness, gait alterations are seen: The teen appears to be shuffling with posterior pelvic tilt. Patients may have a painful, or olisthetic, scoliosis (Fig. 21–4).

FIGURE 21–4 A, Scoliosis in a 13-year-old boy with low back and leg pain of 6 months’ duration. B, Lateral radiograph shows spondylolisthesis at L5-S1.

Plain radiographs establish the diagnosis. The slip is easily seen on a spot lateral radiograph of the lumbosacral junction, and the severity of the spondylolisthesis can be classified as the percentage of forward translation of L5 on the sacrum. Abnormal kyphosis is also seen as the cephalad vertebra tips forward on the caudal segment. A characteristic finding on the anteroposterior radiograph, the appearance of “Napoleon’s hat,” can be seen as L5 moves forward on the sacrum.

Treatment is initially conservative in mild spondylolisthesis and surgical as the magnitude of the slip increases. Surgical treatment of high-grade spondylolisthesis is recommended, but preferred techniques vary among surgeons, and reduction remains controversial.⁴³ The surgical treatment of spondylolisthesis and spondylolysis is discussed in further detail in Chapter 27.

Scheuermann Kyphosis

Scheuermann kyphosis is a developmental condition that occurs in adolescents and is characterized by increased thoracic kyphosis accompanied by lumbar hyperlordosis. Boys are affected slightly more frequently than girls.

Back pain, which is usually located at the apex of the thoracic kyphosis and may be present in the lower lumbar spine as well, is the presenting symptom. The pain is usually described as aching in nature, does not wake the patient from sleep, and does not radiate. It is exacerbated by vigorous activity and prolonged sitting. The severity of the back pain is variable, with some patients denying significant symptoms and instead presenting for evaluation of poor posture. Neurologic symptoms are highly unusual.

Physical examination of a patient with Scheuermann disease shows increased thoracic kyphosis that is most notable on forward bending, where the apex appears to protrude posteriorly. The deformity is usually fairly rigid and does not disappear with hyperextension. There may be concomitant hamstring tightness, with inability to touch the floor with the fingertips.

The diagnosis is made radiographically (Fig. 21–5). Criteria for the diagnosis of Scheuermann disease have been outlined by Sorenson as (1) three contiguous vertebral bodies with greater than 5 degrees of anterior wedging; (2) abnormal disc narrowing; (3) endplate irregularities; and (4) Schmorl nodes, defined as disc herniations into the vertebral bodies.