The purpose of this article is to discuss an orthopedic approach to the diagnosis and management of back pain in children.1'2 Some of the more significant causes are described in detail. Acute fractures, with a clear history of injury and seen on a plain radiograph, are excluded.
GENERAL EVALUATION OF THE CHILD WITH BACK PAIN
The child who complains of prolonged or recurrent back pain must be taken seriously. Parents and caretakers should be advised to seek medical attention, particularly when pain awakens the child from sleep, is constant for 3 consecutive days, or is intermittent but recurrent for 3 weeks' duration. For children, whose primary goal in life is play, any pain that prevents this is of concern.
A comprehensive history is necessary. An organic etiology can be found for most cases of childhood back pain, but that etiology may not be an orthopedic condition. Children, especially those younger than 6 years of age, frequently do not localize pain reliably. Sources of pain that is referred to the back include the chest (eg, pneumonia or reflux esophagitis), the abdomen (eg, appendicitis or pancreatitis), the retroperitoneum (eg, pyelonephritis), or the pelvis (eg, ovarian cyst). Childhood leukemia may present with bone pain, including back pain.
As the history becomes focused toward orthopedic concerns, specific questions should be asked to help clarify the differential diagnosis and determine which diagnostic studies should be done. Some responses are so characteristic of specific orthopedic conditions that they offer shortcuts to help make the correct diagnosis. The following questions illustrate this.
What is the duration of the pain? Patients who have had pain for more than 6 months prior to presentation are likely to have less significant pathology or slowly developing, nonmalignant processes. Those who have been symptomatic for less than 6 months are more likely to have a serious disease process such as infection or malignant tumor.
Is the pain aggravated with activity and relieved with rest? Symptoms such as these are frequently associated with the onset of spring or fall training for sports. If the patient is healthy and the pain is related to his or her participation in sports, he or she may have an overuse condition such as spondylolysis or spondylolisthesis.
Does the pain prevent sleep or awaken the child from a sound sleep? Pain that is unrelieved with rest or that keeps the patient awake at night is suggestive of an infectious or neoplastic process.
Does the pain radiate into the buttock or leg, especially below the level of the knee? This is characteristic of radicular pain associated with herniated nucleus pulposus, spondylolisthesis, and osteoid osteoma.
Is the pain relieved with aspirin? Many inflammatory processes are improved with aspirin, but, classically, aspirin produces profound relief of the pain associated with osteoid osteoma.
Are there any systemic symptoms ? Malaise, fever, headache, and lethargy point to infection, inflammation, and neoplastic processes.
What effect does coughing or sneezing have on the pain? Pain aggravated with coughing or sneezing is present with spinal cord tumors and herniated nucleus pulposus.
Is there any sensory change, muscle weakness, or loss of bowel or bladder control? Syringomyelia, spinal cord abnormalities, tumors of the spine compressing the spinal cord or nerve roots, and herniated nucleus pulposus can produce these findings.
As with the history, the physical examination must be comprehensive. Similarly, some specific physical findings are characteristic of disease categories or specific disorders.
The spinal alignment is assessed during resting stance and also while evaluating spinal range of motion. Idiopathic scoliosis is almost never painful in and of itself; however, a scoliotic deformity may be secondary to pain in syringomyelia, tumor, spondylolisthesis, and herniated nucleus pulposus. These same conditions are suggested if the head does not remain in the center line during forward flexion. An accentuated thoracic kyphosis, especially noticeable on forward flexion, suggests Scheuermann's kyphosis.
Spinal range of motion should be unrestricted. The examiner must observe segmental motion of the lumbar spine by watching the relative motion of the subcutaneous prominences of the lumbar spinous processes. A stiff spine is seen on attempted forward flexion in inflammatory processes, infection, and neoplasms. Stiffness on attempted extension is typical of diskitis.
Joint range of motion, especially in the lower extremities, should be measured. Hamstring contracture is characteristically present in spondylolisthesis. Hamstring spasm and restricted hip flexion are seen with diskitis. The neurologic assessment is an important part of the physical examination. Neurologic abnormalities such as gait disturbance, absent sensation, muscle weakness, or reflex changes are associated with spinal cord tumors or extrinsic pressure on nerve roots from spine tumor or herniated nucleus pulposus. Absence of superficial abdominal reflexes may suggest syringomyelia.
In general, the history and physical examination will direct appropriate laboratory tests or imaging studies. Basic, straightforward studies should not be neglected. Plain radiographs should always be reviewed before ordering other advanced studies such as bone scans or magnetic resonance imaging (MRI). Radiographs requested to assess spinal alignment are optimally done on long (36-inch) cassettes using the proper filters for scoliosis technique (see the article by Killian et al. in this issue).
SPONDYLOLYSIS AND SPONDYLOLISTHESIS
The essential lesion that defines spondylolysis of any vertebra is a defect in the pars interarticularis. This occurs most commonly in the lower lumbar spine, with L5 being the vertebra most often affected. The lesion is not congenital, and has not been described in fetal specimens. Although acute traumatic pars interarticularis fracture is possible, the overwhelming majority of these lesions in children are thought to be repetitive stress injuries that progress to frank stress fracture. Prevalence rates are highest in activities that require repetitive hyperextension of the spine, such as gymnastics and diving.
Spondylolysis and spondylolisthesis may occur without symptoms, or symptoms may be so mild that medical attention is never sought. However, the condition is a common and a frequent cause of juvenile back pain, with patients sometimes presenting as young as 2 or 3 years of age.
In children, spondylolysis and spondylolisthesis are discussed as related disorders because, in this age group, most spondylolisthesis is secondary to a spondylolytic defect in the pars interarticularis.3,4 In pure spondylolysis, there is no change in the spatial relationship between the vertebra with the defect and the vertebra below. In spondylolisthesis, there is a forward displacement, or slip, of the affected vertebra.
There are other types of bony defects that may cause spondylosisthesis in children. "Dysplastic" spondylolisthesis consists of a congenital absence or deficiency of the facet joints. "Isthmic" spondylolisthesis refers to traumatic or repetitive stress lysis of the pars interarticularis as described above, and also includes the abnormally elongated pars. All of these conditions occur most commonly at the L5 to Sl level. The prevalence of spondylolisthesis and spondylolysis, after reaching skeletal maturity, is 6%. The prevalence is higher in boys, but the risk of progression of listhesis is higher in girls.
Spondylolisthesis is classified according to the amount of vertebral displacement or angulation that occurs. The most commonly used system considers four grades of forward translation, determined as a percentage of the width of the normal vertebra below. In a grade 1 slip, the superior vertebra has translated forward no more than 25% of the width of the inferior vertebra (Fig. 1). In a grade 2 slip, there is a 25% to 50% translation. In grade 3 and grade 4 slips, there is a 50% to 75% and a 75% to 100% translation, respectively. Spondyloptosis occurs when the translation exceeds 100% and the superior vertebra has translated beyond the anterior border of the inferior vertebra.
Although spondylolisthesis may be asymptomatic, it is a common and relatively frequent source of back pain. In children, the onset of symptoms occurs most often between the ages of 10 and 15. The degree of slipping may not always correlate with the severity of pain, but increased pain is generally associated with higher degrees of slip. The pain is generally localized to the low back, with referred pain to the iliac crests, buttocks, or groin. True radicular pain in the lower extremities occurs only with significant listhesis.
Figure 1 . Grade 1 isthmic spondylolisthesis (arrows) in a 1 5year-old boy.
Physical findings correlate directly with the degree of slipping. In low-grade slips, the results on examination may be completely normal. There is usually some hamstring tightness and a decrease in forward flexion of the spine. Hyperextension of the spine aggravates the symptoms. With an increase in the slipping, there is a shortening of the waistline, a flattening of the buttocks, and a palpable step-off of the spinous processes at the affected level. The flattening of the buttocks is due to the local kyphosis across the defect, which decreases the ability to extend the hips and is responsible for the short stride, hip flexion gait known as the Phalen-Dickson sign. The straight leg raising test may produce back pain and sciatic symptoms into the leg or may be limited by severe hamstring spasm. Hard neurologic findings of muscle weakness, sphincter dysfunction, and reflex changes are uncommon, but can be found in high-grade dysplastic slips. There is frequently an associated scoliosis. With increasing pain, the scoliosis may appear "decompensated," with the patient unable to center his or her head over the midline. In cases with severe slipping, the ribs approach the iliac crest and a transverse abdominal crease is present.
Figure 2. Positive results on bone scan bilaterally at an L5 spondylolisthesis (arrow) in a 1 6-year-old boy.
Initial radiographic evaluation should include anteroposterior, lateral, and oblique radiographs of the lumbar spine. A standing lateral L5 to Sl spot film helps visualize the percentage of slip, especially in an obese patient. The pars defects may be visualized most directly on the oblique views.
Spondylolysis is frequently suspected but not visualized on the initial plain radiographs. Because most spondylolytic defects begin as repetitive stress injuries and progress as stress fractures, the diagnostic study to be ordered next is the technetium bone scan (Fig. 2). Single photon emission computed tomography (CT) bone scan should be requested when possible because detection and localization are more sensitive than with the standard bone scan technique. Areas of increased tracer uptake can be further investigated by a standard CT scan as indicated. MRI is seldom indicated to establish the diagnosis.
In most cases of spondylolysis, conservative treatment, with rest and activity modification, is successful. A spinal orthosis or a body cast can be used when additional restriction of movement is needed to control pain. Healing of the defect can occur in some cases with early intervention, especially in those with increased tracer activity on bone scan. However, it is important to realize that relief of pain is usually the primary treatment goal rather than bone healing. Direct bony union is unlikely in those patients who have a "cold" bone scan. If the patient has repetitive episodes of pain with a persistent defect, long periods of immobilization are not necessary. In these cases, the patient should be immobilized only until the pain is under control. Operative intervention is indicated for disabling pain that recurs after an adequate trial of immobilization.
Low grades of spondylolisthesis can initially be treated conservatively with rest and activity modification, followed by casting or bracing if necessary. It is unlikely that an established pars defect will heal once significant slipping has occurred. Younger children need to be observed for progressive slipping with physical examinations and spot lateral radiographs at 6-month intervals until skeletally mature. Many cases are managed conservatively into adult life. Patients with progressive slipping, especially higher than grade 2, and those with intractable pain require surgical stabilization by spinal arthrodesis.
In adolescents, spondylolisthesis of higher than grade 2 has a high rate of progression and requires a posterolateral arthrodesis. The most common procedure is fusion without instrumentation, followed by postoperative immobilization in a body cast with the hips in extension to decrease lumbosacral kyphosis. It takes approximately 3 months for the arthrodesis to heal solidly. Posterolateral fusion with instrumentation is another treatment for the older adolescent or adult who does not want to spend the postoperative period in bed. Instrumented fusion with reduction of the slip grade has been associated with higher rates of neurologic complications.
It has not been possible to predict when spondylolysis will progress to spondylolisthesis, nor has it been possible to predict further progression of an existing listhesis. Although the initial lysis is related to athletic activity, additional athletic performance does not predict progression of a slip. Specifically, there is no basis for limiting or restricting the athletic pursuits of the patient who has spondylolysis or nonprogressive spondylolisthesis as long as that patient is asymptomatic and has normal results on neurologic examination.
Scheuermann's kyphosis is a frequent cause of back pain in the adolescent. Kyphosis describes the normal sagittal plane contour of the thoracic spine. In Scheuermann's disorder, the kyphosis is abnormally increased, lacks expected flexibility, and may be located in a part of the spine that should not ordinarily be kyphotic.
There are two types of Scheuermann's kyphosis. The first is the classic form, where the apex of the kyphosis is in the thoracic region. Radiographic changes required to define the diagnosis include end plate irregularities and significant wedging of at least three contiguous vertebral bodies (Fig. 3). The etiology is unknown, although there may be a mechanical component. Historically, this type of Scheuermann's kyphosis has been associated with heavy lifting in skeletally immature individuals. The second type is lumbar Scheuermann's kyphosis, where the apex of the deformity is located in the lumbar spine. The bony changes are present, but vertebral wedging is less severe and may be localized to a single level. This type may be confused with diskitis, or may represent a residual deformity from subclinical diskitis.
These patients present with a kyphotic deformity, with or without associated pain.5,6 Parents frequently state that their child has poor posture and does not stand up straight despite repeated requests. Pain is usually located at the apex of the kyphotic thoracic curve, but may also be located at the secondary hyperlordotic lumbar curve. The more caudad the apex, the higher the incidence and greater the intensity of pain. Symptoms seem to be most severe during periods of accelerated growth. Radicular pain and neurologic symptoms are distinctly uncommon.
The physical examination discloses an increase in the expected thoracic kyphosis, and the alignment does not improve when the patient is instructed to stand erect. The deformity is accentuated with forward bending. A prone hyperextension test gives a clinical evaluation of spinal flexibility: while lying prone with arms at side, the patient is instructed to raise his or her head and shoulders off the table and look at the ceiling. Flexibility of the kyphosis is observed directly during this maneuver.
Figure 3. Classic Scheuermann's kyphosis in a 15-year-old boy. Arrows indicate the four contiguous vertebral bodies that are involved.
Anteroposterior and lateral standing radiographs of the spine should be taken to evaluate the curve magnitude, and a lateral supine hyperextension lateral radiograph should be taken to evaluate the degree of flexibility. Curve magnitudes should be measured using the Cobb angle. Structural and postural factors influence the appearance of the lateral radiograph of the spine. Postural factors should be eliminated by properly positioning the patient for the lateral radiograph. Radiographic findings include vertebral wedging, Schmorl's nodules, end plate irregularities, disc space narrowing, and occasional anterior bony bridging as in congenital kyphosis.
Spondylolisthesis and scoliosis are commonly associated. The scoliosis is usually less than 20° and does not require treatment. Turner's syndrome, juvenile osteoporosis, and the use of phenytoin may have radiologic and clinical manifestations that simulate Scheuermann's kyphosis.
Treatment is based on skeletal maturity, magnitude of the kyphosis, flexibility, and the presence of pain. Exercises do not correct the kyphosis and will not correct the vertebral wedging. However, exercises may strengthen the spine extensors to help with pain relief.
An orthosis may be considered in the skeletalIy immature patient with or without back pain. Indications include a kyphosis greater than 45° but less than 70°, which decreases to less than 45° on hyperextension. The two types of orthoses used are the cervical thoracolumbosacral orthosis (CTLSO) and the thoracolumbosacral orthosis (TLSO). The Milwaukee brace is the most common CTLSO. Studies have shown it to be successful in producing a permanent reduction of the kyphotic deformity. However, to be effective, the brace must be worn for 1 to 2 years. Many patients do not like the cervical component with the metal supports. Patients seem to prefer the TLSO, which can be worn under clothing and does not have a noticeable cervical component. Orthotic management is contraindicated in patients who are obese, are skeletally mature, and have a rigid curve greater than 45°.
Indications for surgical treatment include skeletal maturity, curves greater than 60° to 70°, progressive deformity, pain, and an unacceptable cosmetic appearance. A posterior spinal fusion with instrumentation can be done when the kyphosis corrects to less than 60° on the hyperextension lateral radiograph. Postoperative curve correction will usually decrease the curve magnitude 10° to 20° below that obtained on the hyperextension lateral radiograph. A combined anterior release and fusion with posterior instrumentation and fusion is necessary when the kyphosis is not less than 60° on the hyperextension lateral radiograph.
The natural history of untreated Scheuermann's kyphosis is not well defined. Risk factors for progression are unknown. Kyphosis actually increases the chest capacity, so there is no restriction of heart or lung function. Many patients remain asymptomatic throughout life. However, increasing deformity is associated with increasing symptoms of pain, and there is a small but real risk of myelopathy with increasing kyphosis.
INTERVERTEBRAL DISC HERNIATION
The central portion of the intervertebral disc consists of nucleus pulposus and the peripheral portion is the annulus fibrosus. The disc material in children is more mucoid and generally better hydrated than in adults. The annulus fibrosis is densely adherent to the margins of the adjacent vertebral end plates, and in children this end plate is composed of growth cartilage. Intervertebral disc disorders constitute a spectrum of mechanical failure of this complex. These include bulging of a weakened annulus fibrosus, herniation of the central nucleus pulposus through a torn annulus, and fractures of the cartilaginous end plate at the point of annulus attachment. Local and locally referred back pain may arise directly from the damaged disc complex. However, most significant symptoms are caused by posterior displacement of these structures into the spinal canal, causing pressure on the thecal sac and the nerve root that exits at the foramen below the involved disc.7"9
Although surgical treatment is common in adults, only 0.5% of discectomies are performed on children younger than 16 years of age. The mean age at the onset of symptoms is 14 ± 7 years and the mean age at surgery is 15 ± 1 years. There is a history of trauma in 36%. This is commonly associated with sports, a fall from a height greater than 1 m, and motor vehicle accidents. Approximately 2% of disc herniations occur at the L3-L4 disc. The remaining 98% are equally distributed between the L4-L5 and the L5-S1 discs. The most common symptom is sciatica, present in 92% of patients. Back pain with sciatica is found in 58% of patients, but back pain as the only presenting symptom is rare and is found in only 2%. Some studies suggest that these patients are taller and heavier than average.
When the patient stands and is viewed from the back, there is a sciatic scoliosis, in which the patient lists to one side and finds it painful to keep his or her head over the center line. There may be a rigid lumbar lordosis that does not reverse with attempts at forward flexion. There is increasing leg pain with attempts at forward flexion, causing the patient to list farther from the midline. Pressure over the sciatic nerve in die buttock may aggravate the leg pain. Paraspinous muscle spasm can be palpated, especially in the lumbar area.
Absent Achilles reflex and weak ankle flexors, with sensory loss on the lateral border and plantar surface of the foot, are found in an Sl radiculopathy. Absent medial hamstring reflex and weak ankle dorsiflexors, with sensory loss on the dorsal medial aspect of the foot, are found in an L5 radiculopathy. Absent patellar tendon reflex and quadriceps weakness, with sensory loss over the anterior knee, are found in an L4 radiculopathy. Muscle weakness, although present, may be difficult to appreciate on manual resistance testing.
The most common weakness can be detected by repetitive heel and toe raises, or with heel and toe walking. Weakness with heel walking infers an L5 nerve root involvement, and weakness with toe walking infers an Sl nerve root involvement. The most commonly performed straight leg raising tests help evaluate the L5 and Sl nerve roots. A supine straight leg raising test is done by passively raising the leg, flexing the hip with the knee fully extended. The result of supine straight leg raising is positive when the sciatic component of the pain is aggravated. After maximum hip flexion on the straight leg raising test, the sciatica can be further aggravated by dorsiflexing the ankle or applying pressure in the popliteal fossa. The contralateral straight leg raising test is performed in a similar fashion using the opposite extremity. The result is positive when the contralateral leg raising maneuver aggravates pain in the leg not being raised. The most sensitive test for detecting nerve root involvement is a sitting modification of the straight leg raising test. While the patient is sitting, the knee is extended and the ankle is dorsiflexed. When the leg pain starts to become aggravated, the patient will start to lean backward to decrease it. The patient is then asked to flex his or her neck and try to put his or her chin on his or her chest. If the leg pain is increased with neck flexion and decreased with neck extension, the patient has nerve root impingement.
When the L4 root is involved, radicular pain may be more anterior. To evaluate the L4 root with anterior thigh or leg symptoms, the reverse straight leg raising test is helpful. This is performed with the patient prone and the knee flexed. Raising the limb by extending the hip may then reproduce symptoms.
Figure 4. Magnetic resonance imaging shows a herniated nucleus pulposus at the L4-L5 disc (arrow) in a 12-year-old boy.
Plain radiographs are indicated for a complete initial evaluation, but results are frequently normal. Disc space narrowing with degenerative changes on plain films are seen in adults, but not in children. MRI gives a clear picture of the disc-nerve root relationship (Fig. 4), but it often does not reflect the patient's clinical condition. MRI only helps localize disc pathology: MRI findings alone should not be used as an indication for surgical treatment. Radiographic reports use the term "bulging disc" to describe a protrusion of the annulus fibrosus that may not impinge significantly on the thecal sac or nerve root. The term "herniated disc" means the annulus has protruded to the point that there is significant impingement on the thecal sac, the nerve root, or both. There is a high incidence of positive findings that do not correlate with the patient's physical examination.
When MRI shows multiple levels of involvement, it becomes difficult to determine which disc may be causing clinical sciatica. When MRI does not correlate with the clinical presentation or when multiple level disc pathology is present, a CT myelogram is helpful for those patients who have surgical indications. Identification of the correct level and side when removing a disc is extremely important. An intraoperative anteroposterior radiograph, taken with a marker, should be in the same plane as anteroposterior radiographs taken for the myelogram. This optimizes surgical accuracy.
Patients who have back pain, referred pain into the lower extremity, and disc abnormalities on MRI but no physical findings of nerve root impingement (eg, weakness, sensory loss, or abnormal reflexes) should be treated nonoperatively. This consists of bed rest with hip and knee flexion, non-narcotic analgesics, muscle relaxants, extension exercises, and, occasionally, a lumbosacral orthosis. Indications for surgery include a history and symptoms consistent with the diagnosis, physical findings of sciatica with associated nerve root neurologic deficits, MRI or myélographie findings consistent with the nerve root clinically involved, and a failure to respond to nonoperative treatment. Patients with acute loss of bowel or bladder function or acute multiple nerve root dysfunction should be considered surgical emergencies.
The disc is removed by elevating the paraspinous muscles to expose the inferior and the superior lamina of the vertebrae at the appropriate disc level. Portions of the superior and the inferior laminae are removed, along with the ligamentum flavum, to visualize the nerve root. The nerve root is retracted medially to expose the disc herniation. The annulus is incised, or a portion of it is excised, and sufficient nucleus pulposus is removed so that no pressure remains on the nerve root. If the cartilagenous vertebral end plate is fractured or prominent from traction of the distended annulus, that portion may be removed. Frankly extruded disc material is not as common in children as in adults. Patients frequently notice relief or improvement in the recovery room, and symptoms may continue to improve for several weeks or months.
Syringomyelia refers to a cystic, fluid-filled cavity that occurs in the center of the spinal canal.10,11 It has several etiologies. A syrinx may occur posttraumatically after spinal cord injury. It is found in association with an Arnold-Chiari malformation and other conditions that cause obstruction of cerebrospinal fluid flow through the central portion of the cord. The cystic cavity may vary from extremely small to large cavities extending multiple levels throughout the spinal cord and occupying more than half to one-third the diameter of the cord.
Back pain may be the presenting complaint.
There may also be subtle neurologic changes such as decreased temperature sensation, cavus feet, and abnormal reflexes. Superficial abdomen reflexes are frequently affected. These are elicited by stroking each of the abdominal quadrants and watching the umbilicus move toward that quadrant with reflex muscle contracture. However, many patients have few symptoms and instead present with scoliosis. The scoliosis of syringomyelia is frequently progressive, and may be associated with neuromuscular deterioration.
Standard radiographs frequently reveal a scoliosis. This may mimic the curve patterns of idiopathic scoliosis, but when nonstandard patterns (eg, an apex-left thoracic curve) are seen, there must be an increased index of suspicion. MRI is the best way to detect a syrinx (Fig. 5). Indications for MRI include children younger than age 10 with scoliosis, a left thoracic curve (especially in a male), progressive scoliosis unresponsive to orthotic management, presence of neurologic abnormalities such as abnormal abdominal reflexes, and curves greater than 40° requiring surgical stabilization.
Treatment of the syrinx depends on size and etiology, and neurosurgical consultation is mandatory, in the author's opinion, as part of this management. A small syrinx may be observed for progression with serial MRIs. If an Arnold-Chiari malformation is present and the syrinx occupies one-third or more of the spinal cord, a decompression of the foramen magnum may decrease blockage of cerebrospinal fluid flow and reduce the size of the syrinx. If there is no associated Arnold-Chiari malformation, a syringo-pleural or syringo-peritoneal shunt may be indicated. The outcome of orthotic management of the associated scoliosis is unpredictable. Progressive scoliosis requires spinal stabilization with instrumentation and arthrodesis.
DISC SPACE INFECTION
Disc space infections in children seem to be attenuated bacterial infections,12 although they frequently behave more like a noninfectious inflammatory process. The infection is thought to begin near the end plate of one vertebral body, forming an abscess that breaks into the adjacent disc.
The mean age at diagnosis is 7.5 years (range 11 months to 16 years). Frequently, an antecedent history of minor trauma or of upper respiratory or ear infection is noted. Most patients have a low-grade fever, irritability, and general malaise. Only an occasional such patient has a high fever and appears acutely ill. Localization of symptoms can be variable. Younger patients especially may present with walking difficulty. Another group will present with primary abdominal symptoms. Those children who present with back pain may be divided according to age: the younger ones have a different and generally more benign clinical course compared with the older ones with back pain.
Physical examination typically reveals a rigid lumbar spine with increased lordosis, loss of motion, and loss of lumbosacral curve reversal on forward flexion. Pain is elicited or aggravated with percussion over the spinous processes of the involved disc. The patient has pain when attempting to lift the leg off the examination table in the supine position. The hip examination may be painful, especially when both hips are flexed simultaneously, as when performing a bilateral straight leg raising maneuver. This transmits a forward flexion force onto the lumbar spine that aggravates the patient's pain. Patients with abdominal pain on presentation paradoxically have negative results on abdominal examinations. Pressure on the abdomen that flexes the lumbar spine will, however, produce pain in the back. There may be hamstring spasm.
The average temperature at presentation is 37.6°C. The peripheral white blood cell (WBC) count is generally normal or mildly elevated (ie, from 4,600 to 14,900). C-reactive protein levels rise early in the clinical course, and the erythrocyte sedimentation rate is significantly elevated in most patients. Results on blood cultures may be positive, especially if the specimen is drawn when the symptoms are relatively acute. If Staphylococcus is the offending organism, the teichoic acid antibody titer may be elevated.
Figure 5. Large and small syringomyelias (large arrows) and associated Arnold-Chiari malformation (small arrow) in a 12year-old girl.
Results of radiographs performed early in the course are frequently normal, but may show vertebral end plate erosion. The result on bone scan is positive early and can help localize the disc involved. MRI gives the best picture of the pathology once it has been localized. As time passes, the radiograph shows disc space narrowing with gradual erosion of one or both adjacent vertebral end plates. In the late phase, the disc space partially reconstitutes itself but remains narrowed and irregular. There may be a permanent mild kyphosis at the involved disc level.
Historically, patients have responded to bed rest, bracing, or body jacket casting alone. It is now recognized that Staphylococcus aureus is the offending organism in the majority of cases, and antistaphylococcal antibiotic therapy (oral or parenteral) should be added empirically to the treatment regimen. In most instances, symptoms improve within 2 to 3 days. Antibiotics can then be continued until pain has resolved, and as guided by C-reactive protein or erythrocyte sedimentation rate tests. Needle or open biopsy is seldom necessary. Biopsy may be indicated when there is a poor response to treatment, when the patient becomes systemically ill, or in geographic locations where tuberculosis, fungal infections, or other unusual infections are found.
Intervertebral disc calcification is rare in children.13'14 The exact etiology is unknown, but clinical behavior suggests a nonspecific inflammatory process. The condition is more common in boys by a ratio of 2:1. The average age at diagnosis is 7 years. There is a preceding history of trauma in 30% of patients, and 15% have had an upper respiratory tract infection. Disc calcification is most frequently found in the cervical spine in children, but has been reported at all levels throughout the thoracic and lumbar spine. Cervical disc involvement is associated with a more severe clinical picture.
The patient typically presents with torticollis, frequently associated with neck or spine pain that is local or referred. The range of motion of the spine is decreased and there is localized tenderness. There may be shoulder pain with spasm of the deltoid and trapezius. Signs of inflammation are frequently present (eg, elevated temperature, erythrocyte sedimentation rate, and C-reactive protein levels, and peripheral WBC count less than 20,000). Symptoms usually subside spontaneously within a few weeks to 6 months, but may occasionally persist longer.
Calcified discs are often incidental radiographic findings, so their presence is not diagnostic of this condition. They are found most frequently in the lower cervical spine. More than one disc may be involved. The calcification is usually in the nucleus pulposus, but can herniate in any direction. The calcification appears within a few days to a few weeks after the onset of symptoms. When symptoms subside, calcification usually decreases slowly. This regression may occur through absorption by blood vessels within the disc in the skeletally immature patient. Persistent flattening of an adjacent vertebral body may be present in adult life, and early degenerative changes may occur. A few rare associated conditions have been reported. These include congenital heart disease, dysphagia, bilateral cataracts, chalasia, and an episode of transverse myelitis that resolved spontaneously.
Treatment is conservative, with the use of antiinflammatory medications, analgesics, cervical traction, and cervical collar. Rarely, a disc may prolapse, producing a neurologic deficit that requires surgical decompression.
SACROILIAC I0INT INFECTION
Sacroiliac joint infections are uncommon but often difficult to diagnose in children.15"17 The child may present with a wide gamut of findings such as inability to walk or an antalgic gait. Pain can present in a variety of confusing referred locations such as the hip, gluteal region, abdomen, rectum, and back. The pain is usually significant because the sacroiliac joint, having such a small volume, does not need much effusion to produce symptoms. There is frequently an associated osteomyelitis of the adjacent ileum. This may spontaneously decompress anteriorly to become an iliopsoas abscess.
Physical examination is especially important in making this diagnosis. There is tenderness directly over the sacroiliac joint. The pelvic ring compression test, performed by pushing down and outward on the anterior superior iliac spine area of the pelvis, will elicit pain at the sacroiliac joint. The flexion abduction external rotation test, done on the ipsilateral hip, will also produce pain at the sacroiliac joint.
Results on plain radiographs are usually normal. Delay in diagnosis is usual, and in such cases there may be erosions of the sacroiliac joint or osteomyelitic changes in the adjacent ileum. The definitive radiologic study is a total body three-phase bone scan. This will localize the process to the sacroiliac joint. A CT scan is helpful to determine whether there is evidence of osteomyelitis of the ileum. The CT scan can also be used to position a needle in the sacroiliac joint or adjacent ileum to obtain culture specimens. Without CT guidance, the sacroiliac joint can be difficult to aspirate because there is little fluid within the joint.
The most common offending organism is Staphylococcus aureus, although Streptococcus and Salmonella species are other considerations. The patient should be empirically administered antistaphylococcal antibiotics when culture specimens are unobtainable. Intravenous therapy is continued for up to 6 weeks without further surgical intervention as long as the patient is improving clinically. Open surgical drainage of the sacroiliac joint is rarely indicated.
OSTEOID OSTEOMA AND OSTEOBLASTOMA
Osteoid osteoma and osteoblastoma are benign bone tumors that commonly cause back pain in children.18 In the spine, they occur in the posterior elements (ie, the lamina, facet, and pedicle). The histologies of osteoid osteoma and osteoblastoma are identical and these lesions are differentiated by the size of the tumor. If the lesion is smaller than 1.5 cm in diameter, it is an osteoid osteoma. If larger than 1.5 cm in diameter, it is an osteoblastoma.
The average age at symptom onset is 14.5 years (range 5 to 31 years) for osteoid osteoma and 23.1 years (range 12.9 to 54 years) for osteoblastoma. The average duration of pain before diagnosis has been 12 to 35 months. Patients may present with pain in the back, painful scoliosis, and radicular or referred pain into the upper or lower extremities. Symptoms are typically present before the lesion can be seen on radiographs. The pain is dull throbbing or sharp stabbing (knife-like) in character, aggravated with motion, and not relieved by rest. The pain is present at night, and classically the patient from sleep at the same predictable time each night. Cervical lesions have radiation into the shoulder and arm, and the of lumbar lesions can radiate to the ipsilaterthigh or calf. The pain increases with coughing sneezing. Classically, the pain responds so well to aspirin that such a history has been considered almost diagnostic. Unfortunately, that response is not really that reliable.
Figure 6. Radiograph of an 1 1 -year-old boy with pain and scoliosis caused by a osteoid osteoma at TIO (arrow).
Findings on physical examination are variable and nonspecific. There may be "compensated" scoliosis, meaning that the head is centered over the midline. When pain is severe, the patient may have uncompensated scoliosis where the head does not center over the midline.
Soon after the onset of symptoms, the tumor may not be radiographically visualized, so depending on radiographic findings alone can delay the diagnosis. As time passes, a sclerotic margin appears around a central nidus and the lesion can then be visualized as a "white pedicle or lamina." If there is scoliosis, the tumor will be located within two vertebra of the apex of the curve (Fig. 6). Technetium bone scan is the definitive diagnostic study for localization of the tumor. Once the tumor has been located, a CT scan further defines the local anatomy for surgical excision (Fig. 7).
Figure 7. A computerized tomography scan of the boy in Figure 6 further localizes the central sclerotic lesion (arrow) to the lamina.
To obtain the best relief of pain and prevent persistence or progression of the scoliosis, surgical excision is recommended. Tumors in the lamina can be treated with surgical excision alone. Patients treated with only simple excision notice relief of pain within a few hours of surgery. Lesions of the facet joint or pedicle may require a fusion to prevent pain and instability. If the lesion is adequately treated, 95% of patients will remain free from pain.
Complications sometimes result from an inability to adequately localize the osteoid osteoma at the time of surgery. The use of a radioisotope surgical probe can improve surgical accuracy. With exposure at the proper level, the isotope probe can be used to pick up a higher count in the operative field over the lesion. When the tumor is excised, it can be placed on the operative field away from the patient and the high isotope count can again be verified by the probe. The specimen can then be taken to the radiologic suite, where it can be scanned and compared with the preoperative bone scan to confirm complete excision.
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