Differential Diagnosis in Spine Surgery Alexander R Vaccaro, John D Koerner, Daniel H Kim
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Lower Back Pain in Children and AdolescentsCHAPTER 1

Tamir Bloom,
Sanjeev Sabharwal,
Saad B Chaudhary
Lower back pain is uncommon in young children (< 10 years old) but may be experienced by as many as 36% of older children and adolescents,1,2 with an even higher incidence in competitive adolescent athletes.35 In the older child or adolescent, the evaluation of nonspecific, chronic back pain (lasting > 3 months) frequently does not result in an identifiable organic cause despite the use of an extensive diagnostic workup.6 While young children are more likely to have an underlying pathologic cause for their discomfort, mechanical back pain (defined as pain when there is no identifiable etiology detected on physical examination, radiographs, or advanced imaging investigation) accounts for the majority of juvenile and adolescent lower back pain.69 It is important to be able to discern patients who have mechanical back pain, and require only symptomatic treatment and observation, from patients with a suspected serious organic cause for the symptoms so that sophisticated diagnostic imaging studies and laboratory tests can be appropriately obtained and timely treatment can be instituted. The initial step in differentiating between patients who experience mechanical back pain from those with a specific etiology or demonstrable pathology is a careful medical history and a physical examination.
A thorough history provides the clinician with the most vital diagnostic tool when evaluating a child with lower back pain. Furthermore, a comprehensive clinical assessment, with interview questions based on pertinent differential diagnosis can help direct further workup. Perform the initial history with the parents present and in methodical fashion. Have patients describe the nature of their pain including, location (symmetric or asymmetric, midline or paraspinal), nature of onset, character (dull, aching, or sharp), severity, timing, frequency, and any associated radiation. It may be challenging to get children 2to answer all questions accurately as they are not always specific in localizing the area of concern. The interaction between the patient and the parents may provide clues as to their relationship and may shed light on the nature of the child's pain. Any changes or limitations in the child's activity because of pain can help to understand the severity of the pain. The clinician should also inquire about any history of prior trauma, aggravating and alleviating factors, the presence of neurological symptoms, changes in the child's gait or posture, constitutional symptoms, history of prior infection, including any systemic illness. In young athletes, questions related to sports, including the type of activities, amount of training per day or week, type of training, amount of training per year (down-time) for specific sports, supervision of training, and expectations or importance of that particular sport to both the athlete and the family can provide insightful information.10,11
Lower back pain is a relatively common complaint in the skeletally immature patient, and the following generalizations may help in identifying children with a diagnosable pathology. Commonly, an underlying cause for back pain is found in children whose duration of pain is greater than 4 weeks but less than 3 months.7 Young children and toddlers who present with pain are unlikely to exaggerate symptoms or physical findings, and frequently have a specific pathologic process causing their symptoms. Warning signs where an underlying abnormality is likely to be found include persistent or increasing pain, being worse at night or when lying down, radicular pain, neurologic deficits, loss of motion, spasms, and systemic symptoms (Box 1.1).9 Identifying spinal cord or nerve root impingement requires understanding of neurological symptoms, such as radiculopathy, myelopathy, gait changes, and bowel or bladder changes.
Nonspecific back pain in teenagers may be associated with psychosocial factors (e.g. increasing difficulty with school performance, social maladjustment, physical/sexual abuse, teen pregnancy, and recent familial unrest/death/divorce) or psychological problems (e.g. anxiety disorders, depression, and attempted suicide), as well as litigation and psychosomatic conversion reaction. When appropriate, inquire about family members or friends with similar symptoms and whether they have any disability or physical handicaps. In our experience, a child with back pain related to a history of a motor vehicle accident, whether recent or remote often have lingering back pain. Inquire about a possible history of litigation and be wary when the parents do not allow the child to directly respond to physician's questions.
History regarding backpack wear and the amount of weight within the backpack,1215 as well as amount of time playing video games16 and tobacco use17,18 should be discussed as these have also been implicated in nonspecific lower back pain in adolescence. In addition, medical history, medications, surgical history, and family history may provide insight to other causes of pain or possible predisposing reasons for pain.3
Although no condition is exclusive to a particular age group, the age of the patient is helpful in establishing a differential diagnosis (Table 1.1). Children below the age of 4 years are more likely to have infection or neoplasm, whereas mechanical back pain or pain associated with trauma or overuse syndromes is more often encountered in patients greater than 10 years. Characteristics of the pain (onset, duration, timing, and location) offer valuable information. In general, patients with mechanical back pain present with complaints of non-neurologic, nonspecific, intermittent and chronic pain. Pain of sudden onset or pain that is most intense 24–48 hours after injury, heavy lifting, or vigorous physical activity occurs commonly from self-limited lumbar sprains or strains, or less frequently from a fracture, apophyseal ring injury, or herniated disk. The most common identifiable diagnosis producing lumbar back pain in active patients between the ages of 10 and 15 years is spondylolysis or spondylolisthesis.19 Painful defects, fractures, and stress lesions within the pars interarticularis are often seen in patients participating in sports that tend to involve repetitive hyperextension of the spine, such as gymnastics, figure skating, cheerleading, football (linemen), and volleyball. Athletes involved in these particular sports may also develop pain secondary to degenerative disk disease, but exact correlation between a degenerative intervertebral disk and lower back pain remains elusive.20 Insidious pain that is activity related and relieved with rest may also be due to recurrent lumbar strains/sprains, spondylolysis, apophyseal ring fractures, and sacral stress fractures.
Persistent lower back pain not associated with trauma and not relieved by 2–3 weeks rest, activity modification, nonsteroidal anti-inflammatories, or pain that awakens the patient from sleep is more concerning for infection or neoplasm.
Table 1.1   Differential diagnosis of common spinal causes of pediatric lower back pain (LBP) by age.
Presenting characteristics of lower back pain
Associated symptoms
Birth to 4 years
  • Nonspecific
  • Unremitting, night pain
  • Limp, hip or leg pain (refusal to walk)
  • Abdominal pain
  • Systemic symptoms (fever, poor appetite, lethargy, malaise)
Malignant tumors
(e.g. leukemia, lymphoma, sarcoma)
Metastases to the spine (e.g. neuroblastoma, rhabdomyosarcoma)
Tumor-like lesions (e.g. eosinophilic granuloma)
  • Slow-onset, nonspecific LBP
  • Progressively more severe
  • Unrelenting
  • Night pain
  • Radiating pain below the knees
  • Systemic symptoms
5–11 years
  • Nonspecific
  • Unremitting, night pain
  • Limp, hip or leg pain (refusal to walk)
  • Systemic symptoms
Benign bone tumors (e.g. osteoid osteoma, osteoblastoma)
Bone cyst (unicameral or aneurysmal)
  • Slow-onset
  • Sharp, constant
  • Worse at night
  • Alleviated by NSAIDs
Malignant tumors and metastases
(e.g.osteosarcoma, Ewing's sarcoma)
Spinal cord tumors (e.g. astrocytoma, ependymoma)
  • Nonspecific
  • Unremitting, night pain
  • Systemic symptoms
  • Gait abnormalities, delay in achieving motor milestones
Idiopathic juvenile osteoporosis
  • Extreme pain
  • Difficulty walking
12 years to maturity
Mechanical back pain
  • Chronic or intermittent
  • Nonspecific
  • Aggravated by prolonged standing, walking or sitting
  • Alleviated by NSAIDs, rest, massage, heat
  • No radicular symptoms
Muscle strain/ligament strain
  • Acute, short duration
  • Sharp, mild
  • Alleviated by NSAIDs, rest, massage, heat
  • Muscle tenderness without radiation
  • Acute or chronic
  • Dull or aching
  • Intermittent or recurrent
  • Aggravated by sports, particularly those involving repetitive hyperextension of the trunk
  • Relieved by rest or restriction of athletic or physical activity, NSAIDs
  • Pain radiating to gluteal region and posterior thighs
  • Spasms of paravertebral or hamstring muscles
  • Bowel or bladder dysfunction can occur with signifiant slip progression
  • Lumbar or thoracolumbar scoliosis may occur with spondylolisthesis
Herniated intervertebral disk
  • Acute or insidious
  • Insidious, recurrent or with activity
  • Aggravated by prolonged walking or sitting, coughing or sneezing
  • Alleviated by NSAIDs, rest, massage, heat
  • Radicular pain to the buttock, lateral thigh, or leg
Slipped vertebral ring apophysis
  • Acute, sharp, constant
  • Aggravated by prolonged walking or sitting, coughing or sneezing
  • Alleviated by NSAIDs, rest
  • Radicular pain to the buttock or lateral thigh, usually bilateral
Degenerative disk disease
  • Chronic
  • Activity related
  • Alleviated by NSAIDs, rest, massage, heat
  • Spasms of paravertebral or hamstring muscles
Ankylosing spondylitis, other spondyloarthritides
  • Insidious, slow-onset, chronic (> 3 months)
  • Dull or achy
  • Pain and stiffness usually worse in the mornings and during the night, may improve by warm shower or light exercise but not with rest
  • Morning stiffness
  • Joint pain, swelling of the lower limbs
  • Symptoms of anterior uveitis (eye redness, pain, light sensitivity, vision problems, etc.)
  • Constitutional symptoms
Lumbar Scheuermann's kyphosis
  • Slow-onset, chronic
  • Dull or achy
  • Aggravated by prolonged sitting, walking or activity
Infection—diskitis, vertebral (pyogenic) osteomyelitis, tuberculous spondylitis (non-pyogenic)
  • Slow-onset, may be chronic for non-pyogenic infection
  • Dull, achy, or sharp
  • Aggravated by activity, may also include night and resting pain
  • Limp, hip or leg pain
  • Abdominal pain
  • Systemic symptoms
Sacralization of L5/transverse process impingement
Bertolotti's syndrome21
  • Chronic
  • Dull or achy
  • Activity related
  • Chronic sciatica
Psychogenic back pain, conversion reactions
  • Slow-onset, chronic
  • Dull or achy
Tumors of the spine
  • Unremitting, persistent
  • Not activity related
  • Systemic symptoms
(NSAIDs: Nonsteroidal anti-inflammatory drugs).
Table 1.2   Pediatric lower back pain not localized to the lumbar spine.
Sacral and sacroiliac joint
  • Sacroiliitis (associated with ankylosing spondylitis)
  • Pyogenic sacroiliitis
  • Sacral stress fracture22
  • Arachnoid cyst23,24
  • Appendicitis
  • Inflammatory bowel disease
  • Hydronephrosis
  • Urinary tract infection/pyelonephritis
  • Gynecologic abnormalities, e.g. ovarian cysts
  • Psoas abscess
Diagnoses of exclusion
  • Overuse syndromes
  • Pain associated with menstrual period
  • Psychosomatic (conversion reaction)
(Frymoyer, John W; Wiesel, Sam W, et al. eds. The Adult & Pediatric Spine. Chpt 21. “Back Pain in Children and Adolescents” Lippincott Williams & Wilkins. 2004).
Night pain that prevents the patient from going to sleep but once asleep does not awaken the patient is more common in mechanical conditions. On the other hand, night pain, due to which the patient is awakened from sleep by the pain, is more likely to be due to a more serious condition and should always raise the concern of an infection or neoplastic condition (Table 1.2). Pain localized to the lower lumbar spine is more commonly seen in conditions such as spondylolysis and spondylolisthesis; pain in the sacroiliac (SI) area may indicate an inflammatory arthropathy, infection, or tumor. Infections and neoplasms may occur in any portion of the spinal column. Symmetric pain may be due to mechanical or an overuse condition, whereas asymmetric pain localized to one side of the spine may be more likely due to spondylolysis or tumors. Pain worsened by coughing or sneezing, radicular pain, change in bowel or bladder habits, asymmetric foot posturing or deformities may indicate the presence of conditions that can cause neural compression (e.g. herniated nucleus pulposus, intraspinal tumors, tethered spinal cord, syringomyelia, or severe spondylolisthesis).
Anatomy/Physical Exam
Visual Inspection and Assessment of Alignment and Motion
The physical examination of a pediatric patient should be tailored to each age group and suspected disease process. Enlisting the parents or caregivers with the examination, for example by demonstrating the exam technique first on the parent, may facilitate cooperation with the examination on a young or developmentally delayed child. A comprehensive examination should begin with placing the child in a gown (open in the back) with all articles of clothing removed, except for underpants or shorts, and long hair should be lifted so that the entire spine can be examined. Socks should be removed to look for any foot deformities that may signify intraspinal anomalies or tethered cord. Note the child's height, weight, and body habitus. Being overweight or obese is an important factor associated with back pain and can be identified by determining the body mass index (Source: apps.nccd.cdc.gov/dnpabmi/ Calculator.aspx).25,26
Observe the child's gait and standing coronal and sagittal posture with both lower extremities uncovered. In young children, watching the patient walk in the hallway, entering the examination room, or playing can frequently detect abnormalities in gait, strength, posture and balance. Children with severe spondylolisthesis may have a wide-based stance with the hips and knees flexion, a stiff lumbar spine with marked lumbar hyperlordosis, associated posterior pelvic tilt, heart-shaped buttocks (owing to the vertical position of the sacrum), a protruding abdomen, and a palpable “step-off” often noted at the lumbosacral junction. This standing posture has been described as the Phalen-Dickson sign.27 The normal heel-to-toe gait pattern may change in conditions associated with hamstring tightness, such as spondylolysis and spondylolisthesis. Hamstring tightness may prevent full extension of the knee in terminal swing (stiff-knee gait pattern), thereby causing a decrease in stride length. A limp or ataxia, with or without pain, may be the presenting sign of an intraspinal disorder.
With the child standing, inspect the back for cutaneous findings. A hair patch, subcutaneous lipoma, hemangioma, or sacral dimple may indicate spinal dysraphism. Café-au-lait spots may indicate neurofibromatosis. Assess posture and coronal and sagittal alignment for signs of scoliosis or kyphosis. When viewing a patient from a lateral position, a kyphotic deformity is evident at the thoracic spine or the thoracolumbar junction in Scheuermann's disease. The angular kyphosis is seen most clearly when the patient bends forward, distinguishing it from postural kyphosis which is flexible (Figs. 1.1A to D). Patients with Scheuermann's disease may stand with compensatory lumbar and cervical lordosis, as well as with the shoulders appearing rounded and the head protruding forward.8
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Figs. 1.1A to D: Clinical appearance of a 17-year-old male with long standing back pain and pronounced thoracic kyphosis due to Scheuermann's disease. (A) Standing sagittal alignment demonstrating greater than normal thoracic kyphosis and rounding of the shoulders, (B) With the patient bending forward, an angular kyphosis is seen rather than the normal gradual rounding of the thoracic spine, (C and D) Posteroanterior and lateral radiographs demonstrate a thoracic kyphotic deformity in the order of 85°, vertebral end plate irregularities, and the anterior vertebral wedging in the thoracic spine.
Look for any asymmetry in the neck, level of the shoulders, level of the scapular spines, prominence of the scapulae, surface of the rib cage, and contour of the flanks. The iliac crests are palpated to determine if they are level, or the posterior iliac dimples may be observed for symmetry, indicating equal leg lengths (Fig. 1.2). A difference in the level of the iliac crest may indicate a limb-length discrepancy that can cause a compensatory scoliosis deformity (convex toward the shorter limb) to balance the head over the pelvis. This postural scoliosis will disappear when the leg lengths are corrected by placing an appropriately sized lift under the foot of the short leg. A plumb line, measured by suspending a weight from a string from the C7 spinous process to the level of the pelvis, can be used to determine if the spine is compensated or decompensated. If the spine is compensated, a plumb bob should lie directly over the center of the gluteal cleft. If there is coronal decompensation, usually secondary to scoliosis, the plumb bob will fall 2 cm or more on either side of the gluteal cleft.
The Adam's forward-bending test is useful to detect scoliosis and to determine if the spine is supple and flexes symmetrically. With the clinician standing behind the patient, perform the test by having the patient bending forward at the waist and the arms hanging freely in front with the palms opposed.9
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Fig. 1.2: Clinical photograph demonstrating symmetric palpation of the iliac crests indicating a level pelvis.
Ensure that the knees are fully extended and have the patient reach for their toes. If the patient bends to one side instead of straight ahead, it may indicate a hamstring contracture. With the patient's spine parallel to the floor, asymmetry of the trunk may be observed indicating a rotational component of a scoliosis deformity (Figs. 1.3A to C). The angular degree of thoracic or lumbar prominence can be assessed using a scoliometer placed at the point of maximal asymmetry to measure the angle of trunk rotation, or rib prominence. With the spine flexed, hamstring and paraspinal tightness can be assessed by measuring the distance from the floor to the patient's fingertips. Limited forward bending may be associated with back pain and spondylolisthesis.18 In toddlers and children, the “coin test” may indicate an inability to flex the lower back, assessed by placing an object, such as a coin (or a candy), on the floor and asking the child to pick it up. The test is positive if the back is held in an abnormally stiff posture, with the loss of the usually smooth flexion and extension of the spine, and bends primarily at the hips and knees. Toddlers or children with diskitis commonly present with a positive coin test, loss of lumbar lordosis, refusal to walk, limp, and hip or leg pain.28 In general, pain provoked with back hyperextension and relieved with flexion is usually the result of pathology from the posterior spinal elements (pars interarticularis, facet joints, spinous processes). Pain with hyperflexion but relief in extension, arises from the vertebral bodies, disks, or anterior soft tissues.10
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Figs. 1.3A to C: (A) Clinical photograph of a 12-year-old female demonstrating a prominent right scapula, asymmetry in the level of the shoulder, and asymmetry of the flank commonly seen in adolescent idiopathic scoliosis, (B) Adam's forwardbending test reveals one side of the back appears higher than the other, (C) The clinical appearance on the sagittal profile illustrating rib asymmetry and loss of normal thoracic kyphosis.
Further assess spinal mobility with extension, rotation or bending at the waist, and to the right and left, as motion may be restricted in patients with lower back pain or paraspinal muscle spasm.
Ask the child to localize the back pain with the point of a finger. A child or adolescent that points to one spot, a positive “finger test,” may more likely to have true pathology causing their back pain. An adolescent with typical mechanical back pain is more likely to localize their pain over a broad area, particularly transversely across the lower back. Palpate the spinous processes and sacrum for areas of focal tenderness and percuss any areas of pain identified by the patient. Patients with spondylolysis will frequently experience pain when the affected spinous process is palpated, particularly 11at the L5 spinous process. Tenderness over the paraspinal muscles may indicate muscle spasms. Defects in the posterior elements may be palpated by running the fingers along the spine.
A single-leg lumbar hyperextension test (Stork test) is performed by having the patient stand on one leg with the contralateral knee flexed and hyperextending the back (Fig. 1.4). The testing position increases pressure at the pars interarticularis on the side of weight bearing. Lumbar pain on the weight-bearing side is a common finding in patients with spondylolysis or spondylolisthesis. This procedure also assesses proprioception and stability. Pain originating from the SI joint may be detected with the Patrick or Flexion, Abduction, and External Rotation (FABER) test. This test is performed with the patient lying supine, placing the foot of the affected side on the contralateral knee and pressing firmly on the flexed knee and on the opposite anterior superior iliac crest; this maneuver enhances pain localized to the SI area. Hamstring flexibility may further be assessed by measuring the popliteal angle. With the patient supine, place the contralateral leg flat on the exam table. The ipsilateral hip is flexed 90° and the knee is gradually extended to its natural limit. The angle formed by a vertical line along the posterior thigh and calf is measured. Popliteal angle less than 130° indicated hamstring tightness.29 While lying supine, the lower extremities can be examined for equal leg lengths, joint deformity, and muscle bulk.
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Fig. 1.4: The Stork test is performed with the patient standing on one leg and extending the lumbar spine. Pain in the lower back with hyperextension is a common finding in spondylolysis and spondylolisthesis. This test also assesses global proprioception and stability. This test can be performed with the patient's eyes closed to further assess proprioception in the absence of visual input. A positive finding is the patient's inability to stand with little or no body motion for 10 seconds.
Neurologic Examination
A thorough neurological examination of the extremities includes assessment for muscle strength, sensation, deep tendon reflexes, and presence of any long tract signs, such as muscle wasting, fasciculations, weakness, hypertonia/ hypotonia, clonus, hyper-reflexia, altered or loss of sensation, and sphincter disorders (disorders of urination, bowel and sexual function). In a busy office setting, this can be accomplished efficiently by having the child heel walk, toe walk, and perform a single-leg hop on each foot in turn to assess the general strength, muscle tone and coordination. Performing a straight-leg raise test, standard lower extremity joint reflexes, abdominal reflexes, Babinski test, checking for sustained clonus, and sensory examination can evaluate for neurologic abnormalities. Adolescent lumbar disk herniation, occurring most commonly at the L5/S1 level followed by L4/L5,30 may present with an abnormal motor, sensory, and reflex examination. A disk protrusion at L5/S1 usually affects the first sacral nerve root causing sensory changes over lateral aspects of the calf and foot, weakness in the gastrocsoleus muscle and a decreased Achilles tendon reflex. A disk protrusion at L4/L5 usually affects the L5 nerve root and may cause sensory changes over the dorsal and medial aspect of the foot, particularly the first web space, weakness in dorsiflexion of the great toe and inversion. Increased or asymmetric reflexes can indicate myelopathic or intramedullary lesions involving the spinal cord. A straight-leg raise test is important for assessing signs related to lumbar nerve root irritation. The test is performed with the patient supine, with the examiner gradually raising one leg with the hip and knee in extension. A positive test reproduces the patient's radicular symptoms with the leg elevated off the exam table. The test is reported as an angle between the lower limb and the tabletop. A contralateral straight-leg raise test should also be performed as it can function as a confirmatory test with high specificity for diagnosing a disk herniation. A positive test reproduces the patient's radicular symptoms with raising the unaffected side. Although less common, an upper lumbar disk herniation can be responsible for back pain and radiculopathy and can be aptly evaluated with a femoral stretch test. This test is generally performed with the patient in the prone position with the knee passively flexed to the thigh and the hip passively extended. Again a positive test results in reproduction of the patient's symptoms with this provocative maneuver. Assess the feet for abnormalities such as, cavus foot, clubfoot, and clawing of the digits.
Imaging Studies
The most useful imaging study in children with back pain is a standing anteroposterior (AP) and lateral radiograph of the portion of the spine that seems to be involved, either thoracolumbar or lumbosacral spine.13
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Figs. 1.5A to D: A 9-year-old boy with a history of left sacroiliac joint pain. (A) Anteroposterior radiograph of the pelvis demonstrates focal osteopenia in the left sacral ala, (B and C) Coronal and axial CT of the pelvis shows a lytic lesion destroying the posterior and medial cortex of the left ilium with disruption of the articular surface of the left ilium, (D) Axial T2-Fast Spin Echo weighted image shows the lesion extending into the sacroiliac joint with soft tissue edema. Incisional biopsy was consistent with anaplastic lymphoma.
Consider including the pelvis, because some lesions in the pelvis and sacrum, e.g. osteoid osteoma and spinal arachnoid cysts, may cause lower back pain (Figs. 1.5A to D). Lead-shielding to minimize ionizing radiation exposure to the gonads should not be used for the initial radiographs because it may obscure a lesion in this region. Radiographs should be obtained during the initial evaluation of all children (age 10 years or younger) with persistent, unremitting lower back pain longer than 6 weeks, or who have any “red flags” (see Box 1.1). On the AP image, evaluate for normal vertebral body morphology (no evidence of congenital vertebra), overall coronal alignment to assess for presence of scoliosis, assess disk height, confirm the presence of two pedicles at each level, and assess soft-tissue shadows, including the psoas muscle. The pelvis and hips should also be evaluated if appropriate, because symptoms often described as back pain may have their origin elsewhere in the general vicinity of the lumbar spine. The lateral radiograph should be assessed for alignment and the presence of normal thoracic kyphosis and 14lumbar lordosis.31 Excessive kyphosis in the thoracic region may indicate Scheuermann's kyphosis, congenital kyphosis, osseous spine tumor, or infection. Loss of lordosis in the lumbar spine is often seen with paraspinal muscle contraction associated with significant back pain. Excessive lumbar lordosis can be seen in spondylolisthesis, and the specific subtype should also be identifiable. Detectable radiographic abnormalities include disk space narrowing, vertebral end-plate irregularities, vertebral scalloping, bone lesions, and scoliosis.
It is recommended that further radiographic studies be performed based on each individual patient. If scoliosis is suspected (if the angle of trunk rotation is greater than 7° on scoliometer), 3-foot long cassette standing posteroanterior and lateral radiographs of the thoracolumbar spine are warranted. For spondylolysis, anterior–posterior and lateral plain films of the lumbar spine are often diagnostic. Oblique views can be ordered but may not add significant value in identifying spondylolytic lesions.32,33 In juvenile onset spondyloarthritis, a single AP view of the pelvis is adequate for the radiographic assessment of the SI joint.34 Advanced imaging studies should be obtained only after radiographs have been evaluated, since most diagnoses can be made with initial plain radiographs.6
Further Workup
Standard three-phase Technetium bone scans are extremely sensitive in identifying a bony abnormality such as an osteoid osteoma or osteoblastoma, but have very low specificity in establishing the diagnosis of spondylolysis. Single-photon emission computed tomography (SPECT) scanning of the lumbar spine is useful and a highly sensitive imaging technique that can accurately localize the pars interarticularis lesion. The advantages of SPECT scans include, (1) ability to diagnose early active lesions before a fracture occurs (i.e. stress reaction or subacute injury to the pars), (2) differentiate between symptomatic and asymptomatic (or silent) pars defects, and (3) determine the chronicity of lesions which may indicate healing potential. Compared to magnetic resonance imaging (MRI), SPECT is less likely to require sedation, can usually be obtained faster at most institutions, and is less expensive. Potential disadvantages of SPECT imaging include the potential for false positives (a hot bone scan on SPECT may be seen in infections, tumors and arthritis), inability to detect a chronic nonunion, and radiation exposure.
A computed tomography (CT) scan is useful for evaluating bony anatomy, and can help localize small bony lesions, such as osteoid osteoma, as well as other bonytumors (such as aneurysmal bone cysts, osteoblastomas), vertebral osteomyelitis, and acute fractures. Three-dimensional reconstructions can be obtained to better represent complex lesions or deformities. CT scans are more specific than SPECT in delineating defects in the pars interarticularis and can help in circumstances when SPECT is positive but nondiagnostic.15
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Figs. 1.6A to C: A 6-year-old female with 1-month history of low back pain and limp. (A and B) Initial anteroposterior and lateral radiographs reveal end plate irregularities on the inferior end plate of L4 on the lateral view, (C) Subsequent MRI examination without contrast of the lumbar spine was performed demonstrating findings consistent with both diskitis and vertebral osteomyelitis. A sagittal view T2-Fast Spin Echo weighted image shows loss in L4-5 disk space height, edema within the L4 vertebral body and the superior end plate of L5, and an enhancing fluid collection anterior to the L4 and L5 vertebral bodies.
CT scans can help determine the chronicity of spondylolytic lesions, and are useful as follow-up studies for monitoring healing; however, there is concern for excessive radiation exposure.
Magnetic resonance imaging is excellent at evaluating for intraspinal abnormalities, disk herniations, tumors and infection. Consider obtaining an MRI in the presence of the “red flags” (see Box 1.1), or elevated inflammatory indices (erythrocyte sedimentation rate, C-reactive protein), or other concerning symptoms for an infection or malignancy. In diskitis, because plain radiographs may be normal until 3–8 weeks after the onset of symptoms, use of MRI may facilitate early diagnosis, aid recovery, and avoid lengthy hospitalization (Figs. 1.6A to C).28 In this situation, MRI with gadolinium can differentiate between diskitis, vertebral osteomyelitis, paravertebral inflammation or abscess, and pathology of the hip or spinal cord.35 MRI is also able to detect and help gauge the chronicity of most spondylolytic lesions, determine the condition of the adjacent intervertebral disks, and exclude canal or foraminal stenosis resulting in neural compression. However, for spondylolytic lesions, MRI has a limited ability to assess cortical integrity to distinguish complete versus incomplete fractures, and to detect bony healing.16
In adolescent patients, if an apophyseal fracture is suspected on MRI, a CT scan is indicated to evaluate for a slipped vertebral apophysis because it may alter the approach to treatment.30 With clinical suspicion of spondyloarthritis [back pain for > 3 months, positive human leukocyte antigen B27 (HLAB27)], MRI may be very helpful to confirm the diagnosis in an early disease stage, providing information on both disease activity and structural damage, without exposing patients to ionizing radiation (a major disadvantage of CT scan).36
There are varying opinions and little evidence-based consensus regarding the preferred advanced imaging test to reliably rule out an organic cause of lower back pain in children. Auerbach et al. recommend SPECT imaging in children with non-neurologic back pain of less than 6 weeks duration and MRI for those with persistent pain, particularly with hyperextension testing.37 If initial radiographs are negative, Feldman et al. recommend MRI in patients with constant pain, night pain, radicular pain, and/or abnormal neurologic examination.9 Ultimately, the decision to obtain imaging studies in the workup of back pain should be contextual and include diagnostic accuracy, urgency, potential side effects, and limitations of each imaging test.
Laboratory studies, consisting of complete blood count with differential, erythrocyte sedimentation rate, and C-reactive protein should be obtained if there is concern for infection or malignancy (e.g. leukemia). If there is concern for inflammatory arthropathy and spondyloarthritis, HLA-B27 and rheumatoid factor (RF) should be ordered. Lyme disease may sometimes present with diffuse low back pain and is endemic in certain geographical regions.38 If this condition is suspected, Lyme titers can be tested followed by a Western blot analysis. Urinalysis should also be ordered for flank pain or tenderness, dysuria, or abdominal pain.
The prevalence of low back pain in the pediatric population is increasing, but most patients have no specific organic etiology for back pain. The task of evaluating a child with low back pain necessitates a complete understanding of the wide range of disorders that may cause back pain in pediatric patients, and performing a detailed history and physical examination tailored appropriately to the patient's age. Information obtained from the history and clinical examination is critical in identifying children who require symptomatic treatment from those who merit further diagnostic studies. Radiographs of the spine are the best screening examination for the child with back pain and are indicated if the patient is 10 years of age or younger, if there is a history of significant trauma, persistent pain, duration of pain is 2 months or longer, 17any associated red flags (see Box 1.1), or if the clinical findings cannot sufficiently rule out organic causes of back pain. When a serious underlying pathological cause of back pain is suspected, further investigation with diagnostic imaging such as CT scan, MRI, and/or SPECT/ bone scan should be considered on an individual basis.
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