Even though primary infections and tumors of the spine are rare in
children, orthopaedic surgeons must be aware of the characteristic
presentation of these conditions to ensure a timely and appropriate workup.
The most common presenting symptom among this group of patients is back pain,
a ubiquitous and nonspecific complaint. Although the differential diagnosis
for children with back pain is broad, a higher index of suspicion should be
maintained for children than for adults because structural pathology is more
likely to be the cause of back pain in children. The information gained from a
detailed history and physical examination as well as from a careful assessment
of imaging studies usually enables a physician to narrow the differential
diagnosis and to suspect an infection or spinal tumor in children. A thorough
initial examination and early imaging studies facilitate the planning of
appropriate further work-up, imaging, biopsy, and management. When tumor or
infection is suspected, these steps should be done rapidly to prevent delays
that can decrease the likelihood of a satisfactory outcome and cause children
and families to worry unnecessarily about the possibility of a malignant
disease.
Five general principles for the evaluation and management of infants and
children with possible infection and tumors of the spine should be followed to
ensure timely diagnosis and treatment: (1) perform a complete clinical workup
with appropriate high-quality imaging; (2) if aspiration or biopsy is needed
to confirm the diagnosis, choose a technique that is simple, safe, and
effective; (3) if surgery is indicated, plan surgery with a standardized
spinal surgical staging system and principles; (4) use appropriate adjuvant
treatments or modalities that are based on the condition of the child and the
type of infection or the natural history and stage of the tumor; and (5)
preserve neurologic function and stability of the spinal column.
The goals of this review are: first, to present an overview of the
important elements of the initial patient evaluation, clinical presentation,
imaging strategies, laboratory studies, and biopsy techniques; second, to
describe the specific types of infections and tumors most often seen in the
pediatric spine; and third, to provide an overview of treatment strategies for
benign and malignant tumors as well as spinal infections.
Clinical Presentation
Pain is a relatively common presenting symptom in children and young
adults, and reports of persistent back pain warrant consideration of an
underlying pathologic process, including a spinal tumor or infection. In a
series of children with infection of the spine, all thirty-six children with
discitis and all fourteen children with vertebral osteomyelitis initially
presented with refusal to walk or had a limp or back
pain1. The nature of
the pain reported by patients or by parents of children with spinal infection
is variable; the onset may be gradual or rapid, but it is usually exacerbated
by increased activity. Pain associated with most spinal tumors is
characteristically unrelenting, progressive, and often present at
night2-4.
On examination, pain associated with spinal tumors can usually be reproduced
with pressure and can be localized to the area of an involved spinal segment.
For patients in whom the growth of the tumor has weakened the vertebral body,
pathologic microfracture or, occasionally, a complete fracture can occur and
be associated with severe pain.
In the patient with a spinal tumor or infection, age can help to narrow a
list of possible diagnoses (Table
I). For children who are two years of age or younger, reluctance
and eventual refusal to bear weight can be an indication of spinal infection
or tumor and can easily be mistaken for other pathologic conditions, such as
septic arthritis of the hip. A common observation in very young children with
spinal pathology is that they tend to lean forward and place the hands on the
thighs to support the spine. Patients between seven and fifteen years of age
with spinal infection or tumor tend to present with back, pelvic, or abdominal
pain. In some patients, pain may not be localized at the site of the
infection. In their series of twenty patients with iliac osteomyelitis,
Beaupré and Carroll described three syndromes associated with iliac
osteomyelitis (gluteal, abdominal, and the so-called lumbar disc syndrome)
that reflect the location of the signs and symptoms that result from each of
the three distinct directions in which inflammation can
spread5. In their
series, thirteen children (65%) initially presented with signs of
"lumbar disc syndrome," characterized by low back, hip, and thigh
pain.
Children with spinal infection and tumors, particularly osteoid osteoma and
osteoblastoma, often have an associated spinal
deformity2,6-9.
These tumors are commonly found on the concave side of the apex of a curve and
can result in rapid progression of the
deformity10. In a
series of 115 children with spinal cord tumors, Tachdjian and Matson found
thirty-one children (27%) had scoliosis at
presentation11.
Lesions that lead to destruction of the bone and vertebral collapse (e.g.,
Langerhans cell histiocytosis) may also eventually result in scoliosis or
kyphosis. Vertebral osteomyelitis and tuberculous spondylitis can also cause
destruction of one or more vertebrae and lead to collapse and subsequent
deformity, although systemic signs are usually seen first. Children with
discitis may present with a loss of normal lumbar
lordosis12.
Neurologic involvement in children with vertebral osteomyelitis or discitis
is rare, and signs or symptoms usually occur well after the onset of pain.
However, there have been reports of neurologic signs, some serious, at the
time of presentation. In a recent series of forty-two children with
nontuberculous spondylodiscitis, four patients (10%) had neurologic signs on
admission: two had unilateral sciatic pain, one presented with upper limb
diplegia, and one had flaccid
paraplegia13. In
another review of eleven very young children with discitis, one child
presented with limb weakness, reduced muscle tone, and absent
reflexes12.
Although neurologic deficits produced by the extension of primary bone tumors
are also uncommon, neural canal compromise is seen more often in patients with
malignant tumors or spinal cord tumors. Radicular symptoms or myelopathy can
result from impingement of the tumor into nerveroot foramina or the spinal
canal, and compression at the level of the conus medullaris can lead to
sphincter dysfunction. A thorough neurologic assessment, including an
evaluation of bladder and bowel function, should be performed in all patients
with back pain.
Imaging Strategies
There are certain features associated with complaints of back pain in
children that suggest underlying pathology. "Red flags" include
severe pain, night pain, neurologic signs or symptoms, or pain that lasts more
than four weeks. The evaluation of these patients should include the
acquisition of high-quality posteroanterior and lateral standing or sitting
radiographs at the time of presentation and, often, advanced imaging, such as
magnetic resonance imaging, computed tomography, or a technetium bone scan. By
the time a child with a spinal tumor presents for medical attention, plain
radiography may be revealing. For some patients, the appearance of the lesion
on plain radiographs combined with information from the history and
examination helps to further refine and develop a differential diagnosis.
However, plain radiographs of patients with spinal infection do not always
reveal abnormal findings at the time of presentation. In a series of pediatric
patients with spinal infections, abnormal findings on initial radiographs were
found in twenty-five of thirty-three patients (76%) with discitis and in only
seven of thirteen patients (54%) with vertebral
osteomyelitis1.
The location of the lesion within the spine is an important prognosticator
for spinal tumors (Table II).
Children with vertebral lesions that affect the posterior elements and result
in destruction of the pedicle can be noted by a characteristic "winking
owl" sign that results from an absent pedicle on the anteroposterior
radiograph (Fig. 1). In
children with discitis and pyogenic vertebral osteomyelitis, infection starts
at the vertebral end plate and results in disc destruction and narrowing that
can be seen best on high-quality lateral radiographs of the spine or with the
use of other advanced imaging studies, such as magnetic resonance imaging or
computed tomography. Vertebral collapse is common among patients who have an
aggressive infection or a malignant tumor of the spinal column. Because the
avascular disc is highly resistant to invasion by tumors, disc height is
usually preserved, even after vertebral collapse, in the presence of a
tumor.
Advanced imaging is usually necessary to better define the process. If
plain radiographs are normal and the location of the pain is vague or variable
or if multiple sites of pain are present, a technetium-99 bone scan may be
useful to localize spinal pathology. These scans are highly sensitive for
identifying pathologic processes involving the spine but do not allow for
differentiation between and among specific tumors and types of infection.
Computed tomography is noninvasive, fast, usually well tolerated by
children, and best for defining bone pathology, although it does result in
increased exposure to radiation. Magnetic resonance imaging is also used and
has the advantage of providing the best definition of both bone and soft
tissue, allowing for an evaluation of the neural elements and surrounding soft
tissues in the region of the lesion. Edema and purulence appear as areas of
low-intensity signal on T1-weighted images and as areas of high-intensity
signal on T2-weighted images. Abnormal findings have been noted on magnetic
resonance images for 90% to 95% of patients with vertebral osteomyelitis and
nearly 100% of patients with
discitis1,14.
However, the specificity of magnetic resonance imaging may not be adequate to
differentiate between infection and tumor in some patients. In a series of
fifty-one patients, Pui et al. reported that there were no significant
differences between the apparent diffusion coefficients of diffusion-weighted
magnetic resonance imaging scans of patients with spinal infection compared
with those of patients with malignant
disease15. The
primary disadvantage of magnetic resonance imaging for infants and children is
the need for sedation or general anesthesia.
Laboratory Studies
A peripheral blood smear may show blastic or leukemic cells in the case of
leukemia. Chronic illness or infection may be associated with decreased
hematocrit and decreased levels of hemoglobin, and infection may be associated
with an increase in the white blood-cell count. Children with tumors sometimes
have a decrease in the white blood-cell count, but this finding is variable.
C-reactive protein levels and the erythrocyte sedimentation rate are elevated
but nonspecific in most patients with infection as well as in some patients
with malignant spinal tumors (especially Ewing sarcoma). Blood cultures are
indicated to help identify a causal organism in children with bacterial
infection in order to select the appropriate type of antimicrobial treatment.
An assessment of urinary metanephrines that shows elevation in normetanephrine
can help diagnose a neuroblastoma.
Biopsy
Early and appropriate treatment for infants and children who have spinal
infection or tumor depends on an accurate diagnosis, which usually requires a
biopsy. The exception is discitis, for which the clinical and radiographic
presentation is usually so characteristic that biopsy may not always be
necessary. The authors of a recent series of forty-two children with
nontuberculous spondylodiscitis reported that an organism was cultured from
twenty (61%) of thirty-three aspirates and from both specimens of two open
surgical biopsies. In this series, Staphylococcus aureus was the
organism most often identified: twelve (55%) of the twenty-two patients had
positive
cultures13. If
biopsy is indicated, careful attention to technique is essential; the risks
associated with biopsy can be reduced when the procedure is performed by an
experienced interventional radiologist working together with an orthopaedic
musculoskeletal tumor specialist, preferably at a center with experience in
treating children with benign and malignant musculoskeletal tumors and
infections.
Biopsy can be performed through percutaneous or open
techniques16,17.
Percutaneous biopsy is used when a specific diagnosis is suspected because the
tissue samples obtained are sometimes inadequate for multiple diagnostic
tests18. Although
an open biopsy can result in greater blood loss, it is often the best method
for evaluating tumors of the spinal column. It reduces or eliminates concerns
about inadequate samples, and it can afford the surgeon the option of
addressing the tumor within a single surgical exposure and anesthetic session,
when appropriate. Selection of the optimal biopsy technique depends on the
differential diagnosis, the location and extent of the lesion, and the
ultimate treatment plan.
For most infections and tumors of the spine, lesional tissue should be
evaluated with intraoperative frozen-section analysis, not only for diagnostic
purposes, but to confirm that lesional tissue has been obtained. When
malignancy is suspected, the biopsy incision should be placed to facilitate a
potential later resection of the tumor. Patients with sarcoma are usually
treated with neoadjuvant chemotherapy after biopsy, and subsequent resection
of the involved soft-tissue biopsy track is often required to achieve wide
margins and improve the odds of survival. If a soft-tissue mass is associated
with the malignant process, adequate lesional tissue for biopsy can usually be
obtained from the soft-tissue component of the
lesion19.
Tumors of the posterior elements of the spine are more easily sampled with
an open posterior biopsy technique. Tumors involving anterior elements of the
spine are sampled with either percutaneous computed tomography-directed needle
techniques or an open biopsy done through an anterior, posterolateral
costotransversectomy or through a transpedicular
approach18. Spinal
biopsy performed with use of thoracoscopy or laparoscopy may be appropriate
for some patients, but care should be taken not to contaminate the thoracic or
abdominal cavity in children with resectable sarcomas who do not have
metastatic disease.
Inflammation and Infection of the Spine
Disc-Space Infection
The mean age of children with discitis is approximately 2.8
years1. Although any
level of the spine can be affected, the infection is localized in the lumbar
or lumbosacral region in approximately 75% of
patients1,20,21.
Presenting symptoms are dependent on the ability of the child to communicate:
children who are two years of age or younger often refuse to walk or stand and
may support their weight by leaning forward with hands on thighs, whereas
older children often complain of back or abdominal pain and exhibit abnormal
posture. The onset of symptoms can be abrupt or gradual, and patients may be
febrile or have sepsis.
Laboratory analysis almost always shows an elevation in the level of
C-reactive protein, an elevated erythrocyte sedimentation rate, and an
increase in the white blood-cell count, but cultures are necessary to
determine the specific pathogen. Diagnosis is often confirmed by evidence of
disc-space narrowing on magnetic resonance imaging. Bone scans will reveal
positive findings, but plain radiographs will often be unrevealing for three
weeks following the initial appearance of
symptoms20-22.
Performing disc aspiration or biopsy is not always necessary unless the
child fails to respond to initial antibiotic treatment. There is conflicting
evidence about the sensitivity of cultures obtained from blood samples,
aspirate, and biopsy. In a series of forty-one children with discitis, Wenger
et al. reported that six of nine biopsy samples and nine of twenty-two blood
specimens that were cultured were positive for growth of Staphylococcus
aureus20.
In a series of thirty-six children with discitis, Fernandez et al. obtained
biopsies from a series of eight patients with discitis, none of which showed
bacterial growth1.
From the blood specimens cultured for thirty-two children in the same series,
four (13%) were positive for bacterial growth: Staphylococcus was isolated
from two specimens, Streptococcus from one, and gram-positive rods (not
further identified) from another. When an organism is identified, it is most
often Staphylococcus aureus, which is present in 50% to 67% of
cultures1,13,20.
For children with suspected discitis, the initial treatment is empirical.
Generally, parenteral antistaphylococcic antibiotics (the cephalosporin group)
are used for five to seven days, followed by orally administered antibiotics
for two to four weeks once a favorable clinical response is noted. Patients
are advised to rest, and the use of a brace is recommended for support and
pain relief. If improvement is not noted, if "red flags" or
evidence of atypical features or atypical infection are present, aspiration or
biopsy is indicated. If the patient fails to respond despite rest and
antibiotics, a neoplasm must be considered as a cause of continued
symptoms.
Vertebral Osteomyelitis
In contrast to children with discitis, patients with vertebral
osteomyelitis are more often systemically ill adolescents who present with
pain, muscle spasms, and fever. The mean age of a child with vertebral
osteomyelitis is between six and nine
years1. As with
disc-space infection, plain radiographs will not be revealing for skeletal
involvement until about three weeks after the onset of symptoms. However, in
some patients, vertebral osteomyelitis can eventually result in destruction of
the disc and the vertebral body (Fig.
2). There is also a fulminant form of neonatal vertebral
osteomyelitis. Eismont et al. reported on a series of four children with
vertebral osteomyelitis who were between two and thirteen weeks of age and
systemically ill on
presentation23.
Three of the four children had a recurrence of infection, and plain
radiographs taken at least two weeks after the onset of symptoms showed nearly
complete dissolution of the involved vertebral bodies, with normal or nearly
normal adjacent vertebral end plates. Magnetic resonance imaging is useful for
detecting the presence, extent, and location of abscess formation
(Fig. 3), and computed
tomographic imaging is best for defining bone destruction.
Aspiration or biopsy should be done in most cases and the material sent for
culture and histologic analysis; however, as with discitis, definitive results
cannot always be obtained. In their series of fourteen children with vertebral
osteomyelitis, Fernandez et al. reported that blood cultures were positive for
bacterial growth in eight patients (57%), that the bacteria identified in five
patients was Staphylococcus aureus; and that the aspirate or biopsy
was positive in four of the eight patients from whom cultures were
obtained1.
Treatment for children with vertebral osteomyelitis includes antibiotics
specific to the pathogen and rest and/or immobilization. Surgical
débridement is indicated if an abscess has formed, and instrumentation
may be necessary to reestablish or maintain spinal stability.
Sacroiliac Joint Infection
Children with infection of the sacroiliac joint space usually present with
pain in the lower back, buttock, hip, or abdomen and with fever. Pain is
produced with lateral compression of the pelvis or direct palpation of the
sacroiliac joint. Elevations in the level of C-reactive protein and of the
erythrocyte sedimentation rate and an increased white blood-cell count are
present, and a bone scan will show increased uptake in the region of the
sacroiliac joint. When formulating a differential diagnosis, ankylosing
spondylitis must also be considered. Treatment for sacroiliac joint infection
usually consists of antibiotic therapy and rest. If the patient does not
respond promptly to antibiotics, an aspirate should be obtained for culture.
An open biopsy is sometimes necessary, whereas surgical drainage is rarely
required.
Benign Tumors of the Spine
Langerhans Cell Histiocytosis (Eosinophilic Granuloma) of the
Spine
Langerhans cell histiocytosis, also known as eosinophilic granuloma, is a
self-limiting process that produces focal destruction of bone. Vertebral
involvement occurs in 10% to 15% of children with Langerhans cell
histiocytosis24 at
a mean age of eight
years24,25.
There is conflicting evidence about the predilection of Langerhans cell
histiocytosis for particular regions of the spine: some studies have indicated
that Langerhans cell histiocytosis is more common in the thoracic spine, while
others have reported a higher prevalence in the cervical
spine25-29.
The most common presenting complaint is
pain24,25,30.
Neurological symptoms are rarely seen. In a recent series of twenty-six
children with Langerhans cell histiocytosis of the spine, Garg et al. reported
that three patients (12%) presented with a neurologic symptom; all three
patients had pain that radiated down the upper extremity, and all were
subsequently found to have a cervical
lesion25.
Radiographically, vertebra plana is characteristic of Langerhans cell
histiocytosis, with partial or complete collapse of the vertebra resulting in
a "coin-on-edge" appearance, although spinal balance is maintained
in most
patients31,32.
The collapsed vertebra is usually located between two normal discs and
adjacent vertebrae and is most often seen on plain radiographs. The morphology
of vertebral collapse (Fig. 4)
has been described by Garg et al. and has been related to spinal
balance25. Grade-I
lesions exhibit 0% to 50% collapse, and grade-II lesions have 51% to 100%
collapse. Grade I and grade-II lesions are further classified as type A
(symmetric collapse) or type B (asymmetric collapse). Grade-III lesions
involve the posterior elements of the vertebra. In The Children's Hospital of
Philadelphia series of twenty-six children with a total of forty-four
Langerhans cell histiocytosis lesions of the spine, Garg et al. reported that
the radiographic data indicated that the initial vertebral collapse was grade
IA in twenty vertebrae, grade IB in three, grade IIA in ten, grade IIB in
nine, and grade III in
two25. The authors
of this series hypothesized that asymmetric vertebral collapse would be more
likely to lead to scoliosis or kyphosis than would symmetric collapse, but
found that of the four children who eventually had development of spinal
deformity, half had symmetric collapse (grade-IIA lesions) and half had
asymmetric collapse (grade-IIB
lesions)25.
Vertebral collapse may be the source of pain, spasms, torticollis in the
cervical spine, and, rarely, spinal deformities observed on presentation.
A skeletal survey or bone scan should be done to look for other lesions of
Langerhans cell histiocytosis associated with multifocal disease, which are
present in about half of patients diagnosed with musculoskeletal Langerhans
cell
histiocytosis24.
The differential diagnosis includes malignant diseases, such as Ewing sarcoma,
lymphoma, leukemia, and neuroblastoma, as well as other processes, such as
tuberculosis or atypical
infection33.
Magnetic resonance imaging is helpful in differentiating Langerhans cell
histiocytosis from other malignant diseases because soft-tissue masses are not
usually associated with the vertebral lesions of Langerhans cell
histiocytosis.
Biopsy is often necessary to confirm the diagnosis. The more accessible
extremity lesions, when present, can be biopsied in patients with multifocal
disease. There are three characteristic histologic components of these
neoplasms: (1) characteristic "coffee bean" appearing,
lipid-containing histiocytes from the reticuloendothelial system; (2)
eosinophils; and (3) Langerhans giant cells. Most children with Langerhans
cell histiocytosis have a favorable natural history: most lesions resolve with
time, and partial osseous reconstitution occurs
(Fig. 5). Treatment with local
corticosteroid injection has been used in the past, but it is not clear if
this treatment truly changes the natural history of the condition.
Chemotherapy is only recommended for the disseminated forms of Langerhans cell
histiocytosis. Recurrence or the appearance of new, additional lesions is most
often seen in children with bone and systemic involvement. Ghanem et al.
reported that eleven of seventeen children with systemic Langerhans cell
histiocytosis had development of new or recurrent lesions following
chemotherapy with adjuvant radiation therapy, as opposed to complete or
partial resolution in nearly all of the children without multisystem
involvement34.
Osteoblastoma and Osteoid Osteoma
Osteoblastoma accounts for less than 1% of all benign primary bone tumors
of the spine, while osteoid osteoma accounts for up to
9%35. Approximately
25% of all osteoid osteomas and between 30% and 50% of all osteoblastomas are
located in the
spine2-4,6,8,36-38.
Lesions are more common in the thoracic and lumbar spine than in the cervical
spine39,40.
Children with either lesion often initially present with pain, which is
sometimes worse at night and with activity. Night pain and pain relief with
use of acetylsalicylic acid are characteristic of osteoid osteoma. Patients
with osteoblastoma characteristically report little pain relief with
nonsteroidal antiinflammatory drugs. Lesions are often associated with spinal
deformity 2.
Saifuddin et al. reported a meta-analysis of 465 children and adults with
osteoblastoma or osteoid osteoma of the spine and found that 293 patients
(63%) had
scoliosis40. The
mean age of the patients with scoliosis was 15.3 years. The prevalence of
scoliosis in this series was 65% (124 of 191 patients) for osteoid osteoma and
52% (143 of 274 patients) for
osteoblastoma40.
Spinal osteoid osteoma and osteoblastoma are not easily identified on plain
radiographs. Advanced imaging is necessary to define the lesion and formulate
a diagnosis41.
Technetium bone scan is the most sensitive imaging technique for localizing
these tumors, and computed tomography imaging provides the best definition of
the lesion. Recent evidence suggests that magnetic resonance imaging can give
a falsely aggressive appearance to osteoid osteoma
(Figs. 6-A, 6-B, and
6-C)42.
Both osteoblastoma and osteoid osteoma demonstrate a predilection for
posterior elements of the
spine3,9,36.
Osteoblastoma and osteoid osteoma are similar histologically, and the
differential diagnosis is usually made on the basis of clinical and
radiographic evaluation. Characteristic lesions larger than 2 cm are typically
an osteoblastoma, lesions smaller than 1 cm are typically an osteoid osteoma,
and a gray area exists for lesions that measure between 1 and 2 cm. Osteoid
osteomas are benign latent lesions that spontaneously regress, whereas
osteoblastomas are benign but locally aggressive.
For many children and young adults, the natural history of an osteoid
osteoma lesion is for it to "burn out" over a period of years;
some advocate the use of nonsteroidal antiinflammatory drugs to treat lesions
in locations that are difficult to access surgically. In a comparison of
medical and surgical treatment, Kneisl and Simon reported that long-term
administration of nonsteroidal antiinflammatory drugs was as effective as
excision for the treatment of osteoid
osteoma43. Medical
treatment is often prolonged and associated with problems such as
gastrointestinal irritation or bleeding. Families are often unwilling to
accept this form of treatment, and surgery may be preferred.
Because of the benign, aggressive behavior of osteoblastoma lesions,
surgical treatment is indicated at diagnosis. Excision with extended,
intralesional curettage should be performed for most lesions. The entire nidus
is excised with use of a high-speed diamond bur and with the aid of a surgical
loupe and a headlamp. Fusion and instrumentation can provide stability if
spinal balance is jeopardized by removal of the lesion
(Figs. 7-A, 7-B, and 7-C). If
instrumentation is required, titanium instrumentation is recommended so that
high-quality postoperative computed tomographic or magnetic resonance images
can be acquired to detect
recurrence44.
For both lesions, improvement in the spinal deformity has been observed
following complete surgical removal. Ozaki et al. reported improvement of
scoliosis following resection of osteoid osteoma or osteoblastoma in sixteen
of seventeen
patients39. Other
evidence suggests that the duration of symptoms may be associated with the
probability of postoperative resolution of spinal deformity. Pettine and
Klassen reported that scoliosis improved or resolved following surgery in
eleven of twelve patients who had experienced symptoms for less than fifteen
months preoperatively, but in only one patient who had symptoms for more than
fifteen months9.
Aneurysmal Bone Cyst
Aneurysmal bone cysts are estimated to represent about 1.4% of primary bone
tumors45, and 3% to
20% of these lesions are located in the
spine45,46.
Most patients with an aneurysmal bone cyst present during the first two
decades of
life46,47.
Lesions demonstrate a predilection for the posterior elements of the vertebra
and the lumbar region of the
spine48-51.
Aneurysmal bone cysts may occasionally be seen in association with other bone
lesions, such as Langerhans cell histiocytosis, chondroblastoma, giant-cell
tumor, or osteosarcoma.
Plain radiographs demonstrate a characteristic expansile radiolucent
lesion. The posterior elements of the spine are most often affected (70% of
patients), and lesions can sometimes span two or three adjacent
vertebrae52.
Magnetic resonance imaging shows multiloculated, septated, expansile lesions
with fluid-fluid levels that produce a low-intensity signal on T1 images and a
high-intensity signal on T2 images. Computed tomography scans are also useful
in determining the extent of vertebral involvement. Biopsy with intraoperative
frozen-section analysis should be performed to confirm the diagnosis prior to
surgical removal and reconstruction and is usually done during the same
surgery.
The natural history of aneurysmal bone cyst is that of a benign but locally
aggressive
lesion49.
Traditional treatment has consisted of intralesional curettage and
bone-grafting, and recurrence rates of 10% to 60% have been
reported49,50,52,53.
To lower the risk of recurrence, following intraoperative frozen-section
analysis and histologic confirmation of an aneurysmal bone cyst, we recommend
treatment with a four-step approach consisting of (1) intralesional curettage,
(2) cauterization of the osseous cyst wall, (3) extended curettage with use of
a high-speed diamond bur, and (4) dilute (5%) phenolization (with care taken
to avoid contact with the dura and/or great vessels). Lesions treated with the
four-step approach had a significantly reduced rate of recurrence (zero of
eight patients) compared with simple intralesional curettage and bone-grafting
(four of four
patients)48.
Selective arterial embolization may be used as an adjunct to surgical excision
preoperatively to reduce intraoperative bleeding during the
excision54. After
surgical removal, titanium instrumentation and fusion may be necessary to
maintain or reestablish spinal stability
(Figs. 8-A, 8-B, and 8-C).
Hemangioma
Symptomatic hemangioma of bone is relatively uncommon and accounts for less
than 1% of all primary bone
lesions55. However,
the spine is one of the most commonly affected locations within the skeleton,
representing about 28% of all skeletal
hemangiomas56.
Hemangioma demonstrates a predilection for the thoracic spine and the anterior
elements57.
Children usually present with pain, and neurologic symptoms are uncommon.
Asymptomatic lesions may be discovered incidentally on imaging studies.
On plain radiographs, hemangioma is characterized either by vertical
striations or by multiloculated lytic foci. Thickened trabeculae appear as
coarse vertical and horizontal striations on the computed tomography scan.
Lesions produce a high-intensity signal on T1 and T2-weighted magnetic
resonance images (Fig.
9)58.
Asymptomatic lesions discovered incidentally should be monitored to confirm
the diagnosis and to look for signs of progression. The natural history of
hemangioma is gradual resolution, but symptomatic lesions may require
treatment in some
patients57,59.
Low-dose radiation has been used in the
past57,59,
but it is not an ideal option for children because of the risk of sarcoma
secondary to treatment. When management is indicated, selective arterial
embolization is often the treatment of choice.
Giant-Cell Tumors
Giant-cell tumors represent about 5% of all primary bone
tumors60, and
vertebral lesions are rare, particularly in
children61.
Giant-cell tumors are usually not seen until the third or fourth decade of
life. Pain, localized swelling, and tenderness are the most common presenting
symptoms, although cord compression may also occur, producing neurologic signs
or symptoms.
Most giant-cell tumors are benign but locally aggressive (classified as
Enneking stage 2 or 3). The lesion usually involves the vertebral body. Plain
radiographs may show the area of focal destruction as a radiolucent zone with
little or no cortical margin, but, as with all spinal lesions, this may be
difficult to assess on plain radiographs. Both computed tomography and
magnetic resonance imaging are important in preoperative
staging62.
Radiography of the chest should be done to rule out pulmonary metastatic
lesions, which have been reported in 1% to 9% of patients with giant-cell
tumor63-65.
Children with giant-cell tumors should be managed surgically. The risk of
recurrence has been reported to be as high as
80%66, and marginal
or wide resection of the lesion is recommended when possible. Due to the
spinal location, four-step extended curettage may be necessary. When
instrumentation is needed to maintain or provide stability following
resection, titanium instrumentation should be used because it will reduce the
artifact on subsequent imaging
studies44. It is
necessary to perform routine postoperative monitoring to detect local
recurrence or pulmonary metastasis.
Osteochondroma
Osteochondroma, also referred to as osteocartilaginous exostosis, is the
most common bone tumor in children and adolescents. Although this lesion is
uncommon in the spine, it warrants consideration as a cause of back pain in
children, especially those with multiple hereditary exostoses. There is
conflicting evidence about whether spinal osteochondroma is more often
solitary or associated with multiple hereditary exostoses. Some authors have
reported that solitary osteochondroma accounts for as much as 75% of all
spinal
exostoses67-70,
while other authors have reported that more than half of all osteochondroma
lesions of the spine are seen in patients with multiple hereditary
exostoses71,72.
Unlike many other lesions of the spine, spinal osteochondroma is often
painless, and patients often present with neurologic signs or symptoms caused
by spinal-cord or nerveroot
compression73-77.
Although spinal deformity is not often seen, scoliosis resulting from a
vertebral osteochondroma has been
described71,75,78.
Both solitary lesions and lesions in children with multiple hereditary
exostoses are more likely to be found in the cervical spine than in the
thoracic or lumbar regions. It is important to keep spinal osteochondroma in
mind in the differential diagnosis for a patient with multiple hereditary
exostoses and back pain or for the patient who has neurologic signs or
symptoms (Fig. 10).
The natural history of osteochondroma of the spine is slow growth of the
lesion until skeletal maturity. Occasionally, lesions regress during the
course of childhood and puberty. In patients who present with neurologic signs
or symptoms, excision of the tumor usually results in rapid recovery with a
very low risk of recurrence.
Malignant Tumors of the Spine
Ewing Sarcoma
Ewing sarcoma is the most common primary malignant bone tumor seen in the
spine of children. Between 3.5% and 10% of all cases of Ewing sarcoma
originate in the
spine79,80,
and approximately 75% of all cases of Ewing sarcoma occur in children between
the ages of five and fifteen
years81. Lesions of
the sacrum are most frequently seen, followed by thoracic and lumbar lesions,
whereas cervical lesions are
uncommon80. The
onset of symptoms may be gradual and may result in a delayed diagnosis. In a
series of 344 patients with Ewing sarcoma, Venkateswaran et al. reported that
the most common presenting symptoms were pain (seen in thirty-two patients,
[9%]) and neurologic deficit (thirty-one patients,
[9%])80. A large
soft-tissue mass is usually present and may be tender when palpated. Some
patients may appear constitutionally ill and may report symptoms such as fever
and weight loss. The erythrocyte sedimentation rate and the C-reactive protein
level are elevated in most children.
The characteristic radiographic feature of Ewing sarcoma in the long bones
is a lesion with a moth-eaten appearance, a large soft-tissue mass, and
aggressive periosteal new bone formation. Vertebral lesions, however, are not
always associated with these telltale plain radiographic signs. Vertebra plana
may be visible on plain films with an associated soft-tissue mass. Magnetic
resonance imaging is most helpful for evaluating soft-tissue involvement and
detecting extradural canal-space impingement
(Figs. 11-A and 11-B).
After appropriate staging and biopsy, treatment includes neoadjuvant
chemotherapy, local control with radiation or surgery or both, and additional
postoperative chemotherapy. Metastatic disease may be present in as many as
25% of patients at the time of presentation and is most frequently found in
the lungs, other bones, lymph nodes, brain, and the abdominal
viscera80,82.
Osteogenic Sarcoma
Osteogenic sarcoma is the most common primary malignant bone tumor
(although Ewing sarcoma is more often seen in the spine). About 5% of all
osteogenic sarcomas are primary vertebral lesions, more often localized in the
thoracic or lumbar
spine83. Most
children who are diagnosed with osteogenic sarcoma are between ten and twenty
years of age19.
Patients usually present with pain or soft-tissue swelling, and up to 40% have
neurologic
abnormalities83.
Plain radiographs of children with osteosarcoma may show a radiolucent,
radiodense, or mixed radiolucent-radio-dense and destructive lesion. Lesions
are best defined with magnetic resonance imaging: the osseous component of the
tumor is associated with a low-intensity signal on T1 and T2-weighted images
while the soft-tissue mass produces a high-intensity signal. In a series of
forty-five patients with osteosarcoma, Ilaslan et al. reported that an
associated soft-tissue mass invading the spinal canal was detected in
thirty-eight patients
(84%)83.
After biopsy, neoadjuvant chemotherapy is given to address the primary
tumor and any existing macrometastatic lesions and to eliminate
micrometastatic lesions. Surgery for local control is appropriate when
resection with wide margins can be achieved safely. Pulmonary metastatic
lesions are common and may also require surgery for treatment. The combination
of chemotherapy and local-control surgery has improved the survival rates of
children with osteogenic
sarcoma82,84.
Leukemia
Leukemia is the most prevalent form of cancer in young children: peak
incidences have been noted in patients between two and five years of age and
in patients between fifteen and twenty years. However, the diagnosis can be
challenging because any organ system can be affected. The skeleton is often
the first body system to demonstrate manifestations of the acute form of
leukemia, and bone pain may be the presenting symptom in up to 25% of
patients85.
Constitutional symptoms, including lethargy, fever, and anemia, are often
present. Elevations in the complete blood count, the erythrocyte sedimentation
rate, and the white blood-cell count, a lowered platelet count, and an
increased peripheral leukocyte count are characteristic of leukemia.
Plain radiographs often do not help in forming a definitive diagnosis.
Vertebral lesions associated with leukemia are variable in appearance: diffuse
osteopenia, osteosclerosis, osteolysis, mixed osteolysis and sclerosis,
periosteal new bone formation, and permeative destruction have all been noted
on plain radiographs of children with
leukemia85. Other
radiographic findings in children with leukemia include pathologic fractures,
which occur in 10% to 15% of children, and vertebral collapse, seen in about
6%86,87.
Treatment strategies are specific to the type of leukemia involved and
usually include chemotherapy and/or radiation.
Metastatic Invasion of the Spine in Children
Possible metastasis to the spine can occur as a consequence of
rhabdomyosarcoma, neuroblastoma, and, less often, Wilms tumor, lymphoma, and
teratoma81. Most
children with metastasis to the spine initially present with a pathologic
fracture (micro or macrofracture), and some present with spinal cord
compression. Neurologic signs and symptoms are rarely seen.
The definitive diagnosis of metastatic disease of the spine is made on the
basis of the results of biopsy. Treatment options are specific to the type of
lesion involved.
Staging
Classification systems for spinal tumors include those according to
Enneking88
(Fig. 12-A), Weinstein,
Boriani, and
Biagini62
(Fig. 12-B), and Tomita et al.
89
(Fig. 12-C). The Enneking
classification system for malignant tumors of the musculoskeletal system is a
general system that can be used to describe spinal tumors on the basis of the
consideration of three factors, evaluated clinically, radiographically, and
histologically: grade, which indicates the histologic pattern; site, which
describes whether the lesion is intracompartmental or extracompartmental; and
metastatic disease, which is either present or
absent88.
Weinstein, Boriani, and Biagini proposed an approach to surgical staging that
was based on the extent of vertebral involvement as described by a system of
zones and layers. The vertebrae are divided into twelve radiating zones in the
transverse plane (numbered sequentially in a clockwise direction) and five
layers (lettered sequentially from A through E from prevertebral to dural
involvement)62. In
1997, Tomita et al. proposed a two-part numeric classification system that
incorporated a denotation of tumor location in the spine along with a
simplified scheme for describing the extent of vertebral involvement. The
first number ranges from 1 (vertebral body) to 5 (paravertebral area). The
second number ranges from 1 to 7: lesions of types 1 through 3 are
intracompartmental lesions, types 4 through 6 are extracompartmental lesions,
and type 7 lesions are multiple skip
lesions89.
Surgical Treatment
Infection
Surgical management is rarely indicated for children with disc-space
infection; medical management with antibiotics, accompanied by bracing when
appropriate, is safe and effective treatment for most infections. For
vertebral osteomyelitis, surgical decompression of purulent material is
indicated for more advanced infections. Surgical intervention may also be
necessary when there is a neurologic deficit due to spinal cord compression,
appreciable destruction of vertebral bodies, rapidly progressing deformity, or
when nonoperative management is unsuccessful. When there is evidence of spinal
cord compression, decompression is indicated. Most often, an anterior approach
is used to facilitate access to the infected
region90.
Occasionally, instrumentation may be needed to provide stability and to
minimize the risk of future deformity.
Tumors
Lesions in the pediatric spine are often more challenging to treat than
lesions of similar behavior elsewhere in the musculoskeletal system.
Slow-growing but locally aggressive tumors that may be easily treated
elsewhere may be unresectable and potentially lethal in certain locations in
the spine. The surgical approach should be planned and must achieve
appropriate margins. Intralesional excision is generally a piecewise removal
of the tumor, and en bloc resection can be performed by means of marginal
excision (along the pseudocapsule) or wide excision (outside the
pseudocapsule). While intralesional removal may be associated with excellent
outcomes for many patients with benign tumors and benign but locally
aggressive tumors, more aggressive surgery is indicated for some locally
aggressive benign tumors and many malignant
tumors91.
Nonmetastatic malignant tumors are ideally removed with wide surgical margins
if the goal is to render the patient "cancer free."
Benign Tumors: Benign latent lesions have benign histology, remain
intracompartmental and encapsulated, and do not result in metastatic disease.
Treatment depends on entity, natural history, location, and size of the
lesion. Benign active lesions have similar characteristics but actively
enlarge within their natural boundaries and are more likely to produce
symptoms. Adequate intralesional excision usually can be performed with a low
rate of recurrence for these tumors. Benign aggressive spinal lesions exhibit
benign histologic features, but, unlike other benign tumors, the lesions are
often extracapsular and may extend across compartmental boundaries. En bloc
excision with wide margins (when possible) is often indicated for benign
aggressive lesions. Adjuvant therapy may be necessary on occasion.
Malignant Tumors: Advances in chemotherapy and techniques for
resection and reconstruction have expanded the role of local surgical
management in the treatment of children with malignant spinal tumors.
Management of spinal tumors is complex and requires a multidisciplinary
approach. The Enneking classification helps to delineate the progressive
stages of a tumor and the specific implications for surgical treatment and
provides guidelines for the use of adjuvant therapy. The goal for resection of
malignant tumors is complete removal of the lesion while maintaining or
reestablishing neurologic function and/or stability in the vertebral column.
For radiation-sensitive spinal tumors, such as a Ewing sarcoma, radiation may
be appropriate for local control, especially in the setting of multiple
metastases.
The primary factors in determining the optimal surgical approach are:
Specific diagnosis and behavior of the lesionPresence or absence of metastatic diseaseLocationExtent of the lesion
Specific diagnosis and behavior of the lesion
Presence or absence of metastatic disease
Location
Extent of the lesion
A well-planned and complete resection of the malignant lesion can achieve
local control and improve survival. However, the proximity of the tumor to
spinal cord and/or nerve roots often precludes the possibility of wide
excision. Surgical options include vertebrectomy or partial vertebrectomy.
Vertebrectomy implies removal of the entire vertebra and is achieved through a
posterior approach or a combined anterior and posterior
approach92.
Hemivertebrectomy involves resection of a portion of the vertebra.
Lesions involving the posterior elements of the spine should be approached
posteriorly for removal and
reconstruction92.
An anterior approach is recommended for malignant spinal tumors involving the
anterior body or for tumors without an associated soft-tissue mass. An
anterior approach is not recommended when the pedicle of the vertebral body is
involved92. Often,
a combined anterior and posterior approach is used, often simultaneously. If
the anterior and posterior elements of the vertebra are affected by a
malignant osseous lesion, an en bloc approach, preferably with wide margins,
is indicated. While some lesions that involve both anterior and posterior
elements in the thoracic or lumbar spine can be resected through a posterior
or posterolateral approach alone, most surgeons prefer a combined anterior and
posterior
approach89.
Amputation for malignant spinal tumors is typically performed only for the
treatment of lesions of the sacral spine or, occasionally, the lumbosacral
spine. The procedure, known as a hemicorporectomy, is cosmetically deforming
and used only in rare circumstances.
Stabilization with instrumentation and fusion is often necessary following
resection of a vertebral lesion. Destabilizing resection requires
instrumentation placed at least one to two vertebrae cephalad and caudad to
the lesion. If anterior reconstruction is indicated, structural autograft,
allograft, a cage, or a combination of these may be used. The use of titanium
instrumentation allows for better computed tomographic and magnetic resonance
images with less artifact, making early detection of recurrences
possible44.
Although spinal tumors and infection are uncommon in children, a high index
of suspicion should be maintained when evaluating a child who presents with
back pain. Pain is the most common presenting complaint for nearly all of the
infections and tumors seen in the pediatric spine. A thorough understanding of
the characteristic clinical and radiographic presentations of these conditions
in children can facilitate a timely diagnosis and lead to early intervention,
better outcomes, and decreased mortality for children with spinal tumors and
infection. ?