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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6011_Библиотеки_им_академика_М_И_Перельмана.pdf
C H A P T E R 4 6 Tumors of the oracic Spine
295
A
B
F I G UR E 4 6- 7 Sagittal (A) and Axial (B) CT images of the spine demonstrating a lytic destructive process at T9-10,
with associated large right paraspinal mass (myeloma). Note that despite the significant destruction of the bone, there is no
deformity of the spine.
SURGICAL TECHNIQUE
e patient was placed in the left lateral decubitus position to allow access
to the right thoracoabdominal region and the posterior thoracolumbar spine.
e posterior thoracolumbar spine was exposed from T7 to L2. Pedicle
screws were placed at T7 to T8, and T11-L1. Only one screw could be placed
at L2, and in the lateral position, screws could not be successfully placed at
T6. A temporary rod was placed on the left side of the spine to stabilize the
spine during the decompression. T9 and T10 laminectomies were fashioned
and tumor in the epidural space was resected. A right thoracotomy incision
was fashioned over the 9th and 10th ribs and connected to the thoracolumbar
incision dorsally. A portion of the 9th and 10th ribs distal to the tumor was
resected. is allowed access to the pleural cavity. e 9th and 10th ribs were
disarticulated from the spine to allow the paraspinal component of the tumor
to be resected with the chest wall. Corpectomies of T9 and T10 were performed to resect the remaining tumor. e segment was reconstructed with
an expandable cage encompassing T8 to T11. A lateral plate was also placed
from T8 to T11. Final rods were placed posteriorly and bone grafting was
performed with allograft. Plastic surgery assisted with the closure and reconstruction of the chest wall.
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P A R T V I Other Surgical Treatment Modalities: Thoracic Spine
A
B
F IG U R E 4 6- 8 A, Sagittal and B, Axial T2-weighted images, demonstrating a mass (myeloma) at T9-10 with epidural
spinal cord compression. Note the extensive paraspinal component of the mass.
POSTOPERATIVE COURSE
e patient remained at his neurological baseline postoperatively. His pathology again confirmed the diagnosis of multiple myeloma. His postoperative
course was complicated by a prolonged air leak requiring a chest tube. He
was discharged on postoperative day 17. Postoperative imaging showed good
position of the instrumentation (Figure 46-9). At 2.5 years post surgery he
remains neurologically intact with an intact construct. He has had skeletal
progression of the myeloma to stage III.
DISCUSSION
Metasatic tumors are the most common neoplasms affecting the thoracic
spine. Based on the work of Patchell et al surgery followed by radiation
therapy has replaced radiation therapy alone as the gold standard for treatment of MESCC. Extremely radiation-sensitive tumors include small cell
lung carcinoma, lymphoma, and multiple myeloma. For these lesions, radiation therapy may still be employed as a first-line treatment modality for
MESCC. The surgical approach may be anterior, posterior, or combined
anterior/posterior. En bloc spondylectomy may be employed specifically for certain locally aggressive primary spinal column neoplasms. Prior
to embarking on treatment, it is important to know the tumor histology.
Therefore, CT-guided biopsy is recommended in patients who have stable
or preserved neurological function. Tumor history, tumor location, anatomy
of spinal disease, extent of systemic disease/medical comorbidities, and vertebral column compromise are factors that dictate the surgical approach.
Thoracic spinal column neoplasms require reconstruction with instrumentation, with the exception of IMSCTs and some IDEM tumors. The clinical
goals of surgery for thoracic spinal column neoplasms include local disease
control, preservation or restoration of neurological function, stabilization of
the spinal column, and pain control.
C H A P T E R 4 6 Tumors of the oracic Spine
297
A
B
F IG U R E 4 6 -9 Sagittal, coronal, axial, and scouts views, status post resection and reconstruction with instrumenta-
tion via a combined anterior and posterior approach.
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P A R T V I Other Surgical Treatment Modalities: Thoracic Spine
Case 4: En Bloc
PATIENT PRESENTATION
A 67-year-old male with a history of prostate cancer treated with resection and thought to be in remission presented with upper lumbar/lower
thoracic and right paraspinal pain. Associated symptoms included local
numbness and paresthesias and more recent numbness and paresthesias
in his feet. An MRI of the thoracic and lumbar spine (Figure 46-10) was
performed with and without contrast as well as plain films. e plain films
did not demonstrate evidence of bony changes; however, MRI showed a
T2-hyperintense and contrast-enhancing lesion at T10 with epidural
extension and spinal cord compression. Although the patient had some
mild myelopathic signs on exam (hypereflexia), his motor exam was normal and his gait and sphincter function were both normal. e differential
diagnosis included chordoma, given the T2 hyperintensity that is typical of
this lesion. Also included on the list was metastatic disease, with prostate
being the highest possibility on the list given his previous history. Because
chordoma was on the list, representing a locally aggressive tumor that is
rarely cured with intralesional resection alone, a CT-guided biopsy was recommended through a posterior approach to confirm the pathology prior to
recommending further treatment. e report confirmed a chordoma. An
en bloc surgical resection was recommended. An all-posterior approach
was recommended with the caveat that if en bloc resection could not be
achieved in this fashion, the posterior resection of the posterior elements
at T10 would be followed by a thoracotomy with anterior en bloc vertebral
body resection.
SURGICAL TECHNIQUE
e patient was positioned prone on the Jackson table. e posterior
spine was exposed from T7 to T12. e surgical plan was to stop the
construct at T12/the thoracolumbar (TL) junction. Although stopping
a construct at a junctional level may not be ideal, the authors feel that
when this is done with a construct ending on the superior side of the TL
junction, it is better tolerated than ending on the inferior side of the TL
junction. However, there is no solid data to support this clinical belief. We
also felt that ending at T7 was high enough above the apex of the patient’s
thoracic kyphosis, which we estimated to be at T8-9 or T9-10 based on
the imaging. Pedicle screws were therefore placed at T7-T9 and T11-T12
bilaterally. Laminectomies at T9 and T11 were subsequently fashioned.
Two Tomita saws were then placed between the lamina of T10 and the
dura at the junction with the facet joint. Using the Tomita saws, the spinous process and bilateral lamina of T10 were removed in en bloc fashion.
Using silk ligatures to prevent a CSF leak, the bilateral T9 and T10 nerve
AA
B
B
C
F IG U R E 4 6- 10 A, Sagittal and B, Axial T2-weighted MRI of the thoracic spine demonstrating a high-signal-intensity
lesion at T10 (chordoma) with epidural spinal cord compression. T1-weighted postcontrast and precontrast images (c) dem-
onstrate enhancement of the lesion.
C H A P T E R 4 6 Tumors of the oracic Spine
299
A
B
C
F IG U R E 46 -1 1 Intraoperative photographs. A, Posterior spinal hardware and the bilateral lung fields adjacent to the
spinal cord at the spondylectomy site. B, Anteriorly-placed distractible cage at the site of the en bloc spondylectomy. C, Gross
pathological specimen of the T10 en bloc spondylectomy. Note the epidural tumor capsule posterior to the vertebral body.
roots were ligated proximal to the dorsal root ganglion. e nerve roots
typically have to be sectioned at one or two levels to deliver the vertebral
body posteriorly in an en bloc spondylectomy. It is felt that sectioning
the roots proximal to the dorsal root ganglion decreases the possibility
of postoperative neuropathic radicular pain. e thecal sac was carefully
F IG UR E 4 6- 12 Postoperative AP and lateral x-rays
of the thoracic spine demonstrating the reconstruction.
dissected from the anterolaterally situated epidural tumor. e paraspinal
muscles were dissected off of the rib cage and retracted medially with Penrose drains. e bilateral T10 ribs were then resected from 1 cm distal to
the costotransverse junction to 5 cm distal to that point. e pleura was
opened and a chest spreader was placed, first on the left and then on the
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P A R T V I Other Surgical Treatment Modalities: Thoracic Spine
right. e lung was retracted away from the field and the vessels (aorta
and vena cava) were dissected off the pleura and T9 and T10 vertebral
bodies in a circumferential fashion. Both T9 and T10 segmental vessels
were ligated bilaterally. Rods were then attached to the screw heads from
T7 through T12. Using Tomita saws, the midvertebral body of T9 was
transected, as was the T10-T11 disc space. is completely mobilized
the specimen. e specimen was then removed posterolaterally in en bloc
fashion (Figure 46-11). A distractible cage was placed from T9 to T11.
Bone grafting was done with allograft. Neurological monitoring remained
stable throughout the case.
References
1. T.F. Witham, et al., Surgery insight: current management of epidural spinal cord compression
from metastatic spine disease, Nat. Clin. Pract. Neurol. 2 (2) (2006) 87–94.
2. M. Bilsky, Metastatic tumors of the spine and spinal cord, in: C.A. Dickman, M.G. Fehlings,
Z.L. Gokaslan (Eds.), Spinal Cord and Spinal Column Tumors, Thieme, New York, 2005.
3. R.A. Patchell, et al., Direct decompressive surgical resection in the treatment of spinal cord
compression caused by metastatic cancer: a randomised trial, Lancet 366 (9486) (2005)
643–648.
4. P.C. McCormick, BB: Spinal tumors, in: L.C., R.G. Grossman (Eds.), Principles of neurosurgery, Lippincott-Raven, Philadelphia, 1999.
5. S.J. Hentschel, M.I., Intradural extramedullary spinal tumors, in: M.G. Fehlings, C.A. Dickman, Z.L. Gokaslan (Eds.), Spinal cord and spinal column tumors, Thieme, New York, 2005.
6. P.R. Cooper, H.K, Intramedullary spinal cord tumors, in:M.G. Fehlings, C.A. Dickman,
Z.L. Gokaslan (Eds.), Spinal cord and spinal column tumors, Thieme, New York, 2005.
7. W.B. Jacobs, F.M, Primary vertebral column tumors, in: M.G. Fehlings, C.A. Dickman, Z.L.
Gokaslan (Eds.), Spinal cord and spinal column tumors, Thieme, New York, 2005.
8. J.H. Chi, et al., Epidemiology and demographics for primary vertebral tumors, Neurosurg.
Clin. N. Am. 19 (1) (2008) 1–4.
POSTOPERATIVE COURSE
e patient was taken to the intensive care unit with preserved lower
extremity neurological function. He remained intubated until postoperative
day 1 when he was successfully extubated. Postoperative imaging disclosed
good position of his cage and posterior screws (Figure 46-12). His postoperative course was complicated by new-onset atrial fibrillation. His chest
tubes were discontinued on postoperative days 5 and 6 respectively. He was
discharged on postoperative day 8. At 3 months after surgery, he was off
narcotics and returned to work. Proton beam irradiation was scheduled.
9. A. Mantha, et al., A novel rat model for the study of intraosseous metastatic spine cancer,
J Neurosurg. Spine 2 (3) (2005) 303–307.
10. C.A. Bagley, et al., Fractionated, single-port radiotherapy delays paresis in a metastatic spinal
tumor model in rats, J. Neurosurg. Spine 7 (3) (2007) 323–327.
11. C.A. Bagley, et al., Local delivery of oncogel delays paresis in rat metastatic spinal tumor
model, J. Neurosurg. Spine 7 (2) (2007) 194–198.
12. B. Gok, et al., Surgical resection plus adjuvant radiotherapy is superior to surgery or radiotherapy alone in the prevention of neurological decline in a rat metastatic spinal tumor model,
Neurosurgery 63 (2) (2008) 346–351.
13. W.A. Pennant, et al., Microsurgical removal of intramedullary spinal cord gliomas in a rat
spinal cord decreases onset to paresis, an animal model for intramedullary tumor treatment,
Childs Nerv. Syst. 24 (8) (2008) 901–907.
14. J. Schuster, J. Zhang, M. Longo, A novel human osteoblast-derived severe combined immunodeficiency mouse model of bone metastasis, J Neurosurg. Spine 4 (5) (2006) 388–391.
15. D.R. Fourney, Z.L. Gokaslan, Use of “MAPs” for determining the optimal surgical approach
to metastatic disease of the thoracolumbar spine: anterior, posterior, or combined: invited
submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves,
March 2004, J. Neurosurg. Spine 2 (1) (2005) 40–49.
Infections of the Thoracic Spine
Daniel J. Hoh and Michael Y. Wang
47
k e y p o i n t s
e incidence of reported spinal infections is increasing, which is likely to
be related to a growing elderly population that is living longer with chronic
disease and undergoing more spinal procedures.
Spinal infections are of significant concern, as they can cause pathologic
fractures, instability, loss of spinal alignment, and neural compression
resulting in pain, deformity, and neurological deficit.
Improved diagnostic and therapeutic modalities are available that make
possible earlier identification of the pathologic organism, initiation of
appropriate pharmacotherapy, and better eradication of infection with less
recurrence.
e indications for surgical intervention are to identify the pathologic
organism, prevent neurological deterioration, restore spinal alignment,
maintain stability, and treat disabling pain. A variety of surgical approaches
are available including anterior, posterior, and circumferential techniques.
Decision-making regarding surgical approach is dependent on extent of
disease, need for spinal reconstruction and stabilization, and the patient’s
overall surgical risk.
Advances in surgical technique, instrumentation, and biomedical technology
are improving operative treatment of spinal infections. Recent developments
include the increasingly safe use of titanium-based implants, alternative graft
options, and the introduction of minimally invasive spinal surgery. Prognosis
for patients with spinal infections is improving as a result of these advances in
diagnostic, medical, and surgical modalities.
INTRODUCTION
The last several decades have witnessed a rise in reported spinal infections.
This increase has largely been attributed to factors associated with a growing
elderly population. Improvements in medical care have directly resulted in
prolonged life expectancy with more individuals living longer with chronic
diseases. As a result, various medical conditions associated with advanced
age, such as diabetes or illnesses that lead to immunocompromise, predispose patients to developing spinal infections. Additionally, as individuals are
living longer, more elderly patients are seeking to undergo spinal procedures
for degenerative conditions that otherwise, left untreated, result in debilitating pain. Both minor procedures such as discography and epidural injections and extensive spinal fusion surgeries pose the risk of direct bacterial
inoculation of the spine.
Infections of the spine are characterized either by their microbiology or
by the location of pathology. From a microbiology standpoint, spinal infections are differentiated by pyogenic or granulomatous etiologies. Pyogenic
infections are generally of bacterial origin. Granulomatous spinal infections
encompass fungal etiologies, but include some bacterial sources, and refer
primarily to the histologic course of the infection. Spinal tuberculosis is by
far the most common of the granulomatous spinal infections worldwide.
Spinal infections are also classified by the primary location of pathogenesis. Sole involvement of the disc space is referred to as discitis. Osteomyelitis is an infection of the bony spine (Figure 47-1). Osteodiscitis or
spondylodiscitis is combined involvement of the intervertebral disc and the
vertebra. Abscess or granulation formation can occur in a subdural, epidural,
or paravertebral location (Figure 47-2). Frequently, spinal infections invade
all compartments of the spinal column, including the soft tissues, bony
spine, and within the spinal canal.
Spinal osteomyelitis is estimated to occur in 1 in 100,000 to 250,000,
and accounts for 2% to 7% of all cases of osteomyelitis. Spinal osteomyelitis
occurs more commonly among older individuals, with approximately one
half of all patients being over 50 years of age. Similarly, epidural abscesses
occur in adults and are estimated to occur in 0.2 to 1.2 per 10,000 hospital admissions annually. When bacterial spinal infections occur in younger
individuals, they are more commonly seen in intravenous drug users. Both
osteomyelitis and epidural abscesses generally occur in the thoracic and
lumbar spine, with thoracic infections representing over a third to half of
all cases, and lumbar infections accounting for a majority of the remainder.
Cervical spine infections are estimated to account for only 5% to 14% of
all cases.
Outside the United States, spinal tuberculosis still represents a considerable health care problem. Tuberculosis is relatively common in underdeveloped countries where malnutrition and overcrowding are present. It is
estimated that 2 billion people have tuberculosis worldwide, with 9 million new cases each year. Approximately 5% of these patients have spinal
involvement. Spinal tuberculosis is a major source of morbidity, representing the most common cause of nontraumatic paraplegia in underdeveloped
countries.
While the incidence of spinal infections is increasing, management
of these conditions is also dramatically evolving. Earlier detection, better
screening and surveillance, and advanced imaging modalities have improved
diagnosis of spinal infections and identification of pathogenic organisms.
More effective antimicrobial pharmacotherapy has led to better medical
treatment with clearance of infection and less recurrence. Surgical treatment
options have incorporated advances in surgical technique, instrumentation,
and biomedical technology to increase eradication of infection, preservation
of neurological function, restoration of spinal alignment, and prevention of
deformity and chronic pain.
PATHOPHYSIOLOGY
The pathophysiology of spinal infection ultimately begins with the individual’s underlying predisposing risk factors. Advanced age, diabetes, and
multiple medical comorbidities are associated with increased risk for
spinal infection. Additionally, spinal surgery, intravenous drug use, and
immunocompromise contribute to further risk. Infection generally metastasizes hematogenously to the spine from extraspinal sources such as the
urinary tract, respiratory system, skin or soft tissue infections, or cardiac
vegetations. Direct inoculation from surgery, percutaneous procedures, or
penetrating trauma is an additional modality for bacterial seeding. Local
invasion to the spine also occurs from infected adjacent or contiguous
sources such as the retroperitoneal, abdominopelvic, pleural, or retropharyngeal spaces. Spread of infection can also occur within the spinal
column by direct extension from the bony or soft tissue elements to the
epidural space.
301
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P A R T V I Other Surgical Treatment Modalities: Thoracic Spine
F IG UR E 47 -1 T1-weighted sagittal MRI after administration of intra-
venous gadolinium in the same patient, demonstrating abnormal enhancement. The osteodiscitis at the lower thoracic region has an associated epidural
abscess causing ventral spinal cord compression.
F IG UR E 47 -2 T1-weighted sagittal MRI with gadolinium of the lum-
bar spine in a different patient, demonstrating the ring-enhancing contrast pattern of an epidural abscess.
F IG UR E 4 7 -3 T2-weighted sagittal MRI in a 64-year-old male with
subacute osteodiscitis. Advanced bone loss and significant subchondral destruction has created a severe local kyphosis at the affected level.
Bacterial Pathogenesis
Hematogenous seeding of the spine may occur via either arterial or venous
pathways. The venous plexi that drain from within the spinal canal communicate with plexi that form a venous ring around each vertebral body. This
venous system communicates with the venous drainage of the pelvis. Batson
demonstrated that this venous pathway is a valveless system in which microorganisms may circulate and lodge in the low-flow end-organ vasculature
surrounding the vertebral body. Alternatively, direct bacterial seeding of the
vertebral body may occur from ascending and descending arterial branches
that send penetrating vessels to the vertebral body.
Pathologic sequelae of spinal infection include loss of spinal alignment
with progressive deformity, and risk of neurological compromise. Bacterial
involvement of the spinal column with subsequent inflammatory infiltration causes bony destruction and eventually erodes the subchondral plate
to involve the relatively avascular disc space (Figure 47-3). Advanced bone
loss, particularly across multiple adjacent segments, combined with disc
space narrowing, leads to progressive kyphotic deformity. neurological compromise may result from severe bony destruction, resulting in pathologic
fracture with retropulsed bony fragments into the canal. Epidural abscess
formation or extension of inflammatory granulation tissue into the canal
can cause direct compression of the spinal cord or nerve roots. Additionally,
septic thrombosis of veins within the epidural space or the arteriolar supply
can cause ischemic injury. Particularly, in a spinal cord already compromised
by mechanical compression from either an abscess or fracture, hypoperfusion from thrombosed feeding arteries or draining veins may lead to rapid
neurological deterioration.
Gram-positive cocci are the most prevalent inciting organism, representing 50% to 67% of all causative organisms. Staphylococcus aureus is
the most prevalent bacteria identified, accounting for 80% of all grampositive infections, and 55% of all spinal infections. In a meta-analysis of
915 patients with epidural abscess, S. aureus was identified as the causative
organism in 73.2% of cases. Gram-negative bacteria, particularly Esch-
erichia coli and Proteus, are more frequently identified in patients with preexisting urinary tract infections. Pseudomonas aeruginosa is most common
F IG UR E 4 7 -4 T2-weighted sagittal MRI of the lumbar spine in a
58-year-old woman with spinal tuberculosis, showing fracture of L1, retropulsed fragments in the canal, and neural compression.
among immunocompromised patients or intravenous drug users. Indolent
infections are more likely to occur with low-virulence organisms such as
Streptococcus viridans or Staphylococcus epidermisdis.
Pathogenesis of Tuberculosis
Tuberculosis of the spine results from hematogenous spread of Mycobacterium tuberculosis from well-established extraspinal foci, primarily originating
from the respiratory or genitourinary tract. Unlike pyogenic osteomyelitis,
spinal tuberculosis may begin in the paradiscal area and spread under the
anterior longitudinal ligament to involve adjacent vertebral bodies, while relatively preserving the disc space. Additionally, spinal tuberculosis frequently
involves the posterior spinal arch, whereas pyogenic osteomyelitis is primarily a disease of only the anterior spinal column. Because spinal tuberculosis
often causes widespread destruction of a spinal segment, vertebral collapse
with pathologic subluxation, kyphosis, and retropulsion occur in severe
cases and present greater risk for acute neurological compromise than bacterial osteomyelitis (Figure 47-4). Delayed chronic paresis also occurs with
progressive deformity or in the setting of epidural granulomas that result
from longstanding tuberculous infection.
CLINICAL PRESENTATION
The clinical presentation of bacterial spinal infections often depends on the
virulence of the organism, the duration of infection, and the overall integrity
of the patient’s immune system. Improved diagnostic modalities have led to
earlier detection of disease, with initiation of appropriate medical therapy
often before patients develop systemic illness or potentially irreversible neurological compromise. Over 90% of patients with pyogenic osteomyelitis
present with axial neck or back pain as the primary complaint. The pain is
generally characterized as insidious and nonmechanical in nature, and unrelieved by recumbency. Patients frequently note local spine tenderness with
limited range of motion. Constitutional symptoms associated with infection
such as fevers, chills, and malaise may also be present: however, an elevated
temperature is only found in 52% of patients at time of presentation.
C H A P T E R 4 7 Infections of the oracic Spine
303
Neurological findings are less common with pyogenic osteomyelitis.
A review of the literature reveals that only 17% of patients with bacterial
osteomyelitis have neurological signs or symptoms on initial presentation.
Alternatively, neurological complaints are frequently associated with acute
bacterial epidural abscess, with 56% of patients presenting with motor deficits, and 36% with radicular pain. The clinical triad of localized spine pain,
fever, and progressive neurological deficit is seen, however, in only 36% of
patients with epidural abscess.
Spinal tuberculosis has a similar presentation to bacterial osteomyelitis,
with most presenting with spine pain and localized tenderness. Unlike bacterial osteomyelitis, however, patients with tuberculosis present with a more
insidious course. A mean duration of symptoms prior to diagnosis is 6.1
months. neurological deficits at the time of presentation are also more prevalent with tuberculosis, with 44.9% of patients having neurological findings.
Motor function abnormalities are present in 34.6% of patients with spinal
tuberculosis, with 6.4% being paraplegic at time of presentation.
DIAGNOSTIC EVALUATION
The initial evaluation of a patient suspected of spinal infection includes
standard serologic markers for infection or inflammation. A basic panel
includes peripheral white blood cell count (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). WBC is elevated at time
of presentation, however, in only 42% of cases, and often normalizes in
patients with chronic infection. ESR and CRP are markers of inflammation
and demonstrate high sensitivity for spinal infection. CRP, an acute phase
protein, increases within 4 to 6 hours of infection. ESR begins to increase
only several days after the onset of infection and peaks at 7 to 8 days. ESR
is elevated in over 90% of patients with spinal infection; however, ESR and
CRP lack specificity, and may be increased in patients either with infection
or with other inflammatory disorders. Individuals suspected of tuberculosis
are assessed with a PPD and subsequently sputum staining for acid-fast
bacilli.
Definitive diagnosis of spinal infection is made upon identifying the
causative organism from positive culture. Prompt blood and urine cultures
are obtained immediately on presentation, as infection commonly spreads
to the spine either from the genitourinary tract or hematogenously. Positive
blood cultures identify the inciting organism in 25% to 59% of cases. Ideally,
cultures are obtained prior to initiating antimicrobial therapy to obviate the
potential of a sterile nondiagnostic culture.
Biopsy of an abnormal spinal lesion can confirm the diagnosis of infection as well as isolate the inciting organism. Percutaneous closed biopsy is
performed using computed tomography (CT) or fluoroscopic guidance.
Closed biopsy demonstrates a reported accuracy of 70% to 100% in identifying the causative organism. Open surgical biopsy is indicated in the setting of a nondiagnostic closed biopsy in a patient with persistent clinical
infection or deterioration despite broad-spectrum medical therapy, or for
lesions inaccessible percutaneously. Open biopsy is diagnostic in over 80%
of patients, likely due to a larger bony sample. A high concordance rate is
observed in patients with both positive blood and biopsy specimens, reinforcing the importance of early blood culture sampling prior to initiating
antimicrobial pharmacotherapy.
Imaging
Plain spine x-rays may demonstrate characteristic findings associated with
osteomyelitis or osteodiscitis, and often serve as a rapid method for surveying the full spinal axis for potential infection. Disc space narrowing is the
earliest and most consistent radiographic finding, occurring in 74% of cases,
generally after approximately 2 to 4 weeks. Enlargement of the paravertebral
shadow may indirectly suggest a thoracic paravertebral abscess. After 3 to 6
weeks, leukocyte infiltration into the subchondral bone and vertebral body
leads to bony destructive changes, appearing as a lytic area in the anterior
aspect of the vertebral body adjacent to the disc, or blurring of the endplates.
With advanced bone loss, the vertebral body collapses. Thirty-six inch
standing x-rays are essential for assessing progression of sagittal and coronal
plane deformity in severe cases. With chronic disease (after 8 to 12 weeks),
reactive bone formation and endplate sclerosis occurs. Ultimately, the
reparative process results in new bone formation and hypertrophic changes.
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Eventually, 50% of cases lead to spontaneous fusion; however, it may require
several years for this to take place. The remaining cases likely form a fibrous
ankylosis which may similarly effectively immobilize the involved segment.
Radionuclide studies are capable of detecting and localizing infection
before abnormal findings are observed on plain radiographs. Gallium scanning demonstrates 89% sensitivity, 85% specificity, and 86% accuracy for
diagnosing disc space infections. Technetium scanning is 90% sensitive, 78%
specific, and 94% accurate. Combined gallium and technetium scanning is
reported to have 94% accuracy. SPECT is a sensitive bone scintigraphic
modality for early detection of osteomyelitis and is often performed in conjunction with technetium and gallium scanning.
CT imaging is beneficial for evaluating the extent of bony destruction.
Axial CT imaging demonstrates the presence of retropulsed fragments and
the degree of canal compromise in the setting of pathologic fracture. Sagittal reconstructed CT imaging may reveal endplate osteopenia as an early
finding of infection. Superb detailing of bony anatomy may be useful for
preoperative planning in cases necessitating surgical intervention. Also, CT
imaging can delineate adjacent soft tissue abscess or granulation tissue that
may require operative debridement.
Magnetic resonance imaging (MRI) is the gold standard for radiologic
evaluation of spinal infection. MRI demonstrates high sensitivity (96%),
specificity (92%), and accuracy (94%). Intravenous gadolinium further
delineates areas of abnormal enhancement and facilitates localization of
infection to the vertebral body, intervertebral disc, or epidural space. Optimal visualization of the neural elements allows for evaluation of canal compromise or spinal cord compression. MRI is readily capable of delineating
paravertebral abscesses. Multiplanar imaging allows for full evaluation of the
complete spinal column in sagittal and axial planes to assess for the extent
of involvement.
MANAGEMENT
Management of spinal infections has dramatically evolved over the last several decades. Advances in imaging allow for prompt diagnosis with initiation of appropriate antimicrobial pharmacotherapy, often early in the clinical
course. Improved surgical technique combined with developments in spinal
instrumentation has resulted in decreased surgical morbidity and better
long-term clinical outcomes. The general principles of treatment for spinal
infections, regardless of medical or surgical intervention, are fundamentally
the same. The primary objectives are to eradicate infection, preserve neurological function, maintain spinal alignment, and prevent pain.
Medical Therapy
Medical therapy for spinal infection consists primarily of antimicrobial pharmacotherapy. Most patients with vertebral osteomyelitis respond successfully
to nonsurgical treatment. The main tenet of medical therapy is identification of the inciting organism with either a positive blood or biopsy specimen,
and initiation of an appropriate antimicrobial agent. The selection of either
a single or multi-drug regimen is dictated by the virulence and resistance of
the causative organism. Therefore, optimal treatment is entirely dependent
on isolating an organism. As a result, antimicrobial treatment is withheld in
patients that are neurologicalally and clinical stable until definitive cultures
are obtained. Patients presenting with sepsis or progressive deterioration may
necessitate empirical broad-spectrum coverage until an organism is identified.
Antimicrobial therapy is generally delivered parenterally for a minimum
of 6 weeks. A 25% failure rate is observed in patients treated with antibiotics for less than 4 weeks. Serial serologic evaluation of ESR is an effective
measure of therapeutic response. After 6 weeks of intravenous antibiotics,
some advocate continuing oral therapy until the ESR has diminished by
a minimum of one half the pretreatment level to prevent relapse. A twothirds reduction in ESR from pretreatment levels is an indication of complete eradication of infection. In addition to antimicrobial pharmacotherapy,
immobilization with an external orthosis is recommended for patients with
severe pain, greater than 50% vertebral height loss, or involvement of the
thoracolumbar junction.
Medical treatment for spinal tuberculosis is primarily reserved for
patients without any neurological involvement. The Medical Research
Council Committee for Research on Tuberculosis in the Tropics concluded
that treatment for spinal tuberculosis in developing countries consists of
ambulatory pharmacotherapy with 6- or 9-month regimens of isoniazid
or rifampin. In Western countries, drug therapy for spinal tuberculosis is 6
months of isoniazid, rifampin, and pyrazinamide. Others advocate a more
aggressive approach to spinal tuberculosis with 12 months of treatment,
beginning with isoniazid, ethambutol, rifampin, and pyrazinamide for the
first 2 months, followed by tailoring of the therapy based on sensitivities.
Multimodal therapy is often necessary due to potential drug resistance, as
well as the decreased accessibility of certain agents to different involved
organ systems. Unfortunately, many of these agents have potential side
effects, with the risk of liver failure among the more clinically significant.
Indications for Surgical Intervention
There are several indications for surgical intervention for spinal infection.
Open surgical biopsy to determine the bacteriologic diagnosis is recommended in patients with nondiagnostic cultures or closed biopsy. Patients
in sepsis refractory to medical treatment may require abscess drainage or
debridement of necrotic tissue to facilitate penetration of antimicrobial
therapy to sites of active infection. Individuals presenting with acute neurological deficit resulting from spinal cord compression require emergent
decompression. Delaying surgical intervention in neurologicalally compromised patients may be cautiously reserved in those who are too significantly
medically compromised to undergo surgery, and those who present with
over 72 hours of neurological deficit. Chronic pain and significant deformity
are relative indications for surgical intervention.
Patients with spinal tuberculosis and neurological deficit generally are
require radical debridement with bone grafting and stabilization. There are data
to suggest that patients with tuberculosis and mild neurological deficits may
respond to medical therapy alone. In a study of 200 cases of patients with spinal
tuberculosis and neurological impairment, 38% of patients recovered with only
medical therapy. Sixty-two percent, however, ultimately required surgery, with
69% of surgically treated patients having a complete neurological recovery. A
direct correlation between duration of neurological symptoms prior to surgery
and time for recovery from paraplegia supports early operative intervention in
patients with neurological impairment. With prompt surgical treatment, better
neurological outcomes and prevention of deformity can be expected.
Surgical Management
Several important issues require consideration once it is determined that a
patient requires surgical intervention. The primary issue is deciding upon
an appropriate surgical approach and fusion technique, from a broad spectrum of operative modalities previously described. Anterior approaches
include anterior debridement and fusion with or without instrumentation.
Posterior approaches involve a posterior decompression, debridement, and
instrumented fusion. Circumferential approaches include anterior debridement with strut grafting and instrumentation with posterior supplemental
fixation in a single-stage or delayed fashion. Ultimately, surgical decisionmaking is dependent upon whether the primary pathology is ventral, dorsal,
or circumferential, and whether the infected tissue requires complete or partial debridement. Additional factors include the degree of preexisting defor
mity, determining the optimal technique for restoring spinal alignment, and
whether spinal reconstruction and stabilization are necessary. Last, given the
propensity for significant medical comorbidities in this patient population,
serious consideration must be given toward selecting a surgical approach
that the patient can tolerate with minimized morbidity.
Timing of surgical intervention is also a critical factor. Patients with acute
neurologicalal deficits secondary to spinal cord compression require emergent decompression to prevent irreversible injury. Persistent sepsis despite
medical therapy, with significant abscesses and infected or necrotic tissue,
may necessitate urgent drainage or debridement to decrease the overall
infectious burden and facilitate antimicrobial penetration. Acute instability
that threatens neurological structures demands immediate immobilization
and may require urgent operative stabilization. Delayed surgical intervention is indicated for patients that are stable neurologically and clinically, but
have disabling pain or evidence of chronic progressive deformity. Generally,
in these instances, surgical instrumented stabilization and arthrodesis is
performed after the acute infection is cleared.
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