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C H A P T E R 4 7 Infections of the oracic Spine
305
The use of instrumentation and certain grafting techniques in an
acutely infected wound is controversial. Instrumented spinal fusion surgery
is associated with increased risk of infection compared to nonfusion surgery. However, there are growing laboratory and clinical data to suggest that
titanium-based implants may have improved resistance to bacterial colonization than traditional stainless steel, and may be appropriate for spinal
stabilization even in the setting of acute infection. Selection of appropriate
graft material to promote arthrodesis without serving as a host environment for further bacterial seeding is also critical. Last, various minimally
invasive techniques for surgical debridement, instrumented stabilization,
and fusion have become available that may serve to improve clinical outcomes and reduce surgical morbidity compared to conventional open surgical modalities.
Posterior Approach
Posterior decompression for spinal infection is primarily reserved for evacuation of isolated epidural abscesses without involvement of the bony anterior spinal column or intervertebral discs. Epidural abscesses, particularly in
the thoracic and lumbar spine, preferentially occur dorsal to the thecal sac,
and therefore are amenable to laminectomy for decompression and drainage. The extent of the laminectomy ideally does not involve the facet joints,
so as to prevent iatrogenic destabilization. Reports of limited interlaminar
decompression with epidural abscess fenestration have been described;
however, the benefit of this minimal approach over standard laminectomy
has not been demonstrated. The additional insertion of an epidural suctionirrigation catheter at the time of surgery, for postoperative continuous washout, has also been reported to have beneficial results.
Posterior decompression alone is not recommended in the setting of
osteomyelitis, discitis, or osteodiscitis. Laminectomy with removal of the
posterior tension band further destabilizes the spine in patients with already
impaired anterior column support. Posterior decompression in the setting
of vertebral osteomyelitis has resulted in unfavorable outcomes related to
deformity progression, increased instability, and neurological deterioration.
With the advent of pedicle screw-rod fixation, a single-stage posterior
approach for decompression, debridement, and instrumented stabilization
may be an appropriate alternative surgical modality (Figure 47-5 A-C).
Various posterior approaches for accessing anterior thoracic and lumbar
pathology are available. Costotransversectomy, lateral extracavitary, and
transpedicular techniques allow access to the anterior spinal column via a
posteriorly based approach. With these techniques, debridement of varying
degrees of the anterior column may be performed, although complete vertebrectomy via a solely posterior approach is technically challenging, given
limited visualization of the anterior aspect of the thecal sac.
After debridement of infected, necrotic tissue, anterior column reconstruction may be achieved using either stackable or expandable interbody
devices that are designed to be inserted from a posterior approach (Fig-
ure 47-6 A-B). Particularly in the thoracic spine, a unilateral single nerve
root may be ligated to facilitate insertion of an interbody cage. Again,
however, limited exposure via a posterior approach may restrict the size
of interbody graft that can be inserted, thereby presenting potential risk
for graft subsidence, kyphosis, or nonunion. Supplemental posterior
fixation with a pedicle screw-rod construct provides instrumented stabilization, and thereby prevents progressive sagittal deformity as well as
facilitates arthrodesis. A single-stage posterior approach for debridement,
decompression, and stabilization may be particularly suited for medically compromised patients with osteomyelitis who may not tolerate a
thoracotomy for anterior exposure.
Anterior Approach
Anterior procedures to surgically treat osteomyelitis have become increasingly popular since Hodgson first reported anterior debridement and fusion
for spinal tuberculosis in 1960, and have since become the standard treatment for pyogenic osteomyelitis as well. Because the pathology is generally
ventral, an anterior approach allows for thorough debridement of infected
and necrotic tissue, and drainage of psoas or paravertebral abscesses. With
an anterior approach, it is possible to completely remove all necrotic tissue
until bleeding, well-vascularized bone is encountered, and to decompress
the ventral thecal sac. Anterior spinal column reconstruction with an interbody graft for arthrodesis, anterior column support, and restoration of sagittal alignment is also best attained from an anterior approach. Spinal fixation
A
F IG UR E 4 7- 5 A-C. A, T1-weighted sagittal MRI with gadolinium of the same patient, demonstrating abnormal enhancement in the vertebral bodies and
an associated epidural abscess. B, Lateral x-ray of the same patient revealing the pedicle screw-rod instrumentation and sagittal alignment. C, Anteroposterior x-ray
after posterior decompression and instrumented stabilization with a pedicle screw-rod construct.
B
C
306
F IG UR E 4 7- 6 A-B. Anteroposterior (A) and lateral
(B) x-rays in a 50-year-old male with T10-11 osteomyelitis. The
patient underwent a left costotransversectomy approach for
T10-11 partial corpectomy and debridement. Through the same
posterior approach, a stackable cage was inserted for anterior
column reconstruction, and pedicle screw-rod stabilization was
performed.
P A R T V I Other Surgical Treatment Modalities: Thoracic Spine
A
B
for stabilization and to facilitate arthrodesis can also be performed from an
anterior approach (Figure 47-7 A-D).
Various techniques for anterior debridement, vertebral column reconstruction, and instrumented stabilization have been described. Hodgson’s
original description of an anterior procedure to treat spinal tuberculosis
involved anterior debridement and autologous strut grafting without instrumentation. While initial reports demonstrated successful clinical outcomes,
subsequent studies have observed loss of correction, progressive deformity,
and pseudarthrosis without the use of instrumentation. As a result, various
developments in device technology for spinal reconstruction and stabilization have been made to improve upon these findings. The uses of anterior
instrumentation with or without posterior supplemental fixation in singlestage or two-stage procedure have evolved as modern modalities for the
treatment of vertebral osteomyelitis.
Anterior Approach with Anterior Fixation
An anterior approach allows for a single-stage, single-approach surgical
treatment for debridement, decompression, arthrodesis, and stabilization.
Initially, anterior procedures incorporated autologous strut grafting without
instrumented stabilization, because of concern about placing a foreign body
in a contaminated wound. As a result, patients were immobilized and maintained on prolonged bed rest postoperatively. Recently, however, numerous
reports have described successful use of titanium-based implants in the setting of spinal infection without evidence of persistent infection or relapse.
The use of anterior spinal fixation in combination with anterior debridement and grafting allows for early patient mobilization, thereby reducing
the risk of complications associated with prolonged recumbency such as
pneumonia, pulmonary embolism, decubitus ulcer, and muscle atrophy.
Dai et al reported on 22 patients treated with an anterior-only approach
for the treatment of thoracic and lumbar osteomyelitis.
1
Patients underwent
an anterior debridement, interbody fusion with autologous graft, and anterior instrumented stabilization. Follow-up was for a minimum of 3 years,
and there were no cases of residual or recurrent infection. ESR and CRP
returned to normal levels within 4 to 10 weeks postoperatively.
With anterior column reconstruction, the investigators observed an
improvement in kyphosis, with an average correction rate of 93.1%. Solid
arthrodesis was achieved in all patients within 6 months, with only two
patients requiring immobilization with an external orthosis. Significantly,
there were no cases of implant failure and only three instances of mild graft
subsidence.
Patients also demonstrated significant functional and neurological recovery. Eighteen patients were standing and ambulating within 1 week postoperatively. The remaining 3 patients were walking within 4 weeks. There
were no cases of postoperative neurological deterioration. All patients with
preoperative neurological deficits had complete recovery within 6 months
except for one Frankel grade C patient who improved to a Frankel grade D.
The anterior-only approach provides the benefit of thorough debridement, reconstruction, fusion and stabilization in a single-stage, single
approach. With a single surgical procedure, there is less morbidity associated with prolonged anesthesia, lengthy operative time, blood loss, and
potential tissue injury in patients who are generally medically compromised
and may be predisposed to poor wound healing. The addition of supplemental posterior fixation may result in longer constructs with further loss of
spinal motion segments. Others are concerned that placing instrumentation
in a contaminated wound results in formation of a biofilm on the implant
surface layer that harbors bacteria and is poorly penetrable by antibiotics. Therefore, additional posterior spinal instrumentation may present an
increased risk for persistent infection or recurrence.
Single-Stage Anterior and Posterior Procedure
A combined anterior and posterior procedure to treat vertebral osteomy-
elitis provides several benefits over a single anterior approach. Circumferential access to the spinal canal allows for complete neural decompression
in patients who may have both ventral compression from retropulsed bone
fragments and dorsal compression from epidural abscess or posterior spinal
arch involvement.
Korovessis et al studied 24 patients with osteomyelitis treated with a
single-stage anterior debridement, partial vertebrectomy, mesh cage and
autologous bone graft, and supplemental pedicle screw fixation.
2
Follow-up
was for an average of 56 months, with all patients demonstrating complete
resolution of infection. While three patients who were ASIA A on presentation remained ASIA A postoperatively, patients with incomplete spinal
cord injuries improved an average of 1.4 Frankel grades postoperatively. Six
patients with incomplete injuries preoperatively had full recovery of neurological function within 1 year of surgery. Eleven patients who were neurologicalally intact preoperatively returned to full premorbid functional and
C H A P T E R 4 7 Infections of the oracic Spine
307
A
C
FI G U RE 4 7 -7 A-D. A, Sagittal T2-weighted MRI demonstrating midthoracic osteomyelitis with bony destruction,
kyphosis, retropulsed fragments, and cord compression. B, Axial T2-weighted MRI showing multiple loculated paravertebral
abscesses at a level adjacent to the pathologic fracture. C, Postoperative lateral x-ray revealing the cage and anterolateral
instrumented stabilization. D, Postoperative anteroposterior x-ray demonstrating an anterior debridement, corpectomy,
cage placement, and anterolateral instrumentation.
B
D
activity levels within 4 to 6 months after surgery. Visual analog pain scores
improved postoperatively as well.
Combined anterior and posterior instrumentation provides an idealized
biomechanical construct to treat advanced bony destruction, spinal instability, and deformity secondary to vertebral osteomyelitis. Anterior removal of
necrotic tissue with anterior column reconstruction provides optimal load
sharing and restoration of sagittal alignment in cases of vertebral height
loss. Posterior supplemental fixation recreates the posterior tension band to
restrict potential for long-term loss of sagittal plane correction.
An anterior-only procedure presents concern regarding long-term stability. Some have observed that an anterior procedure without posterior
supplemental fixation results in poor sagittal correction and long-term
increase in kyphosis. An anterior fusion alone may be appropriate for a
single-level corpectomy with an intact posterior tension band. However,
patients with multilevel involvement, significant bony endplate destruction,
or disease that crosses the thoracolumbar junction may be predisposed to
failure with an anterior-only construct. Particularly, patients with loss of
the posterior tension band, either through extensive posterior spinal arch
involvement such as in spinal tuberculosis, or from iatrogenic destabilization via laminectomy, may also require supplemental posterior instrumentation. Alternatively, excellent restoration of sagittal alignment with long-term
maintenance of correction has been demonstrated with a combined anterior-posterior procedure.
A combined anterior-posterior procedure also creates an optimal
mechanical environment for arthrodesis. With an anterior interbody fusion,
the graft is placed under compressive rather than tensile forces, which
facilitates arthrodesis. Posteriorly placed transpedicular instrumentation
provides rigid immobilization in all three planes of rotation to effectively
stabilize the spine and improve fusion.
Two-Staged Anterior-Posterior Procedure
Circumferential treatment of vertebral osteomyelitis can be performed as
a single-stage procedure or in a two-staged fashion, with initial anterior
debridement and then delayed posterior fixation. Staged spinal surgery has
308
P A R T V I Other Surgical Treatment Modalities: Thoracic Spine
gained popularity for the treatment of various other complex spinal disorders such as deformity, trauma, and oncologic and rheumatologic conditions. The benefit of staged surgery is a shorter operative time and less blood
loss for each individual procedure, which may be particularly relevant for
patients with worse overall general health. A two-staged surgery allows for
a convalescent period to bridge between the two procedures, in which the
patients may have an opportunity to recover clinically and neurologicalally.
Also, performing supplemental posterior instrumentation in a delayed manner allows for a longer course of antimicrobial therapy to further reduce the
infected environment prior to implantation of hardware.
Dimar et al reported on 42 patients with osteomyelitis treated with
anterior debridement and strut grafting, followed by delayed instrumented
posterior spinal fusion at an average of 14.4 days after the initial procedure.
Many patients were acutely ill at presentation requiring urgent treatment,
but were in poor overall clinical status to undergo an extensive circumferential operation. Most were significantly debilitated from inadequate nutrition as well. For these patients, Dimar et al performed anterior debridement
and anterior strut grafting urgently to thoroughly remove the infection and
restore anterior column support. Patients were then immobilized in an
external orthosis, continued on intravenous antibiotics, aggressively resuscitated nutritionally, and initiated on physical therapy. Delayed posterior spinal fusion was then performed on a semi-elective basis when patients were
clinically stable to undergo a second procedure.
All patients had complete resolution of their infection with no evidence
of recurrence. Patients with preoperative neurological deficits improved
postoperatively. No significant deterioration in patients’ overall medical condition was observed as a result of the interoperative period. The average
length of hospitalization, however, was prolonged in this series, with a mean
length of stay of 24 days and range of 14 to 53 days.
Use of Instrumentation
The use of instrumentation in patients with spinal infection remains a con-
troversial issue. Hardware placement for fusion operations in uninfected
patients has been shown to increase postoperative infection rates. As a
result, historically, there has been concern regarding placement of instrumentation in a known contaminated field. This is particularly an issue in
complex spinal reconstructive procedures, which often represent longer
operations with extensive muscle exposure and tissue devitalization. This
is further compounded by a patient population who are typically older
with multiple medical comorbidities, and who may be predisposed to poor
wound healing and infection.
Concern for use of instrumentation in the setting of infection arises
from the risk of bacterial colonization of the implant. With traditional
stainless steel implants, a biofilm harboring bacteria develops around the
material. This colonized surface layer is poorly penetrated by antibiotics,
resulting in persistent infection. Laboratory studies, however, suggest that
titanium implants may be less susceptible to bacterial seeding than stainless
steel. Titanium, especially when smooth polished, may be more resistant to
bacterial adherence than other materials.
As a result, recently there has been increasing use of titanium-based spinal instrumentation in the surgical treatment of spinal osteomyelitis. The
growing popularity of spinal instrumentation stems from an improved ability to restore sagittal alignment, maintain spinal stability, protect neurological function, and relieve pain. Spinal instrumentation also serves to reduce
the risk of graft extrusion and to facilitate arthrodesis through rigid immobilization. Additionally, with internal spinal fixation, early patient mobilization is possible, thereby reducing the risk of complications associated with
prolonged bed rest and use of external orthoses. Because of the general concern for increased infection with instrumentation, however, the indications
for instrumented spinal stabilization in the setting of spinal infection must
be clearly established prior to use.
Spinal instrumentation to treat vertebral osteomyelitis has evolved dramatically. Pedicle screw-rod fixation has become a standard method for
supplemental posterior stabilization. More recently, device technology has
developed titanium cages as a method for rigid anterior column support.
Titanium cages offer several significant advantages over traditional anterior strut grafting with either tricortical iliac crest or rib autograft. Titanium cages provide immediate stability, and because of their rigidity can
tolerate compressive forces. Titanium cages can be tailored for size and
shape, and have a broad contact area for load distribution. They also have
significant interface strength between the implant and the vertebral endplates to prevent extrusion or displacement. Newer expandable cages are
designed to be inserted and then increased longitudinally in situ, thereby
exerting corrective forces to restore sagittal alignment. Titanium cages
also are engineered with a hollow mesh design to allow for packing of
morselized bone graft within the cage and for bony ingrowth during the
healing and fusion process.
Ruf et al examined 88 patients with vertebral osteomyelitis treated with
anterior column reconstruction with a titanium mesh cage.
cases involved placement of the cage in a single disc space. Twenty-eight
cases replaced a single vertebral level. Twenty-three cases were two-level ver-
3
tebral body replacements, and three cases involved three-level reconstructions. Kyphosis angles at the affected levels improved a mean 11.2° after
surgery, with a minimal loss of correction of only 1.4°. Four patients with
osteoporosis had evidence of cage settling, with three cases requiring revision surgery and additional posterior instrumentation. All patients demonstrated solid arthrodesis at last follow-up, with no recurrent infection.
Pee et al retrospectively reviewed 60 patients who underwent anterior
debridement, posterior stabilization, and anterior column reconstruction
with either tricortical iliac strut, titanium cage, or polyether ether ketone
(PEEK) cage
5
. The titanium and PEEK cages were packed either with
allograft bone chips, with autograft, or with mixed autograft/allograft for
arthrodesis. Pee et al observed that the tricortical iliac strut group had an
average 200 ml increase in operative blood loss compared to the titanium or
PEEK cage groups. While there was no significant difference in postoperative fusion rate between iliac strut and cage groups, there was a significantly
higher subsidence rate in the iliac strut group. Also, the mean time interval
until subsidence was shorter in the autograft group compared to the cage
group. They secondarily observed that patients with subsidence (regardless
of graft type) had more pain and disability than those without subsidence.
Therefore, the authors inferred that use of a cage may decrease the risk of
this adverse outcome, although this was not proven to statistical significance
in their series. Most relevant, however, was that all patients, regardless of
iliac strut or cage, had normalization of ESR and CRP postoperatively, with
complete resolution of infection at final follow-up.
While some may still have concern about the use of instrumentation in
the setting of spinal infection, there is clearly a growing body of evidence
that, titanium-based implants can be reasonably used with safety. Particularly, given the benefits of instrumentation with regards to spinal reconstruction, sagittal plane correction, stabilization, and early patient mobilization, a
serious recommendation for use of instrumentation to treat vertebral osteomyelitis in select cases can be made.
Graft Type
The selection of graft type for arthrodesis in the setting of spinal infection
is also controversial. The gold standard remains autologous bone graft, due
to its ideal osteobiologic properties. Fresh autologous tissue also may allow
rapid vascular ingrowth for effective antimicrobial delivery to the affected
site and prevent the risk of persistent bacterial colonization. For this reason,
vascularized grafts such as rotational rib grafts or free vascularized fibular
grafts may be necessary for complicated revisions due to persistent infection
or pseudarthrosis, although obtaining these grafts is technically demanding
and time-consuming. Because of the morbidity associated with harvesting
autologous bone graft, an alternative option is the use of allograft. Although
allograft represents a devascularized foreign body, more recent studies have
found that use of allograft struts in patients treated for vertebral osteomyelitis is otherwise safe and can be effective for arthrodesis.
A potentially exciting option is the use of bone morphogenetic protein
(BMP) to promote fusion. Recombinant human BMP (InFuse, Medtronic,
Memphis, TN, USA; OP-1, Stryker Biotech, Hopkinton, MA, USA) is a
synthetic osteoinductive agent that has been demonstrated in both animal
and clinical models to result in increased fusion rates. The use of BMP in the
setting of spinal infection, however, has not been widely clinically explored
and currently represents an off-label and contraindicated use of the product.
Laboratory studies in animal models, however, show that BMP retains its
osteoinductive properties even in the setting of acute or chronic infection.
Interestingly, in experimental models, BMP in combination with antibiotics results in more rapid healing than BMP alone. This may be secondary
4
Thirty-four
C H A P T E R 4 7 Infections of the oracic Spine
309
to increased angiogenesis caused by BMP-stimulated osteoblast-derived
vascular endothelial growth factor. Therefore increased vascular ingrowth
not only facilitates osteogenesis, but also leads to increased local antibiotic
delivery to better eliminate infection.
Limited clinical studies have investigated the use of BMP to promote
fusion in patients with vertebral osteomyelitis. However, a handful of studies evaluating the use of BMP placed either in structural allograft or in a
titanium cage with supplemental spinal fixation demonstrate successful
bony fusion, without recurrence of infection or evidence of complication
related to BMP use. While the use of BMP in the setting of spinal infection
is still not FDA approved, there is a small body of preclinical and clinical
evidence to suggest that BMP may be beneficial in promoting early fusion
in vertebral osteomyelitis. Certainly, further testing is warranted prior to
any recommendation for the clinical use of BMP for spinal infection can
be made.
Minimally Invasive Surgery
In many instances, spinal infections are successfully treated with conservative medical therapy. When surgical intervention is required, however,
operative treatment often requires extensive procedures consisting of radical debridement with spinal reconstruction and stabilization. Perioperative
morbidity in the elderly population or in patients with significant medical comorbidities is of particular concern. Significant complications after
complex spinal instrumentation procedures in patients with spinal infections are reported to be as high as 47%. Recently, minimally invasive surgical techniques have been developed as an alternative surgical modality for
the treatment of a variety of spinal disorders. These techniques, coupled
with novel device technology, have provided measures for performing many
of the same types of open decompressive and fusion procedures, albeit
through tissue-sparing approaches. As a result, decreased blood loss, less
postoperative pain, shorter hospitalization, and earlier return to function
have been observed.
Thoracoscopic Spinal Surgery
An anterior approach for vertebral osteomyelitis allows for direct visualization and access to the primary pathology. Anterior exposure of the thoracic and thoracolumbar spine via a conventional open approach, however,
requires a thoracotomy and potential splitting of the diaphragm. Significant morbidity is associated with a standard thoracotomy, including chronic
postoperative pain and respiratory compromise. To circumvent this issue,
video-assisted thoracoscopic surgical techniques have been applied for
minimally invasive treatment of thoracic spinal disease. While thoracoscopic spinal surgery is already widely used for basic procedures such as
thoracic discectomy and sympathectomy, more recently this technique is
being incorporated in operations to treat more complex pathology like scoliosis, trauma, tumors, and infection. Through multiple ports, exposure of
the thoracic and thoracolumbar junction as well as anterior debridement,
partial corpectomy, interbody cage placement, and spinal stabilization are
possible.
The literature reporting thoracoscopic treatment of vertebral osteomyelitis is limited. Muckely et al described three patients with thoracic
osteomyelitis that underwent thoracoscopic partial corpectomy, anterior
reconstruction, and anterior spinal fixation.
6
The improvement in kyphotic
angle among the three patients ranged from 6° to 15° with no evidence of
loss of correction at a minimum of 22 months of follow-up. There were no
cases of recurrence and no instances of graft or hardware failure. Of note,
one patient in the series was ambulating as early as postoperative day one.
Amini et al presented a case report of a 70-year-old patient who developed
osteodiscitis after a T11-12 discectomy.
7
The patient was treated with a
thoracoscopic vertebrectomy, allograft strut, and anterior instrumentation.
At 1-year follow-up, the patient demonstrated solid fusion without evidence
of recurrent disease.
Percutaneous Technology
Open posterior exposure of the spine consists of a midline incision with
dissection of the musculature away from the bony elements. This approach
allows for access to the dorsal spine for decompression as well as the necessary anatomy for placement of instrumentation and fusion bed preparation.
Extensive muscle dissection and prolonged retraction, however, can result
in tissue ischemia, denervation, scarring, and postsurgical dead space with
increased risk of blood loss, infection, chronic pain, and delay to functional
recovery.
Recently, percutaneous technology has been developed to perform a
variety of spinal procedures including discectomy, spinal decompression,
interbody fusion, and instrumented stabilization. These minimally invasive
techniques have been incorporated in the treatment of spinal infections as
well. Nagata et al applied a technique for percutaneous excision of lumbar
disc herniations as a method for aspiration and drainage of pyogenic spondylodiscitis.
8
Under local anesthesia, a percutaneous trocar that is 5.4 mm
in diameter is inserted under intraoperative fluoroscopy into the affected
level. Through this trocar, specialized forceps and a motor-driven shaver
are used to curette the infected disc and endplate, which are then removed
piecemeal. After debridement, large volume irrigation is flushed through the
trocar. Finally, a small suction drainage tube is left in the disc space and the
trocar is removed to allow for postoperative continuous antibiotic suctionirrigation.
Nagata et al performed this procedure in 23 patients with spondy-
lodiscitis.
8
The causative organism was identified through cultured tissue removed during curettage in 53% of patients. Ninety-one percent of
patients had immediate relief of back pain after surgery, with 43% ambulating without pain within 3 days of surgery. All patients were followed
for a minimum of 2 years with only one patient requiring a repeat operation for recurrent infection. No vascular or neurological complications
were encountered as a result of the procedure. Three of 6 patients with
preoperative neurological deficits, however, continued to have mild sensory
impairment at last follow-up, and therefore, this procedure is not recommended for patients with significant bony destruction, epidural abscess, or
neurological compromise.
Instrumentation for spinal fixation of unstable pathologic fractures and
deformity correction has also been advanced by percutaneous technology.
Standard open placement of pedicle screws requires extensive dissection of
the posterior musculature to expose the necessary anatomic landmarks for
screw insertion and connecting rod placement. Cannulated pedicle screws,
however, have been introduced that allow for placement of screws over a
guidewire percutaneously inserted under fluoroscopic imaging. With this
technique, multilevel fixation can be performed with multiple separate stab
incisions for each screw placement (
Figure 47-8 A-E). Novel technology
has been developed to allow for introducing a connecting rod through the
screw heads via an additional separate stab incision. Due to its low operative
morbidity, percutaneous stabilization may have a particularly beneficial role
as supplemental posterior fixation for patients undergoing primary anterior
debridement and spinal reconstruction.
PROGNOSIS
With earlier diagnosis and better medical and surgical intervention, clinical
outcomes and prognosis from spinal infection are improving. Mortality rates
from pyogenic osteomyelitis were once as high as 25% to 71%. Depending
on patient age and comorbidities, mortality rates for treated pyogenic osteomyelitis are now as low as 5% to 16%. Ninety-one percent of patients are
estimated to recover uneventfully with either medical therapy or combined
medical and surgical intervention. Similar improvement in mortality has
been observed for patients with epidural abscesses. Dandy in 1926 reported
a mortality rate of 83% for patients with spinal epidural abscesses. Now,
with prompt surgical intervention and improved antibiotic therapy, the mortality rate ranges from 5% to 32%.
The prognosis for neurological recovery generally depends on the duration and severity of neurological impairment prior to intervention. Patients
with epidural abscesses that are treated within 24 hours of onset of deficits
have a better prognosis for recovery of function. Rigamonti et al observed
that only 10% of patients with severe neurological deficits who were treated
within 24 hours of onset of symptoms had poor neurologic outcomes,
compared to 47% of patients treated more than 24 hours after onset of
symptoms having a poor neurological outcome.
complete paralysis, especially if present for more than 36 hours, do not generally recover, despite any intervention.
Chronic pain is a potential long-term complication associated with
osteomyelitis, and may be multifactorial. Some studies have found that
9
Additionally, patients with
310
P A R T V I Other Surgical Treatment Modalities: Thoracic Spine
A
C
FI G U RE 4 7 -8 A-E. A, Sagittal T1-weighted MRI of an 83-year-old male with a history of Mycobacterium absces-
sus and debilitating pain related to instability from bone loss and progressive deformity. B, Coronal CT reconstruction of
the same patient demonstrating significant bony destruction and coronal plane deformity. Given the patient’s advanced
age, significant medical comorbidities, and poor nutritional status, he underwent minimally invasive percutaneous spinal
stabilization. C, Intraoperative photograph after percutaneous placement of multilevel cannulated pedicle screws, and demonstrating securing the locking nuts after percutaneous insertion of the connecting rod. D, Postoperative AP radiograph
demonstrating the final construct with restoration of the coronal plane deformity. The connecting cross-link was also placed
percutaneously. E, Postoperative coronal CT reconstruction demonstrating correction of the coronal plane deformity.
B
D
E
patients that underwent surgical intervention are actually less likely to
have chronic back pain than those treated with antibiotics alone. Better
restoration of sagittal alignment and spinal stabilization with surgery may
account for this difference in outcome. However, 36% of patients treated
only with medical therapy do recover without any long-term disabling
back pain. This observation may be due to less severe bony destruction in
patients treated nonsurgically, or to spontaneous fusion that occurs from
the inflammatory response. Spontaneous bony ankylosis forms in 35%
of patients; this, however, may require 6 to 24 months to occur. Deformity is another potential complication that may contribute to pain and
long-term dysfunction. Deformity is more common with spinal tuberculosis, especially when occurring at the thoracic or thoracolumbar spine,
or when involving more than 50% of one or more vertebral bodies. Good
clinical outcomes, however, are demonstrated with surgical intervention.
With an anterior decompression and fusion, 94% of patients with spinal
tuberculosis recover normal neurological function, with a fusion rate of
92% at 5 years.
CONCLUSION
The reportedly growing number of spinal infections may become an
increasingly significant health care problem. Spinal infections are predisposed to occur in the elderly and those who are medically compromised.
As a result, spinal infections are often a complex medical condition with
multiple contributing factors, and are therefore challenging to manage.
The importance of successfully treating spinal infections is all the more
relevant given the potential for significant associated medical complications, neurological compromise, functional impairment, and chronic
disability.
Spinal infections represent a wide-ranging spectrum of pathologic
involvement and therefore are not amenable to simple treatment algorithms
or protocols. General principles dictate that early diagnosis with identification of the pathogenic organism is critical for successful medical therapy
with eradication of infection and minimized complications. Patients who
are neurologicalally intact and clinically stable can generally be managed
C H A P T E R 4 7 Infections of the oracic Spine
311
nonsurgically. Patients who present with neurological deficits, clinical deterioration despite medical therapy, or evidence of spinal instability, deformity,
or chronic pain may necessitate surgical intervention. Currently, a variety
of surgical treatment options are available ranging from minimally-invasive
techniques to radical debridement with complex spinal reconstruction and
instrumented stabilization.
Developments in diagnostic imaging, antimicrobial therapy, and surgical
techniques are advancing our therapeutic capabilities and improving clinical
outcomes. Better understanding of the disease response to surgical interventions, particularly the use of instrumentation and osteobiologic agents,
are reshaping current treatment paradigms. As a result, we are witnessing
greatly reduced morbidity and mortality. With a multidisciplinary approach
committed to early and aggressive management of spinal infections, we can
continue to expect even better patient outcomes.
References
1. L.Y. Dai, W.H. Chen, L.S. Jiang, Anterior instrumentation for the treatment of pyogenic ver-
tebral osteomyelitis of thoracic and lumbar spine, Eur. Spine J. 17 (8) (2008) 1027–1034.
2. P. Korovessis, T. Repantis, P. Iliopoulos, A. Hadjipavlou, Beneficial influence of titanium mesh
cage on infection healing and spinal reconstruction in hematogenous septic spondylitis: a retrospective analysis of surgical outcome of twenty-five consecutive cases and review of literature, Spine 33 (21) (2008) E759–E767.
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Thoracic Spinal Stenosis
Josef B. Simon and Eric J. Woodard
48
k e y p o i n t s
oracic myelopathy can be caused by numerous pathologies such as tumor,
disc herniation, and ossification of the ligamentum flavum (OLF) and/or
posterior longitudinal ligament (OPLL).
Cultural differences exist in the etiology of thoracic myelopathy.
e thoracic spinal cord takes up 40% of the space available for the spinal
cord. Due to this anatomical difference, space-occupying lesions in the
thoracic spine may cause more rapid and profound impingement and
impairment of the spinal cord.
Multiple imaging modalities should be utilized to assess patients with signs
and symptoms of thoracic myleopathy.
When surgery is indicated, the approach should be dictated by the
location and type of pathology. Patients with OLF or OPLL or
neoplasm will most likely require both surgical decompression and
fusion. Circumferential decompression carries a high risk of
neurological deterioration.
INTRODUCTION
Stenosis of the thoracic spine is a relatively rare condition when compared
to stenosis of the cervical or lumbar spine. Because it is unusual, a full
understanding of the condition’s epidemiology and clinical presentation is
limited, yet like stenosis in other spinal regions, its causes are numerous.
These include ossification of the ligamentum flavum (OLF) (Figure 48-1)
or posterior longitudinal ligament (OPLL) (Figures 48-2 and 48-3), herniation of intervertebral discs (Figures 48-4 and 48-5), and spondylosis.
Other causes include neoplastic lesions, facet cysts, vascular malformations,
and fracture. Stenosis of the thoracic spine typically presents with a variable combination of three main symptoms: back pain, radiculopathy, and
myelopathy.
Much of what is known about thoracic stenosis has been derived from
the experience of Japanese practitioners. OLF is cited as the most common
cause of thoracic spinal stenosis. Although case reports of OLF with thoracic myelopathy in whites and North Americans have been published,
patients of Asian descent are most frequently affected. Up to 20% of Asians
older than 65 years of age have some degree of thoracic stenosis due to OLF.
Aizawa et al, in a retrospective study of 265 Japanese patients, found OLF to
account for more than half of all cases of thoracic myelopathy.
men had the condition more frequently than women. It is not yet clear why
this condition has a gender discrepancy and why it tends to occur in younger
patients than those with cervical or lumbar stenosis.
Because OLF and OPLL are unusual among Westerners, much of the
European and North American literature focuses on thoracic intervertebral
disc disease as the primary etiology of thoracic spinal stenosis. As with OLF
and OPLL, thoracic disc herniation is overall an unusual cause of thoracic
back pain, radiculopathy, and myelopathy. Studies suggest than it affects
males most frequently and tends to occur between the fourth and sixth
4
decades.
4
Middle-aged
12
312
PATHOLOGY
A number of anatomical features make the thoracic spinal cord particularly
vulnerable to injury. Unlike the cervical region, where the spinal cord takes
up approximately 25% of the cross-sectional area of the canal, the thoracic
cord constitutes 40% of the canal. Due to this anatomical difference, spaceoccupying lesions in the thoracic spine may cause more rapid and profound
impingement and impairment of the cord. The thoracic kyphosis also creates a relative “bowstring” effect with the spinal cord draped across the posterior longitudinal ligament, the intervertebral discs, and the vertebral bodies.
This positions the ventral cord in close apposition to compressive pathology
of these structures.
The thoracic spinal cord has a more tenuous blood supply than the
lumbar and cervical neurological segments. Ventral perfusion derives from
the main feeding vessel, the artery of Adamkiewicz, which variably supplies
the thoracic spinal cord. Intrinsic blood supply comes from the midline
anterior spinal artery and two posterior vessels that are smaller than their
counterparts in other regions of the spine. Intercostal arteries make up the
extrinsic blood supply and are smaller and fewer in number than those in
the cervical and lumbar spine. This vascular arrangement creates a relative
watershed area between T4 and T9 that makes the region vulnerable to
ischemic injury.
OLF occurs as a normal part of the aging process and rarely leads to
stenosis. Histologically, the normal ligamentum flavum is composed of
significant amounts of elastin that, with aging and degeneration, is progressively replaced by collagen, fragments of bone, cartilage, and fibrous
5
tissue.
Pathologic ossification is characterized by extreme progression of
these processes leading to overgrowth and, ultimately, canal and foraminal
stenosis. The precise mechanisms of pathologic OLF have not yet been
clearly determined. It has been suggested that high mechanical stress of the
thoracolumbar junction leads to degeneration of the facets and intervertebral discs, initiating progressive injury of the ligamentum flavum in this
6
region.
Ossification then proceeds in response to repetitive injury. This
may explain why OLF occurs more frequently in the lower thoracic spine.
Although plausible, this theory has been questioned because the cervical
and lumbar spinal regions are more mobile than the thoracic spine, yet ossification in these locations is less common.
extend across multiple levels. Medical comorbidities such as diabetes mellitus, abnormalities in calcium metabolism, hypoparathyroidism, and Paget
3
disease may play a significant role and have been associated with pathologic
8,9
OLF.
The higher incidence of OLF in the Japanese population clearly
suggests a genetic etiology.
OLF associated with thoracic myelopathy most typically occurs in the
lower thoracic spine.
T11-12 was the most common site of compression, followed by T10-11
and T9-10. When OPLL was the cause, T1-2 was affected most commonly,
followed by T2-3 and T3-4.
As with OLF and OPLL, isolated traumatic injury to thoracic intervertebral discs is rare. The splinting effect of the rib cage as well as the vertical orientation of the thoracic facets serves to reduce the forces on thoracic
discs compared to those in the lumbar spine. This is thought to decrease the
incidence of discal injury in the thoracic area. Degeneration of thoracic discs
10
In their epidemiologic study, Aizawa et al found that
11
7
It is also rare for OLF lesions to
C H A P T E R 4 8 oracic Spinal Stenosis
4
6
8
313
F IG UR E 4 8 - 1 Ossification of the ligamentum flavum (OLF) of T8-9
with severe cord compression and progressive paraparesis in a 61-year-old
male. OLF is more common in Asian males and in the lower segments of the
thoracic spine.
6
F IG UR E 4 8 -3 Multisegment laminectomy, fusion, and instrumenta-
tion was required for cord decompression and junctional stabilization. The dorsal dura is extensively ossified.
F IG UR E 4 8- 2 Sagittal plain CT scan demonstrating ossification of the
posterior longitudinal ligament (OPLL) of the upper thoracic segments extending to the cervicothoracic junction in a 56-year-old female.
due to aging can occur as well, being most common in the fourth through
the sixth decades of life, with males affected more frequently than females.
Thoracic disc herniation tends to occur in the midline or just lateral to the
midline, and predominates in the lower thoracic levels (Figures 48-6 and
12
48-7).
Wood et al reviewed 90 MRI scans of asymptomatic patients and
F IG UR E 48 - 4 Thoracic disc herniation, T8-9, with symptomatic cord
compression and T2 signal change of the cord.
demonstrated that, often, thoracic disc herniations exist without symp-
13
toms.
An additional study by Wood et al showed that these herniations
do not frequently progress.
14
CLINICAL PRESENTATION
The clinical presentation of thoracic stenosis ranges from simple back pain
to frank myelopathy. Thoracic back pain is the most common presentation
of a disc herniation, with patients describing the pain as “passing through
314
P A R T V I Other Surgical Treatment Modalities: Thoracic Spine
F IG UR E 48 - 5 Axial view demonstrates significant midline cord com-
pression. This lesion requires a direct, ventral approach and was resected by
costotransversectomy.
6
12
F IG UR E 4 8- 6 Left-sided T7-8 HNP with predominantly radicular symp-
toms, refractory to conservative care.
their chest.” When lower thoracic discs are affected, the pain may radiate
to the abdomen, flank, or groin. Paresthesias, numbness, intercostal neuralgias, unsteady gait, and fatigue while walking may also be present. When
myelopathy occurs, it often presents itself as trunk and lower extremity
weakness (especially of proximal musculature), spasticity, and sensory loss.
The upper extremities should be spared. Alterations in bladder control can
occur. Because of the similarities in presentation, and the infrequency of
thoracic spinal stenosis, thoracic myelopathy can often be confused with
lumbar and/or cervical stenosis, leading to delays in diagnosis.
F IG UR E 48 -7 Minimal cord displacement and lateral lesion position
make this situation optimal for transpedicular or transfacet discectomy.
DIAGNOSIS
Physical findings of patients with thoracic myelopathy are similar to those
seen in lumbar and cervical stenosis. Lower extremity weakness, hyperreflexia, decreased sensation, sphincter malfunction, loss of abdominal
reflexes, and gait instability can be present. In addition, patients may localize
their pain and hypesthesia in a thoracic distribution. Complete paraplegia
due to thoracic spinal cord compression has also been documented.
15
Patients with symptoms of thoracic spinal stenosis often may have findings on plain x-rays that suggest the etiology of the condition. Destructive
lesions such as tumors and vascular malformations may be directly visualized, as can some fractures. When there is OLF, beak-like bony densities are
characteristically seen projecting into the posterior aspect of the spinal canal
on the lateral x-ray.
with plain x-ray, unless there is a significant amount of ossification.
16
Asymptomatic disc herniations are poorly visualized
17
Unless
there is an underlying metabolic abnormality, laboratory studies are typically
normal.
Studies have compared the utility of CT and MRI in the diagnosis of
thoracic spinal cord compression due to ossification of spinal ligaments.
Both CT and MRI scanning may play a role in the diagnosis of thoracic spinal cord compression. Plain CT provides detailed information regarding the
bony anatomy and degree of ossification of the spinal ligaments, as well as
ossification of intervertebral discs and facet hypertrophy. MRI, on the other
hand, helps to define the extent of spinal cord injury and identify facet cysts.
In the setting of OLF, CT myelography is unnecessary, as it adds little to the
data collected by MRI, and the contrast injection occasionally exacerbates
symptoms of stenosis. If MRI is contraindicated in a patient, such as with a
pacemaker, CT myelography is the study of choice.
TREATMENT
Thoracic myelopathy due to OLF or OPLL is not well treated by con-
servative methods such as nonsteroidal antiinflammatory medications and
physical therapy. Surgical decompression is often required when stenosis results in myelopathy or debilitating radiculopathy. The best mode of
surgical treatment for stenosing OLF is not well defined in the literature.
Depending on the extent of compression, laminoplasty, partial or total laminectomy, circumferential decompression, and decompression with fusion
have been proposed. The proponents of laminoplasty suggest that this procedure may produce less instability than other modes of decompression.
18
19