Surgery is indicated for the rare patient with an acute thoracic disk herniation with progressive neurologic deficit i.e., signs or symptoms of thoracic spinal cord myelopathy.. It has b
Trang 1Thoracic disk herniation, first
de-scribed in the literature by Key
in 1838, has historically been
diffi-cult both to diagnose accurately
and to treat appropriately In 1911,
Middleton and Teacher reported a
case of acute paraplegia in a man
who had attempted to lift a heavy
weight He subsequently died, and
an autopsy revealed a large T12-L1
thoracic disk herniation.1 In both
the orthopaedic and the
neurosur-gical literature, there is a lack of
consensus concerning the most
reproducible and effective method
for nonoperative management of
thoracic disk disease The wide
diversity of presenting signs and
symptoms, as well as the many
other clinical entities that may
pro-duce symptoms similar to those of
a herniated thoracic disk make a definite diagnosis of primary tho-racic disk disease challenging The difficulty in establishing the diag-nosis is compounded by the rela-tively high prevalence of incidental thoracic disk degeneration and her-niations in the asymptomatic pa-tient population
Anatomy and Biomechanics
The thoracic spine is a relatively rigid transition zone between the mobile cervical and lumbar re-gions; its unique stability is the result of the surrounding thoracic
rib cage Each rib head between T2 and T10 has two facets, which articulate with its respective verte-bral body and with the one more cephalad (e.g., the head of the T5 rib articulates with the T4 and T5 bodies) The heads of the 1st, 11th, and 12th ribs articulate only with their similarly numbered vertebral bodies The facets of the T1 through T10 vertebral bodies are generally oriented vertically, with slight medial angulation in the coronal plane This provides sig-nificant stability during flexion and extension, while allowing greater movement in lateral bend-ing and rotation Biomechanical studies have shown that the tho-racic intervertebral disks are most
at risk for injury with combined torsional and bending loading The combination of the splinting effect of the thoracic rib cage and the resistance of the thoracic facets
to flexion loads lessens the poten-tial for intervertebral disk injury in the thoracic spine compared with the lumbar spine
Dr Vanichkachorn is Chief Resident, De-partment of Orthopaedics, Thomas Jefferson University Hospital, Philadelphia Dr Vaccaro is Professor of Orthopaedics, Thomas Jefferson University Hospital.
Reprint requests: Dr Vaccaro, Fifth Floor,
925 Chestnut Street, Philadelphia, PA 19106 Copyright 2000 by the American Academy of Orthopaedic Surgeons.
Abstract
Symptomatic degenerative disk disease is much less common in the thoracic
spine than in the cervical and lumbar regions Accurate diagnosis relies on a
strong clinical suspicion that is confirmed with appropriate diagnostic
imag-ing Presenting symptoms vary tremendously, from atypical pain patterns to
myelopathy The use of computed tomography in combination with
myelogra-phy and magnetic resonance imaging have greatly increased the ability to
accurately visualize thoracic spine disorders The superior resolution of
avail-able imaging modalities has made the incidental detection of asymptomatic
racic disk abnormalities more frequent Most patients with symptomatic
tho-racic disk disease will respond favorably to nonoperative management.
Surgery is indicated for the rare patient with an acute thoracic disk herniation
with progressive neurologic deficit (i.e., signs or symptoms of thoracic spinal
cord myelopathy) Once surgical intervention has been chosen, careful
preop-erative planning is necessary The level, anatomic location, and morphology of
the herniation must be precisely determined to select the optimal approach.
Posterior laminectomy has largely been abandoned for the treatment of
symp-tomatic thoracic disk protrusions Surgeons still may choose among anterior,
lateral, and posterior approaches when surgically addressing the thoracic
inter-vertebral disk.
J Am Acad Orthop Surg 2000;8:159-169
Jed S Vanichkachorn, MD, and Alexander R Vaccaro, MD
Trang 2The spinal canal in the thoracic
region is circular, with the posterior
and lateral aspects formed by broad
overlapping laminae and short
pedicles, respectively Even though
the spinal cord is smallest in
diame-ter in the thoracic region, the spinal
cordÐcanal ratio is approximately
40% because of the small canal size,
compared with 25% in the cervical
region The dentate ligaments,
which run longitudinally between
the spinal cord and the nerve roots,
limit posterior displacement of the
spinal cord within the canal, thus
making the thoracic spinal cord
more sensitive to ventral
compres-sion from anterior disk and bone
prominences Furthermore, the
nat-ural kyphosis of the thoracic spine
causes the spinal cord to lie directly
on the posterior longitudinal
liga-ment and the posterior aspects of
both the vertebral bodies and the
disks in this region Therefore, even
thoracic disk herniations may cause
significant ventral compression of
the thoracic spinal cord
The blood supply of the thoracic
spinal cord is more variable and
tenuous than that of either the
cer-vical or the lumbar region The
thoracic spinal cord receives its
intrinsic blood supply from the
combination of one anterior and
two posterior longitudinal arterial
trunks The midline anterior
arte-rial trunk gives off central artearte-rial
tributaries, which supply most of
the thoracic spinal cord These
ves-sels are smaller in caliber and fewer
in number than those in the lumbar
and cervical regions
An additional extrinsic arterial
supply comes from vessels that arise
variably from the segmental
inter-costal arteries Like the central
arter-ial tributaries, these arteries are
smaller in caliber and fewer in
num-ber than in other regions of the spine
Often, there is a single dominant
ves-sel, the artery of Adamkiewicz This
vessel may originate from a
segmen-tal artery between T7 and L4, usually
on the left side of the spine.2 This artery has a very limited degree of collateralization The anatomic junc-tion of the arterial circulajunc-tion between the cervical and thoracic regions makes the area between T4 and T9 a watershed region with a tenuous vascular supply susceptible
to ischemic injury
Epidemiology
In 1995, Wood et al3 examined the magnetic resonance (MR) images of
90 asymptomatic individuals and found thoracic disk abnormalities in 73% Of these individuals, 37% had frank disk herniations, and 29%
showed definite deformation of the cord In a follow-up study, Wood et
al4reexamined 20 patients with 48 asymptomatic thoracic disk hernia-tions previously diagnosed on MR imaging No patient became symp-tomatic during the study period, with a mean follow-up interval of
26 months They also noted that small herniations (<10% of canal compromise) either remained un-changed or increased in size, while larger herniations (>20% canal com-promise) tended to get smaller over time The authors concluded that asymptomatic thoracic disk hernia-tions exhibit relatively little change
in size over time and rarely become symptomatic
Computed tomography (CT) in combination with myelography has also been shown to be extremely sen-sitive for identifying incidental asymptomatic thoracic disk hernia-tions In 1991, Awwad et al5 re-viewed the CT-myelograms of 433 patients who did not have any symp-toms of thoracic disk disease They found that the frequency of asympto-matic thoracic herniated disks ranged from 11.1% to 13.3% Furthermore, there was no correlation between the radiologic characteristics of these le-sions and the subsequent emergence
of symptomatic disease
It has been estimated that the incidence of symptomatic thoracic disk herniation is approximately 1 in
1 million persons per year.6 This represents approximately 0.25% to 0.75% of the total incidence of symp-tomatic spinal disk herniations each year.7 The occurrence of sympto-matic thoracic disk disease is great-est between the fourth and sixth decades of age, with the peak inci-dence in the fifth decade In general, there is a slight male predominance, and symptomatic women tend to present at a later age than men A small number of adolescents with Scheuermann disease present with a progressive neurologic deficit (mye-lopathy or radicu(mye-lopathy) secondary
to an acute thoracic disk herniation Between 33% and 50% of patients re-port a history of trauma or signifi-cant physical exertion prior to the onset of symptoms.8
Natural History
The natural history of symptomatic thoracic disk disease appears to mimic that in the cervical and lum-bar regions, in that conservative treatments and time are often suffi-cient to cause improvement in a patientÕs symptoms and functional abilities Surgical intervention for thoracic disk herniation is rarely re-quired; only about 0.2% to 1.8% of all disk herniations are surgically treated each year.9
The clinical course of thoracic disk herniation can be quite vari-able and is dependent on a combi-nation of patient and pathophysio-logic factors In general, two types
of patients with thoracic disk herni-ations have been described The first are younger patients with an acute soft disk herniation There is usually a short history of symp-toms that can be attributed to an acute traumatic event These pa-tients are likely to present with either acute spinal cord
Trang 3compres-sion or radiculopathy They usually
respond well to both nonoperative
and operative treatment
The second (and larger) group
consists of older individuals who
present with a longer duration of
symptoms that are more likely to
be secondary to chronic spinal cord
or root compression Degeneration
of the involved disks appears to be
the underlying pathologic change
in this group A history of trauma
is less common These disk
hernia-tions can be soft but more often are
calcified, reflecting the
degenera-tive nature of the process
Clinical Presentation
The differential diagnosis of thoracic
pain is extensive and includes a
num-ber of both spine-related and
non-spine-related conditions (Table 1)
Patients with thoracic disk
hernia-tions may present with a wide
vari-ety of vague complaints that can
mimic a large number of pathologic
conditions depending on the
nature, severity, and level of the
herniation The clinician must
examine the entire patient to be
able to rule out all other possible
causes for symptoms before
pursu-ing the diagnosis of thoracic disk
herniation
Patients with symptomatic
tho-racic disk herniations can be generally
divided into three groups
depend-ing on the symptoms at
presenta-tion The first group are those
pa-tients who present with axial pain
as the predominant complaint
Pain, whether it be local or
radicu-lar, is by far the most common
pre-senting symptom of a thoracic disk
herniation The axial pain is
usual-ly localized to the middle to lower
thoracic region, but in some
cir-cumstances may have a radiating
component referred to the middle
to lower lumbar spine The pain is
generally characterized as mild to
moderate in intensity
Radicular pain, often described as
an anterior-chest bandlike discom-fort in a dermatomal distribution, is the second type of presentation The T10 dermatomal level is the most commonly reported distribution regardless of the level involved Ra-dicular pain is more common in upper thoracic and lateral disk her-niations and is often reported in combination with some amount of axial pain Sensory changes, such as paresthesias and dysesthesias in a dermatomal or radicular distribu-tion, are the second most commonly reported symptoms of acute thoracic disk herniation
Myelopathy is the third and most worrisome type of presenta-tion Patients complain of muscle weakness; mild paraparesis is the most common lower-extremity manifestation of a thoracic disk herniation A positive Babinski sign, sustained clonus, a wide-based gait, and spasticity are all signs of myelopathy and indicate marked thoracic cord compression
Bowel and bladder dysfunction are seen in approximately 15% to 20%
of patients with symptomatic tho-racic disk herniations Classic spinal cord syndromes, such as Brown-SŽquard syndrome, have been reported in instances of large acute midline or paramedian herni-ations Symptoms of isolated pos-terior cord involvement are rarely encountered
High thoracic disk herniations (T2 to T5) can mimic cervical disk disease and present with symptoms
of upper arm pain, radiculopathy, paresthesias, and even Horner syn-drome A careful neurologic exami-nation of the upper extremity is often required to isolate the area of pathologic change When positive, the cervical compression test is more indicative of a cervical origin
of the patientÕs upper-extremity symptoms than of thoracic hernia-tion When myelopathy is suspected because of the presence of
hyper-reflexia in the lower extremities and the Hoffmann sign is negative, an abnormality can be assumed to be present below the cervical spine Clinical differentiation between lumbar and thoracic causation of a patientÕs symptoms requires an astute examiner First, the patientÕs gait and posture should be evalu-ated for any abnormal or awkward motions The presence of splinting,
Table 1 Differential Diagnosis of Thoracic Pain
Nonspinal causes
Intrathoracic Cardiovascular Pulmonary Mediastinal Intra-abdominal Hepatobiliary Gastrointestinal Retroperitoneal Musculoskeletal Postthoracotomy syndrome Polymyalgia rheumatica Fibromyalgia
Rib fractures Intercostal neuralgia
Spinal causes
Infectious Neoplastic Primary Metastatic Degenerative Spondylosis Spinal stenosis Facet syndrome Degenerative disk disease Costochondritis
Metabolic Osteoporosis Osteomalacia Deformity Kyphosis Scoliosis Trauma Neurogenic Herniation Spinal cord neoplasm Arteriovenous malformation Inflammatory (e.g., herpes zoster)
Trang 4antalgia, circumduction, Òdrop footÓ
gait, or a Trendelenburg gait should
be documented A sciatic list may
indicate a contralateral disk
hernia-tion Lateral bending may indicate
an ipsilateral axillary herniation
The Romberg sign is very useful for
detecting subtle changes in
proprio-ception and early myelopathy
Palpation or percussion of the
posterior spinal elements will often
localize the pain to the thoracic
region or recreate the radicular
symptoms in a patient with a
tho-racic disk herniation Examination
of the function of muscles innervated
by thoracic nerve roots is not
high-ly specific; however, having the
patient attempt a partial sit-up is
helpful Asymmetric contraction of
the segmentally innervated rectus
abdominis muscle may indicate a
disorder arising from the thoracic
spinal cord
Testing of the superficial
ab-dominal reflexes can indicate an
upper-motor-neuron lesion arising
from this region Another important
indication of upper-motor-neuron
function in the thoracolumbar
re-gion is the superficial cremasteric
reflex This reflex demonstrates the
integrity of the efferent T12 and
afferent L1-2 neurologic levels Loss
of the patellar reflex or the Achilles
tendon reflex in combination with
positive nerve-root-tension signs is
suggestive of a lumbar disk lesion
and lower-motor-neuron irritation
All patients with suspected lumbar
disk herniations should be tested for
ankle clonus and the Babinski sign
When positive, these tests indicate
an upper-motor-neuron lesion and
are more suggestive of a
compres-sive lesion in the thoracic or
thora-columbar region than of an isolated
nerve-root irritation
Identification of the sensory level
is extremely important in
evaluat-ing thoracic cord compression
Sensory dermatomes should be
carefully tested, and the presence of
paresthesias or dysesthesias in a
radicular pattern (Fig 1) should also be noted The T4 dermatome is
at approximately the level of the nipple line; the T7 dermatome is at the xiphoid process; the T10 der-matome is approximately at the umbilicus; and the T12 dermatome
is consistent with the inguinal crease
Patterns of Disk Herniation
An accurate description of the mor-phology and location of the hernia-tion is important in the treatment of thoracic disk herniations Thoracic disk herniations are classified by their level and location as visual-ized on diagnostic imaging As in other regions of the spine, thoracic disk herniations may occur in mid-line, paramedian, or lateral posi-tions Approximately 70% to 90%
of thoracic disk herniations are either midline or paramedian le-sions Intradural disk fragments or migrating sequestered disk frag-ments are rarely seen in the thoracic region
Thoracic disk herniations can be either calcified or noncalcified
This is important clinically because significant calcification may indi-cate adhesions between the disk fragment and the dura or even in
an intradural location
Midline or paramedian hernia-tions have the greatest propensity for producing myelopathic symp-toms; lateral herniations more fre-quently result in radicular pain
Herniations are extremely rare in the upper thoracic region; T1-2 to T4-5 herniations account for only approximately 1% to 3% of all tho-racic disk disorders Approxi-mately 50% to 75% of thoracic disk herniations occur between the T8 and L1 levels.10 The T11-12 and T12-L1 interspaces are the most frequent sites of sympto-matic disk lesions, due to the
rela-tive mobility and the increased potential for degenerative disease
at these levels
Although thoracic disk abnor-malities are often seen at more than one level, rarely is more than one level symptomatic There are exceptions, such as Scheuermann kyphosis, which predisposes the thoracic intervertebral disks to premature calcification and degen-eration
Diagnostic Imaging
A confirmatory neuroimaging study is necessary before operative treatment of symptomatic thoracic disk herniation can be considered
A plain-radiographic examination
of the thoracic and lumbar spine must be completed to rule out any other obvious disorders, such as
Figure 1 Sensory dermatomes of the trunk region (Reproduced with permission from Klein JD: Clinical evaluation of patients with spinal disorders, in Garfin SR, Vaccaro
AR [eds]: Orthopaedic Knowledge Update: Spine Rosemont, Ill: American Academy of
Orthopaedic Surgeons, 1997, pp 87-96.)
T4
T8
T10
T12
Trang 5neoplastic disease and acute osseous
injury Additionally, evaluation of
all lumbar and thoracic
morpho-logic variations, as well as the size
and level of corresponding ribs,
facilitates the accurate
intraopera-tive identification of thoracic level
Plain radiographs identify the
pres-ence of intradiskal calcification
(Fig 2) in approximately 45% to
71% of symptomatic herniated
tho-racic disks This is in contrast to
the 10% incidence of thoracic disk
calcification in asymptomatic
indi-viduals.10
Magnetic resonance imaging is
an ideal technique for the
evalua-tion of thoracic disk disorders, as it
is both noninvasive and highly
sen-sitive Coronal axial and sagittal
images can accurately demonstrate
the morphology and level of a
tho-racic disk herniation, as well as
identify intradural and free
migrat-ing disk fragments Thoracic disk
herniations have an intermediate
signal intensity on T1-weighted
images and appear as an area of
low signal density on T2-weighted
images (Fig 3, A) On sagittal
im-ages, a thoracic disk herniation is
identified by its posterior
protru-sion into the thoracic spinal cord
(Fig 3, B) On a T2-weighted
sagit-tal image, a thoracic disk herniation
is readily identified by the
sur-rounding high-intensity signal of
the cerebrospinal fluid, which gives
a ÒpseudomyelogramÓ appearance
(Fig 3, C) T2-weighted images
of-ten exaggerate the size and
signifi-cance of actual pathologic changes
Calcifications within a disk
frag-ment present as low-intensity
sig-nal on both T1- and T2-weighted
images
Computed tomography in
combi-nation with myelography assists in
the determination of the type and
level of herniation and also clarifies
the osseous anatomic features in
relation to the soft- or hard-tissue
disk herniation (Fig 3, D and E)
The presence of disk-fragment
calci-fication is readily identifiable with CT-myelography, but a sequestered migrating disk fragment or an in-tradural disk fragment is often diffi-cult to delineate with this imaging modality Like MR imaging, CT-myelography is extremely sensitive and will also identify incidental asymptomatic thoracic disk hernia-tions with relatively high frequency
In summary, the presence of a thoracic disk abnormality on plain radiography, MR imaging, or CT-myelography must be carefully correlated with a patientÕs symp-toms and clinical examination findings before an accurate diag-nosis can be made Although con-sidered controversial, diskography may be safely used to provoca-tively determine the presence of axial back pain.11 This may be useful in the presence of multi-level disease or in patients with a severe thoracic pain syndrome but
no discernible evidence of a neu-rologic abnormality on imaging studies
Nonoperative Treatment
The clinical presentation of a tho-racic disk herniation can vary
wide-ly depending on its morphologic characteristics The natural history
of most acute thoracic disk hernia-tions is benign and mimics the course of herniations in the lumbar spine The treatment protocol for acute thoracic disk herniations is therefore similar to the nonopera-tive management that is used for patients with acute lumbar hernia-tions
In patients with predominantly axial pain without significant radic-ular symptoms, treatment in the acute phase should initially consist
of activity modification and non-steroidal anti-inflammatory drugs Patients should be warned of the potential gastrointestinal side effects of these agents Using a combination of nonoperative treat-ments, Brown et al7 successfully treated 63% of patients with symp-tomatic thoracic disk herniations
Figure 2 A,Plain radiograph of the thoracolumbar junction in a 54-year-old man who presented with a 3-week history of severe bandlike pain in the distribution of the T10 der-matome Degeneration of the disk spaces is demonstrated by sclerosis of the vertebral
endplates Early calcification is seen within the T12-L1 disk (arrow) B, CT-myelogram of the
T12-L1 disk interspace demonstrates a paramedian soft disk herniation The patient had no improvement with nonoperative management and underwent excision of the disk through
a lateral costotransversectomy, with complete resolution of preoperative symptoms.
Trang 6For the extremely uncomfortable
patient, narcotics and muscle
relax-ants may occasionally be prescribed
for very limited periods of time;
however, such use should be
care-fully considered and avoided
alto-gether if possible
Patients with significant
radicu-lar symptoms on presentation are
also treated with a regimen of
non-operative modalities Corticosteroid
injections into the intercostal nerves
can be added and are sometimes
beneficial in both a therapeutic and
a diagnostic sense A short course
of oral corticosteroids should be
tapered off after 3 to 5 days The
anti-inflammatory benefits of corti-costeroids should be weighed against the possible side effects or risk factors (e.g., hyperglycemia, osteonecrosis) before their use
In the acute stage, physical ther-apy should consist primarily of pas-sive modalities, such as heat, ice, manipulation, and ultrasound, to moderate symptoms and provide patient comfort After the acute stage has passed, physical therapy should become more active and should include range-of-motion, flexibility, and strengthening exer-cises Hyperextension exercises are beneficial and should be
empha-sized by the therapist Occasion-ally, a patient with an acute hernia-tion will be so uncomfortable that even light physical therapy is not possible In these situations, epi-dural or intercostal corticosteroid injections can provide the relief nec-essary to begin a physical therapy program After the resolution of the patientÕs symptoms, a home therapy program that includes aer-obic conditioning should be insti-tuted for prevention of recurrent symptoms
Bracing can be used in certain circumstances to provide relief dur-ing the acute phase of thoracic disk
Figure 3 Images of a 46-year-old woman who pre-sented with a 6-month history of moderate to severe
midthoracic pain without radicular symptoms A,
Axial T2-weighted MR image demonstrates a midline
T7-8 thoracic disk herniation B, Sagittal T1-weighted
MR image shows protrusion of a T7-8 thoracic disk herniation Neurologic examination was significant
for three or four beats of clonus bilaterally C, Sagittal
T2-weighted MR image of the same T7-8 thoracic disk herniation demonstrates the ÒpseudomyelogramÓ appearance of the herniation The patient did not respond to conservative treatment consisting
primari-ly of nonsteroidal anti-inflammatory drugs, physical
therapy, and activity modification D, Preoperative
myelogram demonstrates the T7-8 thoracic disk
herni-ation compressing the anterior thecal sac E, The
post-myelogram CT study further delineated the midline T7-8 soft disk herniation The patient underwent exci-sion of the herniation through a transthoracic approach and had complete neurologic recovery without complication.
Trang 7herniation As is the case with the
lumbar spine, prolonged reliance
on external orthoses causes
decon-ditioning and predisposes to
fur-ther dysfunction Therefore, an
or-thosis should be used only briefly,
if at all, until physical therapy can
be tolerated by the patient A brace
that causes hyperextension (e.g., a
Jewett brace) is usually the most
comfortable for the patient
Occa-sionally, a custom-molded
clam-shell brace for hyperextension can
be useful
Nonoperative management should
be continued for 4 to 6 weeks If the
symptoms do not significantly
im-prove or worsen during this period,
operative treatment is recommended
Early surgical intervention may be
considered if unrelenting radicular
pain fails to respond rapidly to
non-operative care Patients who present
with myelopathy or a progressive
neurologic deficit are candidates for
immediate surgical intervention
Nevertheless, a complete medical
workup and careful preoperative
planning are still required before
surgery is performed Some patients
with myelopathy who appear to be
improving or to be stable without a
significant functional deficit can
ini-tially be treated nonoperatively and
closely observed
Preoperative Planning
When the decision for surgical
exci-sion of a thoracic disk herniation
has been made, a number of factors
must be evaluated preoperatively
in order to select the appropriate
approach and method of
decom-pression Determining the exact
level for surgical excision is of
paramount importance, as
diskec-tomy at the wrong level in thoracic
surgery is not an infrequent
prob-lem In a study of anterior thoracic
disk excisions, Bohlman and
Zdeb-lick12 reported a poor result
sec-ondary to excision of a disk at the
wrong level This required a second operative procedure for removal of the actual herniation
By carefully counting up from the sacrum on sagittal views from either the CT-myelogram or the MR imag-ing study, the level of the herniation can usually be accurately deter-mined Coronal and axial sections obtained at the appropriate levels will then help determine the size of the herniation and whether the her-niation is midline, paramedian, or lateral Calcified disk fragments, which are likely to have dural adhe-sions, also should be assessed with preoperative imaging studies Re-view of the plain radiographs may reveal a coexisting thoracic disorder
The presence of thoracic stenosis may require a more generous de-compression than initially planned
The identification of Scheuermann kyphosis may necessitate decom-pression and fusion over multiple levels
Intraoperatively, it is essential that the correct disk space be iden-tified As mentioned previously, in the thoracic spine, the 1st, 11th, and 12th ribs articulate only with their corresponding vertebral bodies
From T2 to T10, each rib head artic-ulates through articular facets with its own vertebral body and the ver-tebral body above Therefore, for example, exposure of the T8-9 disk space is best approached through a thoracotomy with removal of the 9th rib head
Intraoperative plain radiographs
of adequate quality are essential for accurately determining the level of pathologic change The L5-S1 disk space or T12 vertebral body with its corresponding rib can usually
be identified on an intraoperative anteroposterior or lateral radio-graph These levels can be used as
a reference point from which to count cephalad to the appropriate vertebral interspace Herniations
in the upper thoracic spine may be identified on a lateral swimmerÕs
view by counting caudad from the lower cervical vertebrae Preopera-tive radiographs should be studied carefully to identify anomalies, such as osteophytes, and to count the number of lumbar bodies, which can aid in determining the level of the herniation on intraoper-ative radiographs
The overall health status of the patient should be considered dur-ing the preoperative period Pul-monary status is one of the most important functions to examine when considering a surgical ap-proach requiring a thoracotomy Pulmonary function tests provide important information about the medically compromised patient A vital capacity of 35% or less of the predicted value can be indicative of postoperative pulmonary complica-tions and may necessitate avoidance
of thoracotomy during surgery
Surgical Approaches
The surgical excision of a herniated thoracic disk may be accomplished
by utilizing an anterior, posterior,
or lateral approach (Table 2) Ante-rior approaches include the more common transthoracic and the less common transsternal approaches Video-assisted minimally invasive techniques are variations of the transthoracic approach and avoid a thoracotomy Posterior approaches include laminectomy and pediculo-facetectomy Lateral approaches include costotransversectomy and lateral extracavitary exposure Each approach has its own particular ad-vantages and disadad-vantages, which must be carefully considered when selecting the method of exposure (Table 3)
Anterior Approaches
The transthoracic approach is the most commonly used anterior approach to the thoracic spine First reported in 1969 by Perot and
Trang 8Munro13 for the treatment of
tho-racic disk herniations, the
transtho-racic approach has been widely
used by a number of authors with
excellent results Bohlman and
Zdeblick12 compared the anterior
transthoracic approach with
costo-transversectomy in 19 patients All
8 patients treated through a
trans-thoracic approach had good or
ex-cellent results The only 2 poor
re-sults were related to the use of the
costotransversectomy Currier et
al14reported their results in 19
pa-tients with thoracic disk
hernia-tions that were treated with
trans-thoracic diskectomy and fusion
Good or excellent results were seen
in 12 of the 14 patients without
prior laminectomy or coexistent
multiple sclerosis
The anterior thoracic approach
permits excellent anterior midline
exposure from the T4-5 to the
T11-12 intervertebral levels Multiple
levels are easily accessed, allowing
for the placement of a strut graft if necessary, and the posterior ele-ments are left relatively undis-turbed Pleural violation with this approach requires postoperative closed chest drainage The speed
of perioperative recovery is influ-enced by the extent of the surgical dissection, especially when access-ing the T12-L1 junction, which requires diaphragmatic detach-ment The technical aspect of this surgery is at times demanding, especially in the setting of previous thoracic surgery, and may require the assistance of a thoracic surgeon
Posterior Approaches
Currently, the only posterior ap-proach recommended for the treat-ment of a herniated thoracic disk is pediculofacetectomy Earlier in the past century, posterior laminectomy was the preferred method for sur-gical removal of a thoracic disk herniation However, the frequent
morbidity associated with this approach (e.g., neural injury, inad-equate decompression, and contin-ued symptoms) led to the abandon-ment of this technique In a 1985 review of the data on 135 patients after laminectomy for thoracic disk excision, Arce and Dohrmann15 found that 58% were improved, 10% were unchanged, 28% were made worse, and 4% died
The pediculofacetectomy, or transpedicular, approach was first described by Patterson and Arbit in
1978.16 This technique is best suited for the removal of lateral and some soft paramedian disk herniations in the upper thoracic spine and is aided by the use of the operating microscope In 1993, Le Roux et al17 reported on 20 patients with tho-racic herniations treated with a transpedicular approach At 1-year follow-up, all 20 patients had sig-nificant improvement, and 8 had no reportable symptoms The obvious limitation of the
pediculofacetecto-my approach is that there is both limited access and limited visual-ization for removal of midline, paramedian, and intradural hernia-tions Furthermore, removal of a pedicle-facet complex may result in segmental instability and pain Concern about the possible postop-erative pain caused by this instability led to the recent development of a transfacet pedicle-sparing posterior approach by Stillerman et al.18
Lateral Approaches
The two most commonly used lat-eral surgical exposures for the exci-sion of a thoracic disk herniation are the lateral extracavitary and costo-transversectomy approaches The lateral extracavitary approach is a modification of the lateral thoracot-omy approach described by Larson for use in treating spine disorders.19 This approach may be used for her-niations at any level in the thoracic spine and is particularly useful in the removal of soft and calcified lateral
Table 2
Surgical Approaches for Disk Herniation *
Type and Level Location Approach
Soft disk
T1 to T4 Central, centrolateral Transsternal
Central, centrolateral Medial claviculectomy Centrolateral, lateral Costotransversectomy T4 to T12 Central, centrolateral, lateral Transthoracic
Central, centrolateral, lateral Thoracoscopy Centrolateral, lateral Lateral extracavitary Central, centrolateral, lateral Transpedicular
Calcified disk
T1 to T4 Central, centrolateral Transsternal
Central, centrolateral Medial claviculectomy Lateral Costotransversectomy T4 to T12 Central, centrolateral, lateral Transthoracic
Lateral Lateral extracavitary Lateral, centrolateral Costotransversectomy
* Adapted with permission from Mirkovic S, Cybulski GR: Thoracic disk herniations, in
Garfin SR, Vaccaro AR (eds): Orthopaedic Knowledge Update: Spine Rosemont, Ill:
American Academy of Orthopaedic Surgeons, 1997, p 91.
Trang 9and paramedian thoracic disk
herni-ations The additional rib resection
of the lateral extracavitary approach
increases the access to the central
portion of the spinal canal and the
posterior vertebral body
Further-more, because the pleura is not
rou-tinely violated, closed chest drainage
is not needed postoperatively, and
approaches to the thoracolumbar
junction do not require takedown of
the diaphragm Multiple levels are
easily exposed, and strut grafting
may be accomplished if necessary
The main disadvantage of this
exposure is its technical difficulty
The amount of bone resection
re-quired during exposure is
signifi-cant, and surgical time and blood
loss may be substantial
Further-more, midline dural tears are
diffi-cult to access and repair, and the
sacrifice of the segmental
neuro-vascular structures may result in
postoperative pain and numbness in
the chest wall
The costotransversectomy ap-proach was first used in 1900 by Menard for the drainage of a tho-racic tubercular abscess In 1960, Hulme20adopted the costotransver-sectomy approach for the treatment
of thoracic disk herniations after laminectomy yielded disappointing results In 1993, Simpson et al21 re-ported on 21 patients with thoracic disk herniations excised through a modified costotransversectomy
No neurologic complications were recorded, and 16 patients had excel-lent or good long-term results
The costotransversectomy ap-proach does not violate the pleura and is very useful in the removal of paramedian and lateral disk hernia-tions in the entire thoracic spine
The main disadvantage of this pro-cedure, as with the extracavitary approach, is that the paraspinal musculature is significantly manipu-lated This exposure is not safe for the removal of calcified disks or large
posterior osteophytes, nor is it gen-erally appropriate when a complete anterior decompression is needed in
a case of advanced myelopathy
Video-Assisted Thoracic Surgery
Video-assisted thoracic surgery
is rapidly becoming a widely used treatment option for the manage-ment of selected thoracic disk herniations Thoracoscopy for the treatment of spinal disease was first reported in 1993 by Regan and Mack, who used this technique to biopsy and drain a thoracic para-vertebral abscess.22 Since then, tho-racoscopy has been successfully used for disk herniations, anterior thoracic releases for spinal
deformi-ty, osteotomies, and corpectomies Thoracoscopy has the potential advantage of avoiding the pul-monary complications and mor-bidities of an open thoracotomy Denervation of the paraspinal mus-culature is largely prevented,
al-Table 3
Advantages and Disadvantages of Surgical Approaches for Thoracic Disk Disease
Posterior approaches (pediculofacetectomy)
¥ Less extensive dissection ¥ Difficulty of removing calcified disks
¥ Good for high-risk patients ¥ Potential for producing instability
¥ Good for high thoracic herniations (T2-4) ¥ May not address intradural fragments
Anterior approaches (transsternal, transthoracic)
¥ Excellent exposure from T2 to T10 ¥ Requires a thoracotomy
¥ Does not affect posterior-column stability ¥ May require takedown of diaphragm
¥ Good for all types of disk herniations ¥ May not be ideal for high-risk patients
¥ Best approach for densely calcified disks ¥ Visceral structures at direct risk
Lateral approaches (costotransversectomy, lateral extracavitary)
¥ Excellent for lateral disk herniations ¥ Increased operative time
¥ Good exposure for most lesions ¥ Bone resection can be significant
¥ May avoid thoracotomy ¥ Difficulty of removing calcified disks
¥ Good for high-risk patients ¥ Disruption of paraspinal musculature
Minimally invasive approaches (video-assisted thoracic surgery)
¥ Decreased postoperative pain ¥ Technically difficult procedure
¥ Decreased length of hospitalization ¥ Steep learning curve
¥ Decreased postthoracotomy complications ¥ Potential visceral injury from trocars
¥ May be useful for high-risk patients ¥ Difficulty of removing calcified disks
Trang 10though neurapraxia may result
from compression of an intercostal
nerve between the trocar and the
ad-jacent rib In addition, the amount
of bone resection necessary for
visualization is decreased
In 1996, Regan23 compared the
outcomes obtained with
video-assisted thoracic surgery with those
obtained with traditional open
approaches for the excision of
tho-racic disk herniations Duration of
intensive-care unit stay, duration of
chest-tube drainage, and the time to
return to work were all decreased in
patients who underwent disk
exci-sion with thoracoscopy The main
disadvantage of this technique is the
high level of technical skill required
and the steep learning curve
neces-sary to acquire that skill The
assis-tance of a thoracic surgeon trained
in thoracoscopic techniques may be
necessary initially until more
expe-rience is gained The ability to
strut-graft anteriorly, place anterior
instrumentation, and repair dural
tears is currently limited In his
study, Regan reported a 14%
com-plication rate in patients with
tho-racic disk herniations treated with
video-assisted thoracic surgery
Intercostal neuralgia and visceral
injury from trocar placement were
the most commonly seen
complica-tions With increasing research and
experience in the area of minimally
invasive techniques, thoracoscopy
may prove to be a safe and
repro-ducible technique for the excision of
thoracic disk herniations
Role of Fusion
The role of fusion in thoracic disk
surgery is controversial Some
sur-geons believe that the inherent
sta-bility of the thoracic rib cage makes
the need for simultaneous fusion
unnecessary after simple thoracic
disk herniation Other surgeons
contend that the addition of an
autologous graft at the time of disk
excision adds little morbidity and prevents complications from postop-erative instability Currier et al14 routinely performed fusion to pre-vent instability or pain from a de-generative motion segment and rec-ommended fusion whenever the bone resection necessary for decom-pression resulted in instability, as well as in all cases of Scheuermann disease Bohlman and Zdeblick12 did not routinely perform arthrode-sis after disk excision except in patients with demonstrated instabil-ity and those with Scheuermann dis-ease Fusion after disk excision can
be considered a routine indication in Scheuermann disease when multiple levels are decompressed
Relative indications for fusion are instances of multiple-level disk re-sections at risk for postoperative ky-phosis or degeneration and single-level disk removals that require a wide vertebral-body excision that affects segmental stability Because the T12-L1 level is the transitional zone from the more rigid thoracic spine to the less rigid lumbar level, stability at that level should be care-fully assessed after disk excision to determine whether supplemental fusion is indicated When a fusion
is added to a thoracic disk excision, postoperative bracing is generally recommended until radiographic evidence of fusion is documented
Instrumentation, whether anterior
or posterior, is generally not indi-cated for one- to three-level disk excisions above T10, because there
is a protective splinting effect of the thoracic rib cage except when the sternum is split for exposure An-terior instrumentation can be added
in procedures that necessitate a sig-nificant amount of vertebral body removal and therefore result in instability, as is more common after revision disk procedures Posterior instrumentation is not indicated for single-level disk excisions above T10 but is used in patients with Scheuermann disease for
simultane-ous correction of coexisting thoracic kyphosis Progressive kyphosis at the thoracolumbar junction after thoracic disk excision can require a secondary instrumented posterior fusion for correction of deformity and restoration of stability.24
Complications
In a series of 82 patients treated sur-gically for thoracic disk herniations, Stillerman et al25reported an over-all complication rate of 14.6% The three major complications included one perioperative death, one in-stance of spinal instability, and one instance of permanent increase in paraparesis from the preoperative level In their review of the con-temporary literature (263 proce-dures), the major complication rate was 6.1%, and the overall complica-tion rate was 14.8% A major com-plication was defined as death, per-manent deterioration in neurologic status, any problem requiring fur-ther surgery, or a serious periopera-tive medical complication
Since the abandonment of poste-rior laminectomy as a treatment option, mortality has been reported only sporadically in the literature and usually occurs in the high-risk medical patient Dietze and Fessler26 reviewed the data on 85 patients in three separate studies in whom tho-racic disk herniations had been treated with either an anterior or a lateral approach They reported excellent clinical results with no perioperative deaths and only one case of transient paraparesis Per-manent paraparesis or worsening neurologic function has been the most commonly reported major perioperative complication Of the
16 major complications reported in the review by Stillerman et al,25an increased neurologic deficit was the cause in 5 (31%) The use of intra-operative neurologic monitoring greatly reduces the risk of