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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6032_Библиотеки_им_академика_М_И_Перельмана
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Figure 1
Schematic drawings comparing the relative exposures
(diagonal lines) provided by five surgical approaches:
laminectomy (A), transpedicular (B), costotransversectomy (C), lateral
extracavitary (D), and transthoracic (E). As the exposure angle
becomes more anterior and visualization of the ventral structures
improves, the amount of dissection increases. (Reproduced from
Gebhauer G, Vaccaro A: Thoracic disk herniation and stenosis, in Rao
RD, Smuck M, eds: Orthopaedic Knowledge Update Spine 4.
Rosemont, IL, American Academy of Orthopaedic Surgeons, 2012, pp
324-328.)
Although tandem stenosis of the cervical and lumbar spines is common,
with a prevalence of up to 25%, tandem stenosis of the thoracic and lumbar
spines has an estimated prevalence of less than 2%.2 Nonetheless, advanced
thoracic imaging should be considered in patients with symptomatic
congenital lumbar stenosis and symptoms that suggest thoracic pathology.
Thoracic Disk Herniation
Thoracic disk herniation is common and found incidentally in 40% of
asymptomatic individuals.3 Although one study estimated that symptomatic
thoracic disk herniation occurs in only one in 1 million people,4 most spine
practitioners will encounter patients with this rare but potentially serious
condition. No sex or race predilection appears to exist for the development of
thoracic disk herniation, although most symptomatic cases occur in patients
in the fourth through sixth decades of life. The size of a disk herniation and
the extent of spinal cord compression do not always correlate with the
presence or magnitude of the patient’s symptoms. Most symptomatic thoracic
disk herniations occur caudal to the T8 level because of the proportionally
greater motion within this region. Between 30% and 70% of thoracic disk
herniations are calcified, although the pathophysiology of this phenomenon is
not clear. Calcific disks are more likely to be symptomatic and more
susceptible to adherence to the dura, increasing the potential morbidity
associated with their resection. Up to 10% of calcified disk herniations are
intradural, although this can be difficult to visualize or diagnose, even with
advanced imaging.
5
Clinical Presentation
Patients with thoracic disk herniation may present with axial back pain,
thoracic radiculopathy, or myelopathy. A combination of signs and symptoms
is not uncommon, and patients can report back pain or radiculopathy, but
exhibit more severe objective myelopathic features. The infrequent nature of
thoracic disk pathology and the lack of a characteristic clinical presentation
can contribute to a delay in recognition. Axial pain is the most common
presenting complaint and can be acute and spontaneous in origin or more
chronic in nature. Radiculopathy generally occurs with pain or paresthesia in
a dermatomal fashion in the chest or abdomen that is either unilateral or
bilateral, depending on the level and location of the disk herniation. The
onset of myelopathy may be obvious and acute or subtle and insidious.
Patients may experience weakness, gait difficulty, and frequent falls. When
pain is not a major symptom, a patient’s presentation can be delayed until
substantial compromise of function and neurologic deficit occur. Objective
lower extremity weakness, hyperreflexia, and clonus may be present. Bowel
and bladder dysfunction can occur in up to 25% of patients with myelopathy,
including acute incontinence or urinary retention and constipation.
Concurrent thoracic and lumbar pathology is not uncommon, although the
true incidence is not known. Symptoms of lumbar radiculopathy and
neurogenic claudication arising from lumbar spine disease can overshadow
the more subtle but serious features of concurrent thoracic myelopathy. A
high index of suspicion is necessary in patients presenting with documented
lumbar pathology who have subjective or objective evidence of myelopathy,
especially those with radiographic evidence of congenital stenosis.
Because of the relative infrequency of thoracic disk herniation, the true
natural history is difficult to define. Most, if not all, asymptomatic
herniations remain asymptomatic; new onset of symptoms is uncommon. In
symptomatic patients whose only symptoms are radicular, the prognosis is
generally favorable and progression to myelopathy is uncommon.6 Patients
with myelopathy may be severely affected on initial presentation and the
need for rapid surgical intervention makes it difficult to truly assess the
potential of spontaneous improvement. In the setting of advanced thoracic
myelopathy, resolution or improvement without surgical intervention is
unlikely.
Imaging
MRI is the gold standard for the detection and evaluation of thoracic disk
pathology. MRI (or CT myelography) is indicated with persistent thoracic
back pain and radiculopathy or with the presence of even subtle myelopathic
features. However, given the high incidence of clinically silent thoracic disk
herniations, clinical correlation with MRI findings is essential.
The location of the displaced fragment within the canal affects the
likelihood of neural element compression, and thus, subsequent symptoms.
Central disk herniations are generally larger and more likely to result in cord
compression and myelopathy. Lateral or foraminal disk herniations are likely
to result in thoracic radiculopathy. Thoracic disk calcification is relatively
common; therefore, the threshold to obtain CT should be low if calcification
cannot be determined using plain radiography or MRI because this can affect
management as well as surgical planning. Direct visualization with an
anterior surgical approach is often necessary for safe, thorough removal of a
calcified anterior disk herniation.
Treatment
Nonsurgical management is indicated for most patients. Management of axial
back pain or radiculopathy initially consists of activity modification;
NSAIDs; judicious, short-term use of muscle relaxants or opiate analgesics;
and physical therapy. Patients with mild myelopathy undergo nonsurgical
treatment, although close observation and careful patient education are
essential. Patients with profound or progressive myelopathic features should
be considered surgical candidates at the time of initial presentation. The goals
of surgical management for thoracic disk herniation include thorough spinal
cord decompression, maintenance or restoration of stability, and prevention
of recurrence. The surgical approach is selected based on the patient’s body
habitus and medical comorbidities, the location and size of the herniation, the
presence of calcification, and the surgeon’s experience level.
Anterior Surgical Approaches
The anterior approach to the thoracic spine provides the most direct
visualization of the disk space. Large central disk herniations and calcified
disk herniations that are susceptible to dural adherence are most often
removed safely and effectively using an anterior approach because posterior
approaches may not allow enough exposure to thoroughly remove the
compressed material or it can result in unsafe degrees of dural manipulation
(Figure 2). When clinically indicated, multiple levels can be treated without
substantial change in the extent of the anterior exposure. Following
diskectomy, reconstruction with structural bone graft and anterior
instrumentation should be considered to enhance stability, lessen the
likelihood of kyphosis, or mitigate pain that can be associated with disk space
collapse. No consensus exists regarding the need for adjunctive interbody
fusion or the likelihood for the development of kyphosis or substantial axial
back pain in the absence of fusion. The relative time and effort needed to
perform interbody fusion is minimal, and multiple series have reported
successful radiographic healing and associated clinical improvement.
7,8
Figure 2
Schematic drawings showing steps in the surgical removal
of a thoracic disk herniation from an anterior or a lateral
approach. Sagittal-view drawings showing removal of the pedicle at
the caudal level (A), removal (with a burr) of the posteroinferior aspect
of the cranial vertebral body and the posterosuperior aspect of the
caudal vertebral body to allow a plane to be developed between the
disk and the spinal cord (B), and removal of the disk anterior to the
herniation (C). Axial-view drawings showing the initial cavity created in
the central portion of the disk (D), the disk elevated anteriorly off the
curet (E), and the far side of the disk herniation elevated anteriorly
using a reverse-angled curet (F). (Reproduced from Gebhauer G,
Vaccaro A: Thoracic disk herniation and stenosis, in Rao RD, Smuck
M, eds: Orthopaedic Knowledge Update Spine 4. Rosemont, IL,
American Academy of Orthopaedic Surgeons, 2012, pp 324-328.)
The disadvantages of this approach relate primarily to morbidity
associated with thoracotomy such as the need for a chest tube and the risk of
pneumothorax, parenchymal lung injury, or intercostal neuralgia.
Deconditioned patients or those with compromised pulmonary function may
not be suitable candidates for an anterior approach.
Thoracotomy provides satisfactory exposure to the spinal column from
T3 through L1. In most cases, a left-side approach is preferred because the
thick wall of the aorta is less susceptible to injury than the more fragile vena
cava. However, if the predominant disk pathology is to the right of the
midline, a right-side approach may be preferable. At the thoracolumbar
junction, the presence of the liver also favors a left-side approach. For the
infrequently occurring upper thoracic disk herniation, a right-side approach
avoids the heart and subclavian and carotid arteries.
Thoracotomy for spine surgery is performed with the patient in the lateral
position, with all body prominences well padded. A double-lumen tube is
used to facilitate deflation of the ipsilateral lung to help expose the spinal
column. The localization of the target level is of greatest importance.
Intraoperative long radiographs that include the sacrum can assist with proper
localization. These intraoperative images can be compared with long,
preoperative sagittal images to ensure accurate, reliable identification of the
surgical level. Alternatively, preoperative placement of a localizing marker
while the patient is in the radiology suite can safely expedite surgery at the
proper level.
The incision should be made one or two rib levels cephalad to the target
level. A partial rib resection may be necessary, but is not essential if the
intercostal space can be opened adequately and maintained to provide
sufficient visualization. The parietal pleura over the rib head and vertebral
body is incised and reflected. The rib head is resected at its insertion to
identify the pedicle of the caudal level. The caudal pedicle is removed to
reveal the spinal canal and disk space. An annulotomy is performed and the
bulk of the disk material is removed to create a cavity within the disk space.
The compressed disk material is delivered into the cavity using fine-angled
curets in a ventrally directed manner. A plane is carefully created between the
disk material and the dura to lessen the risk of durotomy. Partial resection of
either adjacent vertebral body may be necessary for complete decompression,
especially with extruded or migrated fragments. Partial vertebrectomy should
be considered with giant disk herniation (one that occupies greater than 40%
of the spinal canal), given that the size and propensity for calcification
requires greater space and visualization for safe removal.
9
If interbody fusion is planned following successful disk removal, the
cartilaginous end plates are removed and the bony end plates are decorticated
before placement of the structural graft to create an optimal environment for
solid arthrodesis.
Most patients who undergo a transthoracic approach have had predictably
favorable clinical outcomes. More than 90% of patients in two series who
underwent open transthoracic diskectomy for large central disk herniations
with myelopathy experienced neurologic improvement and symptomatic
relief.
10,11
Mini-open thoracotomy techniques have been introduced to use direct
visualization while minimizing the morbidity associated with open
thoracotomy. Proponents describe this as the shortest, most direct approach to
the thoracic spine that also avoids violation of the pleural cavity.12 A smaller
skin incision and a limited rib osteotomy (instead of resection) is used
followed by a blunt retropleural dissection directed toward the spinal column.
The rib head articulation is identified and resected and the disk space entered
in a manner similar to that of the open thoracotomy approach. Even
extraordinarily large calcified disks have been effectively removed using
these mini-open thoracotomy approaches.
12
Even less invasive techniques such as those using dual-blade or tubular
retractors inserted via the intercostal space and docked on the thoracic spine
use direct visualization of the anterior approach and minimize soft-tissue
dissection and rib resection. Access to the spine can be retropleural to avoid
lung deflation and chest tube placement, thus limiting the potential for
pulmonary complications.13 Laterally based tubular systems, which have
been widely used in the lumbar spine, also have been used in thoracic
diskectomy, interbody fusion, and anterior instrumentation.
13,14
A potential
disadvantage of a tubular-based approach is the increased distance from the
surgeon’s hands to the patient’s spine, which can make surgical maneuvers
more difficult and possibly less safe.
15
Video-assisted thoracoscopic surgery, widely used by thoracic surgeons
for diseases of the lung and pleural cavity, has been used in the treatment of
thoracic disk herniation. Thoracoscopic techniques provide superior
visualization of the transthoracic approach and are associated with minimal
chest wall- or pulmonary-related complications. The illumination and
visualization of thoracoscopy, especially using angled endoscopes, is superior
to that of open or minimally invasive anterior techniques. A systematic metaanalysis of 545 patients who underwent thoracoscopic diskectomy reported
almost 80% improvement and a 24% complication rate, although most
complications were minor (most notably intercostal neuralgia and
atelectasis).16 Single-center studies have reported favorable outcomes in most
patients undergoing thoracoscopic diskectomy for both radiculopathy and
myelopathy.
17,18
Combining three-dimensional intraoperative image
guidance with thoracoscopic techniques has been described as particularly
safe and effective.19 Disadvantages of thoracoscopic diskectomy include
difficult access in obese patients or those with large thoracic cavities. Bone
graft and anterior instrumentation placement and the management of
incidental durotomies are also more difficult. With relatively few indications,
it is unlikely that many surgeons would achieve the level of skill to routinely
use thoracoscopic approaches.
20
Posterolateral Surgical Approaches
The use of laminectomy for thoracic disk herniations has largely been
stopped because of universally poor results and high rates of neurologic
complications.21 In a kyphotic spinal region, laminectomy alone does not
alter the ventral force of the thoracic disk herniation. The propensity for
kyphosis following laminectomy adds further mechanical insult to a spinal
cord draped over the spinal column.
Relevant posterolateral approaches to the thoracic spine include
costotransversectomy and transpedicular, transfacet pedicle-sparing, and
lateral extracavitary approaches. Each technique ultimately provides lateral
access to the disk space. Although posterolateral approaches do not provide
the optimal direct visualization afforded by an anterior approach, they avoid
morbidity associated with transthoracic techniques and are familiar to
surgeons. Given the relative limited visualization and because dural sac
manipulation is inadvisable, posterolateral techniques are most suitable for
lateral disk herniations.
Patients are placed in the prone position with all body prominences well
padded. Patients should be securely immobilized, especially if intraoperative
rotation of the table is planned to facilitate the surgeon’s line of vision.
Intraoperative spinal cord monitoring is used routinely and is particularly
valuable in patients with a compromised thoracic spinal cord. Motor-evoked
potentials are reported to be more sensitive than somatosensory-evoked
potentials in the early detection of neurologic injury.22 Obtaining baseline
traces before the patient is positioned may be useful in confirming that no
neurologic injury has occurred as a result of patient positioning. In addition,
careful attention should be given to maintain safe blood pressure parameters,
which avoid unsafe fluctuations that can adversely affect the tenuous spinal
cord. Before the procedure begins, it is essential to confirm that there will be
access to reliable intraoperative radiography or fluoroscopy, which will allow
visualization of the entire spinal column from the target level to the sacrum,
thus ensuring accurate localization. When performing an accompanying
instrumented fusion, placement of pedicle screws before the planned
decompression can minimize potential iatrogenic spinal cord injury.
For the transpedicular approach, the posterior elements are exposed
lateral to the facet joints in a subperiosteal fashion (Figure 3). A
hemilaminectomy can be performed to improve visualization of the
dorsolateral dura. The ipsilateral facet is resected to expose the caudal
pedicle, which is removed to the level of the vertebral body. An annulotomy
is performed and disk material is removed from a projection lateral to the
thecal sac. As with other techniques, a central cavity is created within the
disk space and fine-angle reverse elevators and curets are used in a ventral
direction to push disk material within the cavity, which is subsequently
removed using pituitary rongeurs.
The transfacet pedicle-sparing technique is an alternative to the
transpedicular technique in which a portion of the medial facet is removed to
expose the lateral aspect of the dura and disk space. Cadaver studies have
shown that similar degrees of lateral access to the disk space can be obtained
with either the transpedicular or transfacet techniques, despite less bone
removal and soft-tissue dissection when the pedicle is maintained.
23
Preservation of the pedicle has been reported to be associated with less axial
pain and better postoperative function.
24,25
Intraoperative ultrasonography
has been used to assess the adequacy of ventral decompression in
posterolateral thoracic diskectomies to circumvent the limited visualization
associated with these approaches. Ultrasonography is a simple, safe tool that
has been shown to accurately assess the dural-disk interface with both
transpedicular and transfacet pedicle-sparing techniques.
26,27
Costotransversectomy was originally described to treat the anterior
pathology of Pott disease and provides a large, more ventral access than the
transpedicular approach. This approach provides excellent exposure for
lateral disk herniations. A midline or paramedian skin incision is made and
wide soft-tissue exposure performed to achieve exposure lateral to the rib
articulation. Portions of the rib, rib head, and transverse process are resected.
The rib that articulates with the target disk is resected (the eighth rib
articulates with the T7 and T8 vertebrae and crosses the T7-8 disk space).
The caudal pedicle is removed to gain lateral access to the disk space. As
with the transpedicular approach, a plane is carefully created between the
disk and the dura, an annulotomy is performed laterally, and disk material is
pushed in a ventral direction and removed. Reliable symptomatic
improvement and neurologic recovery has been reported even for central disk
herniations and for disks with intradural erosion.28 The wider lateral exposure
is associated with a larger area for visualization and more room for surgical
instruments. The disadvantages of the more extensive lateral soft-tissue
dissection and bone resection is the potential for pleural violation or
intercostal neurovascular injury.
The lateral extracavitary approach (LECA) provides more expansive
exposure to the posterior and ventrolateral thoracic spine than either the
transpedicular or costostransversectomy approach. Originally designed for
traumatic conditions for which extensive bone resection and reconstruction
was planned, the LECA provides excellent visualization for lateral disk
herniations and also access for placement of structural graft or devices in the
interbody space when preferred. As with other posterolateral approaches,
posterior supplemental fixation also can be performed via the same incision.
Midline, hockey stick, or paramedian and curvilinear incisions have been
described for these techniques.
28,29
The paraspinal musculature is exposed
and either reflected and mobilized or transected to increase exposure.
Transection of the musculature may afford better visualization laterally, but
requires direct repair of the muscle belly before fascial closure. A medial
portion of the rib is resected along with the rib head articulation. During
exposure and removal of the rib, care should be taken to identify and protect
the intercostal nerve, which can be followed to the neural foramen.
Meticulous attention to the nerve can reduce the likelihood of postoperative
neuralgia associated with the more lateral exposure provided by the LECA.
29
The transverse process and caudal pedicle are removed, the lateral disk space
entered, and the diskectomy is performed. As with the costotransversectomy,
various amounts of vertebral end plate can be removed to facilitate removal
of migrated disk material. The greater lateral expanse to the disk space
provided by the extracavitary approach is more amenable to safe insertion of
a structural graft or cage device. A study of 65 patients undergoing LECA
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