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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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produces peripheral sensitization (increased sensitivity of primary afferent
neurons in the richly innervated joint capsule and synovial membrane) as
well as central sensitization (hyperexcitability of nociceptive interneurons in
the central nervous system).
6
Because of the chemoinflammatory and neural sensitization contributions
to pain, corticosteroid and local anesthetic are rational treatment approaches
to spine pain. Corticosteroid decreases inflammation via inhibition of
prostaglandins in the arachidonic acid cascade, which may in turn improve
microcirculation, capillary permeability, nerve root edema, and ischemia.
Similar to the effect of local anesthetic, corticosteroid may also directly
attenuate the excitation and sensitization of pain-generating C-fiber neurons.
Lidocaine and bupivacaine are well-known direct inhibitors of sodium
channel activation of peripheral nociceptive C-fibers and A-sigma fibers at
the site of tissue injury, reducing peripheral sensitization. When local
anesthetic is administered to the spinal epidural space, it can potentially
inhibit N-methylaspartate–receptor currents critical to a component of central
sensitization.6 The precise mechanisms by which corticosteroid and local
anesthetic act on spinal pain are not completely understood.
Technical Considerations
After it has been decided to proceed with therapeutic spine intervention, the
surgeon must determine the procedural approach, medication, type of image
guidance, timing, and frequency of repeat procedures. These considerations
are especially important in the performance of epidural steroid injections
(ESIs), by far the most widely used pain intervention.
Epidural Steroid Injection
Three approaches exist for entrance to the lumbar epidural space: caudal ESI,
interlaminar ESI, and transforaminal ESI. The selection of approach is based
on a patient’s symptoms, anatomy, pathology, and treatment goals. For any
elective spine procedure, image guidance is the standard of care to optimize
safety, accuracy, and effectiveness. Without image guidance, at least 30% to
50% of interlaminar and caudal epidural injections fail to deliver medication
to the intended epidural space.
9,10
Aspiration alone is insensitive for detecting
potentially catastrophic intravascular needle placement.
5,7
In a caudal ESI, the needle is directed toward the sacral hiatus and a
Figure 1
relatively larger volume of medication is injected to distribute it cephalad, as
high as L4-L5 (Figure 1). Caudal ESI is frequently used in patients with L4L5 or L5-S1 pathology, in whom the anatomy prohibits interlaminar or
transforaminal ESI. For example, patients who have severe scoliosis or who
have previously undergone spine surgery may be treated via caudal ESI.
A, Lateral fluoroscopic view demonstrates epidural contrast
injection into the sacral hiatus via a caudal approach. B, AP
view demonstrates cephalad migration of the epidural contrast.
Interlaminar ESI can be performed at any spinal level at which a
competent ligamentum flavum is present—typically, C6-C7 through L5-S1
(Figure 2). Most often, the needle enters the posterior epidural space via a
paramedian approach, which makes use of a so-called loss of resistance
technique. The injectant may travel several levels cephalad or caudad from
the site of injection.7 Interlaminar ESI is often considered in patients with
bilateral symptoms related to spinal stenosis. This approach should be
avoided at levels of prior posterior spinal surgery, severe stenosis, or
inadequate posterior epidural space, all of which increase the risk for
intrathecal placement.
In transforaminal ESI, the approach to the epidural space is made via an
oblique angle to the lateral foramina. Transforaminal ESI can be performed at
any level in the spine, is thought to be the most selective of all three
approaches, and most consistently delivers medication to the ventral epidural
space near an intervertebral disk herniation (Figure 3). Although this
approach is the best studied, it carries the greatest risk of potentially
catastrophic injection into a radicular artery. Image guidance is required and
optimized with the use of contrast injection under live fluoroscopy and digital
subtraction angiography. Transforaminal ESI is often performed to relieve
radicular pain in the setting of intervertebral disk herniation or stenosis or to
assist with diagnosis through more selective placement of local anesthetic on
a specific nerve.
Radiofrequency Neurotomy
For managing spinal pain, radiofrequency neurotomy (RFN) is typically
performed under biplanar fluoroscopy, with the goal of thermal coagulation
of a nociceptor. Most commonly, the surgeon targets the medial branches of
the primary dorsal rami innervating the spinal facet joint (Figure 4). In
conventional RFN, radiofrequency energy is used to heat a needle tip to
approximately 80°C to create a lesion measuring approximately 1 to 3 mm.
The size of the lesion created is dependent on the size of the needle and
duration of the stimulus. Outcomes of conventional RFN are highly
dependent on technique; the best outcomes are achieved when the needle tip
lies parallel to the target nerve.
5,11
Cooled RFN is a newer, more costly
technique that has some advantages over conventional RFN. Cooled RFN
uses a fluid pump that circulates sterile water to cool the needle tip and
adjacent tissue. Because the probe tip temperature is 60°C, the coagulation
time is longer (approximately 150 seconds), and the lesion size is larger than
with conventional RFN. Moreover, the lesion created using cooled RFN
extends farther beyond the needle tip, allowing easier needle placement,
which is helpful in patients with complex anatomy or who are undergoing SI
joint RFN.12 The larger lesion size generated with cooled RFN warrants
additional caution. After RFN, the coagulated nerves typically regenerate and
can restore nociception to the joint. Although the duration of effect from RFN
varies, at least 50% improvement in pain for at least 6 months constitutes a
positive outcome.
Corticosteroid Selection
The types of corticosteroid commonly used in spine procedures are listed in
Table 1. The US FDA has not approved the epidural use of corticosteroid
and stated in 2014 that effectiveness and safety of epidural steroids has not
been established.13 Bristol-Myers Squibb, the maker of Kenalog
(triamcinolone) changed its package label in 2011 to include a warning
against epidural use of the steroid because of reports of serious medical
events, including death.14 Since 2011, epidural use of triamcinolone has
declined, but off-label use of other corticosteroid brands persists.
Inadvertent intra-arterial injection of a particulate steroid during a
transforaminal ESI can result in embolic infarct of the brain or spinal cord
and cause stroke, blindness, paralysis, or death. Dexamethasone is the only
corticosteroid that is essentially aqueous in solution and does not coagulate
particles larger than red blood cells (Table 1). Theoretically, a particulate
corticosteroid will linger at the site of injection to extend the duration of antiinflammatory effect; most of the early efficacy studies on transforaminal ESIs
used a particulate corticosteroid.15 However, since 2011 multiple studies
have demonstrated essentially equivalent effectiveness with dexamethasone
compared with a particulate corticosteroid for transforaminal ESI.
16,17
A
high-quality study showed that 10% to 15% of patients may require one
additional injection to achieve optimal effect with dexamethasone compared
with particulate steroid, but otherwise steroid selection did not predict
outcome.17 Based on the theoretic improved safety profile and equivalent
effectiveness of dexamethasone compared with other corticosteroids,
dexamethasone has been recommended as the first-line agent for
transforaminal ESI.
16,17
Figure 2
A, Cervical contralateral oblique fluoroscopic view of
epidural contrast injection via a C7-T1 interlaminar
approach. B, AP fluoroscopic view demonstrates cephalad migration
of epidural contrast on the right side of the spinal canal. C, AP
fluoroscopic view of an L2-3 interlaminar epidural approach. D, Lateral
view of a lumbar interlaminar epidural contrast injection demonstrates
cephalad and caudad flow of contrast.
For procedures other than transforaminal ESI, corticosteroid selection
tends to be based more on provider preference than safety concerns. Most
effectiveness studies on interlaminar ESIs, caudal ESIs, and intra-articular
injections used particulate steroids. A recent retrospective series of 531
patients compared response to interlaminar ESI with either 40 mg
triamcinolone or 4 mg dexamethasone and found twice the rate of positive
Figure 3
outcomes at 1-month follow-up in the triamcinolone group.
18
A, Ipsilateral oblique fluoroscopic view demonstrates C7
transforaminal epidural injection of contrast. B, PA
fluoroscopic view demonstrates contrast flow along the right C7 nerve
root. C, AP fluoroscopic view demonstrates transforaminal epidural
contrast flow along the left L4 nerve root. D, Lateral fluoroscopic view
of L4 transforaminal injection demonstrates contrast in the ventral
epidural space.
Timing and Frequency of Injections
Spinal injections should be performed only after treatment goals and
expectations have been established and agreed on. There is no consensus on
the timing and frequency of therapeutic spinal injections, and the historically
used so-called series of three approaches has no scientific basis. If a
technically sound injection does not provide substantial improvement, then
Figure 4
repeating the same injection is not recommended, because only 6% of
patients are likely to respond to the repeat procedure.19 If temporary
improvement is obtained with the first injection, then a repeat injection
between 2 and 4 weeks later can be considered. It may take 1 to 2 weeks to
determine the effectiveness of the injection and 3 to 4 weeks for adrenal
suppression to subside. Typically one or two injections are required to
achieve optimal benefit, and patients rarely need a third injection to address
radicular pain.19 Spine injections should be limited to no more than three in a
6-month period and four in 1 year.
5,15
Successful RFN should not need
repeating more often than every 6 months.
A, AP fluoroscopic view of needle placement for
radiofrequency neurotomy of the left L4 medial branch of
the primary dorsal ramus and the L5 primary dorsal ramus to
denervate the right L5-S1 facet joint in a patient who had previously
undergone L5-S1 disk arthroplasty. B, Lateral fluoroscopic view of the
same patient confirms needle placement at the junction of the superior
articular and transverse processes for denervation of the L4 medial
branch of the primary dorsal ramus and the sacral ala for denervation
of the L5 primary dorsal ramus.
Table 1
There is new research regarding the effect of corticosteroid injection
around the time of spine surgery, including retrospective database analyses of
more than 60,000 patients.
20,21
The following postoperative infection rates
were reported for patients who did not undergo ESI preoperatively: 2% for
posterior cervical surgery, 0.6% for anterior cervical diskectomy and fusion,
and 0.8% for lumbar decompression. If an ESI is performed within 3 months
prior to surgery, postoperative infection rates rise to 4% for posterior cervical
surgery, 0.8% for anterior cervical diskectomy and fusion, and 1.2% for
lumbar decompression, which equates to numbers of 50, 500, and 250,
respectively, needed to harm. Similar analyses of Spine Patient Outcomes
Research Trial (SPORT) and Lumbar Spinal Stenosis Outcome Study
(LSOS) cohorts reported conflicting results.
22,23
Patients in the SPORT
cohort had an increased likelihood of crossover from surgical to nonsurgical
treatment if they underwent an ESI compared with those who had no ESI
(62% versus 33%, respectively); however, patients treated with ESI who
eventually underwent surgery had fusion surgeries lasting an average of 26
minutes longer, longer hospital stays by 1 day, and overall poorer
outcomes.22 In contrast, the LSOS cohort demonstrated no negative or
positive effects of preoperative ESI on postoperative outcomes.23 Additional
studies are needed to definitively determine if and when to avoid ESI around
the time of spine surgery.
Image Guidance
Spine procedures may be performed under fluoroscopy, CT, or
ultrasonography. Fluoroscopy is the most commonly used image guidance
modality. Fluoroscopy was used in the highest quality studies on ESI.
Fluoroscopy has the advantage of multiplanar and real-time visualization of
contrast injection, which is important for reducing the risk of potentially
catastrophic intravascular injection (especially during transforaminal ESIs).
Although routine CT-guided procedures do not allow for real-time
visualization of contrast injection and typically deliver increased amounts of
radiation to the patient, axial CT views are useful in patients who require
either transforaminal ESI in a region of severe spinal deformity (such as
scoliosis) or intra-articular injection to severely arthritic joints (such as the
lateral atlantoaxial joint). Musculoskeletal ultrasonography is a developing
modality for spine interventions, with techniques described for most spine
procedures.24 When used by an experienced surgeon, ultrasonography is
helpful in the effective delivery of medications to the target structure.
However, the failure of ultrasonography to detect real-time intravascular flow
limits its safety and utility for transforaminal epidural procedures. Safety and
efficacy studies are needed to further define the role of ultrasonography for
spine procedures.
Indications for Percutaneous Interventions
The potential benefits from spine interventional procedures are determined by
the particular indication and the individualized treatment goals. As a
diagnostic tool, spine intervention procedures can be used to confirm a
suspected diagnosis, rule out a competing diagnosis, and predict patient
response to more aggressive treatments, such as decompression surgery to
manage radicular pain or RFN to manage facet joint pain. The short- or
medium-term pain relief from percutaneous intervention may be highly
beneficial to a patient for whom a rehabilitation program is unsuccessful as a
result of moderate or severe pain, or in a patient in whom the natural history
of the painful condition is likely to improve with time, such as radicular pain
resulting from an intervertebral disk herniation. With the exception of
successful RFN for managing chronic facet joint pain, the benefits of
percutaneous intervention in patients who have chronic stable pain but for
whom no defined functional rehabilitation goals exist are less clear and less
predictable. Although percutaneous spine procedures are beneficial for
managing pain, they have not been widely demonstrated to improve other
spine-related symptoms, such as weakness, numbness, and incoordination.
The most common indications for spine interventions are lumbar radicular
pain resulting from disk herniation, lumbar radicular pain or neurogenic
claudication resulting from spinal stenosis, and cervical radicular pain.
Lumbar Radicular Pain Resulting From Disk Herniation
Lumbar radicular pain resulting from intervertebral disk herniation is the
most common and well-accepted indication for ESI.
15,19
Evaluation of the
efficacy of ESI is challenging because, historically, studies have included
variable treatment protocols, patient selection, and outcome measures. In
addition, early research focused on interlaminar ESI without image guidance.
More recent research has been of higher quality and primarily studied
fluoroscopically guided transforaminal ESIs. In 2013, the North American
Spine Society published a consensus statement that included a grade A
recommendation for transforaminal ESI to manage radicular pain resulting
from lumbar intervertebral disk herniation.15 The best level I study, which
was published in 2010, included 150 patients who were deemed surgical
candidates to manage lumbar intervertebral disk herniation in conjunction
with acute or chronic radicular pain.25 Patients treated with transforaminal
ESI had substantially more responders (≥50% improvement in pain,
improved function, decreased healthcare needs) at 1 month postinjection
compared with patients treated with transforaminal normal saline,
transforaminal local anesthetic, intramuscular steroid, or intramuscular
normal saline. More than 50% of patients in the transforaminal ESI group
responded at 1 month postinjection, and 25% responded at 1 year
postinjection. The number needed to treat (NNT) for transforaminal ESI
compared with transforaminal normal saline was 2 to 3 for response at 1
month postinjection and 4 to 5 for response at 3, 6, and 12 months
postinjection. Pooled effectiveness data from multiple level I and II studies
and reviews indicate that 60% to 70% of patients experience at least 50%
pain relief for 1 to 2 months postinjection, and 25% to 40% of patients
experience this percentage of improvement at 1 year postinjection.
5,19
No high-quality, prospective, placebo-controlled trials have been done on
interlaminar ESIs and caudal ESIs. Level II and III studies of fluoroscopically
guided interlaminar ESI and caudal ESI report short-term pain relief, with
variable improvement beyond 1 month postinjection.5 Furthermore,
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