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Reviews and Commentary
Spinal Injections for Pain
Image-guided spinal injection is commonly performed in
symptomatic patients to decrease pain severity, confirm
the pain generator, and delay or avoid surgery. This article focuses on the radiologist as spine interventionist and
addresses the following four topics relevant to the radiologist who performs corticosteroid injections for pain management: (a) the rationale behind corticosteroid injection,
(b) the interaction with patients, (c) the role of imaging
in procedural selection and planning, and (d) the pearls
and pitfalls of fluoroscopically guided injections. Factors
that contribute to the success of a pain management service include communication skills and risk mitigation. A
critical factor is the correlation of clinical symptoms with
magnetic resonance (MR) imaging findings. Radiologists
can leverage their training in MR image interpretation to
distinguish active pain generators in the spine from incidental abnormalities. Knowledge of fluoroscopic anatomy
and patterns of contrast material flow guide the planning
and execution of safe and effective needle placement.
RSNA, 2016
Online supplemental material is available for this article.
From the Department of Musculoskeletal Radiology,
Massachusetts General Hospital, 55 Fruit St, YAW 6030,
Boston, MA 02114. Received September 17, 2015;
revision requested October 23; revision received January
26, 2016; accepted February 19; final version accepted
March 30. Address correspondence to the author (e-mail:
[email protected]).
RSNA, 2016
Radiology: Volume 281: Number 3—December 2016
n How I Do It
William E. Palmer, MD
HOW I DO IT: Spinal Injections for Pain Management
n 1930, epidural anesthetic injection was described in the treatment
of sciatica (1). Epidural steroid
injection (ESI) was first performed
in the 1950s, it evolved as a therapeutic option during the 1960s, and
it became a cornerstone in the management of low back pain and sciatica
in the 1970s (2–6). During these decades, needle placement and injection
site depended on palpated landmarks
and loss-of-resistance techniques. In
the 1980s and 1990s, radiologists and
nn Structured interactions during
history taking, intervention, and
discharge build patient-physician
relationships that promote trust
and create rewarding opportunities for radiologists to counsel
patients and affect clinical
decision making.
nn Correlation of symptoms and imaging findings guides targeted
inspection of MR images, differentiation of active pain generators in the spine from painless
structural abnormalities, and formulation of a treatment strategy.
nn Radiologists can leverage their
training in MR image interpretation, their knowledge of fluoroscopic anatomy, and their experience with contrast material
administration to plan and execute safe and effective needle
nn Therapeutic outcomes depend on
four factors: symptoms correlate
with MR imaging findings, symptoms result from inflammation,
inflammation is reversible, and
corticosteroid reaches the
inflamed tissue.
nn Corticosteroid injection has been
performed for decades for pain
management; however, it is considered an off-label use in spine
intervention in the United States
because the Federal Drug Administration has not approved corticosteroids for epidural or epiradicular administration.
anesthesiologists began to use fluoroscopy to determine the accuracy of
caudal and interlaminar needle placement, and they used epidurography to
understand patterns of injectate flow.
They found needle misplacements in
25%–38% of blind procedures performed by experienced injectionists
(7–9). Epidurography was necessary
to confirm injectate location and to exclude intravascular or intrathecal administration (10–13).
Computed tomography (CT) and
magnetic resonance (MR) imaging
spurred growth in intervention by revolutionizing the noninvasive diagnosis of
pain generators (14,15). When spinal
stenosis, disk herniation, and facet arthropathy correlated with symptoms,
they were targeted for therapeutic interventions. When the correlation was
uncertain, they were targeted for a systematic series of diagnostic interventions. ESIs shifted from caudal routes
performed blindly to lumbar and cervical routes directed at the imaging abnormalities and presumed pain sources (16). As fluoroscopic techniques
evolved, facet injection, nerve root
block (NRB), and discography were
added to lumbar and cervical ESIs (17).
During the 1980s and 1990s, utilization data showed dramatic volume
growth as spinal interventions gained
widespread acceptance (18,19). Lumbar ESI rates for spinal stenosis increased 300% within 2 decades (from
1994 to 2011) (20–23). By 2010, more
than 2.2 million lumbar ESIs were performed yearly in Medicare patients
(21). Facet injections surged 147%
from 1993 to 1999 and increased another 300% from 1998 to 2006 (23–
26). Medicare payments for spinal injections expanded 629% from 1994 to
2001 (23). Before 2000, anesthesiologists performed the majority of injections (26). By 2007, procedures were
performed by anesthesiologists (49%),
physiatrists (25%), family practitioners
(12%), orthopedists (6%), and radiologists (3%) (27). Within the pain management domain, a small percentage of
providers performed a disproportionately high percentage of spinal interventions (22,23,26,27).
Overuse led to the scrutiny of therapeutic outcomes and the publication
of contradictory articles that defended
or criticized injections depending on
the interests of the authors (16,26,28–
38). Epidemiologists tended to focus
on long-term outcomes and surgical
end points. Injectionists focused on
short-term outcomes, accepting the
fact that interventions could modulate
but not cure the underlying cause of
symptoms. Research studies remain
difficult to compare due to disparate
symptoms (back pain vs radiculopathy),
diagnoses (spinal stenosis vs disk herniation), injection types (interlaminar
vs transforaminal), procedural techniques (blind injection vs fluoroscopic
guidance), patient demographics, pharmaceutical agents, and drug doses
Corticosteroid Properties
Corticosteroids are powerful anti-inflammatory medications. The rationale
for administration is the suppression
of inflammation implicated in the pathogenesis of radiculopathy and axial
pain (42). Inflammation as a generic
physiologic response can be triggered
by numerous stimuli. In disk herniation and spondylosis, radiculopathy results from both chemical and mechanical irritants (43–45). Phospholipase
A2 and other enzymes are released
into the epidural space by disk material and annular tear. These inflammatory mediators recruit macrophages
that secrete cytokines and catalyze the
inflammatory cascade; they produce
prostaglandins and leukotrienes that
sustain the inflammatory cycle (46).
Mechanical nerve root stretching,
tethering, and compression provoke
Published online
10.1148/radiol.2016152055 Content codes:
Radiology 2016; 281:669–688
ESI = epidural steroid injection
FDA = Food and Drug Administration
NRB = nerve root block
Conflicts of interest are listed at the end of this article.
Radiology: Volume 281: Number 3—December 2016
HOW I DO IT: Spinal Injections for Pain Management
the same inflammatory reaction due
to cellular damage and ischemic injury (47). Corticosteroids inhibit the
release of cytokines and the synthesis
of prostaglandins, thereby suppressing
the physiologic response (42,48).
Injectable corticosteroids are nonparticulate or particulate. Nonparticulate corticosteroids have rapid-onset
effects, whereas particulate corticosteroids have delayed but sustained
effects. Nonparticulate preparations,
sodium phosphate, are fully soluble
and clear in appearance. Particulate
suspensions contain corticosteroid
esters that are insoluble in saline, local anesthetic, and iodinated contrast
material (49). Particulate corticosteroids, including methylprednisolone
acetate, triamcinolone acetonide,
and betamethasone acetate, create a
white cloudy mixture when agitated.
Methylprednisolone has the largest
particles, whereas betamethasone has
the smallest (49–51).
Particulate corticosteroids have
been associated with neurologic damage during transforaminal cervical and
lumbar injections (51–54). Because of
limited data, the incidence of these
rare complications cannot be determined (55). The proposed mechanism
is direct intra-arterial administration
resulting in embolic occlusion followed
immediately by ischemia or infarction
of neural tissue (Figs 1, 2). Neurologic
sequelae, including quadriplegia, paraplegia, and death, are extremely rare
but catastrophic complications, causing some authors to advocate use of
a nonparticulate corticosteroid in all
transforaminal procedures (50,56,57).
No neurologic complications due to
nonparticulate corticosteroid use have
been reported (58).
In April 2014, the Food and Drug
Administration (FDA) posted a safety
announcement requiring manufacturers to add a warning in package inserts about adverse neurologic events
(59). In that same posting, the FDA
stated: “Injecting corticosteroids into
the epidural space of the spine has
Radiology: Volume 281: Number 3—December 2016
Figure 1
Figure 1: Schematic drawing of the prone lumbar spine shows lumbar structures, needle placements, and
cross-sectional relationships of structures in the spinal canal and foramina. Radicular arteries may be paired,
unilateral, or absent. In lumbar NRB, the needle targets the epiradicular space that surrounds the ventral ramus of the spinal nerve, the dorsal root ganglion (∗), and the nerve roots. In ESI, the needle targets the small
triangle of fat in the dorsal epidural space. In lumbar facet injection (F1), needle trajectory must account for
joint curvature. Otherwise, joint access is blocked by margins of articulating processes (F2).
been a widespread practice for many
decades; however, the effectiveness
and safety of the drugs for this use
have not been established, and FDA
has not approved corticosteroids for
such use.” Several professional societies responded to this FDA safety
announcement, expressing concern
that the FDA warning did “not differentiate between the risks and benefits
of transforaminal versus interlaminar
routes of administration, and particulate versus non-particulate formulations of steroids” (60).
Numerous factors influence the
choice of injected corticosteroid, including FDA warnings, published articles, recommendations from specialty
societies, and package inserts. Data
from these varied sources may be
contradictory, requiring judgments on
safety and efficacy based on personal
experience, the regulatory environment, and the availability of drugs in
the hospital formulary.
Interaction with Patients
Structured interactions promote trust
and build patient-physician relationships that can last for years in individuals who suffer from chronic neck or
back pain and who return for periodic
injections. In my practice, these interactions are important because patients
relay their positive and negative experiences to referring physicians. These
interactions also create rewarding opportunities for radiologists to counsel
patients and affect clinical decision
making. Patients actively seek the perspective of nonsurgeons. Radiologists
should understand the treatment options and lifestyle modifications that
help patients stay active.
During procedural visits, I engage
patients at four junctures to obtain or
convey information. These purposeful
interactions can be categorized as the
interview, the blow-by-blow, the teachable moment, and the discharge. The
HOW I DO IT: Spinal Injections for Pain Management
Figure 2
Figure 2: Cervical structures and needle placement
for NRB. (a) Schematic drawing of the supine cervical
spine depicts cross-sectional relationships of structures
in the spinal canal and foramina. Radicular and segmental medullary arteries are too small to identify with MR
imaging. In cervical NRB, needle placement is posterior to great vessels and nerve plexus. The needle
targets the foramen posteriorly and inferiorly in close
proximity to the exiting nerve and dorsal root ganglion
(∗). AS = anterior scalene muscle, CA = carotid artery,
JV = jugular vein, MS = middle scalene muscle. (b)
CT angiographic image at C5–6 disk level shows
posterior location of the jugular vein (JV). A graphically
depicted needle (NRB) is overlaid at 45° and shows
superimposition on the external jugular vein (EJ). To shift
the great vessels from the needle path during cervical
NRB, turn the head away from the symptomatic side.
Lateral approach may be necessary when MR imaging
reveals great vessels in a posterior location. Enhancing
vessels (arrows) surround nerve root ganglia (∗) in
foramina. CA = carotid artery, VA = vertebral artery.
first interaction, the interview, focuses
on clinical history and incorporates the
consent process. The second and third
interactions, the blow-by-blow and the
teachable moment, respectively, take
place during and immediately after the
intervention while the patient lies on
the fluoroscopy table. The final interaction, the discharge, occurs once the patient is dressed and is waiting to leave.
The Interview
The patient interview is critical in
procedural selection and planning.
I have four goals: (a) obtain a focused clinical history, (b) correlate
symptoms with imaging findings, (c)
approve the requested procedure or
propose a different one, and (d) obtain written informed consent. In new
patients, these goals often can be accomplished within 10 minutes. In returning patients, less time is required
because usually little has changed and
previously successful procedures can
be repeated. It only takes a few questions to determine the outcome of the
prior injection and reestablish the
pain generator.
During history taking, one should
focus on spine-related symptoms. Systematic questioning (Fig 3) quickly
yields enough clinical information to
guide the targeted inspection of imaging studies and the formulation of a
treatment plan (correlation of symptoms and imaging findings is addressed
in the next section). Begin with the
discrimination of axial pain from radiculopathy. When leg and back pain
coexist, ask which one is predominant.
Most patients would be willing to live
Radiology: Volume 281: Number 3—December 2016
HOW I DO IT: Spinal Injections for Pain Management
symptom-imaging correlation), and
procedural selection. Explain the procedure, and educate the patient about
risks. It may be necessary to disclose
that the FDA has not approved corticosteroids for epidural administration. Besides fulfilling ethical and regulatory requirements, the consent process should
uncover clinical conditions, medications,
and allergies that increase risk and compromise outcome. The major issues are
anticoagulation therapy, active infection,
and contrast material reaction. When
you are describing bleeding and infection risks, ask about anticoagulant and
antibiotic treatments. Inquire about latex allergy, diabetes, and other recent
steroid injections. In my practice, our
administrative assistant screens patients
prior to the procedure to avoid the discovery of unresolvable issues, such as
anticoagulation therapy, in the fluoroscopy suite.
Figure 3
Figure 3: Flowchart shows interview questions to be asked during history
taking. A = answer, Q = question.
with the lesser pain if the major pain
could be relieved.
Radicular symptoms often enable
one to verify the pain generator during
imaging correlation. In contrast, nonspecific axial pain poses diagnostic challenges. It can be acute or chronic, mild
or severe, intermittent or constant, dull
or sharp, localized or migratory, or any
Radiology: Volume 281: Number 3—December 2016
combination thereof. Patients often
point to a general region in the neck
or low back. Clinical history and physical examination have limited value in
determining the cause of axial pain and
guiding procedural selection (61).
Informed consent follows history taking, correlation of symptoms
with imaging findings (hereafter,
The Blow-by-Blow
Occasionally, patients refuse to receive
information during the procedure. As a
coping strategy, they wear headphones
to listen to music, or they prefer silence,
choosing to mentally transport themselves to another place. However, most
patients want to know what is happening
and value a blow-by-blow narrative. The
blow-by-blow serves several purposes.
Patients feel connected and informed.
It relieves anxiety and eliminates the
element of surprise. It conveys forward
progress. Verbal communication also engages the technologist, fellow, and any
other individuals involved in the procedure. My custom is to announce when I
am deciding where to insert the needle,
putting a dot on the skin with a marker,
cleaning the skin, preparing the medications, numbing the skin, positioning the
needle, and injecting dye to make sure
the needle is in the right place. I express
my satisfaction with needle placement
before I inject the steroid solution. During injection, I warn patients that the
injection could cause pressure or pain.
When concordant symptoms are produced, I reassure patients and state that
the needle is correctly placed. Patients
appreciate knowing that the procedure
is going as expected.
HOW I DO IT: Spinal Injections for Pain Management
The Teachable Moment
The teachable moment begins immediately after needle removal while washing off the skin antiseptic. To set positive expectations, state that the goal
of the procedure was achieved (ie, the
steroid was delivered to the intended
target). Indicate the rationale for injecting the steroid. Explain that the steroid
works by decreasing inflammation, not
by shrinking the disk herniation, reversing arthritis, or opening stenotic
spinal canals. Patients should understand that the drug is a powerful anti-inflammatory agent but that the degree of pain relief depends on whether
inflammation is causing the symptoms.
In patients who might benefit from seeing the fluoroscopic images, reinforce
the technical success of the procedure
by pointing out needle placement and
contrast material flow on the monitor.
The Discharge
The discharge process generates information about immediate pain response. Symptoms might be decreased,
unchanged, or increased depending on
the level of preprocedural pain and the
volume of injected anesthetic. Prompt
pain relief creates a positive attitude
about the procedure and promotes the
placebo effect. A surprising number
of patients claim pain reduction even
if no local anesthetic was injected. In
dictated reports, record the postprocedural pain response (eg, right leg pain
decreased from a score of 8 of 10 to
a score of 2 of 10). If symptoms are
already improved at the time of discharge, I continue to set positive expectations by explaining to the patient that
the steroid was mixed with anesthetic
and, therefore, it is in the same correct
One must explain the time frame
for steroid effectiveness and provide
activity guidelines. Patients can become
disappointed the day after injection if
their pain remains unchanged. Because
particles release the steroid gradually,
it may take 12–24 hours for the drug
to take effect, 4–6 days for its effects
to become more pronounced, and
more than a week for it to reach full
effectiveness. Advise patients to limit
themselves to baseline levels of exercise
and physical therapy for 4–6 days. Patients whose condition improves after
2–3 days are tempted to overdo it before the drug has reached full effectiveness, thereby stirring up inflammation
that overwhelms the steroid and diminishes the overall treatment benefit.
Patients often ask how long the
injection will help. The time course is
surprisingly predictable in patients with
chronic conditions, such as spinal stenosis and facet arthropathy. Symptoms
decrease during the first 2–3 weeks
after injection when the anti-inflammatory effects are strongest but return to
baseline levels over the following 6–8
weeks as the particulate steroid dissipates. In patients with acute conditions,
such as disk herniation and annular
tear, the steroid can break the inflammatory cycle and relieve pain for more
than 6–8 weeks. When new symptoms
are superimposed on long-standing
ones, such as acute radiculopathy superimposed on chronic low back pain,
explain that corticosteroid injection
may accelerate a return to the baseline
condition. Steroid administration decreases the new reversible nocioceptive
pain but leaves the long-standing irreversible neuropathic pain unchanged.
Role of Imaging in Procedural Selection
Symptom-imaging correlation guides
procedural selection and planning
(Movie 1 [online]). It enables one to
verify the appropriateness of the requested intervention or justify modification. Procedural modification is most
practical when the radiologist has authorization to proceed independently.
For the radiologist who possesses the
skill, experience, and confidence to
assume responsibility for treatment
decisions and, therefore, therapeutic
outcomes, the role in pain management
expands beyond rote injection.
Imaging results are available in the
majority of cases. During screening, our
administrative assistant asks patients to
bring their MR images if they were obtained at a different institution. On rare
occasions, we proceed without the benefit of symptom-imaging correlation.
Procedural selection begins with a
judgment on the pain generator. The
following symptom-imaging correlation
exercise is popular with our fellows
because it hones skills in both history
taking and MR image interpretation.
The exercise has two variations. In
one variation, we interview the patient
before we review the MR images. We
then deduce the most likely pain generator and predict the MR imaging findings. In the other variation, we review
the MR images before we interview
the patient, then we deduce the most
likely pain generator and predict the
patient’s symptoms. Symptom-imaging
correlations are often obvious, but surprising mismatches do occur. These
mismatches teach valuable nuances
in pain management and MR image
In younger patients with acute or
subacute radiculopathy, dermatomal information serves to focus MR image review. Symptoms usually correlate perfectly with nerve entrapment because
of lateralization of single-level disk abnormalities. Occasionally, a symptomspecific search will lead to the diagnosis of an intraforaminal or lateral disk
extrusion that explains symptoms but
that was overlooked at the time of MR
image interpretation (Fig 4). Transforaminal NRB targets the pain generator
and delivers the steroid directly to the
inflamed nerve root (62–64) (Figs 5, 6).
In older patients with chronic unilateral radiculopathy, symptom-imaging
correlation is more challenging because
of multilevel spondylosis. Therapeutic success is also more challenging
when severe stenosis causes irreversible nerve damage and neuropathic
pain. Transforaminal NRB remains a
recommended treatment option if dermatomal information reveals a specific
pain generator. One exception is nerve
compression by a facet cyst. To address
this problem, one can combine percutaneous cyst rupture with intra-articular
corticosteroid injection (65) (Fig 7).
In older patients with chronic bilateral radiculopathy, the radiologist
should solicit signs of neurogenic claudication. Intermittent back pain is precipitated by prolonged standing or
Radiology: Volume 281: Number 3—December 2016
HOW I DO IT: Spinal Injections for Pain Management
Figure 4
Figure 5
Figure 4: Intraforaminal disk extrusion missed at prospective interpretation in
a 41-year-old woman with acute L4 radiculopathy. Axial T2-weighted MR image
shows unsuspected L4–5 intraforaminal disk extrusion (white arrowhead)
causing mechanical impingement on left L4 nerve root ganglion (arrow). During
NRB (not shown), the needle targeted the L4 ventral ramus peripheral to the
foramen to avoid severe pain production due to foraminal stenosis and nerve
root displacement. Right L4 nerve root ganglion (black arrowhead) is in its
normal location and is surrounded by fat.
walking and is relieved by sitting or
leaning forward. One should expect MR
imaging to reveal spinal stenosis, which
is the leading reason for spinal surgery
(18). When MR imaging shows multilevel stenosis, dermatomal information
may indicate the level of pain generator.
Interlaminar ESI is the recommended
procedure because the corticosteroid
can spread cranially and caudally over
multiple disk levels.
When symptoms suggest lumbar facet syndrome (posterior ramus
syndrome), one must scrutinize the
zygapophyseal joints for signs of inflammation, including effusion, capsulitis,
and periarticular edema. Back pain
may radiate into the buttocks, groin,
or posterior thigh and may worsen with
prolonged standing and extension and
rotation or lateral bending movements
(71). Sclerotomal maps for posterior
rami depict the patterns of referred
pain from facet joints but are less accurate than dermatomal maps for patterns of referred pain from ventral rami
(72). Clinical history and physical examination findings cannot be used to
Radiology: Volume 281: Number 3—December 2016
predict treatment responses to facet injections (73). If corticosteroid administration alleviates symptoms, systematic
anesthetic injections (medial branch
blocks) yield corroborative diagnostic
information prior to radiofrequency
Segmental instability creates multiple pain generators and causes debilitating symptoms that respond poorly
to injections. Initially, when back pain
predominates, symptoms may respond
to ESI, facet injections, or a combination thereof. Progressive facet degeneration leads to articular hypermobility,
attritional bone loss, and malalignment. Increasing anterolisthesis exacerbates spinal stenosis and foraminal
nerve impingement. When neurogenic
claudication and radiculopathy become
superimposed on back pain, segmental
instability often forces surgical intervention and spinal fusion.
In patients with chronic nonlocalizing low back pain, one must inspect
disks and facets to judge the relative importance of discogenic and arthropathic abnormalities. The basic
Figure 5: Lumbar NRB in a 64-year-old
man with right leg pain correlating with
L4–5 lateral recess stenosis and right L5 mechanical impingement. Anteroposterior fluoroscopic image in the prone position shows the
needle (arrow) in supraneural location between
L5 and S1 pedicles (∗). Contrast material
(arrowheads) flows cranially into the spinal canal
along the L5 epiradicular space to the level of
the L4–5 disk space and pain generator in lateral
procedural alternatives are ESI and facet injection. These limited choices seem
trivial enough, but decision making can
be problematic due to overlapping clinical syndromes and equivocal MR imaging findings (66–68). Incidental MR
imaging abnormalities in asymptomatic
adults are difficult to discriminate from
true pain sources in symptomatic patients (15,61,69,70). The default intervention is ESI. In the absence of MR imaging findings that support a different
level of injection, the radiologist should
select the L4–5 level because injectate
typically flows cranially and caudally,
and it will cover the three lowest movable disk spaces.
One should inspect MR images for
bone marrow edema involving facets,
pars defects, spinous processes (Baastrup syndrome), and lumbosacral pseudoarthroses (Bertolotti syndrome).
When symptoms are highly localized,
ask the patient to point to the most
painful spot and document that site
fluoroscopically, including the pointing
HOW I DO IT: Spinal Injections for Pain Management
Figure 6
Figure 6: Cervical NRB in 41-year-old woman with left arm pain correlating with C6–7 disk extrusion and left C7 mechanical impingement. (a) Oblique fluoroscopic
image obtained in the supine position shows foramina (curved lines) are opened by lateral rotation of the detector approximately 45°. During set-up, turn the head
away from the side of needle placement, thereby displacing the great vessels and nerve plexus from the needle path. The needle tip (arrow) is directed inferiorly
toward C6–7 foramen to target exiting left C7 nerve and posteriorly to avoid vertebral artery. The needle hub has been preloaded with contrast material (arrowhead)
to obviate gas injection. (b) Digital subtraction posteroanterior fluoroscopic image shows contrast material (arrowheads) flowing along the epiradicular space into the
foramen between C6 and C7 pedicles (∗). Subtraction technique may improve detection of intravascular contrast material. The needle (arrow) is barely visible. (c)
Subsequent posteroanterior fluoroscopic image shows contrast material (arrowheads) spreading along C7 nerve between pedicles (∗) into the epidural space. The
needle (arrow) terminates at the border of lateral masses. It can be advanced into outer foraminal thirds if contrast material flow is unsatisfactory (intravascular or
Figure 7
Figure 7: Facet cyst rupture in 71-year-old man with left L5 radiculopathy correlating with left L5-S1 foraminal cyst. (a) Axial T2-weighted MR image at L5-S1
level shows foraminal cyst (straight arrow) is contiguous with degenerated left L5-S1 facet joint (curved arrow) and proximate to left L5 nerve (arrowhead). (b)
Anteroposterior fluoroscopic image in the prone position shows contrast material in the needle hub (straight arrow) and facet cyst (curved arrow). The inferior recess
of the left L5-S1 facet joint was accessed with anteroposterior fluoroscopy by moving the needle caudally off the articulating process. (c) Subsequent anteroposterior
fluoroscopic image shows epidural flow of contrast material (arrowheads), indicating cyst rupture. Contrast material no longer fills the cyst or needle hub (arrow).
Corticosteroid may prevent or delay recurrence of facet cyst.
finger. If this site corresponds to bone
marrow edema or another potential
pain generator on MR images, it can be
targeted for diagnostic information and
therapeutic response.
Pearls and Pitfalls of Fluoroscopyguided Injections
The following pearls and pitfalls focus
on fluoroscopy-guided injections (Movie
2 [online]). Expert interventionalists
develop individualized techniques and
often approach the same problems and
procedures in different ways. Some
physicians prefer to use computed
Radiology: Volume 281: Number 3—December 2016
HOW I DO IT: Spinal Injections for Pain Management
tomography (CT) to guide needle placement (74–80). This preference reflects
training experience, resource availability, and institutional policy. No studies
have compared the effectiveness or
safety of CT-guided interventions versus
fluoroscopy-guided interventions. Neurologic complications have occurred
during spine injections performed with
both modalities (81–84).
Advantages of CT include higher
reimbursement and cross-sectional
documentation of needle position. CT
may improve the accuracy and safety
of needle placement when overlapping
bones make it difficult to plan an unobstructed needle trajectory during fluoroscopic set-up and when intervening
soft-tissue structures must be avoided
but cannot be seen fluoroscopically. In
thoracic NRB, for example, CT shows
the complex relationship between the
ribs, transverse processes, and lung.
For atlantoaxial (C1–2) facet injection,
CT helps to avert complications from
arterial puncture by depicting the vertebral artery (82). In lumbar facet injection, when intraarticular placement
is essential for diagnostic information
or therapeutic cyst rupture, CT shows
marginal osteophytes and hairline joint
spaces (85).
Disadvantages of CT include higher
cost, increased radiation dose, longer
procedural time, and lack of availability. The radiation dose of CT interventions can be decreased to the level of
fluoroscopic interventions by using a
low-dose protocol that eliminates acquisition of a topogram, minimizes both
energy and tube current, and severely
restricts the number of image acquisitions during needle placement (86–88).
At institutions where interventional
CT is a limited resource, CT-guided injections for pain management can be
challenging to schedule if they must
compete for scanner time with biopsy,
oncologic ablation, and abscess drainage procedures.
An advantage of fluoroscopy is the
live real-time observation of contrast
material flow and, therefore, vessel
opacification in the case of inadvertent intravascular needle placement.
During CT-guided procedures, because
Radiology: Volume 281: Number 3—December 2016
conventional scanning is delayed until
operators leave the room, intravascular
contrast material washes away, thereby
precluding vessel identification. Intermittent fluoroscopy, if performed before
and after but not during contrast material injection, also fails to show opacified vessels (52,89). In mixed injections
with concurrent intra- and extravascular contrast material flow, only the extravascular contrast material remains
visible, creating the false reassurance of
extravascular needle placement. Some
authors have proposed the use of CTfluoroscopic techniques to improve the
real-time detection of opacified vessels
(90–92). However, vessels outside of
the limited stack of CT images remain
impossible to identify.
A potential advantage of fluoroscopy is the range of detector rotation,
which enables steep craniocaudal angulation. Steeper craniocaudal angles are
often required in L5 and S1 NRBs, as
well as in lumbar ESIs, in the setting
of interlaminar collapse or exaggerated
lumbar lordosis.
The advantages of both modalities can be attained with one unit
that combines C-arm fluoroscopy with
cone-beam CT (93,94). The flat-panel
detector spins and acquires a volumetric data set enabling multiplanar
two-dimensional reformations and
three-dimensional reconstructions. Because the fluoroscopic image is overlaid onto the three-dimensional data
set, the unit can align itself according to selected skin entry and target
locations for bull’s-eye needle navigation. If necessary, final needle position and contrast material location are
documented with a second volumetric
Risk and Risk Mitigation
Adverse events are exceedingly rare
when experienced practitioners use
fluoroscopic guidance and inject contrast material to confirm needle position (16). In more than 8000 cervical,
thoracic, and lumbar interventions performed by me or under my supervision,
none have been complicated by hemorrhage, infection, or neurologic damage. Radiologists should recognize and
manage immediate and delayed complications or perform patient triage for
appropriate care. Adverse events can
occur during injection (pain, hemorrhage, reaction to contrast material, vasovagal reaction, dural puncture, nerve
or vessel damage), immediately after
injection (pain, hemorrhage, extremity
weakness, paresthesia), or days later
(infection, headache, flushing reaction
to steroid). Most adverse events can be
avoided by anticipating risks discovered
during history taking and image review.
Bleeding risk increases with age,
underlying coagulopathy, severity of
spondylopathy, and difficulty of needle
placement (95). Although the incidence
is unknown, bleeding risk increases in
patients who have undergone anticoagulation therapy, and it increases substantially in patients taking multiple anticoagulant and antiplatelet medications,
including nonsteroidal anti-inflammatory drugs (95). Epidural hematoma
rarely occurs; however, it poses the
greatest threat because of spinal cord
or cauda equina compression, and it
requires surgical evacuation to prevent
permanent neurologic sequelae. Incidence has been estimated at 1:220 000
after subarachnoid anesthesia and at
1:150 000 after epidural anesthesia in
healthy patients (96). Epidural hematoma has been described after ESI and
facet injection in patients without coagulopathy or anticoagulation therapy
(96). Patients should discontinue use
of anticoagulants for appropriate intervals, and they should coordinate bridging therapy according to instructions
from referring physicians or consulting
cardiologists (97). ESI is considered
safe in patients taking nonsteroidal anti-inflammatory drugs (98). In a study
of 1214 patients who underwent ESI,
no hemorrhagic complications occurred
in 383 (32%) patients taking nonsteroidal anti-inflammatory drugs (98).
Iodinated contrast material should
be approved for myelography in case of
inadvertent intrathecal administration.
One should recognize patterns of layering subarachnoid contrast to avoid saddle anesthesia and ascending paralysis
from anesthetics and arachnoiditis from
corticosteroids. Nearly 3% of scheduled
HOW I DO IT: Spinal Injections for Pain Management
Figure 8
Figure 8: Intravenous injection during interlaminar
ESI in a 48-year-old woman with axial low back
pain after L4–5 anterior fusion. Lateral fluoroscopic
image obtained during contrast material injection
shows needle tip (arrow) projecting over the spinal
canal at L3–4 disk level. Extensive epidural venous
network (arrowheads) is visible from L2 to L5.
Needle repositioning could not evade vessels. Thus,
ESI was performed at L2–3 (images not shown).
∗ = L4–5 interbody cage.
patients have had known or suspected
reactions to contrast material (16). In
these patients, options include (a) premedication with oral prednisone and
diphenhydramine, (b) steroid injection
without contrast material confirmation
of needle location, and (c) injection
of a gadolinium-based contrast agent.
Gadolinium chelates provide off-label
alternatives to iodinated contrast material and appear safe for use in epidural
injection (99). Intrathecal administration should be carefully avoided. Digital
subtraction fluoroscopy may improve
visualization of gadolinium-based contrast material, which is less radiopaque
than iodinated contrast material.
Extensive arterial and venous networks crisscross the epidural and epiradicular spaces of the spinal canal and
neural foramina (Figs 1, 2, 8). Overall,
intravenous needle placements are
more common in patients with cervical
NRBs (incidence range, 19.4%–32.8%)
than in those with lumbar NRBs (incidence range, 11.2%–13.1%), but actual
incidence depends on injection level
(10–13). In the cervical spine, vascular
cannulation is more likely from C3–4
to C5–6 (range, 40%–57%) (13). In
the lumbosacral spine, it is more than
twice as likely at S1 (21.3% incidence)
compared to lumbar levels (8.1% incidence) (10–12). In both the cervical
spine and the lumbar spine, aspiration
fails to produce a flashback of blood in
45%–73% of intravenous needle placements subsequently proved via contrast
material opacification (10,100).
Simultaneous intra- and extravascular contrast material flow (mixed injection) is observed more commonly than
is intravascular flow alone in both cervical NRBs and lumbar NRBs (12,13).
In the cervical spine, mixed injection
was reported in 18.9% of injections
as compared with vascular flow alone,
which was reported in 13.9% of injections (13). Concurrent flow creates
challenges because extravascular contrast material can obscure vessels. To
best detect vessels, one should optimize
fluoroscopic techniques by decreasing
the field of view, dimming the lights, using digital subtraction angiography, and
injecting contrast agents that contain a
higher concentration of organic iodine
(eg, 300 mg/mL).
Injected steroids have systemic glucocorticoid effects in addition to local
anti-inflammatory effects. Fortuitous
benefits include temporarily decreased
pain from arthritis and spondyloarthropathy. Undesired consequences
include elevation of the blood glucose level, suppression of the immune
system, and suppression of the hypothalamic-pituitary axis. One should
caution patients with diabetes to monitor their blood glucose levels for 7–10
days after the procedure. Ask patients
about antibiotics they are taking, and
reschedule patients who are taking antibiotics for active infections. Prophylactic antibiotics are not a contraindication. Repeated steroid injections at
short intervals (less than 8 weeks for
particulate preparations) can inhibit
recovery of the hypothalamic-pituitary
axis and can lead to decreased bone
mineral density (101–103). Cushingoid
symptoms, although rare, can persist
for several months after steroid injections have been terminated (28,104).
Injectate composition and volume
depend on numerous factors and vary
widely between practitioners (Table).
Choice of corticosteroid should take
into account the risk of intravascular
or intrathecal injection and, therefore, particle size and the addition of
preservatives (benzyl alchohol) or vehicles (polyethylene glycol) (105,106).
Corticosteroid particles may aggregate
and form larger particles when mixed
with local anesthetics and contrast
agents containing certain preservatives
Commonly used anesthetics include
lidocaine, bupivacaine, and ropivacaine. Formulations with preservatives
(methylparaben) and vasoconstrictors
(epinephrine) should be avoided. Methylparaben is classified as an antimicrobial preservative, and it is added for its
bacteriostatic activity. Choice of anesthetic should take into account patient
health, pain severity, and postdischarge
activities. Use anesthetics with caution
in elderly or unsteady patients and in
individuals who are planning to drive or
take public transportation immediately
after they are discharged. Patients with
baseline weakness or paresthesia are
more susceptible to anesthetic effects
and may develop profound postprocedural weakness, even if only a small volume of anesthetic is administered.
Procedural Tips and Techniques
In the majority of spine procedures, patients are placed in the prone position.
This position can exaggerate lumbar
lordosis, aggravate nerve root entrapment, and provoke facet-related pain.
Patient comfort is more important than
perfect prone positioning, as the goal
is to limit progressive discomfort and
involuntary movement. Placement of
a pillow under the pelvis can help to
reduce lordosis and can relieve symptoms. Patients who cannot lie in the
prone position may be able to tolerate
Radiology: Volume 281: Number 3—December 2016
HOW I DO IT: Spinal Injections for Pain Management
Drug Doses in Common Therapeutic Spinal Injections
Injection Type
Lumbar ESI
MGH protocol*
Published protocol†
Corticosteroid dose
Anesthetic dose
Saline volume
Thoracolumbar transforaminal nerve root injection
MGH protocol at or above conus
MGH protocol below conus‡
Published protocols
Corticosteroid dose
Anesthetic dose
Cervical transforaminal nerve root injection
MGH protocol
Published protocols
Corticosteroid dose
Anesthetic dose
Lumbar or cervical facet injection
MGH protocol
Published protocols
Corticosteroid dose
Anesthetic dose
BTM 15 mg (2.5 mL) followed by saline (2–4 mL) mixed with lidocaine 1% 0–10 mg (0–1 mL)
MPA 40–120 mg (1–3 mL), TCA 60–120 mg (1.5–3 mL), BTM 9–18 mg (1.5–3 mL)
Bupivacaine 0.25%–0.5% 15–40 mg (3–8 mL), lidocaine 0.5%–1.0% 15–40 mg (3–8 mL)
Saline 0–8 mL
DSP 8–12 mg (2–3 mL)
BTM 6–15 mg (1–2.5 mL) mixed with saline 1–2.5 mL & lidocaine 1% 0–10 mg (0–1 mL)
MPA 20–80 mg (0.5–2.0 mL), TCA 20–40 mg (0.5–1.0 mL), BTM 6–9 mg (1.0–1.5 mL), DSP 4–8 mg (1–2 mL)
Lidocaine 0.5%–1.0% 10–20 mg (1–4 mL), bupivacaine 0.25%–0.5% 5–20 mg (1–8 mL)
DSP 8–12 mg (2–3 mL)
DSP 4–12 mg (1–3 mL), BTM 6 mg (1 mL), TCA 40 mg (1 mL), MPA 40 mg (1 mL)
Bupivacaine 0.25%–0.5% 2.5–5 mg (1 mL), lidocaine 0.5%–2.0% 5–20 mg (1 mL)
TCA 40 mg (1 mL) mixed with ropivacaine 0.5% 5 mg (1 mL) or lidocaine 1% 10 mg (1 mL)
TCA 20–60 mg (0.5–1.5 mL), BTM 3–6 mg (0.5–1.0 mL), MPA 20–60 mg (0.5–1.5 mL)
Lidocaine 1%–2% 5–20 mg (0.5–1.0 mL)
Note.—Medication and dose selections require physician discretion. BTM = betamethasone acetate, 3 mg/mL and betamethasone sodium phosphate, 3 mg/mL; DSP = dexamethasone sodium
phosphate, 4 mg/mL; MPA = methylprednisolone acetate, 40 mg/mL; TCA = triamcinalone acetonide, 40 mg/mL.
* Massachusetts General Hospital (MGH) protocols are routinely modified based on recommendations by specialty societies and consensus groups.
Published protocols may not reflect current recommendations by specialty societies and consensus groups.
Corticosteroid dose is proportionate to epidural flow.
imaging in the oblique or lateral decubitus position.
Fluoroscopic set-up can neutralize
the challenges posed by lordosis, scoliosis, spondylolisthesis, and oblique
patient positioning. By standardizing
needle trajectory, even deformed spondylotic spines can be depicted in conventional anteroposterior, lateral, and
oblique views at the level of injection.
Set-up usually involves four systematic
maneuvers. First, one must identify the
level of intervention. Second, one must
rotate the detector left-right to obtain
a straight anteroposterior projection of
the spine. Third, one must adjust the
craniocaudal tilt to normalize endplate
relationships. The final maneuver involves rotating the detector left-right to
obtain a bull’s-eye projection for needle
navigation. Fluoroscopy units that enable one to use saved positions allow
rapid transition between different views.
Radiology: Volume 281: Number 3—December 2016
One should archive fluoroscopic
images to document the procedure,
needle position, and contrast material
distribution for billing and medicolegal
purposes. Referring surgeons may review the images with patients and determine whether the steroid reached its
intended target. In patients who have
undergone repeated injections, the images provide templates for reproducing
safe and effective needle placement.
One should archive a minimum of two
images. The first image, obtained before steroid delivery, shows extravascular contrast material. The second,
obtained after steroid delivery, shows
contrast material washout and proves
that the steroid flowed into the same
location as the contrast material.
Lumbosacral transforaminal injection.—The rationale for transforaminal NRB is precise drug delivery to the
inflamed nerve root (Figs 5, 9). The
epiradicular space, which is the target
in needle placement, surrounds the
ventral ramus. Because the epiradicular and epidural spaces are continuous,
injectate flows selectively along the spinal nerve and nerve root into the spinal
canal (Figs 5, 6). Transforaminal injection delivers the corticosteroid directly
to the pain generator in the foramen
or ventral epidural space. Thus, NRB
can yield a superior therapeutic effect
with a smaller corticosteroid dose than
that used with interlaminar ESI (35,62–
64,107). In ESI, the corticosteroid takes
the path of least resistance, spreading
indiscriminately from the dorsal epidural space throughout the spinal canal.
When the foramen is patent, intraforaminal needle placement can be supraneural (subpediculate) or infraneural
(retrodiskal) (Figs 10, 11). Select the
supraneural location, the so-called safe
triangle, for reliable epiradicular flow of
HOW I DO IT: Spinal Injections for Pain Management
Figure 9
Figure 9: Fluoroscopic set-up for sacral (S1) NRB in a 53-year-old man with left leg pain correlating with
L5-S1 disk extrusion and left S1 mechanical impingement. (a) Anteroposterior fluoroscopic image shows the
detector was tilted craniocaudally to align the inferior margin of posterior S1 foramen (thin curved line) with
the superior margin of anterior S1 neural arch (arrowheads). Sacral orientation determines the degree of
craniocaudal tilt. The detector was rotated laterally to align the medial margin (thick curved line) of S1 pedicle
(∗) with lateral margin of posterior S1 neural foramen along expected course of S1 nerve root. Curved needle
(arrow) improves foraminal navigation. Until it enters the foramen, the needle must target the inferolateral
border of the posterior S1 foramen. (b) Subsequent anteroposterior fluoroscopic image shows the needle
hub (white arrow) and needle tip (white arrowhead) are oriented cranially along the expected course of the
S1 nerve root. Initially, contrast material flowed retrograde into the posterior S1 foramen (black arrow). After
advancing the needle, contrast material (black arrowheads) spread favorably along S1 pedicle (∗) and S1
nerve root to the L5-S1 disk level.
the steroid along the nerve root to the
next higher disk level (64) (Fig 5). The
safe triangle is bounded by the pedicle
superiorly, the exiting nerve medially,
and the vertebral body anteriorly (64)
(Fig 10). Veins, and sometimes the radicular artery, course through the safe
triangle, explaining the frequency of
vascular cannulation and the “unsafe
triangle” moniker (108). Curved needles may have advantages over straight
needles for evading vessels and navigating obstructions (eg, hypertrophic facet
If veins compromise supraneural injection, reposition the needle inferiorly
and posteriorly in the foramen. This infraneural approach targets the Kambin
triangle and favors dorsal and caudal
epidural flow (109). The Kambin triangle is bounded by the exiting nerve superiorly, the caudal vertebral body inferiorly, and the facet joint posteriorly.
Infraneural placement is more likely to
result in annulus fibrosus perforation
and inadvertent discography (Fig 12).
In patients with foraminal stenosis or
lateral disk herniation, target the ventral ramus peripheral to the foramen to
avoid severe pain production during injection and failed delivery of medication
(Figs 4, 10).
NRB at S1 requires epidural needle
placement and poses unique access
challenges. Both transforaminal and
transosseous techniques are feasible after excluding Tarloff cysts and dural ectasia during MR image review. The dorsal S1 foramen is constant in location
and orientation but variable in caliber.
When the foramen is narrow, transforaminal navigation can be difficult or
impossible without meticulous fluoroscopic set-up (Fig 9). A curved needle
(5°–10° along the distal centimeter)
helps passage through a small angled
foramen. Do not rotate a curved needle
in the foramen because of the risk of
lacerating vessels, including the lateral
sacral artery. In patients with osteopenia, a 22-gauge straight needle can be
used to penetrate sacral plates with a
twisting or oscillating motion. Appropriate epidural depth is determined
with lateral fluoroscopy. Trajectory cannot be altered once the needle is drilled
through bone. The same transosseous
technique can be used to advance a
straight needle through a paraspinal fusion mass for lumbar NRB.
During most NRBs, expect injection
to produce transient radicular symptoms. To avoid the overproduction of
severe long-lasting pain, ask patients
to control the injection rate. Explain
that symptoms should not exceed 5–6
on a 0–10 pain scale. Patients indicate
when to inject and when to pause. Patients are reassured by this degree of
control; however, stoic individuals may
request continued injection despite
severe pain because they fear partial
steroid dosing. Watch their faces for
signs of discomfort, and observe their
body language. If the injection rate is
too slow, steroid particles can settle
in the needle and clog it. When injection pressure unexpectedly increases,
reinsert the stylet to clear the needle
before a steroid plug completely blocks
it. Periodically agitate the syringe to
resuspend crystals.
NRB generates diagnostic information from pain provocation during needle placement, pain provocation during
injection, immediate pain relief from
the anesthetic, or delayed pain relief
from the corticosteroid. In dictated reports, record the provocative response
(pain production during injection) as
concordant or nonconcordant and the
immediate analgesic response (pain reduction after injection). Selective NRB
is intended to yield only diagnostic information. An anesthetic, not a steroid,
is injected. In selective NRB, the needle
tip touches the ventral ramus peripheral
to the foramen and provokes radicular
pain that is assessed for concordance
with typical symptoms. The volume of
anesthetic is limited to avoid spread to
nontarget nerves.
Radiology: Volume 281: Number 3—December 2016
HOW I DO IT: Spinal Injections for Pain Management
Figure 10
Figure 11
Figure 10: Transforaminal lumbosacral needle placements. Schematic drawing of the lumbosacral spine
shows coronal relationships of nerve roots, nerve root ganglia, and postganglionic spinal nerves. In stenotic
foramina, extraforaminal needle placement (N1) targets ventral ramus peripherally. In patent foramina, needle
placement can be supraneural (N2) in the safe triangle (∗) or infraneural (N3) in the Kambin triangle (cross).
At S1, the needle (N4) crosses the posterior S1 foramen and enters the epidural space inferior to the S1
Cervical transforaminal injection.—
Cervical transforaminal injection is indicated in radiculopathy with or without
axial neck pain. Injectionists may follow
procedural protocols established by specialty societies, such as the Spine Intervention Society (or SIS) (100–116). The
2004 Spine Intervention Society practice guidelines for cervical NRB recommended intraforaminal positioning of
the needle tip as deep as the midpoint
of articular pillars but never deeper than
a vertical line connecting the uncinate
processes (117). After reports of catastrophic neurologic injuries from cervical
NRBs, some investigators recommended
protocol modifications (55,75,92,118–
120). Potentially safer techniques include extraforaminal needle placement,
a lateral or posterior approach, digital
Radiology: Volume 281: Number 3—December 2016
subtraction fluoroscopy, CT guidance,
and nonparticulate corticosteroid administration. Others have questioned
the benefit of cervical transforaminal
injection with any technique, given the
difficulty associated with visualization
of small vessels, including the radicular
artery (84,121,122).
To perform fluoroscopy-guided
cervical NRB with an anterolateral approach, place the patient in the prone
position and turn his or her head away
from the side of injection to shift the carotid artery from the needle path. Trajectory modification may be necessary
when MR or CT images show an unusually posterior carotid artery or tortuous vertebral artery (123). When MR
images are unavailable for procedural
planning, reschedule the injection or
Figure 11: Oblique fluoroscopic image shows
the set-up for lumbar NRB. During anterposterior
fluoroscopy (images not shown), the detector was
tilted craniocaudally to align the L5 pedicle with
the caudal margin of the transverse process (thin
curved line), to maximize the space between the
L5 transverse process and the sacrum and to
standardize osseous relationships for reproducible
needle placement. The x-ray beam is parallel to the
L5 superior endplate (arrows). The detector was
rotated laterally to open supraneural (S) and infraneural (I) routes between the L5 transverse process,
lateral facet border (thick curved line), and iliac
wing (arrowheads). Degree of rotation depends on
morphology of facet and iliac wing, desired needle
placement relative to foramen, and straight versus
curved needle technique. Straight needle technique
requires direct trajectory and, therefore, greater
detector rotation. A curved needle may improve
navigation through narrow spaces and around
hypertrophic facets.
position the needle more posteriorly
and peripherally than usual, especially
in older individuals who might have tortuous arteries. Skip skin anesthesia in
case the external jugular vein underlies
the desired needle entry site.
During the fluoroscopic set-up, target the foramen posteriorly to increase
distance from the vertebral artery and
inferiorly to access the epiradicular
space of the exiting nerve and to improve the likelihood of intraforaminal
spread of injectate (Fig 6). Whereas
lumbar nerves exit the foramen superiorly, cervical nerves exit it inferiorly.
When the needle is positioned too superiorly and peripherally, injectate may
flow along the more cranial nontarget
HOW I DO IT: Spinal Injections for Pain Management
Figure 12
Figure 14
Figure 12: Inadvertant diskogram during NRB in a 51-year-old man with left L3 radiculopathy correlating
with L3–4 intraforaminal disk extrusion. (a) Axial T1-weighted MR image at the L3–4 disk level shows a
large left intraforaminal disk extrusion (arrowheads) displacing left L3 nerve (white arrow). Right L3 nerve
(black arrow) location is normal and surrounded by fat. (b) Anteroposterior fluoroscopic image in the prone
position. Curved needles are present on the left side at L3–4 and L4–5. At L3–4, infraneural (retrodiscal)
needle (black arrowhead) punctured the disk annulus, resulting in intradiscal contrast (white arrowheads).
Radicular symptoms were immediately exacerbated due to distension of the herniation sac (arrow). L4–5 =
L4–5 disk space.
Figure 13
Figure 13: Inadvertent C7 NRB during attempted C8 NRB in a 44-year-old man with right C8
radiculopathy correlating with C7-T1 intraforaminal
disk extrusion. Anteroposterior fluoroscopic image
in the supine position shows the needle (arrow)
targets right C8 nerve at C7-T1 foramen. Pain
provocation prevented further needle advancement.
Needle trajectory was satisfactory, but the needle tip
terminated peripheral to lateral masses (black lines),
distant from the C8 nerve. Injected contrast material
(arrowheads) flowed along nontarget C7 nerve into
C6–7 foramen between C6 and C7 pedicles. Black
 = pedicles from C6-T2.
nerve (Fig 13). Needle length depends
on neck girth and target level, and it
ranges from 1.5 to 2.5 inches. Remove
any stylet and flush the 25-gauge needle
with contrast material, filling the hub
prior to insertion to obviate gas delivery. Direct the needle to the lateral
margin of the articular pillars, switching between oblique and posteroanterior fluoroscopy to check the needle
trajectory and depth.
Document extravascular needle
placement during contrast material
injection with real-time anteroposterior fluoroscopy. Digital subtraction
angiography may improve vessel detection (115). Exit veins by advancing the
needle several millimeters. If needle advancement fails to result in vein exit, reposition the needle more caudally along
the expected course of the target nerve.
Short extension tubing (dead space, 0.4
mL) helps to avoid hand exposure during fluoroscopy and inadvertent needle
motion during syringe exchange. Inject a nonparticulate corticosteroid.
In the cervical spine, nonparticulate
and particulate corticosteroids have
Figure 14: Targeting midline posterior epidural fat in
interlaminar ESI. Midline sagittal reformatted CT image
of the lumbar spine and posterior epidural fat at L2–3
(white ∗) indicates safe zone for needle placement
in ESI. As a general rule, dorsal epidural fat is most
prominent between the bases of spinous processes
(white line between black ∗ at L4 and L5) at the disk
space level (intersection of white and black lines at
L4–5). Needle (N) at L3–4 shows desired tip location in
dorsal epidural fat. Needle trajectory projects cranial to
disk level (black line at L3–4). In normal spines, L5-S1
has the least dorsal epidural fat.
shown comparable short-term effects
(116,124). Immediately after needle
removal, decrease hydrostatic pressure
and the likelihood of hematoma by having patients sit upright.
Lumbar interlaminar epidural steroid injection.—Standardized fluoroscopic set-up helps to decrease needle
manipulation, radiation dose, and overall procedure time (Figs 14, 15). In
younger patients, copious epidural fat
and wide interlaminar spaces facilitate
successful needle placement. Insert
the needle from the side with more severe symptoms, since injectate tends
to spread more to the side of needle
placement. In older patients, degenerative curvature, spondylotic deformity,
interlaminar collapse, bony proliferation, and surgical changes create access
challenges. In patients with rotatory
Radiology: Volume 281: Number 3—December 2016
HOW I DO IT: Spinal Injections for Pain Management
Figure 15
Figure 15: Fluoroscopic set-up for L4–5 interlaminar ESI. (a) After tilting the detector crainocaudally during anteroposterior fluoroscopy (not shown) and projecting
L4–5 interlaminar arch (thick curved line) above L4 inferior endplate (arrowheads), laterally rotate the detector 18°–22° to align the apex of the interlaminar arch
between the bases of spinous processes (∗). Interlaminar arch at target level should align with arches above and below (curved thin lines at L3-4 and L5-S1). Degree
of detector rotation depends on scoliosis and rotatory curvature of spine. Align needle (arrow) between bases of spinous processes for midline needle placement in
dorsal epidural fat. (b) Lateral fluoroscopic image shows the needle tip (arrow) enters dorsal epidural space at level of L4–5 disk (straight black line). Needle projects
between L4 and L5 spinous processes (curved black lines). Ventral epidural contrast enhancement (arrowheads) is seen. (c) Anteroposterior fluoroscopic image
shows midline placement of needle (arrow) between L4 and L5 spinous processes (∗). Left paramedian approach was chosen because of asymmetric disk degeneration causing levoconvex curvature and right-sided interlaminar collapse.
scoliosis, approach from the side of the
convex curvature to shorten the needle
throw (Fig 15). Should the needle tip
catch on a lamina or spinous process,
turn the bevel toward bone and twist or
rock the needle gently until it slides off
and advances. Steer away from asymmetrically thickened ligamentum flavum
and facet synovial cysts. At the level of
hemilaminotomy or hemilaminectomy,
interlaminar access should be contralateral to the surgical bed to avoid peridural adhesions that increase risk of
dural puncture.
A critical juncture approaches as the
needle passes through the ligamentum
flavum. Initially, when force is applied
to the syringe plunger, high pressure
prevents contrast material flow. Sudden
loss of resistance usually means that the
needle has reached the epidural space.
Before making the final decision to
inject the corticosteroid, carefully observe the contrast material distribution
to exclude intravascular, intrathecal,
retrodural, or intraligamentous spread.
Radiology: Volume 281: Number 3—December 2016
Assume intravascular injection until
proven otherwise (Fig 8). In patients
undergoing lumbar interlaminar ESI,
the lateral view can show both vascular
and intrathecal flow; however, the anterposterior view best excludes vessels
when lateral image quality is degraded
due to body habitus. To evade vessels,
advance the needle, redirect it, or reinsert it at a different level.
Intrathecal injection shows immediate dependent layering of contrast material in the subarachnoid space. After
dural puncture, ESI can be attempted
at a different level or terminated and
rescheduled to avoid any possibility of
complication due to intrathecal steroid
and anesthetic administration. The
retrodural space (retrodural space of
Okada) can be recognized because it
usually communicates with the interspinous space (125,126). The intraligamentous space is associated with facet
degeneration and ligamentum flavum
delamination (125). In the lateral view,
contrast agent distribution initially
simulates epidurography, but injection
pressure unexpectedly increases after
administration of approximately 1 mL
of the contrast agent. If lateral and anteroposterior images enable confirmation of interspinous, interlaminar, or
facet joint opacification, advance the
needle for epidural access.
Epidurographic patterns vary considerably between patients and between
time points in the same patient (127).
Injectate takes the path of least resistance, collecting at the needle tip or
spreading over multiple levels. It may
flow cephalad or caudad, right or left,
circumferentially around the thecal sac
or transforaminally along a nerve root.
The plica mediana dorsalis, a midline
septum that anchors the dural membrane posteriorly, can divide the dorsal
epidural space and restrict injectate flow
unilaterally. Needle repositioning may
be desirable if contrast material spreads
contralateral to the side of symptoms.
Always inject under low pressure.
Spinal stenosis and postoperative
HOW I DO IT: Spinal Injections for Pain Management
peridural scarring can block free flow
of the corticosteroid. When injectate
pools locally at a stenotic level or between stenotic levels, anticipate pain
production. Symptoms are usually transient when delivering small aliquots and
dissipate after 20–30 seconds. When
larger volumes are injected quickly,
persistent leg symptoms limit delivery
of the full dose and force early termination of the procedure. At levels of
severe symptomatic spinal stenosis, ESI
may exacerbate symptoms that require
hospitalization for pain control despite
prominent posterior epidural fat.
Transforaminal ESI is an NRB variant procedure intended to be semiselective in patients who have unilateral
nonradicular symptoms and nonselective in patients who lack interlaminar
access due to multilevel laminectomy,
hardware, or bone graft. The goal of
the procedure is diffuse epidural spread
rather than nerve selectivity. Thus, foraminal patency is more important than
the exact level of injection. Stenotic foramina should be avoided because of
obstructed epidural flow. Although needle placement and initial flow patterns
can be identical in transforaminal ESI
and NRB, extra diluent disperses the
corticosteroid in transforaminal ESI.
Lumbar and cervical facet joint injection.—In patients with early osteoarthritis, facet-related pain reflects
synovitis or capsulitis and responds to
corticosteroid injection. If the steroid
breaks the inflammatory cycle, pain relief lasts longer than the drug lifespan. In
patients with advanced osteoarthritis, irreversible cartilage loss limits treatment
effectiveness. After 6–8 weeks, particulate preparations will have dissipated
and symptoms will have predictably returned. Hypertrophic facet degeneration
can be managed with periodic injections
or with medial branch radiofrequency
denervation. Attritional degeneration
poses a difficult problem due to the loss
of bone stock, causing spondylolisthesis,
stenosis, and segmental instability. Invariably, treatment effects do not last as
long, or they become nonexistent.
Direct needles at cartilage interfaces or capsular recesses (Figs 7, 16).
Fluoroscopic set-up should account for
Figure 16
Figure 16: Pars injection via L4-5 facet joint in a 21-year-old woman with low back pain correlating with
L5 spondylolysis. (a) Sagittal reformatted CT image of lumbar spine shows continuity between L4-5 facet
joint (black arrowheads) and L5 pars defect (white arrowhead). (b) Oblique fluoroscopic image in the prone
position shows contrast material filling the needle hub (black arrow) and flowing away from the needle tip
into the superior recess (white arrow) of right L4-5 facet joint. Contrast material spreads inferiorly into the
conjoined space created by L5 pars defect and inferior L4-5 facet joint recess (arrowheads). Axial CT image
(not shown) demonstrated direct access to right L4-5 facet joint at midarticular level approximately 20° off
midline. L4 = L4 pedicle, S1 = S1 pedicle.
articular orientation, curvature, and degeneration (Fig 1). When osteophytes
block the joint space or when listhesis
deforms it, target capsular recesses to
increase the likelihood of intra-articular
needle placement. Periarticular corticosteroid injection may offer the same
therapeutic benefits as intra-articular
corticosteroid administration (31,128).
Document the extra-articular leak of
contrast material into a synovial cyst,
intraligamentous cavity, or retrodural
space (125,126,129). At lumbar levels,
synovial cyst rupture is feasible by placing the needle into the facet joint with
fluoroscopic guidance or directly into
the cyst or facet joint with CT guidance
(Fig 7). Facet joints communicate with
pars defects; therefore, they can be
used to deliver a steroid directly into
the pseudoarthrosis (130) (Fig 16).
In the cervical spine, both lateral
(joint space) and posterior (capsular recess) approaches are feasible.
In posterior approaches, displace the
mandible by turning the head opposite the symptomatic side. Place pillows under the chest to flex the neck
and shorten needle distances. At lower
cervical levels especially, decrease the
throw by inserting needles perpendicular to the skin. When the needle touches bone, angle the detector parallel to
the joint space and move the needle tip
superiorly or inferiorly into the joint
Spine intervention and pain management create rewarding opportunities for
radiologists. Radiologists with appropriate training can take responsibility
for treatment decisions and outcomes,
helping patients delay or avoid surgery.
These radiologists build patient-physician relationships, counseling patients
with the goal of improving quality of
life. Radiologists can leverage their expertise in MR image interpretation to
Radiology: Volume 281: Number 3—December 2016
HOW I DO IT: Spinal Injections for Pain Management
correlate imaging findings with clinical
symptoms and establish pain generators. They can use their knowledge of
fluoroscopic anatomy to target those
pain generators and plan safe and effective needle placement.
Acknowledgment: The author thanks Susanne
Loomis, MSci, for her expertise in preparation
of the medical illustrations and Eleni Balasalle,
MEd, for her expertise in the preperation of the
supplemental videos.
Disclosures of Conflicts of Interest: W.E.P. disclosed no relevant relationships.
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Radiology: Volume 281: Number 3—December 2016