Diagnostic Value, Prognostic Value, and Safety of Provocation Discography

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Diagnostic Value, Prognostic Value, and Safety
of Provocation Discography
Introduction
The use of provocation discography (discography) as a
diagnostic tool is a source of debate. Literature has
both confirmed and called into question the diagnostic
value, prognostic value, and safety of this procedure.
The following commentary provides an updated,
evidence-based discussion of these topics within the
context of the modern standards for performance of dis-
cography and the interpretation of the resulting data.
Background
The intervertebral disc is a common source of chronic
low back pain in adults, with a prevalence of approxi-
mately 40% [1,2]. Patient history and physical examina-
tion provide inadequate sensitivity and specificity to
accurately diagnose discogenic pain [2,3]. Similarly, be-
cause disc degeneration and disruption are common
findings in asymptomatic individuals [4,5], advanced im-
aging cannot definitively distinguish a painful disc from a
nonpainful disc [6,7].
Provocation discography (discography) is a diagnostic
test meant to confirm or exclude the intervertebral
disc(s) as a source of back pain. This technique involves
puncture of the disc with a fine-gauge needle under
fluoroscopic guidance and pressurization of the disc via
the injection of contrast media. The pressurization pro-
cess seeks to provoke pain of a concordant nature to
the patient’s index pain. Postdiscography CT scanning
may then be performed to examine the disc for annular
fissure presence, configuration, epidural extravasation,
and communication between fissure and herniation.
Concordant pain production, in the presence of fissures
reaching the outer annulus, in a framework of strict di-
agnostic criteria, can allow the diagnosis of painful inter-
nal disc disruption [6,8].
Discography should be performed for chronic low back
pain (3 months) only if adequate attempts at conserva-
tive therapy have been unsuccessful and noninvasive di-
agnostic tests have failed to reveal the etiology of back
pain. It is used to confirm or exclude a suspected disc
as a source of pain in a patient with severe, persistent
symptoms, but is only advised if the results of the test
will influence future care. Most commonly, discography
is used to inform the decision to perform or avoid an in-
vasive therapeutic procedure such as disc thermocoa-
gulation, discectomy, or a spinal fusion. However,
discography is also useful to diagnose discogenic pain,
such that if confirmed, further diagnostic testing does
not need to be pursued (i.e., decrease unnecessary
health care costs).
Since its introduction in the early 1940s [9], the standards
for technique and interpretation of this diagnostic test
have changed in order to improve the accuracy and
safety of this procedure. While clinicians and investigators
over the years have used a variety of definitions of a “pos-
itive” vs “negative” study, as well as pressurization and
volume limits, current clinical guidelines require the follow-
ing for the unequivocal diagnosis of discogenic pain [10]:
1. Concordant pain response of 6/10
2. Volume limit of 3 mL
3. Pressurization of the disc to no greater than 50 psi
above the opening pressure
4. Adjacent disc(s) provide controls
a. For one control disc:
i. Painless response
OR
ii. Nonconcordant pain that occurs at a pressure
greater than 15 psi over opening pressure
b. For two adjacent control discs:
i. Painless response at both levels
OR
ii. One painless disc AND one disc with noncon-
cordant pain that occurs at a pressure greater
than 15 psi over opening pressure
More detailed operational criteria for lumbar discography
are described in the Spine Intervention Society (SIS)
practice guidelines [10].
Diagnostic Value
The functional nature of discography is appealing due to
the inability of advanced imaging to discern a painful
disc from a painless disc [11,12] as disc degeneration
and disruption are common findings in asymptomatic in-
dividuals [4,5]. In a cross-sectional study of
V
C2017 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com 1
Pain Medicine 2017; 0: 1–6
doi: 10.1093/pm/pnx034

asymptomatic individuals who received lumbosacral
magnetic resonance imaging (MRI), one study found that
35% of individuals age 20 to 59 years, and nearly all of
those age 60 to 80 years, had at least one level of disc
degeneration or bulging [5]. Twenty percent of individuals
younger than age 60 years had a herniated nucleus pul-
posus, whereas this finding was present in 36% of those
older than 60 years of age [5]. In a similar cross-
sectional analysis of asymptomatic individuals who re-
ceived lumbosacral MRI, with a mean age of 42 years,
61% of subjects had disc abnormalities in one lumbar
level or more [4]. A high-intensity zone (HIZ) was present
in 14% of individuals, and 60% of those age 60 years or
older had at least one lumbar disc protrusion [4].
Due to methodological variability in the technique and
interpretation of discography in the early literature, a
lack of consensus exists with regard to the false positive
rate and, thus, the diagnostic value of this procedure
[6,8,13–29]. Early techniques implemented a high-
pressure discography technique, with various definitions
of a “positive” vs a “negative” response to disc provoca-
tion with regard to pain intensity, concordance of pain,
and the use of control levels. However, systematic re-
view and meta-analysis have revealed a low false posi-
tive rate of 9.3% per patient and 6.0% per disc when
applying the later-developed SIS/IASP (International
Association for the Study of Pain) technique and criteria
for appropriate performance and interpretation of this
procedure [28].
Prognostic Value
While the diagnostic value of discography is now well
established, there has been less investigation into the
prognostic value of this procedure. One retrospective
matched cohort study found no difference in the suc-
cess rate of lumbar spinal fusion surgery when compar-
ing patients who were selected using discography with
clinical assessment and imaging alone [30]. Notably,
these investigators used a high-pressure discography
technique and did not use pain scores to interpret the
results of disc provocation. Because this technique is
not in accordance with the standards discussed above,
application of these study findings is limited. Based on
these data, inferences regarding the accuracy of dis-
cography findings and their resultant prognostic value
cannot be made. Alternatively, a prospective cohort
study of individuals with an MRI suggestive of disco-
genic pain showed an 89% success rate following lum-
bar spinal fusion when the level treated was directed by
a positive response to discography, as opposed to a
52% success rate with a negative response to discogra-
phy [31]. However, description of the discography tech-
nique and interpretation is inadequate to determine
what standard was applied, again limiting interpretation
of these results. One prospective study demonstrated
that, if performed according to SIS/IASP guidelines, the
use of discography is associated with a threefold greater
rate of clinically significant improvement in pain and
function following spine surgery compared with clinical
assessment and imaging alone [32].
The negative predictive value of discography has not
been directly studied due to ethical issues of operating
on a disc that had a negative response to discography.
However, the presence of a negative response to dis-
cography or indeterminate results due to the inability to
identify a negative control disc, on principle, represents
an important finding that guides the patient away from a
poorly indicated discectomy and fusion surgery.
Safety
Acute/Subacute
Acute and subacute adverse events associated with
discography are rare, and very few have been reported
in the past four decades. These include bacterial disci-
tis, meningitis, spinal headache/cerebral spinal fluid
leakage, retroperitoneal bleeding, intrathecal hemor-
rhage, arachnoiditis, allergic reaction, acute disc hernia-
tion, epidural abscess, pulmonary embolism from
nucleus pulposus material, and seizure [33–39]. A sys-
tematic review estimated an incidence of discitis of less
than 0.25% per patient and less than 0.14% per disc
exposed to discography [40].
Since the implementation of routine fluoroscopic guid-
ance during spinal interventions, as well as improved
discography technique and safety measures during the
modern use of this technique, the only adverse events
reported in the past 15 years include discitis [41,42],
acute disc herniation [43,44], development of an acute
Schmorl’s node [45], and intravascular injection [46].
Discitis following cervical discography has not been re-
ported in over 15 years [47]. Five cases of acute lumbar
disc herniations were reported, with maximal pressures
reaching 40 and 44 psi in two patients, 93 psi in one pa-
tient, and unreported pressures in two patients during
discography [43]. One patient experienced self-limited
foot drop, and three patients required spine surgery due
to persistently exacerbated radicular pain and/or thecal
sac compression. A case of Cauda Equina Syndrome
requiring spinal decompression was reported following
discography [44]. No procedure details were reported,
so the maximal disc pressure reached is unknown.
Similarly, in a case of acute Schmorl’s node formation
associated with discography, procedure details, includ-
ing disc pressure, were not reported [45].
Chronic
Concern has been raised in the scientific community re-
garding possible long-term complications of discogra-
phy. This apprehension stems from two publications
assessing a single cohort of patients. In 2009, prospec-
tive longitudinal cohort data (mean follow-up of 8.7
years) were published that sought to investigate the
long-term impact of discography on intervertebral discs
by comparing MRI indices of disc degeneration and
McCormick et al.
2

disruption in individuals who had undergone discogra-
phy with matched controls [25]. Subsequently, in 2016,
clinical and health care utilization outcomes were re-
ported from the same matched cohort at 10-year fol-
low-up [26]. From these two studies, the research
group concluded that at long-term follow-up discogra-
phy results in a higher rate of lumbar disc degeneration,
lumbar disc herniation, spine surgery, repeat advanced
imaging, significant low back pain episodes, work lost,
and medical visits. However, review of the study meth-
odology reveals alternative conclusions.
These studies excluded individuals who were appropri-
ate discography candidates: individuals 1) with low back
pain significant enough to have presented to a physician
for treatment, 2) taking pain medications for low back
symptoms, or 3) with activity restrictions due to low
back pain. Thus, generalizability of this study with re-
spect to a realistic discography population is limited.
Further, questions arise regarding the appropriateness
of the control cohort as the prevalence rates of Modic
changes in this group were far lower (11%) than re-
ported rates in the general population (36%) [4]. This
discrepancy increases the likelihood of observing inap-
propriate intergroup differences. In addition, loss to
follow-up was substantial. While loss to follow-up is
nearly unavoidable in long-term clinical studies, the rates
in this matched cohort reach a magnitude that impairs
the ability to comment on true patient outcomes. The
loss to follow-up was reported as 30% in the 2009 data
set and 24% in the 2016 data set.
With regard to procedure technique, inappropriately
high disc pressures were produced in a majority of sub-
jects. The investigators used a threshold of 100 psi, ex-
ceeding the SIS/IASP-recommended limit. In 96% of
subjects, at least one disc was subjected to a pressure
of 80 psi or greater. This is notable as high disc pres-
sure has been demonstrated to cause annular disrup-
tion in animal models [48]. Thus, excessive disc
pressurization technique may have damaged the disc
structure due to artificially high disc pressure that is in-
consistent with the established standards.
With regard to the presented data, 95% confidence in-
tervals overlap, indicating a lack of statistical significance
for several of the comparisons made (see Table 1).
Because no subgroup stratification was performed, it is
unknown if new disc herniations or Modic changes
were overrepresented in individuals who had prior disc
pressurization of 100 psi. In addition, it is unknown what
other health care resources or imaging were utilized by
the individual patient pools consisting of 1) subjects hav-
ing documented cervical disc disease, 2) subjects hav-
ing previous lumbar disc herniation with complete
resolution of symptoms, and 3) subjects with no history
of previous cervical or lumbar disc illness but who did
have history of serious psychological distress consistent
with somatization disorder. Notably, secondary analysis
of these data reported in the 2009 study showed that
subjects with normal psychometric test results did not
report significant long-term back pain at a higher rate in
the discography cohort than in the control cohort [17].
Lastly, if the majority of patients who proceeded to sur-
gery or utilized further medical care had discography
performed in discs with prior herniations, this carries dif-
ferent implications than if discography was performed
on structurally “normal” discs.
Other cohort studies have not demonstrated a higher
rate of disc degeneration associated with discography.
In a small prospective study (N ¼36), Pfirrmann scores
in subjects with symptomatic low back pain who had
undergone provocation discography with or without
confirmation by intradiscal bupivacaine injection
(“discoblock”) were compared with matched controls at
long-term follow-up [49]. No significant difference in disc
degeneration was observed on MRI between groups at
three- to five-year follow-up. Notably, pressure manom-
etry and control disc levels were not used and statistical
power was limited. A cross-sectional cohort study found
no evidence of degenerative disc changes 10 to 20
years after discography in individuals who had originally
presented for care due to low back pain [50]. Only radi-
ography was performed (not MRI), so this study was not
sensitive to anything but the most drastic disc changes.
The discography technique was not described.
Published animal data on disc degeneration following
disc puncture also appear equivocal. While annular disc
puncture has been used in animal models of disc de-
generation [51–53], evidence suggests that annular
Table 1 Comparison of imaging and health care utilization outcomes at remote follow-up after lumbar
discography with overlapping 95% confidence intervals of proportions
Imaging and health care utilization outcomes [25,26] Discography Control
Grade III/IV Pfirrmann changes 8% (4–13%) 3% (0–5%)
Grade V Pfirrmann changes 18% (12–24%) 9% (4–13%)
New high-intensity zone 6% (3–10%) 3% (0–5%)
Spine surgery 19% (9–30%) 6% (0–12%)
New advanced imaging 37% (24–49%) 21% (10–32%)
Discography Diagnostic and Prognostic Value
3

puncture with a small gauge needle does not cause
disc degeneration [54,55]. The possibility of a small
gauge needle not causing disc degeneration is striking
in an animal model given that even a 27 gauge needle
represents 52% of a rat’s disc height [56], far greater
relative to disc height in a human disc. Elliot et al. [56]
reviewed 23 in vivo disc puncture studies in rat, rabbit,
dog, and sheep models and found that significant disc
changes were not produced when the needle gauge
represented less than 40% of the disc height. Yet, it
must be noted that disc changes were assessed at
short-term interval follow-up.
Conclusions
When adhering to published SIS/IASP standards for ap-
propriate provocation discography technique and data
interpretation, this diagnostic procedure is associated
with a low false positive rate. There is some evidence
that including positive response to discography, defined
by these standards, correlates with improved surgical
outcomes when compared with selection by clinical and
imaging assessment alone. The negative predictive
value of discography has not been directly studied, but
the presence of a negative response to discography, or
indeterminate results due to the lack of ability to identify
a negative control disc, guides the patient away from a
poorly indicated discectomy and fusion surgery. There is
no convincing evidence that provocation discography,
performed in accordance with SIS/IASP standards, re-
sults in an increased incidence of clinically relevant fu-
ture disc degeneration or disruption. However, failure to
adhere to these standards is associated with an unac-
ceptably high false positive rate [28]. Observation from
one cohort of patients suggests a possible increase in
the long-term risk of disc degeneration, disc disruption,
and inferior clinical outcomes compared with those who
do not undergo this procedure [25,26]; however, there
is concern that these findings may relate to overpressur-
ization of the disc during discography, and overlapping
confidence intervals and study methodology limit the
practical utility of these study findings. Notably, these
findings have not been reproduced in other studies
[49,50]. Additional investigation of possible long-term
risks of discography in a realistic population, with well-
matched controls and the use of appropriate procedure
technique, is needed. The decision to perform discogra-
phy and accept the possible long-term consequences
must be viewed in the context of the potential for an in-
appropriate discectomy and fusion procedure.
Key Point
Discography, performed in accordance with current
standards in appropriately selected patients, is a safe
and useful diagnostic tool to inform treatment decisions.
Acknowledgments
The authors wish to thank Drs. Yakov Vorobeychik and
Milan Stojanovic, Standards Division Chair and Vice
Chair, respectively, for providing direction and guidance
throughout the development of the manuscript. Thanks
also to Drs. Andrew Engel, Milton Landers, and David
C. Miller, Standards Division members, for providing im-
portant comments on the draft. Finally, we wish to rec-
ognize the contributions of Mrs. Belinda Duszynski,
Senior Director of Policy and Practice at the Spine
Intervention Society, for coordinating the development
of the manuscript and preparing it for publication.
Disclosure: None of the authors has any financial con-
flicts of interest to disclose.
ZACHARY L. MCCORMICK, MD,* FRED DEFRANCESCH, MD,
†
VIVEK LOOMBA, MD,
‡
MAXIM MORADIAN, MD,
§
RAMESH
BATHINA, MD,
¶
AND GEORGE RAPPARD,MD
k
;onbehalfof
the Standards Division of the Spine Intervention Society
*Department of Orthopaedic Surgery, University of
California, San Francisco, California;
†
Interventional
Spine Specialists, Kenner, Louisiana;
‡
Henry Ford
Health System, Detroit, Michigan;
§
Risser Orthopaedic
Group, Pasadena, California;
¶
Aurora Pain Clinic,
Aurora, Illinois;
k
Los Angeles Minimally Invasive Spine
Institute, Los Angeles, California, USA
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