STUDY RATIONALE AND CONTEXT
Since most patients with symptomatic lumbar-herniated nucleus pulposus (HNP) will
improve with nonsurgical treatment, and because it is difficult to predict which patients
will not improve, nearly all are initially counseled to undergo nonsurgical care.
Many experienced practitioners have observed, however, that certain types of patients
with HNP are more likely than others to fail conservative management. To address this
observation, and to help counsel patients with regard to the typical treatments used
for their particular lumbar HNP, we investigated if there is radiographic or clinical
factors that can predict surgical intervention in patients with lumbar HNP.
CLINICAL QUESTION
What clinical and radiological findings can serve as predictors for surgical intervention
in patients with lumbar disc herniation?
RESULTS
From 123 citations, six underwent full-text review ([Fig 1]). Four studies met the inclusion criteria for assessing factors associated with
the likelihood of decompression surgery [1], [2], [3], [4] ([Table 1]). In the Web Appendix Table 2 provides the critical appraisal for these four studies,
and Web Appendix Table 3 describes the reasons for excluding studies.
Common prognostic factors evaluated in multiple studies ([Table 2])
More baseline disability was the only factor in more than one study that was associated
with having surgery. Three studies consistently found that more baseline disability
as determined by either the Roland Disability Index (RDI) or the Oswestry Disability
Index (ODI) was associated with a higher possibility of discectomy surgery [1], [2], [1], [2]. One study reported that there was a 70% increase in the odds of having surgery
for every 3-point difference in the RDI (the adjusted odds ratio = 1.8 [95% confidence
interval, 1.2–2.9]) [2]. Descriptions of RDI and ODI are found in [Table 3].
There were inconsistent results across three studies with respect to whether having
an extruded or sequestered disc was associated with a higher probability of having
surgery.
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Buttermann [1] reported on 50 patients who were enrolled in a conservative arm (epidural steroid
injection) of a randomized control trial. Inclusion criteria were symptoms for at
least 6 weeks and disc herniation occupying >25% of the cross-sectional area of the
spinal canal as measured on axial CT or MRI. Twenty-seven (54%) underwent surgery.
Those who had surgery were twice as likely to have an extruded or sequestered disc
compared with those who did not undergo surgery (57% vs 26%, P = .036).
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Peul et al [2] and Weinstein et al [4] found no association between herniation type (extruded, sequestered, or protruded)
and the possibility of surgery. Weinstein et al, as part of the Spine Patient Outcomes
Research
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Trial (SPORT study), evaluated factors associated with having surgery in 240 patients
who were randomized to receive conservative care. Of these, 107 (45%) underwent surgery.
Peul et al analyzed 142 patients from the conservative treatment arm of a randomized
trial on lumbar disc surgery.
Several characteristics were not associated with having surgery in multiple studies.
These include demographic characteristics (age, gender, occupation, smoking status,
and body mass index), evidence of neurological deficit (depressed reflex, weakness
in a myotomal distribution, or decreased sensation in a dermatomal distribution),
positive straight leg testing, and level of herniation.
Prognostic factors evaluated in single studies ([Table 4])
Single studies reported the following characteristics associated with receiving surgery:
hydrated disc, lower income, a positive Kemp’s sign, and higher-leg pain intensity,
higher sciatica indices of frequency and bothersomeness, a lower SF-36v2 physical
score, and symptoms that were getting worse at baseline.
Single studies found the following characteristics not associated with having surgery:
comorbid conditions, pain with cough or sneeze, a positive-crossed straight leg raise
test, education, employment status, inflammatory end plate changes on MRI, number
of levels of degeneration, the patient’s preference for surgery, or physical activity
level.
Clinical guidelines (published in the last 10 years)
The American Pain Society: In patients with persistent and disabling radiculopathy
due to herniated lumbar disc or persistent and disabling leg pain due to spinal stenosis,
it is advised that clinicians discuss surgical risks and benefits as an option (strong
recommendation, high-quality evidence). Also recommended is that shared decision-making
regarding surgery include a specific discussion about moderate average benefits, which
appear to decrease over time in patients who undergo surgery[5].
Within the limits of our inclusion and exclusion criteria, there were no clinical
guidelines that specifically address clinical or radiographic characteristics that
indicate surgery.
Fig 1
Results of literature search.
Table 1
Characteristics of included studies.*
* NR indicates not reported; MRI, magnetic resonance imaging; and CT, computed tomography.
† Only includes patients in the conservative arm of a randomized control trial, of
which some crossed over and received surgery.
Table 2
Summary of predictive variables for discectomy surgery in patients with HNP reported
in two or more studies.*
* HNP indicates herniated nucleus pulposus; BMI, body mass index; MRI magnetic resonance
imaging; + indicates that the variable was found to be predictive of surgery; – indicates
that the variable was not found to be predictive of surgery; a blank space indicates
that the variable was not considered in the study.
† Assessment of disability not described.
Table 3
Description of patient-reported outcomes measures used .
Table 4
Summary of predictive variables for discectomy surgery in patients with HNP reported
in a single study.*
* NP indicates herniated nucleus pulposus;VAS = Visual Analogue Scale; MRI, magnetic
resonance imaging; + indicates that the variable was found to be predictive of surgery;
– indicates that the variable was not found to be predictive of surgery; a blank space
indicates that the variable was not considered in the study.
DISCUSSION
Despite some relevant class I evidence, it can be difficult to guide patients who
present with lumbar radicular pain caused by nerve root compression from a herniated
disc. Weinstein et al [4] performed a prospective randomized study on surgery versus conservative treatment
for lumbar disc herniation, as part of the SPORT study. Both surgery and conservative
treatment demonstrated a high-satisfaction rate. The study was limited, however, in
that the intention-to-treat analysis was hampered by a high-cross over rate. Only
50% of the surgery patients received surgery within 3 months and 42% of the conservative
patients crossed over to surgical treatment. In the as-treated analyses there was
a “strong, statistically significant advantages for surgery at all follow-up times
through two years.”
Some evidence suggests that delaying surgery may limit the effectiveness of surgical
treatment [6]. As such, if prognostic factors were well established to help predict which patients
would ultimately require surgery, treatment may be more effective. To use the SPORT
trial as an example, if it were possible to predict which patients would be most likely
to cross over to the surgical treatment arm, it would significantly aid in directing
patients toward the most effective care. With this goal, this project was designed
to examine the available prospective cohort literature on surgical versus conservative
treatments for lumbar HNP. Specifically, patients who crossed over from the conservative
arm to the surgical arm were evaluated to see what presenting factors were shared.
Each of the four selected studies had individual factors which the authors associated
with increased odds of conservative patients requiring surgical intervention ([Table 1]). More consistent, however, were the factors that were not associated with surgical
intervention ([Table 2]). All four articles reported no correlation between only two factors: patients’
age and their occupation. Surprisingly, we were not able to demonstrate an association
between surgical treatment and neurological symptoms, such as weakness, reflexes,
or sensory disturbance. Weinstein et al [4] noted an association between positive straight leg raise and failure of conservative
treatment but Peul et al [2] and Weber [3] reported no association to this physical examination sign.
The radiographic findings were less of a value than the clinical signs. The only positive
correlation was the presence of a sequestered disc fragment, and this was noted only
by Buttermann [1]. Weinstein et al and Peul et al noted no association of disc sequestration and need
for surgical intervention ([Table 2]). Buttermann further analyzed the MRI images and noted that hydrated discs were
more likely to need surgery ([Table 4]). Last, the level of disc herniation on MRI was reported in all four studies not
to correlate with surgical intervention.
Based on the literature reviewed here, it currently appears that specific clinical
and radiographic features do not seem to be helpful when directing and counseling
patients with lumbar HNP. There appears, however, to be some factors that can help
direct treatment options. The patient’s baseline disability was the only factor in
more than one study that was a prognostic factor for determining which patients would
have lumbar decompressive surgery for acute disc herniations. Three of the four studies
specifically noted a consistent finding of a greater baseline disability, as determined
by either the RDI or ODI, was associated with an increased odds of having surgical
intervention [1], [2], [1], [2] ([Table 4]). In fact, Peul et al [2] noted a 70% increase in the odds ratio for every 3-point increase in the RDI score
(the adjusted odds ratio = 1.8 [95% confidence interval, 1.2–2.9]).
SUMMARY AND CONCLUSION
From the limited data available, it appears that individual radiographic and clinical
features are currently not able to predict the likelihood of surgical intervention.
Higher baseline disability measurements (ODI and RDI) correlated, however, with surgical
treatment. We hypothesize that this is an area of promising future research. Future
studies should aim to follow variables that may be used to predict surgical treatment,
including straight leg raise test, and classification of herniation morphology such
as far-lateral herniation.
