Interspinous Spacer versus Traditional Decompressive Surgery for Lumbar Spinal Stenosis: A Systematic Review and Meta-Analysis.
ABSTRACT Dynamic interspinous spacers, such as X-stop, Coflex, DIAM, and Aperius, are widely used for the treatment of lumbar spinal stenosis. However, controversy remains as to whether dynamic interspinous spacer use is superior to traditional decompressive surgery.
Medline, Embase, Cochrane Library, and the Cochrane Controlled Trials Register were searched during August 2013. A track search was performed on February 27, 2014. Study was included in this review if it was: (1) a randomized controlled trial (RCT) or non-randomized prospective comparison study, (2) comparing the clinical outcomes for interspinous spacer use versus traditional decompressive surgery, (3) in a minimum of 30 patients, (4) with a follow-up duration of at least 12 months.
Two RCTs and three non-randomized prospective studies were included, with 204 patients in the interspinous spacer (IS) group and 217 patients in the traditional decompressive surgery (TDS) group. Pooled analysis showed no significant difference between the IS and TDS groups for low back pain (WMD: 1.2; 95% CI: -10.12, 12.53; P = 0.03; I2 = 66%), leg pain (WMD: 7.12; 95% CI: -3.88, 18.12; P = 0.02; I2 = 70%), ODI (WMD: 6.88; 95% CI: -14.92, 28.68; P = 0.03; I2 = 79%), RDQ (WMD: -1.30, 95% CI: -3.07, 0.47; P = 0.00; I2 = 0%), or complications (RR: 1.39; 95% CI: 0.61, 3.14; P = 0.23; I2 = 28%). The TDS group had a significantly lower incidence of reoperation (RR: 3.34; 95% CI: 1.77, 6.31; P = 0.60; I2 = 0%).
Although patients may obtain some benefits from interspinous spacers implanted through a minimally invasive technique, interspinous spacer use is associated with a higher incidence of reoperation and higher cost. The indications, risks, and benefits of using an interspinous process device should be carefully considered before surgery.
- SourceAvailable from: ncbi.nlm.nih.gov[Show abstract] [Hide abstract]
ABSTRACT: To test the feasibility of creating a valid and reliable checklist with the following features: appropriate for assessing both randomised and non-randomised studies; provision of both an overall score for study quality and a profile of scores not only for the quality of reporting, internal validity (bias and confounding) and power, but also for external validity. A pilot version was first developed, based on epidemiological principles, reviews, and existing checklists for randomised studies. Face and content validity were assessed by three experienced reviewers and reliability was determined using two raters assessing 10 randomised and 10 non-randomised studies. Using different raters, the checklist was revised and tested for internal consistency (Kuder-Richardson 20), test-retest and inter-rater reliability (Spearman correlation coefficient and sign rank test; kappa statistics), criterion validity, and respondent burden. The performance of the checklist improved considerably after revision of a pilot version. The Quality Index had high internal consistency (KR-20: 0.89) as did the subscales apart from external validity (KR-20: 0.54). Test-retest (r 0.88) and inter-rater (r 0.75) reliability of the Quality Index were good. Reliability of the subscales varied from good (bias) to poor (external validity). The Quality Index correlated highly with an existing, established instrument for assessing randomised studies (r 0.90). There was little difference between its performance with non-randomised and with randomised studies. Raters took about 20 minutes to assess each paper (range 10 to 45 minutes). This study has shown that it is feasible to develop a checklist that can be used to assess the methodological quality not only of randomised controlled trials but also non-randomised studies. It has also shown that it is possible to produce a checklist that provides a profile of the paper, alerting reviewers to its particular methodological strengths and weaknesses. Further work is required to improve the checklist and the training of raters in the assessment of external validity.Journal of Epidemiology & Community Health 07/1998; 52(6):377-84. · 3.29 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Prospective observational study. To prospectively assess the clinical outcome of patients with symptomatic lumbar spinal stenosis before and at periodic intervals after X Stop implantation and to compare the data with previous studies. The X Stop Interspinous Process Distraction Device is a relatively new interspinous implant designed for patients with symptomatic spinal stenosis particularly neurogenic claudication. Previously, a randomized study has shown a 75% improvement in symptoms and physical function at 1-year post-X Stop implantation for lumbar spinal stenosis. The only other study is a preliminary report of only 10 patients with variable intervals of clinical outcome assessment. Forty consecutive patients were enrolled and surgically treated with X Stop implantation. The X Stop device was implanted at the stenotic segment, which was either at 1 or 2 levels in each patient. They were clinically evaluated at the preoperative, 3-month, 6-month, and 1-year stage with clinical questionnaires (Zurich Claudication Questionnaire, Oswestry Disability Index, and SF-36). Sixteen patients failed to complete all the questionnaires at all time intervals and hence were excluded, leaving 24 patients who had completed all questionnaire at all time interval. By 12 months, 54% of these 24 patients reported clinically significant improvement in their symptoms, 33% reported clinically significant improvement in physical function, and 71% expressed satisfaction with the procedure. 29% of the patients required caudal epidural after 12 months after surgery for recurrence of their symptoms of neurogenic claudication. The results of this prospective observational study indicate that X Stop offers significant short-term improvement over a 1-year period. It is a safe, effective, and less invasive alternative for treatment of lumbar spinal stenosis. Our results, however, are less favorable than the previous multicenter, randomized study.Spine 06/2007; 32(12):1345-8. · 2.45 Impact Factor
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ABSTRACT: A randomized, controlled, prospective multicenter trial comparing the outcomes of neurogenic intermittent claudication (NIC) patients treated with the interspinous process decompression system (X STOP) with patients treated nonoperatively. To determine the safety and efficacy of the X STOP interspinous implant. Patients suffering from NIC secondary to lumbar spinal stenosis have been limited to a choice between nonoperative therapies and decompressive surgical procedures, with or without fusion. The X STOP was developed to provide an alternative therapeutic treatment. METHODS.: 191 patients were treated, 100 in the X STOP group and 91 in the control group. The primary outcomes measure was the Zurich Claudication Questionnaire, a patient-completed, validated instrument for NIC. At every follow-up visit, X STOP patients had significantly better outcomes in each domain of the Zurich Claudication Questionnaire. At 2 years, the X STOP patients improved by 45.4% over the mean baseline Symptom Severity score compared with 7.4% in the control group; the mean improvement in the Physical Function domain was 44.3% in the X STOP group and -0.4% in the control group. In the X STOP group, 73.1% patients were satisfied with their treatment compared with 35.9% of control patients. The X STOP provides a conservative yet effective treatment for patients suffering from lumbar spinal stenosis. In the continuum of treatment options, the X STOP offers an attractive alternative to both conservative care and decompressive surgery.Spine 07/2005; 30(12):1351-8. · 2.45 Impact Factor
Interspinous Spacer versus Traditional Decompressive
Surgery for Lumbar Spinal Stenosis: A Systematic Review
Ai-Min Wu1, Yong Zhou2, Qing-Long Li1, Xin-Lei Wu3, Yong-Long Jin1, Peng Luo1, Yong-Long Chi1,
1The Department of Spinal Surgery, Second Affiliated Hospital of Wenzhou Medical University, Zhejiang Spinal Research Center, Wenzhou, Zhejiang, People’s Republic of
China, 2The First Medical College, Wenzhou Medical University, Wenzhou, Zhejiang, People’s Republic of China, 3Institute of Digitized Medicine, Wenzhou Medical
University, Wenzhou, Zhejiang, People’s Republic of China
Background: Dynamic interspinous spacers, such as X-stop, Coflex, DIAM, and Aperius, are widely used for the treatment of
lumbar spinal stenosis. However, controversy remains as to whether dynamic interspinous spacer use is superior to
traditional decompressive surgery.
Methods: Medline, Embase, Cochrane Library, and the Cochrane Controlled Trials Register were searched during August
2013. A track search was performed on February 27, 2014. Study was included in this review if it was: (1) a randomized
controlled trial (RCT) or non-randomized prospective comparison study, (2) comparing the clinical outcomes for
interspinous spacer use versus traditional decompressive surgery, (3) in a minimum of 30 patients, (4) with a follow-up
duration of at least 12 months.
Results: Two RCTs and three non-randomized prospective studies were included, with 204 patients in the interspinous
spacer (IS) group and 217 patients in the traditional decompressive surgery (TDS) group. Pooled analysis showed no
significant difference between the IS and TDS groups for low back pain (WMD: 1.2; 95% CI: 210.12, 12.53; P=0.03; I2=66%),
leg pain (WMD: 7.12; 95% CI: 23.88, 18.12; P=0.02; I2=70%), ODI (WMD: 6.88; 95% CI: 214.92, 28.68; P=0.03; I2=79%), RDQ
(WMD: 21.30, 95% CI: 23.07, 0.47; P=0.00; I2=0%), or complications (RR: 1.39; 95% CI: 0.61, 3.14; P=0.23; I2=28%). The TDS
group had a significantly lower incidence of reoperation (RR: 3.34; 95% CI: 1.77, 6.31; P=0.60; I2=0%).
Conclusion: Although patients may obtain some benefits from interspinous spacers implanted through a minimally invasive
technique, interspinous spacer use is associated with a higher incidence of reoperation and higher cost. The indications,
risks, and benefits of using an interspinous process device should be carefully considered before surgery.
Citation: Wu A-M, Zhou Y, Li Q-L, Wu X-L, Jin Y-L, et al. (2014) Interspinous Spacer versus Traditional Decompressive Surgery for Lumbar Spinal Stenosis: A
Systematic Review and Meta-Analysis. PLoS ONE 9(5): e97142. doi:10.1371/journal.pone.0097142
Editor: Michael Fehlings, University of Toronto, Canada
Received January 21, 2014; Accepted April 15, 2014; Published May 8, 2014
Copyright: ? 2014 Wu et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by the National Natural Sciences Foundation of China (81372014; 81371988) and the Natural Sciences Foundation of Zhejiang
Province for Distinguished Young Scholars (LR12H06001). The funders had no role in the study design, data collection and analysis, decision to publish, or
preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: email@example.com
Degenerative lumbar spinal stenosis is common in the elderly
population, and many affected individuals have pain and
neurogenic intermittent claudication. Decompressive surgery is
recommended for their treatment [1,2]. Flexion tends to relieve
symptoms for some patients. Therefore, dynamic devices have
been designed to limit spinal extension. These devices include
interspinous spacers, such as the X-stop, Coflex, DIAM, and
Aperius devices [3,4,5].
However, controversy remains about whether interspinous
spacers produce better or worse outcomes than traditional
decompressive surgery [6,7]. Richards et al. reported that
implanted interspinous spacers could increase the spinal canal
area, as well as the width and area of the intervertebral foramen
. Zucherman et al.  reported good functional improvement
and pain relief after the implantation of interspinous spacers.
However, Bowers et al.  noted that the procedure carried a
high rate of complications, which was separately reported by Kim
et al. .
The aim of this study was to compare the clinical outcomes of
interspinous spacer use to traditional decompressive surgery.
Electronic databases of Medline, Embase, Cochrane Library,
and the Cochrane Controlled Trials Register were searched
without restriction for publication date or language during August
2013. The following keywords were used, in combination with
PLOS ONE | www.plosone.org1May 2014 | Volume 9 | Issue 5 | e97142
Boolean operators: ‘‘lumbar spinal stenosis,’’ ‘‘neurogenic inter-
mittent claudication,’’ ‘‘interspinous spacer,’’ ‘‘X-stop,’’ ‘‘Coflex,’’
‘‘DIAM,’’ ‘‘Wallis,’’ ‘‘Aperius,’’ and ‘‘decompressive surgery’’.
Related articles and reference lists were searched to avoid
omissions. A track search was performed on February 27, 2014,
to add any new publications.
A study was included in the analysis if it was: (1) a randomized
controlled trial (RCT) or a non-randomized prospective compar-
ative study, (2) comparing the clinical outcomes of interspinous
spacer use versus traditional decompressive surgery, (3) in at least
30 patients, (4) with a follow-up period of at least 12 months. Two
authors (AMW and YZ) assessed the potentially eligible studies
independently. Any disagreement was discussed and resolved with
a third independent author (LQL).
Data were independently extracted by two investigators (XLW
and YLJ) using a standardized form (Table S1). Collected data
included the publication date, study design, sample size, follow-up
duration, interventions, complications, incidence of reoperation,
and clinical outcomes, including low back pain, leg pain, the
Oswestry disability index (ODI), and the Roland disability
Risk of bias assessment
Risk of bias was assessed with the Downs and Black checklist
. The quality levels of randomized and non-randomized
studies of healthcare interventions were assessed with 27 questions,
as shown in Table S2.
Meta-analyses were performed in the RevMan 5.2 software
(Cochrane Collaboration, Software Update, Oxford, UK), ac-
Figure 1. Flowchart of the study selection process.
Table 1. Characteristics of the four included studies.
CharacteristicStromqvist 2013 Beyer 2013Richter 2012 Kim 2007Moojen 2013
Study design RCTNon-RCTNon-RCTNon-RCT RCT
Follow-up duration24 months24 months 24 months 12 months12 months
Participants100 patients Age: 69
45 patients Age:
62 patients Age:
68 (52–79) years
62 patients Age:
50 (20–81) years
159 patients Age:
63 (45–83) years
InterventionIS=50 TDS=50 IS (X-Stop) IS=12 TDS=33 IS
IS=31 TDS=31 IS
IS=31 TDS=31 IS
IS=80 TDS=79 IS
Outcomes VAS of low back pain and
leg pain, complications
VAS of low back pain
and leg pain, ODI and
ODI, RDQ, complications
VAS of low back pain
and leg pain,
VAS of low back pain
and leg pain, RDQ,
Note: RCT: Randomized controlled trial; IS: Interspinous spacer group; TDS: Traditional decompressive surgery group; VAS: Visual analogue scale; ODI: Oswestry
disability index; RDQ: Roland disability questionnaire.
Interspinous Spacer versus Decompressive Surgery
PLOS ONE | www.plosone.org2 May 2014 | Volume 9 | Issue 5 | e97142
cording to the recommendations of the Cochrane Collaboration.
Another author independently checked the data before the
analysis was performed. Risk ratios (RRs) were calculated for
binary outcomes and weighted mean differences (WMDs) for
continuous outcomes, along with the 95% confidence intervals
(CIs). Heterogeneity was evaluated by chi-squared and I2tests.
Acceptable heterogeneity was defined by a P-value of ,0.01 for
the chi-squared test and ,30% for the I2test. A sensitivity analysis
was performed, in which the possible effects of removing one study
from the analysis were evaluated. Homogeneous data were pooled
with a fixed-effects model. Heterogeneous data were assessed by a
Studies included and risk of bias
The first search strategy identified 426 potential studies, of
which 422 reports were excluded. One RCT  and three non-
randomized prospective studies [14,15,16] were included accord-
ing to the eligibility criteria. Another RCT was included by the
track search  (Fig. 1). In total, there were 208 patients in the
interspinous spacer (IS) group and 217 patients in the traditional
decompressive surgery (TDS) group. The characteristics of all five
included studies are shown in Table 1. The risk of bias assessment
according to the Downs and Black checklist of all included studies
is shown in Table S2.
Four studies [13,14,16,17] reported visual analogue scale (VAS)
scores for low back pain and leg pain. Pooled analysis showed no
significant differences between the IS and TDS groups for low
back pain (WMD: 1.20; 95% CI: 210.12, 12.53; P=0.03;
I2=66%) or leg pain (WMD: 7.12; 95% CI: 23.88, 18.12;
P=0.02; I2=70%; Fig. 2A, B). Two studies each reported the
results of the ODI [15,16] and RDQ [15,17]. Pooled analysis
shown no significant difference between the IS and TDS groups
Figure 2. Forest plot showing the meta-analysis of visual analogue scale (VAS) scores for low back pain (A) and leg pain (B), the
Oswestry disability index (C), and the Roland disability questionnaire (D).
Interspinous Spacer versus Decompressive Surgery
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for the ODI (WMD: 6.88; 95% CI: 214.92, 28.68; P=0.03;
I2=79%) or RDQ (WMD: 21.30; 95% CI: 23.07, 0.47;
P=0.88; I2=0%; Fig. 1C, D).
All of the included studies reported the outcome of complica-
tions. There were 23/204 complications in the IS group and 18/
217 complications in the TDS group. Pooled analysis showed no
significant differences between the groups (RR: 1.39; 95% CI:
0.61, 3.14; P=0.23; I2=28%; Fig. 3). Analyses of the minimally
invasive (MI) and open surgery (OS) subgroups revealed no
significant differences between the IS and TDS groups (MI
subgroup: RR: 1.08; 95% CI: 0.47, 2.48; OS subgroup: RR: 1.76;
95% CI: 0.35, 8.84; Fig. 3).
The incidence of reoperation was reported in three studies
[13,15,17]. In the IS group, 31/161 cases required a second
operation, compared to 11/160 cases in the TDS group. The
incidence of reoperation was significantly lower in the TDS group
(RR: 3.34; 95% CI: 1.77, 6.31; P=0.60; I2=0%, Fig. 4).
Analyses of the MI and OS subgroups showed a higher incidence
of reoperation in the IS group (MI subgroup: RR: 3.46; 95% CI:
1.47, 8.11; OS subgroup: RR: 3.20; 95% CI: 1.23, 8.33; Fig. 4).
Patients with lumbar spinal stenosis can experience intermittent
neurogenic claudication, pain, and numbness in the legs.
Implantation of an interspinous spacer can increase the cross-
Figure 3. Forest plot showing the meta-analysis for the incidence of complications.
Figure 4. Forest plot showing the meta-analysis for the reoperation rate.
Interspinous Spacer versus Decompressive Surgery
PLOS ONE | www.plosone.org4 May 2014 | Volume 9 | Issue 5 | e97142
sectional area of the spinal canal . Many interspinous spacers
have been designed  for clinical use , and an increasing
number of studies have reported their use for the treatment of
degenerative lumbar spinal stenosis [4,5,21,22]. However, most of
these studies were case series or clinical experiments without
contrasting controls . Our eligibility criteria permitted only
five studies to be included in our meta-analysis. Although the
included sample size was not large, it is larger than most other
studies of dynamic device use for the management of lumbar
spinal stenosis [24,25]. All of the included studies were prospective
and comparatively designed, and two were RCTs . Therefore,
the results of our meta-analysis are credible.
The meta-analysis revealed no statistically significant differences
in the clinical outcomes for back/leg pain, ODI, and RDQ
between the two groups. Complication rates were also similar,
although the incidence of complications in the TDS group (18/
217; 8.3%) was slightly lower than that in the IS group (23/204;
11.3%). Interspinous spacer insertion has been associated with
spinous process fracture, implant dislocation, [14,15], and
heterotopic ossification [26,27], which may explain the slightly
higher rate of complications in the IS group.
The reoperation rate was significantly higher in the IS group
(37/161; 23.0%) compared to the TDS group (11/160, 6.9%).
Moojen et al.  and Beyer et al.  implanted interspinous
spacers through an MI method. Therefore, we performed a
subgroup analysis of the incidence rates of complications and
reoperations for the MI and OS subgroups. The subgroup analysis
revealed the same results as the overall analysis, indicating that the
higher reoperation rate was not related to the surgical method (MI
or OS). Many surgeons choose indirect decompressive surgery
 or simply insert the implant percutaneously [28,29]. It may be
that patients could obtain benefits from the MI technique;
however, the cost of each interspinous process device is at least
J2,000 (£1,704; $2,756), as reported by Moojen et al. . An
alternative might be the use of microsurgical technique of simple
decompression without interspinous spacer use, many of which
have been reported.
A limitation of this meta-analysis was that only five studies were
included. There is a lack of studies comparing interspinous spacer
use and traditional decompressive surgery in the published
literature. Based on the above meta-analysis of 12 to 24 months
of clinical results, we conclude that patients may obtain some
benefit from MI techniques with interspinous spacer use.
However, the high cost and high reoperation rate associated with
interspinous spacer use are worrisome. Therefore, the indications,
risks, and benefits of using an interspinous process device should
be carefully considered before surgery.
Data extraction form.
Downs and Black Checklist.
Conceived and designed the experiments: AMW XYW YLC. Performed
the experiments: AMW YZ QLL. Analyzed the data: XLW YLJ PL.
Contributed reagents/materials/analysis tools: AMW XYW YLC. Wrote
the paper: AMW XYW.
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