Interspinous process device versus conventional decompression for lumbar spinal stenosis: 5-year results of a randomized controlled trial

Catharina D. Schenck Department of Neurosurgery and
Department of Neurosurgery, Haaglanden Medical Center, The Hague, The Netherlands;

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Sietse E. S. Terpstra Department of Neurosurgery and

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Wouter A. Moojen Department of Neurosurgery and
Department of Neurosurgery, Haaglanden Medical Center, The Hague, The Netherlands;
Department of Neurosurgery, HAGA Teaching Hospital, The Hague, The Netherlands; and

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Erik van Zwet Department of Biostatistics, Leiden University Medical Center, Leiden, The Netherlands;

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Wilco Peul Department of Neurosurgery and
Department of Neurosurgery, Haaglanden Medical Center, The Hague, The Netherlands;

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Mark P. Arts Department of Neurosurgery, Haaglanden Medical Center, The Hague, The Netherlands;

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Carmen L. A. Vleggeert-Lankamp Department of Neurosurgery and
Department of Neurosurgery, Haaglanden Medical Center, The Hague, The Netherlands;
Department of Neurosurgery, HAGA Teaching Hospital, The Hague, The Netherlands; and
Department of Neurosurgery, Spaarne Hospital, Hoofddorp/Haarlem, The Netherlands

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OBJECTIVE

Interspinous process distraction devices (IPDs) can be implanted to treat patients with intermittent neurogenic claudication (INC) due to lumbar spinal stenosis. Short-term results provided evidence that the outcomes of IPD implantation were comparable to those of decompressive surgery, although the reoperation rate was higher in patients who received an IPD. This study focuses on the long-term results.

METHODS

Patients with INC and spinal stenosis at 1 or 2 levels randomly underwent either decompression or IPD implantation. Patients were blinded to the allocated treatment. The primary outcome was the Zurich Claudication Questionnaire (ZCQ) score at 5-year follow-up. Repeated measurement analysis was applied to compare outcomes over time.

RESULTS

In total, 159 patients were included and randomly underwent treatment: 80 patients were randomly assigned to undergo IPD implantation, and 79 underwent spinal bony decompression. At 5 years, the success rates in terms of ZCQ score were similar (68% of patients who underwent IPD implantation had a successful recovery vs 56% of those who underwent bony decompression, p = 0.422). The reoperation rate at 2 years after surgery was substantial in the IPD group (29%), but no reoperations were performed thereafter. Long-term visual analog scale score for back pain was lower in the IPD group than the bony decompression group (p = 0.02).

CONCLUSIONS

IPD implantation is a more expensive alternative to decompressive surgery for INC but has comparable functional outcome during follow-up. The risk of reoperation due to absence of recovery is substantial in the first 2 years after IPD implantation, but if surgery is successful this positive effect remains throughout long-term follow-up. The IPD group had less back pain during long-term follow-up, but the clinical relevance of this finding is debatable.

ABBREVIATIONS

Felix = Foraminal Enlargement Lumbar Interspinous distraXion; INC = intermittent neurogenic claudication; IPD = interspinous process distraction device; LSS = lumbar spinal stenosis; LTFU = lost to follow-up; OR = odds ratio; RMDQ = modified Roland-Morris Disability Questionnaire; VAS = visual analog scale; ZCQ = Zurich Claudication Questionnaire.

OBJECTIVE

Interspinous process distraction devices (IPDs) can be implanted to treat patients with intermittent neurogenic claudication (INC) due to lumbar spinal stenosis. Short-term results provided evidence that the outcomes of IPD implantation were comparable to those of decompressive surgery, although the reoperation rate was higher in patients who received an IPD. This study focuses on the long-term results.

METHODS

Patients with INC and spinal stenosis at 1 or 2 levels randomly underwent either decompression or IPD implantation. Patients were blinded to the allocated treatment. The primary outcome was the Zurich Claudication Questionnaire (ZCQ) score at 5-year follow-up. Repeated measurement analysis was applied to compare outcomes over time.

RESULTS

In total, 159 patients were included and randomly underwent treatment: 80 patients were randomly assigned to undergo IPD implantation, and 79 underwent spinal bony decompression. At 5 years, the success rates in terms of ZCQ score were similar (68% of patients who underwent IPD implantation had a successful recovery vs 56% of those who underwent bony decompression, p = 0.422). The reoperation rate at 2 years after surgery was substantial in the IPD group (29%), but no reoperations were performed thereafter. Long-term visual analog scale score for back pain was lower in the IPD group than the bony decompression group (p = 0.02).

CONCLUSIONS

IPD implantation is a more expensive alternative to decompressive surgery for INC but has comparable functional outcome during follow-up. The risk of reoperation due to absence of recovery is substantial in the first 2 years after IPD implantation, but if surgery is successful this positive effect remains throughout long-term follow-up. The IPD group had less back pain during long-term follow-up, but the clinical relevance of this finding is debatable.

In Brief

The long-term results of the Felix trial, which compared the use of stand-alone interspinous process distraction devices (IPDs) to standard bony decompression for the treatment of neurogenic claudication due to lumbar spinal stenosis, showed that leg pain and other functional outcome scores did not significantly differ between groups over time and reoperation rates remained higher in the IPD group. Standard bony decompression should remain the gold standard treatment of lumbar spinal stenosis.

Lumbar spinal stenosis (LSS) may cause patients to suffer from neurogenic claudication,1 in which compression of the roots of the cauda equina triggers leg pain that is aggravated by prolonged walking, standing, or lumbar extension. Symptoms are sometimes accompanied by back pain.2,3 Surgical treatment may be offered if conservative treatment fails. Lumbar decompressive surgery without instrumentation is the standard treatment.4,5 Patient satisfaction after surgery is relatively low,4–6 and one of the reasons may be the destructive nature of bony decompression.7,8 Interspinous process distraction devices (IPDs) were developed as a less destructive alternative to standard bony decompression. The IPD simultaneously increases the interspinous distance via indirect decompression of the dural sac and nerve roots owing to flexion of the involved segments and widens entry to the spinal root canal.9–18 This device can be implanted in patients with symptomatic LSS instead of performing conventional bony decompression.9,10 The less invasive nature of IPD surgery could lead to decreased postoperative pain, shorter hospital stay, faster recovery, and less back pain at follow-up compared with bony decompression.19

We previously published the 1- and 2-year results of a double-blind randomized trial that compared treatment with stand-alone IPD (without bony decompression) to standard bony decompression in patients with INC due to LSS.20,21 At 8 weeks, 1 year, and 2 years, the success rates according to the Zurich Claudication Questionnaire (ZCQ) were not significantly different between the IPD group and standard bony decompression group. However, the reoperation rates of the IPD group were substantially higher than those of the decompression group after 1 year (29% vs 8%) and 2 years (33% vs 8%). Back pain was comparable between treatment groups at 1 and 2 years after surgery.20,21 Other outcome parameters for pain and functioning did not show significant differences between groups.

The 5-year follow-up data are now available, and a similar analysis was conducted to compare the long-term results of IPD implantation with those of conventional decompressive surgery.

Methods

Study Population

The enrolled patients had participated in the multicenter randomized controlled trial, Foraminal Enlargement Lumbar Interspinous distraXion (Felix). This prospective double-blind trial enrolled patients with neurogenic claudication due to LSS. Stand-alone treatment with insertion of an IPD without bony decompression was compared to standard bony decompression. The study protocol was approved by the medical ethics committees of the five participating hospitals. Specifically, we obtained approval to randomly assign treatment after induction of anesthesia. The design and study protocol were published previously (Dutch Trial Register no.: NTR1307).21 The trial was performed using a randomized design with variable block sizes.

All patients met the inclusion and exclusion criteria of the Felix trial (Table 1).21 Written informed consent was obtained from all patients. All patients were diagnosed with INC on the basis of lumbar spinal canal stenosis at 1 or 2 levels with MRI confirmation and underwent at least 3 months of failed conservative treatment. The patient was excluded if preoperative MRI also showed a herniated disc that required discectomy or other deformities such as spondylolisthesis grade > 1 at the affected level (Table 1).

TABLE 1.

Inclusion and exclusion criteria

Criteria
Inclusion
 Signed informed consent
 Age 40–85 yrs
 Diagnosis of INC, as noted by leg/buttock/groin pain w/ or w/o back pain
 ≥3 mos conservative treatment
 Regular indication for surgical intervention for INC
 Narrowed lumbar spinal canal, nerve root canal, or intervertebral foramen at 1 or 2 levels, confirmed w/ MRI
 Physically & mentally willing & able to comply w/ postop evaluations (or has a caregiver willing to comply)
Exclusion
 Cauda equina syndrome
 Herniated disc at the same level, necessitating lumbar discectomy
 Paget’s disease, severe osteoporosis, or metastasis to vertebrae
 Significant scoliosis (Cobb angle >25°)
 Previous surgery at the same lumbar level
 Degenerative spondylolisthesis > grade 1 (scale 1–4) at affected level
 Significant instability of lumbar spine
 Severe comorbid conditions
 Fused segment at indicated level

Allocations were stored in prepared, opaque, coded, sealed envelopes that were opened only after induction of anesthesia. The patients, clinical nurses, and research nurses remained blinded to the allocated treatment for 1 year of follow-up. The preoperative MR images of the lumbar spine of each patient were analyzed in a previous study of the Felix trial, which showed that the included patients presented with varying degrees of stenosis according to the Schizas scale, including the most severe degree.22

Interventions

Patients in the IPD group underwent operations under general anesthesia in the knee-elbow position. Under fluoroscopic control, the IPD was implanted with a posterior midline approach and no bony decompression was performed. Patients in the standard bony decompression group underwent surgery in the same position with a similar incision length as that used for the IPD group in order to ensure that all caregivers were blind to the allocated treatment. At the stenotic level(s), limited reduction of the adjacent laminae was executed, followed by flavectomy with bilateral opening of the lateral recess. Medial facetectomy was performed if necessary. No patients underwent laminectomy, discectomy, or a combination of these procedures. Patients in both groups received the same standard postoperative care. Patients, and the research nurses who were observing these patients, were asked after every visit if they were still blind to the allocated treatment.20

Outcomes

The primary outcome measure was a disorder-specific functional score provided by the ZCQ.23,24 The primary outcome score was assessed at baseline, immediately postoperatively (2 weeks), and at 4, 8, 12, 26, 52, 104, and 260 weeks postoperatively. The ZCQ has three domains (symptom severity, physical function, and patient satisfaction). Domain scores were calculated as the average number of points obtained on the subsets of questions, with high scores of 5 (symptom severity) or 4 (physical function and patient satisfaction). The score increases with increasing disability. Average subscale scores were determined at every follow-up evaluation by the blinded research nurses. In terms of the overall ZCQ score, the patient was considered to have had a successful recovery if at least two domain subscales of the ZCQ were considered successful.25 Success was defined as a decrease of at least 0.5 points on the symptom severity scale and the physical function scale.20,23,24 A score of less than 2.5 on the patient satisfaction subscale was also defined as successful.23,24

Secondary outcome measures were scores on the modified Roland-Morris Disability Questionnaire (RMDQ) for sciatica (score range 0 to 23, with higher scores indicating worse functional status),26–34 100-mm visual analog scale (VAS) for back and leg pain (with 0 representing no pain and 100 representing the worst pain ever experienced),35 McGill Pain Questionnaire (with 0 representing the minimum pain score and 78 representing the maximum),36,37 and 7-point Likert self-rating scale of global perceived recovery (based on whether the patient experienced recovery compared with baseline status; 1–2 points were considered recovery and 3–7 points were considered no recovery).38

Sample Size

A sample size of 80 patients per treatment group would be required to provide a statistical power of 0.80 and a 2-sided alpha of 0.05.23–25 A difference of 20% between success rates was considered clinically significant on the basis of the assumption that this level of superiority would be convincing enough to change surgical guidelines and to warrant reimbursement for the costs of the IPD implant.

Statistical Analysis

An intention-to-treat analysis was used to compare treatment groups. Repeated measurement analysis was used to compare groups at all follow-up evaluations (2, 4, 8, 12, 26, 52, 104, and 260 weeks postoperatively), and generalized estimating equations were used to account for correlations between repeated measurements of the same individual. Odds ratios (ORs) were reported for binary outcome variables and mean differences for continuous outcome variables.

To analyze and interpret possible heterogeneity between treatment centers, the study was stratified at randomization. The ProMISe data management system was used for data collection and quality control. SPSS version 20.0 (IBM Corp.) was used for all statistical analysis. The Department of Medical Statistics and Bioinformatics of Leiden University Medical Center assisted and advised in the steps of the statistical analysis.

Results

Between October 2008 and September 2011, a total of 205 patients with INC due to spinal stenosis were referred to the participating hospitals and screened for inclusion by the neurosurgeon. In total, 162 patients were enrolled in the trial and gave informed consent (Fig. 1). However, 1 patient died waiting for the operation, and 2 patients appeared to have severe spondylolysis at the L5–S1 level at the final preoperative checkup. Both patients were excluded. Therefore, 159 patients received the allocated treatment. At baseline, there were no significant differences in characteristics between treatment groups (Table 2).

FIG. 1.
FIG. 1.

Enrollment and follow-up.

TABLE 2.

Baseline characteristics

CharacteristicIPD Group (n = 80)Decompression Group (n = 79)
Age, median (range), yrs66 (45–83)64 (47–83)
Male sex, no. (%)49 (61)37 (47)
Duration of INC, median (range), mos12 (2–120)22 (1–204)
BMI, median (range), kg/m227 (20–48)28 (20–37)
Duration of back pain, range, yrs1–31–3
IPD was preferred treatment, no.4946
Mild paresis or sensory loss, no.6771
Level of stenosis, no.
 L2–323
 L3–42522
 L4–55354
2-level op, no. (%)21 (26)16 (20)
ZCQ score, mean ± SD
 Symptom severity subscale (range 0–5)3.1 ± 0.53.2 ± 0.5
 Physical function subscale (range 0–4)2.6 ± 0.52.6 ± 0.5
23-item RMDQ score13.0 ± 5.214.4 ± 4.5
VAS, mean (95% CI)
 Leg pain52 (47–59)58 (52–64)
 Back pain50 (43–56)52 (46–58)

Five-Year Results

Primary Outcome Measure

Five years after randomization, 25 patients in the IPD group and 24 in the bony decompression group were lost to follow-up (LTFU), which brought both groups to a size of 55 patients. The proportions of patients with successful recovery according to ZCQ score were similar between treatment groups: mean (95% CI) 68% (56%–78%) of patients in the IPD group versus 56% (95% CI 44%–68%) in the bony decompression group (p = 0.422). During the 5-year follow-up period, the ZCQ success rates were similar between treatment arms (Table 3; Fig. 2). The ZCQ scores of the IPD group showed an upward trend, increasing from 63% of patients with successful recovery at 8 weeks to 68% at 260 weeks (p = 0.55). The ZCQ scores of the bony decompression group showed a downward trend, decreasing from 72% of patients with successful recovery at 8 weeks to 56% at 260 weeks (p = 0.07).

TABLE 3.

Primary and secondary outcomes

Variable8 wks52 wks104 wks260 wks
IPDBDOR (p value)IPDBDOR (p value)IPDBDOR (p value)IPDBDOR (p value)
Primary outcome
 ZCQ
  No. of patients73780.73 (0.44)73780.90 (0.77)70750.65 (0.20)55550.717 (0.422)
  % successful63 (51–73)72 (60–81)67 (54–74)68 (57–78)69 (57–79)60 (48–71)68 (56–78)56 (44–68)
Secondary outcome
 RMDQ score7.5 (6.1–9.0)6.5 (5.3–7.8)1.06.9 (5.4–8.5)8.1 (6.6–9.7)1.27.5 (5.6–9.5)8.1 (6.6–9.6)0.6 (0.65)*7.0 (5.5–8.5)8.6 (6.8–10.3)
 VAS score
  Back pain2.4 (19–30)23 (17–28)123 (17–29)31 (24–37)836 (24–48)28 (23–34)8 (0.26)*26 (20–32)38 (30–46)12 (0.02)
  Leg pain26 (20–32)22 (18–27)423 (17–30)26 (20–33)321 (15–27)26 (20–32)5 (0.22)*24 (17–30)32 (24–40)8 (0.12)
 Likert scale, % successful51 (40–63)53 (41–64)0.94 (0.85)56 (45–67)49 (38–60)1.37 (0.37)54 (45–69)46 (32–55)1.21 (0.52)65 (51–77)63 (50–75)0.847 (0.718)
 McGill Pain Questionnaire score11 (9–12)10 (8–12)11 (9–13)10 (9–12)9110.3710 (8–12)11 (9–12)0.48

BD = bony decompression.

Values are shown as mean (95% CI) unless indicated otherwise.

Overall scores with continuous outcome scales (RMDQ and VAS) were not significantly different.

FIG. 2.
FIG. 2.

Proportions of patients with successful recovery over time according to ZCQ score. The whiskers indicate 95% CIs. BD = bony decompression.

To evaluate whether this trend was biased by the absence of data from patients who were LTFU, the 2-year follow-up ZCQ scores were compared between the LTFU and non-LTFU patients. There were no significant differences in the 2-year ZCQ scores between those who were LTFU and those who remained in the follow-up cohort after 5 years in either treatment group. Fifty-four percent of patients who were LTFU in the IPD group had a 2-year ZCQ score indicative of successful recovery compared with 69% of patients who remained in the follow-up cohort after 5 years (p = 0.14). Among the patients in the bony decompression treatment group, 58% had ZCQ scores indicative of successful recovery at 2 years compared with 64% at 5 years (p = 0.71).

Secondary Outcome Measures

Neither the bony decompression group nor the IPD group showed statistically significant changes in RMDQ values between 104 and 260 weeks (p = 0.65 for both groups), with respective averages of 8.6 and 7.0 points at 260 weeks. The VAS score for back pain was lower in the IPD group than the bony decompression group at 260 weeks (mean 26 vs 38 mm, p = 0.02). Similar to ZCQ values, the VAS score for back pain showed a downward trend in the IPD group and an upward trend in the bony decompression group (Fig. 3).

FIG. 3.
FIG. 3.

Mean VAS scores for back pain (in millimeters) over time. The whiskers indicate 95% CIs.

The mean VAS score for leg pain at 260 weeks was 24 mm in the IPD group and 32 mm in the bony decompression group, and the VAS score for leg pain did not show any significant differences between treatment groups during the 5-year follow-up (p = 0.12) (Table 3; Fig. 4). The McGill Pain Questionnaire scores showed no significant differences between groups at 260 weeks or over time (p = 0.48; Table 3).

FIG. 4.
FIG. 4.

Mean VAS scores for leg pain (in millimeters) over time. The whiskers indicate the 95% CIs.

The dichotomized Likert scores for perceived recovery at 5 years were comparable between groups: namely, 65% of patients in the IPD group reported successful recovery versus 63% of the bony decompression group (OR 0.847, p = 0.718). This was a positive trend in comparison with the 2-year follow-up Likert scores, which showed that 54% of patients in the IPD group (p = 0.22) and 46% of those in the bony decompression group (p = 0.06) had a successful recovery (Fig. 5).

FIG. 5.
FIG. 5.

Proportions of patients with successful recovery over time according to Likert scores. The whiskers indicate the 95% CIs.

Complications and Reoperations

Direct postoperative complications were minor and described in the 1-year follow-up study.25 Reoperations were indicated and performed on 23 patients (29%) in the IPD group versus 10 patients (13%) in the bony decompression group (p = 0.04). This means that 4 additional patients in the bony decompression group underwent a reoperation since the 2-year analysis,26 while no additional patients in the IPD group underwent a reoperation. All 23 patients in the IPD group who needed a reoperation had the implant removed and underwent standard surgery with bony decompression at the same level. Of the patients in the bony decompression group who needed a reoperation, 4 underwent a reoperation on the previously operated level. Two of these 4 patients underwent a fusion procedure. The remaining patients in the bony decompression group who needed a reoperation underwent operations on directly adjacent levels.

The ZCQ scores showed that 41% (21%–64%) of the reoperated patients in the IPD group had a successful recovery at 5 years, compared with 68% of the total IPD group. ZCQ scores showed that 60% (22%–94%) of the reoperated patients in the bony decompression group had successful recovery at 5 years, compared with 56% of the total bony decompression group.

Discussion

Functionality, as represented by successful recovery according to the ZCQ score, did not show any differences at any evaluation throughout the 5-year follow-up period in this comparison of IPD without bony decompression to conventional bony decompression in patients with symptomatic LSS. In the 1- and 2-year follow-up studies of this trial, it was stressed that the high reoperation rate of the IPD group disqualified this treatment as a suitable alternative to standard decompression. Remarkably, no extra patients in the IPD group underwent operations between 2 and 5 years of follow-up, in contrast to 4 extra operations in the bony decompression group. Reoperations for recurrence of symptoms after conventional decompression may be attributed to secondary collapse of the operated segments due to progressive depression of the intervertebral disc and/or progressive degeneration of the facet joints. Therefore, the results presented here tend to legitimize the rationale for IPD implantation, which tries to achieve indirect decompression and stabilization of the lumbar spine after decompression.

Because stand-alone IPD implantation is a less destructive surgical intervention than bony decompression, it was hypothesized that its use would lead to less postoperative pain, shorter hospital stay, faster recovery, and less low-back pain during the postoperative phase. The 1-year follow-up results could not confirm this hypothesis.20 The long-term results demonstrated less back pain in the IPD group. This may be the result of the stabilizing effect of the IPD on the target level in the lumbar spine. However, the relevance of this low-back pain score is debatable. The minimal clinically important difference in VAS score for pain is generally between 10 and 20 mm or a decrease of more than 30%.39 In our study, the baseline VAS score for back pain was 50, which leads to a minimal clinically important difference of 15 between groups. A difference in back pain of 12 mm was demonstrated here. Moreover, a VAS score of 40 mm is usually considered the threshold for clinical relevance.5,40 Thus, the low-back pain score of the IPD group can be considered clinically irrelevant.

Our study showed improvements in Likert scores between 2 and 5 years after surgery in both treatment groups. Subjective satisfaction scores generally decrease as study populations age. Positive trends could be due to a higher rate of LTFU in patients who were not satisfied. However, in both groups of this study, patients who were LTFU did not have significantly different 2-year ZCQ scores compared with patients who remained in the follow-up cohort. A favorable outcome in 63%–65% of patients, as reported at 5-year follow-up, is in line with the satisfaction scores for LSS surgery reported by other studies.4–6

In agreement with our results, Nunley et al. reported ZCQ scores and a reoperation rate of 25% at 5 years after interspinous spacer implantation.41 Moreover, they also demonstrated that many revisions (20%) took place during the first 2 years after device implantation. They included patients with symptomatic "moderate" LSS, which was not further defined, whereas we included patients with all degrees of narrowing (according to the Schizas scale). In a previously published study of the Felix trial, we reported no correlation between grade of stenosis and clinical outcome.22,42

Likewise, Strömqvist et al. showed comparable 2-year ZCQ outcomes, as well as similar secondary outcomes, between patients who underwent IPD and those who underwent bony decompression for symptomatic LSS.43 They also reported significantly more reoperations in the IPD group than the bony decompression group after 2 years, which is in concordance with our 2-year results. Unfortunately, they did not publish their 5-year results, so a comparison with our 5-year results is lacking.

The blinded randomized controlled design and the long follow-up period are the major strengths of this study because the majority of studies on this subject present a follow-up period of only 2 years.43–45 The clinical features and baseline pain scores of the patients included in this study are comparable to those of other large trials.4,5 The elderly population and the long follow-up period pose extra challenges for patient tracing because these patients are more likely to die or move away to retirement or nursing homes over the years. Although the LTFU rate of 30% is relatively high, we considered these losses reasonable given the patient population. Another weakness is that the power of the study was based on ZCQ scores, which prevents us from drawing strong conclusions about other outcome parameters.

There is a subpopulation of LSS patients who thrive well with an IPD, but the number of patients in this study was too small to perform a subgroup analysis in order to identify in which patients IPD is successful. Nonetheless, it is unlikely that the size of the favorable effect would outweigh the higher costs of the implant.

Conclusions

The present study shows that bony decompression should remain the gold standard treatment of neurogenic claudication because the reoperation rate during the first years after surgery was higher in the IPD group and IPD costs are substantial. Despite these drawbacks, once beneficial, IPD implantation remains successful over long-term follow-up.

Disclosures

Dr. Arts is a consultant for NuVasive and Intrinsic Therapeutics; receives royalties from DePuy Synthes; and received clinical or research support for the described study from Zimmer Biomet and Paradigm Spine. Dr. Vleggeert-Lankamp receives non–study-related clinical or research support from Covidien, Ynske Meyes Fund, SAG, CSRS Europe, and EANS; serves on the boards of CSRS Europe and the Netherlands Neurosurgical Society; serves on the advisory board of the Rijndam Rehabilitation Centre; is a faculty member of EANS, CSRS, and EUROSPINE; produces webinars for AO Spine; and is lecturer for Women in Spine for NuVasive. Paradigm Spine funded this investigator-initiated trial.

Author Contributions

Conception and design: Moojen. Analysis and interpretation of data: Schenck, Terpstra, Vleggeert-Lankamp. Drafting the article: Schenck, Terpstra, Vleggeert-Lankamp. Critically revising the article: Schenck, Moojen, Peul, Vleggeert-Lankamp. Reviewed submitted version of manuscript: Arts. Approved the final version of the manuscript on behalf of all authors: Schenck. Statistical analysis: Terpstra, van Zwet. Study supervision: Moojen, Peul.

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    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Sénégas J. Mechanical supplementation by non-rigid fixation in degenerative intervertebral lumbar segments: the Wallis system. Eur Spine J. 2002;11(suppl 2):S164S169.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Chiu JC. Interspinous process decompression (IPD) system (X-STOP) for the treatment of lumbar spinal stenosis. Surg Technol Int. 2006;15:265275.

  • 15

    Moojen WA, Arts MP, Bartels RH, Jacobs WC, Peul WC. Effectiveness of interspinous implant surgery in patients with intermittent neurogenic claudication: a systematic review and meta-analysis. Eur Spine J. 2011;20(10):15961606.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Zucherman JF, Hsu KY, Hartjen CA, Mehalic TF, Implicito DA, Martin MJ, et al. A prospective randomized multi-center study for the treatment of lumbar spinal stenosis with the X STOP interspinous implant: 1-year results. Eur Spine J. 2004;13(1):2231.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 17

    Zucherman JF, Hsu KY, Hartjen CA, Mehalic TF, Implicito DA, Martin MJ, et al. A multicenter, prospective, randomized trial evaluating the X STOP interspinous process decompression system for the treatment of neurogenic intermittent claudication: two-year follow-up results. Spine (Phila Pa 1976).2005;30(12):13511358.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Anderson PA, Tribus CB, Kitchel SH. Treatment of neurogenic claudication by interspinous decompression: application of the X STOP device in patients with lumbar degenerative spondylolisthesis. J Neurosurg Spine. 2006;4(6):463471.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Eichholz KM, Fessler RG. Is the X STOP interspinous implant a safe and effective treatment for neurogenic intermittent claudication? Nat Clin Pract Neurol. 2006;2(1):2223.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Moojen WA, Arts MP, Jacobs WC, van Zwet EW, van den Akker-van Marle ME, Koes BW, et al. Interspinous process device versus standard conventional surgical decompression for lumbar spinal stenosis: randomized controlled trial. BMJ. 2013;347:f6415.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 21

    Moojen WA, Arts MP, Jacobs WCH, van Zwet EW, van den Akker-van Marle ME, Koes BW, et al. IPD without bony decompression versus conventional surgical decompression for lumbar spinal stenosis: 2-year results of a double-blind randomized controlled trial. Eur Spine J. 2015;24(10):22952305.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22

    Moojen WA, Schenck CD, Lycklama À Nijeholt GJ, Jacobs WCH, Van der Kallen BF, Arts MP, et al. Preoperative MRI in patients with intermittent neurogenic claudication: relevance for diagnosis and prognosis. Spine (Phila Pa 1976).2018;43(5):348355.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    Stucki G, Liang MH, Fossel AH, Katz JN. Relative responsiveness of condition-specific and generic health status measures in degenerative lumbar spinal stenosis. J Clin Epidemiol. 1995;48(11):13691378.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Stucki G, Daltroy L, Liang MH, Lipson SJ, Fossel AH, Katz JN. Measurement properties of a self-administered outcome measure in lumbar spinal stenosis. Spine (Phila Pa 1976).1996;21(7):796803.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 25

    Tuli SK, Yerby SA, Katz JN. Methodological approaches to developing criteria for improvement in lumbar spinal stenosis surgery. Spine (Phila Pa 1976).2006;31(11):12761280.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 26

    Deyo RA, Diehl AK. Patient satisfaction with medical care for low-back pain. Spine (Phila Pa 1976).1986;11(1):2830.

  • 27

    Deyo RA, Patrick DL. The significance of treatment effects: the clinical perspective. Med Care. 1995;33(4 suppl):AS286AS291.

  • 28

    Hutchinson PJ, Laing RJ, Waran V, Hutchinson E, Hollingworth W. Assessing outcome in lumbar disc surgery using patient completed measures. Br J Neurosurg. 2000;14(3):195199.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 29

    Koes BW, van Tulder MW, Thomas S. Diagnosis and treatment of low back pain. BMJ. 2006;332(7555):14301434.

  • 30

    Patrick DL, Deyo RA. Generic and disease-specific measures in assessing health status and quality of life. Med Care. 1989;27(3 suppl):S217S232.

  • 31

    Patrick DL, Deyo RA, Atlas SJ, Singer DE, Chapin A, Keller RB. Assessing health-related quality of life in patients with sciatica. Spine (Phila Pa 1976).1995;20(17):18991909.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 32

    Roland M, Morris R. A study of the natural history of low-back pain. Part II: Development of guidelines for trials of treatment in primary care. Spine (Phila Pa 1976).1983;8(2):145150.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 33

    Roland M, Morris R. A study of the natural history of back pain. Part I: Development of a reliable and sensitive measure of disability in low-back pain. Spine (Phila Pa 1976).1983;8(2):141144.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 34

    Schoppink LE, van Tulder MW, Koes BW, Beurskens SA, de Bie RA. Reliability and validity of the Dutch adaptation of the Quebec Back Pain Disability Scale. Phys Ther. 1996;76(3):268275.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 35

    Carlsson AM. Assessment of chronic pain. I. Aspects of the reliability and validity of the visual analogue scale. Pain. 1983;16(1):87101.

  • 36

    Melzack R. The McGill Pain Questionnaire: major properties and scoring methods. Pain. 1975;1(3):277299.

  • 37

    Melzack R. The McGill Pain Questionnaire: from description to measurement. Anesthesiology. 2005;103(1):199202.

  • 38

    Sullivan GM, Artino AR Jr. Analyzing and interpreting data from Likert-type scales. J Grad Med Educ. 2013;5(4):541542.

  • 39

    Ostelo RWJG, de Vet HCW. Clinically important outcomes in low back pain. Best Pract Res Clin Rheumatol. 2005;19(4):593607.

  • 40

    van Geest S, Kuijper B, Oterdoom M, van den Hout W, Brand R, Stijnen T, et al. CASINO: surgical or nonsurgical treatment for cervical radiculopathy, a randomised controlled trial. BMC Musculoskelet Disord. 2014;15:129.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 41

    Nunley PD, Patel VV, Orndorff DG, Lavelle WF, Block JE, Geisler FH. Five-year durability of stand-alone interspinous process decompression for lumbar spinal stenosis. Clin Interv Aging. 2017;12:14091417.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 42

    Weber C, Giannadakis C, Rao V, Jakola AS, Nerland U, Nygaard ØP, et al. Is there an association between radiological severity of lumbar spinal stenosis and disability, pain, or surgical outcome?: A multicenter observational study. Spine (Phila Pa 1976).2016;41(2):E78E83.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 43

    Strömqvist BH, Berg S, Gerdhem P, Johnsson R, Möller A, Sahlstrand T, et al. X-Stop versus decompressive surgery for lumbar neurogenic intermittent claudication. Spine (Phila Pa 1976).2013;38(17):14361442.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 44

    Lønne G, Johnsen LG, Rossvoll I, Andresen H, Storheim K, Zwart JA, Nygaard ØP. Minimally invasive decompression versus x-stop in lumbar spinal stenosis: a randomized controlled multicenter study. Spine (Phila Pa 1976).2015;40(2):7785.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 45

    Richter A, Halm HF, Hauck M, Quante M. Two-year follow-up after decompressive surgery with and without implantation of an interspinous device for lumbar spinal stenosis: a prospective controlled study. J Spinal Disord Tech. 2014;27(6):336341.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • Collapse
  • Expand

Schematic image of the spine (L1–pelvis) instrumented with transforaminal (upper left), anterior (center left), and lateral (lower left) lumbar interbody fixation devices as a standalone cage (upper right) and with supplemental posterior fixation (lower right) at the L4–5 level. © Margaret Sten, published with permission. See the article by Kiapour et al. (pp 928–936).

  • FIG. 1.

    Enrollment and follow-up.

  • FIG. 2.

    Proportions of patients with successful recovery over time according to ZCQ score. The whiskers indicate 95% CIs. BD = bony decompression.

  • FIG. 3.

    Mean VAS scores for back pain (in millimeters) over time. The whiskers indicate 95% CIs.

  • FIG. 4.

    Mean VAS scores for leg pain (in millimeters) over time. The whiskers indicate the 95% CIs.

  • FIG. 5.

    Proportions of patients with successful recovery over time according to Likert scores. The whiskers indicate the 95% CIs.

  • 1

    Ishimoto Y, Yoshimura N, Muraki S, Yamada H, Nagata K, Hashizume H, et al. Prevalence of symptomatic lumbar spinal stenosis and its association with physical performance in a population-based cohort in Japan: the Wakayama Spine Study. Osteoarthritis Cartilage. 2012;20(10):11031108.

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    Malmivaara A, Slätis P, Heliövaara M, Sainio P, Kinnunen H, Kankare J, et al. Surgical or nonoperative treatment for lumbar spinal stenosis? A randomized controlled trial. Spine (Phila Pa 1976).2007;32(1):18.

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    Weinstein JN, Tosteson TD, Lurie JD, Tosteson AN, Blood E, Hanscom B, et al. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N Engl J Med. 2008;358(8):794810.

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    Airaksinen O, Herno A, Kaukanen E, Saari T, Sihvonen T, Suomalainen O. Density of lumbar muscles 4 years after decompressive spinal surgery. Eur Spine J. 1996;5(3):193197.

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    Thomé C, Zevgaridis D, Leheta O, Bäzner H, Pöckler-Schöniger C, Wöhrle J, Schmiedek P. Outcome after less-invasive decompression of lumbar spinal stenosis: a randomized comparison of unilateral laminotomy, bilateral laminotomy, and laminectomy. J Neurosurg Spine. 2005;3(2):129141.

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    Davis RJ, Errico TJ, Bae H, Auerbach JD. Decompression and Coflex interlaminar stabilization compared with decompression and instrumented spinal fusion for spinal stenosis and low-grade degenerative spondylolisthesis: two-year results from the prospective, randomized, multicenter,. Food and Drug Administration Investigational Device Exemption trial. Spine (Phila Pa 1976).2013;38(18):15291539.

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    Fox MW, Onofrio BM, Onofrio BM, Hanssen AD. Clinical outcomes and radiological instability following decompressive lumbar laminectomy for degenerative spinal stenosis: a comparison of patients undergoing concomitant arthrodesis versus decompression alone. J Neurosurg. 1996;85(5):793802.

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    Fox MW, Onofrio BM. Indications for fusion following decompression for lumbar spinal stenosis. Neurosurg Focus. 1997;3(2):e2.

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    Senegas J. [Surgery of the intervertebral ligaments, alternative to arthrodesis in the treatment of degenerative instabilities]. Acta Orthop Belg. 1991;57(suppl 1):221226.

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  • 13

    Sénégas J. Mechanical supplementation by non-rigid fixation in degenerative intervertebral lumbar segments: the Wallis system. Eur Spine J. 2002;11(suppl 2):S164S169.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Chiu JC. Interspinous process decompression (IPD) system (X-STOP) for the treatment of lumbar spinal stenosis. Surg Technol Int. 2006;15:265275.

  • 15

    Moojen WA, Arts MP, Bartels RH, Jacobs WC, Peul WC. Effectiveness of interspinous implant surgery in patients with intermittent neurogenic claudication: a systematic review and meta-analysis. Eur Spine J. 2011;20(10):15961606.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Zucherman JF, Hsu KY, Hartjen CA, Mehalic TF, Implicito DA, Martin MJ, et al. A prospective randomized multi-center study for the treatment of lumbar spinal stenosis with the X STOP interspinous implant: 1-year results. Eur Spine J. 2004;13(1):2231.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 17

    Zucherman JF, Hsu KY, Hartjen CA, Mehalic TF, Implicito DA, Martin MJ, et al. A multicenter, prospective, randomized trial evaluating the X STOP interspinous process decompression system for the treatment of neurogenic intermittent claudication: two-year follow-up results. Spine (Phila Pa 1976).2005;30(12):13511358.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Anderson PA, Tribus CB, Kitchel SH. Treatment of neurogenic claudication by interspinous decompression: application of the X STOP device in patients with lumbar degenerative spondylolisthesis. J Neurosurg Spine. 2006;4(6):463471.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Eichholz KM, Fessler RG. Is the X STOP interspinous implant a safe and effective treatment for neurogenic intermittent claudication? Nat Clin Pract Neurol. 2006;2(1):2223.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Moojen WA, Arts MP, Jacobs WC, van Zwet EW, van den Akker-van Marle ME, Koes BW, et al. Interspinous process device versus standard conventional surgical decompression for lumbar spinal stenosis: randomized controlled trial. BMJ. 2013;347:f6415.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 21

    Moojen WA, Arts MP, Jacobs WCH, van Zwet EW, van den Akker-van Marle ME, Koes BW, et al. IPD without bony decompression versus conventional surgical decompression for lumbar spinal stenosis: 2-year results of a double-blind randomized controlled trial. Eur Spine J. 2015;24(10):22952305.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22

    Moojen WA, Schenck CD, Lycklama À Nijeholt GJ, Jacobs WCH, Van der Kallen BF, Arts MP, et al. Preoperative MRI in patients with intermittent neurogenic claudication: relevance for diagnosis and prognosis. Spine (Phila Pa 1976).2018;43(5):348355.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    Stucki G, Liang MH, Fossel AH, Katz JN. Relative responsiveness of condition-specific and generic health status measures in degenerative lumbar spinal stenosis. J Clin Epidemiol. 1995;48(11):13691378.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Stucki G, Daltroy L, Liang MH, Lipson SJ, Fossel AH, Katz JN. Measurement properties of a self-administered outcome measure in lumbar spinal stenosis. Spine (Phila Pa 1976).1996;21(7):796803.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 25

    Tuli SK, Yerby SA, Katz JN. Methodological approaches to developing criteria for improvement in lumbar spinal stenosis surgery. Spine (Phila Pa 1976).2006;31(11):12761280.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 26

    Deyo RA, Diehl AK. Patient satisfaction with medical care for low-back pain. Spine (Phila Pa 1976).1986;11(1):2830.

  • 27

    Deyo RA, Patrick DL. The significance of treatment effects: the clinical perspective. Med Care. 1995;33(4 suppl):AS286AS291.

  • 28

    Hutchinson PJ, Laing RJ, Waran V, Hutchinson E, Hollingworth W. Assessing outcome in lumbar disc surgery using patient completed measures. Br J Neurosurg. 2000;14(3):195199.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 29

    Koes BW, van Tulder MW, Thomas S. Diagnosis and treatment of low back pain. BMJ. 2006;332(7555):14301434.

  • 30

    Patrick DL, Deyo RA. Generic and disease-specific measures in assessing health status and quality of life. Med Care. 1989;27(3 suppl):S217S232.

  • 31

    Patrick DL, Deyo RA, Atlas SJ, Singer DE, Chapin A, Keller RB. Assessing health-related quality of life in patients with sciatica. Spine (Phila Pa 1976).1995;20(17):18991909.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 32

    Roland M, Morris R. A study of the natural history of low-back pain. Part II: Development of guidelines for trials of treatment in primary care. Spine (Phila Pa 1976).1983;8(2):145150.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 33

    Roland M, Morris R. A study of the natural history of back pain. Part I: Development of a reliable and sensitive measure of disability in low-back pain. Spine (Phila Pa 1976).1983;8(2):141144.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 34

    Schoppink LE, van Tulder MW, Koes BW, Beurskens SA, de Bie RA. Reliability and validity of the Dutch adaptation of the Quebec Back Pain Disability Scale. Phys Ther. 1996;76(3):268275.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 35

    Carlsson AM. Assessment of chronic pain. I. Aspects of the reliability and validity of the visual analogue scale. Pain. 1983;16(1):87101.

  • 36

    Melzack R. The McGill Pain Questionnaire: major properties and scoring methods. Pain. 1975;1(3):277299.

  • 37

    Melzack R. The McGill Pain Questionnaire: from description to measurement. Anesthesiology. 2005;103(1):199202.

  • 38

    Sullivan GM, Artino AR Jr. Analyzing and interpreting data from Likert-type scales. J Grad Med Educ. 2013;5(4):541542.

  • 39

    Ostelo RWJG, de Vet HCW. Clinically important outcomes in low back pain. Best Pract Res Clin Rheumatol. 2005;19(4):593607.

  • 40

    van Geest S, Kuijper B, Oterdoom M, van den Hout W, Brand R, Stijnen T, et al. CASINO: surgical or nonsurgical treatment for cervical radiculopathy, a randomised controlled trial. BMC Musculoskelet Disord. 2014;15:129.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 41

    Nunley PD, Patel VV, Orndorff DG, Lavelle WF, Block JE, Geisler FH. Five-year durability of stand-alone interspinous process decompression for lumbar spinal stenosis. Clin Interv Aging. 2017;12:14091417.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 42

    Weber C, Giannadakis C, Rao V, Jakola AS, Nerland U, Nygaard ØP, et al. Is there an association between radiological severity of lumbar spinal stenosis and disability, pain, or surgical outcome?: A multicenter observational study. Spine (Phila Pa 1976).2016;41(2):E78E83.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 43

    Strömqvist BH, Berg S, Gerdhem P, Johnsson R, Möller A, Sahlstrand T, et al. X-Stop versus decompressive surgery for lumbar neurogenic intermittent claudication. Spine (Phila Pa 1976).2013;38(17):14361442.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 44

    Lønne G, Johnsen LG, Rossvoll I, Andresen H, Storheim K, Zwart JA, Nygaard ØP. Minimally invasive decompression versus x-stop in lumbar spinal stenosis: a randomized controlled multicenter study. Spine (Phila Pa 1976).2015;40(2):7785.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 45

    Richter A, Halm HF, Hauck M, Quante M. Two-year follow-up after decompressive surgery with and without implantation of an interspinous device for lumbar spinal stenosis: a prospective controlled study. J Spinal Disord Tech. 2014;27(6):336341.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

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