Postmarket Outcomes Study for Evaluation of the Superion™ Spacer: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Postmarket Outcomes Study for Evaluation of the Superion™ Spacer (NCT04563793), a registered phase not stated study. The primary outcome is Low Back Pain Responder Rate.

2. Clinical Question

3. Trial Design

The registry describes a completed postmarket outcomes study of the Superion™ IDS for lumbar spinal stenosis. Its stated purpose was to compile real-world outcomes in routine clinical practice. The listed intervention is a device, and the arm description says all patients were to receive the IDS for their moderate lumbar spinal stenosis symptoms. Enrollment is recorded as 129. The registry gives a start date of 2020-10-08, a primary completion date of 2023-03-20, and a status of COMPLETED.

The record lists one device arm and does not describe a like-for-like control arm. It identifies the study as not randomized and states that allocation is not stated. These features matter when interpreting results: an outcome observed in the device arm alone cannot, by itself, distinguish an intervention effect from changes over time, participant characteristics, other care, or other influences. The record does not report a comparator-based estimate.

The primary-outcome population is described as an Intent-to-Treat (ITT) Population of patients who receive treatment with the Superion® IDS. It includes previously implanted subjects and newly enrolled subjects up to 3 years post-procedure. The description of data for previously implanted subjects is incomplete in the registry record, so the precise data contributing to that group cannot be determined from the available description.

The registry lists 5 outcome measures and 0 analyses. Completion status and the recorded dates describe the study’s registry history; they do not establish that results for every planned follow-up timepoint are available. The primary endpoint covers assessments up to 3 years post-procedure, but follow-up completeness, the number assessed at each timepoint, and any reasons for missing assessments are not reported in the registry record. The record also does not state the allocation method, detailed enrollment criteria, or the statistical plan used for any analyses.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Intent-to-Treat (ITT) Population: Patients who receive treatment with the Superion® Indirect Decompression System (IDS). Patients include previously implanted subjects and newly enrolled subjects up to 3 years post-procedure. Data for patients previously implanted includes data which was collected retrospectively.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: All subjects who completed the baseline information. Two subjects were consented but did not complete the baseline information.

6. Primary Endpoint

The registry lists the primary outcome as Low Back Pain Responder Rate, measured over Up to 3 years post-procedure.

The primary endpoint is the Low Back Pain Responder Rate, expressed as a count of participants. A participant is described as a responder if low back pain improved by 20 mm during the last 7 days compared with baseline on the visual analogue scale (VAS). Assessments are specified at 6 months, 1 year, 2 years, and 3 years post-procedure.

A responder endpoint turns a continuous symptom measure into a classification using a stated threshold. In general, this can make the outcome easier to interpret as the number of people meeting a prespecified degree of improvement. It also loses information: participants just above and below the threshold are assigned different classifications even if their underlying scores are close, while people with different amounts of improvement above the threshold are counted alike. The continuous VAS results would provide complementary information, but they are not reported in the registry record.

The endpoint’s repeated timepoints can describe response over follow-up, but each assessment answers a separate time-specific question. A count at one timepoint should not be assumed to represent the same participants or the same follow-up completeness at another timepoint. The registry specifies the endpoint and follow-up schedule, but reports no responder counts, denominators by timepoint, estimates of uncertainty, or analyses. Therefore the endpoint definition is available, while its observed results and precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a binary primary outcome: participants are counted according to whether they meet the low back pain responder definition. The definition requires an improvement of 20 mm during the last 7 days compared with baseline on the VAS. The specified assessments are at 6 months, 1 year, 2 years, and 3 years post-procedure. The outcome is reported as a count of participants, but the registry record does not provide those counts or analyses.

What does a responder count tell us?

For a binary outcome, an observed count indicates how many assessed participants fall into a category. To interpret the count as a frequency in the study group, the corresponding number assessed at that timepoint is also needed. A proportion puts the count in the context of its denominator, and a confidence interval can express uncertainty around an estimate. These are general statistical concepts; the registry record does not report the primary endpoint’s counts, denominators, proportions, or confidence intervals. No derived estimate can therefore be interpreted from the record.

Threshold-based outcomes have a particular trade-off. They translate a measurement into an understandable classification, but disregard how far a participant’s measurement lies from the cutoff once classified. A threshold can also make classifications sensitive to measurement variability near the cutoff. General interpretation is stronger when the binary responder outcome is accompanied by the underlying continuous measure and clear information about how it was collected. The registry describes the VAS comparison but does not report the underlying score distributions.

Why do repeated timepoints matter?

Each scheduled assessment addresses response at a different stage of follow-up. If the same participants contribute repeatedly, their observations are related rather than independent. In general, analyses of repeated measurements should account for that relationship when estimating change or describing trends. A response count at one timepoint should not be treated as interchangeable with a count at another, and the record does not establish that the same participants posted data at each assessment. The number assessed and the missing-data handling for each timepoint are not reported in the registry record.

Multiple outcomes and assessment times also create multiple opportunities to examine results. In general, multiplicity can increase the chance that at least one analysis appears notable by chance when many questions are tested. A prespecified statistical plan can explain which outcomes and timepoints are primary, how comparisons are organized, and whether any adjustment is used. The registry lists 5 outcome measures, but 0 analyses, and does not report a multiplicity strategy or a detailed analysis plan.

What can a confidence interval add?

In general, a confidence interval gives a range of estimates compatible with the data under the method’s assumptions and indicates how precisely an effect has been estimated. It is not a guarantee that the true value lies in that particular interval. For a binary endpoint, precision depends in part on the number of observations and the event frequency; missing data and the analysis method also matter. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed from these registry entries.

What is the role of the planning illustrations?

Planning sample-size illustrations are not observed trial results. The stated assumptions for the illustrations are a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect expressed as a fraction of the observed effect. The description specifies participants per arm for non-time-to-event outcomes and a total number of events for time-to-event outcomes. These are planning assumptions, not evidence that this study used those choices. The record identifies no randomized two-arm comparison and reports 0 analyses, so the illustrations should not be read as the study’s design justification or as observed power. The trial’s own sample-size justification is not reported in the registry record.

For count data, a statistical model may need to account for over-dispersion when the observed variability exceeds what a simpler model assumes. In general, ignoring over-dispersion can make uncertainty estimates too small and tests too optimistic. This concept applies to count outcomes where such a model is appropriate; the listed primary outcome is a participant responder count, and the registry record does not describe a count model, an over-dispersion assessment, or any fitted analysis. No particular model should be attributed to the study.

What can be inferred from the listed design?

The registry describes a nonrandomized study without a stated allocation process and lists a device arm. General statistical reasoning distinguishes descriptive results within a group from comparative effects between groups. A single-arm description can characterize outcomes among participants observed, but a comparison that estimates effects against an alternative requires a suitable comparator and methods that address differences between groups. The registry record does not describe a like-for-like control comparison. It also does not report adjusted or unadjusted effect estimates, standard errors, tests, or confidence intervals for the primary endpoint.

The study is marked COMPLETED, but completion status is not a statistical result. Likewise, the enrollment entry does not establish the number with outcome data at each follow-up timepoint. Conclusions require analysis results and their denominators, as well as a clear account of how missing measurements and repeated observations were handled. Those details are not reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Superion™ IDS 6-Month Follow-up", "Superion™ IDS 1-Year Follow-up", "Superion™ IDS 2-Year Follow-up", "Superion™ IDS 3-Year Follow-up")
n      <- c(30, 11, 8, 7)
events <- c(17, 3, 1, 2)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Superion™ IDS 6-Month Follow-up  30  17  56.7  37.4  74.5  39.2  72.6  39.1  72.7
ARM  Superion™ IDS 1-Year Follow-up  11  3  27.3  6.0  61.0  9.7  56.6  9.9  57.2
ARM  Superion™ IDS 2-Year Follow-up  8  1  12.5  0.3  52.7  2.2  47.1  2.8  48.2
ARM  Superion™ IDS 3-Year Follow-up  7  2  28.6  3.7  71.0  8.2  64.1  8.5  65.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 5 outcome measures and specifies multiple assessment times for the primary low back pain responder endpoint: 6 months, 1 year, 2 years, and 3 years post-procedure. When several outcomes or timepoints are examined, multiplicity is a general statistical concern because the more questions tested, the greater the opportunity for chance findings. A prespecified hierarchy or adjustment method can clarify how a study handles that issue. The registry record reports 0 analyses and does not state whether any multiplicity strategy was planned or used.

Missing-data information is also limited. The primary endpoint description identifies an ITT Population as patients who receive treatment with the Superion® IDS and says it includes previously implanted subjects and newly enrolled subjects up to 3 years post-procedure. It does not give the number assessed at each timepoint, the amount of missing data, reasons for missing assessments, or the method used to handle missing observations. The description of data for previously implanted subjects is incomplete in the registry record.

In general, missingness can affect both the estimate and its precision, particularly if participants with unavailable outcomes differ from those with observed outcomes. Analyses may use different assumptions or methods to address missing values, but none is described in the record. The stated population label alone does not identify how missing endpoint measurements were treated. The analysis population, exclusions, and any sensitivity analyses are not reported in the registry record. Consequently, the completeness and robustness of any endpoint result cannot be assessed from the listed information.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: covid-19 pneumonia (1.6%), pulmonary embolism (1.6%), spinal fracture (0.8%), acute coronary syndrome (0.8%), pneumocystis jirovecii pneumonia (0.8%).

For the Superion™ IDS arm, the registry lists 129 participants at risk for serious adverse events and 12 participants affected. It lists 129 at risk for other adverse events and 3 affected, and reports 0 deaths. These are participant counts, not a comparison with another arm. The registry does not report a randomized control group or a comparative safety analysis.

The listed serious adverse event terms and percentages are COVID-19 pneumonia, 1.6%; Pulmonary embolism, 1.6%; Spinal Fracture, 0.8%; Acute coronary syndrome, 0.8%; Pneumocystis jirovecii pneumonia, 0.8%; and Osteonecrosis, 0.8%. These terms describe events recorded in the registry. The information does not establish that the device caused any particular event, and the listed terms do not provide a complete account of each participant’s clinical circumstances.

Counts and percentages answer different descriptive questions, and a percentage should be interpreted with its stated event definition and population in mind. The record does not provide event timing, duration, severity details beyond the serious classification, relatedness assessments, recurrent-event information, or a comparison group’s data. The serious and other adverse event counts should not be added together: the record does not state whether participants could appear in both categories. They are safety summaries, not estimates of comparative risk.

13. What the Result Does, and Does Not, Mean

The registry record establishes what the study set out to describe: real-world outcomes after treatment with the Superion™ IDS in routine clinical practice. It identifies lumbar spinal stenosis as the condition, records enrollment as 129, and describes a primary low back pain responder endpoint based on improvement from baseline on the VAS. The endpoint is scheduled for assessment through 3 years post-procedure. The record also includes safety counts for the listed device arm.

Those details do not establish the observed primary outcome. No responder results or analyses are reported in the registry record. Without the number of participants meeting the definition and the corresponding number assessed at each timepoint, neither the frequency of response nor its precision can be judged. The registry’s COMPLETED status does not substitute for outcome data.

The study is described as nonrandomized, with allocation not stated, and no like-for-like control comparison is provided. Therefore, even if within-arm outcomes were available, they would describe observations among participants rather than establish what would have happened under a different treatment. Changes could reflect factors other than the device, and the design information does not allow those influences to be separated.

The safety counts likewise have a descriptive role. They report participants affected in the device arm and identify several serious adverse event terms, but do not establish causation or comparative safety. No control-group safety data or detailed event-level account is reported in the registry record.

In general, interpreting a clinical study requires more than an endpoint definition and an enrollment entry. Readers need reported outcome estimates, their denominators and uncertainty, clear methods for missing observations, and a design capable of addressing the question being asked. Here, the available registry entries clarify the planned question and some safety reporting, but do not support a conclusion about the size, precision, or comparative effect of the device on low back pain.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of the difference between a registry description and an analyzed clinical result. The record identifies a real-world postmarket aim, an intervention, an outcome definition, scheduled follow-up, and safety counts. Those elements help readers understand the question being asked, but they do not replace endpoint results or an analysis plan.

The primary endpoint uses a responder threshold on a patient-reported pain measure. Such endpoints can be understandable because they classify participants according to a stated improvement criterion. At the same time, they require careful reporting of who was assessed, how baseline and follow-up values were obtained, and what happened to missing measurements. Repeated assessment through 3 years makes timepoint-specific reporting especially relevant. These details are not reported in the registry record.

The registry also makes the design limitation visible: it describes a nonrandomized study, does not state allocation, and does not provide a like-for-like control comparison. Statistical interpretation must match the design. Descriptive outcomes in a treated group can inform what was observed in that group, but cannot alone provide the same type of evidence as a randomized comparison. That distinction is important when communicating real-world evidence.

Finally, the record lists 5 outcome measures and 0 analyses. A transparent analysis plan and posted results would help readers assess how outcomes and timepoints were handled, how missingness affected estimates, and how precise any findings were. The registry entries make those evidence gaps apparent without implying that a result can be reconstructed from enrollment or status. The safety summaries offer additional descriptive context, while remaining distinct from comparative safety evidence.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several trial-specific limitations follow directly from the registry description. The study is identified as not randomized, allocation is not stated, and only the Superion™ IDS arm is listed. No like-for-like control comparison is described. As a result, the record does not support a comparative estimate of outcomes against another treatment or a control condition.

The primary endpoint is defined, but no analyses are reported. The registry lists 0 analyses, so there are no posted responder counts, timepoint denominators, effect estimates, confidence intervals, or p-values to evaluate. The study’s completed status and enrollment entry do not indicate how many participants contributed primary endpoint data at each scheduled assessment.

The endpoint description covers follow-up through 3 years post-procedure and refers to both previously implanted subjects and newly enrolled subjects. The description of previously implanted subjects’ data is incomplete. The registry record does not explain the relationship between these data sources, provide timepoint-specific follow-up completeness, or state how missing measurements were handled. This limits assessment of the population represented by any potential result.

The registry lists 5 outcome measures but does not report the statistical plan, multiplicity methods, analysis population details beyond its brief ITT description, or sensitivity analyses. It also does not provide the continuous VAS results that would complement the responder classification. The sample-size illustration assumptions do not establish the study’s own design justification or analysis strategy.

Safety information is limited to participant counts and listed event terms. The registry does not provide detailed timing, causality assessments, recurrence information, or comparative safety data. Taken together, these limitations mean the record supports a description of the study and its posted safety figures, but not an assessment of primary endpoint effect size or precision.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Postmarket Outcomes Study for Evaluation of the Superion™ Spacer — NCT04563793.
• Registry record last updated 2025-01-13; status last verified 2024-09.
• Results first posted 2025-01-13.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

The registry describes NCT04563793, the Postmarket Outcomes Study for Evaluation of the Superion™ Spacer, sponsored by Boston Scientific Corporation. It lists lumbar spinal stenosis as the condition, Superion™ IDS as the device intervention, enrollment of 129, a start date of 2020-10-08, a primary completion date of 2023-03-20, and status COMPLETED. The stated aim is to compile real-world outcomes in routine clinical practice.

The primary endpoint is a low back pain responder count based on improvement of 20 mm during the last 7 days compared with baseline on the VAS, with assessments at 6 months, 1 year, 2 years, and 3 years post-procedure. The record describes a nonrandomized study, does not state allocation, lists 5 outcome measures, and reports 0 analyses. It includes safety counts for the device arm: 12 participants affected by serious adverse events, 3 affected by other adverse events, and 0 deaths. Primary outcome analyses and timepoint-specific follow-up details are not reported in the registry record.