Spinal Cord Stimulation for Restoration of Function in Lower-Limb Amputees, 90-Day: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Spinal Cord Stimulation for Restoration of Function in Lower-Limb Amputees, 90-Day (NCT04547582), a na na study. The primary outcome is Number of Participants Experiencing Serious Device-related Adverse Events up to 90 Days Following Implantation.

2. Clinical Question

The research also addressed sensory and functional questions, including phantom limb pain, evoked sensations, and the ability to use a prosthetic limb with neural signals. Those aims provide context for the intervention, but the listed primary endpoint is a count of participants with serious device-related adverse events, not a measure of pain relief or prosthesis performance. The registry record lists these as secondary outcomes: change in phantom limb pain using the McGill Pain Questionnaire, qualitative self-report of evoked sensations, and ability to use a prosthetic limb with neural signals. The record does not report comparative efficacy estimates. Because there was no control group, observed changes cannot by themselves establish what would have happened without stimulation.

3. Trial Design

The registry record describes a single-group study of spinal cord stimulation in lower-limb amputees. Allocation is listed as not applicable, and masking is listed as none. The study is not a randomized comparison, so the design does not support a like-for-like comparison between intervention and control groups. The listed enrollment is 4, while the primary outcome description states that one participant was implanted with spinal cord stimulation leads. These figures refer to different aspects of the record: overall enrollment and the population identified for the primary safety outcome.

The intervention is named as a spinal cord stimulator. Its description refers to placement of 2-3 leads in the lumbar epidural space. The planned research goals included characterizing stimulation-evoked sensations, examining the relationship between stimulation settings and sensation quality, assessing prosthesis control with sensory stimulation, and measuring phantom-limb perception and associated pain. The listed secondary outcomes address phantom limb pain, self-reported sensations, and use of a prosthetic limb with neural signals.

The primary endpoint concerns serious device-related adverse events during the study and up to 90 days following implantation. The record identifies examples of events considered serious, including infection, hospitalization, withdrawal due to worsening pain or intolerable dysesthesia, and certain fractures related to falls. The posted adverse-event figures identify one participant at risk for serious events in the spinal cord stimulation group.

The study began on 2021-05-27, had a primary completion date of 2023-07-03, and is listed as terminated. The registry record does not explain the reason for termination. It does not report a phase beyond “NA,” a detailed protocol for treatment delivery, or a statistical analysis plan. The stated enrollment and the number implanted should not be treated as interchangeable: the record gives one implanted participant for the primary outcome, without describing the status or outcomes of the other enrolled participants in detail.

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.

Before assignment: Enrollment is defined as completing informed consent.

Overall Study

Analysis population for the primary outcome, as defined in the registry: One participant was implanted with spinal cord stimulation leads.

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.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants Experiencing Serious Device-related Adverse Events up to 90 Days Following Implantation, measured over 90 days.

The primary endpoint is the number of participants experiencing serious device-related adverse events during the study and up to 90 days after implantation. The unit is participants, and the endpoint is a count rather than a continuous measurement or event rate. The listed examples include unresolved superficial infection resulting in lead removal, deep infection, inpatient hospitalization, withdrawal because of worsening pain or intolerable dysesthesia, and fracture due to falls related to study interventions.

A participant-level safety count is useful for describing how many people experienced at least one event meeting the endpoint definition. It is distinct from a count of all event episodes: a participant with more than one qualifying event would still be counted once under a participant-count endpoint. The registry record does not provide a breakdown by event type or report whether any participant experienced multiple qualifying events.

This endpoint is relevant to an implanted device intervention because it focuses on serious harms associated with the device or study procedures. It does not measure sensation quality, phantom limb pain, or prosthesis control; those questions are addressed among the listed secondary outcomes. In the posted results, no serious device-related adverse events are reported among the one participant identified as implanted and at risk for the primary outcome. With such a small safety population, the count is a description of the recorded observation, not a precise estimate of the frequency of serious harms in a broader population.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record describes a single-group study with no masking and no randomized allocation. The primary endpoint is a participant count for serious device-related adverse events, with follow-up through 90 days after implantation. The posted outcome is therefore naturally read as a descriptive count within the observed group. The record lists 4 participants enrolled, while the primary outcome description identifies one implanted participant. The relevant denominator for interpreting the stated primary safety result is the one participant identified as implanted and at risk, not the overall enrollment by itself.

What does a participant count tell us?

A participant count records how many people meet an endpoint definition. For an adverse-event endpoint, counting participants avoids treating multiple events in one person as though they were multiple affected people. It answers the question of whether any participant met the defined criterion, but it does not show how many event episodes occurred or how long an event lasted. The record does not provide event-level detail for the non-serious event or describe a breakdown of serious-event types.

General statistical principle: counts are most informative when the number of people observed is large enough to reveal a stable pattern. With very few people, each person's outcome has a large influence on the overall description. A count of zero is a valid account of what was reported, but it cannot rule out events that were not observed in such a small group. A confidence interval, when reported, represents uncertainty around an estimate under its statistical assumptions; the registry record does not report one for this primary outcome.

Why does the single-group design matter?

In a controlled comparison, outcomes can be compared between groups to estimate how they differ under the study conditions. This study has no like-for-like control group, so its event count has no concurrent comparison. The design can describe the experience recorded among participants receiving spinal cord stimulation, but it cannot establish whether the observed count is higher or lower than would have occurred without the intervention. General statistical principle: causal interpretation depends on design and assumptions, not merely on observing outcomes after treatment.

The absence of masking is also part of the recorded design. The record does not describe who was aware of treatment assignment, and there is no comparison assignment to conceal. For subjective outcomes such as self-reported sensations or pain, awareness can be relevant to measurement and interpretation. However, the registry entries do not establish whether or how this affected any outcome in this study, so it should be treated as a design consideration rather than a demonstrated source of bias.

What does the record say about statistical analysis?

The registry record lists 0 analyses. It does not report a statistical analysis plan, an inferential model, confidence intervals, hypothesis tests, covariate adjustments, or a method for handling repeated measurements. The primary endpoint is a count and is presented descriptively in the available safety figures. No unreported analysis should be inferred from the endpoint's wording or from the broader research aims.

General statistical principle: an analysis plan specifies in advance how outcomes will be defined, summarized, and compared. For count outcomes, the choice between a simple participant count, a rate, or a model-based estimate depends on the design, follow-up, and data structure. A rate would require a defined time-at-risk denominator, and a comparative model would require a suitable comparison structure. The registry record does not report such analyses for this outcome. It is therefore most appropriate to describe the recorded counts without adding a model or interpretation that the record does not support.

What is over-dispersion, and does it apply?

General statistical principle: over-dispersion occurs when count data vary more than a chosen statistical model expects. It can make standard errors too small if a model assumes less variability than the data contain. Assessing it requires adequate event data and a model for counts. The registry record does not report a count model, and the primary result is a participant count in a very small observed population. There is no basis in the record to assess over-dispersion or to select a model that accounts for it.

How should sample-size planning be read?

Any sample-size illustrations associated with a reported observed effect are planning exercises, not observed power and not evidence that an effect was detected. General statistical principle: a planning calculation depends on assumptions about the effect to detect, significance level, allocation, and statistical method. The registry record does not report the study's own sample-size justification or a detailed statistical plan. The stated enrollment of 4 is an enrollment figure; it should not be treated as proof that the study was adequately powered for safety or efficacy questions.

Since the primary outcome is rare-event safety reporting in a very small implanted population, descriptive interpretation is central. The observed absence of a serious event is informative as a record of what happened to the identified participant, but it has limited capacity to characterize uncommon risks. The registry record does not report an uncertainty interval or analysis that would quantify that limitation. These are limits on statistical precision, not evidence for or against the intervention's effect on pain or function.

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("Spinal cord stimulation")
n      <- c(1)
events <- c(0)
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  Spinal cord stimulation  1  0  0.0  0.0  97.5  0.0  79.3  1.3  84.2

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary safety outcome and several secondary outcomes, including phantom limb pain measured using the McGill Pain Questionnaire, qualitative self-report of evoked sensations, and ability to use a prosthetic limb with neural signals. It also states that there are 8 outcome measures. However, the record does not report a multiplicity strategy for interpreting results across outcomes, such as a hierarchy, adjustment, or other approach to controlling the chance of false-positive findings when multiple questions are examined.

The record lists 0 analyses. It does not report which analysis populations were used for the secondary outcomes, whether outcomes were assessed repeatedly, or whether a particular analysis set was defined for the primary endpoint. The primary outcome description identifies one implanted participant, but the record does not explain in detail how the remaining enrolled participants were handled or whether they contributed to other outcomes. Enrollment and implantation should therefore not be assumed to define the same analysis population.

Missing-data handling is not reported in the registry record. The record does not state whether any outcome observations were missing, how incomplete follow-up was treated, or whether any participants withdrew. The study status is listed as terminated, but the reason for termination and its relationship to follow-up or data completeness are not reported. The primary endpoint specifies a 90-day observation window, but the record does not provide a participant-level account of follow-up completion.

General statistical principle: when outcomes or follow-up are incomplete, the interpretation depends on why data are missing and how the analysis handles them. The registry record does not provide enough information to assess this. The posted serious-event count can be described for the identified at-risk participant, but should not be generalized as though complete outcome data were documented for all enrolled participants.

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 non-serious adverse event terms

The serious adverse-event figures report one participant at risk and zero participants with a serious device-related adverse event in the spinal cord stimulation group. The primary endpoint covers events during the study and up to 90 days following implantation. The record lists no deaths. These figures are participant counts, not a rate per person-time and not a comparison with another group.

The adverse-event record separately lists one participant at risk for other events and one participant with an other adverse event. That category should not be combined with the serious-event count: the registry reports no serious events and one other adverse event. The specific non-serious event and its relationship to the intervention are not reported in the registry record. The serious event terms list is empty, and no event-level narrative is included in the registry record recorded for this analysis.

The outcome description gives examples of events that could count as serious, including infection, hospitalization, withdrawal due to worsening pain or intolerable dysesthesia, and fractures due to falls related to study interventions. The reported zero means no qualifying serious event was recorded for the identified participant during the stated window. It does not demonstrate that such events are impossible or provide a precise estimate of their frequency in a larger population. The small at-risk population makes the result descriptive, and the registry record does not report a confidence interval or another estimate of uncertainty.

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

The result means that the registry record reports no serious device-related adverse event among the one participant identified as implanted and at risk for the primary safety endpoint. It also records one participant with an other, non-serious adverse event and no deaths. Those are observations in the stated group; they do not establish the safety profile of spinal cord stimulation in a broader population.

The result does not show whether stimulation reduced phantom limb pain, generated naturalistic sensations, or improved prosthesis control. Those topics appear among the study's goals and listed secondary outcomes, but numerical findings for them are not reported in the registry record used for this analysis. The primary endpoint is a safety count, not a measure of treatment benefit. It should not be read as evidence for or against effectiveness.

The study was single group, with no randomized comparator and no masking. Without a control group, the observed outcomes cannot be set against outcomes under an alternative condition. Even if a change in pain or function were reported, the design alone would not show how much of that change was caused by the intervention. The registry record does not report inferential analyses to address such questions.

The listed enrollment of 4 does not mean that 4 participants contributed to the primary safety outcome: its description identifies one implanted participant. The record does not explain the status or outcome contribution of the other enrolled participants. It also does not report the reason the study was terminated or whether follow-up was complete. These gaps limit interpretation of the overall study experience.

General statistical principle: absence of an observed event in a small group is not the same as evidence that the event risk is zero. Sparse data provide limited precision, and the record includes no confidence interval or model-based estimate. The result is best read as a report of what was observed for the identified participant, with substantial uncertainty about how well that observation represents others.

14. Why This Trial Matters Statistically

This study illustrates why the denominator and the outcome definition matter when interpreting safety findings. The registry record lists enrollment of 4, but identifies one implanted participant for the primary endpoint. Reporting the serious-event count alongside the number at risk makes clear that the primary observation concerns that implanted participant, rather than automatically applying to everyone enrolled.

It also demonstrates the distinction between a primary safety question and broader clinical research aims. The study sought to characterize sensations, examine stimulation parameters, assess prosthesis control, and quantify phantom-limb perception and associated pain. Yet its primary endpoint is a count of participants with serious device-related adverse events. These are different questions and require separate outcome evidence. A safety count cannot substitute for measurements of pain or function.

The single-group design is another important statistical feature. Without a concurrent control group, there is no direct comparison to distinguish outcomes associated with stimulation from changes that might occur otherwise. This does not invalidate a descriptive report, but it limits what the reported counts can establish. The record's status as terminated, combined with the absence of a reported reason and analysis plan, also underscores the importance of transparent reporting about follow-up and analysis populations.

Finally, the very small implanted safety population shows how a zero event count can be both accurate as a description and limited as an estimate. General statistical principle: uncommon outcomes require substantial information to characterize precisely. A small study may document that no serious event occurred among its observed participants while leaving considerable uncertainty about risk beyond them. Reading such a result requires attention to the observed count, the population represented, and the limits of the design—not extrapolation to conclusions the record does not support.

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.

The primary safety result is based on one participant identified as implanted, while total enrollment is listed as 4. The registry record does not explain the participation status, exposure, follow-up, or outcome contribution of the remaining enrolled participants. This limits interpretation of the overall enrollment figure and prevents treating it as the primary endpoint denominator.

The study is single group, with no randomized allocation, no control group, and no masking. Consequently, the registry record cannot support a like-for-like comparison or a causal estimate against an alternative condition. The record does not report a statistical analysis plan, inferential model, confidence interval, or hypothesis test. It also does not report an explanation for termination or details of missing-data handling and follow-up completeness.

The primary endpoint is a serious-event participant count through 90 days after implantation. The record does not provide event-level detail for the other adverse event, a breakdown of safety events by type, or additional measures of exposure time. It reports no serious device-related adverse events among the one participant at risk and no deaths, but the small observed population gives limited information about uncommon events. The absence of an event in this record should not be generalized as evidence that serious events cannot occur.

The study's aims include sensory, pain, and prosthetic-use questions, but numerical results for those outcomes are not reported in the registry record. The reason for study termination, the analysis population for secondary outcomes, and the handling of incomplete observations are also not reported. These limitations constrain both the statistical interpretation and the extent to which the results can be applied beyond the recorded participant.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Spinal Cord Stimulation for Restoration of Function in Lower-Limb Amputees, 90-Day — NCT04547582.
• Registry record last updated 2026-01-07; status last verified 2025-12.
• Results first posted 2026-01-07.
• 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 record describes a terminated, single-group study of spinal cord stimulation in people with lower-limb amputation. Enrollment is listed as 4; the primary outcome description identifies one implanted participant. The study began on 2021-05-27, with primary completion on 2023-07-03. Allocation is not applicable, and masking is listed as none.

The primary endpoint counts participants with serious device-related adverse events during the study and up to 90 days following implantation. The posted safety figures report zero serious events among one participant at risk, one other adverse event among one participant at risk, and no deaths. The record lists phantom limb pain, evoked sensations, and prosthetic-limb use among secondary outcomes. Numerical results for those outcomes, a statistical analysis plan, missing-data procedures, and the reason for termination are not reported in the registry record.