Neuromodulation Techniques After SCI: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Neuromodulation Techniques After SCI (NCT04241250), a randomized phase 2 study. The primary outcome is 10-meter Walking Speed (m/Sec).

2. Clinical Question

The registry describes the work as a pilot intended to provide preliminary evidence for designing future trials involving Veterans and civilians with spinal cord injury. Its summary places the study in the context of spinal stimulation combined with intensive walking rehabilitation and the possible use of robotic exoskeletons. Those aims explain the clinical question, but they do not establish that either intervention improves walking. The posted endpoint information is incomplete for comparing the randomized groups, and the record does not report outcome values or a treatment-effect estimate.

3. Trial Design

This was a randomized, phase 2, parallel-group trial with no masking. The registry lists enrollment of 4 and a completed status. The sponsor was the VA Office of Research and Development. The recorded start date was 2020-06-01, and primary completion was 2024-07-31. The condition was spinal cord injury.

The trial compared two device interventions. Both included exoskeleton-assisted walking, followed by a stimulation treatment. In EAW+SCES, participants had three months of exoskeleton training followed by six months of epidural stimulation. In EAW+TS, they had three months of exoskeleton training followed by six months of transspinal stimulation. Randomization is intended to support a fair comparison by assigning participants to groups by chance, but it does not ensure that groups will be comparable in a very small trial.

The primary outcome was 10-meter walking speed. The registry lists baseline, post-intervention 1 at three months following baseline, and post-intervention 3 at six months following post-intervention 1. The outcome description also says measurements were conducted over the course of nine months and describes a baseline test and a test after six months from implantation of epidural stimulation in the EAW+SCES group. These descriptions do not establish a complete set of comparable measurements across both arms.

Participants in EAW+TS withdrew before outcome variables were assessed. The record describes measurements for EAW+SCES, but does not provide the actual walking-speed values, the number measured at each time point, or a comparative estimate. It also lists secondary outcomes concerning fat mass, oxygen uptake, fasting lipid profile, and fat-free mass. The registry record does not report the statistical analysis plan, allocation details beyond randomization, or the reasons participants withdrew.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Participants in EAW+TS withdrew from the trial before the outcome variables were assessed. In the EAW+SECES, participants had undergone exoskeletal-10 meter walking test at baseline (BL) and after 6 months (P3) from implantation of spinal cord epidural stimulation (SCES). The 10-meter walking test was performed 100% exoskeletal assisted walking (EAW) or reduced EAW (RED-EAW). At post-intervention 3, the RED-EAW was tested twice either with SCES off or with SCES On.

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 10-meter Walking Speed (m/Sec), measured over Baseline (BL), Post-Intervention 1 (P1; 3 months following BL) and Pos-intervention 3 (P3; 6 months following P1).

The primary endpoint was 10-meter walking speed, expressed in meters per second. The registry describes a test in which a participant, after being fitted in a robotic exoskeleton, walks a 10-meter distance while time and speed are determined. Walking speed is a continuous measure: it can take values along a scale rather than placing each participant in a category. The registry identifies the mean as the summary parameter and standard deviation as the measure of dispersion.

Walking speed is used to describe performance over a specified distance in a way that can be compared across measurements. Repeating the test can show how a participant’s measured speed changes over time. A group mean can summarize the measurements, while the standard deviation describes how spread out individual measurements are around that mean. Those summaries alone do not establish that a change was caused by treatment, particularly when the groups are not both observed at the relevant time points.

The registry lists baseline and later assessments, including post-intervention 1 and post-intervention 3. Its description also refers to measurements over nine months and to an assessment after six months from implantation in the epidural-stimulation group. Participants in the transspinal group withdrew before outcome variables were assessed. Actual walking-speed means, standard deviations, and a comparison between arms are not reported in the registry record. Therefore, the endpoint definition is available, but the posted information does not show the size or precision of an outcome difference.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is a continuous outcome summarized by its mean and standard deviation. The mean represents the average measured walking speed in a group at a specified time point. The standard deviation describes variability among the measured speeds. These are descriptive statistics: they summarize observations, but do not on their own quantify the uncertainty in a treatment comparison or establish a cause for differences.

What does a comparison estimate?

In a randomized trial, an analysis may compare group means at a specified time point or compare changes from baseline. These approaches answer related but distinct questions. A follow-up comparison asks how the groups differ at that visit; a change comparison asks how much each group changed relative to its own baseline and then contrasts those changes. With repeated measurements, a model may also assess the pattern across visits. These are general methods, not claims about the analysis used in this trial: the registry record does not report the statistical plan or identify a primary contrast.

The outcome record names baseline, post-intervention 1, and post-intervention 3, and gives a timeframe involving three months following baseline and six months following post-intervention 1. The endpoint description also refers to measurement over nine months and to testing after six months from implantation in EAW+SCES. Multiple visits create multiple possible summaries and comparisons. Choosing among them requires a prespecified analysis plan, which is not reported in the registry record.

How should uncertainty be understood?

A confidence interval is a range of estimates compatible with the observed data under the assumptions of a statistical method. It communicates precision: a narrower interval indicates greater precision, while a wider interval indicates greater uncertainty. A point estimate without an interval can obscure how uncertain the result is. The registry record does not report a primary-outcome estimate or confidence interval, so the precision of a treatment comparison cannot be evaluated.

A p-value is a measure, under a specified statistical model and null hypothesis, of how incompatible the observed data are with that hypothesis. It is not the probability that a treatment works, and it does not measure the size or clinical importance of an effect. The registry record does not report a p-value for the primary outcome or explain which test would have been used. The significance level of 0.05 appears among the assumptions for planning illustrations; it should not be mistaken for a reported trial result or evidence that a particular analysis was performed.

What can a planning calculation show?

Sample-size calculations can illustrate how many participants per arm might be needed to detect an effect under chosen assumptions. The listed planning assumptions use a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect expressed as a stated fraction of the observed effect. Those calculations are planning illustrations, not observed power and not the trial’s own design justification. The registry record does not report a sample-size justification. The observed primary-outcome effect needed for such an illustration is also not reported in the registry record, and no numerical planning result is available in the record.

Sample size and power are different from the amount of evidence actually observed. A planned sample size is based on assumptions about variability, effect size, and statistical testing. Observed power is not a substitute for reporting an estimate and its uncertainty. For this trial, enrollment was 4, and the transspinal participants withdrew before primary-outcome assessment. The available registry information therefore does not support a useful estimate of a between-arm outcome effect, regardless of any planning illustration.

Why does over-dispersion matter?

Over-dispersion is a general concept that arises when observed variability is greater than a statistical model assumes. If a model understates variability, its uncertainty estimates can be too small and its intervals or tests can be misleading. For a continuous outcome such as walking speed, the standard deviation is one way to describe variation in the measured data. With very few observations, estimating that variation is difficult. The registry record does not report walking-speed standard deviations, so over-dispersion cannot be assessed for this trial.

More generally, a valid analysis depends on how measurements are distributed, whether observations are independent, how repeated measures are handled, and whether missingness is related to outcomes. The registry record does not give enough detail to evaluate those assumptions or identify any model used. This is not evidence that an assumption was violated; it means the analysis details needed to assess it are not reported in the registry record.

What does missing outcome data change?

When an arm has no assessed primary outcomes, a direct randomized comparison at that endpoint cannot be derived from the outcome data described in the registry record. General approaches to missing data depend on the amount and pattern of missingness, its likely causes, and the estimand of interest. They may require assumptions that cannot be checked from the available record. No imputation method, sensitivity analysis, or missing-data model is reported.

The registry’s account of withdrawal is especially important because the missing measurements are in EAW+TS, rather than simply being scattered among participants in both groups. The reasons for withdrawal are not reported, so it is not possible to judge whether the missingness might be related to outcome or intervention. A result based only on EAW+SCES measurements, if one were available, would not by itself estimate the randomized contrast between EAW+SCES and EAW+TS.

10. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when an analysis considers several outcomes, time points, or statistical contrasts. The registry lists seven outcome measures and two analyses, and the primary walking-speed outcome has several time points. Looking at multiple comparisons can increase the chance of finding an apparently notable result by chance if no adjustment or prespecified hierarchy is used. Whether and how to address that issue depends on the analysis plan. The plan for multiplicity is not reported in the registry record.

The endpoint listing includes baseline, post-intervention 1, and post-intervention 3. A study could compare arms at one follow-up, compare changes, or assess a pattern over time; these are different estimands. The record indicates that the primary outcome has several categories or time points and is not reduced to one comparison. It does not identify which contrast was intended as the decisive test or report an adjustment for multiple testing.

Missingness is also material. Participants in EAW+TS withdrew before outcome variables were assessed. For EAW+SCES, the registry describes baseline and later testing, but does not report the number of completed measurements at each visit or the outcome values. Reasons for withdrawal, imputation procedures, sensitivity analyses, and definitions of analysis populations are not reported in the registry record.

In a randomized trial, an intention-to-treat analysis generally seeks to retain participants in their assigned groups, but that principle does not itself resolve missing outcomes. The registry record does not say whether an intention-to-treat, per-protocol, or other analysis population was used. Without those details and the outcome data, the effects of missingness and the interpretation of any analysis cannot be assessed.

11. 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 registry lists two participants at risk in each intervention group for serious adverse events, and zero affected by serious adverse events in each group. It lists zero deaths in both groups. For other, non-serious adverse events, two participants were at risk in each group; zero were affected in EAW+SCES and one was affected in EAW+TS. These are participant counts in the registry record, not rates or estimates of comparative safety.

The serious adverse event terms list is empty. The registry record does not report event descriptions, severity details for the other adverse events, timing, relatedness to treatment, or whether one participant experienced more than one event. A count of participants affected should not be treated as a count of all events unless the registry explicitly reports that equivalence.

With enrollment of 4, these safety counts are descriptive and involve very few participants. Zero recorded serious adverse events does not establish that serious events cannot occur, and the one participant recorded with other adverse events does not establish a difference between interventions. The record does not provide enough information for a comparative safety estimate.

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

The registry record describes a randomized comparison of two exoskeleton-assisted walking approaches that differed in the stimulation method following training. It specifies 10-meter walking speed as the primary outcome and identifies several assessment times. It also records that participants in the transspinal arm withdrew before outcome assessment. These registry entries describe the trial and its outcome collection, but they do not show whether either intervention changed walking speed or whether one approach differed from the other.

The record does not report numerical primary-outcome results, an estimated treatment effect, a confidence interval, or a p-value. Consequently, the magnitude and precision of any difference are not available for interpretation. The absence of a reported comparison must not be read as evidence that the treatments are equivalent, that there was no effect, or that either intervention was effective. It indicates that the registry information does not establish those conclusions.

Enrollment of 4 and the lack of assessed primary outcomes for EAW+TS sharply limit comparative interpretation. Even if measurements in EAW+SCES were reported, changes within that group alone would not identify what would have happened under the alternative intervention. A between-group conclusion requires outcome information and an appropriate analysis that respects the randomized assignment and addresses missing data.

The trial is identified as a pilot intended to inform future clinical-trial design. Pilot work can be useful for assessing feasibility and informing later research, but the registry record does not report enough information to judge feasibility outcomes or derive a precise treatment-effect estimate. Its listed secondary outcomes and adverse-event counts add context, but do not fill the gap in the primary comparison. Any inference about broader populations or clinical consequences would go beyond what the posted results establish.

13. Why This Trial Matters Statistically

This trial is statistically notable because its question involves a randomized comparison, a continuous primary outcome, repeated assessment times, and withdrawal before the transspinal group’s outcome assessment. Those features make the distinction between a trial’s intended comparison and the data actually available especially important. Randomization supports comparative inference only when outcome information and an appropriate analysis are available to estimate the contrast.

The primary outcome, 10-meter walking speed, is a direct measured quantity with a defined unit and test procedure. Such specificity is useful: readers can understand what was measured and when. At the same time, multiple time points leave several possible comparisons, and the registry record does not report a single primary contrast or analysis plan. Statistical interpretation depends not only on defining an endpoint, but also on specifying how its measurements will answer the research question.

The small enrollment and incomplete outcome assessment illustrate why estimates and their uncertainty matter more than a simple label such as completed or randomized. In general, very small samples provide limited information about variability and can yield highly uncertain estimates. Here, the registry record does not post the numerical endpoint data needed to assess either an estimate or its precision.

The pilot rationale is relevant to future research planning, but planning assumptions should not be confused with evidence of a treatment effect. A planning illustration based on an observed effect is not observed power and is not a substitute for a reported comparison. Clear reporting of the analysis plan, outcome values, missingness, and uncertainty would be needed for readers to evaluate the evidence and its relevance to later trials.

14. 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 main trial-specific limitation in the registry record is that participants in EAW+TS withdrew before outcome variables were assessed. The record does not give the reasons for withdrawal, so it is not possible to determine whether the decision was related to intervention burden, outcome prospects, or another circumstance. The absence of outcome assessment in that arm prevents interpretation of the intended randomized comparison from the information recorded.

Enrollment was 4. The record does not report participant-level outcome values, group means, standard deviations, or a treatment-effect estimate for walking speed. It also does not report how many EAW+SCES participants completed each listed assessment. This prevents evaluation of observed change, variability, precision, and the amount of missing data at each visit.

The timing descriptions are not fully aligned in their wording. The timeframe lists baseline, post-intervention 1 at three months following baseline, and post-intervention 3 at six months following post-intervention 1. The outcome description refers to measurements over nine months and to testing after six months from implantation of epidural stimulation. The record does not clarify how these descriptions map to all participants or whether comparable visit timing was used across arms.

The registry does not report the statistical analysis plan, the primary contrast, the analysis population, multiplicity handling, missing-data methods, or sensitivity analyses. It also does not provide a sample-size justification. These omissions do not prove that such plans or analyses were absent; they mean their details are not reported in the registry record. Together with the missing transspinal outcome assessment, they constrain the conclusions that can be drawn from the posted information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Neuromodulation Techniques After SCI — NCT04241250.
• Registry record last updated 2026-04-28; status last verified 2026-04.
• Results first posted 2026-04-28.
• 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.

18. Record Summary

The registry identifies NCT04241250, titled Neuromodulation Techniques After SCI, as a completed randomized phase 2 parallel trial with no masking. Enrollment was 4, and the sponsor was the VA Office of Research and Development. The trial compared exoskeleton-assisted walking followed by epidural stimulation with exoskeleton-assisted walking followed by transspinal stimulation.

The primary endpoint was 10-meter walking speed, measured in meters per second, with multiple time points listed. Participants in EAW+TS withdrew before outcome variables were assessed. The registry record does not report numerical primary-outcome results or a completed comparison between the interventions. It lists secondary outcomes related to body composition, oxygen uptake, and fasting lipid profile. The safety record lists no serious adverse events or deaths in either group, and one participant affected by other adverse events in EAW+TS.