Evaluation of Dual Channel vs. Single Channel FES for Dropfoot: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of Dual Channel vs. Single Channel FES for Dropfoot (NCT02494323), a na na study. The primary outcome is Ankle Movement as Good as or Better With the Segmented Electrode as With the QFE.

2. Clinical Question

The clinical question focuses on the direction of ankle movement during stimulation. The scale ranges from inverted dorsiflexion through neutral dorsiflexion to everted dorsiflexion. The study description says clinicians recorded how many subjects achieved each movement category with each electrode. The stated purpose of dual-channel stimulation was to enable balanced dorsiflexion without inversion or eversion inclinations.

The comparison is described as successive device conditions within a single-group study, not as a randomized parallel-group trial. The registry record does not report a numerical comparison of the movement distributions, a statistical estimate of the difference, or a conclusion about whether either electrode performed better. It also does not report a prespecified margin for deciding that movement was “as good as” movement with the other electrode. The clinical question is therefore identifiable from the outcome description, but the posted record does not supply the results needed to answer it.

3. Trial Design

The registry identifies this as a completed, single-group study of functional electrical stimulation for dropfoot. Enrollment was 70. The record lists the study start as 2015-03 and primary completion as 2015-06. It names Bioness Neuromodulation as sponsor. Allocation is recorded as NA, and masking as none; the record does not describe a randomized allocation or a blinded assessment.

The study description says subjects were fitted first with the L300 cuff housing the single-channel QFE and then with a modified cuff housing the dual-channel segmented electrode. Stimulation was assessed while sitting and, after optimal ankle elevation was achieved, during walking. The description also outlines an initial evaluation of four dual-channel configurations in the first 20 subjects, followed by evaluation of a configuration judged to have an advantage in 50 additional subjects. The registry record does not report which configuration was selected or provide configuration-specific results.

Ambulation tests are described for the additional subjects. The description also says that subject preference was to be recorded using a BSW Questionnaire and Subjective Survey. The listed secondary outcome is the Benefit Satisfaction Willingness to Continue questionnaire. The record does not report results for that outcome or for the survey.

The registry’s single-group classification matters when interpreting the comparison. Although the same study included both electrode types, the record does not describe randomizing the order, a separate control arm, or a like-for-like randomized comparison. Further details about the protocol, sample-size justification, analysis plan, and handling of assessments made under the different configurations are not reported in the registry record.

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: All subjects suffer from foot drop due to upper motor neuron lesion

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: Twenty subjects were evaluated to determine the most advantageous dual channel configuration. When this was determined, 50 additional subjects were evaluated to allow sufficient data do determine feasibility.

6. Primary Endpoint

The registry lists the primary outcome as Ankle Movement as Good as or Better With the Segmented Electrode as With the QFE, measured over 7 months.

The primary endpoint is titled “Ankle Movement as Good as or Better With the Segmented Electrode as With the QFE.” It concerns ankle movement during functional electrical stimulation, assessed by a clinician on a five-point scale. The categories describe movement from inverted dorsiflexion to everted dorsiflexion, with neutral dorsiflexion at the middle of the scale. The record says clinicians documented the number of subjects achieving each category with each electrode.

The endpoint is intended to describe the direction of ankle movement, which is relevant to the study’s stated aim of balanced dorsiflexion. Assessments were made with subjects sitting and, after optimal ankle elevation was achieved, walking with stimulation. The listed timeframe is 7 months. The registry record does not clarify how the sitting and walking assessments were combined or whether one setting determined the primary analysis.

The outcome is recorded as a mean with standard deviation and as a continuous measure in the registry. However, its description emphasizes counts across ordered categories on a five-point scale. A mean can provide a compact summary, but it may conceal how observations are distributed across categories. The record does not report the category counts, mean, standard deviation, or a comparison estimate, so the endpoint’s observed results and precision are not available in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary measure as a mean of a continuous outcome, with standard deviation as the measure of dispersion. In general, a mean summarizes the central location of observations, while a standard deviation describes their spread around that mean. These summaries are most straightforward to interpret when the measurement scale supports meaningful numerical distances between values.

Here, the outcome description is based on five ordered movement categories, from inverted to everted dorsiflexion, with neutral dorsiflexion as a category. The categories have an order, but the registry record does not establish that the difference between each adjacent category represents an equal change in movement. In general, summarizing ordered categories with a mean treats the category coding as though its numerical spacing carries meaning. A mean can be useful as a compact summary, but it may not show whether observations cluster near neutral or are spread across more extreme categories. Reporting category counts alongside a mean can help readers understand the pattern; the category counts are not reported in the registry record.

A standard deviation is not the same as a confidence interval. In general, a confidence interval describes uncertainty around an estimated quantity, whereas a standard deviation describes variation among observations. Confidence intervals can help readers judge the precision of an estimated contrast. No confidence interval or other uncertainty measure for the primary comparison is reported in the registry record, so the precision of the comparison cannot be assessed.

The study description involves observations with both electrode types in a single-group study. In general, a within-person comparison can account for stable differences between people when the analysis uses paired observations appropriately. It can also be affected by changes over time, sequence, or conditions of measurement. The record does not report the statistical method used to account for the repeated assessments, nor does it describe randomizing electrode order. It is therefore not possible to determine from the registry how the data structure was handled in the analysis.

The description also outlines an evaluation of four dual-channel configurations in the first 20 subjects, followed by additional evaluation of a configuration judged to have an advantage. In general, selecting a configuration based on observed results and then evaluating it can affect how an apparent advantage should be interpreted. Prespecification, independent confirmation, and methods for accounting for selection can matter. The criteria and statistical handling of this process are not reported in the registry record.

Multiplicity refers generally to the increased chance of finding an apparently notable result when several outcomes, comparisons, or configurations are assessed. This study description includes multiple configurations, a primary movement outcome, and a listed satisfaction-related secondary outcome. The record does not report whether the analysis plan specified a primary comparison among configurations or adjusted for multiple testing. No conclusion about the presence or absence of a multiplicity adjustment can be drawn beyond noting that its handling is not reported in the registry record.

The sample-size assumptions listed for planning illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; they describe detecting a stated fraction of an observed effect. These are planning assumptions, not evidence about the trial’s own design or an observed power calculation. They also do not match the registry’s single-group classification and described electrode sequence as a like-for-like randomized two-arm comparison. The registry record does not report the trial’s own sample-size justification or numerical planning results. Any sample-size illustrations should therefore be read as hypothetical planning information, not as observed findings or proof that the study was adequately powered.

Recalculation from summary statistics would require posted outcome summaries, such as group or paired estimates and measures of variation. Those numerical primary-outcome summaries are not reported in the registry record. No recalculated estimate or precision measure can therefore be interpreted from this record. More generally, a recalculation from summary statistics would be an unadjusted analysis and would not replace a sponsor’s prespecified analysis if one were reported.

Finally, the listed outcome measure and its description leave some analytical details unclear. The record does not report how sitting and walking assessments were combined, how the clinician’s ordinal ratings were entered into the analysis, how incomplete assessments were handled, or which analysis population was used. Without those details and the outcome results, statistical interpretation must remain focused on the study design and the limits of what the registry record reports.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Functional Electrical Stimulation")
n   <- c(70)
m   <- c(3.63)
sp  <- c(0.85)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Functional Electrical Stimulation  70  3.630  0.850  3.427  3.833

11. Multiplicity, Missing Data and Analysis Populations

The study description involves more than one assessment of interest: the primary ankle-movement outcome and a satisfaction-related secondary outcome. It also describes four dual-channel configurations in the first 20 subjects, with a configuration judged advantageous to be evaluated in 50 additional subjects. Considering multiple outcomes or configurations can raise multiplicity concerns because repeated opportunities to identify a difference can affect the interpretation of statistical evidence. The registry record does not report a prespecified testing hierarchy, adjustment for multiple comparisons, or criteria for choosing the configuration.

Missing-data handling is not reported in the registry record. The record does not say how incomplete movement assessments, questionnaire responses, or missed visits were treated, or whether any imputation method was used. Enrollment is reported as 70, but the number contributing to each endpoint and the reasons for any unavailable outcome data are not reported.

The record classifies the study as single-group and does not describe a randomized allocation. It does not identify an analysis population, such as all enrolled subjects or those with complete paired assessments. The number of subjects included in the primary analysis and the handling of subjects who may not have completed both electrode assessments are not reported. These omissions limit assessment of whether the analyzed observations represent the enrolled study population.

12. Safety Results

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

Other (non-serious) adverse events

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

The registry lists zero serious adverse events and zero other adverse events in the functional electrical stimulation group, with 70 at risk for each category. These figures describe the events recorded in the registry; they are not a detailed account of event types, timing, severity beyond the serious-versus-other classification, or relatedness to stimulation.

The deaths entry is not populated, so deaths are not reported in the registry record. The record also does not explain the duration or completeness of safety follow-up, whether all enrolled subjects contributed safety information, or how events were collected. A zero count in the posted record should therefore be read as a reported count, not as proof that no event could have occurred or that all possible harms were assessed. The registry does not provide enough detail to assess the comparative safety of the two electrode approaches.

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

The record establishes that a completed study evaluated functional electrical stimulation using a single-channel QFE and a dual-channel segmented electrode in people with foot drop due to an upper motor neuron lesion. It describes an ankle-movement rating and a plan to record subject preference. It also lists safety counts for the functional electrical stimulation group.

It does not report the primary outcome values, the distribution of ratings, or a numerical comparison between electrodes. It also does not report the satisfaction questionnaire results. The registry therefore does not establish whether ankle movement was better, worse, or similar with either electrode, nor does it show how precise any observed comparison was. The title’s “as good as or better” wording should not be interpreted as a demonstrated result.

Even if outcome differences were available, this single-group study description does not identify a randomized control comparison. The electrode assessments are described in sequence, and the record does not say that the sequence was randomized. Without more detail, potential influences of order or assessment conditions cannot be evaluated. The record also does not report a formal equivalence or non-inferiority margin, so it cannot support such a conclusion based on its title alone.

The safety counts should be interpreted narrowly as registry-recorded events in the named group. They do not, by themselves, establish comparative safety or rule out events that were not recorded or reported. More complete outcome, analysis, and follow-up information would be needed for a broader assessment. The appropriate conclusion from the registry record is that the study question and measurement approach are described, while the results needed to judge the comparative endpoint are not reported.

14. Why This Trial Matters Statistically

This trial is statistically notable because the registry describes a clinically direct comparison of two electrode configurations but classifies the study as single-group. The protocol description places the QFE assessment before the segmented-electrode assessment. This makes the distinction between a comparison of recorded measurements and a randomized treatment comparison important: the registry does not describe randomized order or a separate control group.

The endpoint also raises a measurement question. Clinicians recorded movement across ordered categories on a five-point scale, while the registry identifies the outcome as continuous and summarizes it using a mean and standard deviation. In general, ordinal categories can be summarized numerically, but readers need to understand how category spacing and distribution affect interpretation. Category counts and an explanation of the analysis would make the measurement easier to evaluate; neither is reported in the registry record.

The configuration-selection process adds another statistical consideration. The description says an advantageous configuration from an initial evaluation would proceed to additional evaluation. How that choice was made, whether it was prespecified, and how any multiple comparisons were handled are not reported. These details matter because results used to select a configuration are not automatically equivalent to an independent confirmation of its performance.

Finally, the registry provides the endpoint description but not its numerical results or uncertainty. Without estimates and precision measures, the central clinical comparison cannot be assessed. This illustrates why a clearly stated question and outcome are not sufficient for interpretation: the analysis population, methods, results, and limitations are also needed.

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 main limitation for interpreting this record is the absence of numerical primary and secondary outcome results. The movement category counts, mean, standard deviation, comparison estimate, and uncertainty are not reported in the registry record. The satisfaction outcome is listed, but its results are also not reported.

The design description does not include randomized order or a separate control arm. It describes use of the QFE followed by the segmented electrode, but the registry does not report whether order effects or other changes between assessments were considered. It also does not clarify how assessments in sitting and during gait contributed to the primary endpoint.

The outcome is described as an ordered five-point clinical rating, while the registry labels it a continuous measure and specifies a mean and standard deviation. The record does not report category-level results or explain the statistical treatment of the ordered scale. The configuration-selection criteria and any multiplicity strategy are also not reported.

Further limitations include unreported missing-data procedures, analysis populations, sample-size justification, and statistical analysis methods. The registry does not explain safety follow-up completeness or provide details of event collection. These omissions prevent assessment of the precision, robustness, and generalizability of the findings; they do not establish that a particular methodological problem occurred.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Evaluation of Dual Channel vs. Single Channel FES for Dropfoot — NCT02494323.
• Registry record last updated 2016-08-03; status last verified 2015-02.
• Results first posted 2016-04-01.
• 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

NCT02494323 is a completed single-group study of functional electrical stimulation for dropfoot, sponsored by Bioness Neuromodulation. The registry reports enrollment of 70 and describes assessments using the single-channel QFE and dual-channel segmented electrode.

The primary outcome concerns ankle movement on a five-point scale, assessed in sitting and during walking. A Benefit Satisfaction Willingness to Continue questionnaire is listed as a secondary outcome. The registry reports zero serious adverse events and zero other adverse events among 70 at risk; deaths are not reported.

Numerical primary and secondary outcome results, statistical estimates, analysis methods, missing-data procedures, and the configuration-selection criteria are not reported in the registry record. The record describes the study question and design, but does not provide the results needed to determine the comparative ankle-movement findings.