Reducing Asymmetry During Gait Using the TPAD (Tethered Pelvic Assist Device) for Stroke Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Reducing Asymmetry During Gait Using the TPAD (Tethered Pelvic Assist Device) for Stroke Patients (NCT03203291), a na na study. The primary outcome is Force Symmetry Ratio During Gait.

2. Clinical Question

This is a feasibility pilot rather than a controlled test of comparative effectiveness. Its clinical question therefore has two parts: whether participants can take part in the training as intended, and whether measurements of gait symmetry warrant further study. The registry describes the intended aims, but does not report numerical findings for treatment tolerance, adherence, gait symmetry, or the other listed outcomes. Consequently, the record does not establish how participants’ measurements changed or how consistently they completed training.

3. Trial Design

The registry describes a non-randomized, single-group pilot study involving 12 participants with stroke. The study is listed as completed, with phase and allocation marked NA and masking marked none. There is no randomized assignment or parallel control group in the record. Accordingly, observations before and after training can describe change over time in the enrolled group, but cannot by themselves separate an intervention-associated change from other influences that may affect repeated measurements.

The planned schedule included three assessments within a one-week period before intervention. TPAD and overground training were planned during week 2, across 5 consecutive weekday visits. Participants were also to complete short walks before and after intervention using an instrumented system that records walking characteristics. A final walking and balance assessment was planned for one-week after intervention. Each study visit was described as approximately 1-1.5 hours, with total participation intended to be completed within three weeks.

The intervention is named as the Tethered Pelvic Assist Device treatment. The registry says all participants would receive 5 consecutive days of training, with testing before training, on completion, and at a 1-week follow-up. This schedule gives repeated observations around the intervention, but the registry does not report a control condition or a randomized sequence.

The registry lists 7 outcome measures, including force symmetry ratio during gait as the primary outcome. Named secondary outcomes include stride-length symmetry ratio, gait velocity, symmetry of the percentage of time in swing phase, time spent in double support, and the Berg Balance Scale. The planned study was intended to assess feasibility and preliminary efficacy; the registry record does not report the protocol’s sample-size justification, detailed statistical analysis plan, or numerical outcome findings.

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:

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 Force Symmetry Ratio During Gait, measured over Baseline through day 5.

The primary endpoint is the force symmetry ratio during gait. It is described as a ratio from 0-1 comparing impulse force from the affected limb with impulse force from the unaffected limb. A value of 1 represents equivalent performance by the limbs; values closer to 0 indicate greater disparity between them. The recorded summary measure is a mean with standard deviation, and the stated timeframe is baseline through day 5.

This measure is relevant to the study’s stated focus on load asymmetry. A ratio gives a compact way to represent the balance of force between limbs during walking, while repeated measurements can describe how the ratio varies over the intervention period. The direction of the scale matters for interpretation: movement toward 1 corresponds to greater symmetry according to the registry’s definition. The measure is not itself a direct assessment of every aspect of walking ability, and the registry lists other gait and balance outcomes separately.

In general, a mean describes the group’s average measurement, while a standard deviation describes how dispersed individual measurements are around that average. Those summaries can help characterize the enrolled participants, but they do not by themselves establish the precision of a treatment effect or whether an observed change is attributable to the intervention. Numerical means, standard deviations, changes, and uncertainty estimates for this endpoint are not reported in the registry record. Therefore, the endpoint’s definition is available, but the size and precision of any observed change cannot be assessed from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the reported endpoint summarize? The primary endpoint is a continuous measure: the force symmetry ratio during gait. The registry specifies a mean and standard deviation as its summary format. In general, a mean locates the center of a group’s measurements, while the standard deviation describes how much individual measurements vary around that center. Neither quantity alone describes the uncertainty in a mean or in a change between assessment times. Numerical summaries for the primary endpoint are not reported in the registry record.

The ratio’s stated range and interpretation provide a directional reference. The registry defines 1 as equivalent impulse force between the affected and unaffected limbs, and says greater disparity is represented by values closer to 0. This makes the scale interpretable in terms of symmetry, but a scale definition is not an outcome result. Without the observed values at baseline and subsequent assessments, neither the group’s starting level nor its pattern of change can be evaluated.

How would a change estimate be interpreted?

In general, a change estimate compares measurements taken at different times. For a single-group study, such an estimate describes the observed group’s before-and-after pattern. It does not, on its own, estimate a causal contrast with an untreated group. Natural variation, repeated testing, changes in participant behavior, and other time-related influences can contribute to a difference between assessments. These are general considerations for interpreting repeated measurements, not reported findings about this study.

The registry describes assessments before training, at completion, and at a 1-week follow-up. These times could distinguish an immediate post-training measurement from a later observation if numerical results were reported. The primary outcome’s stated timeframe is baseline through day 5. The record does not provide the numerical estimates or an analysis describing how repeated observations were combined or compared.

What would uncertainty measures add?

In general, a confidence interval expresses a range of values compatible with the data and a specified statistical procedure. It communicates precision as well as the estimated effect’s direction and size. A narrow interval indicates greater precision than a wide interval under the same method and assumptions. A p-value, in general, measures how incompatible the observed data are with a specified null model; it is not the probability that a treatment works, nor a measure of clinical importance. No confidence intervals or p-values for the trial outcomes are reported in the registry record, so these concepts cannot be applied to a numerical result for this study.

Small feasibility studies are often primarily informative about whether study procedures can be carried out and whether outcome measurement appears practicable. Their estimates can be imprecise, especially when participant numbers are limited. That general point is relevant to interpreting the enrollment of 12, but it does not provide a substitute for actual uncertainty estimates. The record does not report the study’s own sample-size justification, so the basis for choosing enrollment cannot be assessed.

How should the planning illustration be read?

The registry describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. For non-time-to-event outcomes, such calculations are expressed as participants per arm for a specified power; time-to-event calculations are described in terms of a total event count. These are planning assumptions, not evidence about what occurred in the enrolled study.

The actual study is described as single-group and non-randomized, so a two-arm planning illustration should not be read as the trial’s design or as a comparison that participants experienced. Planning values, when available, indicate the sample size associated with assumptions; they are not observed power. Numerical planning outputs are not reported in the registry record. The record also does not report enough outcome information to evaluate the observed effect underlying the illustration.

Why do distribution and measurement details matter?

In general, continuous-outcome methods can be affected by skewness, outliers, and repeated measurements on the same participant. Standard deviations describe dispersion, but they do not show the distribution’s shape. Repeated observations from one person are related, so an analysis may need to account for that dependence rather than treating every measurement as independent. The registry record does not report the specific model, distributional checks, handling of repeated measures, or sensitivity analyses used.

Over-dispersion is a general concern when observed variation is greater than a model assumes. If a method underestimates variation, its uncertainty estimates may be too small; if it allows for greater variation, estimated uncertainty can increase. This concept does not establish that over-dispersion occurred in this study. No model diagnostics or analysis details are reported in the registry record.

The registry lists several gait and balance outcomes in addition to the primary endpoint. When many outcomes or comparisons are examined, general statistical practice distinguishes a prespecified primary question from additional exploratory questions. Testing many hypotheses can increase the chance of at least one apparently unusual result, so interpretation may account for multiplicity. The registry record does not report a multiplicity procedure or a detailed plan identifying which secondary analyses were confirmatory. It also reports no analyses, so no inferential result can be assessed against such a plan.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 7 outcome measures, with force symmetry ratio during gait identified as the primary outcome and several gait and balance measures named as secondary outcomes. Considering multiple outcomes can create multiplicity: in general, the more statistical questions examined, the greater the opportunity for an apparently notable result to arise by chance. A prespecified primary outcome helps focus interpretation, while secondary outcomes may provide supporting or exploratory information. The registry record does not report a method for controlling multiplicity or a detailed analysis plan describing how the outcomes were prioritized beyond the primary designation.

Numerical outcome analyses are not reported in the registry record. It is therefore not possible to assess whether all planned outcomes were analyzed, how many comparisons were made, or whether any adjustment was used. The registry also does not report interim analyses or stopping rules; their presence or absence cannot be inferred from the posted record.

Missing-data handling is not reported in the registry record. The enrolled group is described as 12 participants, but the record does not state how many contributed data at each assessment, whether any visits or measurements were missed, or how incomplete observations were handled. The primary endpoint’s population field is blank, and the record does not describe analysis populations such as an intention-to-treat or per-protocol set. Without those details, the relationship between enrollment, follow-up, and the analyzed data cannot be evaluated.

In general, missingness can affect interpretation when participants with unavailable measurements differ from those with observed measurements. A complete-case analysis, an imputation method, and a repeated-measures model can rely on different assumptions. No such method is reported, so none should be presumed.

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.

The registry lists 12 participants at risk in the TPAD treatment group. It records 0 serious adverse events, 0 other adverse events, and 0 deaths. These are counts as posted for this group. They describe what the registry records; they do not establish that no adverse events occurred outside the categories or observation period represented in the record.

A zero count is not the same as proof that an event is impossible or that risk is absent. In general, a safety count is interpreted alongside the number of participants observed, the length and completeness of follow-up, event definitions, and how actively events were collected. The registry record does not provide further details on these elements, so the scope and sensitivity of event ascertainment cannot be evaluated.

The study’s stated feasibility aims include safety and treatment tolerance. The posted counts are relevant to that aim, but the record does not report additional measures of tolerance or a narrative description of safety findings. The counts should therefore be read as limited descriptive information, not as a comparative safety estimate. With no control group, the record also cannot compare the event experience under TPAD training with an alternative condition.

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

This registry record describes a completed pilot that enrolled 12 participants and planned TPAD-assisted training with repeated gait and balance assessments. It identifies a primary measure of force symmetry and lists additional outcomes. It also reports no recorded serious adverse events, other adverse events, or deaths among participants at risk in the treatment group. These details help characterize the study’s design and the scope of its posted safety information.

The record does not report numerical results for the primary endpoint or secondary outcomes. It therefore does not show the size, direction, or precision of any change in gait symmetry, gait velocity, balance, or the other listed measures. Nor does it report numerical feasibility findings for adherence, tolerance, or completion. The study’s objectives and expected outcomes are not substitutes for observed results.

The single-group design means that even if before-and-after changes were available, they would describe participants over time rather than establish a treatment effect relative to a control group. Without randomization or a concurrent comparator, changes cannot be cleanly separated from time-related influences or other explanations. The registry record does not provide an analysis plan that would resolve this limitation.

The sample-size illustration is described as a planning exercise, not observed power. It should not be interpreted as evidence that the study was adequately powered to detect a particular clinical effect. The record does not report the numerical planning outputs or the study’s sample-size justification.

Overall, the posted record supports a careful description of the pilot’s purpose, schedule, endpoint definition, and recorded event counts. It does not support a conclusion about whether the intervention changes gait measures or how large or reliable any such change might be. That distinction is especially important when a study’s stated aims include preliminary efficacy but numerical outcome findings are not reported.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of a feasibility-oriented, single-group design. Its structure makes clear the difference between describing a training program and estimating its effect against a comparator. Repeated assessments can characterize how measurements vary around an intervention, but without a control group they do not provide the same causal contrast as a randomized comparison. Recognizing that distinction prevents within-group change from being overstated.

The primary endpoint also illustrates why outcome definitions matter. The force symmetry ratio is defined in terms of impulse force from affected and unaffected limbs, and its scale gives a clear reference for symmetry. Such a definition aids interpretation of future numerical results. In this record, however, the definition is not accompanied by posted means, standard deviations, or uncertainty estimates. Statistical interpretation depends on both a meaningful measurement and results that show its observed distribution and precision.

The registry’s separate emphasis on safety, treatment tolerance, adherence, and preliminary outcome assessment highlights that feasibility and efficacy are different statistical questions. A pilot can be valuable for assessing study procedures and identifying measurement challenges, even when it is not designed as a definitive comparative test. But the record needs outcome reporting to establish what was observed for those aims; the stated objectives alone cannot answer them.

Finally, the planning illustration shows why design assumptions must be kept distinct from the trial that was conducted. A calculation based on equal allocation between two arms does not describe this single-group study. Planning quantities are prospective illustrations, not observed evidence or observed power. Keeping these distinctions explicit makes the available information useful without attributing results or design features that the registry does not report.

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 central limitation for statistical interpretation is that numerical outcome findings are not reported in the registry record. The primary endpoint is defined, but no group means, standard deviations, changes, confidence intervals, or tests are available. The same limitation applies to the named secondary outcomes. As a result, the magnitude and precision of any observed gait or balance change cannot be evaluated.

The study enrolled 12 participants and used a single-group, non-randomized design. Without a concurrent comparator, changes across assessments cannot isolate an intervention effect from other changes over time. Masking is listed as none, and the registry does not describe any steps to reduce measurement or assessment bias. The record does not report participant flow, the number completing each assessment, or how missing measurements were handled.

The registry does not report the study’s sample-size justification, detailed statistical methods, analysis populations, multiplicity procedures, interim analyses, or stopping rules. The planning illustration is described with two-arm assumptions, which do not match the listed single-group design; its numerical outputs are not reported. These omissions limit evaluation of whether analyses were prespecified and how estimates should be interpreted.

The posted safety counts are limited to the recorded categories and group. Details on event definitions, surveillance, and duration of safety follow-up are not reported in the registry record. Finally, the record’s description of intended outcomes cannot replace observed findings. The limitations concern what can be concluded from the registry record and should not be mistaken for evidence that an unreported analysis or procedure did or did not occur.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Reducing Asymmetry During Gait Using the TPAD (Tethered Pelvic Assist Device) for Stroke Patients — NCT03203291.
• Registry record last updated 2020-06-09; status last verified 2020-06.
• Results first posted 2019-10-28.
• 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 describes NCT03203291, a completed, non-randomized, single-group pilot study sponsored by Columbia University. It enrolled 12 participants with stroke and evaluated training using the Tethered Pelvic Assist Device alongside overground training. The planned intervention involved 5 consecutive days of training, with assessments before and after training and at a 1-week follow-up.

The primary outcome was the force symmetry ratio during gait, defined on a 0-1 scale, with 1 representing equivalent impulse force between limbs. The registry also names gait and balance secondary outcomes. It records 0 serious adverse events, 0 other adverse events, and 0 deaths among 12 participants at risk in the treatment group.

Numerical outcome results and statistical analyses are not reported in the registry record. The record therefore describes the study’s design, intended questions, outcome definitions, and posted safety counts, but does not permit assessment of outcome changes or their precision.