Do Rocker Bottom Shoes and Ankle-Foot Orthoses Reduce Pain and Improve Mobility for Ankle Osteoarthritis Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Do Rocker Bottom Shoes and Ankle-Foot Orthoses Reduce Pain and Improve Mobility for Ankle Osteoarthritis Patients (NCT03524729), a non-randomized na study. The primary outcome is Daily Step Count (# Steps).

2. Clinical Question

3. Trial Design

The registry identifies this as a completed, non-randomized crossover study, with no masking. It lists an enrollment of 11 and a phase of NA. The study start date is 2019-01-01, and the primary completion date is 2022-06-01. The sponsor is the VA Office of Research and Development. These administrative details describe the registered study, but do not provide information about how participants were allocated to device conditions or how the crossover was conducted.

The listed devices are a rocker bottom shoe, an ankle-foot orthosis, and a standard walking shoe. The registry describes an ankle osteoarthritis group and healthy control subjects. It does not report the sequence in which participants used devices, the duration of each condition beyond the primary outcome timeframe, whether there was a washout period, or how period and carryover effects were handled. Those details matter in a crossover design because outcomes from one condition may depend on when it was used or on prior conditions.

Non-randomized allocation means the registry does not describe random assignment. Consequently, the arms should not be interpreted as though they were necessarily exchangeable groups. The registry explicitly cautions that the arms are not a like-for-like control comparison. The absence of masking also means participants and study personnel were not masked, according to the record. Whether outcome assessors were masked is not reported in the registry record.

The primary outcome is daily step count over three weeks, measured using a body-worn pedometer. The registry lists secondary outcomes covering ankle range of motion, walking speed, timed-up-and-go, physical function, device wearing, satisfaction, and preference. Although the record lists 12 outcome measures, it reports 0 analyses. Numerical outcome estimates and inferential results 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: numbers analyzed are different as there was issue with the data collection device and data were not recorded

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 Daily Step Count (# Steps), measured over Three weeks.

Daily step count is the number of steps a participant takes per day, measured in this study using a body-worn pedometer. The registry specifies a mean as the summary measure and a standard deviation as the dispersion measure, with a timeframe of three weeks. The outcome is intended to represent mobility through observed everyday activity rather than performance on a single walking test.

As a general statistical concept, the mean describes the average measured step count in a group or condition, while the standard deviation describes how spread out individual measurements are around that average. These summaries answer different questions: a mean locates the typical level, and a standard deviation conveys variability among measurements. For a repeated or crossover study, comparisons may also depend on whether the same participants contribute data under multiple conditions and how those within-person measurements are handled.

The endpoint description states that analyzed numbers differ because of an issue with the data collection device and that some data were not recorded. The registry record does not report the mean step counts, standard deviations, number analyzed by condition, or a contrast between conditions. Thus, the endpoint definition and intended summary are documented, but the observed primary outcome is not numerically available in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a crossover design mean?

As a general concept, a crossover study measures participants under more than one condition, so comparisons can potentially use measurements from the same person. This can be useful when stable characteristics of participants affect the outcome, because a person can serve as their own reference across conditions. It does not automatically remove bias. The order of conditions, changes over time, and any lingering effects from an earlier condition can influence later measurements. The registry identifies this study as a crossover but does not report the device sequence, condition durations, washout arrangements, or methods used to address period or carryover effects.

What does non-randomized allocation imply?

Random allocation is a method used to make assignment to study conditions independent of participant characteristics, on average. The registry labels allocation as non-randomized. In general, non-randomized comparisons may be affected by selection: participants may enter or experience conditions in ways related to their health, preferences, or ability to use a device. The registry also cautions that the arms are not a like-for-like control comparison. The allocation procedure and any adjustment for differences between groups are not reported in the registry record, so the extent to which such differences were addressed is unknown.

How should the mean and standard deviation be understood?

The primary outcome is continuous: daily step count. The registry specifies that it is summarized as a mean with a standard deviation. In general, the mean is an average of the measured values. The standard deviation describes the spread of observations around that average; it is not the uncertainty of the mean itself. An effect estimate comparing conditions would describe how their average step counts differ under a stated analysis. The registry record does not report the means, standard deviations, or an effect estimate, so none can be interpreted for this outcome.

What would a confidence interval add?

In general, a confidence interval communicates uncertainty around an estimated effect. A narrower interval indicates greater precision under the model used; a wider interval indicates more uncertainty. It is not a guarantee that the true effect lies in the interval, and it does not replace consideration of study design or measurement quality. No confidence interval for daily step count is reported in the registry record. Without one, readers cannot evaluate the precision of a primary-outcome comparison.

Why do missing measurements matter?

The endpoint description says that a data collection device issue meant data were not recorded and that the numbers analyzed differ. Missing step counts reduce the information available for estimating activity and may affect interpretation if missingness is related to condition, participant characteristics, or the recorded step count itself. As a general concept, missingness is often described according to whether it is unrelated to observed and unobserved values, related to observed information, or related to the unobserved value. The record does not report enough detail to characterize the mechanism. It also does not report imputation, sensitivity analyses, or analysis populations.

What role do p-values and multiplicity play?

A p-value is, in general, a measure of how incompatible observed data are with a specified null model, assuming the model and its assumptions. It is not the probability that a treatment works, nor a measure of effect size. The registry record reports no primary-outcome p-value or other inferential result. It lists 12 outcome measures and 0 analyses. It does not report a plan for selecting primary comparisons, controlling the chance of false-positive findings across multiple outcomes, or interpreting secondary analyses. With multiple possible outcomes or contrasts, a prespecified analysis plan can help distinguish planned questions from exploratory findings. The plan is not reported in the registry record.

The record includes sample-size assumptions describing 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 states that the effect to detect is a stated fraction of the observed effect, and that non-time-to-event illustrations are expressed as participants per arm. These assumptions describe an illustration rather than the trial’s own design. The registry does not report the trial’s sample-size justification, and the illustration is not observed power or evidence that the study could reliably detect a particular effect.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 12 outcome measures, including daily step count and outcomes concerning ankle motion, walking performance, physical function, and device experience. It records 0 analyses. No multiplicity strategy is reported in the registry record. In general, testing or emphasizing many outcomes and contrasts can increase the chance that at least one result appears notable by chance. A prespecified hierarchy, adjustment approach, or clear distinction between confirmatory and exploratory analyses can help readers interpret such results. The registry record does not state whether any such approach was planned.

Missing data are a specific concern for the primary outcome. The endpoint description says that an issue with the data collection device meant data were not recorded and that the numbers analyzed differ. The number analyzed under each condition, the quantity of missing data, reasons by participant or condition, and any rules for excluding records are not reported in the registry record. It also does not report whether missing values were imputed or whether sensitivity analyses assessed how missingness could affect results.

The analysis population is not reported in the registry record. For example, the record does not explain which participants or observations were included in each outcome analysis or how incomplete crossover data were handled. These omissions limit the ability to assess whether reported analyses, if any, would represent all enrolled participants or only those with usable measurements. Because numerical outcome analyses are not reported, the impact of missing data on an estimated treatment contrast cannot be evaluated.

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 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: infection (12.5%).

The registry reports adverse-event information separately for Ankle Foot Orthosis (AFO), Healthy Control Subjects, Rocker Bottom Shoe (RB), and Control (C). For AFO, 8 were at risk for serious adverse events and 0 were affected; 8 were at risk for other adverse events and 0 were affected, with 0 deaths. For Healthy Control Subjects, 1 was at risk for serious adverse events and 0 were affected; 1 was at risk for other adverse events and 0 were affected, with 0 deaths. For RB, 8 were at risk for serious adverse events and 0 were affected; 8 were at risk for other adverse events and 0 were affected, with 0 deaths. For Control (C), 8 were at risk for serious adverse events and 1 was affected; 8 were at risk for other adverse events and 0 were affected, with 0 deaths.

The registry also lists infection as the top serious adverse-event term, with 12.5%. The record does not clarify the denominator or explain how this term relates to the group-level serious-event counts. These figures should be read as registry-reported event summaries, not as a direct comparison of safety between devices. The non-randomized design and non-equivalent arms limit like-for-like comparisons, and the record does not provide further details about event definitions, timing, attribution, or follow-up.

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

The record establishes that a completed, non-randomized crossover study was registered to examine rocker bottom shoes and ankle-foot orthoses in relation to mobility among people with ankle osteoarthritis. It identifies daily step count over three weeks as the primary outcome and describes a pedometer as the measurement device. It also lists a standard walking shoe and healthy control subjects. These details clarify the intended question and the kinds of measurements considered.

However, the registry record does not report numerical results for daily step count or the listed secondary outcomes. It therefore does not show the observed average step counts, a difference between conditions, or the precision of such a difference. The device collection issue and differing analyzed numbers further mean that the enrollment figure cannot stand in for the number with usable primary-outcome data. No conclusion about the direction, magnitude, or consistency of an outcome difference can be drawn from the registry record.

The stated rationale is that rocker bottom shoes and ankle-foot orthoses may reduce ankle motion and relieve pain, potentially improving mobility. That rationale is not itself evidence that these changes occurred. The record does not report results demonstrating changes in pain, joint range of motion, walking speed, physical function, satisfaction, or preference.

Even if numerical comparisons were available, the design would require careful interpretation. The study is non-randomized and unmasked, and the registry cautions that the arms are not a like-for-like control comparison. Details needed to evaluate the crossover, missing-data methods, and statistical analyses are not reported in the registry record. The record supports an account of the registered study and its limitations, but not a claim that a device caused improvement or failed to do so.

13. Why This Trial Matters Statistically

This study raises a practical statistical question: how to evaluate a device intended to change mobility using both controlled performance measures and everyday activity. Daily step count can reflect activity outside a clinic, while outcomes such as walking speed, timed-up-and-go, and ankle range of motion characterize other aspects of function. In general, these measures address related but distinct constructs; a change in one should not automatically be treated as proof of a change in another.

The crossover design also makes the analysis structure important. When participants experience multiple conditions, the timing and order of measurements can matter, and analyses should account for within-person observations where appropriate. The registry identifies a crossover but does not report the sequence or analysis details. Its non-randomized allocation and explicit warning that arms are not like-for-like further underline why design information is necessary before attributing differences to a device.

The data collection device issue is another important lesson. A clearly defined outcome is useful only if the measurements are captured adequately and the number of usable observations is transparent. The registry notes that some daily step-count data were not recorded and that analyzed numbers differ, but does not report the numbers by condition or the missing-data approach. That limits evaluation of both the estimate and its reliability.

Finally, the record illustrates the difference between a study’s intended question and the evidence available for interpretation. It names outcomes, devices, and a rationale, but it reports 0 analyses and no numerical outcome results. For statistical interpretation, transparent estimates, uncertainty, analysis populations, and missing-data details are essential; without them, the study’s measured effects cannot be assessed from the registry record.

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.

Several limitations specific to this record constrain interpretation. The study is non-randomized and unmasked, and the registry warns that the arms are not a like-for-like control comparison. The exact assignment process and the characteristics of participants within each condition are not reported in the registry record. Consequently, the record does not establish that observed groups or conditions would be directly comparable even if outcome estimates were available.

The crossover details are incomplete. The registry does not report the order of device use, condition duration beyond the primary outcome timeframe, washout procedures, or the method used to handle repeated observations. Those details are important for assessing whether period or carryover effects could influence comparisons. The registry also does not report whether outcome assessors were masked.

Daily step-count data were affected by a collection device issue. The endpoint description says data were not recorded and analyzed numbers differ, but the number with usable data by condition and the missing-data methods are not reported in the registry record. The record also does not provide numerical outcome results, effect estimates, confidence intervals, or p-values. It lists 12 outcome measures and 0 analyses, without reporting a multiplicity plan or analysis populations.

The enrollment is 11, but the registry does not report a sample-size justification for the trial. The planning assumptions recorded for an illustration do not establish the study’s design rationale or the precision of any outcome estimate. Finally, the adverse-event summary gives group-level counts but little contextual detail about event definitions, timing, attribution, or follow-up. These omissions limit both efficacy and safety interpretation.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Do Rocker Bottom Shoes and Ankle-Foot Orthoses Reduce Pain and Improve Mobility for Ankle Osteoarthritis Patients — NCT03524729.
• Registry record last updated 2024-09-19; status last verified 2024-08.
• Results first posted 2024-09-19.
• 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 a completed, non-randomized, unmasked crossover study sponsored by the VA Office of Research and Development. It lists enrollment of 11, with a study start date of 2019-01-01 and primary completion date of 2022-06-01. The study concerns ankle osteoarthritis and healthy ankles, and lists rocker bottom shoes, ankle-foot orthoses, and standard walking shoes.

Daily step count, measured by a body-worn pedometer over three weeks, is the primary outcome. The record notes missing step-count data due to a device issue and differing analyzed numbers. It lists 12 outcome measures and 0 analyses, but numerical outcome results and details of the statistical analysis are not reported in the registry record. The record cautions that the arms are not a like-for-like control comparison.