Duration of Brace Wear in Clubfoot Treatment - A Prospective Randomized Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Duration of Brace Wear in Clubfoot Treatment - A Prospective Randomized Trial (NCT01551264), a randomized na study. The primary outcome is Kaplan-Meier Recurrence-Free Survival Probability for Clubfoot Affected Limbs.

2. Clinical Question

The registry describes a prospective, randomized, controlled comparison of bracing duration. Its stated aim is to evaluate whether a two-year or four-year bracing protocol differs in preventing recurrence during the first year after treatment, and to evaluate factors associated with recurrence. The posted primary outcome is not a simple count of people with recurrence. It is a Kaplan-Meier recurrence-free survival probability for each affected limb.

Recurrence has a clinical definition in the record: one or more listed deformities—hindfoot varus, ankle equinus, midfoot adduction, midfoot cavus, or forefoot pronation—that require repeat casting or surgical intervention. Recurrence was determined by the local Principal Investigator. The endpoint timeframe runs from the end of assigned bracing until the earliest recurrence, up to one year after bracing is discontinued, with a per-protocol visit window of 1.2 years.

The outcome population includes limbs from participants who started bracing and attended at least one visit within one year after discontinuation. Further detail in the registry record is truncated, so additional eligibility or analysis-population criteria are not reported in the registry record. The central comparison is therefore about limb-level recurrence-free survival after bracing ends, rather than recurrence over the entire period from initial correction.

3. Trial Design

This is a randomized, parallel-group trial with no masking reported. It is listed as completed and has an enrollment of 139. The sponsor is Washington University School of Medicine. The registry lists isolated clubfoot as the condition and a Foot Abduction Brace as the intervention. The trial is classified as not applicable for phase.

After correction of clubfoot using the Ponseti Method, participants were assigned to a four-year or a two-year bracing protocol. The primary outcome is measured from the end of the assigned bracing treatment, not from the start of the trial or the initial correction. The outcome timeframe extends up to one year after bracing is discontinued, with a per-protocol visit window of 1.2 years. The registry describes a multicenter trial but does not report the number or locations of participating centers in the registry record.

The reported primary outcome estimates are 0.81 for the four-year arm, with a 95% confidence interval from 0.7 to 0.95, and 0.65 for the two-year arm, with a 95% confidence interval from 0.52 to 0.8. The registry gives arm counts of 44 and 55 for this outcome. These are limb-based Kaplan-Meier estimates: bilateral participants contribute data for both affected limbs, while unilateral participants contribute one limb. They should not automatically be read as numbers of participants.

The record reports a Chi-squared analysis with p = 0.03. The test statistic, the precise comparison to which the test was applied, and further details of its implementation are not reported in the registry record. The allocation sequence, concealment procedures, protocol deviations, and detailed sample-size justification are also not reported in the registry record. Enrollment is not the same as the number contributing to each outcome estimate; the record's analysis population is narrower and is described in relation to starting bracing and attending at least one follow-up visit.

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: For patients with bilateral clubfoot, each limb was assessed. Bilateral patients contribute data for both limbs and unilateral patients contribute data for the affected limb. Analysis includes limbs from participants who started bracing and attended at least one visit within one year after discontinuing bracing.

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: Baseline participants represent the number of participants enrolled and randomized. However, participant could drop out of the study prior to starting the bracing treatment due to eligibility changes or site discontinuation.

6. Primary Endpoint

The registry lists the primary outcome as Kaplan-Meier Recurrence-Free Survival Probability for Clubfoot Affected Limbs, measured over From end of bracing treatment until the earliest recurrence up to 1 year (allowing for per-protocol visit window of 1.2 years) after the assigned treatment (2- or 4-year bracing) is discontinued..

The primary endpoint is Kaplan-Meier recurrence-free survival probability for each limb affected by clubfoot. It describes the probability that a limb remains free of a qualifying recurrence over the specified follow-up after bracing is discontinued. The analysis counts recurrence only when a listed deformity requires repeat cast application or surgical intervention. The local Principal Investigator determined whether recurrence occurred.

Time-to-event methods are used because recurrence may occur at different times and because not every limb will necessarily have a recurrence observed during the follow-up period. Kaplan-Meier estimation can account for different observed follow-up times, subject to assumptions about censoring and the analysis procedures. The registry reports the estimate and a 95% confidence interval for each arm. It does not report additional detail about censoring rules or the handling of incomplete follow-up.

The unit is the affected limb, not the participant. A participant with bilateral clubfoot contributes both limbs, whereas a participant with unilateral clubfoot contributes one. This distinction matters when reading the arm counts and when considering whether observations may be related within a participant. Whether the analysis accounted for within-participant dependence is not reported in the registry record.

The timeframe begins when assigned bracing ends and extends up to one year, allowing for a per-protocol visit window of 1.2 years. This endpoint therefore addresses recurrence after the bracing period, not recurrence during bracing or all outcomes after initial correction. The endpoint is useful for expressing the timing of recurrence-free follow-up, but its interpretation depends on the definition of recurrence, the follow-up available, and the analysis population described in the registry.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Kaplan-Meier estimation is a general method for describing time until an event, while allowing participants or other analysis units to have different observed follow-up. In this trial, the event is a qualifying recurrence in an affected limb. The estimate is framed as recurrence-free survival: the probability of remaining without the defined recurrence over time after bracing ends. The posted values are 0.81 for the four-year bracing arm and 0.65 for the two-year bracing arm.

What does a Kaplan-Meier estimate represent?

In general, Kaplan-Meier estimation uses the event times that are observed and incorporates follow-up until an event or censoring. Censoring means that the event was not observed during the available follow-up for an analysis unit. The method relies on assumptions about how censoring relates to the chance of the event. The registry does not report the detailed censoring rules, how follow-up times were handled, or how limbs without a qualifying event were treated at the end of observation. Those omissions make it impossible to fully assess the implementation from the record alone.

The primary endpoint is evaluated for each affected limb. If a participant has bilateral clubfoot, both limbs contribute; for unilateral clubfoot, the affected limb contributes. A limb-based analysis can be clinically meaningful when recurrence is defined for each limb, but the two limbs of one participant may have related outcomes. General statistical methods often need to account for such clustering when making inference. Whether this trial's analysis accounted for within-participant dependence is not reported in the registry record. This matters because a method that treats related limbs as independent may represent uncertainty differently from a method that models their relationship.

How should the confidence intervals be read?

A confidence interval is a range of values compatible with the observed data under the interval procedure and its assumptions. The four-year arm's 95% confidence interval is 0.7 to 0.95; the two-year arm's is 0.52 to 0.8. The intervals communicate uncertainty around the respective arm-specific survival estimates. They are not guarantees that a particular value is true, and they do not directly give an interval for the difference between arms. The registry does not report a confidence interval for a between-arm contrast.

Confidence intervals also depend on the analysis unit, the method used to calculate them, and assumptions about follow-up and dependence. The record names the outcome as Kaplan-Meier recurrence-free survival probability and identifies the dispersion as a 95% confidence interval, but it does not report the interval calculation method. The precision of the estimates should therefore be understood from the posted interval limits without inferring an unreported method.

What does the reported test add?

The registry lists a Chi-squared analysis and p = 0.03 for the two arms. In general, a Chi-squared test assesses compatibility between observed data and a null hypothesis under a particular test setup. The registry does not specify the exact test statistic, null hypothesis, time point or data reduction used for this analysis. Nor does it say whether the test addresses the Kaplan-Meier estimates directly or another representation of the outcome. This uncertainty prevents a more specific explanation of the test's mechanics.

A p-value is not an effect size and does not describe the probability that the result is due to chance. It is a measure derived under a null model and test assumptions. It should be interpreted with the outcome estimates and their precision, not in isolation. Because no contrast estimate or confidence interval is posted for the between-arm comparison, the magnitude and precision of that contrast cannot be described from the registry result.

Why can over-dispersion and dependence matter?

Over-dispersion is a general statistical issue in which variability in observed data exceeds what a model assumes. It can arise when observations are more heterogeneous or more dependent than the model allows. The primary outcome is limb-based, and bilateral participants contribute two limbs; this creates a possible dependence structure within participants. The registry does not report whether clustering or extra variability was assessed or handled. This is not evidence that the analysis was incorrect, but it is an important unreported detail for evaluating standard errors, confidence intervals, and tests.

The reported Chi-squared method may have been applied using a specific data structure, but the record does not provide enough information to establish that structure. A reader should not assume that the test accounts for time-to-event data, limb clustering, or censoring unless those details are reported. The p-value can be quoted as the result recorded, while its precise interpretation remains limited by the missing methodological detail.

What do planning calculations represent?

Planning calculations are design illustrations, not observed trial findings and not observed power. The registry's stated assumptions for such calculations are a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation. The effect to detect is expressed as a stated fraction of the observed effect. For time-to-event outcomes, the planning quantity is the total number of events; for other outcomes, it is participants per arm. These assumptions describe illustrative planning calculations, not necessarily the trial's original design or justification. The sample-size justification for this trial is not reported in the registry record.

In general, power planning asks how much information a future study would need to detect a specified effect under stated assumptions. It does not show that the completed trial had a particular probability of detecting an effect, and it should not be used to interpret the observed result as though it were a measured outcome. The registry record does not report the original rationale for enrollment or its assumptions in sufficient detail to evaluate that design decision.

Finally, the outcome population is described as including limbs from participants who started bracing and attended at least one visit within one year after bracing ended. The remaining population description is incomplete in the registry record. The specific handling of missing outcomes, missed visits, protocol deviations, and analysis populations is not reported. Such details can affect both survival estimation and comparisons between randomized groups.

10. Analyses Reported by the Sponsor

The registry reports the sponsor's two-group analysis as Chi-squared, with p = 0.03. No comparison effect estimate, confidence interval for the contrast, or test statistic is reported. The method is named, but its exact application to the limb-level Kaplan-Meier endpoint is not explained in the registry record.

No recalculated two-arm comparison is available for this outcome. The endpoint is classified as a count-other outcome, and values are missing or not estimable for a two-arm comparison of that type. The posted arm-specific survival estimates and their confidence intervals can be described, but they do not themselves constitute a recalculated contrast. There is therefore no independent recalculated estimate to set beside the sponsor's p-value.

The record does not flag a discrepancy between a sponsor result and a recalculation. The sponsor's reported p-value should be presented as the posted analysis, with the limitation that the exact test details and a contrast estimate are absent. It should not be supplemented with an inferred difference, ratio, or other comparison that the registry does not report.

11. Multiplicity, Missing Data and Analysis Populations

The registry posts one primary outcome measure and one reported analysis, and it lists no posted secondary outcomes. The trial's stated objective also mentions evaluating factors associated with recurrence, but the available record does not show analyses of those factors. It is not possible to determine from the posted information whether additional outcomes or analyses were planned, conducted, or omitted.

Multiplicity arises when several hypotheses or outcomes are tested, because the chance of at least one apparently notable result can increase across a set of tests. Whether any adjustment or other strategy for multiple comparisons was planned is not reported in the registry record. The record also does not report interim analyses, stopping rules, or a prespecified statistical analysis plan. Without these details, the p-value should be treated as the result of the reported analysis, not as evidence that all possible testing issues have been addressed.

The primary outcome population includes limbs from participants who started bracing and attended at least one visit within one year after bracing discontinuation. The population description ends before all eligibility criteria are stated, and further analysis-population details are not reported in the registry record. The record does not say whether the primary analysis followed intention-to-treat principles, how protocol deviations were handled, or how participants without qualifying follow-up were treated.

Missing-data methods and the amount or pattern of missing follow-up are not reported in the registry record. For a time-to-event outcome, loss of observation and censoring can affect estimates, so the assumptions and procedures matter. The registry gives a follow-up window and a visit-window allowance but does not explain rules for censoring, incomplete visits, or withdrawal. These gaps do not establish that data were missing or that the analysis was biased; they limit independent assessment of how missing information and the analysis population may affect the result.

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 5% reporting threshold.

The adverse-event figures list zero serious adverse events, zero other adverse events, and zero deaths in both groups. The serious-event and other-event at-risk counts are 70 in the four-year bracing arm and 69 in the two-year bracing arm. These are the counts recorded as at risk for the adverse-event summaries, and they should not be confused with the limb-based counts used for the primary outcome.

Zero reported events means none were recorded in these registry fields for the listed groups; it does not establish that no events occurred outside the defined recording or reporting process. The registry does not provide serious-event terms, and it does not report additional detail about event definitions, observation periods, ascertainment, or the handling of missing safety information. The at-risk counts are not the enrollment count and are not explained further in the record.

These figures are descriptive safety data. They do not provide a comparative estimate or establish equivalence between bracing durations. When event counts are zero, the record's figures alone do not quantify how precisely rare events have been excluded. The safety information should therefore be read as the reported event counts and denominators, with the limitations in definitions and follow-up noted.

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

The posted primary results describe recurrence-free survival of affected limbs after bracing was discontinued. The estimate is 0.81 in the four-year arm and 0.65 in the two-year arm, with respective 95% confidence intervals of 0.7 to 0.95 and 0.52 to 0.8. These are arm-specific Kaplan-Meier estimates over the stated post-bracing follow-up window. The registry also reports a Chi-squared p-value of 0.03 for the two groups.

These results do not provide a directly reported contrast estimate with a confidence interval. The p-value gives no standalone description of the size or precision of a difference. The exact implementation of the reported Chi-squared analysis is not reported in the registry record, so the test cannot be interpreted beyond its recorded method label and p-value. It is important to distinguish the posted analysis from an unreported recalculation or an inferred effect measure.

The endpoint applies to limbs, not simply to participants. Participants with bilateral clubfoot contribute two affected limbs, and unilateral participants contribute one. The record does not say whether within-participant dependence was accounted for. The estimates also represent outcomes after the assigned bracing period ends, and do not cover recurrence during bracing or outcomes beyond the follow-up timeframe.

The findings do not establish the result for every person with clubfoot or for settings and populations not described by the trial. The outcome analysis is limited to limbs from participants who started bracing and attended at least one visit within one year after discontinuation, as described in the registry. Further criteria, missing-data handling, and analysis-population details are not reported. Nor do the posted results answer the stated question about factors associated with recurrence, since no secondary outcomes are posted.

In general, statistical evidence should be interpreted with the endpoint definition, study design, precision, analysis assumptions, and completeness of follow-up in view. The reported estimates, confidence intervals, and p-value are the available primary results; they do not by themselves settle questions about clinical importance, mechanisms, longer-term recurrence, or unreported outcomes. No medical recommendation follows from these registry figures alone.

14. Why This Trial Matters Statistically

This trial raises a useful statistical distinction between the unit randomized and the unit analyzed. The intervention is assigned as a bracing duration, while the primary endpoint is evaluated for each affected limb. Bilateral participants contribute two limbs. This structure is common in clinical research when an outcome can occur separately on paired body parts, but it creates a question about dependence: two outcomes from one participant may be more alike than outcomes from different participants. Whether and how the analysis addressed this issue is not reported in the registry record.

The endpoint is also time-based. A recurrence-free survival estimate uses information about when recurrence occurs, rather than reducing follow-up to a simple ever/never count without regard to timing. This can make the summary relevant to the stated follow-up question, while also making censoring and follow-up rules important. The registry identifies a timeframe and a visit-window allowance, but detailed rules are not reported.

Another important statistical feature is the gap between arm-specific estimates and a reported group test. The two arm estimates have confidence intervals, while the Chi-squared result is reported without a contrast estimate or confidence interval. A test result and an effect estimate answer different questions: the former summarizes compatibility with a null model under assumptions, while the latter quantifies a contrast. Having both would make it easier to understand magnitude and uncertainty together.

Finally, the registry's outcome-specific analysis population is not identical by definition to enrollment: it includes those who started bracing and attended at least one follow-up visit. Transparent reporting of missingness, censoring, analysis populations, and handling of paired limbs is central to evaluating precision and generalizability. The record's omissions illustrate why statistical interpretation depends on more than a single p-value.

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.

Several trial-specific details needed to assess the primary result are not reported in the registry record. The detailed statistical analysis plan, original sample-size justification, interim-analysis procedures, stopping rules, allocation concealment, and protocol-deviation handling are not described. The record names a Chi-squared test but does not identify its exact implementation or give its test statistic. It also does not report a between-arm effect estimate or confidence interval.

The primary outcome is limb-based, and bilateral participants contribute two limbs. The registry does not report whether the analysis accounted for correlation between limbs belonging to the same participant. If such dependence is present, it is relevant to uncertainty estimates and hypothesis testing. The record does not establish whether or how it was handled.

The recurrence assessment was made by the local Principal Investigator, but masking was none. The record does not report further detail about outcome-assessment procedures or whether assessments were standardized across centers. The endpoint definition includes deformities requiring repeat casting or surgical intervention; the registry does not describe adjudication procedures beyond identifying the local Principal Investigator as the determiner.

Missing-data and censoring procedures are not reported. Although the endpoint timeframe and visit-window allowance are stated, the record does not explain how incomplete follow-up, missed visits, or withdrawal affected the Kaplan-Meier estimates. The outcome population description is truncated after noting that participants started bracing and attended at least one visit within one year after discontinuation, so the complete criteria cannot be assessed.

The posted record includes one primary outcome and no secondary outcomes, despite the stated objective concerning factors associated with recurrence. The absence of posted secondary results does not show whether additional analyses were planned or performed. These reporting limitations constrain evaluation of the p-value, the precision of the group comparison, and the extent to which results apply beyond the analyzed limbs and stated follow-up.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Duration of Brace Wear in Clubfoot Treatment - A Prospective Randomized Trial — NCT01551264.
• Registry record last updated 2021-11-30; status last verified 2021-11.
• Results first posted 2021-11-30.
• 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

NCT01551264 is a completed, randomized, parallel-group trial comparing two-year and four-year Foot Abduction Brace use after Ponseti correction of isolated clubfoot. The registry lists enrollment of 139 and no masking. The primary outcome is Kaplan-Meier recurrence-free survival probability for affected limbs during follow-up after bracing is discontinued.

The posted estimate is 0.81 (95% confidence interval 0.7 to 0.95) for the four-year arm and 0.65 (95% confidence interval 0.52 to 0.8) for the two-year arm. A Chi-squared analysis is reported with p = 0.03. Further details about that test and a confidence interval for the between-arm contrast are not reported in the registry record. The endpoint is limb-based, and whether the analysis accounted for paired limbs is not reported.

The adverse-event fields list zero serious events, zero other events, and zero deaths in both groups. No secondary outcomes are posted. Details of missing-data handling, the complete analysis population, and the original sample-size justification are not reported in the registry record.