Cerebral Palsy: Ankle Foot Orthoses - Footwear Combinations: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cerebral Palsy: Ankle Foot Orthoses - Footwear Combinations (NCT03756571), a randomized na study. The primary outcome is Change in Baseline Gait Profile Score (GPS) at 3 Months-individual Lower Extremity Joint Kinematics.

2. Clinical Question

The primary endpoint focuses on gait kinematics rather than walking activity or participation in daily life. The registry describes GPS as a single score derived from individual joint and limb gait kinematics. A higher GPS is a worse outcome. The clinical question is therefore about change in a measure of gait-pattern deviation, not whether participants experienced a broader functional benefit.

The registry also lists secondary outcomes involving balance, mobility, physical function, pain, fatigue, pain interference, and satisfaction with orthoses or shoes. These outcomes address other aspects of function and experience, but their detailed results are not reported in the registry record. The primary comparison should be interpreted separately from those secondary questions.

3. Trial Design

The registry identifies this as a randomized, single-masked, parallel-group trial sponsored by Seattle Children's Hospital. Enrollment is listed as 21. The study is marked completed. Its recorded start date is 2018-12-17, and its primary completion date is 2020-02-28. The phase is listed as not applicable.

Participants were assigned to one of two orthotic approaches: an AFO-FC or a TSAFO. The AFO-FC arm description specifies a solid ankle AFO combined with modified footwear designed individually according to an algorithm. The TSAFO arm description specifies a solid AFO aligned with the ankle at 90 degrees and worn with regular footwear. The registry does not report further details about the randomization procedure, allocation concealment, or which parties were masked.

The primary endpoint is change in baseline Gait Profile Score at 3 months, with the timeframe described as 3 months after wearing the assigned orthotic intervention. The posted group summaries include 7 participants for the AFO-FC group and 6 for the TSAFO group for this outcome. The registry does not explain the relationship between these outcome counts and the enrollment figure, or report the analysis population used for the test.

Six secondary outcome descriptions are listed, covering balance, mobility, physical function, pain or fatigue, pain interference, and satisfaction. Although the record lists 12 outcome measures and 12 analyses, the details of the remaining measures and analyses are not reported in the registry record. Protocol details such as the planned analysis model, sample-size justification, interim analyses, and handling of deviations from assigned treatment are also 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.

Before assignment: This was a randomized cross over design where those who randomized to TSAFO group first then crossed over without a washout period to the AFOFC treatment arm after 3 months of wearing the TSAFO.

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.

Population: These are the individual children who randomized to the two comparison conditions.

6. Primary Endpoint

The registry lists the primary outcome as Change in Baseline Gait Profile Score (GPS) at 3 Months-individual Lower Extremity Joint Kinematics, measured over 3 months post wearing assigned orthotic intervention.

The primary endpoint is change in Gait Profile Score (GPS) from baseline at 3 months. The registry describes GPS as a single-number representation of the pattern of deviation, derived from the same individual joint and limb gait kinematics as the Gait Deviation Index. It ranges from 0 to 20, with a higher score indicating a worse outcome. The registry notes a published minimally clinically important difference of 1.6 for children with cerebral palsy.

A summary score can make a complex pattern of joint motion easier to describe and compare than a set of separate kinematic measurements. GPS is therefore used as an overall measure of gait-pattern deviation. It does not, by itself, describe every component of walking mechanics or directly measure walking activity, participation, pain, or satisfaction.

The endpoint is reported as a mean change with a standard deviation in each arm. The AFO-FC group had a mean change of 0.41 (standard deviation 1.95; 7 participants), and the TSAFO group had a mean change of -0.48 (standard deviation 1.47; 6 participants). The registry does not state the sign convention used to calculate change, so the direction of change should be read alongside that limitation. It also does not report an interval estimate for the between-group contrast.

The minimally clinically important difference provides context for interpreting GPS, but the registry does not report a confidence interval for the between-group result. The group summaries alone therefore do not establish how precisely the contrast is estimated in relation to that benchmark.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports a two-sided t-test for the primary continuous outcome. The test compares the group results using a framework based on means. The record does not specify which version of the t-test was used, whether adjustments were made, or whether the analysis followed a prespecified plan.

What does the t-test address?

General statistical explanation: A t-test evaluates evidence about a difference in group means relative to the variation in the data. A two-sided test considers results in either direction rather than testing only whether one group has a higher mean. Its p-value depends on the observed data and on assumptions of the chosen test. A p-value is not a measure of effect size, clinical importance, or the probability that a treatment works.

For this trial, the endpoint is change in GPS, and the reported summaries are means and standard deviations. The registry gives p = 0.36 for the two-sided test. It does not give the test statistic, degrees of freedom, exact model specification, or a confidence interval for the contrast. Those omissions limit independent assessment of the test and the precision of the comparison.

What do the standard deviations describe?

General statistical explanation: A standard deviation describes how spread out individual observations are around their group mean. It is not the same as a standard error or confidence interval. In the posted results, the standard deviations are 1.95 for AFO-FC and 1.47 for TSAFO. These values describe variation in the reported changes; they do not directly quantify uncertainty in the between-group contrast.

With a small number of observations, estimates of means and variability may be sensitive to individual values. The registry does not provide participant-level results, distributions, or diagnostic checks, so it is not possible to assess the shape of the outcome data or the influence of individual observations from the posted summaries alone. Whether the assumptions used for the reported test were checked is not reported in the registry record.

Why is a confidence interval useful?

General statistical explanation: A confidence interval gives a range of effect estimates compatible with the data under a specified method. It communicates precision and helps readers consider both the direction and magnitude of plausible effects. A p-value alone does not show that range. No confidence interval for the primary between-group result is reported in the registry record, so the precision of that contrast cannot be described from the posted analysis.

The registry notes a minimally clinically important difference of 1.6 for GPS in children with cerebral palsy. This gives a clinical reference point for the endpoint, but it does not replace an estimate and confidence interval for the between-group effect. The registry does not report a confidence interval that can be considered against that reference point.

What does over-dispersion mean in general?

General statistical explanation: Over-dispersion occurs when observed variability is greater than a statistical model expects. It can make standard errors too small and uncertainty appear less than it is if a model does not account for the extra variation. The registry reports a t-test and group standard deviations, but it does not report an over-dispersion assessment or a model for repeated measurements. There is therefore no basis in the registry record to claim that over-dispersion was present or that a correction was used.

How should planning illustrations be read?

General statistical explanation: Sample-size calculations are planning tools based on chosen assumptions and a target effect; they are not measurements of the trial's observed power. The planning illustration associated with the posted results is described as using the observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. The effect to detect is defined as a stated fraction of the observed effect. For non-time-to-event outcomes, the illustration is expressed as participants per arm. These assumptions describe the illustration, not necessarily the trial's original design. The trial's own sample-size justification is not reported in the registry record.

The record does not report a prespecified statistical analysis plan, a sample-size rationale, an interim-analysis plan, or methods for adjustment for multiple comparisons. It also does not report the analysis population, missing-data method, or whether the primary analysis was adjusted for baseline GPS. Those details should not be inferred from the t-test label or the summary statistics.

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("Ankle Foot Orthoses-Footwear Combination", "Traditional Solid Ankle AFO (TSAFO)")
n   <- c(7, 6)
m   <- c(0.41, -0.48)
sp  <- c(1.95, 1.47)
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  Ankle Foot Orthoses-Footwear Combination  7  0.410  1.950  -1.393  2.213
CARM  Traditional Solid Ankle AFO (TSAFO)  6  -0.480  1.470  -2.023  1.063

11. Analyses Reported by the Sponsor

The registry lists the primary comparison as a two-sided t-test with p = 0.36. It also reports the group means, standard deviations, and outcome counts used to describe the endpoint. These are the posted results for the sponsor's analysis in the registry record.

No separately recalculated estimate, p-value, or confidence interval for the primary contrast is reported in the registry record. Consequently, there is no independent recalculation to compare numerically with the registry test. The reported test should be read as the available inferential result, while recognizing that the record does not include the contrast estimate or its interval.

The registry does not report the test statistic, model details, or an analysis plan that would allow the method to be reconstructed fully from the posted summaries. The arm means and standard deviations describe the results, but a reader should not substitute a calculation based on rounded summaries for the sponsor's analysis. The registry record does not report a discrepancy between a sponsor analysis and a recalculation.

The reported p-value addresses the test's statistical comparison, not the clinical importance of a difference or the certainty of the result. A confidence interval and fuller analysis details would be needed to assess the precision and robustness of the contrast.

12. Multiplicity, Missing Data and Analysis Populations

The registry lists six secondary outcome descriptions, including balance, mobility, physical function, pain or fatigue, pain interference, and satisfaction with orthoses or shoes. It also lists 12 outcome measures and 12 analyses. The detailed results for the secondary outcomes are not reported in the registry record, so their estimates and uncertainty cannot be evaluated alongside the primary result.

When a study examines multiple outcomes or multiple analyses, the chance of at least one apparently notable result can increase. General statistical explanation: Multiplicity methods can control or describe that issue, but the appropriate approach depends on which outcomes were designated primary, the planned comparisons, and the analysis strategy. The registry does not report whether any multiplicity adjustment was planned or used, or how the six listed secondary outcomes relate to the full set of outcome measures and analyses.

The record does not report the number of participants assessed at each time point beyond the primary outcome counts, reasons for missing outcomes, or whether missingness differed by arm. It also does not report an imputation method, a sensitivity analysis, or how participants with incomplete measurements were handled. These aspects of missing-data management are not reported in the registry record.

The primary outcome counts are 7 for AFO-FC and 6 for TSAFO. The record does not identify the analysis population as intention-to-treat, per-protocol, or another defined population, and does not explain whether these outcome counts reflect all randomized participants with available endpoint data. A missing or non-estimable continuous two-arm comparison is also flagged in the registry record, but the record does not identify which measure that flag concerns.

Without the analysis plan and fuller participant-flow information, it is not possible to determine how multiplicity, missing data, or analysis-population choices affect the interpretation of the primary result.

13. 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 reports serious adverse events for each arm. For AFO-FC, 9 participants were listed as at risk and 0 as affected; for TSAFO, 10 were listed as at risk and 0 as affected. Deaths are reported as 0 in both groups. No serious adverse-event terms are listed.

The registry also reports other adverse events: 5 affected among 9 at risk in the AFO-FC group, and 8 affected among 10 at risk in the TSAFO group. These are the counts recorded for the respective categories. The registry does not provide further detail about the nature, timing, severity, or relatedness of the other adverse events in the registry record for this comparison.

These figures should be read as registry-reported counts, not as evidence that serious events are impossible or that an intervention is safer. The record does not explain the adverse-event collection procedures, observation windows, or definitions used. The at-risk counts also differ from the primary endpoint counts, and the reason for that difference is not reported in the registry record. No event-rate calculation or causal attribution is made.

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

The primary outcome summaries describe mean change in GPS at 3 months for the two randomized groups. The reported mean change was 0.41 for AFO-FC and -0.48 for TSAFO, with standard deviations of 1.95 and 1.47, respectively. The two-sided test reported p = 0.36. The result is evidence from this comparison, not a definitive statement about equivalence or the absence of an effect.

Statistical uncertainty and clinical importance are different questions. The registry identifies 1.6 as a published minimally clinically important difference for GPS in children with cerebral palsy. However, it does not report a confidence interval for the between-group contrast. The available summaries therefore do not show the range of contrasts compatible with the data or whether that range includes effects that would be clinically important.

GPS is a gait-kinematics measure. A change in this score does not by itself establish a change in walking activity, participation, balance, pain, or satisfaction. Those topics appear among the secondary outcomes, but their results are not reported in the registry record. The record also does not specify the sign convention for change, which limits interpretation of whether a positive or negative mean change represents improvement.

The trial's randomized design supports a comparison between the assigned approaches, but the registry does not report enough detail to assess the analysis population, missing-data handling, or the precision of the primary contrast fully. The posted p-value should not be interpreted as the probability that either approach is effective, nor as proof that the groups have the same outcome.

In short, the registry reports group-level GPS changes and a two-sided test, but not a confidence interval or a complete account of the analysis. The result alone does not establish a clinically meaningful advantage, equivalence, or a broader functional effect.

15. Why This Trial Matters Statistically

This trial raises a statistical question that is common in rehabilitation research: how should a complex movement pattern be condensed into an endpoint that can be compared between groups? GPS offers a single-number summary based on joint and limb gait kinematics. That makes a group comparison possible, but it also means that the score cannot describe every component of walking mechanics or daily function.

The trial compares two approaches that differ in both orthotic alignment and footwear. The registry describes the AFO-FC as individually designed and the TSAFO as a solid AFO aligned at 90 degrees and worn with regular footwear. This makes the clinical contrast meaningful as a comparison of assigned strategies, while also limiting what the primary endpoint can isolate: the result concerns the two approaches as described, not a single footwear or alignment feature in isolation.

The posted group means and two-sided p-value illustrate why an estimate of precision matters. A test result alone does not communicate the range of plausible between-group effects. The registry's stated GPS benchmark of 1.6 gives clinical context, but without a confidence interval for the contrast, the relationship between statistical uncertainty and that benchmark remains unclear.

The record also lists outcomes beyond gait kinematics, including balance, mobility, pain-related measures, and satisfaction. Those domains can complement a gait score, but the detailed results and multiplicity approach are not reported in the registry record. The example therefore underscores the importance of a clear outcome hierarchy and transparent reporting of estimates, uncertainty, analysis populations, and missing data.

16. 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 registry record provides a limited account of the primary analysis. It reports group means, standard deviations, participant counts, and a two-sided t-test, but does not report a confidence interval or the numerical between-group contrast. It also does not give the test statistic, degrees of freedom, model specification, or analysis plan. These omissions restrict assessment of precision and independent verification.

The reported outcome counts are 7 for AFO-FC and 6 for TSAFO, while enrollment is listed as 21. The registry does not explain the relationship between these figures, describe participant flow, or give reasons for any missing primary outcome data. The analysis population and missing-data approach are not reported in the registry record.

The record does not state the sign convention used for change in GPS. Although higher GPS is described as worse, the meaning of positive and negative change depends on how change was calculated. A published minimally clinically important difference of 1.6 is noted, but the absence of a confidence interval for the between-group contrast limits evaluation against that benchmark.

Details of randomization and masking are sparse: the registry identifies the design as randomized and single-masked, but does not report the randomization procedure, allocation concealment, or who was masked. It also does not report the trial's sample-size justification, interim analyses, prespecified statistical plan, multiplicity handling, or baseline adjustment. The detailed results for the listed secondary outcomes are not reported in the registry record.

Finally, the safety record gives event counts but not definitions, timing, severity, relatedness, or collection methods for the other adverse events. These gaps mean that the posted summaries should be interpreted as a limited registry account rather than a complete description of trial conduct and results.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Cerebral Palsy: Ankle Foot Orthoses - Footwear Combinations — NCT03756571.
• Registry record last updated 2021-10-14; status last verified 2021-09.
• Results first posted 2021-08-24.
• 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.

20. Record Summary

NCT03756571 is a completed randomized, single-masked, parallel-group study sponsored by Seattle Children's Hospital. It enrolled 21 participants and compared an ankle-foot orthosis–footwear combination with a traditional solid ankle AFO in cerebral palsy. The primary endpoint was change in Gait Profile Score at 3 months.

The registry reports mean changes of 0.41 for AFO-FC and -0.48 for TSAFO, with standard deviations of 1.95 and 1.47, respectively. The outcome counts were 7 and 6, and the posted two-sided t-test had p = 0.36. A confidence interval for the between-group result is not reported in the registry record. The record also lists secondary outcomes and adverse-event counts, but does not report detailed secondary results or full methods for missing data and analysis populations.