This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Comparative Performance of Dynamic Elastic Response Feet (NCT02542761), a non-randomized na study. The primary outcome is Peak Ankle Dorsiflexion During Stance.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02542761 |
| Phase | NA |
| Condition | Transtibial Amputation - Unilateral |
| Allocation | Non-Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 10 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Mayo Clinic |
| Results posted | Yes |
2. Clinical Question
Population
Individuals with unilateral transtibial amputation. The registry record lists an enrollment of 10.
Intervention
A fiberglass composite prosthetic foot, studied after an acclimation period.
Comparator
A carbon fiber composite prosthetic foot, studied after an acclimation period.
Primary question
How does peak ankle dorsiflexion during stance compare between the two foot designs after an approximate 4 week acclimation period?
The study was designed to compare functional performance when participants used two prosthetic foot designs. The primary measure was peak ankle dorsiflexion during stance, reported in degrees. The registry describes this as the peak backward flexion or bending of the ankle while walking.
The crossover structure means that participants were studied using both foot designs, in one of two listed sequences: carbon fiber first and fiberglass second, or fiberglass first and carbon fiber second. Thus, the clinical question is a comparison of measurements within a study in which people experienced both designs, rather than a comparison of two independently assigned parallel groups.
The registry record does not report the primary outcome values, the estimated difference between foot designs, or an uncertainty interval. It therefore does not establish the direction or size of any observed difference. The question can be identified from the registered endpoint, but the posted record does not contain the outcome results needed to answer it statistically.
3. Trial Design
This completed study is registered as NCT02542761 and is sponsored by Mayo Clinic. The registry lists a start of 2015-06 and a primary completion of 2015-12. Its enrollment is 10, and the condition is unilateral transtibial amputation.
The design is recorded as a nonrandomized crossover with no masking. Participants used both a carbon fiber composite foot and a fiberglass composite foot. One sequence studied the carbon fiber foot first and the fiberglass foot second; the other sequence reversed that order. The arm descriptions state that each foot was studied after an acclimation period of 4 weeks. The primary outcome timeframe is described as after an approximate 4 week acclimation period.
Because the comparison is crossover, each participant’s measurements could contribute information about both designs. The record’s count of 10 at risk for each foot should not be read as evidence that there were two separate groups of 10 participants. The registry does not state how many participants followed each sequence, how sequence assignment was made, or whether all enrolled participants completed both periods.
Nonrandomized allocation and no masking are important features for interpreting the comparison. The record does not describe procedures intended to conceal the foot design or to randomly determine sequence. It also does not report whether the analysis accounted for within-participant pairing, sequence, or period effects. Those details are not reported in the registry record, so the registered design can be described, but the specific implementation and analysis cannot be reconstructed.
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.
Acclimation Period 1
| Stage | CFPF First, Then FPF | FPF First, Then CFPF |
|---|---|---|
| STARTED | 5 | 5 |
| COMPLETED | 5 | 5 |
| NOT COMPLETED | 0 | 0 |
First Intervention
| Stage | CFPF First, Then FPF | FPF First, Then CFPF |
|---|---|---|
| STARTED | 5 | 5 |
| COMPLETED | 5 | 5 |
| NOT COMPLETED | 0 | 0 |
Acclimation Period 2
| Stage | CFPF First, Then FPF | FPF First, Then CFPF |
|---|---|---|
| STARTED | 5 | 5 |
| COMPLETED | 5 | 5 |
| NOT COMPLETED | 0 | 0 |
Second Intervention
| Stage | CFPF First, Then FPF | FPF First, Then CFPF |
|---|---|---|
| STARTED | 5 | 5 |
| COMPLETED | 5 | 5 |
| NOT COMPLETED | 0 | 0 |
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.
| Characteristic | Unit | Entire Study Population |
|---|---|---|
| Participants analysed | 10 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 10 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age, Continuous | years | 49 (SD 9) |
| Sex: Female, Male: Female | Participants | 0 |
| Sex: Female, Male: Male | Participants | 10 |
| Region of Enrollment: United States | Participants | 10 |
| Body Mass Index (BMI) | kg/m^2 | 29 (SD 7) |
6. Primary Endpoint
The registry lists the primary outcome as Peak Ankle Dorsiflexion During Stance, measured over After approximate 4 week acclimation period.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | degrees |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is peak ankle dorsiflexion during stance, measured in degrees after an approximate 4 week acclimation period. Dorsiflexion describes upward or backward bending at the ankle; in this study, the registry defines the peak as the greatest such movement while walking. The endpoint is continuous, and the registry specifies that it is to be summarized as a mean with a standard deviation.
A peak value focuses on the greatest ankle movement during the stance portion of walking, rather than an average across all points in the walking cycle. Comparing this measure across foot designs is one way to assess a biomechanical aspect of functional performance. It is a specific measurement, however, and does not by itself describe every aspect of walking or the overall experience of using a prosthetic foot.
The registry also lists secondary outcomes: peak ankle plantar flexor moment during stance, peak ankle power generation, peak knee flexion during swing, time of peak knee flexion during swing, and patient satisfaction measured by the Prosthesis Evaluation Questionnaire. These outcomes represent other biomechanical or patient-reported aspects of performance. The registry record does not report numerical results for the primary endpoint or the secondary outcomes, so their observed values and comparisons are not available in the record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a focused comparison of two prosthetic foot designs in a small crossover study, but it does not report the outcome estimates needed to interpret the primary comparison. In particular, it provides no mean or standard deviation for peak ankle dorsiflexion under either foot, no estimated contrast between designs, and no confidence interval or p-value. The direction, magnitude, and statistical precision of the primary result are therefore not reported in the registry record.
The study status is completed, but completion does not itself supply evidence about the outcome. The record lists 10 enrolled participants and six outcome measures, yet it has no analysis entries. That absence means the registry record does not present an analysis result; it does not establish whether analyses were performed outside the registry or whether all enrolled participants contributed usable observations.
The crossover design offers a framework for comparing each participant under both foot conditions. In general, paired comparisons can account for stable differences between participants because each person serves as their own comparator. This benefit depends on having measurements from both periods and using an analysis suited to the design. The registry record does not report the analysis method, the number of paired observations, or how incomplete pairs were handled. It is therefore not possible to determine whether the posted comparison used the design’s paired structure.
There are also design features that affect how confidently a comparison could be interpreted. Allocation is recorded as nonrandomized, and masking is recorded as none. Differences between sequence groups or expectations about the foot design could potentially influence measurements or reporting. These are general considerations for such designs, not evidence that bias occurred in this study. The record does not describe sequence assignment procedures or steps to reduce such influences.
The listed endpoint is a biomechanical measure, not a complete account of prosthetic performance. Other registered outcomes address additional movement characteristics and patient satisfaction, but their results are also not reported in the registry record. No conclusions about the overall comparison, participant experience, or clinical importance can be drawn from the outcome information posted in the record. The defensible interpretation is limited to the registered question, design, and available safety counts, with the primary result itself unavailable.
9. Statistical Methods Explained
The registered primary measure is continuous: peak ankle dorsiflexion during stance in degrees. The registry specifies a mean and standard deviation as its descriptive summary. These statistics would describe the center of the observed measurements and their spread. They are not present for either foot in the registry record, so no numerical summary or comparison can be interpreted.
What does a mean and standard deviation describe?
In general, a mean is an average that summarizes the location of a set of measurements. A standard deviation describes how dispersed measurements are around that mean. Together, they give a basic account of the measured values, but they do not show the full shape of a distribution or identify unusual observations. Their usefulness depends on having observed values and knowing how many participants contributed. Those outcome details are not reported in the registry record.
Why does the crossover structure matter?
In general, a crossover comparison observes participants under more than one condition. Measurements from the same person are related, so a method that treats each foot-period observation as independent may fail to reflect that relationship. A paired analysis instead focuses on within-person contrasts, when complete paired observations are available. This can reduce the influence of stable differences between people. The registry identifies two treatment sequences, but it does not report the analysis method, paired data, or sequence-specific results. It is not possible to determine how the comparison was analyzed.
Crossover studies can also be affected by period and order. In general, measurements may differ between study periods for reasons unrelated to the foot design, and the experience in one period could potentially affect a later period. The registry describes an acclimation period of 4 weeks before each foot was studied, but it does not report a washout period, an assessment of carryover, or a statistical adjustment for period or sequence. Their use or absence is not reported in the registry record.
What would an uncertainty interval add?
In general, a confidence interval gives a range of values compatible with the observed data under a specified statistical procedure. It communicates precision as well as the estimated contrast: a narrower interval indicates greater precision than a wider interval, while the interval’s location describes which differences remain compatible with the data. A confidence interval is not reported for the primary outcome. Neither the size nor precision of the comparison can therefore be assessed from the registry record.
How should a p-value be read?
In general, a p-value describes how unusual data at least as incompatible with a specified null model would be, if that model and the test assumptions were correct. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of a difference. The registry record does not report a p-value or identify a statistical test for the primary outcome. No significance conclusion is available from the posted record.
What can planning calculations show?
Planning illustrations are distinct from trial results. The stated illustration assumptions use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. Such calculations are planning aids, not observed power and not evidence that the study was designed with those assumptions. The registry record does not report a sample-size justification or state that these illustration assumptions were the trial’s design assumptions. Because the primary effect estimate is not reported, the planning illustrations cannot be interpreted as a substitute for the missing outcome results.
More generally, power calculations depend on assumptions about the effect, variability, allocation, and analysis. In a crossover design, the relationship between measurements from the same participant is also relevant to planning. The registry record does not report a protocol-based sample-size calculation or the assumptions used to choose enrollment. The enrollment of 10 is recorded, but its statistical justification is not reported in the registry record.
Why might over-dispersion matter?
In general, over-dispersion refers to greater variability in data than a statistical model expects. It can make standard errors too small and uncertainty appear narrower if the model does not accommodate the extra variability. It is most directly relevant to outcome types and models in which variability is constrained by an assumed distribution; the primary measure is continuous and summarized by a mean and standard deviation. The registry does not report a model or evidence of over-dispersion, so this is a general statistical consideration rather than a finding about this study.
Overall, the registry gives the endpoint type and descriptive summary, but not the statistical test, model, estimate, or uncertainty. Any fuller methodological assessment would require analysis details that are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome and five secondary outcomes, for six outcome measures in total. Considering multiple outcomes raises a general multiplicity issue: the more comparisons or tests that are examined, the greater the chance that at least one result may appear notable by chance if each is interpreted without accounting for the collection of tests. Statistical approaches can define a primary comparison, adjust for multiple testing, or otherwise describe how secondary findings are to be interpreted. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or adjustment procedures.
The record lists no analysis entries. It does not report how missing measurements were handled, whether outcomes were analyzed for all enrolled participants or for a subset, or how many participants completed each study period. Those details are not reported in the registry record. The record also does not identify an analysis population or provide reasons for any unavailable measurements.
These gaps matter particularly for a crossover comparison. If a participant has a measurement for only one foot, a complete within-person comparison may not be available. In general, choices about including incomplete observations can affect both the estimate and its precision. No conclusion about the amount or handling of missing data can be drawn from the registered information.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Carbon Fiber Prosthetic Foot (CFPF) | 0 | 10 | 0.0% |
| Fiberglass Prosthetic Foot (FPF) | 0 | 10 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Carbon Fiber Prosthetic Foot (CFPF) | 0 of 10 |
| Fiberglass Prosthetic Foot (FPF) | 0 of 10 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Carbon Fiber Prosthetic Foot (CFPF) | 0 of 10 |
| Fiberglass Prosthetic Foot (FPF) | 0 of 10 |
The registry lists zero serious adverse events among 10 at risk for the carbon fiber prosthetic foot and zero among 10 at risk for the fiberglass prosthetic foot. It also lists zero other adverse events among 10 at risk for each foot, and zero deaths in both groups. No serious adverse event terms are listed.
These are the counts recorded for each foot condition. Because the design is crossover, the at-risk count for each foot should not be interpreted as two distinct sets of participants; the registry lists 10 enrolled participants overall. The record does not provide further detail about the duration or completeness of safety observation, or about how adverse events were collected.
Zero events in the registry does not establish that no events occurred outside the reported observation or that either design is free of risk. It describes only the counts posted in the record. With no event terms or additional safety information reported, the safety findings should be read narrowly as the recorded counts rather than as a broad assessment.
12. What the Result Does, and Does Not, Mean
The available registry information establishes what the study set out to compare: peak ankle dorsiflexion during stance after acclimation to a carbon fiber or fiberglass composite foot. It also establishes that the study was completed, enrolled 10 participants, used a nonrandomized crossover design, and had no masking. The primary outcome result itself is not reported in the registry record.
Accordingly, the record does not show whether peak ankle dorsiflexion was higher, lower, or similar under either foot design. It does not give an estimate of the size of a difference, its precision, or a statistical test. The missing result cannot be interpreted as evidence of no difference, just as study completion cannot be treated as evidence of a particular outcome.
Even if an outcome estimate were available, the endpoint would address a specific movement measurement rather than every dimension of prosthetic function. The registry also names ankle moment, ankle power, knee movement, and patient satisfaction as secondary outcomes, but does not report their findings. A single biomechanical measure would not, by itself, summarize those distinct outcomes.
In general, clinical interpretation depends on the observed effect, its uncertainty, the measurement context, and the relevance of the outcome to the question being asked. Here, the registry record does not include the observed effect or uncertainty for the primary endpoint. It therefore supports a description of the study question and design, but not a conclusion about the comparative performance of the two feet.
13. Why This Trial Matters Statistically
This study illustrates why design labels and outcome reporting both matter in clinical statistics. A crossover design can make within-person comparisons possible, while a nonrandomized sequence and absence of masking raise considerations about order and expectations. Understanding the design is necessary for interpreting what a comparison could represent; seeing its estimated result and uncertainty is necessary for interpreting what the study observed.
The registry defines a concrete continuous endpoint and specifies a mean and standard deviation, but no outcome analyses are listed. That distinction is important: an endpoint description tells readers what was intended to be measured, not what the measurements showed. A completed status and an enrollment count cannot replace estimates, uncertainty intervals, or an account of the analysis.
The study also makes clear that functional performance is represented by more than one kind of measure. The listed secondary outcomes include movement measures and patient satisfaction. In general, multiple outcomes can provide different perspectives, but they also require clarity about which comparisons are primary and how multiplicity is handled. Such a plan is not reported in the registry record.
For biostatisticians and clinical researchers, the practical lesson is to distinguish the registered question from the evidence needed to answer it. A clear design description is useful, but without the outcome summaries, analysis details, and missing-data information, the strength and precision of the comparison cannot be assessed.
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 primary limitation for interpretation is that the registry record does not report outcome values or analyses. Although the primary endpoint and its intended summary are identified, there is no mean, standard deviation, effect estimate, confidence interval, or p-value. The results for the secondary outcomes are also not reported in the registry record.
The enrollment is 10. The registry does not report how many participants completed both periods or contributed to each outcome, nor how many followed each sequence. It does not describe missing observations or their handling. As a result, the analyzed sample and the completeness of paired comparisons cannot be established from the record.
The design is nonrandomized and unmasked. The registry does not describe how participants were allocated to sequence or whether steps were taken to limit potential order or expectation effects. It identifies an acclimation period of 4 weeks for each foot, but does not report further details about period effects, carryover, or analysis adjustments.
The record does not report a statistical analysis plan, a sample-size justification, a multiplicity approach, or an analysis population. These omissions prevent a detailed assessment of whether the analysis matched the crossover design and how uncertainty or multiple outcomes were handled. They are limitations of the information available in the registry record; they do not establish what procedures may have been used outside it.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Comparative Performance of Dynamic Elastic Response Feet — NCT02542761.
- Registry record last updated 2018-09-20; status last verified 2018-08.
- Results first posted 2017-09-08.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
NCT02542761 is a completed Mayo Clinic study of carbon fiber and fiberglass composite prosthetic feet in individuals with unilateral transtibial amputation. The registry lists enrollment of 10 and a nonrandomized, unmasked crossover design with two possible foot sequences and an acclimation period of 4 weeks before each foot was studied.
The primary endpoint is peak ankle dorsiflexion during stance, in degrees, summarized as a mean and standard deviation. Five secondary outcomes are listed. The registry record does not report outcome values or analyses. It lists zero serious adverse events, zero other adverse events, and zero deaths for each foot condition. The analysis method, missing-data handling, and sample-size justification are not reported in the registry record.