Pressure Alternating Shoes: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pressure Alternating Shoes (NCT06026813), a non-randomized na study. The primary outcome is Maximum Average Pressure at Baseline With Pressure Alternating Shoes, Right Foot (Before Any Cells Were Offloaded).

2. Clinical Question

The study concerns Pressure Alternating Shoes (PAS), a device designed to change how plantar pressure is distributed during walking. The primary question is descriptive: what is the maximum average pressure in specified regions of the right foot before any insole cells are offloaded? The record also lists skin temperature and tissue oxygenation outcomes. It does not report a primary numerical result or an analysis comparing pressure before and after offloading.

3. Trial Design

The registry describes a completed study of Pressure Alternating Shoes for prevention of diabetic foot ulcers. Its listed intervention is a device test. The stated device concept is an insole with an active pressurized actuator array and a passive compliant layer over each actuator. Individual actuators can be inflated or deflated using pressurized air, with programmable control intended to cycle relief of mechanical loading. The record describes intended device operation; it does not establish a clinical effect on ulcer prevention.

The design fields identify the allocation as non-randomized, masking as none, and model as single group. Although the record describes healthy controls and patients with diabetic neuropathy, it cautions that the arms are not a like-for-like control comparison. Random assignment, a masked assessment process, and a formal comparison plan are not reported in the registry record. The presence of two described populations should therefore not be taken to establish a randomized or balanced treatment comparison.

The registry lists enrollment as 21. The recorded study start is 2024-03-07, primary completion is 2024-07-11, and overall status is completed. Phase is listed as NA. The sponsor is University of Texas Southwestern Medical Center. These administrative details do not provide information about recruitment methods, adherence, or how participants were allocated to the described groups; those details are not reported in the registry record.

The primary measure concerns right-foot plantar pressure before any cells were offloaded, over the first 40-seconds of the walk. The device description identifies seven air cells aligned with the big toe, second through fifth toes, metatarsal heads, midfoot, and heel. The registry also lists skin temperature and tissue oxygenation outcomes. The number of outcome measures is listed as 17, while the number of analyses is listed as 0. Numerical outcome findings and a statistical analysis plan 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.

Before assignment: Due to design \& device constraints, unable to randomize between left/right foot (PAS device) between subjects \& were asked to walk with daily shoes on treadmill-5 mins (Control data). Order of sessions (PAS \& Daily footwear) weren't randomized as in crossover study. After testing PAS device, daily footwear use data was collected in healthy subjects (Tier 1). Study procedures (use of PAS and daily footwear) in Tier 2- diabetic neuropathic subjects followed the same sequence as in Tier 1.

Session 1- Tier 1 Subjects(5 Mins)

Session 2-Tier 2 Subjects(5 Mins)

Analysis population for the primary outcome, as defined in the registry: Due to technical issues like unexpected stop in the interface pressure data collection during testing and insole control box not functioning properly, resulted in incomplete data collection for 4 healthy subjects and therefore not included in the analysis of this outcome measure. All successfully collected data are reported.

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 Maximum Average Pressure at Baseline With Pressure Alternating Shoes, Right Foot (Before Any Cells Were Offloaded), measured over Before any cells were offloaded (First 40-seconds of the walk).

The primary endpoint is titled maximum average pressure at baseline with Pressure Alternating Shoes, in the right foot, before any cells were offloaded. It measures pressure in plantar regions during walking; the stated timeframe is the first 40-seconds of the walk. The unit is kPa, and the endpoint is specified as a mean with standard deviation as its dispersion measure.

The insole's seven air cells correspond to the big toe, the area spanning the second through fifth toes, metatarsal heads, midfoot, and heel. The endpoint description states that measurements were obtained only from the right foot. These details define what was intended to be measured, but the registry record does not report the numerical mean, standard deviation, or region-specific values. It also does not clarify how the maximum average pressure was derived across regions or repeated observations.

As a device-focused measure, plantar pressure can describe the mechanical loading that the insole is designed to alter. In general, such a measure can help characterize device operation or pressure distribution. It is not itself a direct count of diabetic foot ulcers, and the listed primary endpoint does not measure ulcer incidence. A relationship between pressure readings and later clinical outcomes is not established by this endpoint alone.

The record reports incomplete collection for 4 healthy subjects because of technical problems, including unexpected stops in interface pressure data collection and an insole control box that did not function properly. Those subjects were not included in the analysis of this outcome measure. Further details about the remaining primary outcome analysis population are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Several statistical ideas help frame the record, but the registry does not report a complete analysis plan or numerical primary results. The distinctions below are general explanations, not claims about unreported procedures in this study.

What does a mean with standard deviation describe?

The primary endpoint is specified as a mean with standard deviation. In general, the mean describes the central level of a continuous measurement, while the standard deviation describes how spread out individual measurements are around that mean. They answer different questions: the mean is about the measured level, and the standard deviation is about variation among observations. Neither alone communicates how precisely the mean has been estimated. A confidence interval is commonly used to describe that estimation uncertainty, but no confidence interval is reported for this endpoint.

The primary measure is called maximum average pressure, which combines terms that can refer to different summaries. The record does not explain the precise calculation, such as which observations are averaged or how the maximum is selected. This matters because different aggregation rules can produce different summaries from the same underlying pressure readings. The calculation procedure is not reported in the registry record, so the exact statistical meaning beyond the endpoint description cannot be determined.

Why does the study design matter?

Randomization, when used, helps make comparison groups similar on average with respect to measured and unmeasured baseline characteristics. This study is listed as non-randomized, and the registry cautions that the described arms are not a like-for-like control comparison. Consequently, a group contrast would not automatically isolate an effect of the shoes. In general, differences in diabetes status, neuropathy, or other participant characteristics can influence physiological measurements independently of a device. The registry record does not describe a method for controlling such confounding.

Masking is listed as none. In general, lack of masking may affect behavior, measurement procedures, or decisions about data handling, depending on the outcome and study conduct. The primary outcome uses interface pressure data, but the record does not describe whether measurement staff were aware of group status, whether data processing was automated, or whether assessment procedures were standardized. These details are not reported in the registry record.

What does missingness change?

Four healthy subjects were excluded from the primary endpoint analysis because technical problems led to incomplete data collection. In general, excluding observations can reduce the available information and may introduce bias if the reason data are missing is associated with the unobserved measurement. Technical failure does not necessarily create bias, but the likely direction and magnitude depend on which records were lost and why. The registry describes the technical issues but does not report a comparison of included and excluded participants or a sensitivity analysis.

For a continuous endpoint, the analysis population and handling of missing measurements determine which observations contribute to the estimate. The remaining details of the primary outcome population are incomplete in the registry record. It does not report the number of usable measurements by region, participant-level summaries, or a missing-data method. No particular imputation, complete-case, or other procedure should be assumed.

How should planning illustrations be read?

In general, a sample-size calculation asks how much information might be needed to detect a specified effect under stated assumptions. The registry's planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a stated fraction of the observed effect. For time-to-event calculations, the stated quantity is total events using the Schoenfeld approach; other calculations are expressed as participants per arm.

These are planning illustrations based on the observed effect, not the trial's own design. They do not describe the study's actual allocation or establish that the study had a particular probability of detecting an effect. A planning sample size is not observed power. The record does not report a sample-size justification used to design the study, and no planning values or underlying observed effect values are reported in the registry record. Therefore, the assumptions can be described, but the resulting numerical illustrations and their practical implications cannot be assessed from the registry information.

Why do multiple outcomes need care?

The registry lists 17 outcome measures, including the primary pressure measure and secondary skin temperature and tissue oxygenation measures. In general, testing many outcomes can increase the chance that at least one result appears statistically notable by chance. Methods such as prespecifying a primary endpoint or adjusting for multiple comparisons may address that concern, but the registry record does not report a multiplicity strategy. The number of analyses is listed as 0, and no test results or multiplicity adjustments are recorded.

Finally, statistical significance and clinical importance are not interchangeable. In general, a small p-value does not by itself establish that a difference is important, while an imprecise estimate may leave substantial uncertainty. Here, the absence of numerical endpoint results prevents assessment of either the estimated size or its precision. The listed endpoint and design can inform how a future result might be interpreted, but cannot substitute for that result.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 17 outcome measures. The primary endpoint is a right-foot plantar pressure measure, and the listed secondary outcomes include plantar skin temperature and tissue oxygenation at plantar locations. When many outcomes are examined, general statistical practice considers whether a primary outcome was specified in advance and whether any adjustment or hierarchical testing plan was used. Such a plan is not reported in the registry record. The number of analyses is listed as 0, and numerical findings or test results are not reported.

Missing primary outcome data are explicitly described for 4 healthy subjects. The record attributes incomplete collection to unexpected stops in interface pressure data collection and problems with the insole control box, and states that these subjects were not included in the primary outcome analysis. This indicates an available-data analysis for those individuals on that measure, but the broader analysis population and any additional exclusions are not fully described. The remaining population text is incomplete in the registry record.

The registry does not report the amount of missing data for other outcomes, whether missingness was evaluated by group, or whether any imputation or sensitivity analyses were used. In general, technical missingness can still affect interpretation if the chance of obtaining a measurement is related to the unobserved value or participant characteristics. No assumption about the missing-data mechanism can be justified from the record.

The registry does not report an analysis population definition, a protocol for deviations, or a statistical plan specifying how outcomes were summarized and compared. Those details are not reported in the registry record. As a result, the extent to which analyses followed a prespecified plan and the robustness of findings to missingness or multiple outcomes cannot be assessed.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The adverse-event entries list two groups: Healthy Controls and Patients With Diabetic Neuropathy. For Healthy Controls, the registry records 0 serious adverse events among 20 at risk, 0 other adverse events among 20 at risk, and 0 deaths. For Patients With Diabetic Neuropathy, it records 0 serious adverse events among 1 at risk, 0 other adverse events among 1 at risk, and 0 deaths. These are the recorded counts for the stated groups, not evidence that every possible harm was ruled out.

The group sizes shown for safety reporting should not be assumed to be the primary endpoint analysis populations. The primary endpoint description separately notes incomplete collection for 4 healthy subjects. The registry does not explain the relationship between safety reporting and the analysis population for each outcome.

In general, zero recorded events in a small study do not establish that an intervention has no risk. The ability to detect uncommon events depends on the amount and duration of observation, as well as how events are collected and classified. Follow-up duration for safety outcomes and the event-ascertainment procedures are not reported in the registry record. No serious adverse event terms are listed among the top serious terms. These entries should be read as registry-reported event counts, not as a comprehensive safety conclusion.

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

The study addresses an engineering and measurement question: pressure-alternating shoes are designed to redistribute plantar loading through inflatable cells, and the primary endpoint specifies pressure before any cells are offloaded. The record also describes skin temperature and tissue oxygenation measurements. These features make the study relevant to understanding how a device is evaluated, but the intended mechanism is not itself an observed result.

The posted registry record does not report the numerical primary endpoint estimate, its standard deviation, or an inferential analysis. It therefore does not establish the baseline pressure level in the study population, the amount of variation among measurements, or whether pressure changed with device operation. The listed endpoint is specifically before offloading; a comparative post-offloading result is not reported in that endpoint description.

The study is marked completed, but completion status should not be confused with evidence of benefit or with complete data. The record documents incomplete primary endpoint collection for 4 healthy subjects due to technical issues. It does not provide a final numerical estimate or explain the remaining primary analysis population. It also does not report numerical findings for the secondary outcomes.

The groups described are not a like-for-like control comparison according to the registry. Since assignment was non-randomized and the model is listed as single group, the record does not support interpreting a contrast between healthy controls and people with diabetic neuropathy as a causal device effect. Differences between these groups could reflect their underlying population characteristics. A randomized comparison is not reported in the registry record.

The endpoint is a pressure measure rather than a direct clinical outcome of ulcer prevention. Even a well-measured pressure change would not, by itself, show that ulcers were prevented; that question requires evidence on ulcer outcomes and an appropriate design. No such result is reported in the registry record. The study description can therefore clarify the device concept and intended measurement, while the magnitude, precision, clinical meaning, and safety implications of measured outcomes remain undetermined from the posted information.

13. Why This Trial Matters Statistically

This study is statistically informative as an example of the gap between an outcome definition and an outcome result. The registry specifies a continuous measure, its unit, the foot measured, and the timing relative to device operation. Those details help readers understand what an estimate would represent. Yet without a reported mean, standard deviation, or interval estimate, the endpoint cannot be quantitatively interpreted.

It also illustrates why design labels matter. The registry describes non-randomized allocation and a single-group model, while listing healthy controls and people with diabetic neuropathy. It explicitly warns that these arms are not a like-for-like control comparison. Statistical comparisons cannot remove design limitations simply by producing a p-value; causal interpretation depends on how groups were formed and on whether important differences were addressed. The methods for doing so are not reported in the registry record.

Technical failures are another important statistical issue. Incomplete pressure data for 4 healthy subjects led to their exclusion from the primary outcome analysis. Transparent reporting of missing measurements and the analysis population is essential because the resulting estimate describes those with usable data, and may not represent everyone intended for measurement if data availability is selective.

Finally, the registry lists 17 outcomes but does not report analyses or a multiplicity plan. Prespecification and careful interpretation are important when many outcomes are considered, especially when numerical results are used to make claims. The record's endpoint and design descriptions are useful context, but statistical conclusions require the estimates, uncertainty, and analysis details that are not reported in 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.

The primary limitation for interpreting results is that numerical outcome findings are not reported in the registry record. The primary endpoint definition is available, but its mean, standard deviation, confidence interval, and statistical comparison are not. The number of analyses is listed as 0. Without outcome estimates, neither the size nor precision of a pressure measurement can be judged.

The study is non-randomized, masking is listed as none, and the model is listed as single group. Although two populations are described, the registry cautions that the arms are not a like-for-like control comparison. Any observed differences between the populations would therefore not, by themselves, isolate an effect of the shoes. The registry does not report an adjustment strategy or other design features that would address confounding.

Primary endpoint data collection was incomplete for 4 healthy subjects because of technical problems, and those subjects were excluded from that outcome analysis. The full analysis population description is truncated in the registry record. It does not report whether missingness differed across relevant characteristics, how many measurements were available for each region, or whether sensitivity analyses were conducted.

The endpoint is based on right-foot pressure before offloading, so it does not directly report a clinical ulcer outcome or a pressure response after offloading. The record does not clarify the exact calculation used to derive maximum average pressure. In addition, it lists 17 outcome measures but does not report a multiplicity plan, numerical secondary findings, or an analysis plan. Safety entries report no recorded events in the stated groups, but follow-up duration and event collection methods are not reported. These limitations constrain both causal interpretation and assessment of precision, completeness, and clinical relevance.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Pressure Alternating Shoes — NCT06026813.
• Registry record last updated 2025-08-12; status last verified 2025-07.
• Results first posted 2025-08-12.
• 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 record describes Pressure Alternating Shoes for prevention of diabetic foot ulcers, sponsored by University of Texas Southwestern Medical Center. The study is marked completed, with a non-randomized allocation, no masking, and a single-group model. Enrollment is listed as 21. Its primary endpoint is mean maximum average pressure in the right foot before any cells were offloaded, measured during the first 40-seconds of the walk and expressed in kPa.

The intervention uses an insole with seven air cells intended to shift plantar loading through inflation and deflation. Healthy controls and patients with diabetic neuropathy are described, but the registry cautions that the groups are not a like-for-like control comparison. Technical problems led to incomplete primary endpoint data collection for 4 healthy subjects, who were excluded from that outcome analysis.

The record lists 17 outcome measures and 0 analyses. Numerical primary and secondary results, a statistical analysis plan, and details of the remaining primary analysis population are not reported in the registry record. Adverse-event entries list 0 serious events, 0 other events, and 0 deaths in each reported group.