Different Cryocompression Devices and Skin Temperature of the Knee: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Different Cryocompression Devices and Skin Temperature of the Knee (NCT05355116), a randomized na study. The primary outcome is Skin Temperature.

2. Clinical Question

3. Trial Design

This was a randomized, unmasked crossover study of five cryocompression devices. The registry record identifies enrollment of 32 participants and a completed study. It lists the study start as 2022-04-20 and primary completion as 2022-07-27. The phase is recorded as NA. The sponsor was the University of Winchester.

In a crossover design, participants receive or experience more than one study condition, so comparisons can be made within the same participant. In general, this can reduce the influence of stable differences between people. It also means that observations from one participant are related rather than independent. The registry record says the primary-outcome analysis included individuals who completed participation in all test conditions, but does not report how many participants satisfied that definition.

The five devices were Physiolab S1, Breg Vpulse, Cryo/Cuff, GameReady, and Physiolab Gel Therapy Wrap. The descriptions specify cuffs spanning mid-thigh to mid-calf. Some devices used temperature-controlled cold water and pressure settings; for Cryo/Cuff and the Physiolab Gel Therapy Wrap, the applied pressure and temperature are described as non-modifiable and undefined. The device descriptions are not complete enough in the registry record to establish every operating detail.

Randomization is recorded, but the sequence-generation method, allocation concealment, and assignment of treatment order are not reported in the registry record. Masking is recorded as none. The order of device sessions, any washout interval, the session conditions, and whether participants received all devices in a standardized sequence are not reported. The record also does not give a sample-size justification or a statistical analysis plan. Those details matter when interpreting repeated measurements and comparisons across multiple devices.

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: 32 participants were enrolled and began the data collection phase.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Individuals who completed their participation in all test conditions were included in the final analysis.

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: Although 32 participants were originally enrolled, only the data from 30 participants was included in the final analysis due to the withdrawal of 2 participants from the study for unknown reasons prior to their completion of all test conditions.

6. Primary Endpoint

The registry lists the primary outcome as Skin Temperature, measured over Up to 40 minutes per treatment.

The primary endpoint is skin temperature, a continuous measurement reported as a mean with standard deviation. A thermocouple was positioned 20 mm distal to the patella. Temperature was measured before the device was applied, every 5 minutes during testing, and every 5 minutes after a test until the skin temperature reached >15°C. The stated timeframe was up to 40 minutes per treatment.

The endpoint addresses whether the devices produce different temperature patterns around the knee during and after cooling. The registry background explains that the temperature setting of a device may not equal the temperature reached at the skin, so measuring skin temperature directly is relevant to the stated research question. It also describes 10–15°C as the therapeutic skin-temperature range thought to be relevant to cryotherapy. That background rationale is not itself a trial result.

The registry record does not specify which point or summary across the measurement period constitutes the reported primary comparison, nor does it provide results by device, time point, or participant. The primary-outcome results and their uncertainty are therefore not reported in the registry record. The record lists Subjective Comfort as a secondary outcome, but does not report its results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a continuous primary outcome summarized by a mean and standard deviation, but does not report the analysis used. The concepts below are general explanations, not a description of methods confirmed for this study.

What does a mean and standard deviation describe?

In general, a mean describes the central level of a continuous measurement across observations. A standard deviation describes how spread out those measurements are around the mean. They answer different questions: a mean gives a measure of location, while a standard deviation gives a measure of variability among observations. Neither one alone shows the uncertainty in an estimated mean or the uncertainty in a comparison between devices. A confidence interval is commonly used to express that uncertainty; it gives a range of values compatible with the data and the analysis assumptions. The registry record does not report confidence intervals for the skin-temperature outcome.

Why does the crossover design matter?

In general, a crossover study measures a participant under more than one condition. Measurements from the same person tend to be related, so an analysis that treats every measurement as independent may give an inappropriate estimate of uncertainty. A paired comparison or a model that accounts for participant-level correlation can reflect the within-person structure. Which approach is suitable depends on the design and data structure. The registry record does not identify the model used, provide participant-level results, or say how the device conditions were ordered.

Order can matter if the response to one condition carries over into a later condition, or if measurements change over time for reasons unrelated to the device. In general, investigators may consider treatment order, period, and carryover when planning or analyzing crossover studies. Whether such effects were considered, and whether there was a washout between sessions, are not reported in the registry record. No particular carryover effect should be assumed from this absence.

How should repeated temperature measurements be understood?

Measurements taken repeatedly during one treatment session are also related. They describe change over time, but do not amount to independent replications of the treatment. In general, repeated-measures methods can model the pattern over time and account for correlations among observations. The method may depend on whether the main interest is a specific time point, an average across time, or the overall trajectory. The registry record gives the measurement schedule and endpoint description, but does not specify which summary was analyzed or the statistical approach to repeated measures.

Device comparisons across multiple time points also raise a question of multiplicity. In general, making many statistical comparisons increases the chance of a chance finding if each is judged without considering the number of comparisons. A prespecified primary comparison or a suitable adjustment can help address this issue. The registry record does not state the intended comparison set, any multiplicity procedure, or whether analyses were prespecified. It is not possible to determine from the record how multiplicity was handled.

What do statistical significance and precision mean?

In general, a p-value describes how compatible data are with a specified statistical model and a null hypothesis; it is not a measure of the size or importance of an effect. A confidence interval communicates precision and the range of effect sizes compatible with the data under the analysis assumptions. Interpreting either requires knowing the comparison, the analysis, and the estimate. Because the registry record does not report the primary results or analysis, no trial-specific conclusion about statistical significance, effect size, or precision can be drawn.

What is the role of a sample-size illustration?

The registry record describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Such planning calculations are not observed outcomes and do not show how likely the completed study was to detect an effect. They depend on the effect size chosen for planning and on the assumptions used. The record does not report the effect estimate or the numerical planning results, and it does not report the trial's own sample-size justification. No sample-size value or power conclusion can be inferred from the available information.

What can be said about the analysis population?

The primary-outcome population is described as individuals who completed participation in all test conditions. In general, restricting an analysis to completers can affect interpretation if completion is related to measured outcomes or treatment experience. The record does not give the number included in this population, the number or reasons for incomplete participation, or any alternative analysis population. It also does not report how missing temperature measurements were handled. These omissions limit assessment of possible bias and of how well the analyzed participants represent everyone enrolled.

10. Multiplicity, Missing Data and Analysis Populations

The registry record describes temperature measurements at multiple times and compares five devices. In general, testing multiple devices, time points, or outcome summaries can create multiplicity: the more comparisons considered, the greater the opportunity for a chance result to appear noteworthy. A prespecified primary comparison or an appropriate multiplicity strategy can help control interpretation. The registry record does not describe a planned comparison hierarchy, a correction for multiple testing, or which comparisons were designated primary beyond naming skin temperature as the primary outcome.

The primary-outcome analysis population is defined as individuals who completed participation in all test conditions. The number who met that definition, the number with incomplete participation, and the reasons for missing data are not reported in the registry record. The record also does not explain how missing measurements within a treatment session were handled or whether any sensitivity analyses were conducted.

These gaps matter in a crossover study because a participant may contribute measurements under several device conditions, while incomplete participation could leave some conditions observed and others unobserved. In general, the consequences depend on why data are missing and on the analysis method. The registry record does not provide enough information to assess whether missingness could have affected comparisons.

The number of analysis entries is recorded as 0. This indicates that the registry record does not contain analysis entries; it does not establish whether analyses were performed outside the registry. Statistical methods, multiplicity handling, and missing-data procedures are not reported in the registry record.

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.

For each of the five device groups, the registry record lists 32 participants at risk for serious adverse events and 0 affected. It also lists 32 at risk for other adverse events and 0 affected. Deaths are recorded as 0 for each group. These are group-specific registry counts, not a comparison of estimated risks with confidence intervals.

Because this is a crossover study, the same participant may contribute experience under more than one device condition. The 32 at risk listed for each group should therefore be read as the recorded denominator for that group, not added across groups to infer a count of distinct participants. The registry record does not explain the adverse-event collection procedures, event definitions beyond the serious and other categories, or the duration of safety follow-up.

Zero affected participants in the recorded categories means no such affected participants are listed in the registry results for those groups. It does not demonstrate that an event is impossible or that all potential harms were measured with equal sensitivity. The registry record does not provide event narratives or further safety analyses.

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

The record identifies a randomized crossover comparison of five cryocompression devices and describes a plan to measure skin temperature around the knee. It gives the measurement location, schedule, and stated timeframe. These details define the research question and indicate what kind of response was intended to be measured.

However, the primary outcome findings are not reported in the registry record. No device-specific temperature summaries, comparisons, or uncertainty estimates are available. As a result, the record does not establish which device produced a higher or lower skin temperature, whether any differences were large or small, or how precisely those differences were estimated. It also does not show whether temperatures fell within the 10–15°C range discussed in the registry background.

Even if numerical temperature results were available, this study concerns skin temperature under the recorded test conditions. The registry record does not report clinical outcomes that would establish effects on recovery, symptoms, or other aspects of postoperative rehabilitation. The background discusses potential relevance of cooling and cold-injury concerns, but that rationale should not be read as a finding from this comparison.

The safety counts record zero affected participants for serious and other adverse events in each group, and zero deaths. They should be interpreted as registry counts, with the limitations of the stated denominators and unreported safety-collection details. They do not resolve the missing primary outcome results.

Overall, the registry record provides design and measurement information but not the results needed to judge device-to-device temperature differences. It is therefore not possible to draw a trial-specific conclusion about comparative temperature effects or the precision of those effects from this record.

13. Why This Trial Matters Statistically

This study addresses a measurement question that is important to interpreting device settings: the temperature selected or delivered by a device may not be the same as the temperature measured at the skin. The registry background explicitly identifies that distinction and describes direct skin-temperature monitoring as the relevant outcome. Comparing devices on the measured skin response is therefore statistically different from comparing their settings alone.

The crossover design is also statistically notable. In general, within-participant comparisons can reduce the influence of stable differences between individuals, but they require methods that account for related observations and possible effects of order or time. The registry record identifies randomization and crossover design, yet does not report how treatment order was handled or which analysis method was used. This makes the design structure important to understanding what a complete analysis would need to address.

Temperature was measured repeatedly during and after treatment. Such data can describe a changing response rather than a single static outcome. The analysis choice determines whether the main comparison concerns a particular time, a summary over time, or a trajectory. The record gives the schedule but does not state which summary was used for the primary comparison. This illustrates why endpoint definition and analysis details are essential alongside the measurement plan.

The registry record does not include primary outcome results or analysis entries. That absence leaves the central statistical question unanswered in the record, despite the detailed description of the devices and measurement procedure. It also prevents assessment of effect size, uncertainty, and multiplicity. The study is therefore informative about the intended comparison and the structure of the measurements, but the available registry information is insufficient for evaluating the comparative temperature findings.

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 principal limitation of the registry record for statistical interpretation is that it does not report primary outcome results. Device-specific means, standard deviations, comparisons, and uncertainty estimates are absent. The registry record lists no analysis entries, so there is no reported statistical model or test to evaluate.

The primary-outcome population is defined by completion of all test conditions, but the number of participants included in that population is not reported. The registry record does not describe incomplete participation, missing measurements, reasons for missingness, or any method for handling missing data. This prevents assessment of how closely the analyzed population corresponds to those enrolled.

Although randomization and crossover design are recorded, the sequence-generation method, allocation concealment, treatment order, and any washout interval are not reported. The statistical approach to within-participant dependence and repeated measurements is also not reported. The record does not explain which time point or summary of the temperature series was used as the primary comparison.

The record does not report a multiplicity plan for comparisons across devices or measurement times. It also does not provide a sample-size justification. A planning illustration is described, but its observed-effect input and numerical output are not reported in the registry record, so it cannot clarify the precision achieved in the completed study.

Safety information is limited to the group-level counts of affected participants and deaths. The collection procedures, definitions, and follow-up details are not reported. These limitations concern what can be learned from the registry record; they do not establish that the underlying study lacked additional methods or results.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Different Cryocompression Devices and Skin Temperature of the Knee — NCT05355116.
• Registry record last updated 2024-11-06; status last verified 2024-10.
• Results first posted 2024-11-06.
• 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 a completed, randomized, unmasked crossover study sponsored by the University of Winchester, with enrollment of 32 participants. It compares Physiolab S1, Breg Vpulse, Cryo/Cuff, GameReady, and Physiolab Gel Therapy Wrap. The primary outcome is skin temperature measured at a location 20 mm distal to the patella, before, during, and after device use, with a stated timeframe of up to 40 minutes per treatment.

The primary analysis population is described as participants completing all test conditions. Subjective Comfort is listed as a secondary outcome. The registry record reports zero participants affected by serious or other adverse events and zero deaths for each device group, with 32 at risk recorded in each group.

Primary outcome results, statistical analyses, missing-data methods, and multiplicity procedures are not reported in the registry record. The available information therefore describes the study design and measurement plan, but does not permit evaluation of comparative skin-temperature findings.