In Vivo Optical Spectroscopy Monitoring in a New Model of Muscular Compartment Syndrome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for In Vivo Optical Spectroscopy Monitoring in a New Model of Muscular Compartment Syndrome (NCT01452425), a na phase 1 study. The primary outcome is Comparison Between INVOS Monitoring and Electromyography.

2. Clinical Question

The registry describes muscular compartment syndrome as a consequence of increased intramuscular compartment pressure and identifies it as a rare but serious postoperative complication. The study’s objective was to develop a model mimicking its pathophysiology and assess the potential use of INVOS in that model. INVOS is described as a continuous, non-invasive monitor of tissue oxygenation.

The planned primary measure was a comparison of INVOS monitoring with non-invasive EMG monitoring, with the aim of determining INVOS accuracy for predicting AP block. The registry specifies mean and standard deviation for INVOS values at baseline and at the time of the block, with the unit reported as % of StcO2 and a timeframe of 45 minutes. These details describe the intended measurement, not an observed result. The registry record does not report numerical endpoint estimates, a measure of diagnostic accuracy, or the results of the INVOS–EMG comparison.

The question is therefore about measurement performance in a volunteer model, not about comparing clinical treatments or evaluating patient outcomes. Whether the planned model generated a useful predictive signal cannot be determined from the outcome information reported in the registry record.

3. Trial Design

NCT01452425 is listed as a completed Phase 1 study sponsored by Université Catholique de Louvain. The registry records a start date of 2011-10, a primary completion date of 2011-12, and enrollment of 10. The population is identified as human volunteers. The study model is single-group, allocation is listed as NA, and masking is listed as none.

The intervention entries are Tourniquet, INVOS assessment, and EMG assessment. The arm description specifies inflation of a tourniquet. In context, tourniquet inflation was intended to create a model that mimicked the pathophysiology of muscular compartment syndrome. INVOS and non-invasive, transcutaneous EMG monitoring were to be compared in relation to AP block. The record does not describe a separate control group or a randomized assignment to different interventions.

The primary outcome is titled “Comparison Between INVOS Monitoring and Electromyography.” It specifies mean and standard deviation for INVOS measurements at baseline and at the time of the block, reported in % of StcO2, over a timeframe of 45 minutes. The registry lists 2 outcome measures, but further details for the other measure are not reported in the registry record. No statistical analyses are listed.

The design should be read as a small, single-group physiological monitoring study, rather than as a controlled trial of clinical treatment. Its planned comparison concerns measurements made with monitoring devices in a model involving volunteers. The registry’s completed status indicates that the study record is marked completed; it does not establish that all planned analyses or results are posted. The registry record does not report further details about the sequence or timing of assessments, the criteria used to identify AP block, or how the comparison was to be analyzed.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

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 Comparison Between INVOS Monitoring and Electromyography, measured over 45 minutes.

The primary endpoint concerns the comparison of INVOS monitoring with non-invasive, transcutaneous EMG monitoring to determine whether INVOS could predict AP block. The registry describes INVOS as a continuous, non-invasive monitor of tissue oxygenation. It specifies INVOS values at baseline and at the time of the block, summarized as a mean with a standard deviation and expressed in % of StcO2. The stated timeframe is 45 minutes.

These measurements address a physiological monitoring question: whether changes in the INVOS signal align with the event identified through EMG monitoring in the tourniquet model. Comparing measurements at baseline and during the modeled event can be informative because it relates the monitoring signal to a defined physiological context. More generally, an objective measure of agreement or prediction can help assess whether a monitor tracks a target event. The registry record, however, does not report which accuracy metric was planned or how a successful prediction was to be defined.

The endpoint description is not itself evidence that INVOS predicted AP block accurately. No means, standard deviations, individual-level data, comparison estimate, uncertainty interval, or diagnostic performance result is reported in the registry record. The stated endpoint and rationale explain what the study sought to assess; they do not establish what the measurements showed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous outcome summarized by a mean and standard deviation. These are descriptive statistics: the mean locates the center of a set of measurements, while the standard deviation describes how spread out measurements are around that center. They answer different questions. A mean alone does not show how consistent individual measurements were, and a standard deviation does not show the precision of an estimated mean.

What would a comparison of measurements address?

In general, comparing measurements from two monitoring methods asks whether their signals relate to the same target or event. Agreement and prediction are not interchangeable ideas. Two methods may move in a similar direction yet differ in their absolute readings; conversely, a measure may appear associated with an event without being sufficiently accurate for individual prediction. A suitable analysis depends on the intended claim and on how the target event is defined. The registry says that INVOS was to be assessed for its ability to predict AP block using EMG monitoring, but it does not report the chosen statistical definition of prediction or the planned comparison method.

The endpoint description refers to INVOS at baseline and at the time of the block. In general, measurements from the same participant at different times are related rather than independent. An analysis should account for that relationship when estimating change or comparing measurements. The registry record does not specify whether the measurements were analyzed as paired observations, how observations were handled if the timing differed, or whether the participant-level data were available for analysis.

How should uncertainty be understood?

A confidence interval is a way to express the uncertainty around an estimated quantity. It is distinct from a standard deviation: the standard deviation describes variability among measurements, while a confidence interval describes uncertainty in an estimate under the assumptions of the analysis. Neither the primary outcome description nor the posted results include a confidence interval. Without the estimate and its uncertainty, readers cannot judge how precisely the INVOS–EMG comparison was characterized.

In general, small studies can produce estimates with substantial uncertainty, particularly when measurements vary or the event of interest is uncommon. This is a general statistical consideration, not a claim about the observed variability or event frequency in this study. The registry record gives enrollment of 10, but does not report the outcome data needed to assess the actual precision of the endpoint.

What do the planning assumptions represent?

The registry’s sample-size assumptions describe planning illustrations computed from an observed effect, rather than the trial’s own design. They specify 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. Such illustrations are conditional calculations: their meaning depends on the effect estimate and assumptions used. They are not observed outcomes and do not establish observed power.

These assumptions do not match the recorded single-group model, in which allocation is listed as NA. The equal-allocation assumption between two arms describes a hypothetical planning comparison, not the design recorded for this study. The registry record does not report the original sample-size justification or explain a design-based power calculation. The planning illustrations should therefore be interpreted as hypothetical planning information, not evidence that the study was designed or powered according to those assumptions.

What cannot be evaluated from the record?

No analysis methods are listed, and the registry record does not report outcome estimates. Consequently, it is not possible to evaluate the selected statistical model, the handling of repeated measurements, the definition of AP block for analysis, or the robustness of the results to alternative assumptions. The record also does not report whether missing measurements occurred or how missing data would have been handled. These are limits on what can be assessed from the registry entry, not evidence that a particular analytic problem occurred.

More generally, monitoring studies benefit from a clear distinction between descriptive signal changes, association with a reference measurement, and predictive accuracy. A mean and standard deviation describe a distribution but do not, by themselves, quantify classification performance or individual-level prediction. The registry identifies the intended comparison but does not give enough information to determine which of these statistical aims was ultimately addressed or what the results were.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures, but it gives detailed information about the primary measure only. The other outcome’s definition, timing, and results are not reported in the registry record. No statistical analyses are listed, and the record does not describe a testing hierarchy, an adjustment for multiple comparisons, or a prespecified distinction among analyses.

In general, examining multiple outcomes or multiple analyses can increase the chance of finding an apparently notable result by chance. A prespecified analysis plan and a clear account of which findings are confirmatory can help readers interpret that risk. This is a general methodological point; the registry record does not establish which analyses were conducted or whether multiplicity was addressed outside the record.

The registry does not report missing-data counts, the completeness of the INVOS or EMG measurements, or any method for handling missing observations. It also does not specify an analysis population, such as which enrolled participants or measurements would be included in the primary analysis. No interim analyses or statistical analysis plan are reported in the registry record. These omissions prevent assessment of whether the posted endpoint was analyzed as planned, but they do not show that data were missing or that an interim analysis occurred.

Because there are no outcome estimates or analysis results in the registry record, missing-data and multiplicity decisions cannot be connected to observed findings. Interpretation should remain limited to the stated study objective and design.

11. Safety Results

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

Other (non-serious) adverse events

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

For the Tourniquet group, the registry reports 10 participants at risk for serious adverse events and 0 affected. It also reports 10 at risk for other adverse events and 0 affected. These are the adverse-event figures recorded for the group; the registry does not provide terms for any serious adverse events.

The death count is not reported in the registry record. It should not be interpreted as a reported count of zero. The listed figures also do not establish that every possible adverse event was assessed or captured, nor do they describe event severity beyond the serious-versus-other categories.

In general, observing no reported events in a study does not demonstrate that the risk of an event is absent. Interpretation depends on the number of participants observed, the follow-up and surveillance procedures, and the completeness of reporting. The registry gives the at-risk counts but does not describe adverse-event collection methods or provide further safety detail. These figures describe what was posted; they do not support a broader conclusion about safety in other populations or settings.

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

This study asks whether INVOS monitoring can predict AP block in a tourniquet model intended to mimic aspects of muscular compartment syndrome. It compares INVOS with non-invasive, transcutaneous EMG monitoring and describes INVOS measurements at baseline and at the time of the block. That is the scope of the research question stated in the registry.

The registry record does not report numerical primary outcome results or an analysis of the comparison. It therefore cannot establish whether INVOS values changed, how they related to EMG findings, or how accurately INVOS predicted AP block. It would be inappropriate to treat the study objective as evidence that prediction succeeded or failed. No reported estimate is available to quantify the strength or precision of the comparison.

Even if a monitoring signal were informative in this model, a volunteer study using tourniquet inflation would not by itself establish performance in postoperative patients. The registry describes a model-development objective, not a clinical diagnostic validation study. The record does not report patient outcomes, a clinical decision rule, or an evaluation of whether monitoring changes care.

The posted adverse-event figures report 0 serious and 0 other adverse events among the participants listed at risk in the Tourniquet group. The death count is not reported. Those entries should be read as registry safety reporting, not as proof that risk is absent or as a basis for claims about broader clinical use.

Overall, the record documents a completed, single-group physiological monitoring study with a stated comparison and endpoint, but it does not post the outcome results needed to evaluate the central question. The result does not support a positive or negative conclusion about INVOS prediction. It identifies what the investigators sought to assess and leaves the performance of the monitor unresolved in the registry record.

13. Why This Trial Matters Statistically

Statistically, this study is useful as an example of the distinction between a clearly stated research question and a reported result. The registry identifies the intended target—prediction of AP block—and the monitoring methods to be compared. It also specifies a continuous INVOS measure summarized by a mean and standard deviation. Those details help define what an analysis would need to address, but they do not substitute for numerical results.

The single-group design also makes the comparison fundamentally different from a randomized trial of competing treatments. The study concerns measurements under a tourniquet model, rather than outcomes in separate intervention groups. Recognizing the design prevents hypothetical two-arm planning assumptions from being mistaken for the actual study structure.

The record illustrates why descriptive summaries and predictive claims need to be distinguished. Means and standard deviations can characterize readings, while a claim about prediction requires an analysis linking those readings to a defined event. The registry does not report that analysis or its estimate. Without results and uncertainty measures, readers cannot assess whether a signal was consistent, how precise any estimated relationship was, or how well the planned comparison performed.

Finally, registry completeness matters to statistical interpretation. A completed status and a stated endpoint do not guarantee that the endpoint’s results are posted. When results, methods, and missing-data details are absent, the appropriate conclusion is limited: the question and design are documented, but the result cannot be evaluated from the registry record. This distinction helps prevent intentions, planning assumptions, and safety counts from being read as evidence about the primary monitoring question.

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 most important limitation for interpreting this trial is that the registry record does not report the primary outcome results. Although the endpoint description specifies the intended measurements and comparison, it gives no INVOS estimates, variability, or measure of prediction accuracy. The central research question therefore remains unanswered by the posted results.

The study is recorded as a single-group investigation in human volunteers, using tourniquet inflation to model aspects of muscular compartment syndrome. It does not provide a randomized control comparison. This limits the scope of any inference to the monitoring question in the stated model; the registry does not establish applicability to patients experiencing postoperative compartment syndrome.

The registry provides limited detail about how measurements were collected and analyzed. It does not report the operational definition of AP block, the specific statistical method, how repeated measurements were handled, or whether all planned observations were available. It also does not describe eligibility criteria beyond identifying the population as human volunteers. Such information is not reported in the registry record and should not be assumed.

Although the record lists 2 outcome measures, detailed information is available only for the primary outcome. No analyses are listed, and the record does not report a statistical analysis plan, multiplicity approach, analysis population, or missing-data method. These gaps mean that the analysis process and the completeness of outcome reporting cannot be assessed.

The adverse-event entry reports no affected participants in the posted serious or other event categories, but the death count and event-collection procedures are not reported. The planning assumptions describe a hypothetical two-arm calculation and are not the design recorded for this study. Together, these limitations require a cautious reading: the registry documents the objective and design, but does not provide enough outcome or methods information to evaluate monitor performance.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: In Vivo Optical Spectroscopy Monitoring in a New Model of Muscular Compartment Syndrome — NCT01452425.
• Registry record last updated 2014-12-22; status last verified 2014-12.
• Results first posted 2014-12-22.
• 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

NCT01452425, “In Vivo Optical Spectroscopy Monitoring in a New Model of Muscular Compartment Syndrome,” is listed as a completed Phase 1, single-group study in human volunteers, sponsored by Université Catholique de Louvain. The registry records a start date of 2011-10, primary completion on 2011-12, and enrollment of 10.

Tourniquet inflation was used in a model intended to mimic muscular compartment syndrome. The planned primary comparison was INVOS monitoring against non-invasive, transcutaneous EMG monitoring for predicting AP block. INVOS measurements were specified at baseline and at the time of the block, in % of StcO2, over 45 minutes.

The registry lists 2 outcome measures but no statistical analyses. Numerical primary results are not reported in the registry record. For the Tourniquet group, 0 serious and 0 other adverse events are reported among 10 participants at risk in each category; the death count is not reported. The posted information documents the study question and design but does not permit evaluation of the primary monitoring result.