ICG Fluorescence Imaging in Trauma Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for ICG Fluorescence Imaging in Trauma Patients (NCT04245111), a registered phase not stated study. The primary outcome is Percent of Patients That Complete the Protocol.

2. Clinical Question

3. Trial Design

NCT04245111 is listed as a completed prospective observational trial sponsored by Dartmouth-Hitchcock Medical Center. The registry lists enrollment as 20. The study began on 2019-05-16, and primary completion is listed as 2021-11-23. Its stated purpose was to characterize variation in bone and soft-tissue perfusion in fracture patients and examine the relationship between perfusion measured by quantitative ICG fluorescence and complications.

The record describes three clinical cohorts rather than randomized treatment arms. The Open Fracture Cohort includes adults with an open extremity fracture and planned definitive fracture management with external fixation, internal fixation, or joint fusion. Its criteria also include formal surgical debridement within 72 hours of injury. The Closed Fracture Cohort is for adults with a closed extremity fracture and planned definitive management using those approaches; the description also notes informed consent. The Complication Cohort includes adults with an extremity fracture who have had definitive fracture management and a superficial, deep, or organ space surgical-site infection at the fracture site requiring operative management. The cohort description is truncated after its statement about fracture care, so further detail is not reported in the registry record.

Because this is observational and the cohorts have different eligibility criteria, they should not be treated as exchangeable groups in a controlled comparison. Allocation is not stated. The registry record does not report a protocol for assigning participants to cohorts, the timing or schedule of imaging, or a detailed account of follow-up. The listed primary endpoint is protocol completion, while the study summary also identifies perfusion and complications as subjects of interest. A detailed statistical analysis plan is 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.

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.

6. Primary Endpoint

The registry lists the primary outcome as Percent of Patients That Complete the Protocol, measured over 1 year.

The primary endpoint is the percent of patients that successfully complete the protocol. The registry identifies the study as a pilot and feasibility study and gives a timeframe of 1 year for this outcome. Protocol completion is a feasibility measure: it describes whether the study procedures can be completed, rather than whether imaging changes a clinical outcome.

To interpret a percentage of completion, readers need to know how completion was defined and which participants were included in its denominator. Those operational details, the completion count, and the resulting percentage are not reported in the registry record. Consequently, the endpoint's stated purpose is clear, but its observed value cannot be assessed from the record.

In general, a feasibility endpoint can help characterize whether a study process is workable and can inform the design of later research. It does not establish that a measurement predicts complications or that any clinical intervention is beneficial. Here, the broader rationale concerns quantitative ICG fluorescence as a measure of perfusion and its possible relationship to surgical-site infection, persistent infection, and fracture nonunion. The registry record does not report a primary endpoint result for those relationships, nor does it identify them as the registered primary outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does an observational design imply?

In general, an observational study records measurements and outcomes without randomly assigning participants to treatments. The registry describes this trial as prospective and observational. Prospective means the study was planned to collect information forward in time; it does not, on its own, establish that every planned measurement was completed or that follow-up was complete. The registry record does not give a detailed schedule of measurements or follow-up procedures.

The cohorts are defined by clinical characteristics, not by random allocation. This matters when interpreting comparisons: groups selected because they have different fracture or complication characteristics may also differ in other ways. Without a randomized comparison or an adequately described adjustment strategy, an observed association cannot be interpreted as a causal effect. The allocation method and any adjustment strategy are not reported in the registry record.

What would the primary endpoint estimate?

The primary endpoint is the percentage of patients who successfully complete the protocol. In general, a percentage is a count of people meeting a specified definition divided by the count of people eligible for that calculation. A clear interpretation depends on both parts: what qualifies as completion and which participants are included. Neither the operational definition nor the completion counts are reported in the registry record. The record therefore states the feasibility question but does not provide a result that can be checked or interpreted for precision.

Percentages can be accompanied by confidence intervals. In general, a confidence interval describes the range of values reasonably compatible with the observed data under a specified statistical model. It communicates uncertainty and is not a guarantee that the true value lies within that range. No confidence interval for protocol completion is reported in the registry record. With a pilot study, estimates can also be imprecise; the actual degree of uncertainty cannot be assessed without the endpoint data and its analysis.

How should perfusion and complication relationships be assessed?

The study summary identifies quantitative ICG fluorescence as the measure of perfusion and names surgical-site infection, persistent surgical-site infection, and fracture nonunion as complications of interest. In general, an analysis of a relationship needs a defined perfusion measure, an outcome definition, and a stated method for comparing or modeling them. The registry record does not report those values, the timing of measurement relative to complications, or a statistical model for these relationships. No effect estimate or uncertainty interval for them is reported.

Clinical cohort comparisons require particular caution. The complication cohort is defined by the presence of a surgical-site infection requiring operative management, while the other cohorts are defined by open or closed fracture criteria. This makes cohort membership a clinical distinction, not a randomized exposure. Even if group-level values were available, a contrast among these cohorts would not automatically estimate the effect of an intervention or the predictive accuracy of a perfusion measure. The record does not state that the study used a predictive model, diagnostic accuracy analysis, or a prespecified comparison among cohorts.

What can the sample-size illustration tell readers?

The registry describes a planning illustration based on the observed effect. Its stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the planning target is expressed as a stated fraction of the observed effect. These are assumptions for a hypothetical planning calculation, not evidence that the trial used those design features. The trial itself is described as observational, and allocation is not stated.

In general, planning calculations estimate the sample size needed under specified assumptions about an effect, variability, allocation, and statistical decision rule. Their output depends on those assumptions. Calculations based on an effect observed in a pilot study can be uncertain because that effect estimate may itself be imprecise. They should be read as planning illustrations, not as proof that the completed study had adequate power. They are not observed power. The registry record does not report a sample-size justification for the actual study design.

Why might over-dispersion matter?

In general, over-dispersion occurs when observed variability in count data exceeds what a chosen model assumes. Ignoring it can make uncertainty appear too small. This concept is relevant to some analyses of counts, but the registry does not report a count model or any analysis of perfusion or complications that would permit assessment of over-dispersion. The primary endpoint is a percentage of protocol completion, and its result and analysis are not reported. No particular statistical model should therefore be inferred from the endpoint label or study summary.

The registry lists one outcome measure and one analysis. That listing does not disclose the statistical test, model, covariates, missing-data procedures, or handling of multiple outcomes or comparisons. Those methods are not reported in the registry record. The statistical interpretation must remain limited to the study's stated design and the results that are actually recorded.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and one analysis, and identifies protocol completion as the primary outcome. This does not establish that only one analysis was planned or conducted. The analysis plan, including whether additional outcomes or subgroup comparisons were examined, is not reported in the registry record. A prespecified multiplicity strategy is also not reported.

In general, multiplicity arises when several statistical tests or comparisons are considered. The more opportunities there are to find a nominally unusual result, the more important it is to understand whether the analyses were planned and whether any adjustment or interpretation strategy was used. The record does not provide enough detail to determine whether multiplicity is relevant to the unreported perfusion and complication analyses.

The registry does not report missing-data counts, reasons for non-completion, or a method for handling missing measurements or outcomes. These details matter for a feasibility endpoint: participants with incomplete study procedures may be central to the completion estimate, and excluding them without explanation could alter its interpretation. The completion definition and denominator are not reported, so the impact of missingness cannot be assessed.

The named cohorts give eligibility criteria, but the analysis populations are not described beyond those definitions. It is not reported whether all enrolled participants contributed to each outcome, how withdrawals were handled, or whether analyses used an intention-to-observe or other population definition. The registry also does not report a protocol-deviation policy. These omissions limit reproducibility and make it impossible to judge whether the recorded analysis populations correspond to the intended study populations.

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 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: rehospitalization for procedure (16.7%), complication due to surgery (16.7%).

The registry reports serious adverse events separately for the three cohorts. In the Open Fracture Cohort, 13 were at risk and 2 were affected; in the Complication Cohort, 6 were at risk and 2 were affected; in the Closed Fracture Cohort, 1 was at risk and 0 were affected. The record lists 0 other adverse events in each cohort, with at-risk counts of 13, 6, and 1, respectively. Deaths are listed as 0 for every cohort.

The two serious-event terms identified in the record are “Rehospitalization for procedure” and “Complication due to surgery,” each listed as 16.7%. The record does not specify in the adverse-event summary how these terms map to individual cohorts, so they should not be attributed to a particular cohort. The listed at-risk counts are safety-reporting figures; they are not the denominator for the protocol-completion endpoint.

These entries describe reported events and do not establish that imaging caused an event or that an event was caused by a particular clinical circumstance. Further detail on event timing, severity criteria, relatedness, and duration is not reported in the registry record. The safety entries should therefore be read descriptively, not as a comparative safety estimate.

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

The record establishes that NCT04245111 was a completed prospective observational pilot study focused on quantitative ICG fluorescence imaging in fracture patients. It identifies protocol completion as the primary outcome and describes a broader interest in perfusion variation and complications. It also records adverse-event counts by cohort. These registry entries characterize the study's purpose and the information entered in the registry.

The registry does not report the result for the primary endpoint. The completion definition, numerator, denominator, and percentage are absent. Nor does it report perfusion measurements or estimates linking perfusion to surgical-site infection, persistent surgical-site infection, or fracture nonunion. The study's completed status cannot substitute for those results, and the record does not permit a judgment about the magnitude or precision of the intended feasibility or association findings.

The observational cohort structure does not support a randomized treatment-effect interpretation. The cohorts have distinct eligibility criteria, and allocation is not stated. Therefore, the record does not establish that any observed difference between cohorts would be attributable to imaging, perfusion, or a treatment strategy. It also does not establish that ICG fluorescence predicts complications or improves clinical decisions.

In general, pilot and feasibility studies can inform whether research procedures and measurements merit further evaluation. Their findings need to be interpreted in light of the precision of estimates, the completeness of outcome reporting, and the design used. Here, the registry record does not report enough endpoint or analysis detail to assess those features. The posted adverse-event figures are descriptive and do not answer the primary feasibility question or the broader perfusion question.

13. Why This Trial Matters Statistically

This trial is statistically interesting because it frames perfusion imaging as a measurement question within a clinically varied fracture population. Its stated rationale is to characterize variation in bone and soft-tissue perfusion and examine whether measured perfusion relates to complications. That kind of question depends not only on collecting measurements, but also on defining the measurement, the timing, the relevant outcomes, and how uncertainty will be represented.

The pilot and feasibility framing also places protocol completion at the center of the registered primary endpoint. Feasibility is distinct from clinical effectiveness: completion can describe whether procedures were carried out, while an association between perfusion and complications would require a separate analysis. Keeping these questions separate helps prevent a feasibility result from being interpreted as evidence about prediction or clinical benefit.

The cohort structure illustrates a recurring challenge in observational research. Groups defined by different clinical circumstances are not automatically valid controls for one another. Without random allocation and a clearly described analysis, comparisons may reflect the criteria used to form cohorts rather than a relationship that can be generalized to other patients. The registry record does not report such an analysis, so the distinction is important when reading the stated aims.

Finally, transparent outcome and analysis reporting is essential for evaluating precision and reproducibility. The primary endpoint is named, but its observed result and operational details are not reported in the registry record. This limits what can be learned statistically from the recorded information, even though the study's topic and design are clearly stated.

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.

Several limitations follow from what is and is not reported in the registry. Most importantly, the primary protocol-completion result is absent. The registry does not state how completion was defined, how many participants completed the protocol, or the denominator used for the percentage. A reader cannot evaluate the feasibility outcome or its precision from the record.

The study summary describes quantitative ICG fluorescence and its intended relationship to complications, but no perfusion values, complication associations, or uncertainty estimates are reported. The record does not detail when imaging occurred relative to fracture management or complications, which limits interpretation of any potential temporal relationship. It also does not describe a statistical model or adjustment strategy.

The cohorts have distinct clinical eligibility criteria, and the study is observational. Allocation is not stated, and the record explicitly does not describe a randomized comparison. As a result, the cohorts should not be treated as equivalent control groups. The Complication Cohort description is truncated after its reference to fracture care, so its full eligibility description is not available in the registry record.

The registry does not report a statistical analysis plan, sample-size justification for the actual study design, missing-data handling, analysis-population definitions, or a multiplicity strategy. Although a planning illustration is described, its assumptions do not establish how the observational study was designed or analyzed. The adverse-event summary lacks detail on timing and event relatedness. These reporting gaps limit assessment of reproducibility, uncertainty, and the scope of conclusions that can be drawn.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: ICG Fluorescence Imaging in Trauma Patients — NCT04245111.
• Registry record last updated 2024-09-19; status last verified 2024-05.
• Results first posted 2024-09-19.
• 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

NCT04245111, titled “ICG Fluorescence Imaging in Trauma Patients,” is listed as completed and sponsored by Dartmouth-Hitchcock Medical Center. It is described as a prospective observational pilot and feasibility study, with registry enrollment of 20. The study dates are 2019-05-16 for start and 2021-11-23 for primary completion.

The primary outcome is the percentage of patients successfully completing the protocol over 1 year. The stated broader aim is to measure bone and soft-tissue perfusion using quantitative ICG fluorescence and examine its relationship to complications. Three cohorts are listed: Open Fracture, Complication, and Closed Fracture.

The registry record does not report the primary outcome result, perfusion findings, or analyses of the stated complication relationships. It records serious and other adverse-event counts by cohort, with 0 deaths listed in each. The available entries support a description of the study design and reporting, but not a conclusion about the unreported feasibility or perfusion results.