An Imaging Framework for Clinically Testing New Treatments to Prevent Post-traumatic OA: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for An Imaging Framework for Clinically Testing New Treatments to Prevent Post-traumatic OA (NCT03809520), a na na study. The primary outcome is Changes in the Ankle Joint Space Width Between Baseline and Final Follow-up.

2. Clinical Question

3. Trial Design

The registry classifies this completed study as a single-group study with no allocation and no masking. Its listed intervention is pedCAT, a weight-bearing CT imaging procedure. The record does not describe a randomized treatment comparison, and the registry lists the study phase as NA. Enrollment is listed as 97; the record does not clarify in the material available for this analysis how many participants contributed data at each visit or to the primary endpoint.

The experimental group description specifies imaging at 6 months, 12 months, and 18 months after ankle injury. It also says that additional funding extended follow-up for subjects initially enrolled under OTA funding, with yearly follow-up through 5 years after injury. The primary outcome description defines final imaging as at 18 months or at 5 years. This indicates that final observations could arise at different follow-up times; the registry does not explain how those timing differences were handled analytically.

The main research purpose is to test a low-cost, low-dose standing CT system for early detection of joint degeneration and elevated contact stress. A secondary purpose is to enable predictive models of osteoarthritis risk using post-treatment contact-stress measures, with the aim of informing treatment and risk-stratified testing of future interventions. These are stated aims, not findings. The record does not report a statistical analysis, a model result, or a conclusion about imaging performance.

The contralateral, uninjured ankle is identified as a control for the joint-space-width assessment. This reference can help contextualize a participant’s injured-side measurement, but does not create a randomized or independently recruited control group. The registry record does not report further details about measurement procedures, assessor blinding, or participant flow.

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:

Analysis population for the primary outcome, as defined in the registry: joint space width, minimum value

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 Changes in the Ankle Joint Space Width Between Baseline and Final Follow-up, measured over Final imaging assessed at 18 months or up to 5 years post-injury.

The primary endpoint is change in ankle joint-space width between baseline and final follow-up. It is measured in millimeters using three-dimensional pedCAT imaging, and the registry identifies the minimum joint-space-width value as the measure of interest. The outcome is described as a mean with standard deviation. The contralateral, uninjured side is named as the control reference for tracking the longitudinal imaging measure.

Joint-space width is a structural imaging measure. In general, repeated measurements can describe whether an anatomical feature changes over time, while a comparison with an uninjured side can provide a reference within the same person. These functions help explain why such a measure may be useful in research on joint degeneration; they do not establish that a change in the measure predicts symptoms or future disease in this study.

The registry gives the endpoint timeframe as final imaging at 18 months or up to 5 years post-injury. It does not report the baseline or final means, the standard deviation, the estimated change, a confidence interval, or a test of the change. It also does not report a clinically meaningful threshold for interpreting a difference in millimeters. Consequently, the endpoint definition is available, but its observed magnitude and precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods information in the registry record is limited. It identifies a single-group design, no allocation, no masking, a continuous primary outcome summarized as a mean with standard deviation, and no recorded analyses. It does not describe a statistical model or provide an estimate. The concepts below are general explanations of how such methods are ordinarily interpreted, not claims about analyses performed in this study.

What does a mean with standard deviation describe?

For a continuous outcome such as joint-space width, the mean describes the central level of measurements in the analyzed observations. The standard deviation describes how spread out those measurements are around the mean. They answer different questions: the mean concerns the average measured value, while the standard deviation concerns variability among measurements. Neither quantity is reported numerically for this endpoint in the registry record.

A mean change can summarize the average within-person movement between baseline and a later measurement, if the analysis uses paired observations. But the registry does not specify the exact calculation, the participants included, or whether the endpoint was analyzed as paired change, as separate time-specific measurements, or with another approach. It would therefore be inappropriate to infer a particular analysis from the outcome title alone.

Why is the comparator structure important?

A single-group study does not assign participants to competing treatment arms. The uninjured contralateral side is described as a control for the imaging measure, but this is a reference within the outcome definition, not a separately allocated arm. In general, paired comparisons can account for some characteristics shared by measurements from the same person. They do not by themselves resolve every possible source of bias, and they do not provide the same design protections as randomized allocation between groups.

The record does not report whether the injured and uninjured sides were measured using a prespecified paired analysis, how side-to-side differences were modeled, or how measurement variability was assessed. It also does not report a method for handling the different final follow-up times. These omissions limit what can be said about the assumptions behind any potential comparison.

What would a confidence interval add?

In general, a confidence interval gives a range of values compatible with the data under a specified statistical procedure and its assumptions. It helps show precision: a more concentrated interval indicates greater precision, while a wider interval indicates more uncertainty. A point estimate alone does not show that uncertainty. The registry record reports no confidence interval for the primary outcome, so precision cannot be evaluated from the posted results.

A p-value, when reported, addresses how compatible the data are with a specified null model under the chosen analysis. It does not measure the size or practical importance of an effect. No p-value or inferential test is reported for the primary endpoint. More generally, statistical significance would not by itself establish that an imaging difference is clinically meaningful; that requires an appropriate interpretive benchmark, which is not reported in the record.

How should sample-size planning be read?

The registry’s planning description characterizes sample-size illustrations as based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says that the target effect is a stated fraction of the observed effect, and that non-time-to-event planning values are expressed as participants per arm. These are planning assumptions, not a report of the study’s actual design: this study is registered as single-group with no allocation. The record does not report the observed effect used for the illustration or numerical planning counts in the information available for this analysis.

In general, sample-size planning estimates the amount of information a future study might need under chosen assumptions. Such estimates are not observed power, and they do not show that the current study had a particular probability of detecting an effect. Planning based on an observed effect also depends on that estimate and the assumptions used. No sample-size justification for the study itself is reported in the registry record.

Why can measurement and follow-up choices matter?

General measurement error can make repeated values less stable and obscure whether a true change occurred. Three-dimensional weight-bearing imaging is the stated approach in this study, but the registry does not report repeatability estimates, quality-control procedures, or reader agreement. General statistical methods may account for repeated observations and differing follow-up times, but no such model is described. The registry record also does not report interim analyses, a prespecified analysis plan, adjustment for multiple outcomes, or handling of missing data. Without those details and the outcome estimates, the statistical evidence cannot be independently characterized.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Experimental: pedCAT")
n   <- c(70)
m   <- c(0.912)
sp  <- c(0.492)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Experimental: pedCAT  70  0.912  0.492  0.795  1.029

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures, including the primary joint-space-width outcome and secondary outcomes of change in ankle pain and change in ankle function. It does not report how many hypotheses were tested, whether the analyses were prespecified, or whether any adjustment for multiple comparisons was used. In general, testing multiple outcomes can increase the chance of at least one apparently unusual result under a set of null hypotheses. A multiplicity strategy can address that issue, but no such strategy is reported in the registry record.

The record lists zero analyses and does not provide outcome estimates or inferential results. It also does not report an analysis population, the number contributing data at each visit, or a participant-flow account. The enrollment figure cannot establish how many participants had usable baseline and final imaging.

Missing-data methods are not reported in the registry record. This matters because scheduled imaging visits span 6 months, 12 months, and 18 months, while extended follow-up through 5 years is described for subjects initially enrolled under OTA funding. Final follow-up can therefore refer to different timepoints. In general, incomplete visits or unequal observation times may affect which data contribute to an estimate and how that estimate should be interpreted. The record does not say whether missing observations were excluded, imputed, or handled with a longitudinal model.

The record also does not report whether the primary analysis followed a prespecified protocol or how secondary outcomes were related to the primary question. These are reporting gaps, not evidence that a particular method was or was not used outside the registry record.

12. 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 registry lists the experimental pedCAT group as having 97 participants at risk for serious adverse events and 0 affected. It also lists 97 at risk for other adverse events and 0 affected, with 0 deaths. No serious adverse-event terms are listed. These are the registry’s reported counts; they are not an estimate of risk relative to a comparison group, because the study is registered as single-group.

Zero recorded events should be read narrowly. The entries do not by themselves establish that no event occurred outside the recorded reporting scope, nor do they describe event definitions, ascertainment procedures, reporting completeness, or observation time for safety. The record identifies pedCAT as a radiation intervention, but does not provide radiation dose details in the material available for this analysis. It is therefore not possible to assess exposure or compare safety across imaging approaches from these entries.

Safety counts also do not answer the primary imaging question about joint-space-width change. They are separate registry information and should not be interpreted as evidence about the imaging outcome or the performance of predictive models.

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

The registry record establishes that a completed single-group study investigated weight-bearing pedCAT imaging after ankle injury. Its primary outcome was change in minimum ankle joint-space width between baseline and final imaging, with the contralateral, uninjured side identified as a control reference. The planned follow-up description includes imaging at 6 months, 12 months, and 18 months, and extended yearly follow-up through 5 years for some participants.

Those design details do not reveal what the measured change was. The registry record does not report a mean, standard deviation, effect estimate, confidence interval, p-value, or analysis details for the primary endpoint. It therefore cannot support a conclusion about the magnitude or precision of joint-space-width change. It also does not report diagnostic accuracy, evidence that degeneration was detected earlier than with another modality, or predictive performance for osteoarthritis risk.

The stated goals describe intended research contributions: evaluating the standing CT system for early detection and enabling risk-prediction models based on contact-stress measures. Goals are not findings. The record does not report results showing that these goals were achieved, and the single-group imaging design is not a randomized test of a treatment to prevent post-traumatic osteoarthritis.

In general, interpreting an imaging measure as clinically important requires more than knowing its unit or average. Its uncertainty, measurement reliability, relationship to symptoms or later disease, and relevant interpretive thresholds may all matter. Those details are not reported for the primary endpoint in the registry record. Likewise, enrollment does not tell readers how many people contributed to each analysis, and no missing-data approach is described. The appropriate conclusion is that the registry records an imaging study and its intended measurements, but not the quantitative evidence needed to judge the endpoint result or its clinical relevance.

14. Why This Trial Matters Statistically

This study raises statistical questions that are important when evaluating imaging research in orthopedic injury. Its central measurement is longitudinal: joint-space width is to be assessed from baseline to final imaging, with the uninjured side serving as a reference. Repeated measurements can capture change, but interpretation depends on how within-person observations are compared, how measurement variability is handled, and which observations contribute to the estimate. The registry does not report those analytic details or the result.

The follow-up description also illustrates why timing is part of the statistical question. Imaging is specified at 6 months, 12 months, and 18 months, with an extension through 5 years for subjects initially enrolled under OTA funding. The primary endpoint refers to final imaging at 18 months or up to 5 years. Combining or comparing observations across different follow-up times can require clear definitions and methods. Those methods are not described in the registry record.

The study’s broader aims concern early detection and prediction of osteoarthritis risk. In general, a useful prediction model requires evidence about its predictive performance and the population to which it applies; an imaging objective alone does not establish either. The registry record does not report model results, validation, or an analysis of contact-stress measures.

Finally, a single-group imaging study and a randomized treatment trial answer different questions. This record describes imaging follow-up and a structural endpoint, not an assigned intervention intended to prevent osteoarthritis. Recognizing that distinction prevents the study’s title and aims from being mistaken for evidence about treatment efficacy. The study is statistically relevant because it brings together longitudinal measurement, a within-person reference, variable follow-up, and goals for future risk modeling, while leaving the outcome estimates and analysis methods unreported.

15. 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 main limitation for interpreting the posted findings is that the registry record does not include a quantitative result for the primary endpoint. Although it identifies the measure, unit, summary type, and follow-up timeframe, it provides no mean, standard deviation, change estimate, confidence interval, or test result. The record lists zero analyses, so the statistical evidence cannot be reconstructed from the information available.

The study is single-group and has no allocation. The contralateral, uninjured side is described as a control reference, but it is not a parallel randomized comparator. The record does not report participant characteristics, eligibility criteria, baseline outcome values, or how many participants contributed to each follow-up measurement. Enrollment of 97 should not be read as the endpoint sample size.

Follow-up timing is another specific limitation. Imaging is described at 6 months, 12 months, and 18 months, with extended yearly follow-up through 5 years for subjects initially enrolled under OTA funding; the endpoint timeframe is 18 months or up to 5 years. The record does not explain how differing observation times, incomplete visits, or missing endpoint values were handled.

Measurement and analysis details are also absent. The registry does not report reliability or quality-control information for the imaging measure, the precise statistical model, a missing-data method, multiplicity handling, or an analysis population. It does not report results for the secondary pain and function outcomes or predictive models. These limitations concern what can be established from the registry record; they do not establish that unreported procedures were not undertaken.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: An Imaging Framework for Clinically Testing New Treatments to Prevent Post-traumatic OA — NCT03809520.
• Registry record last updated 2026-04-24; status last verified 2025-09.
• Results first posted 2026-04-24.
• 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.

19. Record Summary

NCT03809520 is listed as completed and describes a single-group study of pedCAT weight-bearing CT imaging after ankle injury. Enrollment is listed as 97. The intervention is imaging, and the stated research aims concern early detection of joint degeneration and elevated contact stress, as well as development of osteoarthritis risk models.

The primary outcome is change in minimum ankle joint-space width, measured in millimeters between baseline and final imaging. Final imaging is described at 18 months or up to 5 years after injury, with the contralateral, uninjured side used as a control reference. Secondary outcomes are change in ankle pain and change in ankle function.

The registry lists zero analyses and does not report quantitative outcome results, confidence intervals, or statistical tests. It also does not report an analysis population or missing-data approach. Safety entries list 0 serious adverse events, 0 other adverse events, and 0 deaths in the experimental group. These entries do not provide a comparison with another study arm.