Retrospective Study Chimaera Long Nail in Adult Patient: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Retrospective Study Chimaera Long Nail in Adult Patient (NCT06285981), a registered phase not stated study. The primary outcome is Percent of Patients in Which Bone Union Has Been Achieved.

2. Clinical Question

3. Trial Design

The registry record identifies this as a retrospective observational study of the Chimaera Long Nail in adults with pertrochanteric, intertrochanteric or subtrochanteric fractures of the femur. Its stated purpose was to assess the device’s clinical benefit and safety profile in daily practice. The study is marked completed. The record gives a start date of 2023-11-27 and a primary completion date of 2024-12-17.

The record reports an enrollment of 44. It describes a patients-with-femur-fractures group and names the Chimaera Long Nail as the intervention. A separate control group or comparator is not described, and allocation is not stated. The registry record therefore does not support interpreting the study as a randomized, controlled comparison or as a like-for-like comparison between arms.

The primary outcome was the percentage of patients in whom bone union was achieved within 12 months from nail implantation. The listed secondary outcome was the percentage of patients that required a reoperation. Although two outcome measures are recorded, the registry record does not report their results or any analyses.

For the performance endpoint, 42 of the enrolled patients were analysed. The record says two did not meet the CIP criteria for primary-endpoint evaluation and were excluded from the efficacy analysis, while remaining included in the safety evaluation. This difference in analysis populations matters: the endpoint result, if reported, would describe the specified performance population rather than automatically applying to everyone enrolled or assessed for safety.

The registry record does not report a protocol-level statistical analysis plan, a sample-size justification, or a detailed account of how retrospective observations were collected. Those details should not be inferred from the completed status or the endpoint description.

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

Analysis population for the primary outcome, as defined in the registry: Only 42 out of 44 enrolled patient were analysed for the performance endpoint because Two patients did not meet the CIP criteria for the primary endpoint evaluation and were not included in the efficacy analysis of clinical benefit, but were included in study evaluation for safety.

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 in Which Bone Union Has Been Achieved, measured over 12 months.

The primary endpoint is the percentage of patients in whom bone union was achieved within 12 months from nail implantation. It is a binary outcome at the participant level: for the endpoint, each evaluated patient is classified according to whether bone union was achieved within the stated timeframe. The registry record labels the unit as participants and the parameter as a count of participants, while its endpoint description expresses the intended measure as a percentage.

Bone union is used as a measure of clinical benefit after treatment of the specified femur fractures. In general, a clearly defined clinical endpoint helps connect an assessment to a patient-level outcome and a stated follow-up period. A percentage can describe how often the endpoint occurred in the analysed population, but the estimate is most useful when its denominator, outcome definition and uncertainty are also clear.

The registry record gives the timeframe and explains that 42 patients were included in the performance analysis because two did not meet the CIP criteria. It does not report the number who achieved union, the resulting percentage, or an interval expressing uncertainty. Therefore, the endpoint’s observed frequency and precision are not reported in the registry record. The secondary outcome concerning reoperation is listed, but its result is also not reported.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a retrospective observational study and defines a participant-level binary primary endpoint: bone union achieved within 12 months from nail implantation. A binary endpoint has two possible classifications for each evaluated participant, such as achieving or not achieving the specified outcome within the assessment window. This makes a count and a proportion natural descriptive summaries. The registry record does not report either summary for the primary endpoint.

What does a percentage describe?

In general, a percentage for a binary endpoint describes the share of the analysed population meeting the endpoint definition. Its interpretation depends on a clearly defined numerator, denominator, endpoint rule and follow-up window. Here, the record specifies the 12-month window and says 42 patients were analysed for performance. It does not report how many achieved bone union, so the endpoint percentage cannot be recovered from the record and should not be inferred.

The two patients excluded from the efficacy analysis did not meet the CIP criteria for primary-endpoint evaluation. The record says they were included in the safety evaluation. This is an analysis-population distinction rather than a reported endpoint result. In general, excluding participants from an efficacy denominator can affect how representative an estimate is of all enrolled participants. Assessing that issue requires knowing the exclusion criteria, why those criteria applied, and what outcome information was available for excluded patients. Those details and any sensitivity analyses are not reported in the registry record.

How should uncertainty be assessed?

In general, a confidence interval describes the uncertainty around an estimate under the assumptions of the statistical method used. For a binary outcome, an interval around a proportion can help readers distinguish a precise estimate from one that remains compatible with a broad range of underlying event frequencies. The registry record does not report a confidence interval for bone union, nor does it state a method for calculating one. No interval should be reconstructed without the endpoint count and a specified analysis approach.

A p-value, in general, addresses how compatible observed data are with a specified statistical model or null hypothesis. It is not a measure of clinical importance, and it does not by itself describe the size or precision of an effect. The registry record lists no analyses and reports no p-value for the primary endpoint. Because no comparator is specified, a between-group test should not be presumed.

What does the planning illustration represent?

The sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two hypothetical arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. These are planning assumptions, not evidence that the study itself used that design. The registry record does not report a randomized two-arm comparison, a sample-size justification, or the calculated planning results. Any sample-size figures should therefore be read as planning illustrations, not observed power and not as analyses of this observational cohort.

In general, an observed effect used in a planning exercise is an estimate from data and may itself be uncertain. Planning for a fraction of that effect explores how a future study might be sized under chosen assumptions; it does not establish that the effect is real, clinically important or expected to recur. The illustration’s assumptions cannot substitute for a prespecified design or an analysis plan.

Why does study design limit causal interpretation?

In general, retrospective observational studies use information arising outside a randomized allocation process. Differences in patient characteristics, clinical decisions, follow-up and outcome recording can influence observed results. Randomization, when used, is intended to balance measured and unmeasured factors on average between comparison groups; this record does not describe randomization or a comparator. It is therefore appropriate to describe the study’s outcomes as observations in its evaluated population, not as a causal estimate against an alternative treatment.

The record does not state the statistical methods used to address confounding, how missing observations were handled, or whether any adjusted analysis was performed. It does not report uncertainty estimates, hypothesis tests or sensitivity analyses. These omissions mean that the statistical precision and robustness of the primary endpoint cannot be assessed from the registry record. General statistical concepts can explain what such analyses would address, but they do not establish that any were conducted in this study.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Patients With Femur Fractures")
n      <- c(42)
events <- c(42)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Patients With Femur Fractures  42  42  100.0  91.6  100.0  91.6  100.0  91.8  99.9

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists two outcome measures: the primary endpoint of bone union within 12 months and a secondary outcome concerning the percentage of patients requiring reoperation. It reports no results for either outcome and lists no analyses. A multiplicity strategy—how statistical error is managed when several outcomes or tests are considered—is not reported in the registry record. It is therefore not possible to determine whether outcomes were tested, whether any adjustment was planned, or how any inferential findings would have been prioritized.

In general, examining multiple outcomes or performing multiple tests can increase the chance of findings that appear notable by chance. Prespecified priorities and an analysis plan help readers understand which results were primary and how secondary findings should be interpreted. The primary endpoint is identified in the record, but the statistical plan for handling the listed outcomes is not reported.

The record identifies a performance population of 42 patients and states that two did not meet the CIP criteria for primary-endpoint evaluation. It says these patients remained included in the safety evaluation. This explains an exclusion from the efficacy analysis but does not describe missing-data handling among the analysed patients, the completeness of follow-up, or whether sensitivity analyses were performed. Those details are not reported in the registry record.

In general, missing-data methods depend on why information is absent and on the analysis objective. Excluding cases, imputing values and conducting sensitivity analyses involve different assumptions; none should be attributed to this study without documentation. The registry record does not report the relevant methods or assumptions. Thus, the effect of incomplete endpoint information on the reported results cannot be assessed, and no primary or secondary efficacy result is available to interpret.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: deep infection (2.3%), fracture (2.3%).

The registry record reports safety information for the Patients With Femur Fractures group. It gives 44 patients at risk, 2 affected by serious adverse events, and 0 deaths. The top serious terms listed are deep infection at 2.3% and fracture at 2.3%. These are the safety figures reported in the registry record; they should be read as descriptive information about the study group.

The percentages are reported alongside event terms, but the record does not provide further detail about event timing, severity beyond the serious classification, attribution to the device, or whether a patient could contribute to more than one term. The figures do not establish that the device caused the events. They also do not provide a comparative safety estimate because no comparator is specified.

In general, safety interpretation benefits from clear definitions, follow-up duration, event ascertainment procedures and context about the population being monitored. These details are not reported in the registry record beyond the stated group and counts. The two patients excluded from efficacy analysis were included in the safety evaluation, according to the record. Safety counts should not be substituted for the unreported bone-union endpoint or interpreted as evidence about comparative benefit.

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

The registry record establishes what the study set out to assess: clinical benefit and safety of the Chimaera Long Nail in adults with pertrochanteric, intertrochanteric or subtrochanteric femur fractures in daily practice. It defines bone union within 12 months as the primary endpoint and names reoperation as a secondary outcome. It also reports selected safety counts. Those details describe the study question and some observed safety information, but the primary and secondary outcome results are not reported in the registry record.

As a result, the record does not provide the observed percentage achieving bone union, the number requiring reoperation, or uncertainty around either outcome. The completed status does not supply those missing estimates. Readers cannot determine from this record how frequently the primary endpoint occurred in the performance population or how precise that estimate would be.

The observational design and absence of a specified comparator also limit what can be concluded. In general, outcomes in a single group describe what occurred among evaluated participants; they do not show what would have happened under another treatment. Without a reported comparison and relevant methods, an outcome cannot be attributed to the device alone or used to estimate its relative effect.

The reported safety information consists of 2 serious adverse events among 44 patients at risk, 0 deaths, and the listed serious terms deep infection and fracture, each reported at 2.3%. These data do not establish causation or comparative safety. They also cannot resolve the unreported primary endpoint.

The appropriate reading is therefore limited: the record identifies a completed retrospective study, its target population, device, endpoint definitions, efficacy analysis population and selected safety figures. It does not report enough outcome or analysis detail to quantify the primary clinical result or support a comparative treatment conclusion.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of the difference between a clearly stated endpoint and a reported endpoint result. The record defines bone union within 12 months as the primary outcome and identifies a performance analysis population of 42 patients. Yet it does not report the number achieving union or a percentage. Without those values, readers cannot assess the observed frequency or its precision, regardless of how clearly the question is framed.

The distinction between efficacy and safety populations is also important. The record says two patients did not meet the CIP criteria for primary-endpoint evaluation and were excluded from the efficacy analysis, while remaining in the safety evaluation. Such population definitions determine which participants contribute to a particular estimate. Transparent reporting of eligibility, exclusions and endpoint availability helps readers judge how well an estimate represents the enrolled group.

The retrospective observational design makes comparator and confounding questions central. The registry record does not specify a comparator or allocation method. General statistical reasoning therefore cautions against interpreting an outcome in this cohort as a comparative treatment effect. Descriptive outcomes and causal contrasts answer different questions, and the latter require an appropriate comparison and supporting design and analysis.

The record also illustrates why a planning calculation should be kept distinct from a trial’s actual design and results. The stated planning assumptions describe a hypothetical equal-allocation comparison, while the recorded study is observational and has no specified comparator. Planning illustrations can inform future research under their assumptions; they are not observed power and do not fill gaps in outcome reporting.

Finally, the safety counts are useful as descriptive record entries but have limited interpretive reach without event context, attribution and a comparator. Taken together, these features make completeness of outcome reporting, clarity of analysis populations and alignment between design and statistical claims especially important.

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.

Several trial-specific limitations follow directly from what the registry record reports and omits. The study is retrospective and observational, and the record does not state an allocation method or identify a comparator. It therefore does not describe a controlled comparison from which a relative treatment effect could be estimated. The extent to which clinical or patient characteristics may have influenced treatment and outcomes is not reported.

The primary endpoint result is not reported in the registry record. Although bone union within 12 months is defined and the performance population is described, the number achieving union and the corresponding percentage are absent. The secondary reoperation outcome is listed without a reported result. The record lists no analyses, and it does not report confidence intervals, hypothesis tests, adjusted estimates or sensitivity analyses.

The performance endpoint excluded two patients who did not meet the CIP criteria, while those patients remained included in the safety evaluation. The record does not provide further detail on the criteria, the reasons they were not met, follow-up completeness, or the potential effect of the exclusions on the efficacy estimate. Missing-data procedures are not reported.

Safety reporting is also limited in context. The registry record reports serious-event counts, deaths and two serious terms, but does not give further information about attribution, timing or event ascertainment. No comparative safety analysis is reported. The sample-size assumptions describe a planning illustration rather than a documented justification for this observational study, and calculated planning results are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Retrospective Study Chimaera Long Nail in Adult Patient — NCT06285981.
• Registry record last updated 2025-09-15; status last verified 2025-09.
• Results first posted 2025-08-07.
• 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

The registry record describes a completed retrospective observational study of the Chimaera Long Nail in adults with pertrochanteric, intertrochanteric and subtrochanteric femur fractures. It reports enrollment of 44 and identifies bone union within 12 months as the primary endpoint. The performance analysis included 42 patients; two who did not meet the CIP criteria were excluded from efficacy evaluation but included in safety evaluation.

The primary and secondary outcome results are not reported in the registry record, and no analyses are listed. Safety reporting includes 2 serious adverse events among 44 patients at risk, 0 deaths, and deep infection and fracture, each listed at 2.3%. No comparator is specified. Consequently, the record describes the study question and selected safety information but does not provide a primary efficacy estimate or a comparative treatment result.