Ropivacaine Versus Bupivacaine as Preemptive Analgesia in Surgical Site in Ankle Fracture Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Ropivacaine Versus Bupivacaine as Preemptive Analgesia in Surgical Site in Ankle Fracture Patients (NCT02949674), a randomized phase 3 study. The primary outcome is VAS.

2. Clinical Question

The clinical question concerns preventive local infiltration at the surgical incision in patients undergoing ankle-fracture surgery. The record says traditional anesthesia was also to be used, but does not provide further details about that anesthesia or the care surrounding surgery.

The distinction between the listed comparison and the study arms matters for interpretation. The brief summary describes patients being assigned to ropivacaine or bupivacaine, while the arm descriptions include a Control group as well. The registry record does not clarify whether the control group was part of the randomized comparison, how the groups were assigned, or which group comparisons were prespecified for the primary question. The endpoint result and its statistical analysis are not reported in the registry record.

3. Trial Design

The registry record describes a randomized, single-masked, parallel trial and identifies its phase as Phase 3. Enrollment is recorded as 93. The trial status is completed. Its start is recorded as 2016-09 and its primary completion as 2016-10; these dates describe the registry fields and do not establish when each participant was assessed.

The brief summary describes assignment to ropivacaine or bupivacaine before surgery. The intervention descriptions specify ropivacaine 37.5 mg and bupivacaine 25 mg at the surgical site, each given at least 10 minutes before skin incision. A Control arm is separately listed, with no anesthetic applied. The registry record does not explain how this control arm relates to the two-group assignment described in the summary, or identify which comparison was intended as the primary contrast.

Random allocation is intended, in general, to reduce systematic differences between groups at assignment. A parallel design means that assigned groups are compared rather than participants crossing between the interventions. The record states single masking but does not identify who was masked or how masking was maintained. Those details are not reported in the registry record.

The sponsor is Instituto Mexicano del Seguro Social. The record does not report the randomization procedure, allocation concealment, protocol deviations, adherence to the assigned infiltration, or the number of participants analyzed for the primary endpoint. It also does not give a sample-size justification or explain whether the enrollment was based on a prespecified statistical calculation. The posted enrollment field should therefore not be read as proof that every enrolled participant received an intervention or contributed endpoint data.

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 VAS, measured over Change in Visual Analogue Scale at 24 hours.

The primary endpoint is described as change in the Visual Analogue Scale at 24 hours after surgery. The scale is described as ranging from 0, meaning no pain, to 10, meaning the worst pain possible. Pain was to be assessed according to the investigator. The registry record identifies the measure as a mean with standard deviation and expresses it in units on a VAS scale.

A pain scale provides a way to record a subjective experience in a form that can be compared across groups. In general, a continuous scale can be summarized by its mean, while its standard deviation describes the spread of individual scores around that mean. A mean difference between groups can describe the average contrast, but a complete interpretation also depends on uncertainty, participant-level variation, and how the endpoint was measured.

The word “change” implies a comparison between measurements over time, but the registry record does not report the baseline measurement or specify how change was calculated. It also does not report a group mean, standard deviation, between-group estimate, confidence interval, or test result. The endpoint description alone therefore explains what was intended to be measured, not what the trial found.

The registry record notes that the primary outcome has several categories or time points and was not reduced to one comparison. The outcome is consequently not available as a single analyzable result in the posted record. Details such as the exact assessment procedure, handling of missing scores, and the assessment population are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a continuous primary measure: VAS change at 24 hours, summarized as a mean and standard deviation. In general, a mean describes the average score in a group. A standard deviation describes how dispersed individual observations are around that average; it is not the uncertainty in the estimated mean and is not a confidence interval. The record does not include the group means or standard deviations, so neither the average scores nor their variability can be examined.

What would a group comparison estimate?

In general, a comparison of group means estimates how far apart the average outcomes are for the groups being compared. The direction depends on the order used for the contrast, so an estimate must be interpreted alongside its definition and the scale's meaning. For a change score, interpretation also depends on whether the analysis compares average changes directly or adjusts for baseline scores. The registry record does not specify the calculation of change, identify a model, or report a group contrast.

A confidence interval is a range of values compatible with the data under a statistical model and its assumptions. It communicates uncertainty around an estimate; a narrow interval generally indicates more precision than a wide interval. A confidence interval is not reported for the primary endpoint. Without an estimate and interval, the record cannot show either the likely direction of the group contrast or how precisely it was estimated. A p-value, which measures compatibility between data and a specified null model under its assumptions, is also not reported. Neither a test result nor its interpretation can be reconstructed from the endpoint description alone.

Why do analysis details matter?

In general, an analysis plan defines the outcome, comparison, analysis population, and statistical model before results are assessed. These choices affect what the estimate means. For example, an analysis of all participants according to assigned group addresses a different question from an analysis restricted to those who received the planned intervention. The registry record does not report the primary analysis population, the handling of participants who did not follow the assigned intervention, or the statistical model.

The trial is described as randomized, single-masked, and parallel. Randomization can help balance measured and unmeasured prognostic characteristics between groups in expectation, but the record does not report its sequence-generation method or allocation concealment. “Single-masked” does not identify which people were masked. These design labels do not tell readers whether masking was successful or whether the groups remained comparable throughout follow-up.

The listed arms create an additional interpretive issue: the brief summary describes assignment to ropivacaine or bupivacaine, but the arm descriptions include a control group with no anesthetic. The registry record does not explain the allocation of this control group or specify the primary contrast. A statistical comparison must refer to identifiable groups; the record does not make that comparison clear enough to interpret an endpoint estimate.

What do the planning assumptions mean?

In general, a sample-size calculation estimates how many observations would be needed to detect an assumed effect with specified statistical properties. The registry states that its planning illustration uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also says the effect to detect is a stated fraction of the observed effect. These are assumptions for a planning illustration, not evidence about the trial's actual design or its statistical analysis.

A planning illustration based on an observed effect is especially dependent on that effect estimate. If the endpoint result is not available as an analyzable comparison, the illustration cannot be assessed against a verifiable trial estimate from the registry record. A calculated sample size is not “observed power,” and it does not establish that the trial was adequately powered. The record does not report its own sample-size justification, the effect size used for its design, or any prespecified power target.

Equal allocation between two arms also does not describe the listed three-group structure without further information. The record does not state whether the planning calculation concerns only an active-treatment comparison, whether it is applicable to the control group, or whether another allocation was used in the trial. No numerical sample-size illustration is reported in the registry record for this explanation, so there is no planning result to interpret.

What cannot be recovered from the registry entry?

The registry record does not report a statistical analysis plan, primary endpoint estimates, uncertainty intervals, test statistics, or p-values. It does not describe the handling of missing observations, multiplicity, baseline adjustment, distributional assumptions, or sensitivity analyses. General statistical concepts can explain why these choices matter, but cannot determine which approach the investigators used. No method should be attributed to the trial unless it is documented in the registry record.

For continuous outcomes, assumptions about the distribution and the way scores are summarized can affect the appropriateness of a mean-based analysis. In general, unusual skew or influential observations can make a mean less representative of typical responses, while over-dispersion can make a model that assumes less variability understate uncertainty. These are general considerations, not findings about this trial: the registry record supplies no participant-level outcome distribution or diagnostic assessment.

The endpoint is described as a change score, but no baseline data or operational definition of change is given. In general, analysis of follow-up scores adjusted for baseline and analysis of change scores can yield different estimates and precision. Without the specified method and the underlying data, neither can be reproduced. The registry record also does not report whether the investigator assessment was made using a standardized procedure or whether assessors knew group assignment.

10. Multiplicity, Missing Data and Analysis Populations

The registry record does not report how multiplicity was handled. It notes that the primary outcome has several categories or time points and was not reduced to one comparison. When multiple outcomes, time points, or group contrasts are examined, the chance of at least one apparently notable result can increase. In general, a prespecified strategy can define which comparisons are confirmatory and whether any adjustment or hierarchy is used. No such strategy is reported in the registry record, and the note does not identify which category, time point, or contrast was intended to carry the primary inference.

Missing-data handling is also not reported in the registry record. The enrollment field is 93, but the record does not state how many participants contributed VAS measurements at 24 hours, whether any scores were unavailable, or how missing measurements were handled. Enrollment should not be assumed to equal the endpoint analysis population. In general, excluding participants with missing outcomes, imputing values, or using a model that accommodates incomplete observations relies on different assumptions. The registry does not identify which, if any, approach was used.

The analysis population is not reported in the registry record. It is therefore unclear whether the intended analysis followed randomized assignment, included only participants who received the specified infiltration, or used another definition. The record also does not describe protocol deviations, withdrawals, or sensitivity analyses. These gaps limit interpretation of both the endpoint and the safety counts.

Because the endpoint result is not available as a single comparison, multiplicity and missing-data concerns cannot be resolved by examining an estimate. They remain reporting limitations rather than evidence that a particular analysis choice was made.

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.

The registry reports safety counts separately for Bupivacaine, Ropivacaine, and Control. For each group, 31 participants are listed as at risk for serious adverse events, with 0 affected. For each group, 31 are also listed as at risk for other adverse events, with 0 affected, and deaths are recorded as 0. These are the registry's posted counts; they are not a comparison adjusted for differences between groups.

A zero count in a registry entry means no events are recorded in that category for the stated group. In general, it does not prove that the true risk is zero. Interpretation depends on how adverse events were defined, how actively they were collected, the period of observation, and whether reporting was complete. The registry record does not report those details or provide uncertainty intervals for the safety counts.

The counts should not be read as establishing that the groups had identical safety experience. The record does not explain whether the same follow-up and ascertainment procedures were used in each group or how participants who were not observed for the full period were handled. The listed counts are therefore a limited description of recorded events, not a comprehensive safety comparison.

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

The registry record establishes that the study was described as a randomized, single-masked, parallel Phase 3 trial of local anesthetic applied before ankle-fracture surgery. It identifies ropivacaine and bupivacaine doses and specifies a VAS pain measure at 24 hours. It also lists a control group without local anesthetic. These details describe the study question and intended approach, but do not supply the outcome results needed to answer the question.

The primary endpoint is not reported as an analyzable comparison. There is no group-level VAS result, estimate of the difference, confidence interval, or test result. The record therefore does not show whether one group had a higher or lower average score, how large any contrast was, or how precise an estimate might be. No conclusion about the pain outcome can be drawn from the trial status, design labels, intervention doses, or endpoint definition alone.

The listed control arm and the two-group assignment in the brief summary are not reconciled. Consequently, the intended primary comparison is unclear from the registry record. A reader should not assume that the active interventions were compared with each other, that either was compared with control, or that all listed groups contributed to one analysis.

The safety entries report zero serious adverse events, zero other adverse events, and zero deaths in each listed group, with 31 participants at risk for each adverse-event category in each group. These entries describe recorded counts only. They do not establish absence of risk, equivalence, or a broader safety profile because definitions, follow-up, and reporting completeness are not described.

In general, trial results are most informative when the prespecified comparison, analysis population, effect estimate, and uncertainty are reported together. Those elements are not available in the registry record for the primary endpoint. This limits what can be inferred from the entry; it does not establish that no analyses or results existed outside the registry.

13. Why This Trial Matters Statistically

The trial raises a useful statistical question: whether pain scores after ankle-fracture surgery differ according to the local anesthetic applied before incision. The registry record gives details about the intended endpoint and interventions, allowing readers to understand the type of comparison that was planned. It also illustrates why an outcome definition alone is not enough to interpret a clinical trial statistically.

For a continuous pain scale, readers need the group summaries and a clearly defined contrast to understand the magnitude and direction of an average difference. Uncertainty is also essential: a confidence interval conveys how precisely the contrast is estimated, while a test result addresses compatibility with a specified statistical model. Neither endpoint estimates nor inferential results are reported in the registry record. The central statistical question therefore remains unanswered by the posted outcome information.

The entry also demonstrates the importance of consistent descriptions of study groups. The summary describes assignment to the two active anesthetics, while the arm descriptions include a control group receiving no anesthetic. Without an explanation of allocation and the intended primary comparison, the group structure cannot be translated into a clear estimand—the specific treatment contrast the analysis is meant to quantify.

Finally, the registry notes that the primary outcome includes several categories or time points but does not reduce them to one comparison. Prespecification and transparent reporting help distinguish a primary inference from exploratory comparisons and make multiplicity easier to assess. The record does not report the relevant analysis details. These issues matter not because they prove a particular bias or result, but because they define the limits of what readers can conclude from the registry entry.

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 direct limitation is that the primary VAS outcome is not available as a single analyzable comparison. The record identifies a change in VAS at 24 hours but supplies no group means, standard deviations, contrast estimate, confidence interval, or test result. It also notes that the outcome has several categories or time points and was not reduced to one comparison. The direction, size, and precision of any pain-score difference therefore cannot be assessed.

The group descriptions are not fully consistent. The brief summary describes assignment to ropivacaine or bupivacaine, whereas the intervention descriptions also list a Control group with no anesthetic. The registry record does not explain the control group's role, the allocation scheme, or the primary contrast. This makes the planned comparison uncertain.

The record does not report participant characteristics, the endpoint analysis population, endpoint completion, missing-data handling, or protocol deviations. It does not explain how change was calculated or give a baseline VAS value. The masking field does not identify who was masked. These reporting gaps prevent assessment of how closely the recorded study conduct matches the intended design.

For safety, the registry gives event counts but not definitions, follow-up duration, collection procedures, or completeness. The counts cannot be interpreted as a comprehensive comparison of harms. The record also does not provide the trial's statistical analysis plan, multiplicity strategy, sample-size justification, or sensitivity analyses. These limitations concern what is reported in the registry; they do not establish that the trial did or did not collect additional information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Ropivacaine Versus Bupivacaine as Preemptive Analgesia in Surgical Site in Ankle Fracture Patients — NCT02949674.
• Registry record last updated 2018-12-31; status last verified 2017-09.
• Results first posted 2018-12-31.
• 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

NCT02949674 is a completed, randomized, single-masked, parallel Phase 3 trial sponsored by Instituto Mexicano del Seguro Social. The registry lists enrollment as 93 and describes surgery for ankle fractures. Ropivacaine 37.5 mg or bupivacaine 25 mg was to be applied at the surgical site at least 10 minutes before skin incision. A Control arm is also listed, described as receiving no anesthetic.

The primary endpoint is change in VAS at 24 hours after surgery, with pain assessed on a scale from 0 to 10. The registry record does not report a single analyzable endpoint comparison, and the outcome result, statistical analysis, and analysis population are not reported. For each listed group, the safety record lists 31 at risk and 0 affected for serious adverse events, 31 at risk and 0 affected for other adverse events, and 0 deaths.