Regional Anesthesia for Major Surgery of the Foot. Levobupivacaïne Ropivacaine 0.5% Versus 0.5% in the Sciatic Block Through médiofémorale: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Regional Anesthesia for Major Surgery of the Foot. Levobupivacaïne Ropivacaine 0.5% Versus 0.5% in the Sciatic Block Through médiofémorale (NCT00956709), a randomized phase 4 study. The primary outcome is Compare the Onset of Action of Ropivacaine 0.5% and levobupivacaïne 0.5 % for Sciatic Nerve Block Guided in Major Surgery of the Foot.

2. Clinical Question

The trial record describes a phase 4 comparison and lists nerve block as the condition. Its rationale was that ultrasound-guided placement might make the comparison between local anesthetics less variable than an approach using a neurostimulator. That is the investigators’ rationale, not a result established by the posted data. The registry record does not report a separate primary question about pain relief, recovery, or clinical outcomes beyond the listed measures.

3. Trial Design

NCT00956709 is recorded as a randomized, parallel-group trial with no masking. The registry lists phase 4, an enrollment of 35, Nantes University Hospital as sponsor, and a status of terminated. The recorded start is 2008-12 and the primary completion is 2011-11. The reason the trial was terminated is not reported in the registry record.

The two groups received levobupivacaïne 0.5% or ropivacaïne 0.5% for sciatic nerve block. The primary outcome was the onset of action in minutes. The record reports a median of 40.0 with a full range from 15.0 to 60.0 for levobupivacaïne, based on 16.0 participants, and a median of 35.0 with a full range from 10.0 to 60.0 for ropivacaïne, based on 19.0 participants. The record notes that two patients in each group had an incomplete block before surgery; it does not explain how this fact related to the analysis population.

Three secondary outcomes are listed: relative position of the tibial and common fibular components in the sciatic nerve, duration of motor sciatic block, and duration of sensory sciatic block. The record also lists four outcome measures and three analyses. The arm descriptions are empty, and further details of recruitment, allocation concealment, the ultrasound procedure, and follow-up are not reported in the registry record. These gaps limit how fully the conduct of the trial can be reconstructed from the registry entry.

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: Two patients in each group had incomplete block before surgery.

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 Compare the Onset of Action of Ropivacaine 0.5% and levobupivacaïne 0.5 % for Sciatic Nerve Block Guided in Major Surgery of the Foot, measured over 72 hours.

The primary endpoint is the onset of action of the sciatic nerve block. It is measured in minutes, so it describes the elapsed time until the block reaches the endpoint used by the investigators. The registry record does not define the specific clinical criterion used to decide that the block had taken effect. It lists a timeframe of 72 hours, but does not explain how that timeframe relates to the measurement of onset.

Onset is relevant to this comparison because the investigators’ stated hypothesis concerned whether levobupivacaïne would have a better onset result than ropivacaïne. Measuring the same outcome in both randomized groups allows a comparison of the recorded distributions. The registry reports the outcome as a median and full range rather than a mean and standard deviation. A median describes the central ordered observation; the full range gives the lowest and highest recorded values. Neither summary shows the shape of all observations or how values are distributed between the endpoints of the range.

The posted medians are 40.0 minutes for levobupivacaïne and 35.0 minutes for ropivacaïne. Their full ranges are 15.0 to 60.0 minutes and 10.0 to 60.0 minutes, respectively. These summaries describe the observed groups; they do not, by themselves, establish whether a difference is distinguishable from random variation or how precisely the group comparison is estimated. The registry record does not report a confidence interval for the comparison or a more detailed definition of the endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Why report a median and full range?

The median is the middle value when observations are ordered. It is a useful summary when an outcome may be skewed or when a typical value is more informative than an arithmetic average. The full range reports the smallest and largest observed values. It conveys the span of the data, but not how many observations lie near either endpoint or how values are distributed within that span. In this trial, onset is summarized with a median and full range for each group. The registry does not provide individual observations, an interquartile range, or another description of the distribution.

For levobupivacaïne, the reported median is 40.0 minutes and the full range is 15.0 to 60.0 minutes. For ropivacaïne, the reported median is 35.0 minutes and the full range is 10.0 to 60.0 minutes. These group-level descriptions do not themselves quantify uncertainty about the contrast. A difference between reported medians is not the same quantity as a treatment-effect estimate from a model, and the registry does not report a confidence interval for a difference in medians.

What does the Wilcoxon (Mann-Whitney) test assess?

The registry identifies the sponsor’s analysis as a Wilcoxon (Mann-Whitney) test. In general, this is a rank-based method for comparing observations between two independent groups. It uses the relative ordering of observations rather than relying directly on a normal-theory comparison of group means. Its interpretation depends on the data and assumptions. It is often described as a test of distributional differences; it does not automatically test only whether the two medians differ. A median-only interpretation is especially limited if the group distributions differ in shape or spread.

The reported p-value is 0.56. In general, the p-value is calculated under a null hypothesis and describes how unusual the test result, or a more extreme result, would be if that null model were correct. It is not an effect-size measure and does not tell readers whether any difference is large enough to matter. A p-value also does not establish that two interventions are equivalent. The registry does not state the exact null hypothesis, test implementation, handling of ties, or whether the test was one-sided or two-sided.

What does a confidence interval add?

In general, a confidence interval gives a range of estimates compatible with the data and the method used to construct it. It can communicate both the direction and precision of an estimated contrast. A narrow interval indicates greater precision under the model; a wide interval indicates more uncertainty. A confidence interval does not eliminate uncertainty or guarantee that the true value lies in a particular interval. No confidence interval for the primary comparison is reported in the registry record, so the precision of a comparative effect cannot be assessed from the posted analysis alone.

How should the randomized design be understood?

Randomization is intended, in general, to make group assignment independent of measured and unmeasured prognostic characteristics, on average across repeated assignments. The record identifies the study as randomized and parallel-group. It does not report the sequence-generation method, allocation concealment, or whether any procedures were used to ensure that assignments could not be anticipated. No masking was reported. The record does not specify who was unmasked or whether outcome assessment was blinded, so those details cannot be inferred.

A parallel-group design compares participants assigned to one intervention with participants assigned to the other. The primary outcome summaries are reported separately by group. The registry does not state whether the primary analysis followed intention-to-treat principles, was restricted to participants with complete outcome data, or used another analysis population. It notes incomplete blocks in each group but does not say whether those cases were excluded, retained, or treated in another way.

What cannot be inferred from planning assumptions?

General sample-size illustrations can show how a hypothetical study might be planned under stated assumptions. The registry’s planning description refers to a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects expressed as fractions of the observed effect. Such illustrations are planning scenarios, not evidence about the power achieved by this completed trial. The record does not report the trial’s own sample-size justification or a prespecified target effect. Sample sizes calculated for planning are not observed power and cannot establish that the trial was adequately powered.

Over-dispersion is a general concern when variation in the data is greater than a model assumes. If a method assumes less variability than is present, uncertainty may be understated and statistical evidence may appear stronger than warranted. The registry does not describe a model for this outcome or report a variance estimate, so there is no basis for determining whether over-dispersion was relevant to the sponsor’s analysis. A rank-based test avoids some distributional assumptions of a conventional comparison of means, but it does not remove the need to examine the data, analysis choices, and study conduct.

The record lists four outcome measures, three secondary outcomes, and three analyses. It does not report a prespecified hierarchy, multiplicity adjustment, missing-data method, interim analysis plan, or the full statistical analysis plan. Those details matter when interpreting a p-value, especially when several outcomes or analyses may have been examined. The registry information permits a description of the named test and its result, but not a complete audit of the statistical workflow.

10. Analyses Reported by the Sponsor

The registry reports the sponsor’s primary comparison using a Wilcoxon (Mann-Whitney) test, with p = 0.56. It does not report a comparative effect estimate or confidence interval alongside that result. The posted arm summaries are medians with full ranges: 40.0 minutes, ranging from 15.0 to 60.0, for levobupivacaïne; and 35.0 minutes, ranging from 10.0 to 60.0, for ropivacaïne.

No recalculated comparative estimate or confidence interval is reported in the registry record, so there is no recalculation to compare directly with the sponsor’s test result. The descriptive group summaries should not be mistaken for an independent recalculation of the Wilcoxon analysis. In general, a recalculation based on summary statistics can differ from the sponsor’s analysis because it may use a different estimand or assumptions and may not use the participant-level data. The registry does not provide the information needed to reproduce the test from individual observations.

The sponsor’s posted analysis is therefore the only reported inferential comparison for the primary endpoint. Its p-value should be interpreted with the limitations of the record, including the absence of a confidence interval, analysis-population details, and a statistical analysis plan. The registry does not report a discrepancy between the sponsor’s analysis and a recalculation.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three secondary outcomes in addition to the primary endpoint and reports four outcome measures and three analyses. When a study assesses several outcomes or conducts several analyses, the chance of finding at least one apparently unusual result can increase if each is interpreted independently. In general, multiplicity methods can control or otherwise address that issue, but the suitable approach depends on the study questions and analysis plan.

The registry record does not report whether the secondary outcomes were prespecified in a hierarchy, whether the primary endpoint was protected from additional testing, or whether any adjustment for multiple comparisons was used. It also does not identify which analyses correspond to which outcomes. The posted primary p-value can be described as reported, but its relationship to any broader family of tests is not clear from the registry record. No adjustment should be assumed.

Missing-data handling is also not reported. The record gives group summaries and participant counts for the primary outcome but does not state whether all randomized participants contributed to that outcome, whether any measurements were unavailable, or how unavailable measurements were handled. It notes two incomplete blocks in each group before surgery, but does not say whether these cases were included in the primary analysis or how their outcomes were defined. The counts alone do not resolve these questions.

The analysis population is not described as intention-to-treat, per-protocol, or another specified set. The registry record also does not report a statistical analysis plan, interim-analysis procedures, or rules for stopping analyses. Because the trial status is terminated and the reason is not reported, it is not possible to determine whether termination affected outcome availability or the analysis. These omissions do not establish that the analysis was inappropriate; they limit what can be concluded about prespecification, missingness, and multiplicity.

12. 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.

The registry reports zero serious adverse events in the levobupivacaïne group, among 16 participants at risk, and zero in the ropivacaïne group, among 19 participants at risk. It also reports zero other adverse events in the respective groups. No serious adverse event terms are listed. These are the recorded event counts for the categories included in the registry entry.

Zero recorded events does not establish that an intervention has no risk. The counts apply to the participants and event reporting captured in this trial, and the registry does not provide further detail about event definitions, surveillance, duration of safety follow-up, or completeness of reporting. The death counts are not reported in the registry record. The trial’s terminated status and the reason for termination are also not explained, so the safety figures should be read narrowly as the posted counts rather than as a comprehensive assessment of safety.

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

The posted results describe the onset of action observed in the two randomized groups and the sponsor’s rank-based comparison. The median was 40.0 minutes for levobupivacaïne and 35.0 minutes for ropivacaïne; their reported full ranges were 15.0 to 60.0 minutes and 10.0 to 60.0 minutes. The Wilcoxon (Mann-Whitney) analysis had p = 0.56. Taken together, these data do not show a statistically clear difference in the reported analysis, but they do not demonstrate equivalence.

A non-significant result is not evidence that the interventions have identical effects. The p-value does not state the probability that there is no difference, and the group medians do not express the precision of the comparison. The absence of a reported confidence interval leaves uncertainty about the range of comparative effects compatible with the analysis. The registry also does not report an equivalence or non-inferiority margin, so those conclusions cannot be drawn from this result.

The record identifies the trial as randomized and parallel-group, but does not describe allocation concealment, the analysis population, missing-data handling, or the full statistical plan. It notes incomplete blocks in each group without explaining how these cases were treated. Those uncertainties affect interpretation of the reported summaries. The terminated status is recorded, but no reason is given.

The result is therefore best understood as a limited account of one reported endpoint in this trial, not as a definitive determination of whether one local anesthetic has a faster onset. It does not establish a broader effect on clinical outcomes, and the listed secondary outcomes cannot be interpreted from the primary result alone. The registry’s adverse-event counts are also limited to the categories and follow-up information recorded there.

14. Why This Trial Matters Statistically

This trial illustrates why a reported p-value should be read alongside the endpoint summary, the study design, and the information available about analysis conduct. The primary outcome is a time measurement presented as a median and full range, while the reported inferential method is a rank-based test. Each contributes different information: the summaries describe the observed groups, and the test addresses a comparison under its statistical assumptions. Neither alone gives a complete account of the size and precision of a treatment contrast.

The record also shows how sparse reporting can constrain statistical interpretation even when the main group summaries and a p-value are available. There is no comparative confidence interval, no detailed account of the analysis population, and no explanation of the incomplete blocks’ treatment in the analysis. The trial is marked terminated, but the reason is not reported. These details are relevant to understanding how much confidence to place in the result and what questions remain unresolved.

For clinical researchers and biostatisticians, the case emphasizes the value of prespecifying an estimand, defining how onset is measured, clarifying the analysis population, and describing missing-data and multiplicity procedures. It also demonstrates why a planning illustration based on an observed effect should not be confused with the trial’s original design justification or with observed power. Such distinctions help keep descriptive results, hypothesis tests, and planning calculations conceptually separate.

The posted data support a restrained interpretation: the registry reports the group onset summaries and a Wilcoxon p-value, but does not provide enough detail to reconstruct the entire analysis or assess its precision fully. Recognizing that boundary is an important part of statistical reporting, rather than a reason to overstate what the result means.

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 limitations specific to this registry record affect interpretation. The trial is marked terminated, but the reason for termination is not reported. The record gives enrollment and group counts, but does not provide participant characteristics, eligibility criteria, or enough information to judge how representative the study population was of people undergoing major foot surgery.

The primary outcome is described as onset of action in minutes, with a median, full range, and timeframe of 72 hours. The operational definition of onset and the relationship between the stated timeframe and the measurement are not reported. The record notes incomplete blocks in each group before surgery but does not state how those cases were handled in the primary analysis. It also does not clarify whether all randomized participants were included or whether outcome data were missing.

The registry names randomization and a parallel design but does not describe sequence generation, allocation concealment, or who was unmasked. Arm descriptions are empty. Details of the ultrasound-guided procedure and outcome assessment are not reported. These gaps prevent a fuller assessment of potential sources of bias and variation.

The sponsor’s analysis is reported as a Wilcoxon (Mann-Whitney) test with p = 0.56, but the registry does not provide a confidence interval, an effect estimate, participant-level data, or a complete analysis plan. It does not report whether multiplicity was addressed or whether there were interim analyses. The record lists secondary outcomes, but their numerical results are not included in the registry record. These limitations leave the primary comparison interpretable at a basic descriptive level, while limiting assessment of precision, robustness, and the broader outcome pattern.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Regional Anesthesia for Major Surgery of the Foot. Levobupivacaïne Ropivacaine 0.5% Versus 0.5% in the Sciatic Block Through médiofémorale — NCT00956709.
• Registry record last updated 2016-10-05; status last verified 2016-10.
• Results first posted 2014-08-01.
• 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

NCT00956709 is a phase 4 randomized, parallel-group trial with no masking reported, comparing levobupivacaïne 0.5% with ropivacaïne 0.5% for sciatic nerve block in major foot surgery. The registry lists Nantes University Hospital as sponsor, enrollment of 35, a start of 2008-12, primary completion of 2011-11, and status of terminated.

The primary endpoint is onset of action in minutes, reported as a median and full range. The levobupivacaïne group had a median of 40.0 and range of 15.0 to 60.0; the ropivacaïne group had a median of 35.0 and range of 10.0 to 60.0. The sponsor’s Wilcoxon (Mann-Whitney) analysis reported p = 0.56. The registry also lists three secondary outcomes and reports zero serious and zero other adverse events in each group. The reason for termination, analysis population, missing-data handling, and detailed statistical plan are not reported in the registry record.