This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Study to Find Optimal Dose of Local Spinal Anesthetic (Mepivacaine) Combined With Narcotic (Fentanyl) For Knee Surgery (NCT01701102), a randomized na study. The primary outcome is Time From Spinal Administration to Block Regression to the S1 Dermatome in Post-Anesthesia Care Unit (PACU).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01701102 |
| Phase | NA |
| Condition | Arthroscopic Knee Surgery |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 56 |
| Arms in the primary outcome | 4 |
| Lead sponsor | Hospital for Special Surgery, New York |
| Results posted | Yes |
2. Clinical Question
Population
Participants undergoing arthroscopic knee surgery. The registry reports enrollment of 56 and describes the study period for each participant as the time from surgery until same-day hospital discharge. It does not provide further participant characteristics in the record.
Intervention
The registry lists spinal mepivacaine at 24 mg, 27 mg, or 30 mg, each combined with fentanyl 10 µg. These are the lower-dose combinations being considered in relation to recovery from spinal anesthesia.
Comparator
The comparator arm is mepivacaine 37.5 mg without fentanyl. The registry also lists a general intervention entry for mepivacaine, but the arm description identifies the comparator dose as 37.5 mg.
Primary question
How does the time from spinal administration until the block regresses to the S1 dermatome in the post-anesthesia care unit differ descriptively across the four regimens? The stated study purpose was to identify the lowest mepivacaine dose combined with fentanyl for which spinal anesthesia would be adequate for ambulatory knee arthroscopy. The posted primary outcome measures block regression time; the registry record does not report an adequacy result or a formal comparison establishing a lowest adequate dose.
3. Trial Design
The registry describes a randomized, double-masked, parallel-group study and lists the status as completed. The study concerns spinal anesthesia for arthroscopic knee surgery. Its four arm descriptions are mepivacaine 37.5 mg, mepivacaine 30 mg plus fentanyl 10 µg, mepivacaine 27 mg plus fentanyl 10 µg, and mepivacaine 24 mg plus fentanyl 10 µg. Enrollment is reported as 56.
Randomization means that assignment to the study regimens was intended to be determined by chance, which can reduce systematic differences between groups. Double masking indicates that the registry classifies the study as masked at two levels, but it does not identify which people were masked or describe how masking was maintained. The allocation sequence, concealment procedures, and details of the masking are not reported in the registry record.
The recorded start is 2011-12 and the primary completion is 2012-07. The primary outcome was assessed during recovery in the post-anesthesia care unit. The registry describes follow-up as covering recovery after surgery and the period through same-day discharge; it gives an expected average PACU recovery duration of 2-4 hours. These details define the recorded observation window, not the actual duration for every participant.
The registry identifies the sponsor as Hospital for Special Surgery, New York, and lists the phase as NA. It does not report the planned allocation ratio, eligibility criteria beyond the condition and procedure description, or a target enrollment justification. The posted arm counts are not equal, but the record does not explain the reasons for the group sizes.
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
| Stage | Mepivacaine 37.5 mg | Mepivacaine 30 mg Plus Fentanyl 10 µg | Mepivacaine 27 mg Plus Fentanyl 10 µg | Mepivacaine 24 mg Plus Fentanyl 10 µg |
|---|---|---|---|---|
| STARTED | 22 | 6 | 10 | 18 |
| COMPLETED | 22 | 6 | 10 | 18 |
| NOT COMPLETED | 0 | 0 | 0 | 0 |
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.
| Characteristic | Unit | Mepivacaine 37.5 mg | Mepivacaine 30 mg Plus Fentanyl 10 µg | Mepivacaine 27 mg Plus Fentanyl 10 µg | Mepivacaine 24 mg Plus Fentanyl 10 µg | Total |
|---|---|---|---|---|---|---|
| Participants analysed | 22 | 6 | 10 | 18 | 56 | |
| Age, Continuous | years | 41 (19 to 55) | 50 (42 to 57) | 46 (27 to 60) | 45 (19 to 60) | 44 (19 to 60) |
| Sex: Female, Male: Female | Participants | 12 | 3 | 2 | 5 | 22 |
| Sex: Female, Male: Male | Participants | 10 | 3 | 8 | 13 | 34 |
| Body Mass Index | kg/(m^2) | 26.3 (SD 3.8) | 26.0 (SD 4.3) | 28.5 (SD 5.6) | 28.7 (SD 4.8) | 27.4 (SD 4.6) |
6. Primary Endpoint
The registry lists the primary outcome as Time From Spinal Administration to Block Regression to the S1 Dermatome in Post-Anesthesia Care Unit (PACU), measured over Participants will be followed for the duration of their recovery after surgery in the post-anesthesia care unit (PACU), an expected average of 2-4 hours..
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | minutes |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is time from spinal administration until the block regresses to the S1 dermatome in the post-anesthesia care unit, measured in minutes. The reported summary is the median with an interquartile range. The median describes the middle of the observed times after they are ordered; the interquartile range describes the middle half of those observations. It gives information about spread without assuming that times follow a particular symmetric distribution.
Block regression is relevant to the study’s focus on recovery from spinal anesthesia. The registry’s background describes prolonged motor block and delayed ability to walk as limitations in ambulatory surgery, while the primary endpoint specifically records sensory block regression to a dermatome. It should not be treated as a direct measure of walking, discharge readiness, anesthetic adequacy, or overall recovery. Those outcomes are not posted as primary results in the registry record.
The endpoint’s timeframe is recovery in PACU, with follow-up described as ending at same-day hospital discharge. The reported summaries are medians and interquartile-range bounds for each arm. The registry record does not post confidence intervals, participant-level times, or an inferential comparison for this outcome.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary results are descriptive. The median time to block regression was 203.0 minutes for mepivacaine 37.5 mg, with an interquartile range of 165.0 to 231.0. For mepivacaine 30 mg plus fentanyl 10 µg, the median was 195.0 minutes and the interquartile range was 175.0 to 210.0. For mepivacaine 27 mg plus fentanyl 10 µg, the median was 156.0 minutes and the interquartile range was 135.0 to 180.0. For mepivacaine 24 mg plus fentanyl 10 µg, the median was 159.0 minutes and the interquartile range was 135.0 to 194.0.
These summaries describe the observed groups; they do not establish that any regimen caused a difference in recovery time. The interquartile ranges overlap, and medians alone do not show the full distributions or the uncertainty around a comparison. The registry record reports no p-value, confidence interval, adjusted estimate, or formal analysis for the primary outcome. It therefore does not establish whether any observed difference between the group summaries is compatible with chance variation or represents a statistically distinguishable effect.
The study purpose concerned the lowest dose of mepivacaine, when combined with fentanyl, that would provide adequate spinal anesthesia. The posted primary outcome is time to regression to the S1 dermatome, not a direct report of whether anesthesia was adequate. No adequacy outcome result or decision rule for selecting a lowest adequate dose is posted in the registry record. The descriptive recovery summaries alone cannot answer that broader question.
Each arm’s reported count is different: 22 for mepivacaine 37.5 mg, 6 for mepivacaine 30 mg plus fentanyl, 10 for mepivacaine 27 mg plus fentanyl, and 18 for mepivacaine 24 mg plus fentanyl. Unequal group sizes can affect the precision of estimates, particularly for a small group, but the registry does not report confidence intervals for these medians. The record also does not explain the group-size pattern or state whether all randomized participants contributed to the endpoint summaries.
The posted results should consequently be read as arm-level summaries of recovery time, not as a confirmatory ranking of treatments. They provide a description of the observed medians and central spread in this trial, while leaving the uncertainty of between-arm effects and the adequacy question unresolved.
9. Statistical Methods Explained
The primary endpoint is a time measurement summarized with medians and interquartile ranges. This choice describes the center and spread of the observed recovery times without requiring the reader to interpret a mean as representative of every participant. Recovery times may vary, and a median is less affected by unusually long or short observations than an arithmetic mean. That is a general statistical property, not a claim about the shape of the distributions in this trial.
What does the median tell the reader?
When observations are ordered from shortest to longest, the median marks the middle of that ordered set. A group median is a summary of the group, not a time that every participant experienced. In this record, the median is reported separately for each regimen. It does not show how many participants had times above or below a clinically relevant threshold, because no such threshold result is posted.
How should the interquartile range be read?
The interquartile range describes the central half of the observations, with its lower and upper bounds marking the first and third quartiles. For example, the record reports 165.0 to 231.0 minutes for the mepivacaine 37.5 mg arm. These bounds are not confidence limits for the median. They describe variation among participant outcomes, whereas a confidence interval would describe uncertainty in an estimated population quantity. Confidence intervals are not reported for the primary endpoint.
Why are descriptive summaries not a treatment comparison?
A comparison between groups requires an estimate of the contrast and an account of its uncertainty. Looking across separate medians does not provide that uncertainty. General statistical practice would use an analysis suited to the outcome and design, with an estimate and interval or other inferential result to express how precisely the group contrast is known. The registry record does not report such a primary-outcome analysis, a test statistic, a p-value, or an adjusted comparison. No new contrast should be inferred from the posted arm summaries alone.
What does randomization contribute?
In general, random assignment is intended to balance known and unknown prognostic factors across treatment groups on average. It does not guarantee that groups will be identical, particularly when group sizes are small. The record calls the study randomized but does not describe the randomization method, sequence generation, allocation concealment, stratification, or implementation. The reader therefore cannot assess those procedures from the registry entry.
What does masking contribute?
In general, masking can limit the influence of expectations on participant experience, clinical decisions, and outcome assessment. The record labels the study double-masked, but does not state which parties were masked, whether the regimens were distinguishable, or whether masking was assessed. The label alone does not provide those operational details.
What can be said about planning calculations?
The registry record describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustrated effect is a stated fraction of the observed effect. Such calculations are prospective planning aids: they estimate the group size a future study might require under their assumptions. They are not observed power and do not demonstrate that this trial was adequately powered. The record does not report a sample-size justification for the trial’s original design, and no actual planning estimates are included in the trial details.
More generally, a planning calculation based on an observed effect can be unstable because the observed estimate itself is uncertain. The record’s stated assumptions also describe two-arm planning, while the trial has four posted arms. Without the actual planned contrast and analysis plan, the illustrations cannot be interpreted as evidence about the original design’s adequacy. The registry record does not report whether the original design included a sample-size calculation, interim analysis, stopping rule, or multiplicity adjustment.
10. Multiplicity, Missing Data and Analysis Populations
The registry reports one primary outcome measure and no posted secondary outcomes. It lists zero analyses. This does not establish that the study conducted no analyses; it means analysis results are not posted in the registry record. The record does not describe a statistical analysis plan, identify the prespecified primary contrast, or say whether comparisons among the four arms were planned as a family of tests.
Multiplicity arises when several hypotheses or outcomes are examined. In general, conducting many tests can increase the chance of at least one apparently notable result under a setting where no true effects exist. Methods for addressing this depend on the planned questions and analysis. Since the registry record does not report the analysis plan or formal comparisons, it is not possible to determine whether multiplicity was considered or controlled.
Missing-data handling is also not reported in the registry record. The record provides an enrollment figure and arm-level counts for the primary outcome, but does not explain whether those counts include everyone assigned to each regimen, whether any observations were missing, or how missing observations were handled. It does not report an intention-to-treat, per-protocol, or other analysis population. The posted group summaries should therefore be interpreted as reported, without assuming which participants were included or why the counts differ from one another.
The registry record does not report protocol deviations, exclusions, censoring, or sensitivity analyses for the primary endpoint. These omissions limit assessment of how complete and robust the posted summaries are; they do not by themselves show that data were missing or that the analysis was biased.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Mepivacaine 37.5 mg | 0 | 22 | 0.0% |
| Mepivacaine 30 mg Plus Fentanyl 10 µg | 0 | 6 | 0.0% |
| Mepivacaine 27 mg Plus Fentanyl 10 µg | 0 | 10 | 0.0% |
| Mepivacaine 24 mg Plus Fentanyl 10 µg | 0 | 18 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Mepivacaine 37.5 mg | 0 of 22 |
| Mepivacaine 30 mg Plus Fentanyl 10 µg | 0 of 6 |
| Mepivacaine 27 mg Plus Fentanyl 10 µg | 0 of 10 |
| Mepivacaine 24 mg Plus Fentanyl 10 µg | 0 of 18 |
For serious adverse events, the registry reports zero affected participants in each arm: 0 among 22 at risk for mepivacaine 37.5 mg, 0 among 6 at risk for mepivacaine 30 mg plus fentanyl 10 µg, 0 among 10 at risk for mepivacaine 27 mg plus fentanyl 10 µg, and 0 among 18 at risk for mepivacaine 24 mg plus fentanyl 10 µg. It also reports zero participants with other adverse events in each of those arm-level risk groups.
These are reported counts for the registry’s adverse-event fields. A count of zero means no affected participants are recorded for that category in the posted results; it does not establish that the underlying risk is absent. The groups are small, and the registry entry does not provide event descriptions, event-collection procedures, follow-up details specific to safety, or confidence intervals. It reports no serious adverse-event terms. Death counts are not reported in the registry record, so they should not be interpreted as zero.
Safety counts should be read separately from the primary recovery-time outcome. They do not establish a comparative safety profile between regimens, and the registry record does not post a statistical safety comparison.
12. What the Result Does, and Does Not, Mean
The registry record documents a randomized, double-masked, parallel-group study of spinal mepivacaine regimens for arthroscopic knee surgery. It posts medians and interquartile ranges for time from spinal administration to regression of the block to the S1 dermatome. Those summaries describe the recovery times recorded in each arm and allow readers to see the central outcome and its spread.
The results do not, by themselves, show that one regimen caused faster or slower recovery. No formal between-arm estimate, confidence interval, or p-value is reported. The summaries also do not establish the lowest dose that provides adequate anesthesia, because the posted primary endpoint concerns block regression rather than a direct measure of anesthetic adequacy. The study’s stated purpose and the outcome actually posted are related but not interchangeable.
Nor do these results establish effects on walking, readiness for discharge, patient experience, or other recovery outcomes. The registry describes delayed walking as part of the background rationale, but does not post those outcomes among the results in this record. The reported endpoint is measured in PACU during a same-day surgical recovery period.
The safety fields show zero recorded affected participants for serious and other adverse-event categories in each arm, with death counts not reported in the registry record. These entries are not proof that no harm occurred, and they do not support a definitive comparison of safety.
Overall, the posted results offer descriptive information about block-regression time in the four reported groups. They leave inferential uncertainty, adequacy of anesthesia, and the broader clinical consequences unresolved. Any interpretation should remain within those limits rather than turning the medians into a treatment recommendation or a definitive efficacy conclusion.
13. Why This Trial Matters Statistically
This trial illustrates the difference between a study’s clinical aim and the outcome that is posted as its primary endpoint. The stated aim is to identify a lowest mepivacaine dose, when paired with fentanyl, that gives adequate spinal anesthesia for ambulatory knee arthroscopy. The reported endpoint is time to regression of the block to the S1 dermatome. That endpoint can describe one aspect of recovery, but it does not directly establish whether anesthesia was adequate or identify a dose-selection threshold.
It also illustrates why results need both a summary and an account of uncertainty. Medians and interquartile ranges are useful descriptive statistics for recovery times, but they do not quantify the uncertainty in a comparison between regimens. Without an estimated contrast and confidence interval or other inferential analysis, readers cannot determine how precisely the groups differ or whether the apparent variation is distinguishable from chance.
The unequal arm counts are another reason to avoid treating descriptive summaries as a complete comparison. In general, the precision of a group estimate depends in part on how many observations contribute to it. The record gives arm-level counts but does not explain the allocation pattern, missing outcomes, or analysis population. That leaves important context for interpreting precision unavailable.
Finally, safety reporting demonstrates the distinction between an absence of recorded events and evidence that risk is absent. The posted adverse-event fields contain zero affected participants, but the record does not provide enough detail to infer a definitive safety profile. Together, these features make the study a useful example of how registry results can document outcome summaries while leaving key questions about analysis, uncertainty, and clinical interpretation open.
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 registry record provides limited information about the conduct and analysis of the trial. It identifies the design as randomized, double-masked, and parallel-group, but does not describe the randomization process, allocation concealment, who was masked, or how masking was maintained. It does not provide detailed eligibility criteria or baseline participant characteristics beyond the knee-surgery condition.
The posted primary outcome is summarized by arm using medians and interquartile ranges. The record does not report a formal comparison, uncertainty interval, p-value, or adjusted estimate. It also does not explain the choice of primary analysis or provide participant-level data. Consequently, the precision and statistical significance of between-arm differences cannot be assessed from the registry entry.
The arm counts are unequal, and the registry does not explain why. It does not say whether the reported counts represent all randomized participants, whether outcome observations were missing, or how analysis populations were defined. The record also does not report a sample-size justification, interim analyses, stopping rules, or multiplicity procedures. These matters are not reported in the registry record and should not be inferred from the outcome summaries.
The purpose includes determining an adequate anesthetic dose, but the posted primary outcome is regression time, and no adequacy result is reported. The record also does not post results for walking, discharge readiness, or other recovery outcomes mentioned in the background rationale. Safety entries contain no affected participants in the recorded serious and other adverse-event categories, but event ascertainment details and death counts are not reported in the registry record. These limitations restrict conclusions to the descriptive results that are actually posted.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study to Find Optimal Dose of Local Spinal Anesthetic (Mepivacaine) Combined With Narcotic (Fentanyl) For Knee Surgery — NCT01701102.
- Registry record last updated 2016-04-05; status last verified 2016-03.
- Results first posted 2016-03-10.
- 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.
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18. Record Summary
The registry describes a completed, randomized, double-masked, parallel-group study of spinal anesthesia for arthroscopic knee surgery, with enrollment of 56. The four arm descriptions are mepivacaine 37.5 mg, and mepivacaine 30 mg, 27 mg, or 24 mg, each combined with fentanyl 10 µg.
The primary outcome is time from spinal administration to block regression to the S1 dermatome in PACU, reported as a median and interquartile range for each arm. The registry posts descriptive results but no formal primary-outcome comparison or inferential statistics. It does not report an adequacy result establishing the lowest sufficient dose. Serious and other adverse-event fields list zero affected participants in each arm; death counts are not reported in the registry record.