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 Adductor Canal Block Versus Periarticular Bupivicaine Injection in Total Knee Arthroplasty (NCT02777749), a randomized phase 4 study. The primary outcome is Change in VAS Pain Scores.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02777749 |
| Phase | Phase 4 |
| Condition | Osteoarthritis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 155 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Columbia University |
| Results posted | Yes |
2. Clinical Question
Population
People with osteoarthritis undergoing total knee arthroplasty were the population of interest. The registry record lists an enrollment of 155. It does not provide further eligibility details or a fuller description of the analyzed population.
Intervention
One approach was an adductor canal block: 15 cc's of 0.5% bupivacaine administered preoperatively by the regional pain anesthesia team. A third group received this block together with 50 cc's of 0.25% bupivacaine injected intraoperatively before wound closure.
Comparator
The periarticular injection group received 50 cc's of 0.25% bupivacaine intraoperatively, just before wound closure. The record describes this as the Periarticular SB group. The trial therefore included three treatment groups rather than a single pairwise comparison.
Primary question
The central question was how postoperative visual analog scale pain scores compared across the three approaches. Scores were to be recorded two times/day from Post-Operative Day 0 through Post-Operative Day 3. The registry record does not include numerical results for those scores, so it does not establish which group had higher or lower pain scores.
The study objective was to compare pain-management approaches in total knee arthroplasty. The planned primary measure was a continuous score: the VAS ranges from 0, described as No Pain, to 10, described as the Worst Pain. Other outcomes listed were change in activity level, opioid consumption, range of knee flexion, and length of hospital stay. Those additional measures broaden the clinical questions beyond pain scores, but their results are not reported in the registry record.
The study was registered as a randomized, double-masked, parallel-group trial. Randomization is intended, in general, to make group assignment less dependent on participants' characteristics, while masking is intended to limit the influence of knowledge of assignment on care or assessment. The record does not state who was masked or describe how assignment was carried out. Its design helps frame the intended comparison, but the missing outcome results prevent an assessment of the observed differences.
3. Trial Design
The registry identifies this as a Phase 4, randomized, double-masked, parallel-group study sponsored by Columbia University. It lists osteoarthritis as the condition and total knee arthroplasty as the surgical setting. Enrollment was 155, and the study status is completed. The record lists a start date of 2016-07-19 and a primary completion date of 2017-09-19.
Three groups are described. The Adductor Canal Block group received 15 cc's of 0.5% bupivacaine before surgery. The Periarticular SB group received 50 cc's of 0.25% bupivacaine during surgery, just before wound closure. The ACB + SB group received both described procedures. The intervention list names Bupivacaine as a drug; the record does not provide additional details about other co-interventions or the broader perioperative care.
A parallel-group design assigns participants to a group and compares outcomes between groups. In general, random assignment can support a causal comparison by reducing systematic differences at baseline, although the registry record does not describe the randomization procedure, allocation concealment, or baseline characteristics. The record labels the study double-masked but does not identify which people were masked, how masking was maintained, or whether it was successful.
The primary outcome was change in VAS pain scores over Day 0 through Day 3, with scores planned two times/day. Four secondary outcomes are named: change in activity level, opioid consumption, range of knee flexion, and length of hospital stay. The record lists five outcome measures overall, but gives no numerical results for them. Although the study is marked completed, completion status alone does not provide evidence about the size, direction, or precision of any treatment-group differences.
The registry record does not report detailed eligibility criteria, participant flow, treatment adherence, protocol deviations, or the precise analysis population. These omissions limit assessment of how the intended design was implemented and how broadly the results might apply.
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 | Adductor Canal Block | Periarticular SB | ACB + SB |
|---|---|---|---|
| STARTED | 53 | 51 | 51 |
| COMPLETED | 53 | 51 | 51 |
| NOT COMPLETED | 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 | Adductor Canal Block | Periarticular SB | ACB + SB | Total |
|---|---|---|---|---|---|
| Participants analysed | 53 | 51 | 51 | 155 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 14 | 9 | 13 | 36 |
| Age, Categorical: >=65 years | Participants | 39 | 42 | 38 | 119 |
| Age, Continuous | years | 69 (SD 10) | 73 (SD 10) | 71 (SD 10) | 71 (SD 10) |
| Sex: Female, Male: Female | Participants | 38 | 33 | 37 | 108 |
| Sex: Female, Male: Male | Participants | 15 | 18 | 14 | 47 |
| Race and Ethnicity Not Collected | Participants | — | — | — | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Change in VAS Pain Scores, measured over Day 0 through Day 3.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | scores on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change in VAS pain scores. The visual analog scale is described as running from 0, meaning No Pain, to 10, meaning the Worst Pain. The score is a continuous measure: it can represent degrees of pain rather than sorting participants only into broad categories. The registry specifies a mean and standard deviation as the summary form, and says scores were to be recorded two times/day from Post-Operative Day 0 through Post-Operative Day 3.
Repeated assessment across the early postoperative period can describe pain at different times, rather than relying on a single assessment. In general, a mean describes the average score in a group, while a standard deviation describes how spread out individual scores are around that average. These summaries answer different questions: the mean concerns the group’s typical score, while the standard deviation concerns variation among observations.
The record does not specify a single summary across the assessment times, such as a particular average over the period, nor does it report numerical scores, group contrasts, confidence intervals, or a statistical test for the primary endpoint. It also does not state whether the reported change would be calculated from a baseline measure or how repeated observations would be handled. As a result, the endpoint description explains what was intended to be measured, but not the observed pain pattern or its precision.
VAS pain scores are used in general because they provide a structured way to record a person's reported pain intensity. They are not a complete description of recovery or function. The separately listed outcomes—activity level, opioid consumption, knee flexion range, and hospital stay—address other aspects of postoperative care, but their results are also absent from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a completed randomized comparison of an adductor canal block, periarticular bupivacaine injection, and the combination. It does not report numerical primary-outcome results. In particular, there are no group means, standard deviations, between-group estimates, confidence intervals, or primary-outcome p-values in the record. Therefore, the available information does not show the direction or magnitude of any difference in postoperative VAS pain scores.
The study's planned repeated pain assessments could, in principle, reveal whether group patterns differed over the early postoperative period. However, the registry does not give values at individual assessment times or a single summary over the period. It also does not report an analysis that compares groups across time. The record explicitly notes that the primary outcome has several categories or time points and was not reduced to one comparison. Without results, there is no basis for judging whether any apparent difference was large, small, consistent over time, or estimated precisely.
Statistical interpretation normally considers an effect estimate together with its uncertainty. A confidence interval, in general, gives a range of values compatible with the data and the analysis assumptions; a narrow interval indicates greater precision than a wide interval. Neither an effect estimate nor its interval is reported for the primary outcome. A p-value alone, if available, would not convey the size or clinical relevance of a difference, and no primary p-value is reported in any case.
The registry lists five outcome measures and four secondary outcomes, but no numerical findings for these measures. It also lists zero analyses. The lack of analysis entries should not be interpreted as evidence that no analysis was performed outside the registry; it means only that analyses are not reported in this registry record. Likewise, study completion and enrollment do not substitute for outcome findings.
Safety information is reported separately. For serious adverse events, the record lists zero affected participants in the Adductor Canal Block group, with 53 at risk; zero in the Periarticular SB group, with 51 at risk; and zero in the ACB + SB group, with 51 at risk. It also lists zero other adverse events and zero deaths in each group. These are the reported counts, not evidence that the risk of an event is absent. The registry record does not give further details about event definitions, collection procedures, follow-up completeness, or how the safety observations were analyzed.
Overall, the record establishes the intended design, intervention descriptions, endpoint schedule, and listed safety counts. It does not permit a statistical comparison of pain outcomes among the groups. No conclusion about which approach had higher or lower pain scores, or how precisely any difference was estimated, can be drawn from the outcome information recorded.
9. Statistical Methods Explained
Statistical methods help connect a study design to the conclusions that its data can support. For this trial, the registry identifies randomization, masking, a parallel-group structure, a continuous primary outcome, and a repeated assessment schedule. It does not report the detailed statistical analysis plan or numerical primary-outcome analyses. The explanations below describe general statistical principles and distinguish them from methods documented in the registry record.
What does randomization contribute?
In general, random assignment is used to reduce systematic differences between groups that could otherwise influence an outcome. It does not guarantee that groups will be identical, especially in a particular realized sample. The record identifies the study as randomized but does not describe the sequence-generation method, allocation concealment, stratification, or checks of baseline comparability. Those details are therefore not reported in the registry record.
A parallel-group design means the groups are compared as separate arms. Here, the record describes Adductor Canal Block, Periarticular SB, and ACB + SB. A three-group design can support more than one pairwise question, but which comparisons were designated primary or how comparisons were ordered is not reported. The recorded primary outcome is not reduced to one comparison in the registry.
How should mean and standard deviation be read?
The record specifies mean and standard deviation for the continuous VAS measure. In general, the mean is the arithmetic average of recorded scores and provides a measure of group location. The standard deviation describes the dispersion of scores around that mean. A mean does not describe every participant's experience, and a standard deviation is not a measure of uncertainty in the mean. That uncertainty is typically represented by a standard error or a confidence interval, neither of which is reported for the primary endpoint.
When comparing group means, an estimated difference would describe the contrast in average scores on the VAS scale. A confidence interval around that contrast would communicate its precision and the range of values reasonably compatible with the data under the analysis assumptions. The registry record does not report the group means or any contrast, so no such comparison can be interpreted. No new estimate can be reconstructed from the information recorded.
Why do repeated measurements matter?
VAS scores were planned two times/day from Post-Operative Day 0 through Post-Operative Day 3. Repeated observations from the same participant are generally correlated: a person's scores may be more similar to one another than scores from different people. Analyses that treat all repeated observations as independent can misstate uncertainty. Common general approaches account for within-person correlation, but the registry record does not say whether such an approach was used. It also does not state whether the main comparison was based on each assessment time, a summary over time, or a model of the trajectory.
Over-dispersion is a general concern when observed variability exceeds what a statistical model assumes. It matters because an incorrect variability assumption can lead to confidence intervals and tests that are too optimistic or too conservative. The primary measure is continuous, and the record reports that standard deviation was the planned dispersion summary. It does not report a distributional assessment, model diagnostics, or any adjustment for unusual variability. No claim about over-dispersion in the trial data is possible from the registry record.
What can masking and the analysis plan tell us?
The trial is labeled double-masked. In general, masking may reduce the influence of knowledge of treatment assignment on behavior, care, measurement, or assessment. The record does not say who was masked, whether the procedures could reveal assignment, or how masking was assessed. The label alone does not establish that all potential sources of bias were prevented.
A statistical analysis plan ordinarily specifies the target comparisons, outcome definitions, treatment of repeated measurements, covariate adjustment, handling of missing observations, and analysis populations. These details are not reported in the registry record. The record lists zero analyses, so no fitted model, test, or adjustment can be attributed to the study based on the registry information alone.
How should the planning assumptions be understood?
The record describes sample-size calculations as planning illustrations based on an observed effect, not as the trial's own design. It states assumptions of a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. For non-time-to-event outcomes, such illustrations are expressed as participants per arm. No specific illustration values or observed effect estimate are included in the registry record, so the calculations cannot be evaluated from the information available.
Such planning calculations are not observed power. In general, a planning illustration asks how much information would be needed to detect a chosen effect under stated assumptions. It does not establish that the trial had that probability of detecting an effect after the data were collected. Nor does it replace an estimate and confidence interval for the observed treatment contrast. The assumptions describe a hypothetical calculation, not the trial's documented randomization balance or its completed analysis.
10. Multiplicity, Missing Data and Analysis Populations
Multiplicity arises when several outcomes, treatment contrasts, time points, or analyses are considered. In general, testing many hypotheses can increase the chance of at least one apparently notable result arising by chance. Researchers may address this through a prespecified hierarchy, an adjustment to significance thresholds, or a strategy that distinguishes confirmatory from exploratory analyses. The registry lists a primary outcome assessed repeatedly over Day 0 through Day 3, three treatment groups, and four secondary outcomes. It does not report a multiplicity strategy or identify how comparisons across groups and assessment times were prioritized.
The record notes that the primary outcome has several categories or time points and is not reduced to one comparison. It does not provide a primary contrast, a time-specific analysis plan, or an adjustment method. Consequently, the number and role of statistical tests cannot be determined from the registry record. This uncertainty is about reporting; it does not establish that multiplicity was ignored in any analysis conducted elsewhere.
Missing-data handling is also not reported. The record does not state how many participants contributed outcome observations, whether some scheduled scores were missing, why observations might be missing, or whether any method was used to handle missing values. In general, the consequences of missing data depend partly on why values are unavailable and how the analysis treats them. Without participant flow and missingness details, the completeness of the pain-score data cannot be assessed.
The analysis populations are not defined in the registry record. It does not say whether the primary analysis followed assigned groups regardless of treatment received, included only participants who completed treatment, or used another population. Those choices can affect the interpretation of a treatment comparison, so the absence of a definition limits evaluation of the estimand and analysis.
The record also does not report protocol deviations, adherence, or sensitivity analyses. These omissions do not prove that the relevant information or analyses do not exist elsewhere; they mean that these features cannot be evaluated from the registry record.
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 |
|---|---|---|---|
| Adductor Canal Block | 0 | 53 | 0.0% |
| Periarticular SB | 0 | 51 | 0.0% |
| ACB + SB | 0 | 51 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Adductor Canal Block | 0 of 53 |
| Periarticular SB | 0 of 51 |
| ACB + SB | 0 of 51 |
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 |
|---|---|
| Adductor Canal Block | 0 of 53 |
| Periarticular SB | 0 of 51 |
| ACB + SB | 0 of 51 |
The registry lists serious adverse event counts separately for each treatment group. It reports zero affected participants among 53 at risk in the Adductor Canal Block group, zero among 51 at risk in the Periarticular SB group, and zero among 51 at risk in the ACB + SB group. The record also lists zero other adverse events and zero deaths for each of the three groups.
These entries describe the events recorded during the registry's safety reporting, not a guarantee that no event could occur. A zero count does not establish that the underlying risk is zero; uncommon events may not be observed in a study, and the precision of a risk estimate depends on the amount and quality of follow-up. No confidence intervals or comparative safety analyses are reported.
The registry record does not provide the definitions used for serious and other adverse events, the duration or completeness of safety follow-up, or details on how events were collected and assessed. It also does not say whether the counts were analyzed according to assigned treatment or treatment received. The figures should therefore be read as the reported counts and group denominators, without inferring a broader safety profile or a difference between approaches.
12. What the Result Does, and Does Not, Mean
This trial record is relevant to the statistical question of comparing pain scores after total knee arthroplasty under three perioperative approaches. Its randomized, double-masked, parallel-group designation describes an intended comparative design. The primary outcome is clearly identified as change in VAS pain scores, with a stated scale and repeated assessment schedule. Those details help define what the study set out to measure.
What the record does not provide is equally important: no numerical primary-outcome results, group summaries, estimates of between-group differences, confidence intervals, or primary-outcome tests are reported. The registry record therefore cannot show whether the approaches produced different observed pain scores, the direction of any difference, or how precisely a difference was estimated. No claim about efficacy follows from the design description alone.
Even when numerical results are available, statistical and clinical interpretation are distinct. A statistical estimate describes the observed contrast and its uncertainty under an analysis; clinical interpretation asks whether the magnitude is meaningful in context. The record does not give an estimated contrast or a threshold for a clinically important difference, so neither question can be answered. The VAS scale endpoints clarify the measure's range, but do not supply the results needed to judge the size of any group difference.
The record lists activity level, opioid consumption, knee flexion range, and hospital stay as secondary outcomes, but reports no findings for them. Its safety entries show zero reported serious adverse events, other adverse events, and deaths in each group, with group-specific numbers at risk. Those counts are informative as registry entries but cannot, without further follow-up and analysis details, establish comparative safety or rule out uncommon events.
Completion status indicates that the study is marked completed; it does not mean that outcome data or a statistical analysis are included in the record. The defensible reading is that the registry documents the design and intended measures, while the results needed to judge comparative outcomes are not reported in the registry record.
13. Why This Trial Matters Statistically
This study raises a useful design question for clinical research: how should a trial compare several treatment approaches when the principal outcome is measured repeatedly during a short postoperative period? A single endpoint description may conceal important choices about whether to compare groups at each time, summarize scores across time, or examine how scores change over time. Those choices define the statistical question and should be specified in a prespecified analysis plan.
The three-group structure also makes the choice of comparisons important. A trial may be interested in each pair of approaches, or may prioritize one contrast and treat others as secondary. In general, clearly identifying those aims helps readers distinguish planned confirmatory comparisons from exploratory ones and understand how multiplicity is handled. The registry record does not report a prioritized comparison or a multiplicity strategy, and it does not give outcome analyses.
Repeated pain ratings also illustrate why data structure matters. Observations from the same participant are not generally independent, so an analysis should account for their relationship when estimating uncertainty. A report that states the model, the treatment contrast, and its confidence interval can help readers judge both the pattern and precision of the findings. Those details are not available in this registry record.
Finally, outcome reporting is necessary for a completed trial to inform statistical interpretation. Design labels, enrollment, and a planned endpoint explain what researchers intended to investigate, but they cannot substitute for estimates and their uncertainty. The trial's registry entry is useful for understanding its question and intervention groups; the absence of reported outcome analyses prevents a comparison of the groups' observed pain outcomes.
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.
A central limitation for interpreting this particular trial is that the registry record does not include numerical results for its primary endpoint. It describes VAS pain scores and their scheduled assessment, but provides no group means, standard deviations, treatment contrasts, confidence intervals, or tests. The direction, magnitude, and precision of any difference therefore cannot be assessed from this record.
The endpoint is recorded across multiple assessment times, yet the record does not define a single summary over the period or specify how repeated observations were analyzed. It notes that the primary outcome was not reduced to one comparison. The approach to comparisons among the three groups and across time points is not reported, nor is any multiplicity handling.
Several other analysis details are absent. The registry does not define the analysis population, describe missing outcome data, report participant flow, or explain how protocol deviations and treatment adherence were handled. It does not provide baseline characteristics, detailed eligibility criteria, or the randomization and allocation-concealment procedures. The double-masked designation is recorded, but who was masked and how masking was maintained are not specified.
The registry lists safety counts but not event definitions, follow-up completeness, or comparative safety analyses. The listed zeros should not be treated as proof of no risk. Finally, the sample-size information is described as a planning illustration based on an observed effect, but no specific calculation values or observed effect estimate are included in the registry record. These reporting gaps limit assessment of both the outcome findings and the precision of any planned comparison.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Adductor Canal Block Versus Periarticular Bupivicaine Injection in Total Knee Arthroplasty — NCT02777749.
- Registry record last updated 2019-03-20; status last verified 2019-03.
- Results first posted 2019-03-20.
- 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 identifies a completed Phase 4, randomized, double-masked, parallel-group trial sponsored by Columbia University. It lists osteoarthritis, enrollment of 155, and three groups: Adductor Canal Block, Periarticular SB, and ACB + SB. The listed primary measure is change in VAS pain scores, planned two times/day from Post-Operative Day 0 through Post-Operative Day 3.
Four secondary outcomes are named: change in activity level, opioid consumption, range of knee flexion, and length of hospital stay. Numerical results and analyses for the primary and secondary outcomes are not reported in the registry record. Safety entries report zero serious adverse events, other adverse events, and deaths in each group. The registry therefore documents the study question and design but does not provide the outcome analyses needed to compare pain scores across groups.