Exparel vs. Standard Bupivicaine for Abdominoplasty: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Exparel vs. Standard Bupivicaine for Abdominoplasty (NCT01853176), a randomized phase 4 study. The primary outcome is Pain Score, Visual Analogue Pain Scores.

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group phase 4 trial sponsored by Emory University. Its official title frames the comparison as a test of whether liposomal injection bupivacaine, Exparel, is superior to standard bupivacaine for abdominoplasty. The record lists an enrollment of 4 and a status of terminated. It gives a start date of 2013-05 and a primary completion date of 2014-07. A reason for termination is not reported in the registry record.

The two intervention descriptions specify infiltration into the rectus fascia and subcutaneous tissues at the time of abdominoplasty. For Exparel, the description states a maximum approved dose of 266 mg diluted in 20 mL normal saline. For standard bupivacaine, it states a maximum safe allowance of 0.25% bupivacaine, or 1.5 mg/kg, and gives an example for a 100 kg patient. These are descriptions of the study arms, not confirmation of what each participant received.

In general, random allocation is intended to make treatment groups comparable at the start of a trial, while a parallel design assigns each participant to one study arm. The record identifies single masking but does not report who was masked or how masking was maintained. It also does not report a protocol rationale for the design, recruitment details, or the actual distribution of enrolled participants across the randomized arms.

The registry records one primary outcome measure and no analyses. The safety record lists four participants at risk in the Exparel group and zero in the standard bupivacaine group. Those safety counts should not be treated as a complete account of randomization or as an outcome analysis. The record does not explain the relationship between the planned enrollment, the enrollment recorded, the safety populations, and the trial's termination.

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

Reasons for not completing this period:

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.

Population: Did not meet target accrual before study terminated.

6. Primary Endpoint

The registry lists the primary outcome as Pain Score, Visual Analogue Pain Scores, measured over 3 days.

The registered primary endpoint is pain score measured with a continuous visual analogue scale from 0 - 10, where 0 is no pain and 10 is the worst imaginable pain. Participants were to complete a log of pain levels each morning and evening for 3 days. The registry lists the timeframe as 3 days. It does not report a summary statistic, a comparison between arms, or a result for any individual assessment time.

In general, a visual analogue pain scale is a patient-reported measure: the participant records the perceived intensity of a symptom rather than having pain inferred from an examination or a laboratory measure. Repeated entries can describe how reported pain changes over time and can capture variation between morning and evening. That feature also means that a trial needs a clear analysis plan defining how repeated scores will be summarized or compared. The registry record does not report such a plan.

The endpoint is relevant to the stated question because the trial compares local anesthetic approaches in the setting of postoperative pain. However, an endpoint definition is not a result. The registry supplies no observed scores, measure of variability, estimate of the difference between arms, confidence interval, or p-value. Without those items, the degree of precision and the direction or size of any observed difference cannot be assessed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies random allocation and a parallel-group design. In general, randomization uses chance to assign participants to study groups. Its purpose is to reduce systematic differences between groups at baseline, although a small study can still have imbalances by chance. A parallel design means that the treatment groups are compared over the study rather than each participant being described as receiving both approaches in sequence. The registry does not report the randomization procedure, allocation concealment, block size, or stratification factors. Those details are not reported in the registry record and should not be inferred.

What does single masking mean in this record?

The record labels the trial single-masked. In general, masking is intended to limit the influence of knowledge about assigned treatment on behavior, assessment, or reporting. But the registry does not say whether participants, clinicians, outcome assessors, or another group were masked. It does not explain how masking was implemented or whether it continued throughout follow-up. The label alone cannot establish which sources of bias were addressed.

What is measured by the primary endpoint?

The endpoint is a continuous visual analogue pain score with a scale from 0 - 10. The registry defines the endpoints of the scale as no pain and the worst imaginable pain, respectively. Participants were to record pain each morning and evening for 3 days. In general, a continuous outcome retains gradations in the measured experience rather than reducing it to a yes-or-no event. Repeated measurements can describe a time course, but they are correlated within a participant: scores from the same person are not generally independent observations. A statistical plan would normally specify how to account for that repeated structure or how to summarize it. The registry does not report the planned method.

What comparison was intended?

The trial title poses a superiority question: whether Exparel is superior to standard bupivacaine. In general, a superiority analysis tests whether the data support a difference in a specified direction or whether the groups differ under a defined comparison. Interpretation depends on the outcome summary, analysis population, model, and uncertainty measure. The registry record does not report the estimand, the direction and threshold for a superiority decision, or any model for the repeated scores. No numerical comparison is posted, so no statistical test can be reconstructed from the record.

Why do precision and sample size matter?

In general, an estimate describes the observed contrast, while its standard error and confidence interval describe statistical uncertainty under the chosen model. Small samples commonly yield imprecise estimates, but precision cannot be calculated without outcome data and an analysis. The enrollment listed in the record is 4. The registry does not report a sample-size justification, a target effect, or assumptions used to plan enrollment. It also does not report interim analyses or a stopping rule. The termination status does not by itself reveal why enrollment ended or whether an interim analysis occurred.

What can be said about over-dispersion?

Over-dispersion is a general concern for some outcome models when observed variability exceeds what the model expects. It can make standard errors too small if the extra variability is ignored. The registered primary endpoint is a continuous pain score, but the record does not identify a statistical model, report outcome variability, or state whether over-dispersion was assessed. It would therefore be inappropriate to assert that over-dispersion affected this trial or to describe a correction that was not reported.

What is the status of the statistical evidence?

The registry lists one primary outcome measure and zero analyses. It does not provide the score summaries needed to assess a treatment contrast, such as arm-level means, dispersion, or a model-based estimate. No p-value or confidence interval for pain is reported. In general, a non-significant result, if one were reported, would not by itself prove that treatments are equivalent; a result must be interpreted in light of its estimate, precision, and design. Here there is no reported comparative result to classify as statistically significant or not significant.

Any planning calculation based on an observed effect would require an observed effect estimate, which is absent from the registry record. No sample-size illustration or observed-power conclusion can be derived from the posted information. In general, power calculations are planning tools tied to specified assumptions, not a substitute for reporting what happened in the trial. For this record, the appropriate statistical reading is limited to the design labels, endpoint description, enrollment, and missing comparative analysis.

10. Multiplicity, Missing Data and Analysis Populations

The primary pain measure involves repeated entries: each morning and evening for 3 days. Repeated observations create several possible ways to define a primary comparison, such as comparing a single prespecified summary or modeling the trajectory over time. In general, when multiple time points or multiple outcomes are examined, the analysis plan should make clear which comparisons are primary and how the risk of false-positive findings is handled. The registry record does not report a multiplicity adjustment or a prespecified approach for combining or comparing the repeated pain scores.

The registry records one primary outcome measure, but no outcome analysis is posted. It does not report a hierarchy of secondary outcomes or explain how other analyses, if any, were to be handled. The registry lists zero analyses; it does not establish whether analyses were conducted but not entered, or whether no analysis was completed.

Missing-data handling is not reported in the registry record. The record does not say whether pain logs were complete, how missing morning or evening entries would be handled, or whether participants with incomplete logs would be included in an analysis. It also does not report an imputation method or a sensitivity analysis. In general, missing repeated measurements can affect both the number of observations available and the interpretation of an estimate, especially if missingness is related to pain or treatment assignment.

The analysis population is not reported in the registry record. There is no statement of whether the primary analysis was intended to follow randomized assignment, include participants who received treatment, or use another population definition. The registry does not report exclusions, protocol deviations, or a participant flow description. These gaps prevent assessment of how the enrolled participants contributed to any intended comparison.

11. 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 5% reporting threshold.

The registry lists four participants at risk for serious adverse events in the Exparel group and zero serious adverse events. It also lists four participants at risk for other adverse events and zero other adverse events in that group. For standard bupivacaine, the record lists zero participants at risk for both categories, with zero affected. The comparator's zero at-risk count means these entries do not provide a meaningful participant-based contrast between treatment groups.

These figures are registry safety entries, not a complete safety analysis. They do not include event descriptions or exposure details in the record, and the record does not report whether all participants were monitored for the same duration. The listed deaths values are null; deaths are not reported in the registry record. A null entry should not be rewritten as a confirmed zero.

In general, an event count is most interpretable alongside the number of people at risk, the observation period, and a clear event definition. Even when no event is recorded in a small group, that observation does not establish that the event is impossible or that the risk is absent. Here, the zero comparator at-risk count and the absence of a reported safety comparison sharply limit what can be concluded about relative safety.

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

The registry record identifies a randomized comparison of liposomal injection bupivacaine (Exparel) and standard bupivacaine for abdominoplasty. It describes the pain measure and collection schedule, reports an enrollment of 4, and marks the trial as terminated. These registry entries help define what the study set out to examine and what information is available for interpreting its record.

What the record does not establish is whether Exparel produced lower, higher, or similar pain scores compared with standard bupivacaine. No primary outcome results or analysis are reported. The endpoint description cannot serve as evidence of an effect, and the trial title's superiority wording is a research question rather than a finding. Without a comparative estimate and its uncertainty, the magnitude and precision of any difference are unknown from the registry.

The record also does not establish why the trial was terminated, whether the planned enrollment was reached, or whether complete pain logs were collected. It does not describe the analysis population, missing-data approach, or planned statistical model. Those absences matter because they prevent readers from determining how outcomes would have been summarized and how incomplete observations or repeated scores would have been handled.

The safety entries should be interpreted separately from efficacy. Four participants are listed at risk in the Exparel group, while zero are listed at risk in the standard bupivacaine group. The entries therefore do not support a direct comparison of adverse-event frequencies. The record does not report deaths.

In general, trial results need to be interpreted using the estimate, its uncertainty, the endpoint definition, and the population analyzed. A small enrollment can limit precision, but no precision measure is available. The posted information supports a description of trial intent and reporting status, not a conclusion that either treatment is superior, equivalent, or safer.

13. Why This Trial Matters Statistically

This trial is statistically notable because the registry preserves a clear comparative question but does not report the primary outcome analysis needed to answer it. The study was randomized and parallel, and the endpoint was repeated patient-reported pain scoring over 3 days. These features make the missing analysis especially important: the results would need to explain how multiple scores from the same participant were handled and what summary represented the comparison.

The enrollment recorded is 4, and the status is terminated. These details put the evidence in context, but they do not explain the reason for termination or reveal whether outcome data were collected. The lack of an analysis means there is no estimate whose size or precision can be assessed. Readers cannot determine whether the outcome was favorable, unfavorable, or inconclusive based on the registry record.

In general, publication and registry reporting are most useful when they connect the planned endpoint to an analyzed population, a clearly defined effect estimate, and an uncertainty interval. This record instead illustrates the distinction between a registered outcome and reported results. The endpoint's collection schedule is described, but a method for reducing or modeling the repeated measurements is not reported.

The safety entries add another statistical limitation: the Exparel group has four participants at risk, while the comparator group has zero at risk. Without participants recorded at risk in both arms, event counts cannot offer a balanced comparison. The record also does not report deaths.

The statistical importance of this trial record is therefore not a treatment conclusion. It is a reminder that randomization and an endpoint definition alone do not provide comparative evidence. Results, analysis details, and an account of missing observations are necessary to assess what the trial's data show and how precisely they support that interpretation.

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 main limitation of the registry record is the absence of primary outcome results. It gives no pain scores, arm-level summaries, treatment-effect estimate, measure of dispersion, confidence interval, or p-value. The comparative question cannot be evaluated quantitatively from these entries.

The recorded enrollment is 4, and the trial is marked terminated. A reason for termination is not reported in the registry record. The record does not clarify whether enrollment was complete as planned, whether all enrolled participants contributed outcome data, or whether data collection stopped before the stated primary completion date. It also does not report the number of participants included in a primary analysis.

Although the registry identifies randomization, single masking, and a parallel model, it does not describe the randomization method, who was masked, or how masking was implemented. The arm descriptions state planned infiltration approaches and doses, but the record does not confirm actual treatment received. The statistical plan, sample-size justification, interim analyses, and stopping rules are not reported.

The repeated pain logs create unanswered analysis questions. The record does not specify a primary summary across morning and evening entries, a model for within-participant correlation, a multiplicity approach, or a missing-data method. It also does not identify an analysis population. These omissions limit evaluation of bias and precision even apart from the lack of posted results.

Safety information is limited by the zero participants at risk listed for standard bupivacaine. The registry does not provide a comparative adverse-event analysis, and deaths are not reported in the registry record. Taken together, the record supports description of the registered design and endpoints, but not an assessment of comparative effectiveness or safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Exparel vs. Standard Bupivicaine for Abdominoplasty — NCT01853176.
• Registry record last updated 2014-11-03; status last verified 2014-10.
• Results first posted 2014-11-03.
• 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

NCT01853176 is a phase 4 randomized, single-masked, parallel trial sponsored by Emory University. It compares liposomal injection bupivacaine (Exparel) with standard bupivacaine for abdominoplasty. The registry records enrollment of 4, a start date of 2013-05, a primary completion date of 2014-07, and a status of terminated.

The primary measure is a visual analogue pain score from 0 - 10, logged each morning and evening for 3 days. The registry lists one primary outcome measure and zero analyses. No comparative pain results, analysis population, or statistical analysis plan are reported in the registry record.

For safety, four participants are listed at risk in the Exparel group and zero in the standard bupivacaine group. No adverse events are listed in either group, but the comparator has no participants at risk in the safety entries. Deaths are not reported in the registry record. The reason for termination is not reported.