Efficacy and Safety of Single, Low-dose Dexamethasone in Patients After Total Knee Arthroplasty: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy and Safety of Single, Low-dose Dexamethasone in Patients After Total Knee Arthroplasty (NCT01612702), a randomized phase 4 study. The primary outcome is Incidence of Nausea and Vomiting.

2. Clinical Question

The clinical question concerns whether adding one low dose of dexamethasone before total knee arthroplasty changes the observed incidence of nausea and vomiting during the first 72 hours after surgery, in the setting described in the study summary. It also has a safety dimension: the summary identifies wound complications as a concern, and the record includes serious adverse event figures.

The primary endpoint combines nausea and vomiting in its title. The endpoint description says a blinded clinical investigator assessed postoperative nausea, defined as the subjective unpleasant sensation associated with awareness of the urge to vomit, as well as emetic episodes and vomiting. The registry record does not describe how those components were combined into a single endpoint, how repeated episodes were handled, or how participants with incomplete assessments were treated.

The posted results are descriptive by arm. They show the reported incidence estimates and their confidence intervals, which allow readers to see the arm-specific results and their stated precision. They do not provide a posted between-arm estimate, confidence interval for a contrast, or test for the primary endpoint. Therefore, the page can describe the observed pattern, but the posted primary results alone do not establish the size or precision of a treatment contrast.

3. Trial Design

This was a phase 4, randomized, double-blind, parallel-group trial sponsored by Tae Kyun Kim. The registry record lists an enrollment of 291 and a completed status. The intervention was dexamethasone, given as 10 mg 1 hour before surgery; the control arm received no dexamethasone. The study focused on patients undergoing total knee arthroplasty for knee osteoarthritis.

The record lists a start date of 2011-04 and a primary completion date of 2011-12. It does not report additional details about the randomization sequence, allocation concealment, the identities of the people who were masked, or whether masking was maintained throughout follow-up. The labels “randomized” and “double” describe the registered design, but they do not by themselves answer those operational questions.

The study summary places the intervention in the context of an antiemetic protocol based on Ramosetron. It says the study examined postoperative nausea and vomiting, pain, and safety in terms of wound complications. The registry record lists pain level and wound complication as secondary outcomes. The primary endpoint was incidence of nausea and vomiting within 72 hours after surgery. Pain was recorded during the timeframe of 6 to 24 hours after surgery.

The posted primary results include 146 participants in the dexamethasone arm and 145 in the control arm. Pain results are also posted for those arm sizes. The registry record does not report whether these counts represent all randomized participants, all participants who received treatment, or only participants with available outcome data. It also does not describe exclusions after randomization or define an analysis population.

There are no reported analyses listed in the registry record. The record does not provide the full statistical analysis plan, the intended primary contrast, or details of any interim analyses. Those omissions limit how specifically the posted summaries can be connected to a prespecified analysis strategy.

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.

Before assignment: 14 patients were excluded before assignment. 5 were other diagnosis such as rheumatoid arthritis, secondary osteoarthritis, 4 had serious medical conditions such as renal failure, heary failure, 5 refused to participate

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.

6. Primary Endpoint

The registry lists the primary outcome as Incidence of Nausea and Vomiting, measured over within 72 hours after surgery.

The primary endpoint is the incidence of nausea and vomiting within 72 hours after surgery. It is intended to summarize how often these postoperative symptoms or events occurred during the stated follow-up period. Such an endpoint is relevant to the study question because the intervention was assessed as an addition to an antiemetic protocol, and the study summary identifies postoperative nausea and vomiting as a target outcome.

The registry description says that a clinical investigator blinded to randomization assessed postoperative nausea. It defines nausea as a subjective unpleasant sensation associated with awareness of the urge to vomit, and also refers to emetic episodes and vomiting. Blinded assessment can help limit the influence of knowledge about assigned treatment when recording an outcome. The record does not explain the assessment schedule, the precise rule for classifying a participant as having the endpoint, or how nausea and vomiting observations were combined.

The posted results express the endpoint as a percentage of participants and give a confidence interval for each arm. Those are arm-specific summaries. A direct comparison would require an estimate of the difference or another specified contrast, with its own uncertainty. Such a primary-endpoint comparison is not reported in the registry record. The interval around each arm’s estimate should therefore not be read as an interval for the difference between arms.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does randomization contribute?

Randomization assigns participants to treatment groups by chance. In general, this helps make the groups comparable at the start of a trial with respect to both measured and unmeasured characteristics, apart from differences that occur by chance. It supports interpreting a between-group contrast as a comparison of assigned strategies, provided the assignment process is implemented appropriately and the analysis preserves the benefits of randomization. The registry record identifies this study as randomized, but the sequence-generation and allocation-concealment procedures are not reported in the registry record.

What does double masking mean for interpretation?

The registry record labels the study double-blind. In general, masking can reduce the risk that expectations influence how participants report symptoms, how investigators assess outcomes, or how other trial decisions are made. Its value depends on who was masked and whether masking was maintained. The record does not identify the masked parties or describe how masking was implemented. For the primary endpoint, it does say that a clinical investigator who was blinded to randomization assessed nausea and vomiting. This is relevant to outcome assessment, but it does not fill in the other masking details.

How should the primary percentages and intervals be read?

The primary outcome is reported as a percentage of participants, with a 95% confidence interval for each arm. In general, a confidence interval conveys uncertainty around an estimate: narrower intervals indicate greater precision under the method used, while wider intervals indicate less precision. The intervals belong to the separate arm estimates. They are not a direct interval for a between-arm difference, and comparing whether separate intervals overlap is not a substitute for analyzing the contrast itself. The registry record does not report the method used to calculate these primary endpoint intervals or a direct comparison between arms.

Why does the type of outcome matter?

Nausea and vomiting are represented as an incidence or percentage rather than as a continuous measurement. In general, an analysis of a binary or count-related outcome depends on how the event is defined, what population is included in the denominator, and whether each participant can contribute only once or can contribute repeated events. Different statistical models can answer different questions about such data. The registry record describes the outcome as a percentage of participants but does not report a model, a detailed endpoint rule, or how repeated events were handled. A model should not be inferred from the displayed summaries alone.

Pain is presented as a mean with a standard deviation. In general, the mean summarizes the central level of a continuous measurement, while the standard deviation describes participant-to-participant spread around that mean. The posted secondary results also include an unadjusted mean difference and a confidence interval, with p < 0.001. This is a secondary comparison and is not adjusted for multiple outcomes or analyses in the posted results. A p-value describes how compatible the observed data are with a specified null model under the analysis assumptions; it is not the probability that a treatment effect is true, and it does not describe the size or practical importance of an effect.

What does over-dispersion mean in general?

For count outcomes, some models make assumptions about how much variability should be expected relative to the average event frequency. Over-dispersion occurs when the observed variability is greater than the model expects. If it is ignored, standard errors may be too small and confidence intervals or tests may appear more precise than warranted. This is a general statistical issue, not a claim about this trial: the registry record does not report a count model, a dispersion assessment, or whether over-dispersion was considered. The primary outcome is posted as a percentage, so the record does not support attributing any particular model or dispersion issue to its analysis.

What does the sample-size illustration show?

The sample-size section on the page is a planning illustration based on the observed secondary pain effect, not the trial’s design calculation. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. It shows planning for different fractions of the observed effect and reports participants per arm for 80% power and participants per arm for 90% power. These are hypothetical planning quantities under those assumptions. They are not the number enrolled, do not describe the trial’s prespecified sample-size justification, and are not observed power. The trial’s own sample-size assumptions and justification are not reported in the registry record.

Why is a posted analysis plan important?

A prespecified statistical analysis plan can explain the primary contrast, analysis population, model, missing-data approach, and handling of multiple outcomes before results are examined. In general, these choices help readers distinguish planned analyses from analyses selected after seeing the data. The registry record lists no reported analyses and does not provide the full analysis plan. Therefore, the posted summaries can be described, but readers cannot verify from this record whether the displayed analyses follow a prespecified strategy.

10. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a statistical analysis plan, a multiplicity strategy, or any reported analyses. The study summary and outcome listings identify a primary endpoint and secondary outcomes, but the record does not say whether the secondary analyses were prespecified, whether there were additional planned comparisons, or whether a hierarchy was used to control the interpretation of multiple tests. These omissions matter because each additional outcome or analysis can create another opportunity for a chance finding.

The posted pain comparison is unadjusted. In general, an unadjusted p-value addresses one comparison under its analysis assumptions; it does not account for a wider family of outcomes or tests. Without a stated multiplicity plan, it is not possible to determine how the trial intended to balance false-positive risk across analyses. This does not invalidate the descriptive result, but it limits how confidently an individual secondary result can be treated as confirmatory.

Missing-data handling is also not reported in the registry record. The posted arm sizes do not establish how many participants had usable measurements at each assessment, whether all randomized participants were included in each analysis, or how missing outcomes were handled. The record does not describe imputation, complete-case analysis, exclusions, or sensitivity analyses. These details can affect both the estimate and its uncertainty, particularly if outcome availability is related to treatment assignment or outcome status.

The analysis population is not reported in the registry record. It is therefore unclear whether the posted results follow an intention-to-treat approach, a per-protocol approach, or another definition. The registry record also does not report interim analyses or stopping rules. These are reporting gaps, not evidence that a particular method was or was not used. They prevent a full assessment of whether the available results follow a prespecified analysis strategy.

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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: wound complication (0.7%).

The serious adverse event listing reports one serious event among 146 participants in the dexamethasone arm and one among 145 participants in the control arm. Wound complication is the serious adverse event term shown in the record. These figures are event counts within the posted at-risk groups; they are not a complete safety comparison and should not be interpreted as establishing that risks are equivalent or different.

With sparse counts, estimates of comparative safety are inherently imprecise. In general, a small number of events gives limited information about the range of plausible differences between groups. The registry record does not post a statistical comparison or confidence interval for serious adverse events, and it does not provide a detailed account of event timing, severity beyond the serious classification, relatedness to treatment, or adjudication. The listed term should therefore be read as a description of what was recorded, not as proof of causation.

The record lists no non-serious adverse events in either arm. Death values are not reported in the registry record. These entries do not establish that no other harms occurred outside the posted categories or reporting period. The available figures are useful for transparent description, but the record does not provide enough detail to draw a comprehensive safety conclusion.

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

The posted results establish what the registry record reports: arm-specific incidence estimates for nausea and vomiting within 72 hours after surgery, pain summaries, and serious adverse event counts. The primary endpoint percentages are lower in the dexamethasone arm than in the control arm. That observed pattern is worth describing, but the primary endpoint has no posted between-arm estimate or test in the registry record. The arm-specific confidence intervals do not supply that missing comparison.

The trial’s randomized, double-blind designation is relevant to how a comparison might be interpreted, and the study summary describes the dose and clinical context. Still, design labels cannot answer every question about conduct or analysis. The registry record does not report the randomization procedures, analysis population, missing-data methods, primary contrast, or full statistical plan. Those gaps mean the posted results cannot be evaluated against a fully specified analysis strategy using this record alone.

The secondary results add information about outcomes beyond the primary endpoint, but the registry record does not report a multiplicity plan. A secondary result should therefore not be treated as definitive confirmation of the primary question. Similarly, the serious adverse event counts are descriptive and sparse; they do not establish comparative safety or treatment causation.

These results do not, by themselves, show whether the intervention should be used in clinical practice. They do not establish how results would generalize to settings, patient groups, or care protocols not described in the record. They also do not reveal whether the results were consistent across subgroups or whether longer-term outcomes differed, because such findings are not reported in the registry record. The most defensible reading is limited to the posted measurements and their stated precision, with the missing direct primary comparison and analysis details kept visible.

13. Why This Trial Matters Statistically

This trial is statistically instructive because it pairs a randomized design with primary results that are posted as separate arm estimates rather than as a direct comparative analysis. Readers can see the reported incidence in each group and the confidence interval around each estimate, but those summaries do not answer the same question as a treatment contrast. Recognizing that distinction prevents arm-level uncertainty from being mistaken for uncertainty about the difference.

The record also illustrates why endpoint definition and analysis details matter. The primary endpoint includes nausea and vomiting, with a stated assessment timeframe and a blinded investigator, but the record does not explain the event-classification rule or how repeated events were handled. Such details shape what an incidence percentage means and how it should be analyzed. A registry record can give a useful overview while still leaving important methodological questions unresolved.

Secondary outcomes add another statistical lesson. A result can be presented with an unadjusted comparison, yet its interpretation depends on whether it was planned and how it fits among the other outcomes. Since multiplicity handling is not reported, secondary findings deserve more cautious weight than a clearly prespecified primary analysis would receive.

Finally, the sample-size illustration is distinct from the trial’s actual design justification. Planning calculations based on an observed effect can help readers understand how assumed effect size and power relate in general, but they do not establish that the trial was planned that way or that it had adequate power for its primary endpoint. Keeping planning illustrations separate from trial-design evidence is essential for an accurate statistical reading.

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.

Several limitations are specific to the information available for this trial. The registry record does not report a direct analysis of the primary endpoint between the randomized groups. It provides arm-specific percentages and confidence intervals, but not a contrast with its own confidence interval or test. The method used to construct the primary confidence intervals is not reported in the registry record, so their assumptions cannot be assessed.

The endpoint description does not give a complete operational definition. It identifies nausea, emetic episodes, and vomiting, but does not explain how participants were classified, whether recurrent episodes counted once or repeatedly, or how assessments were scheduled within the 72-hour period. The record does not state whether the nausea and vomiting components were analyzed separately as well as together.

Important trial conduct and analysis details are also absent. The randomization procedure, allocation concealment, parties included in double masking, analysis population, missing-data methods, and statistical analysis plan are not reported in the registry record. The record does not explain whether all randomized participants contributed to each outcome or whether any post-randomization exclusions occurred.

The secondary analyses are reported without a stated multiplicity approach, and the registry record does not clarify whether they were prespecified. The serious adverse event information is limited to posted counts and a listed term; event-level details and a formal safety comparison are not reported. Finally, the study summary identifies an antiemetic protocol based on Ramosetron, but the record does not provide enough detail to assess how the results might apply under other care settings or protocols. These limitations concern the record’s reporting and do not establish that particular procedures were absent from the conduct of the trial.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Efficacy and Safety of Single, Low-dose Dexamethasone in Patients After Total Knee Arthroplasty — NCT01612702.
• Registry record last updated 2013-05-27; status last verified 2013-05.
• Results first posted 2013-05-21.
• 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

The registry record describes a completed, phase 4, randomized, double-blind, parallel-group study sponsored by Tae Kyun Kim. It enrolled 291 patients undergoing total knee arthroplasty for knee osteoarthritis. The intervention was dexamethasone 10 mg 1 hour before surgery; the control group received no dexamethasone. The listed study dates are 2011-04 for start and 2011-12 for primary completion.

The primary endpoint was incidence of nausea and vomiting within 72 hours after surgery. Results are posted for 146 participants in the dexamethasone arm and 145 in control, with arm-specific percentages and confidence intervals. The record lists pain level and wound complication as secondary outcomes. It also reports one serious adverse event in each arm, with wound complication as the listed serious event term.

No reported analyses are listed in the registry record. A direct primary-endpoint comparison, the analysis population, missing-data methods, multiplicity approach, and detailed statistical plan are not reported in the registry record. The available results can therefore be summarized descriptively, while the limits on comparative interpretation remain important.