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 Vitagel Revision Total Knee Arthroplasty (NCT01923805), a randomized na study. The primary outcome is Transfusion Requirements.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01923805 |
| Phase | NA |
| Condition | Failed Total Knee Arthroplasty |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 8 |
| Arms in the primary outcome | 2 |
| Lead sponsor | The Cleveland Clinic |
| Results posted | Yes |
2. Clinical Question
Population
People undergoing revision total knee arthroplasty for failed total knee arthroplasty. The registry lists an enrollment of 8, but it also states that data were not collected from participants enrolled in the study. The record does not describe participant characteristics or eligibility details beyond the condition and procedure.
Intervention
Vitagel, described as a collagen/thrombin autologous platelet hemostatic agent. Its use was intended to be evaluated during revision knee arthroplasty, with attention to transfusion requirements and other outcomes described in the study summary.
Comparator
Standard of care for surgical hemostasis. The registry identifies this as the control approach but does not give further details about the specific care used.
Primary question
Does the use of Vitagel, compared with standard surgical hemostasis, differ in transfusion requirements among patients managed with revision total knee arthroplasty? The registry names transfusion requirements as the primary outcome, but reports that participant data were not collected. A comparative effect therefore cannot be estimated from the posted primary outcome.
3. Trial Design
The registry describes a prospective, randomized, double-masked, parallel-group study of Vitagel during revision total knee arthroplasty. Its condition was failed total knee arthroplasty, and the planned comparison was Vitagel versus standard of care for surgical hemostasis. The study is listed as terminated, with enrollment of 8. The registry lists the study start as 2013-04 and primary completion as 2014-03. It does not report why the study was terminated.
The registry lists the phase as NA. It does not identify which participants or study personnel were masked, how randomization was generated or implemented, or how treatment allocation was concealed. Those design details are not reported in the registry record. The record also does not give a protocol-level account of the intervention or the standard-care procedures.
The primary outcome was transfusion requirements, with follow-up described as the duration of the hospital stay and an expected average of 12 weeks. That wording is recorded as stated; the record does not explain the relationship between hospital-stay follow-up and the expected average duration. It reports that data were not collected from enrolled participants. Consequently, the randomized design describes the intended comparison, not a completed analysis of comparative outcomes. No outcome estimate, uncertainty interval, or analysis result for the primary comparison is reported.
The brief summary also describes planned assessment of hemoglobin and hematocrit change, transfusion rates, pain, function, quality of life, and postoperative analgesic use. The registry lists no posted secondary outcomes and no analyses. It does not establish that these assessments were completed.
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 | Treatment Group | Control |
|---|---|---|
| STARTED | 3 | 5 |
| COMPLETED | 0 | 0 |
| NOT COMPLETED | 3 | 5 |
Analysis population for the primary outcome, as defined in the registry: Data were not collected from participants enrolled in the study
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 | Treatment Group | Control | Total |
|---|---|---|---|---|
| Participants analysed | 3 | 5 | 8 | |
| Age, Continuous | years | 64 (59 to 69) | 57.8 (48 to 66) | 60.1 (48 to 69) |
| Sex: Female, Male: Female | Participants | 2 | 2 | 4 |
| Sex: Female, Male: Male | Participants | 1 | 3 | 4 |
6. Primary Endpoint
The registry lists the primary outcome as Transfusion Requirements, measured over Participants will be followed for the duration of hospital stay, an expected average of 12 weeks..
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is transfusion requirements among patients managed with revision total knee arthroplasty. Transfusion is a clinically relevant outcome for a study intended to evaluate blood loss during surgery and recovery. The brief summary also describes hemoglobin and hematocrit change as measures related to blood loss, while the primary objective specifically focuses on whether transfusion requirements differ between the Vitagel and standard-care groups.
The record describes follow-up as lasting for the duration of the hospital stay, with an expected average of 12 weeks. It does not explain how transfusion requirements were operationalized: for example, it does not state whether the endpoint was a count of transfusions, the proportion receiving a transfusion, or another measure. The outcome unit, summary parameter, and measure of dispersion are not reported in the registry record.
Most importantly, the registry states that data were not collected from participants enrolled in the study. It therefore does not report group-level transfusion results or an estimate of the difference between groups. Without those results, the endpoint identifies the question the study was designed to address but does not establish what happened in either group or how precisely a group comparison could be estimated.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes a randomized comparison of Vitagel with standard surgical hemostasis, but it does not provide analyzable results for the primary endpoint. It states that data were not collected from enrolled participants. The primary outcome fields do not provide usable group estimates, and the record lists no analyses. Thus, the posted information cannot show whether transfusion requirements differed between groups or quantify the size or precision of any difference.
The enrollment entry is 8, but enrollment alone is not an outcome. It does not show how many participants contributed to a primary-endpoint analysis, and it cannot substitute for the missing transfusion data. The study is marked terminated; the reason for termination is not reported in the registry record. The record does not say whether data collection stopped before any outcome assessments, whether assessments were attempted but not recorded, or why participant data were unavailable. It states only that participant data were not collected.
There is no reported effect estimate, confidence interval, or p-value for the primary comparison. A confidence interval is a statistical way to express uncertainty around an estimated effect; it requires an estimate and relevant data. A p-value evaluates the compatibility of data with a specified statistical model or null hypothesis; it also requires observed data and an analysis. Neither can be interpreted for the primary endpoint from the posted results.
The safety entries are separate from the primary efficacy question. They record serious and other adverse events by group, with different numbers of participants listed as at risk. These entries should be read as descriptive safety counts, not as a test of the transfusion comparison or as a reliable estimate of comparative safety. The record does not report a safety analysis plan or inferential comparison.
Overall, the registry supports a description of the intended study design and its planned outcomes, along with limited adverse-event counts. It does not support a conclusion about the effect of Vitagel on transfusion requirements. The absence of outcome data is not evidence that the groups had the same outcomes, nor is it evidence of a difference. It leaves the primary question unanswered in the posted record.
9. Statistical Methods Explained
The registry identifies a prospective randomized parallel-group design with double masking. These terms describe the intended structure of the study: participants were to be assigned to one of two groups, and outcomes were to be assessed prospectively. Random allocation can help balance measured and unmeasured characteristics across groups on average, while masking can reduce some forms of measurement or treatment-related bias. These are general principles, not confirmation of how the procedures were implemented in this study. The method for generating the random sequence, allocation concealment, and the identities of those masked are not reported in the registry record.
What comparison was planned?
The intended contrast was Vitagel versus standard of care for surgical hemostasis during revision total knee arthroplasty. The primary outcome was transfusion requirements. To estimate a treatment contrast, a report would ordinarily present the outcome in each group and a defined comparison between them. The registry does not report those outcome data. It therefore provides no estimated contrast to interpret, whether as a difference in average outcome, a difference in event probability, or another measure.
The endpoint’s exact statistical form is not specified. The record gives no unit, parameter, or dispersion measure for transfusion requirements. It does not define the assessment rules or specify how the primary endpoint would be summarized. These details matter because different outcome definitions call for different statistical summaries and models. Without the endpoint definition and observed data, the appropriate analysis cannot be reconstructed from the registry.
What do uncertainty measures mean?
In general, a confidence interval describes a range of values compatible with the data and the method used to calculate it. Its width reflects precision: more uncertainty generally corresponds to a wider interval. A confidence interval is not reported for the primary outcome. Because no primary outcome estimate is available, there is no interval to interpret.
In general, a p-value describes how unusual observed data would be under a stated null hypothesis and model. It does not measure the probability that a treatment works, and it does not convey the size or clinical importance of an effect. No primary-outcome p-value or analysis is reported. The record does not report a statistical analysis plan, including the planned test, model, adjustment variables, or handling of assumptions.
What do the planning assumptions represent?
The sample-size assumptions describe a planning illustration rather than the trial’s documented design. They specify a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. The assumptions also distinguish time-to-event illustrations, which use a total event count, from other illustrations, which use participants per arm. These are general planning inputs. The registry does not report that these assumptions were used to design or conduct this study.
Planning illustrations answer a hypothetical question about the sample size associated with stated assumptions. They are not observed power, and they do not recover missing trial results. The registry reports no primary outcome data from which an observed effect can be assessed. The reason for termination and any original sample-size justification are not reported in the registry record. No inference about the study’s intended or achieved precision follows from the enrollment entry alone.
Why can over-dispersion matter?
As a general statistical concept, over-dispersion occurs when observed variability is greater than a model expects. If a count or rate outcome is analyzed under a model that understates its variability, uncertainty estimates can be too small and statistical evidence can appear stronger than warranted. Analysts may address this by selecting a suitable model or adjusting uncertainty estimates. The registry does not report an analysis model for transfusion requirements, and no data are available in the record to assess whether over-dispersion was relevant.
Likewise, model choice depends on how an outcome is measured and how observations are collected. A continuous measure, an event count, and a time-to-event outcome do not necessarily call for the same analysis. The registry’s primary endpoint description does not provide enough detail to determine which form applies. No model diagnostics or sensitivity analyses are reported.
What can be concluded from the posted methods?
The record establishes the intended randomized, double-masked, parallel-group comparison and names transfusion requirements as the primary endpoint. It does not document the operational details needed to reproduce the randomization or masking, nor does it provide a statistical analysis plan or primary results. General statistical methods can explain how a future or complete analysis might be interpreted, but they cannot replace the unreported outcome data. Accordingly, no effect estimate, precision assessment, or hypothesis test can be reconstructed from the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The brief summary describes multiple planned outcome domains: hemoglobin and hematocrit change, transfusion rates, pain, function, quality of life, and postoperative analgesic use. The registry identifies transfusion requirements as the primary outcome, lists 0 posted secondary outcomes, and reports 0 analyses. It does not say whether the other measures were collected, analyzed, or omitted after study termination.
When a study evaluates multiple outcomes or multiple statistical comparisons, the chance of at least one apparently notable result can increase. General methods for addressing multiplicity include identifying a primary outcome in advance and specifying how additional tests will be interpreted or adjusted. The registry names a primary outcome, but a multiplicity strategy is not reported in the registry record. No multiplicity-adjusted or unadjusted outcome analyses are posted.
Missing-data handling is also not reported. The record’s primary-outcome population statement says that data were not collected from participants enrolled in the study. It does not describe an analysis population, exclusions, reasons for unavailable measurements, imputation, or sensitivity analyses. The analysis population for the adverse-event entries is not described beyond the group-specific counts listed as at risk.
These omissions prevent assessment of whether outcome measures were selected or analyzed according to a prespecified plan, and whether missing data could have affected any estimate. Since primary outcome data and analyses are absent, there is no basis to evaluate the impact of multiplicity or missing-data assumptions on the trial’s comparative result.
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 |
|---|---|---|---|
| Treatment Group | 0 | 3 | 0.0% |
| Control | 1 | 5 | 20.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Treatment Group | 0 of 3 |
| Control | 0 of 5 |
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 |
|---|---|
| Treatment Group | 0 of 3 |
| Control | 0 of 5 |
Most frequent serious adverse event terms
| Event term | Organ system | Treatment Group | Control |
|---|---|---|---|
| Pulmonary Embolism, bilateral lower extremity deep vein thrombosis | Blood and lymphatic system disorders | 0 of 3 | 1 of 5 |
Serious events with the highest arm-level rate: pulmonary embolism, bilateral lower extremity deep vein thrombosis (20.0%).
The registry lists serious adverse events separately for the treatment and control groups. In the treatment group, 3 participants are listed as at risk, with 0 serious adverse events, 0 other adverse events, and 0 deaths. In the control group, 5 participants are listed as at risk, with 1 serious adverse event, 0 other adverse events, and 0 deaths. These are descriptive counts as recorded, not estimates from a reported comparative safety analysis.
The listed serious term is “Pulmonary Embolism, bilateral lower extremity deep vein thrombosis,” with 20.0% shown. The registry does not clarify the denominator or calculation associated with that percentage, so it should not be interpreted as a group-specific risk from the information reported. The term also does not establish a causal relationship to study treatment.
Safety counts should be interpreted in light of the listed at-risk groups and the absence of a reported analysis plan. The record does not provide event timing, severity details beyond the serious-event classification, follow-up completeness, or criteria used to determine relatedness. These entries do not resolve the primary transfusion question and cannot establish a comparative safety profile.
12. What the Result Does, and Does Not, Mean
The posted record shows that a prospective randomized comparison of Vitagel and standard surgical hemostasis was planned for revision total knee arthroplasty. It identifies transfusion requirements as the primary outcome and gives a brief description of additional outcomes that were intended for assessment. It also records that the study was terminated and that data were not collected from enrolled participants.
What the record does not show is a comparative result. There is no reported estimate for transfusion requirements, no confidence interval describing its precision, and no p-value for a test of group differences. The planned study question therefore cannot be answered from the posted outcome data. An absent estimate is not a finding of no difference, and it is not evidence that either approach performed better.
The enrollment entry of 8 does not change that interpretation. Enrollment is not a measure of treatment effect, and the record does not report outcome contributions by group. Nor does the adverse-event information provide an answer to the primary question: those counts concern safety, and no comparative safety analysis is reported.
The registry record can still be informative about the intended design, outcome priorities, termination status, and the limited safety counts it contains. It also makes clear that the planned efficacy assessment is unavailable in the posted results. The reason for termination and the circumstances that led to the absence of participant data are not reported in the registry record. Without those details, it is not possible to determine why the study did not yield a primary-outcome analysis.
Accordingly, the appropriate statistical interpretation is limited: the trial was designed to compare transfusion requirements, but the posted record contains no data with which to estimate that comparison. Any stronger conclusion about the relative outcomes of Vitagel and standard care would go beyond the reported evidence.
13. Why This Trial Matters Statistically
This study illustrates the distinction between a randomized design and an informative randomized result. Random allocation describes how groups are intended to be formed; it does not by itself provide evidence about the outcome. A treatment comparison requires outcome data, a defined measure, and an analysis that estimates the contrast with appropriate uncertainty. In this record, the intended comparison is clear, but participant outcome data were not collected.
The contrast between a named primary outcome and the absence of posted analyses is statistically important. Naming transfusion requirements establishes the focus of the planned efficacy question, but it does not supply an effect estimate. Likewise, enrollment of 8 describes the study’s enrollment entry, not the precision of an outcome analysis. Without measured outcomes and a documented analysis population, neither the magnitude nor uncertainty of a treatment contrast can be assessed.
The record also shows why safety counts should be kept distinct from efficacy results. Adverse-event entries can provide descriptive information, but a small set of group-specific counts without a reported comparative analysis cannot answer the primary transfusion question. Denominators, follow-up, event definitions, and analysis methods all affect how safety data should be interpreted.
Finally, planning assumptions and observed evidence serve different purposes. Sample-size planning illustrations describe hypothetical requirements under stated assumptions; they are not proof that a study had a particular probability of detecting an effect, and they do not substitute for outcome data. This case underscores the value of clear reporting of outcomes, analysis populations, statistical methods, and reasons for unavailable results. In their absence, a reader should distinguish carefully between what a study intended to test and what its registry record can actually establish.
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 primary limitation is that the registry states that data were not collected from participants enrolled in the study. There are consequently no usable primary outcome results with which to estimate transfusion requirements or compare the groups. Although enrollment is listed as 8, the record does not provide an outcome analysis population or explain how the enrollment entry relates to the at-risk groups reported for safety.
The study is marked terminated, but the reason for termination is not reported in the registry record. The record does not explain whether the planned outcome assessments were never conducted, whether data were collected but not entered, or whether other circumstances prevented analysis. These possibilities should not be treated as established explanations.
Several design and analysis details are also absent. The registry does not describe the randomization procedure, allocation concealment, who was masked, the operational definition of transfusion requirements, or the statistical analysis plan. It does not report missing-data methods, analysis populations, or multiplicity procedures. The primary follow-up description combines hospital-stay follow-up with an expected average of 12 weeks, without clarifying how those statements fit together.
The adverse-event information is limited to group counts and a listed serious-event term. Event timing, definitions, relatedness, and a comparative safety analysis are not reported. The percentage associated with the listed serious term has no stated denominator in the record. These limitations mean the safety entries cannot be read as a complete or adjusted comparison between groups.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Vitagel Revision Total Knee Arthroplasty — NCT01923805.
- Registry record last updated 2017-06-07; status last verified 2017-05.
- Results first posted 2017-06-07.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry describes a prospective, randomized, double-masked, parallel-group study of Vitagel versus standard care for surgical hemostasis during revision total knee arthroplasty for failed total knee arthroplasty. The primary outcome was transfusion requirements. Enrollment is listed as 8, and the study status is terminated. The registry lists the start as 2013-04 and primary completion as 2014-03.
The record states that data were not collected from participants enrolled in the study. It lists 0 secondary outcomes and 0 analyses, and does not report a primary-outcome estimate or statistical test. The reason for termination and the statistical analysis plan are not reported in the registry record. Safety entries include group-specific counts and a serious-event term, but no comparative safety analysis. The posted record therefore describes the intended study question and limited safety information without providing a result for the primary comparison.