Evaluation of Closed Incision Negative Pressure Dressing (PREVENA) to Prevent Lower Extremity Amputation Wound Complications: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of Closed Incision Negative Pressure Dressing (PREVENA) to Prevent Lower Extremity Amputation Wound Complications (NCT03773575), a randomized na study. The primary outcome is Overall Rate of Wound Complications.

2. Clinical Question

3. Trial Design

The trial is registered as NCT03773575 and is titled “Evaluation of Closed Incision Negative Pressure Dressing (PREVENA) to Prevent Lower Extremity Amputation Wound Complications.” Thomas Jefferson University is listed as the sponsor. The registry describes a prospective, multicenter, two-arm, randomized controlled trial. Its allocation was randomized, its masking was none, and its model was parallel. The study status is completed.

The registry lists enrollment as 272. The primary outcome entries report 134 participants in the PREVENA group and 129 in the standard-care group. These are the group sizes recorded for the outcome; the registry record does not explain how those counts relate to the enrollment figure. The trial began on 2019-01-15, and the primary completion date is 2024-07-15.

Participants assigned to PREVENA received the PREVENA™ PEEL & PLACE™ Dressing Kit. The comparator group received sterile gauze supplemented with an Ace wrap. As the trial was unblinded, knowledge of assigned dressing was not masked. The registry does not report further details about allocation concealment, procedures for outcome assessment, or whether any outcomes were assessed by masked reviewers.

The main endpoint was a participant-level count of any wound complication within 30 days post procedure. Secondary outcomes include length of stay, return to the operating room, hospital readmissions, and several wound-specific complications. The study summary also identifies medical costs as an objective, but a cost outcome result is not reported in the registry record. The phase is listed as NA. A protocol, detailed eligibility criteria, original statistical analysis plan, and the trial’s own sample-size justification are not reported in the registry record.

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

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 Overall Rate of Wound Complications, measured over 30 days post procedure.

The primary endpoint, Overall Rate of Wound Complications, counts participants with at least one qualifying complication within 30 days post procedure. It is a composite: the qualifying events include skin or fascial dehiscence, seroma, lymph leak, superficial or deep infection using CDC Surgical Site Infection criteria, hematoma, ischemia, and necrosis. The registry records the outcome as a count of participants, rather than as the number of separate events. A participant with multiple qualifying complications would therefore still contribute to the participant count as an affected participant, although the detailed event-handling rules are not reported in the registry record.

A composite endpoint can capture several clinically relevant forms of wound difficulty in one outcome, rather than focusing on only one type. It can also make interpretation less specific: the overall result does not show which component is most responsible for the observed pattern. Component-specific outcomes are listed among the secondary outcomes, but the registry record does not report a complete component-level primary analysis or rules for selecting an event when more than one occurred.

The posted primary counts are 26 of 134 participants in the PREVENA group and 31 of 129 in standard care. These counts describe the recorded outcome, not a causal explanation for an event or a measure of its severity. The endpoint is limited to the stated 30-day timeframe; it does not by itself describe later wound outcomes.

7. Results Posted in the Registry

• Prevena: 19.4% (26/134) versus 24.0% (31/129) on control; risk difference -4.6 percentage points (95% CI -14.6 to 5.3), risk ratio 0.81 (0.51–1.28); unadjusted two-proportion z-test p = 0.362.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Length of Stay (LOS)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Prevena: mean 10.00 versus 9.60 on control; difference 0.40 (95% CI -1.31 to 2.11), standardized effect d = 0.06; z-test p = 0.646.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Prevena and the control. The interval gives the range of effects that remain compatible with the data.

30-day Return to Operating Room (ROR)

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Prevena: 3.7% (5/134) versus 8.5% (11/129) on control; risk difference -4.8 percentage points (95% CI -10.6 to 1.0), risk ratio 0.44 (0.16–1.22); unadjusted two-proportion z-test p = 0.104.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Prevena and the control. The interval gives the range of effects that remain compatible with the data.

30-day Hospital Readmissions

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Prevena: 9.0% (12/134) versus 11.6% (15/129) on control; risk difference -2.7 percentage points (95% CI -10.0 to 4.7), risk ratio 0.77 (0.38–1.58); unadjusted two-proportion z-test p = 0.475.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Prevena and the control. The interval gives the range of effects that remain compatible with the data.

The registry lists secondary outcomes covering length of stay, return to the operating room, hospital readmissions, and wound-specific complications. These outcomes broaden the clinical picture beyond the composite primary endpoint: some relate to healthcare use, while others describe particular forms of wound complication. The posted comparisons for length of stay, return to the operating room, and readmissions are unadjusted. A complete set of detailed numerical results for all listed secondary outcomes is not reported in the registry record.

Across the posted secondary comparisons, the estimates do not provide a consistent, precise basis for a conclusion separate from the primary result. They should be read as additional descriptive evidence, not as confirmation of a definitive treatment effect. The primary endpoint combines several kinds of wound events, whereas secondary outcomes can capture particular consequences or components. Similarity between a component outcome and the composite would not constitute independent confirmation, because the same participants and related events can contribute to both.

Multiplicity matters because examining several outcomes creates more opportunities for a result to appear notable by chance. An unadjusted p-value for an individual secondary comparison does not account for the full set of comparisons. A prespecified hierarchy, correction method, or distinction between confirmatory and exploratory outcomes is not reported in the registry record. Accordingly, secondary results carry less evidential weight than a prespecified primary analysis and should not be treated as stand-alone proof.

The registry lists other wound outcomes, including skin and fascial dehiscence, superficial and deep infection, and seroma. These measures can help describe which events make up the broader clinical picture, but their interpretation depends on definitions, completeness of ascertainment, and analysis methods. Those details are not reported in the registry record. Taken together, the secondary outcomes provide context around the main question, while the uncertainty in the primary estimate remains central.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Length of Stay (LOS)
• 30-day Return to Operating Room (ROR)
• 30-day Hospital Readmissions
• Incidence of Skin Dehiscence
• Incidence of Fascial Dehiscence
• Incidence of Superficial Skin Infection
• Incidence of Deep Skin Infection
• Incidence of Seroma

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary at the participant level: each participant is classified according to whether any qualifying complication was recorded within the specified follow-up. The group counts are 26 of 134 for PREVENA and 31 of 129 for standard care. A comparison of these proportions can be expressed in several ways. The risk difference subtracts the standard-care risk from the PREVENA risk, so a negative estimate means the observed proportion was lower in the PREVENA group. The posted risk difference is -0.046. This direction describes the estimate; it does not establish that the dressing caused the difference.

A risk ratio compares the two risks by division, while an odds ratio compares the odds of an event. These measures use different scales and should not be read as though their numerical values were directly interchangeable. The registry reports a risk ratio of 0.807 and an odds ratio of 0.761. Their intervals include the respective no-association values, so these relative measures also leave substantial uncertainty about the direction and size of a group difference. They are based on the same event data as the risk difference, rather than being separate replications.

An interval estimate communicates precision by indicating values that are reasonably compatible with the data under the analysis method. It is not a range containing every possible true value, and it does not assign a probability to the observed estimate being correct. The primary risk-difference interval extends from -0.146 to 0.053. Since it spans zero, the data are compatible with no difference as well as with differences favoring either group. The interval is more informative than the point estimate alone because it shows how much uncertainty remains.

The reported unadjusted p-value is 0.362. A p-value is calculated under a null model, commonly one that assumes no group difference. It describes how unusual data at least as discrepant as those observed would be under that model and the test assumptions. It is not the probability that the null model is true, and it does not quantify the clinical importance of an effect. “Unadjusted” means the reported value is not adjusted for other comparisons or covariates in the posted result. A multiplicity adjustment or adjusted model is not reported in the registry record.

The registry lists length of stay as a continuous outcome reported as a mean and standard deviation. For that outcome, a mean difference compares group averages. The standard deviation describes the spread of individual observations around a group mean; it is not the standard error of the mean or an interval estimate. The posted mean difference is 0.4, and its reported interval extends from -1.307 to 2.107. The unadjusted p-value is 0.646. This estimate is a group-average comparison and does not indicate that every participant had a similar length of stay.

For binary outcomes, a key statistical concern is that event counts can be sparse. With relatively few events, estimates of relative effects may be unstable and intervals can be wide. General statistical principle: sparse data can make model-based estimates sensitive to the method used, so the chosen method and its assumptions matter. The registry record does not report enough detail to identify the estimation method for each comparison or to assess robustness to alternative methods.

Randomization is intended to make assigned groups comparable on average, including with respect to factors that are not measured. It does not guarantee that every characteristic will be balanced in a particular trial, and it does not remove uncertainty caused by limited information. The parallel design compares outcomes between groups assigned to different dressing strategies. Because masking was none, participants and study personnel could know the assignment. General statistical principle: knowledge of assignment can influence measurement, reporting, co-interventions, or decisions, particularly for outcomes involving judgment. The extent of any such influence is not reported in the registry record.

Several design and analysis details needed for a fuller statistical appraisal are not reported in the registry record. These include the original sample-size calculation and its assumptions, the prespecified primary analysis method, any covariate adjustment, the analysis population, handling of missing outcomes, and the multiplicity strategy. The posted results should therefore be read as registry-reported comparisons, not as a complete account of the trial’s statistical plan.

Length of stay may have a distribution that is skewed or includes unusually long stays. General statistical principle: when data are substantially skewed, the mean and standard deviation may not describe a typical participant as well as other summaries. Over-dispersion, meaning variability larger than a model assumes, can also make model-based standard errors too small if not addressed. The registry reports a mean and standard deviation but does not report distributional checks or a method addressing skewness or over-dispersion. No additional assumptions about those data can be established from the posted summary.

11. Confidence Intervals and Precision

Precision concerns how tightly the data locate an effect estimate. For the primary risk difference, the estimate is -0.046 and the reported interval extends from -0.146 to 0.053. Because the interval includes zero, the posted data are compatible with no group difference. They are also compatible with a lower event proportion in PREVENA or a higher one. The point estimate alone gives a much narrower impression than the interval does.

The relative-effect intervals tell a similar story. The risk ratio is 0.807, with an interval from 0.509 to 1.281; the odds ratio is 0.761, with an interval from 0.423 to 1.371. Each interval includes the value representing no relative difference. The direction of the point estimates is not enough to establish that the underlying effect has that direction, and the intervals do not support a precise estimate of the magnitude.

A confidence interval is a statistical procedure for expressing uncertainty across repeated samples under its assumptions. It is not a guarantee that the true value lies within the displayed endpoints, nor does an interval that includes no difference prove that the groups are equivalent. Equivalence requires a prespecified margin defining what differences would be small enough to count as equivalent; such a margin is not reported in the registry record.

The unadjusted p-value of 0.362 should not replace the interval in interpretation. A p-value does not show whether an estimate is clinically important, and a result that does not cross a chosen significance threshold can still be compatible with effects that matter. The record does not report a clinically important difference threshold, so clinical importance cannot be inferred from statistical precision alone.

Precision is also limited by the available event information and by details that are not reported, including missing-data handling and the analysis population. The posted summaries do not give enough information to determine whether every randomized participant contributed to each analysis. These limitations make cautious interpretation of the interval appropriate.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are illustrative estimates based on the observed effect, not the trial’s original design calculation. The registry’s planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set at the stated fraction of the observed effect. The original trial’s sample-size assumptions and justification are not reported in the registry record.

For the binary outcomes and the length-of-stay outcome, the figures are participants per arm, not a total across both arms. A row describing 100% of the observed effect uses the full observed effect as the planning target; rows for 75% and 50% use smaller target effects. Smaller effects are harder to distinguish from random variation, so planning for a smaller effect requires more participants per arm. The estimates rise as the target effect becomes smaller.

The 80% power column represents a planning scenario in which the assumed study design would detect the specified effect in 80% of repeated trials, if the assumptions and effect were correct. The 90% power column uses a higher target probability of detection and therefore calls for more participants. These are design probabilities under assumptions, not guarantees for a particular trial. The estimates depend on the assumed effect, allocation, significance level, and approximation.

These figures are not observed power. They do not measure the chance that the completed trial’s result is true or that an effect exists. They are forward-looking planning illustrations based on the observed effect, which is itself uncertain. The registry does not report the sample-size justification used when the trial was designed, so these planning estimates should not be taken as evidence of the trial’s original intent or adequacy.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.240; treatment proportion p₁ = 0.194; average p̄ = 0.217.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5831 = 1.1429.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5822 = 0.4900.
4. n = (1.1429 + 0.4900)² / (-0.0463)² = 1,244.8, rounded up to 1,245 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.24031007751938                          # control proportion
p1 <- 0.194029850746269                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(3773575)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 1,245 (80% power), 1,666 (90% power)
 75% of observed effect: n per arm = 2,257 (80% power), 3,020 (90% power)
 50% of observed effect: n per arm = 5,171 (80% power), 6,922 (90% power)
power.prop.test: 1244.8 
Simulated power at n = 1,245 per arm: 0.802 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry reports an unadjusted p-value for the primary comparison and for the posted secondary comparisons. It does not report whether the trial prespecified a multiplicity strategy, such as a testing hierarchy, a familywise error adjustment, or a distinction between confirmatory and exploratory analyses. Without that information, the p-values should not be interpreted as though they necessarily account for all outcomes examined.

Missing-data handling is not reported in the registry record. The posted primary outcome counts list 134 participants in PREVENA and 129 in standard care, while registry enrollment is 272. The record does not explain the relationship between these entries, indicate whether any outcome values were missing, or describe how missing outcomes would have been classified or handled. No assumptions about complete follow-up or imputation can be made from the summaries alone.

The analysis population is also not reported in the registry record. It is not stated whether the analyses followed an intention-to-treat principle, included only participants who received the assigned dressing, or used another population definition. The record does not report exclusions from analysis or reasons for any exclusions. These details are important because analysis choices can affect the interpretation of a randomized comparison.

The registry lists no reported analyses in its analysis listing. It also does not report an interim-analysis plan, stopping rule, covariate-adjustment strategy, or prespecified statistical analysis plan. This absence of reporting does not establish that such plans did not exist; it means their contents cannot be evaluated from the registry record. The primary and secondary comparisons should therefore be read as the results posted in the registry, with the limits imposed by these missing analytic details.

Outcome definitions are partly described for the primary composite, including the use of CDC Surgical Site Infection criteria for infection. More detailed rules for adjudication, handling of multiple events, and completeness of ascertainment are not reported in the registry record. Such information would help assess whether outcomes were applied consistently between groups, particularly in an unblinded trial.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

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: worsening post-procedure pain (2.3%), delayed wound healing (1.6%), homorrhage from operative site (1.6%), sepsis (1.5%), skin dehiscence (1.5%).

The registry records serious adverse events for 11 of 134 participants in the PREVENA group and 14 of 129 in standard care. Deaths are recorded for 1 participant in each group. The registry also records zero other adverse events in each group. These are descriptive safety figures; they do not by themselves establish that the groups differ or that an event was caused by the dressing.

The listed serious-event terms include Worsening post-procedure pain at 2.3%, Delayed Wound Healing at 1.6%, Homorrhage from Operative Site at 1.6%, Sepsis at 1.5%, Skin Dehiscence at 1.5%, and Gastrointestinal Hemorrhage at 0.8%. The registry does not provide enough detail in these entries to infer the severity, timing, causal relationship, or overlap among terms. The percentages should be read as listed, without assuming a denominator or adding them together.

Safety comparisons require attention to how events were defined, collected, and attributed, as well as the follow-up period and the number of participants at risk. These details are not fully reported in the registry record. The counts therefore describe what was posted, not a complete comparative safety analysis.

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

The posted primary result describes a randomized comparison of PREVENA dressing with sterile gauze and an Ace wrap after lower extremity amputation. The event counts were 26 of 134 in the PREVENA group and 31 of 129 in standard care. The estimated risk difference was -0.046, but its interval extended from -0.146 to 0.053. This indicates that the estimate is uncertain and compatible with no difference as well as with differences in either direction.

The result does not establish that PREVENA prevents wound complications, nor does it establish that the two approaches are equivalent. A finding of no clear difference is not the same as evidence that any possible difference is negligible. Equivalence or noninferiority would require specific margins and prespecified methods, which are not reported in the registry record.

The primary endpoint is a composite of several postoperative wound problems. It gives an overall participant-level summary, but it does not identify which component accounts for the result. It also concerns the 30-day period stated for the endpoint, and cannot answer questions about later outcomes. The registry’s description of medical costs as a study objective is not accompanied by a posted cost result.

Random assignment supports a comparative interpretation, but it does not remove all limitations. The trial was unblinded, and the registry does not report the analysis population, missing-data methods, outcome adjudication details, or original statistical plan. Those omissions make it difficult to evaluate the robustness of the estimates or the extent to which the posted comparisons were prespecified.

The secondary outcomes and serious adverse-event entries add context, but unadjusted comparisons across multiple outcomes should be treated cautiously. The findings describe the posted data; they do not provide medical advice or determine which dressing should be used for an individual patient. Clinical decisions require broader evidence and patient-specific judgment beyond the registry results.

17. Why This Trial Matters Statistically

This trial addresses a statistical challenge common in surgical research: comparing interventions when outcomes are clinically important but occur in a limited number of participants. The primary endpoint combines several wound complications, allowing a broad outcome to be assessed while making the result less specific about the event types involved. Both features matter when choosing an endpoint and interpreting a composite measure.

The randomized design and parallel groups make a direct comparison possible, while the unblinded design is relevant because knowledge of assignment can affect care or outcome measurement. Reporting these design features helps readers distinguish what randomization can support from questions that depend on masking, ascertainment, and analysis procedures. The registry record does not report enough detail to assess those procedures fully.

The primary estimate illustrates why a point estimate and a p-value are not enough on their own. The direction of the risk-difference estimate favors fewer recorded events in the PREVENA group, but the interval spans no difference and effects in either direction. Considering the interval prevents overinterpretation of a directional estimate when its precision is limited.

The registry also includes secondary clinical outcomes and safety entries. Their presence can make the evidence more informative, but multiple outcomes increase the need for a prespecified analysis strategy. Without a reported multiplicity plan and analysis population, secondary comparisons should remain supportive and descriptive rather than being treated as independent confirmation.

Finally, planning illustrations based on the observed effect highlight how sample-size requirements depend on the effect a future study aims to detect. They are not a substitute for the original design rationale. The trial’s own sample-size justification is not reported in the registry record, reinforcing the importance of transparent protocol and analysis-plan reporting.

18. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record leaves several trial-specific uncertainties. Although enrollment is listed as 272, the primary outcome groups are reported as 134 and 129, and the record does not explain the relationship between enrollment and those outcome entries. It does not identify the analysis population or explain whether all randomized participants contributed to each outcome.

The study was unblinded. The record does not describe whether wound complications were assessed by independent reviewers, whether events were adjudicated, or how consistent application of the criteria was ensured. These omissions matter for outcomes that may involve clinical judgment, even though part of the infection definition references CDC Surgical Site Infection criteria.

The primary endpoint combines several event types. The overall result cannot reveal whether a particular component was more frequent, more severe, or more influential in the comparison. Although related component outcomes are listed, the registry does not report the full analysis details needed to assess them together with the composite. The posted time horizon is 30 days, so it does not characterize outcomes beyond that period.

Statistical reporting is limited: the original sample-size rationale, multiplicity strategy, missing-data handling, interim-analysis plan, analysis population, and detailed statistical analysis plan are not reported in the registry record. The registry also does not provide a posted medical-cost result despite identifying costs as an objective. These gaps prevent a full assessment of prespecification, robustness, and the breadth of conclusions supported by the trial.

The available secondary comparisons are unadjusted, and the registry lists no reported analyses in its analysis listing. The absence of those details is a reporting limitation; it does not establish that no additional analyses were conducted. Caution is warranted when interpreting the posted results as the complete analytic record.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Evaluation of Closed Incision Negative Pressure Dressing (PREVENA) to Prevent Lower Extremity Amputation Wound Complications — NCT03773575.
• Registry record last updated 2026-03-25; status last verified 2026-03.
• Results first posted 2026-02-12.
• 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.

22. Record Summary

NCT03773575 is a completed, prospective, multicenter, randomized, unblinded, parallel-group trial sponsored by Thomas Jefferson University. It compared PREVENA™ PEEL & PLACE™ Dressing Kit with sterile gauze supplemented by an Ace wrap after lower extremity amputation. Registry enrollment is 272, with a start date of 2019-01-15 and a primary completion date of 2024-07-15.

The primary outcome was any qualifying wound complication within 30 days post procedure. The registry reports 26 of 134 participants with an event in the PREVENA group and 31 of 129 in standard care. The estimated risk difference was -0.046, with an interval from -0.146 to 0.053 and an unadjusted p-value of 0.362. The interval spans no difference, so the primary result is not precise enough to establish a clear group difference.

The registry lists secondary outcomes and serious adverse events, but key details about the original statistical plan, analysis populations, missing data, and multiplicity are not reported in the registry record. The posted estimates should be interpreted with those limitations in mind.