Repair of Infected or Contaminated Hernias: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Repair of Infected or Contaminated Hernias (NCT00617357), a na na study. The primary outcome is Incidence of Wound Events.

2. Clinical Question

This is a descriptive question about events following a particular repair approach in a selected clinical setting. It is not a direct estimate of how the approach compares with another repair method, because no control group is listed. The study’s single-group design can record whether defined wound events occurred among participants, but without a comparator it cannot separate the observed event experience from differences in patient characteristics, clinical circumstances, or other care. The record’s stated focus also includes postoperative resumption of activities and hernia recurrence, while the primary endpoint is the incidence of wound events. Activities Assessment Scale is listed among the secondary outcomes. The registry record does not report results for those secondary outcomes.

3. Trial Design

The registry describes a multicenter, prospective evaluation of hernia repair using LTM in contaminated or infected sites. It identifies the intervention as Strattice Reconstructive Tissue Matrix and the study model as single group. The brief summary describes the study as interventional and observational, open label, single arm, and longitudinal. Those labels are reported as written; the registry record does not provide further detail to reconcile the interventional and observational descriptions.

Overall enrollment was 83. The primary-outcome description states that 80 patients were enrolled, received Strattice Reconstructive Tissue Matrix to support repair, and were included in the Intent to Treat population. The primary endpoint timeframe is postoperative follow-up up to 24 months. The registry lists the study as completed, with a start date of 2007-09 and primary completion in 2010-12. Its phase and allocation entries are NA, and masking is listed as none.

No comparator arm is reported. As a result, the design supports description of outcomes in the treated group but does not support a randomized treatment contrast. The registry summary says that three interim analyses were planned to examine surgical site events, postoperative resumption of activities, and hernia recurrence. Whether those analyses were conducted, and what they found, is not reported in the registry record. The record does not report a protocol-level sample-size justification or a complete statistical analysis plan.

Activities Assessment Scale is listed repeatedly among the secondary outcomes. The registry record does not give the corresponding outcome results or clarify the repeated listings. It also does not report further detail on eligibility criteria, the distribution of follow-up, or how incomplete follow-up was handled. These omissions matter when interpreting a prospective study: a study description explains the intended setting and follow-up, but an outcome conclusion also requires the observed outcome data and methods used to analyze them.

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: 83 subjects were enrolled, 3 were not implanted, resulting in 80 subjects implanted with device (ITT group).

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: 80 patients were enrolled and received Strattice Reconstructive Tissue Matrix to support the repair and were included in the Intent to Treat (ITT) population.

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: 83 subjects enrolled, of which 80 subjects were implanted. The ITT population is defined as subjects enrolled and implanted (n=80).

6. Primary Endpoint

The registry lists the primary outcome as Incidence of Wound Events, measured over Postoperatively up to 24 months.

The primary endpoint is the incidence of wound events, expressed in participants, over postoperative follow-up up to 24 months. The record defines a wound event as an event in the area of the hernia repair and repair site. The listed event types are seroma, hematoma, dehiscence, infection, abscess, fistula, and re-herniation.

In general, a composite endpoint groups multiple event types into one outcome. This can capture a wider range of clinically relevant postoperative events than a single-event definition, but the component events may differ in nature and seriousness. An overall composite count therefore does not, by itself, show which events drove the result. Component-level counts and clear rules for whether a participant can contribute more than one event help readers understand what the composite represents. Those details and results are not reported in the registry record.

The registry identifies 80 treated participants in the Intent to Treat population for this endpoint, but it does not report how many experienced a wound event. It also does not report a calculated incidence, uncertainty interval, or statistical analysis. Consequently, the endpoint definition and intended population are clear, but the observed primary outcome cannot be interpreted from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods help define what an outcome count represents, how uncertainty is described, and what comparisons a design can support. The registry record contains a binary primary outcome definition but no reported primary analysis. The explanations below describe general statistical concepts and distinguish them from analyses actually reported in this study.

What does a binary endpoint count?

In general, a binary endpoint classifies each participant according to whether an event occurred during a specified period. For this study, the endpoint is the number of participants with wound events, and the follow-up timeframe is postoperative up to 24 months. This participant-level framing differs from counting every event: one participant might experience more than one event, but the registry’s endpoint description does not report how repeated events were handled. The observed count and denominator are needed to estimate an incidence proportion. Although the record gives 80 participants in the primary-outcome population, it does not give the number who experienced a wound event.

What does an uncertainty interval convey?

In general, a confidence interval describes the range of values reasonably compatible with the observed data under a specified statistical method. It communicates precision, not certainty that the true value lies within a particular range. A narrow interval usually indicates greater precision than a wide interval, but the interval’s meaning depends on the design, outcome definition, and analysis assumptions. No confidence interval for the primary outcome is reported in the registry record. Since the primary event count is also absent, its statistical precision cannot be evaluated from the posted results.

What can a single-group study estimate?

In general, a single-group study can describe outcomes observed in its enrolled participants. It does not directly estimate a between-group treatment effect because there is no concurrent comparator group. An outcome observed after treatment may reflect several influences, and a single-group design cannot isolate the intervention’s contribution from those influences. The record lists a single-group model and no comparator. It therefore supports a descriptive study question, not a randomized comparison. Any interpretation should keep that design limitation separate from the clinical relevance of the outcome being recorded.

What is the role of the planned interim analyses?

The study summary says three interim analyses were planned to examine surgical site events, postoperative resumption of activities, and hernia recurrence. In general, interim analyses review data before the planned end of a study. Their timing, decision rules, and any adjustments to statistical testing can affect how results are interpreted. Those details are not reported in the registry record, nor does it report whether the planned analyses took place or their findings. The mention of a plan does not establish that interim results were produced or that any particular statistical procedure was used.

How should the planning illustrations be read?

In general, sample-size calculations are planning tools: they estimate how many participants may be needed under specified assumptions to detect a target effect with a chosen statistical power and significance level. They do not indicate whether a study actually observed an effect, and they are not observed power. The planning illustrations associated with the posted results are described as using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is described relative to the observed effect. These are hypothetical two-arm assumptions, whereas this study is listed as single group with no comparator. They should not be mistaken for the study’s own design or for its observed outcome analysis. The registry record does not report the protocol’s sample-size justification, and no numerical planning outputs are included in the registry information summarized in the record.

Over-dispersion is a general concern when count data vary more than a statistical model assumes; it can make standard errors too small and intervals too narrow if ignored. It is not identified as a method issue for this primary endpoint, which is defined as participants with an event rather than an event count, and the registry does not report a model fit or dispersion assessment. No p-value or adjusted analysis is reported for the primary endpoint. Statistical terms such as significance, adjustment, and model fit should therefore not be attributed to this study without a reported analysis.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("One Arm")
n      <- c(80)
events <- c(53)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  One Arm  80  53  66.2  54.8  76.4  55.4  75.7  55.3  75.7

11. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when several outcomes, comparisons, or repeated statistical tests are examined. In general, conducting many tests can increase the chance of finding an apparently notable result even when there is no corresponding underlying effect. Approaches to address multiplicity may include defining a primary endpoint in advance, adjusting inference across tests, or treating secondary results as exploratory. Which approach is appropriate depends on the study question and analysis plan.

The registry names incidence of wound events as the primary outcome and lists Activities Assessment Scale among the secondary outcomes. Its summary also says three interim analyses were planned, covering surgical site events, postoperative resumption of activities, and hernia recurrence. The registry record does not report whether any interim analyses were conducted, how many comparisons were made, or whether multiplicity adjustments were planned or used. It does not provide a statistical analysis plan that would answer those questions.

The record gives the primary-outcome population as 80 participants but does not report primary outcome results or an analysis population for the secondary measures. Overall enrollment was 83. The registry record does not explain the difference between overall enrollment and the primary-outcome population, or report whether missing outcome data occurred, how much data were missing, or how any missing data were handled. It also does not report the timing or completeness of follow-up for individual participants.

These omissions prevent assessment of how missing information, interim looks, or multiple outcomes may have influenced the reported evidence. They do not establish that analyses were improperly conducted; the registry record simply does not report the needed details. A reader should distinguish the stated endpoint and planned analyses from completed analyses and their results, which are not reported.

12. 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

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: wound infection (11.2%), incisional hernia (8.8%), ileus (6.2%), seroma (5.0%), urinary tract infection (5.0%).

The adverse-event record lists the Strattice group with 80 participants at risk for serious adverse events and 50 affected. For other adverse events, 80 were at risk and 20 were affected. These are reported participant counts. The record lists serious-event terms with percentages: wound infection, 11.2%; incisional hernia, 8.8%; ileus, 6.2%; seroma, 5.0%; urinary tract infection, 5.0%; and atrial fibrillation, 3.8%.

These entries should be read as the registry’s safety reporting, not as an estimate of comparative risk. There is no control group, and the record does not report a comparator-based analysis. The listed terms may not represent every adverse event, and the record does not clarify whether a participant could contribute to more than one term. It does not report deaths. The serious-event counts and listed terms are separate from the primary endpoint result; no primary wound-event count or analysis is reported.

In general, adverse-event counts describe what was recorded in a study population. They do not, on their own, establish that an event was caused by the intervention or show how its frequency compares with another approach. The registry record does not report further details on event attribution or duration.

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

The registry record documents a prospective, multicenter, single-group evaluation of Strattice Reconstructive Tissue Matrix for contaminated or infected hernia repair. It defines wound events as events in the hernia repair area and identifies postoperative follow-up up to 24 months. These details clarify the intended clinical setting and outcome, but they do not provide the primary endpoint result. The number of participants with a wound event, the corresponding incidence, and an uncertainty interval are not reported.

Accordingly, the posted information does not establish a particular frequency of wound events in the primary-outcome population. It also does not show whether that frequency is higher or lower than it would be with another method of repair. A single-group evaluation has no control arm for a treatment comparison, and the registry lists no randomized allocation. The adverse-event counts and listed event-term percentages add safety-reporting information, but cannot fill the gap in the primary outcome analysis or provide a comparative estimate.

In general, clinical interpretation depends on the outcome definition, the completeness of follow-up, the observed data, and the study design. Here, the definition and planned timeframe are described, while the outcome count, analysis, and missing-data details are not. This distinction is important: absence of a reported result is not evidence that events did or did not occur. It means the registry record does not provide the information needed to quantify the primary result.

The study summary mentions planned interim analyses, but does not report whether they occurred or what they found. The registry also does not report a protocol-level sample-size justification or a full statistical analysis plan. Conclusions should therefore remain descriptive and limited to the design and results that are actually recorded. No conclusion about comparative effectiveness or causation can be drawn from this single-group record.

14. Why This Trial Matters Statistically

This study raises a useful statistical distinction between a clearly specified clinical outcome and a reported analysis of that outcome. The registry defines wound events, gives a follow-up timeframe, and identifies the primary-outcome population. Those elements make the intended measurement understandable. Yet the primary event count and analysis are not reported. A defined endpoint alone cannot tell readers how often it occurred or how precisely it was estimated.

The single-group structure is also central to interpretation. Descriptive outcome data can characterize what occurred among enrolled participants, but a comparison requires a reference group and appropriate methods. Without a comparator, the record cannot estimate a difference attributable to one repair approach relative to another. This is a design limitation, not a judgment about the relevance of the clinical question.

The record also illustrates why safety summaries and primary outcomes need to be read separately. Adverse-event counts and percentages provide information about recorded events, but they do not replace a missing primary endpoint analysis. In general, readers need to know how event terms were defined, whether individuals can appear in multiple categories, and how complete follow-up was. Those details are not reported in the registry record.

Finally, planned interim analyses and sample-size illustrations should not be mistaken for completed evidence. The registry notes intended interim reviews, while actual analyses and results are not reported. The planning assumptions described for sample-size illustrations do not match the listed single-group design and are not a record of observed power. Keeping design, planning, outcomes, and inference distinct is essential to an accurate statistical reading.

15. 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 most important trial-specific limitation in interpreting the registry record is that the primary endpoint is defined but its result is not reported. There is no number of participants with wound events, incidence estimate, confidence interval, or primary outcome analysis. Without those data, the intended primary clinical question cannot be answered quantitatively from this record.

The study is listed as single group, with no comparator and no randomized allocation. It can therefore describe outcomes among participants who received Strattice, but it cannot directly compare those outcomes with another repair approach. The registry’s description uses both interventional and observational terminology; it does not provide further detail to resolve that characterization. The record also does not report eligibility criteria or information sufficient to assess how representative the enrolled group was of other patients undergoing hernia repair.

Although the primary endpoint timeframe is postoperative up to 24 months, the record does not report participant-level follow-up completeness, missing outcome data, or how incomplete follow-up was handled. Overall enrollment was 83, while the primary-outcome description identifies 80 participants in the Intent to Treat population; the registry record does not explain this difference. The study summary says interim analyses were planned, but whether they occurred and how they were conducted are not reported. A complete statistical analysis plan and protocol-level sample-size justification are also not reported in the registry record.

Safety reporting has its own limits: event attribution and overlap among listed terms are not clarified, and deaths are not reported. These gaps constrain interpretation of the safety counts as well as the primary outcome. They are limitations of the information available in the registry record and should not be treated as evidence that an unreported analysis or event did not occur.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Repair of Infected or Contaminated Hernias — NCT00617357.
• Registry record last updated 2015-12-01; status last verified 2015-10.
• Results first posted 2015-12-01.
• 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.

19. Record Summary

The registry record describes a completed, prospective, multicenter, open-label, single-group evaluation of Strattice Reconstructive Tissue Matrix for contaminated or infected hernia repair. Overall enrollment was 83, and the primary-outcome description identifies 80 participants in the Intent to Treat population. The primary endpoint is incidence of wound events through postoperative follow-up up to 24 months.

The registry does not report the primary wound-event count, an incidence estimate, or an analysis. It lists adverse-event counts for the Strattice group and several serious-event terms with percentages, but no comparator is available. The study summary mentions three planned interim analyses; whether they occurred and what they found are not reported. Missing-data handling, a complete statistical analysis plan, and a protocol-level sample-size justification are not reported in the registry record. The design supports descriptive interpretation only, and the primary outcome cannot be quantified from the posted record.