Use of Knotless Suture for Closure of Total Hip and Knee Arthroplasties: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Use of Knotless Suture for Closure of Total Hip and Knee Arthroplasties (NCT00834483), a randomized na study. The primary outcome is Closure Time.

2. Clinical Question

The study was designed around a surgical process question: whether a knotless closure approach changes the time needed to close the wound compared with a traditional layered approach. Closure time is not itself a measure of long-term joint function or scar appearance. The registry also describes objectives concerning wound safety, cost, cosmesis, and the perceived presence of subcutaneous knots. These additional questions broaden the clinical context, but the available results do not provide quantitative findings for every stated objective.

The follow-up plan in the brief summary describes routine visits at 2, 6, and 12 weeks, concluding at the six month postoperative visit. The primary endpoint timeframe is also listed as 6 months. The record does not clarify how that timeframe applies to the closure-time measurement, which is an operative measure. Further detail about the timing and handling of the endpoint is not reported in the registry record.

3. Trial Design

The registry classifies NCT00834483 as a randomized, double-masked, parallel-group clinical trial. Its listed phase is NA, and the study status is completed. Rush University Medical Center is named as sponsor. The registry lists a start date of 2009-02 and a primary completion date of 2011-01.

The listed interventions are knotless suture for wound closure and layered traditional wound closure (monocryl). The arm descriptions use the labels Treatment Group and Control Group, rather than naming the techniques in those labels. In the primary endpoint results, the Treatment Group has n = 31 and the Control Group has n = 29. The record's brief summary describes the comparison as bidirectional barbed suture versus traditional layered closure, but uses vicryl for the traditional suture, so the naming is not fully consistent across the registry entry.

The primary endpoint is Closure Time, expressed as average time in minutes. The posted summary gives a mean and full range for each arm. The registry's primary endpoint description says that the trial evaluated closure time, complications, and length of surgery in primary total hip and knee arthroplasties. The record also lists Cost-analysis and Visual Analog Score, Cosmesis as secondary outcomes.

The primary endpoint population description includes a planning statement: a power analysis based on mean closure times by the 2 surgeons determined that 23 patients in each group would provide 90% power to detect a 50% difference in closure time. The sentence then begins to describe enrollment intended to account for loss to follow-up, but ends before the full account is given. The remainder of that enrollment rationale is not reported in the registry record. This planning statement is distinct from the results and does not establish the power achieved in the analyzed groups.

The registry does not report the randomization sequence, allocation concealment procedures, masking roles, or the analysis population definitions. It also does not report protocol deviations or the number of participants who completed each follow-up visit. Those design details should not be inferred from the randomized and double-masked classifications alone.

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: No participants were excluded except those that would not sign consent. 5 patients were excluded as they did not want to participate giving us 65 offers and 60 enrollments.

Overall Study

Analysis population for the primary outcome, as defined in the registry: A power analysis was performed based on mean closure times by the 2 surgeons and determined that a sample size of 23 patients in each group would provide 90% power to detect a 50% difference in closure time. To account for patients being lost to FU, we enrolled 29 to the traditional closure group and 31 to the barbed closure group

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 Closure Time, measured over 6 months.

Closure time measures the duration of the wound-closure process. The registry reports the endpoint in minutes and summarizes it as an average for each group, accompanied by the full range. The posted mean is 9.34 minutes in the knotless-suture Treatment Group and 13.57 minutes in the traditional-closure Control Group. The corresponding full ranges are 5.4 to 13.8 and 7.0 to 26.2.

As a general statistical point, an average gives a compact description of the central level of a measurement across participants. The range shows the lowest and highest values represented in the reported group summary, giving a sense of how widely individual observations varied. A range does not show the distribution between its endpoints, and it can be affected by extreme observations. The record does not provide a standard deviation or another measure of spread for closure time.

Closure time is relevant to the practical evaluation of a surgical technique because it describes an operative process. It is not interchangeable with wound complications, scar appearance, perceived knots, or total operating-room time. The registry identifies those broader considerations in its objectives or endpoint description, but the posted primary endpoint is closure time. The record does not report a separate estimate for length of surgery in the available results.

The endpoint timeframe is listed as 6 months, while closure time is a measurement taken during wound closure. The registry does not explain this timing label. Further detail on the precise measurement procedure, such as the start and stop definitions, is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is reported as a mean in each group, with a full range. In general, a mean is the arithmetic average of observed measurements and is useful for describing the central level of a continuous outcome such as time. A range identifies the smallest and largest observed values in the summary. It does not indicate how many observations lie near either endpoint or how values are distributed between them. The registry does not provide a standard deviation for closure time, so a reader cannot use the posted summaries to reconstruct the spread in the same way that a standard deviation would permit.

A group mean is not the same quantity as a between-group effect estimate. A comparative analysis would ordinarily report a contrast, such as a mean difference, together with a measure of uncertainty. A confidence interval, as a general statistical concept, gives a range of values compatible with the data and the assumptions of the analysis at a stated confidence level. The primary endpoint record does not post such a contrast or interval. It also does not post a primary p-value. Accordingly, the means and ranges can describe what was observed but cannot, by themselves, show how precisely the group contrast was estimated.

The cost endpoint is reported with a mean and standard deviation for each arm, along with a mean difference, an interval, and an unadjusted p-value. The posted mean difference is 39.96, with an interval from 32.9 to 47.02, and p < 0.001. An unadjusted p-value evaluates the observed data against a specified null comparison without accounting for the possibility that several outcomes or comparisons have been examined. The registry does not state the confidence level for the interval, the precise test used, or whether the cost comparison was prespecified in an analysis plan.

The record includes planning illustrations based on fractions of the observed cost effect. Those calculations use a two-sided significance level of 0.05, equal allocation, and a normal approximation. For planning for 100% of the observed effect, the illustration is 3 participants per arm for 80% power and 3 participants per arm for 90% power. For planning for 75% of the observed effect, it is 4 participants per arm for 80% power and 5 participants per arm for 90% power. For planning for 50% of the observed effect, it is 9 participants per arm for 80% power and 11 participants per arm for 90% power. These are planning illustrations based on the observed cost result, not observed power and not the trial's own design calculation.

The registry separately describes a design calculation for closure time. It states that 23 patients in each group would provide 90% power to detect a 50% difference, based on mean closure times by the 2 surgeons. This is a stated design assumption, not evidence that the primary comparison achieved that power. The complete enrollment sentence is not present in the record, and further sample-size assumptions are not reported in the registry record.

As a general concept, over-dispersion occurs when the variability in data is greater than expected under a statistical model. It can make standard errors too small if a model assumes less variability than the data contain. The registry does not identify an over-dispersion analysis or provide a model for the primary endpoint, so this concept should not be taken as a description of what happened in this trial.

Random allocation can support a fair comparison by balancing treatment assignment through chance, but the registry's classification alone does not establish how the allocation process was implemented or whether the analysis preserved the randomized groups. The record does not report the randomization method, allocation concealment, analysis population, handling of missing observations, or adjustments for differences between hip and knee procedures. It also does not describe an analysis model for the primary endpoint. These details are necessary for a fuller appraisal of the statistical comparison.

Finally, the planning figures for the cost outcome should not be read as a recommendation for a future study's sample size. They depend on the observed effect and stated calculation assumptions, and planning for a smaller fraction of the observed effect leads to different illustrations. A new study's design would need its own target effect, variability assumptions, allocation plan, and analysis strategy. Such a protocol is not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary endpoint and multiple secondary objectives, but it does not report a statistical plan for controlling the chance of false-positive findings across those outcomes. The cost analysis has an unadjusted p-value. The record does not state whether outcomes were tested in a hierarchy, whether adjustments were planned, or whether any outcome was designated as exploratory. The meaning of the unadjusted result should therefore be considered in the context of the wider set of outcomes described.

As a general statistical principle, multiplicity matters when several hypotheses are evaluated. If each is tested without an adjustment, the chance of at least one apparently noteworthy result can increase. This does not invalidate a specific result, but it affects how much confirmatory weight to place on it. The registry does not report enough information to determine the multiplicity strategy for this trial.

Missing-data handling is also not described. The record does not report how many participants missed follow-up visits, whether endpoint data were unavailable, how missing observations were handled, or whether any sensitivity analyses were conducted. The primary endpoint description mentions an intention to account for loss to follow-up in enrollment, but its sentence is incomplete. The registry does not report whether the final analysis used all randomized participants or a subset defined by outcome availability.

The record does not define analysis populations, such as an intention-to-treat or per-protocol population, and does not describe exclusions after randomization. It does not report a prespecified statistical analysis plan, interim analyses, or protocol deviations. Those items are not reported in the registry record and should not be inferred from the trial's randomized designation.

These reporting gaps limit assessment of whether the posted group summaries represent all randomized participants, whether missing data could affect the results, and how the secondary p-value should be interpreted. They also prevent a complete reconstruction of the primary analysis. The posted findings remain descriptive where no comparative analysis is reported.

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 3.4% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: fall (3.2%).

The registry reports serious adverse events among 31 at risk in the Treatment Group and 29 at risk in the Control Group. The listed serious-event counts are 1 and 0, respectively. Other adverse events are listed as 2 in the Treatment Group and 3 in the Control Group, with the same respective numbers at risk. These are event summaries as posted; the record does not explain whether the categories are mutually exclusive or whether each count refers to participants or events.

The registry lists Fall at 3.2% among the top serious terms. The record does not provide further context for that term in the posted safety summary, so it should not be used to infer the circumstances or consequences of an event. Death counts are not reported in the registry record.

These figures are descriptive, not a formal comparison of safety. The registry does not report a risk difference, confidence interval, or p-value for adverse events. With sparse counts, small changes in the observed event pattern can materially affect a comparison, and absence of a listed event in one group does not establish absence of risk. The record also does not describe event definitions, severity grading beyond the serious and other categories, follow-up completeness, or causal attribution.

Accordingly, the figures describe the adverse events recorded for the two groups in the registry. They do not by themselves establish whether one closure approach is safer, and they should be interpreted alongside the limitations in outcome reporting and analysis detail.

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

The primary endpoint results show that the posted average closure time was 9.34 minutes in the knotless-suture group and 13.57 minutes in the traditional-closure group. The ranges indicate that observed times varied within each group. These summaries describe the trial's reported measurements; they do not provide a statistical estimate of the difference or its precision. A primary comparison estimate and uncertainty interval are not reported in the registry record.

The result does not establish that the difference is statistically reliable, nor does it show what would be expected in another clinical setting. It also does not establish effects on wound complications, length of surgery, cosmesis, perceived knots, or longer-term recovery. Although some of these topics appear in the trial objectives, numerical results for them are not all posted. The cost endpoint is separate from closure time and should not be treated as a measure of clinical benefit.

As a general statistical distinction, a group-level average summarizes observed data but does not predict the exact outcome for an individual. The posted ranges also do not show the full distribution or reveal whether differences between groups reflect consistent shifts or a small number of extreme observations. The absence of a reported primary confidence interval makes it difficult to judge the precision of the apparent separation between means.

The safety counts provide another descriptive view, but they are not a substitute for a defined safety analysis. The record does not report comparative estimates or sufficient detail on event definitions and follow-up. Similarly, the design's randomized classification supports a comparative intent but does not fill in missing information about the actual analysis.

The most defensible reading is limited to what is posted: group averages and ranges for closure time, a separate cost comparison, and adverse-event counts. The results do not support broader conclusions about overall efficacy or safety. Important details about analysis methods, missing observations, multiplicity, and several outcomes are not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically useful as an example of the difference between reporting group summaries and reporting a complete comparative analysis. The primary outcome has means and ranges for each group, which allow a basic description of observed closure times. However, the registry does not post a primary effect estimate, uncertainty interval, or p-value. Without those elements, the precision of the primary comparison remains unclear.

The record also illustrates how a single study can have several different kinds of outcomes. Closure time is an operative process measure, cost is a resource measure, and cosmesis and adverse events address different aspects of the procedure. Evidence for one outcome cannot stand in for evidence about another. This distinction matters when study objectives are broad but the posted numerical results are partial.

Planning statements require similar care. The registry describes a design calculation for closure time and separately lists planning illustrations based on the observed cost effect. These are not interchangeable. A design assumption is not proof of achieved power, and calculations based on an observed effect are planning illustrations rather than measurements of the trial's evidential strength.

The record's incomplete reporting on analysis populations, missing data, multiplicity, and methods also shows why statistical interpretation depends on more than a mean and a p-value. These details help readers understand which observations contributed to an estimate, how uncertainty was calculated, and how multiple outcomes were considered. Their absence limits what can be concluded from the posted results.

For clinical researchers, the central statistical lesson is to distinguish descriptive findings, comparative estimates, and planning calculations. Each answers a different question. Here, the primary endpoint is descriptively summarized, the cost outcome has a reported unadjusted comparison, and several other objectives lack numerical results or analysis detail in the registry record.

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 specific to this registry record affect interpretation. The primary endpoint is reported as a mean and full range for each group, but no comparative estimate, uncertainty interval, or p-value is posted. The reader therefore cannot assess the precision of the primary contrast from the registry results alone.

The intervention naming is not fully consistent. The intervention listing identifies the traditional closure as monocryl, while the brief summary describes traditional layered vicryl closure. The record does not clarify whether these labels refer to the same protocol or reflect different descriptions. The primary result uses generic Treatment Group and Control Group labels, which require the arm descriptions to interpret.

The record lists 6 months as the primary endpoint timeframe even though closure time is an operative measurement, and it does not explain that timing. The description of the measurement procedure, including how closure time was defined, is not reported in the registry record. The primary endpoint description also mentions complications and length of surgery, but no corresponding quantitative results are posted with the primary summary.

Secondary reporting is incomplete: cost has a numerical comparison, while cosmesis has no quantitative result in the registry record. Another endpoint is noted as missing or not estimable for a two-arm comparison. The record does not provide an adjustment strategy for multiple outcomes or explain whether secondary tests were confirmatory.

Further limitations include absent details on allocation procedures, analysis populations, missing-data methods, follow-up completion, outcome definitions, and the statistical model. The primary sample-size narrative ends mid-sentence, so its full enrollment rationale is unavailable. These gaps prevent a complete appraisal of how the trial was conducted and how its reported results were derived.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Use of Knotless Suture for Closure of Total Hip and Knee Arthroplasties — NCT00834483.
• Registry record last updated 2014-09-11; status last verified 2014-09.
• Results first posted 2014-09-11.
• 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

NCT00834483 is a completed, randomized, double-masked, parallel-group trial sponsored by Rush University Medical Center. It compares knotless suture closure with traditional layered wound closure in primary hip and knee arthroplasty. The registry lists Closure Time, measured in minutes, as the primary endpoint and reports group means and full ranges.

The knotless-suture group mean is 9.34 minutes, with a range of 5.4 to 13.8; the traditional-closure group mean is 13.57 minutes, with a range of 7.0 to 26.2. A primary comparative estimate and its uncertainty are not reported in the registry record. The cost-analysis has a reported unadjusted comparison, while quantitative results for cosmesis are not reported in the registry record. Serious and other adverse-event counts are listed, without a formal comparative safety analysis.

Important details—including the primary analysis method, missing-data handling, analysis populations, and multiplicity strategy—are not reported in the registry record. The posted results therefore provide descriptive primary-endpoint information and partial secondary and safety reporting, rather than a complete statistical account of all stated objectives.