Evaluation of 3D Visualization for Total Colectomy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of 3D Visualization for Total Colectomy (NCT02370056), a randomized na study. The primary outcome is Operating Time.

2. Clinical Question

3. Trial Design

NCT02370056, titled “Evaluation of 3D Visualization for Total Colectomy,” was a completed randomized, parallel-group trial sponsored by The Cleveland Clinic. It compared 3-dimensional visualization with conventional 2-dimensional visualization for total laparoscopic abdominal colectomy in patients diagnosed with ulcerative colitis. The registry lists no masking. The trial began in 2015-03, and primary completion was recorded as 2019-05-17. The phase field is listed as NA.

The registry records 53 participants enrolled. The operating-time outcome summaries include 27 participants in the 3D group and 26 in the 2D group. The arm descriptions refer to laparoscopic surgical video systems, but the available descriptions are truncated. Further procedural details, the allocation sequence method, and whether allocation was concealed are not reported in the registry record.

The primary outcome was operating time, specified as a mean measured in minutes, with a timeframe of 180 minutes. Major complication was the listed secondary outcome. The registry lists two outcome measures, but only one secondary outcome is identified by name in the posted results. The number of reported analyses is zero in the record, and no analysis descriptions are listed. Thus, the posted comparisons can be described, but the full analysis workflow and any additional planned outcomes cannot be reconstructed from this record.

The record does not describe a sample-size justification for the original trial, the intended target enrollment, or the statistical assumptions used when designing it. The later sample-size calculations are planning illustrations based on the observed effects, not evidence about the original design. Further information on trial conduct, participant flow, and analysis populations is 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 Operating Time, measured over 180 minutes.

Operating time is the duration of the operation, as a continuous measure in minutes. The registry defines the outcome as total operating time and lists a timeframe of 180 minutes. A continuous endpoint retains information about the amount of time recorded for each operation, rather than reducing the comparison to whether a participant crossed a yes-or-no threshold.

Mean operating time offers a direct way to compare the average duration between the two visualization groups. The registry reports a mean and standard deviation for each group. The mean describes the group average, while the standard deviation describes how dispersed individual operating times were around that average. The mean difference then expresses the contrast between group averages in the units of the outcome, minutes.

Operating time was relevant to the rationale recorded for the trial: the anticipated advantages of 3D visualization included greater accuracy and speed in manual skills. That rationale is not itself evidence that a difference occurred. The endpoint records duration; it does not directly measure accuracy, learning curve, or safety. Major complication was separately listed as a secondary outcome, so it should not be conflated with the primary operating-time measure.

The registry does not report a clinically important threshold for operating time, nor does it describe how the 180-minute timeframe was applied in data collection. It also does not specify whether particular portions of the procedure were excluded from the total time. Interpretation therefore rests on the stated endpoint definition and the posted summary statistics.

7. Results Posted in the Registry

• 2D Visualization: mean 82.70 versus 75.30 on control; difference 7.40 (95% CI -11.44 to 26.24), standardized effect d = 0.21; z-test p = 0.442.

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.

Major Complication

• 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:
  • 2D Visualization: 30.8% (8/26) versus 29.6% (8/27) on control; risk difference 1.1 percentage points (95% CI -23.6 to 25.9), risk ratio 1.04 (0.46–2.35); unadjusted two-proportion z-test p = 0.928.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between 2D Visualization and the control. The interval gives the range of effects that remain compatible with the data.

Major complication is the listed secondary endpoint. The posted counts are equal across the two groups, and the unadjusted comparison does not indicate a clear separation. The uncertainty around the comparison remains important: the available sample and event counts do not establish that the underlying complication risks are equal or that a difference is absent.

This secondary result provides a separate perspective from operating time. The primary endpoint concerns the mean duration of an operation, while major complication concerns whether a participant had the recorded event. They capture different aspects of the comparison, so the secondary finding does not confirm or explain the operating-time result. In particular, the record does not provide evidence that any difference or lack of difference in operating time caused a difference in complications.

The registry lists no reported secondary analyses. The unadjusted result therefore has limited context about how the endpoint was defined, whether additional analyses were planned, or how multiplicity was handled. When several outcomes or comparisons are examined, the chance of observing an apparently notable result by chance can increase. An adjustment or a prespecified hierarchy can address that issue, but neither is described in the registry record. For that reason, an unadjusted secondary comparison should generally carry less weight than a clearly prespecified primary analysis, especially when the record does not document the broader analysis plan.

The trial reports only one named secondary outcome in the posted information, although the registry records two outcome measures in total. The additional outcome is not identified by name in the posted results. It is therefore not possible to assess whether the available secondary result represents the full set of outcomes considered, or whether other analyses were planned but not reported. This uncertainty about the outcome record is distinct from the statistical uncertainty in the major-complication estimate itself.

Overall, the secondary information does not provide a precise independent answer that resolves the primary operating-time comparison. It should be read as a limited, unadjusted comparison that is compatible with a range of underlying effects, rather than as a conclusive safety or equivalence finding.

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

• Major Complication

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous, so the registry reports each group's mean operating time and standard deviation. A mean gives the arithmetic center of the observed times; a standard deviation describes their spread. These quantities answer different questions: a difference between means concerns the average contrast, while the standard deviations indicate how variable operating times were among participants. The trial's reported group sizes are 27 for 3D visualization and 26 for 2D visualization.

What does the mean difference represent?

The posted mean difference compares the 2D group with the 3D group. Its estimate is 7.4 minutes. A positive value under this ordering corresponds to a higher mean in the 2D group, consistent with the reported group means of 82.7 and 75.3 minutes. The difference is expressed in minutes, which makes the estimate interpretable in the endpoint's original units. The record does not provide a threshold for deciding how large a difference would matter clinically.

What does the confidence interval add?

A confidence interval gives a range of values compatible with the data and the statistical method, under its assumptions. The 95% interval for the mean difference runs from -11.44 to 26.24 minutes. Because it includes zero, the data are compatible with no average difference as well as with differences in either direction. Its breadth signals that the estimate is not highly precise. A confidence interval is not a guarantee that the true value lies inside this particular interval, and it does not assign a probability to each possible value.

What does the p-value describe?

The unadjusted p-value for operating time is 0.442. A p-value is calculated under a statistical model that assumes no difference between groups and measures how unusual the observed result, or a more extreme one, would be under that model. It is not the probability that the null hypothesis is true, and it is not a measure of the size or importance of the effect. The word unadjusted indicates that this posted value is not adjusted for multiple comparisons. The registry does not report a multiplicity procedure.

Why does variation matter?

Individual operating times vary. When observations are more dispersed, the group averages are generally estimated with less precision than they would be with less variation, all else equal. The standard deviations of 30.8 minutes and 38.6 minutes show the observed spread in the two groups. Standard errors of 5.927 and 7.57 are also listed for the two group means. A standard error describes the sampling uncertainty in an estimated mean; it is not the spread of individual participant times. These summary measures help explain why a point estimate alone cannot convey how certain the comparison is.

General statistical explanation: in a two-group comparison of means, the uncertainty of a mean difference depends on the variation within groups and the number of observations contributing to each mean. The comparison is reported as an unadjusted mean difference. The registry does not describe whether assumptions about the distribution of operating time were checked, whether an alternative analysis was prespecified, or how any departures from model assumptions were handled.

How should the secondary comparison be understood?

Major complication is a binary outcome: each participant either was or was not counted as having a major complication for the posted summary. The record lists 8 affected participants in each group. The comparison uses a risk difference, a contrast between group proportions, and reports an unadjusted p-value of 0.928. The confidence interval for that difference crosses zero and includes values in either direction. That uncertainty means the equal observed counts should not be read as proof that the underlying risks are equal.

For binary outcomes, precision depends not only on the number of participants but also on how many events are observed. With relatively few participants and events, estimates of group differences can remain uncertain. General statistical explanation: confidence intervals for a risk difference describe a range of plausible absolute contrasts, whereas relative measures such as risk ratios express a contrast on a ratio scale. The record lists relative measures as well, but their estimates have more than three decimal places; they are not repeated. No reported secondary analysis is listed beyond the posted comparison.

The analyses shown in the registry are unadjusted. No information is reported on covariate adjustment, stratification, handling of surgeon effects, or modeling of repeated or clustered observations. The arm descriptions refer to procedures performed by surgeons, but the available text is truncated and does not provide a complete analytic account of how surgeon-level variation was handled. Such details could affect interpretation, but they cannot be inferred from the posted summaries.

The registry record also does not report an analysis population definition, a plan for missing outcome data, or a description of exclusions from analysis. A posted group size does not by itself establish whether all randomized participants contributed complete data or whether analysis followed intention-to-treat principles. The estimates should therefore be read as the comparisons reported, without assuming unreported methods.

11. Confidence Intervals and Precision

The operating-time estimate is 7.4 minutes for the 2D group relative to the 3D group. Its 95% confidence interval, -11.44 to 26.24 minutes, is wide enough to include a possible average difference favoring either group as well as a value of no difference. This is the central precision finding: the point estimate has a direction, but the interval leaves substantial uncertainty about the magnitude and direction of the underlying contrast.

The interval is in minutes, so its endpoints can be interpreted on the same scale as the outcome. The lower endpoint corresponds to a mean difference in the opposite direction from the point estimate; the upper endpoint corresponds to a larger difference in the point-estimate direction. Because the registry does not state a clinically important threshold, it is not possible to classify the full interval as either clinically trivial or clinically important based on the record alone.

The group means are based on 27 and 26 participants, and the standard deviations are 30.8 and 38.6 minutes. These figures provide context for why the group comparison remains uncertain: there is meaningful variation in operating times, and the sample is limited. The confidence interval communicates that uncertainty more fully than the point estimate or p-value alone. It should not be treated as a range that contains every plausible value, nor as proof that values outside it are impossible.

The major-complication comparison is also imprecise. The same number of participants was counted in each arm, but the posted confidence interval for the risk difference extends across zero. It therefore does not establish that the risks are the same. Taken together, the intervals support cautious interpretation of both endpoints: neither comparison has a narrow estimate that settles the size of the difference.

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 sample-size planning figures are participants per arm for both the operating-time outcome and the major-complication outcome; they are not total event counts. They are planning illustrations based on the observed effect, not the original trial's design assumptions. The stated calculation assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to the stated fraction of the observed effect. The original trial's sample-size assumptions are not reported in the registry record.

For operating time, planning for 100% of the observed effect gives 349 participants per arm for 80% power and 466 participants per arm for 90% power. Planning for 75% of the observed effect gives 619 per arm for 80% power and 829 per arm for 90% power. Planning for 50% of the observed effect gives 1,393 per arm for 80% power and 1,864 per arm for 90% power. The corresponding major-complication planning figures are much larger: 25,479 and 34,108 participants per arm for 100% of the observed effect, 45,174 and 60,475 for 75%, and 101,368 and 135,702 for 50%, for 80% and 90% power respectively.

In plain terms, an 80% power target means that, if the assumed effect and calculation model were correct, a study of the stated size would have an 80% chance of detecting that effect at the stated significance level. The 90% column represents a higher chance under those same assumptions and therefore requires a larger planned sample. Smaller effects require more participants to detect than larger effects.

These figures are not observed power. They are planning illustrations calculated from the observed effects, which are uncertain estimates from this trial. The trial's own enrollment and design choices should not be judged as though these later illustrations were its original plan.

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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 7.400; pooled standard deviation σ = 34.842.
2. n = 2 × (1.96 + 0.842)² × 34.842² / 7.400² = 348.0, rounded up to 349 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
delta <- 7.40000000000001                      # observed difference in means
sigma <- 34.8424014840606                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2370056)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 349 (80% power), 466 (90% power)
 75% of observed effect: n per arm = 619 (80% power), 829 (90% power)
 50% of observed effect: n per arm = 1,393 (80% power), 1,864 (90% power)
power.t.test: 349 
Simulated power at n = 349 per arm: 0.799 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-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

Multiplicity arises when a study evaluates more than one outcome, contrast, time point, or subgroup. If each is tested separately without adjustment, the chance of at least one result appearing statistically notable by chance can increase. The registry names operating time as the primary outcome and major complication as a secondary outcome, and it records two outcome measures in total. However, it does not provide a complete list of all planned analyses or state how multiplicity was addressed.

The posted p-values are unadjusted. No adjustment method, testing hierarchy, or prespecified strategy for interpreting multiple outcomes is reported in the registry record. This does not establish that no such plan existed outside the registry; it means the record does not document one. The secondary outcome should consequently be treated as supportive or descriptive rather than as a stand-alone confirmatory result.

Missing-data methods are also not reported in the registry record. The posted outcome group sizes are 27 and 26 for operating time, and the same group sizes appear in the complication summaries. The record does not state whether any measurements were missing, how missingness was assessed, whether participants were excluded from an outcome analysis, or how missing observations were handled. Matching group counts to enrolled group summaries does not by itself describe the missing-data process.

The analysis populations are not defined. The record does not say whether analyses included all randomized participants, only participants who underwent surgery, or another population. It also does not describe any protocol deviations or exclusions. Without those details, the reported estimates can be described as posted but cannot be assigned to a particular intention-to-treat or per-protocol framework.

Finally, the registry does not report details of the randomization method, allocation concealment, adjustment for surgeon, or checks of statistical assumptions. These omissions limit assessment of possible sources of bias and of the robustness of the analyses. They should be understood as missing documentation in the registry record, not as evidence that a particular procedure or analysis was or was not performed.

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 0% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: post-operative ileus (14.8%), readmission (11.1%), portal vein thrombosis/deep vein thrombosis (7.7%), surgical site infection (7.7%), wound dehiscence (3.7%).

The registry reports serious adverse event counts for each arm: 8 participants at risk and affected in the 3D group, and 7 participants at risk and affected in the 2D group. No deaths are reported in either group. The record also lists zero other adverse events in each group. These are counts, and they should be read in the context of the group sizes rather than as a complete description of all possible harms.

The listed serious-event terms and percentages include Post-operative ileus (14.8%), Readmission (11.1%), Portal vein thrombosis/Deep vein thrombosis (7.7%), Surgical Site Infection (7.7%), and Wound Dehiscence (3.7%). The registry does not clarify the arm-specific attribution of these terms in the information recorded. They should not be interpreted as arm-specific rates or assumed to be mutually exclusive categories.

Adverse-event reporting is distinct from the major-complication endpoint, even though the outcomes may overlap in some cases. The registry does not provide detailed event definitions, severity grading beyond the serious-event label, timing, or a complete narrative of event assessment. These summaries therefore describe what was posted, but do not establish comparative safety with precision.

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

The trial gives a randomized comparison of 3D and conventional 2D visualization during total laparoscopic abdominal colectomy for ulcerative colitis. The observed mean operating time was lower in the 3D group than in the 2D group, and the mean difference estimate was 7.4 minutes in the direction of longer time with 2D. However, the confidence interval is broad and includes values consistent with differences in either direction. The comparison does not provide a precise estimate of the underlying difference.

The result does not show that the approaches are equivalent. Equivalence requires an explicitly defined margin and an analysis designed to assess whether the confidence interval lies within that margin; neither is reported in the registry record. Nor does the result establish that one approach is superior. The posted p-value is not a probability that either method is better, and a result that is not conventionally statistically significant does not prove absence of an effect.

The major-complication counts were the same in the two groups, but the comparison is uncertain and the registry does not document an equivalence framework. Equal observed counts do not demonstrate equal risks. The safety summaries likewise cannot establish that the approaches have identical safety profiles. The posted adverse-event information is limited in detail and does not resolve the comparative uncertainty.

The findings apply to the trial described in the registry: patients with ulcerative colitis undergoing total laparoscopic abdominal colectomy in this randomized comparison. The record does not report enough detail to determine how results might vary by surgeon, patient characteristics, or operative circumstances. It does not report learning-curve outcomes, accuracy measures, or a full account of safety assessment as primary outcomes. The rationale in the brief summary should not be mistaken for results on those measures.

In practical statistical terms, these data are compatible with a range of possibilities. They provide an observed direction and size for the mean contrast, but the uncertainty leaves room for a smaller, absent, or larger difference. More precise evidence would require information and data beyond what is reported in this registry record. No clinical recommendation follows from these statistical summaries alone.

17. Why This Trial Matters Statistically

This trial is statistically instructive because a randomized design and a point estimate do not automatically produce a decisive result. The operating-time means differ, but the confidence interval is broad relative to the estimate and spans values on both sides of no difference. Reading the interval alongside the point estimate prevents the direction of the observed means from being mistaken for a settled conclusion.

The comparison also illustrates why endpoints need to be interpreted on their own scales. Operating time is continuous and reported in minutes, while major complication is binary and represented by participant counts and a risk difference. The same sample can yield different levels of information for these outcomes because their measurement and event patterns differ. Equal complication counts, for example, do not guarantee a precise comparison of underlying risks.

The planning illustrations highlight the effect of uncertainty in an observed effect. They show that planning around smaller effects requires larger samples under the stated assumptions. Those calculations are not a substitute for the trial's original design rationale, which is not reported, and they are not evidence of the probability that this completed trial detected an effect.

The record also demonstrates the importance of reporting a full analysis plan. Information about missing data, analysis populations, multiplicity, and surgeon-level handling is not reported. Without it, readers can interpret the posted summaries while recognizing that key aspects of robustness and bias assessment remain unclear. Transparency about these methods would help distinguish uncertainty inherent in the sample from uncertainty about how the results were obtained.

For clinical researchers and biostatisticians, the central lesson is to separate the observed contrast, its precision, and the scope of the record. A modest-looking point estimate, a non-small p-value, and equal event counts each answer different questions; none alone establishes equivalence or absence of an effect.

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 trial's sample includes 53 participants, with operating-time summaries for 27 in the 3D group and 26 in the 2D group. The confidence interval for the primary comparison is broad, limiting precision. This is particularly relevant when the aim is to distinguish between modest differences, since the record does not report a clinically important operating-time threshold against which to interpret the interval.

The registry's arm descriptions are truncated. They refer to operations by surgeons, but do not provide a complete account of the number of surgeons, the distribution of cases, or whether the analytic method accounted for clustering or differences among surgeons. This matters because procedural outcomes may vary across operators, but the posted record does not allow that variation to be assessed.

Important trial-conduct and analysis details are not reported in the registry record. These include the randomization method, allocation concealment, analysis populations, missing-data handling, a full statistical analysis plan, multiplicity control, and the handling of possible departures from model assumptions. It is also unclear from the posted record whether all planned outcomes and analyses are represented. Such gaps limit independent assessment of risk of bias and robustness.

The safety reporting is brief. Detailed definitions and timing of serious events, arm-specific attribution for the listed event terms, and information on event ascertainment are not reported. The listed major-complication endpoint should not be assumed to capture every safety concern. The secondary comparison is also based on limited event information and has broad uncertainty.

Finally, the record concerns a specific surgical procedure and patient group. It does not report results for other operations or populations, nor does it provide measures of accuracy, learning curve, or long-term outcomes. These limits constrain what can be inferred from the statistical comparisons.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Evaluation of 3D Visualization for Total Colectomy — NCT02370056.
• Registry record last updated 2021-05-12; status last verified 2021-04.
• Results first posted 2020-12-17.
• 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

NCT02370056 was a completed randomized, parallel-group trial sponsored by The Cleveland Clinic. It compared 3D laparoscopic visualization with conventional 2D visualization during total laparoscopic abdominal colectomy for ulcerative colitis. The registry records 53 participants enrolled and lists no masking.

The primary outcome was mean total operating time in minutes, with a timeframe of 180 minutes. The observed group means were 75.3 minutes for 3D and 82.7 minutes for 2D. The mean difference comparing 2D with 3D was 7.4 minutes, with a 95% confidence interval from -11.44 to 26.24 and an unadjusted p-value of 0.442. Major complication was listed as a secondary outcome, with 8 participants counted in each group.

The estimates are uncertain and do not establish superiority, equivalence, or a difference in safety. The registry does not report several design and analysis details, including missing-data methods and the original sample-size justification.