A Comparison of Stryker Hybrid Arch Bars: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Comparison of Stryker Hybrid Arch Bars (NCT02283528), a randomized na study. The primary outcome is Time to Place Archbars.

2. Clinical Question

The comparison is about a procedural measure: time to place arch bars, recorded in minutes. The study summary explains that arch bars are used to hold the upper and lower teeth together while a mandibular fracture heals or while plates and screws are applied. It describes the Hybrid device as fixed to the jaw bone and the Erich device as wired to the teeth. The study's stated purpose was to compare the speed of placement and fracture healing. The posted primary result compares group means, while the secondary results concern a count of participants with fracture healing and a count with specified complications. Those outcomes address different questions: a difference in average placement time does not by itself establish a difference in healing or complications. Participant characteristics, the fracture mix, and further details of eligibility are not reported in the registry record, so the extent to which the enrolled participants represent other clinical settings cannot be assessed from this record alone.

3. Trial Design

The registry identifies NCT02283528 as a completed, randomized, parallel-group study titled “A Comparison of Stryker Hybrid Arch Bars.” Its official title describes a prospective randomized study of Stryker Hybrid versus Erich arch bars for maxillomandibular fixation of mandibular fractures. The listed enrollment is 50. The start is recorded as 2015-05, and primary completion as 2017-12-21. Emory University is listed as the sponsor.

The two device groups are Hybrid and Erich. The posted primary endpoint data include 26 participants in the Hybrid group and 24 in the Erich group. The registry describes placement of either type for open or closed reduction of mandible fractures. The trial is listed as having no masking, so the record does not describe it as blinded. The allocation method is recorded as randomized, but the method used to generate or conceal the allocation sequence is not reported in the registry record.

The primary outcome is time to place arch bars, measured in minutes during the initial admission and surgery. Secondary outcomes are the number of participants with fracture healing at 6 weeks and the number with complications, including loosening of archbars, loosening of maxillomandibular fixation, or damage to adjacent teeth and structures, up to 6 weeks post operatively. No phase is applicable according to the registry listing.

The registry record does not report the study setting, baseline characteristics, detailed inclusion or exclusion criteria, planned follow-up procedures, or a full protocol. It also does not report the trial's original sample-size justification, prespecified statistical methods, or analysis populations. The completed status and posted outcomes describe the record's status and results, but do not supply those missing design details.

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 Time to Place Archbars, measured over During initial admission and surgery.

The primary endpoint is time to place arch bars, measured in minutes during the initial admission and surgery. It is a continuous measure: each observation represents elapsed time, and the posted group summaries describe the mean and standard deviation. The mean gives the average placement time in a group; the standard deviation describes how spread out individual times are around that group mean.

This endpoint addresses the procedural-speed question stated in the study summary. The registry describes arch bars as a means of holding the teeth together during fracture treatment, with the two devices differing in how they are attached. Comparing placement time can describe whether the observed procedures took different average amounts of time in the randomized groups. It does not, by itself, measure fracture healing, complications, patient experience, or the overall consequences of choosing either device.

The Hybrid group had a posted mean placement time of 14.07 minutes, with a standard deviation of 8.4. The Erich group had a mean of 37.29 minutes, with a standard deviation of 15.1. The posted mean difference, expressed as Erich minus Hybrid, is 23.22 minutes. The registry's stated timeframe is during the initial admission and surgery. Details such as who timed the procedure, how start and stop times were defined, and whether timing was assessed by someone unaware of group assignment are not reported in the registry record. Those details matter when interpreting a time-based measure, particularly in an unmasked study.

7. Results Posted in the Registry

• Erich: mean 37.29 versus 14.07 on control; difference 23.22 (95% CI 16.37 to 30.07), standardized effect d = 1.92; z-test p = <0.001.

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.

Number of Participants With Fracture Healing at 6 Weeks

• 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:
  • Erich: 75.0% (18/24) versus 69.2% (18/26) on control; risk difference 5.8 percentage points (95% CI -19.0 to 30.6), risk ratio 1.08 (0.77–1.53); unadjusted two-proportion z-test p = 0.650.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Erich and the control. The interval gives the range of effects that remain compatible with the data.

Number of Participants With Complications Including Loosening of Archbars, Loosening of MMF, or Damage to Adjacent Teeth and Structures

• 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:
  • Erich: 0.0% (0/24) versus 19.2% (5/26) on control; risk difference -19.2 percentage points (95% CI -34.4 to -4.1); unadjusted two-proportion z-test p = 0.024.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically lower for Erich than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcomes address healing and complications, rather than the time required to place arch bars. The posted fracture-healing counts are similar in the two groups, while the complications counts differ. These outcomes do not measure the primary procedural-time question, and the primary result cannot determine what happened for healing or complications. Each endpoint provides a separate, limited view of the comparison.

The fracture-healing result is imprecise: the posted risk-difference confidence interval includes both negative and positive values, and the unadjusted p-value is 0.65. The complication result has an unadjusted p-value of 0.024, with 5 events recorded in one group and none in the other. That event pattern warrants careful reading rather than a simple conclusion about comparative safety. The registry does not report the event adjudication process, missing outcome data, or a detailed analysis method for these endpoints.

Unadjusted secondary results generally carry less weight than a prespecified primary comparison when the record does not explain the testing hierarchy or any multiplicity adjustment. When multiple outcomes are tested, a nominal p-value does not account for the number of opportunities to find a difference. The registry record lists no reported analyses for the secondary outcomes and does not indicate whether these comparisons were planned as confirmatory. This does not make the results irrelevant; it means they should be treated as descriptive or exploratory evidence unless further analysis details are available.

The secondary outcomes also differ in how they are represented. Healing is recorded as a participant count at 6 weeks, while complications include specified events up to 6 weeks post operatively. They are not interchangeable measures, and neither provides a complete account of all possible benefits or harms. Taken together, the posted results suggest that procedural time and the secondary outcomes tell different parts of the study story, with the latter less secure as evidence for a definitive between-group effect.

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

• Number of Participants With Fracture Healing at 6 Weeks
• Number of Participants With Complications Including Loosening of Archbars, Loosening of MMF, or Damage to Adjacent Teeth and Structures

9. Statistical Interpretation

10. Statistical Methods Explained

The posted primary outcome is continuous and is summarized by a mean and standard deviation in each group. A mean is the arithmetic average of the measured placement times. A standard deviation describes variability among times; it is not the uncertainty in the mean itself. The Hybrid mean is 14.07 minutes with a standard deviation of 8.4, and the Erich mean is 37.29 minutes with a standard deviation of 15.1. The group sizes reported for this endpoint are 26 and 24, respectively.

What does the mean difference represent?

The reported mean difference is Erich minus Hybrid. Its estimate of 23.22 minutes expresses the difference between the two posted group means in that direction. A positive value therefore corresponds to a longer mean placement time in the Erich group in these data. This is an unadjusted group comparison: the registry record does not report a model adjusting for participant or procedure characteristics. A difference in group means does not describe every participant's procedure time, and the mean difference should not be interpreted as a guaranteed time saving for an individual procedure.

How should the p-value be understood?

The primary unadjusted p-value is <0.001. In general, a p-value describes how unusual data at least as discrepant as those observed would be under a specified null model and its assumptions. It does not state the probability that the null model is true, measure the size or importance of the difference, or establish that the result will recur in another study. The registry record does not specify the exact test used for the primary comparison, whether assumptions were checked, or whether any adjustment was applied. The reported p-value should therefore be read as the posted unadjusted result, not as evidence of a complete analysis plan.

What does a confidence interval add?

The primary 95% confidence interval runs from 16.37 to 30.07 minutes for the mean difference. In general, a confidence interval gives a range of values compatible with the data under the statistical method used. It communicates uncertainty about the estimated difference as well as its direction. It is not a range containing every individual participant's time, and it does not guarantee that the true difference lies inside this particular interval. The method used to construct the interval is not reported in the registry record.

How do the secondary outcomes differ?

The secondary outcomes are counts of participants, rather than continuous measurements. For fracture healing, the registry posts 18 of 26 in the Hybrid group and 18 of 24 in the Erich group, with an unadjusted p-value of 0.65. A risk difference compares the observed event proportions between groups; a confidence interval for a risk difference conveys uncertainty about that comparison. For complications, the posted counts are 5 of 26 and 0 of 24, with an unadjusted p-value of 0.024. When one group has no recorded events, estimates of relative measures can be particularly sensitive to the statistical method. The record does not report the analysis method for these endpoints, and the registry lists no reported analyses.

General statistical context: multiple outcome comparisons increase the opportunity to observe a nominally small p-value by chance, especially when no adjustment or prespecified testing order is described. That concern does not erase the posted findings, but it affects how much weight to give unadjusted secondary results. The primary endpoint is identified separately in the record, while the record does not say whether the secondary outcomes were confirmatory or exploratory.

Why can over-dispersion matter?

General explanation: over-dispersion occurs when observed variability is greater than a statistical model assumes. If a model understates variability, its standard errors may be too small and its confidence intervals too narrow. The registry reports standard deviations for placement time, but does not report an over-dispersion assessment or enough detail to determine whether a particular model was used. It would therefore be inappropriate to claim that over-dispersion was present or that it was addressed in the trial analysis.

What analysis details remain unknown?

The registry record does not report the test used for the primary endpoint, the methods used for the confidence intervals, covariate adjustment, missing-data methods, the treatment of protocol deviations, or the analysis population. It also does not report interim analyses, subgroup analyses, or multiplicity procedures. These omissions limit independent assessment of the analytical choices. The posted summary statistics remain useful descriptions of the recorded results, but they cannot answer every question about how the trial data were analyzed.

11. Confidence Intervals and Precision

The primary estimate is a mean difference of 23.22 minutes, with a 95% confidence interval from 16.37 to 30.07 minutes. Because the interval lies above zero, the posted estimate is consistent with a higher average placement time in the Erich group than in the Hybrid group, given the stated direction of subtraction. The interval also shows that the estimate is not a single exact value: a range of differences remains compatible with the data under the method used to calculate it.

General explanation: a confidence interval describes statistical uncertainty around an estimate, conditional on the data and the method's assumptions. It is not a prediction interval for individual procedure times and does not mean that a specified share of future study results will fall inside it. It also does not incorporate every possible source of uncertainty, such as differences in case mix, operator experience, measurement practices, or study setting. The construction method for the posted interval is not reported in the registry record.

The standard deviations of 8.4 minutes for Hybrid and 15.1 minutes for Erich describe variation in recorded placement times within the groups. They should not be confused with the confidence interval for the between-group mean difference. The primary interval communicates the precision of that comparison; the standard deviations describe dispersion among observations.

The secondary fracture-healing comparison is less conclusive about the direction and size of a difference: its posted risk-difference interval extends from -0.190 to 0.306. That interval includes values on either side of zero. The complications comparison is based on 5 recorded participants in the Hybrid group and 0 in the Erich group, and the available registry record does not give a confidence interval for that outcome. These secondary results therefore have different precision and should not be read as having the same evidential strength as the primary estimate. The limited number of recorded events also makes the complications contrast sensitive to how events were defined and analyzed.

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 illustrations based on the observed effects, not the trial's original design assumptions. For these outcomes, the figures refer to participants per arm; no time-to-event outcome is posted. The listed 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 to the stated fraction of the observed effect. The trial's own original sample-size justification and design assumptions are not reported in the registry record.

For each effect scenario, the 80% power column indicates the number of participants per arm in a hypothetical study that would have an 80% chance of detecting that assumed effect under the stated planning assumptions, if the assumptions hold. The 90% power column gives the corresponding planning figure for a higher chance of detection. These are prospective planning calculations, not estimates of the probability that this completed trial detected a true effect. This is not observed power.

For the primary placement-time outcome, planning for 100% of the observed effect gives 5 participants per arm for 80% power and 6 per arm for 90% power. Planning for 75% of the observed effect gives 8 per arm and 11 per arm; planning for 50% gives 18 per arm and 23 per arm. For fracture healing, the analogous figures are much larger: for 100% of the observed effect, 948 participants per arm for 80% power and 1,268 per arm for 90% power; for 75%, 1,712 and 2,291; for 50%, 3,909 and 5,233. No planning figures are posted for the complications outcome.

The general pattern is that smaller effects require more participants to detect under otherwise unchanged assumptions. The planning figures depend on the observed effect, which is itself uncertain, and should not be treated as a recommendation or as evidence that the trial was designed to achieve a particular power. They also do not account for any assumptions not listed in the registry record.

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 = 23.220; pooled standard deviation σ = 12.083.
2. n = 2 × (1.96 + 0.842)² × 12.083² / 23.220² = 4.3, rounded up to 5 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 <- 23.22                      # observed difference in means
sigma <- 12.0832442525452                     # 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(2283528)
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 = 5 (80% power), 6 (90% power)
 75% of observed effect: n per arm = 8 (80% power), 11 (90% power)
 50% of observed effect: n per arm = 18 (80% power), 23 (90% power)
power.t.test: 5.4 
Simulated power at n = 5 per arm: 0.760 (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

The registry identifies one primary endpoint and lists two secondary outcomes. It does not report whether the secondary tests were arranged in a prespecified hierarchy, whether an adjustment for multiple comparisons was planned, or whether any outcomes were designated exploratory. The posted p-values for the secondary outcomes are unadjusted. When several outcomes are examined, the chance of at least one small p-value can increase; an adjustment or a prespecified testing strategy can address that issue, but neither is described in the registry record. Consequently, the secondary p-values should not be interpreted as if they necessarily reflect a multiplicity-controlled analysis.

Missing-data handling is also not reported in the registry record. The endpoint summaries give group counts, but those counts alone do not establish whether all randomized participants contributed data, whether any data were missing, or how missing outcomes were treated. The record does not describe participant flow, withdrawals, exclusions from analyses, or reasons for any unavailable measurements. Without that information, it is not possible to assess whether missingness could have affected the posted estimates.

The analysis population is not reported in the registry record. The record does not say whether the primary result follows an intention-to-treat approach, a per-protocol approach, or another population definition. It also does not describe handling of crossovers, protocol deviations, or participants whose procedure differed from the assigned device. No interim analyses, subgroup analyses, or covariate-adjusted models are listed.

These omissions are limits on interpretation, not evidence that particular analyses or data problems occurred. The randomized allocation is recorded, but the allocation sequence method and concealment procedures are not described. The masking field is none. Together, these details mean the available record supports reading the posted estimates as group summaries, while leaving important questions about analysis specification, missingness, and robustness unanswered.

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.

The registry's adverse-event figures list 0 serious adverse events in the Hybrid group and 0 in the Erich group. It also lists 0 other adverse events and 0 deaths in each group. The groups are shown with 26 and 24 participants at risk, respectively. These are registry-recorded counts, not proof that no adverse events occurred outside the definitions, reporting procedures, or observation captured by the record.

The secondary complications outcome is distinct from these adverse-event fields. It includes loosening of archbars, loosening of maxillomandibular fixation, or damage to adjacent teeth and structures up to 6 weeks post operatively; the posted counts are 5 in the Hybrid group and 0 in the Erich group. The record does not explain whether or how those complications overlap with the adverse-event categories. They should not be combined or treated as equivalent measures.

Interpretation of safety counts depends on follow-up completeness, event definitions, and ascertainment. The registry does not report detailed surveillance methods, severity grading, or adjudication procedures. A zero count in a group means no events were recorded for that category in the posted result; it does not establish that the underlying risk is zero. The available figures therefore describe what the registry records, with limited information about how events were collected.

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

The clearest statistical finding is a difference in the posted group means for the primary procedural endpoint. Mean placement time was 14.07 minutes in the Hybrid group and 37.29 minutes in the Erich group; the reported Erich-minus-Hybrid mean difference is 23.22 minutes, with a 95% confidence interval from 16.37 to 30.07 minutes and an unadjusted p-value of <0.001. This describes the trial's observed average times. It does not mean every procedure took longer in one group or predict the timing of an individual procedure.

The primary endpoint is limited to time to place arch bars during the initial admission and surgery. It does not establish a difference in fracture healing, complications, patient experience, or other outcomes. The healing comparison has an unadjusted p-value of 0.65 and an interval that includes values in both directions. The complications result records events in one group and none in the other, but is a secondary comparison with limited event information. Neither secondary result should be treated as a definitive account of overall effectiveness or safety.

Randomization is an important design feature for comparing groups, but the registry does not report allocation concealment, detailed participant characteristics, missing-data handling, or analysis populations. The study is listed as unmasked, and the record does not describe how procedural time or outcomes were measured and assessed. These uncertainties restrict what can be concluded about the stability and applicability of the estimates.

The results therefore support a specific statistical description: the posted average placement times differed, while the secondary findings are less conclusive and require caution. They do not establish that either device is preferable in every setting, nor do they answer questions not measured by the posted outcomes. No treatment recommendation follows from these data alone.

17. Why This Trial Matters Statistically

This trial is statistically useful because it places a procedural measure and clinical follow-up outcomes in the same randomized comparison. The primary endpoint, time to place arch bars, is continuous and summarized by group means, standard deviations, a mean difference, and a confidence interval. The secondary outcomes are participant counts. Understanding that these are different kinds of endpoints helps prevent a clear result on procedural time from being mistaken for equally clear evidence about healing or complications.

The record also illustrates why effect estimates and uncertainty should be read together. The primary estimate is accompanied by a confidence interval, while the secondary outcomes have different amounts and types of information. The healing interval spans effects in either direction, and the complications result involves a small number of recorded events. A p-value alone cannot convey these distinctions or establish clinical importance.

The sample-size planning illustrations make another statistical point: planning requirements depend strongly on the size of the effect one aims to detect. The figures for the continuous primary endpoint differ substantially from those for fracture healing, and smaller assumed effects require more participants under the listed assumptions. These calculations are not the original design justification and do not indicate the trial's observed power.

Finally, the record's missing analysis details matter. Randomization and a named primary endpoint provide a useful framework, but the absence of reported information on multiplicity, missing data, analysis populations, and measurement methods limits assessment of robustness. The trial is a reminder that a numerical result is best interpreted alongside the endpoint definition, design, precision, and reporting context.

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.

Several limitations are specific to the information recorded for this comparison. The posted endpoint groups contain 26 participants in the Hybrid group and 24 in the Erich group, and the registry does not provide baseline characteristics. Fracture features, participant demographics, operator experience, and procedural context are not reported, so it is not possible to assess how balanced or representative the groups were on those factors from the record.

The study is listed as unmasked. The registry does not explain who recorded placement time, how timing was defined, or whether outcome assessment was standardized. Since the primary endpoint is a timed procedure, measurement practices could affect recorded times. The record also does not describe allocation concealment or the method used to generate the randomized sequence.

Outcome details are limited. The registry does not report how fracture healing was defined or assessed, how complications were identified, or whether events were independently adjudicated. Follow-up completeness and missing-data handling are not reported. For the secondary complications result, a count of 0 in one group should be read as no recorded events in that group, not as proof of no possible risk.

The registry does not report the trial's original sample-size justification, a complete statistical analysis plan, multiplicity procedures, or analysis populations. It also does not list reported analyses for the secondary outcomes. These gaps prevent a full appraisal of whether the analyses followed prespecified methods or how sensitive results might be to alternative choices. The posted primary estimate is informative about the recorded comparison, but the scope and reliability of conclusions beyond that estimate remain constrained by the available reporting.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: A Comparison of Stryker Hybrid Arch Bars — NCT02283528.
• Registry record last updated 2019-01-14; status last verified 2019-01.
• Results first posted 2019-01-14.
• 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

NCT02283528 is a completed, randomized, parallel-group comparison of Stryker Hybrid and Erich arch bars for mandibular fractures. The registry lists enrollment of 50, no masking, and Emory University as sponsor. The primary endpoint is time to place arch bars during the initial admission and surgery. The posted mean was 14.07 minutes for Hybrid and 37.29 minutes for Erich, with an Erich-minus-Hybrid mean difference of 23.22 minutes and a 95% confidence interval from 16.37 to 30.07 minutes.

The registry also posts fracture-healing and complications outcomes, along with adverse-event counts. The record does not report a detailed statistical analysis plan, original sample-size justification, missing-data methods, or analysis populations. Secondary results are unadjusted and should be interpreted cautiously.