Comparing Ways to Freeze the Nerve That Provides Thigh Sensation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparing Ways to Freeze the Nerve That Provides Thigh Sensation (NCT02577510), a randomized phase 3 study. The primary outcome is Anesthesia Related Time.

2. Clinical Question

The trial asks whether ultrasound guidance or nerve stimulation is a more efficient way to perform a lateral femoral cutaneous nerve block using local anesthetic. The primary outcome is anesthesia-related time, defined as the combined performance and onset times. The registry describes a randomized comparison, and the investigators’ stated hypothesis favored ultrasound guidance for efficacy and efficiency.

3. Trial Design

The registry records a randomized, single-masked, parallel-design, phase 3 trial, with status listed as completed. Enrollment is recorded as 21, and the registry lists the Canadian Forces Health Services Centre Ottawa as sponsor. The study concerns anesthesia of the lateral femoral cutaneous nerve in the context of meralgia paresthetica. Start and primary-completion dates are recorded, but those dates do not establish when results were analyzed or reported.

The design description needs to be read alongside the arm descriptions. They state that the right or left side was randomly assigned to nerve stimulation or ultrasound and that each patient received both approaches, one on each side. Thus the registry’s parallel-design label does not match the within-person arrangement described in the arm text. How the investigators accounted statistically for measurements from both sides of the same participant is not reported in the registry record. This matters because measurements from one person may be related rather than independent.

The primary outcome was anesthesia-related time, defined as performance time plus onset time, with a stated timeframe of less than 30 minutes. Secondary outcomes were success rate, needle passes, and pain with the procedure, also with a stated timeframe of less than 30 minutes. The registry lists 21 observations for each method in the posted outcome summaries; that should not be interpreted as separate groups of people, given the description that each patient received both methods.

Eligibility criteria, masking procedures, allocation concealment, details of the randomization sequence, and the analysis population are not reported in the registry record. The original sample-size justification and the trial’s planned statistical analysis are also not reported. These gaps limit how fully the study’s conduct and analysis can be evaluated from the registry information.

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: We enrolled 21 participants and randomized the sides for each modality.

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 Anesthesia Related Time, measured over less than 30 minutes.

The primary endpoint is anesthesia-related time, measured in seconds. The registry defines it as the sum of performance time and onset time. Performance time represents the time involved in carrying out the block, while onset time represents the time until the intended anesthetic effect is assessed. Combining the components gives a measure of the total time associated with anesthesia rather than focusing only on the injection procedure.

This endpoint is relevant to the investigators’ stated aim of comparing efficiency. If a method requires less total time, that would be reflected in a lower mean, but the endpoint alone does not describe every aspect of the procedure. It does not, by itself, establish success, pain, safety, or the quality of the resulting sensory block. Those topics are addressed separately by the posted secondary outcomes, and the record describes measurement of sensory distribution as part of the study background.

The registry reports the outcome as a mean with standard deviation. Nerve stimulation had a mean of 554.0 seconds and a standard deviation of 366.9; ultrasound had a mean of 480.0 seconds and a standard deviation of 251.9. The estimated mean difference, ultrasound relative to nerve stimulation, was -74.0 seconds. The interval around that estimate ranges from -264.3 to 116.3, so the observed data do not pin down the direction of the difference with precision.

The primary outcome’s stated timeframe is less than 30 minutes. More detail about how performance and onset were timed, how onset was defined, and whether measurement was blinded is not reported in the registry record.

7. Results Posted in the Registry

• Ultrasound: mean 480.00 versus 554.00 on control; difference -74.00 (95% CI -264.35 to 116.35), standardized effect d = -0.24; z-test p = 0.446.

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.

Success Rate

• 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:
  • Ultrasound: 95.2% (20/21) versus 76.2% (16/21) on control; risk difference 19.0 percentage points (95% CI -1.3 to 39.4), risk ratio 1.25 (0.97–1.62); unadjusted two-proportion z-test p = 0.078.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Ultrasound and the control. The interval gives the range of effects that remain compatible with the data.

Needle Pass

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Ultrasound: mean 3.20 versus 9.50 on control; difference -6.30 (95% CI -11.66 to -0.94), standardized effect d = -0.71; z-test p = 0.021.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Ultrasound than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Pain With Procedure

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Ultrasound Guided Xylocaine Injection: mean 4.60 versus 4.00 on control; difference 0.60 (95% CI -0.73 to 1.93), standardized effect d = 0.27; z-test p = 0.377.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Ultrasound Guided Xylocaine Injection and the control. The interval gives the range of effects that remain compatible with the data.

Across the secondary outcomes, the point estimates do not all move in the same direction. The success-rate estimate favors ultrasound, and the needle-pass estimate is lower for ultrasound; the pain estimate is slightly higher for ultrasound. The uncertainty differs across outcomes: the success and pain intervals include no difference, while the needle-pass interval does not. The posted unadjusted p-values likewise vary. These patterns provide descriptive context for the primary time comparison but do not turn the primary result into a definitive overall judgment about efficiency or performance.

Success rate and needle passes concern procedural performance, while pain with the procedure concerns the experience of the intervention. They measure different aspects of the comparison and should not be collapsed into one conclusion. Nor does an apparent pattern across outcomes establish a combined effect, since no overall composite or joint analysis is reported in the registry record.

Each secondary result is based on a limited set of posted observations, and the record does not give full analysis details. The registry does not report a multiplicity adjustment or explain how the outcomes were prioritized. In general, when multiple outcomes are tested, unadjusted results provide less confirmatory evidence because they do not account for the opportunity to observe a seemingly unusual result among several comparisons. A secondary result with an unadjusted p-value should therefore be read as exploratory or descriptive unless the analysis plan establishes otherwise.

The posted secondary findings neither negate nor independently confirm the primary endpoint. They broaden the picture by addressing success, technical attempts, and pain, but they do not remove the uncertainty around anesthesia-related time. The relevance of any single secondary pattern also depends on its measurement definition, the paired design, missing observations, and the planned analysis, details that are not fully reported in the registry record. Interpretation should rest on the effect estimates and their uncertainty rather than on a simple count of which results appear favorable.

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

• Success Rate
• Needle Pass
• Pain With Procedure

9. Statistical Interpretation

10. Statistical Methods Explained

Comparing two methods involves estimating how far apart their outcome distributions are, not simply comparing which observed mean is smaller. A mean difference expresses the contrast on the outcome’s original scale. Here, the contrast is ultrasound minus nerve stimulation, so a negative value indicates a lower observed mean time for ultrasound. The estimate is -74.0 seconds. Its uncertainty is important: the reported interval extends from -264.3 to 116.3 and includes no difference.

What does a confidence interval communicate?

In general, a confidence interval describes the range of values compatible with the data and the statistical procedure used to construct it. Narrower intervals indicate greater precision; wider intervals indicate less precision. An interval that includes zero for a mean difference does not establish that the methods are the same. It indicates that the data do not rule out zero difference at the interval’s stated level. The confidence level for the posted comparison interval is not reported in the registry record, so it should not be assumed from the interval alone.

What does a p-value add?

In general, a p-value describes how unusual data at least as incompatible with a specified null hypothesis would be if that hypothesis and the test assumptions held. It is not the probability that the null hypothesis is true, and it does not measure the size or practical importance of an effect. The recalculated primary p-value is 0.446. The registry separately reports p=0.05 from a one-sided t-test. Because the test direction and analysis differ, the values should not be treated as interchangeable. The trial’s complete prespecified analysis plan is not reported in the registry record.

Why does the design description matter?

General statistical reasoning distinguishes a comparison of independent groups from a paired comparison. When both methods are measured within the same person, the two measurements may be correlated. A paired analysis uses information about the within-person differences and their variability. An independent-groups calculation instead uses group-level summaries and does not account for the pairing. The registry says each patient received both methods on opposite sides, but it labels the design parallel. The correlation or paired-difference summaries needed to evaluate the paired analysis are not reported in the registry record. The recalculated estimates should therefore be read as unadjusted calculations from posted summaries, not as a substitute for the investigators’ complete analysis.

Why can over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a statistical model expects. When variability is high relative to the effect being estimated, uncertainty increases and estimates become less precise. For a continuous outcome, standard deviations give information about spread, though they do not reveal the full distribution. The primary outcome’s standard deviations are 366.9 seconds and 251.9 seconds, compared with an estimated mean difference of -74.0 seconds. These summaries indicate that the means need to be interpreted alongside substantial observed variation. Whether the time data were skewed, whether outliers occurred, or whether a transformation or robust method was considered is not reported in the registry record.

What are the recalculated results?

Recalculated results are unadjusted comparisons derived from the posted group summaries. They can help readers understand the contrast and its uncertainty, but they are not necessarily identical to the sponsor’s analysis. They may not reflect paired measurements, covariate adjustment, missing-data procedures, or other features that were part of the original analysis. The registry lists one sponsor analysis for the primary outcome, but gives no estimate or interval for that analysis. The sponsor-reported test is a one-sided t-test with p=0.05. The trial’s full analytic methods and any adjustment strategy are not reported in the registry record.

How should secondary outcomes be treated?

General statistical practice treats multiple outcomes with care. Testing several outcomes creates more opportunities for apparently notable results, even when no underlying effects exist. An unadjusted p-value does not account for the number of outcomes or comparisons examined. The registry posts three secondary outcomes, but does not report a multiplicity adjustment or explain which outcomes were prespecified as key secondary analyses. Their results can be useful for describing the study, but isolated unadjusted findings carry less confirmatory weight than a result supported by a prespecified analysis plan and appropriate control of multiplicity.

These methods explanations are general statistical guidance. They do not establish which procedures the investigators actually used beyond the sponsor’s recorded one-sided t-test. The registry’s original sample-size justification, detailed analysis population, missing-data approach, and handling of the within-person design are not reported in the registry record.

11. Confidence Intervals and Precision

The primary estimate is a mean difference of -74.0 seconds for ultrasound relative to nerve stimulation. Its reported interval runs from -264.3 to 116.3. Because zero lies within that range, the result is compatible with no mean difference as well as with differences favoring either method. The interval is broad relative to the point estimate, so the magnitude and direction are not determined precisely by these data.

In general, an interval is more informative than a point estimate alone because it displays uncertainty around the estimated effect. An interval spanning zero is not proof of equivalence, and it does not show that the methods have identical performance. Establishing equivalence or non-inferiority would require a prespecified margin and a design and analysis intended to test that question. Such a margin and such an analysis are not reported in the registry record.

The posted standard deviations for anesthesia-related time are 366.9 seconds for nerve stimulation and 251.9 seconds for ultrasound. These indicate substantial spread around each mean. A mean can summarize a distribution while hiding skew, outliers, or clusters; distributional details are not reported in the registry record. The posted summaries also do not show how paired times within each participant varied together. Since the arm descriptions say both methods were used within each participant, that missing paired information limits assessment of the precision of a within-person contrast.

The registry does not state the confidence level attached to the recalculated interval. It is therefore appropriate to refer to it as the reported interval without assigning a confidence percentage not specified in the record. The reported sponsor test gives p=0.05, while the unadjusted recalculation gives p=0.446. Those figures arise from separately described analyses and do not resolve the uncertainty conveyed by the broad primary interval.

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 effect, not the trial’s original design justification. The assumptions stated for these illustrations 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 trial’s original sample-size assumptions are not reported in the registry record.

For these non-time-to-event outcomes, the planning figures are participants per arm, not a combined total. The 80% power column gives the illustrative number of participants per arm under the stated assumptions for an 80% chance of detecting the chosen effect if that effect were the true effect. The 90% power column gives the corresponding number for a 90% chance. These are design calculations for hypothetical future studies; they are not a statement about the probability that the current trial detected an effect.

Rows based on 100%, 75%, and 50% of the observed effect represent different assumed effect sizes. Smaller effects need more participants to detect under the same assumptions, which is why the planning figures increase as the assumed fraction decreases. The observed effect is an uncertain estimate from this study, so using it as the basis for planning is illustrative rather than a guarantee that a future study will see the same effect.

This is not observed power. Observed power is not a useful replacement for examining the estimate and its uncertainty after results are known. The planning calculations are best read as sensitivity illustrations showing how required sample size changes when the target effect or desired power changes. They do not confirm that the original study was adequately powered, and they do not reveal the investigators’ original planning rationale.

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 = -74.000; pooled standard deviation σ = 314.698.
2. n = 2 × (1.96 + 0.842)² × 314.698² / -74.000² = 283.9, rounded up to 284 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 <- -74                      # observed difference in means
sigma <- 314.697648545393                     # 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(2577510)
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 = 284 (80% power), 381 (90% power)
 75% of observed effect: n per arm = 505 (80% power), 676 (90% power)
 50% of observed effect: n per arm = 1,136 (80% power), 1,521 (90% power)
power.t.test: 284.9 
Simulated power at n = 284 per arm: 0.797 (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. Analyses Reported by the Sponsor

The registry’s reported primary analysis is a one-sided t-test with p=0.05. It does not provide an associated effect estimate, interval, test statistic, or details of the direction specified for that test. The unadjusted recalculation from the posted summary statistics gives a mean difference of -74.0 seconds, an interval from -264.3 to 116.3, and p=0.446. These recalculated quantities describe the observed contrast and its uncertainty using posted summaries; they are not a transcription of the sponsor’s analysis.

The record does not flag a discrepancy between the posted results and recalculation. The sponsor’s own analysis therefore does not need to be displaced on the basis of a flagged numerical conflict. Still, the two p-values should not be compared as if they came from the same test: the registry identifies the sponsor test as one-sided, while the recalculation is an unadjusted summary-statistic comparison. The registry’s complete statistical plan and the basis for the one-sided test are not reported in the registry record.

The registry also describes the methods as used on opposite sides within each patient, while its design field says parallel. Without the paired analysis details, it is not possible to determine whether the sponsor’s test accounted for within-person dependence. The recalculation should be treated as a separate, limited perspective on the posted summaries, not as a correction to the sponsor’s work.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome and three secondary outcomes. Testing multiple outcomes can increase the chance of a nominally notable result even when all underlying effects are absent. In general, multiplicity can be addressed by prespecifying a hierarchy, adjusting significance thresholds, or using another planned strategy. The registry does not report whether such a strategy was used, whether any secondary outcomes were designated as key, or how the investigators intended to interpret multiple tests.

Missing-data procedures and analysis populations are also not reported in the registry record. The posted outcome summaries list 21 observations for each method, but do not explain whether all randomized participants contributed data to every endpoint, whether observations were excluded, or how any missing values were handled. No assumptions or sensitivity analyses for missing data are reported. These details matter because missing outcomes can affect both the estimated effect and its uncertainty, particularly if the reasons for missingness differ across methods.

The registry’s arm descriptions say each patient received both methods on opposite sides, while the design field identifies a parallel model. If the observations are paired, a suitable analysis would ordinarily account for within-person dependence. The record does not report the paired differences, their variability, or the method used to model the two measurements. Consequently, the available summaries do not allow a full appraisal of whether the analysis reflected the described allocation and treatment structure.

Other relevant details not reported in the registry record include the original statistical analysis plan, the sample-size justification, any interim analyses, covariate adjustment, handling of protocol deviations, and whether outcome definitions or analyses changed. These omissions do not establish that a particular procedure was or was not performed. They mean that readers cannot verify those aspects of the study’s analysis from the registry record alone.

16. 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 1% reporting threshold.

Most frequent non-serious adverse event terms

The posted adverse-event summaries show zero serious adverse events in both method groups and zero deaths in both groups. For other adverse events, the record lists one affected participant in the ultrasound-guided group and none in the nerve-stimulation-guided group. These are descriptive counts from the registry, not a complete safety comparison.

Zero reported serious events does not prove that serious harms are impossible or that the methods have identical safety. The study’s posted groups are small, and uncommon events may not appear in a study of this size. The registry does not provide serious-event terms, and the adverse-event summary does not explain the nature, timing, severity, or relatedness of the one other event. Follow-up duration and the methods used to collect adverse events are not reported in the registry record.

The safety counts should be interpreted as the events recorded for this trial, not as estimates that can be generalized to all patients or settings. They do not change the uncertainty in the primary time comparison and should not be taken as a comprehensive assessment of safety.

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

The results describe a randomized comparison of two approaches to lateral femoral cutaneous nerve block. The posted mean anesthesia-related time was lower with ultrasound, and the unadjusted difference estimate was -74.0 seconds. However, the interval from -264.3 to 116.3 includes zero and extends in both directions. The data therefore do not precisely establish whether ultrasound or nerve stimulation has the lower mean time.

The results do not establish that the methods are equivalent. Equivalence is a specific statistical conclusion that requires a prespecified acceptable difference and an analysis designed to test it; such information is not reported in the registry record. A non-small recalculated p-value is not evidence that the true difference is zero. Conversely, the sponsor’s one-sided test, reported as p=0.05, should not be taken by itself as proof of a meaningful advantage because the record does not provide its estimate, interval, full analysis plan, or rationale for the test direction.

Efficiency is only one dimension of a nerve block. The study also posted success, needle-pass, and procedure-pain outcomes, but those results do not create a single overall measure of benefit. Their unadjusted nature and the absence of a reported multiplicity strategy limit confirmatory interpretation. The adverse-event counts are similarly descriptive and do not provide a comprehensive safety comparison.

The registry describes both methods as being given to each participant on opposite sides, yet labels the design parallel. Without a reported paired analysis, the summary-statistic recalculation may not capture the within-person structure. Eligibility criteria, participant characteristics, missing-data methods, and the original analysis plan are also not reported. These limitations mean that the findings should be understood as the posted results from this trial, not as a definitive estimate applicable to every patient or clinical setting.

18. Why This Trial Matters Statistically

This trial illustrates why a treatment comparison should be read through its estimate and uncertainty, not through the direction of the point estimate alone. Ultrasound has the lower posted mean time, but the interval around the difference includes zero and allows effects in either direction. The numerical contrast is visible; its precision is limited. That distinction is central to sound interpretation of clinical research.

It also highlights the importance of matching an analysis to a study’s design. The record describes random assignment of methods to opposite sides within each patient, while the design label says parallel. When measurements are paired, accounting for their dependence can affect estimated uncertainty. Arm-level means and standard deviations do not reveal the within-person relationship, so complete reporting of the design and analysis is essential for independent appraisal.

The trial’s multiple outcomes show why secondary results need context. Different outcomes capture different aspects of a procedure, and unadjusted testing across them can make isolated findings less persuasive. Prespecified outcome priorities and a transparent multiplicity strategy help readers distinguish confirmatory evidence from exploratory patterns. The registry record does not report those details.

Finally, planning illustrations based on an observed effect can help readers understand how study size depends on the effect a future study aims to detect. They cannot recover the original sample-size rationale or describe the probability that this completed study detected an effect. This distinction prevents planning calculations from being mistaken for evidence about the trial’s observed statistical power.

19. 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 trial. The most consequential design-reporting issue is that the registry labels the study parallel while the arm descriptions say each patient received both methods on opposite sides. The paired outcome data and the analysis used to account for this arrangement are not reported. The posted group summaries therefore do not show how within-person differences were distributed or correlated.

The primary endpoint combines performance and onset time, but the registry does not give detailed operational definitions for either component, describe the timing procedures, or report assessor masking. It also does not report the confidence level for the recalculated interval. These omissions make it harder to assess measurement consistency and reproduce the analysis.

The registry lists enrollment as 21 and outcome summaries with 21 observations for each method, but does not describe participant characteristics, eligibility criteria, exclusions, missing observations, or the analysis population. It is therefore not possible to assess how representative the participants were or whether every enrolled participant contributed to all results. The original sample-size assumptions, statistical analysis plan, and any interim analyses are not reported in the registry record.

Only one sponsor analysis is recorded for the primary endpoint, and it is identified as a one-sided t-test with p=0.05. Its estimated effect, interval, and analytic rationale are not given. The secondary outcomes have no sponsor analyses listed, and a multiplicity approach is not reported. Safety information is limited to aggregate adverse-event counts; event descriptions and follow-up details are not reported. Together, these reporting gaps constrain independent verification and interpretation, without demonstrating that any particular procedure was omitted.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Comparing Ways to Freeze the Nerve That Provides Thigh Sensation — NCT02577510.
• Registry record last updated 2017-09-15; status last verified 2017-09.
• Results first posted 2017-09-15.
• 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.

23. Record Summary

The registry record describes a completed randomized comparison of ultrasound-guided and nerve-stimulation-guided lateral femoral cutaneous nerve block. Its primary endpoint is anesthesia-related time, defined as performance time plus onset time. The posted mean was 554.0 seconds with nerve stimulation and 480.0 seconds with ultrasound; the unadjusted mean difference was -74.0 seconds, with an interval from -264.3 to 116.3.

The registry reports a one-sided sponsor t-test with p=0.05. An unadjusted recalculation from the posted summaries gives p=0.446. The record describes each participant receiving both methods on opposite sides but labels the design parallel, and does not report the paired-analysis details needed to resolve that issue. Secondary outcomes and adverse-event counts add descriptive context, while multiplicity, missing-data procedures, and the original sample-size justification are not reported in the registry record. The primary comparison remains uncertain in direction and magnitude.