Ultrasound Guided Adductor Canal Versus Femoral Nerve Blocks for Anterior Cruciate Ligament Reconstruction in Pediatrics: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Ultrasound Guided Adductor Canal Versus Femoral Nerve Blocks for Anterior Cruciate Ligament Reconstruction in Pediatrics (NCT03053401), a randomized na study. The primary outcome is Quadriceps Muscle Strength in Kilogram-force (Kgf).

2. Clinical Question

3. Trial Design

The registry record identifies this as a randomized, triple-masked, parallel-group trial. The two arms were Adductor Canal Block and Femoral Nerve Block, with 26 participants listed in each arm. Enrollment was 52. The phase is recorded as not applicable. The study status is completed, and the sponsor is Akron Children's Hospital.

The registered intervention comparison concerned ultrasound-guided single-shot blocks for postoperative analgesia after arthroscopic ACL reconstruction in pediatric patients. The arm descriptions identify ultrasound guidance for both procedures. The adductor canal description specifies a mid-thigh block intended to target the saphenous nerve. Both descriptions mention a needle, while the solution details are incomplete in the posted record. The full procedural protocol and complete drug recipe are not reported in the registry record.

The primary outcome was quadriceps muscle strength on the surgical side, measured 4 hours following peripheral nerve block performance. The record describes a supine assessment with a cushion under the knee and dynamometer readings taken at the ankle; participants were instructed to extend their legs three times, with a 30-second pause between attempts. The outcome is recorded in kilogram-force. Group results are reported as medians and full ranges.

The start date was 2017-02-09, and the primary completion date was 2019-10-25. Although the registry classifies the study as completed, details about the recruitment process, masking procedures, allocation concealment, follow-up beyond the primary time point, and protocol deviations are not reported in the registry record. The record does not describe a sample-size justification or provide a full statistical analysis plan.

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

Analysis population for the primary outcome, as defined in the registry: 20 of 26 subjects in the femoral nerve block group had recorded quadriceps muscle strength of zero.

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 Quadriceps Muscle Strength in Kilogram-force (Kgf), measured over 4 hours following peripheral nerve block performance.

The primary endpoint is quadriceps muscle strength on the surgical side, expressed in kilogram-force (Kgf), measured 4 hours following peripheral nerve block performance. A dynamometer was placed on the front of the ankle while the participant was supine, with the knee supported at a 45-degree angle. Participants were asked to extend the leg three times, pausing for 30 seconds between attempts. The record states that all three readings for each leg were recorded.

This endpoint addresses a specific functional concern raised in the registry rationale: postoperative quadriceps weakness. The rationale notes that the investigators were interested in whether the adductor canal block could provide analgesia while having a different relationship with muscle strength than the femoral nerve block. Strength is therefore a functional measure relevant to the stated comparison, rather than a direct pain score or an assessment of the duration or quality of analgesia.

The posted primary outcome is summarized by the median and full range for each arm. The registry reports the Adductor Canal Block median as 1.1 Kgf, with a full range from 0.0 to 25.6; the Femoral Nerve Block median is 0.0 Kgf, with a full range from 0.0 to 15.3. The record also states that 20 of 26 subjects in the femoral nerve block group had recorded strength of zero. No corresponding count of zero readings is reported for the adductor canal group.

A measurement at one postoperative time point cannot, by itself, describe how strength changes over time or establish the duration of any difference. The registry record does not report a minimal clinically important difference for this measure.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the Wilcoxon (Mann-Whitney) test compare?

The registry reports a Wilcoxon (Mann-Whitney) test for the primary comparison. General explanation: this rank-based method combines the observations from both groups, orders them, and evaluates whether the ranks tend to differ between groups. It is useful when an outcome is not well described by a simple comparison of means or when values are skewed or include many tied observations. The method does not automatically test a difference in medians under every possible distributional pattern. A median interpretation is clearest when the group distributions have comparable shapes and differ mainly by location.

The primary outcome has a large concentration at zero in the femoral nerve block group: the registry states that 20 of 26 subjects in that group had recorded strength of zero. Such ties can matter for rank-based testing because multiple observations receive the same rank. The registry does not say how ties were handled or whether an exact or approximate calculation was used. The reported p value is 0.026; the test specification and the p value are the reported inferential details.

Why report medians and ranges?

General explanation: a median gives the midpoint of ordered observations and is less affected by extreme values than a mean. A full range describes the lowest and highest observed values, but it does not show how observations are distributed between those endpoints. Here, the posted summaries are medians and full ranges: 1.1 Kgf and 0.0 to 25.6 for the Adductor Canal Block arm, and 0.0 Kgf and 0.0 to 15.3 for the Femoral Nerve Block arm. These summaries are consistent with describing a potentially non-symmetric outcome, but the record does not state why this summary format was selected.

General explanation: when an outcome has many zero values, its distribution can contain a mass at zero alongside positive values. That pattern can make a single summary such as a median incomplete as a description of the data. A full distribution, or a prespecified two-part analysis distinguishing any strength from positive strength, could address different questions, but neither additional analysis is reported in the registry record. No alternative endpoint definition or transformation is reported.

What does the p value say?

General explanation: a p value describes how surprising data at least as inconsistent with a specified null model would be, if that model and the test assumptions held. It is not the probability that the null hypothesis is true, and it is not a measure of the magnitude of an effect. The posted p value is 0.026. The registry record does not state the decision threshold used for this analysis, so the p value should be read as the reported test result rather than as a complete account of a prespecified decision rule.

A confidence interval would describe uncertainty around an estimated contrast on a defined scale. No confidence interval or test-based effect estimate is reported for this comparison. General explanation: an interval is useful because it can show both the range of effects reasonably compatible with the data and the precision of the estimate; a p value alone does not supply that information. The group ranges cannot substitute for an interval around a between-group effect.

What can be inferred from the design?

The registry identifies random allocation, triple masking, and a parallel model. General explanation: random allocation is intended to make treatment assignment independent of baseline characteristics on average, while masking is intended to limit influences arising from knowledge of assignment. These design labels do not establish how allocation or masking was implemented. The record does not report the randomization sequence, concealment procedures, which roles were masked, or whether masking was maintained.

The record does not describe adjustment for baseline values, covariates, clustering, or repeated measures. The primary measurement description mentions three dynamometer readings, but it does not state how those readings were combined to form the reported participant-level outcome. The details of any such processing are not reported in the registry record. Without an analysis plan and participant-level data, it is not possible to independently verify the test, evaluate sensitivity to ties, or assess the influence of missing observations.

The sample-size assumptions listed for planning illustrations are a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect expressed as a fraction of the observed effect. These describe planning assumptions, not observed trial findings. The registry record does not report a trial-specific sample-size justification, and no planning illustration should be read as observed power or as evidence that the trial had a particular ability to detect an effect.

10. Analyses Reported by the Sponsor

The registry’s reported analysis for the primary comparison is a Wilcoxon (Mann-Whitney) test with p = 0.026. The accompanying group summaries are medians and full ranges. These are the sponsor-reported inferential result and descriptive values available for interpreting quadriceps strength at 4 hours following peripheral nerve block performance.

No recalculated between-group effect estimate or confidence interval is reported in the registry record. The posted summaries do not provide the individual observations or enough detail about the handling of ties and the three dynamometer readings to reproduce the analysis independently. A recalculation that requires those details cannot be compared numerically with the sponsor’s test result. No discrepancy is recorded between a sponsor analysis and a recalculation.

General explanation: a recalculated comparison based only on summary statistics would be an unadjusted reconstruction, not a replacement for an analysis based on the trial’s individual data and prespecified methods. The registered test is a rank-based comparison, while the published summaries alone do not identify every feature of the data distribution. Interpretation should therefore center on the sponsor’s reported test and the observed group summaries, while recognizing that the record does not report a confidence interval or a comparative effect estimate.

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists three outcome measures and four analyses, but it does not provide posted secondary results. The primary endpoint discussed in the record is quadriceps muscle strength at 4 hours following peripheral nerve block performance. The stated rationale also mentions postoperative analgesia, its duration and quality, and early mobilization, but results for those outcomes are not reported in the registry record.

Multiplicity arises when several outcomes, time points, subgroups, or analyses are tested. General explanation: if many statistical tests are performed, the chance of at least one small p value can increase unless the analysis plan addresses that issue. The registry record does not report whether multiplicity adjustments were planned or applied, how the primary endpoint was distinguished from other outcomes in the analysis, or whether any secondary analyses were prespecified. It is therefore not possible to assess how the reported p value fits into a broader testing strategy.

The registry does not report a participant flow, the analysis population for the primary comparison, or the number of missing primary outcome measurements. The primary outcome description states that readings were recorded, but it does not establish whether all randomized participants contributed to the reported summaries. No imputation method, missing-data sensitivity analysis, or explanation for missing measurements is reported in the registry record. The femoral nerve group’s count of zero readings is an outcome finding, not a count of missing values.

General explanation: missing outcome data can affect an estimate if the probability of missingness is related to the outcome or differs between groups. Without information about missingness and the analysis population, readers cannot determine whether the posted comparison represents all randomized participants or a subset with recorded outcomes. The record also does not report subgroup analyses, interim analyses, or a statistical analysis plan that would clarify the handling of multiple looks at the data. These omissions limit assessment of robustness, but they do not establish that any particular procedure was or was not used.

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

The posted primary result describes quadriceps strength on the surgical side at 4 hours following peripheral nerve block performance. The Adductor Canal Block arm had a reported median of 1.1 Kgf and full range of 0.0 to 25.6; the Femoral Nerve Block arm had a median of 0.0 Kgf and full range of 0.0 to 15.3. The registry reports that 20 of 26 subjects in the femoral nerve block group had recorded strength of zero. The reported Wilcoxon (Mann-Whitney) p value is 0.026.

These findings describe the reported strength measure and its rank-based comparison at the specified time. They do not, on their own, quantify a clinically important difference. No confidence interval or comparative effect estimate is reported, and no threshold for interpreting the magnitude of a strength difference is given. General explanation: statistical evidence about a group comparison and the practical importance of a difference are related but distinct questions.

The result does not establish the quality or duration of postoperative analgesia. Although analgesia is part of the trial’s stated rationale, no secondary results are posted in the registry record. The strength measure also does not directly establish early mobilization, later quadriceps function, surgical recovery, or outcomes beyond the measurement time. These outcomes cannot be inferred from the four-hour strength comparison.

The randomized design is relevant to interpreting a comparison, but the available record does not detail randomization implementation, participant flow, missing outcome handling, or analysis populations. The result should be understood with those reporting limits in mind. It describes a reported outcome in this trial; it is not medical advice and does not determine which block is appropriate for an individual patient.

13. Why This Trial Matters Statistically

This trial is statistically interesting because its primary outcome is a functional measurement with many zero observations reported in one arm. The registry states that 20 of 26 subjects in the Femoral Nerve Block group had recorded quadriceps strength of zero at the four-hour assessment. Such a concentration can shape the distribution substantially, making the choice of summary and comparison method important. A median and range provide useful descriptive information, while the Wilcoxon (Mann-Whitney) test compares ranks rather than estimating a difference on the kilogram-force scale.

The record offers an opportunity to distinguish several statistical questions. The observed group medians describe central values. The rank-based p value addresses evidence against a null comparison under the test’s assumptions. Neither item gives a confidence interval for the magnitude of a between-group difference, and neither alone establishes the clinical importance of the result. The absence of a posted effect estimate and interval leaves the precision of the comparative effect less directly characterized.

The trial also illustrates how the registry’s stated motivation can extend beyond its posted primary result. The rationale discusses analgesia, muscle weakness, and early mobilization, while the primary endpoint is a dynamometer assessment at one time point. Without posted secondary results, the strength outcome cannot resolve every question that motivated the comparison. This distinction matters when aligning a statistical result with the clinical question readers may be asking.

Finally, transparent reporting of participant flow, missing measurements, outcome processing, and the analysis plan would help readers assess the robustness of a result with many zero values. The record identifies a randomized, triple-masked, parallel design, but does not report those further details. The trial therefore highlights both the value of a clearly timed functional endpoint and the limits of interpreting a single reported test without fuller analysis information.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary outcome is reported at one time point, 4 hours following peripheral nerve block performance. The registry does not report later strength measurements or posted results for the analgesia outcomes discussed in its rationale. The primary endpoint therefore cannot describe the course of quadriceps strength or the duration and quality of analgesia.

The group summaries contain medians and full ranges, and the record reports many zero strength observations in the Femoral Nerve Block arm. It does not provide participant-level data, a distributional plot description, or the corresponding count of zero readings in the Adductor Canal Block arm. The summaries alone cannot show the overall shape of the data or support independent verification of the rank-based comparison.

Important measurement and analysis details are not reported in the registry record. Although the outcome description mentions three dynamometer readings, it does not state how those readings were combined for the participant-level result. The record does not describe missing outcome data, the analysis population, a confidence interval, an effect estimate, an analysis plan, or a sample-size justification. It also does not give a clinical threshold for interpreting the magnitude of a strength difference.

The intervention descriptions are incomplete with respect to the injected solutions. The record identifies ultrasound-guided blocks, but does not provide a complete recipe for either arm in the posted descriptions. Details of randomization and masking implementation are also not reported. These are reporting limitations; they do not demonstrate that the procedures or analyses were necessarily inadequate.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Ultrasound Guided Adductor Canal Versus Femoral Nerve Blocks for Anterior Cruciate Ligament Reconstruction in Pediatrics — NCT03053401.
• Registry record last updated 2020-12-28; status last verified 2020-12.
• Results first posted 2020-12-28.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT03053401 is a completed randomized, triple-masked, parallel-group trial sponsored by Akron Children's Hospital. It compared Adductor Canal Block with Femoral Nerve Block for postoperative care after pediatric arthroscopic ACL reconstruction. Enrollment was 52, with 26 participants listed in each arm. The recorded start date was 2017-02-09, and the primary completion date was 2019-10-25.

The primary outcome was surgical-side quadriceps muscle strength in Kgf, measured 4 hours following peripheral nerve block performance. The reported medians were 1.1 for Adductor Canal Block and 0.0 for Femoral Nerve Block; full ranges were 0.0 to 25.6 and 0.0 to 15.3, respectively. The registry reports that 20 of 26 subjects in the Femoral Nerve Block group had recorded strength of zero. A Wilcoxon (Mann-Whitney) test was reported with p = 0.026.

The registry record does not report a confidence interval, comparative effect estimate, secondary outcome results, participant flow, missing-data approach, or full statistical analysis plan. Its primary result addresses strength at the stated time point, not the broader analgesia and mobilization questions in the trial rationale.