Acupuncture ACL (Anterior Cruciate Ligament): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Acupuncture ACL (Anterior Cruciate Ligament) (NCT03711734), a randomized na study. The primary outcome is Bang Blinding Index (BI).

2. Clinical Question

The clinical question is therefore about the feasibility of masking in a perioperative acupuncture trial, not primarily about whether acupuncture changes pain. Pain at rest, pain with movement and opioid consumption were secondary outcomes. Their results can add context about early postoperative experience, but they do not replace the primary assessment of whether participants could identify their assignment.

The registry describes a randomized comparison of acupuncture plus standard of care against standard of care without acupuncture. Because both groups received standard care, the contrast concerns the addition of acupuncture within this trial’s perioperative setting. The registry record does not report a separate comparison of acupuncture with no anesthesia or with no analgesia.

3. Trial Design

The registry record describes a completed, randomized, parallel-group feasibility trial with triple masking. Enrollment was 40. The trial compared acupuncture plus standard of care with no acupuncture plus standard of care among patients undergoing ACL surgery. Its stated central purpose was to evaluate whether adequate patient blinding was possible when acupuncture was delivered in the intraoperative setting while patients were sedated.

The intervention descriptions say that both groups received spinal anesthesia with IV sedation, as well as intraoperative anti-emetics and analgesics. The acupuncture group received ATP acupuncture at ear points, while the comparator group did not. The arm descriptions are incomplete in the registry record, so full procedural details are not reported in the registry record. The registry lists phase as NA.

The primary endpoint was the Bang Blinding Index on postoperative day 1. The primary results include 20 participants assigned to acupuncture and 19 assigned to no acupuncture. The registry notes one patient lost to follow up. The number of participants contributing to secondary results varies by outcome: pain at rest includes 20 and 19, pain with movement includes 19 and 18, and opioid consumption includes 20 in each group.

Study start was 2018-11-01, primary completion was 2019-12-13, and status is completed. The sponsor is Hospital for Special Surgery, New York. The registry record does not report the planned sample-size justification, detailed allocation procedures, the method used to maintain masking, or a full statistical analysis plan. It also does not report whether any interim analyses were planned or performed. These details should not be inferred from the randomized and triple-masked design labels alone.

The posted results include the primary endpoint and three secondary outcomes. No reported analyses are listed for the secondary outcomes. This means the registry record supplies arm-level outcome summaries but does not describe a sponsor-reported inferential analysis for those endpoints.

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: One patient was lost to follow up.

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.

Population: Number of all participants for whom baseline characteristics were measured, in each arm/group and in the entire study population (total)

6. Primary Endpoint

The registry lists the primary outcome as Bang Blinding Index (BI), measured over postoperative day 1.

The primary endpoint is the Bang Blinding Index, measured on postoperative day 1. It is intended to quantify patients’ ability to determine whether they received acupuncture. The registry describes the index as ranging from -1 to 1: values closest to 0 indicate less likelihood that participants guessed their assignment, while a value of 1 or -1 indicates that participants were able to guess which group they were in. The index is obtained by asking participants which group they believe they were randomly assigned to.

This measure is used because blinding is a particular feasibility concern in trials of acupuncture. If participants can identify their assignment, their expectations or awareness may influence reported experiences such as pain. The trial’s stated focus is whether patient blinding is possible when acupuncture is delivered during surgery while the patient is sedated. The endpoint therefore addresses a design question that matters when interpreting later patient-reported outcomes.

The registry reports the mean index and a 95% confidence interval for each group. The acupuncture group’s mean was 0.2, with a 95% confidence interval from -0.02 to 0.42. The no-acupuncture group’s mean was 0.11, with a 95% confidence interval from -0.1 to 0.31. These are group-level estimates; they do not reveal how each individual participant guessed or how many participants selected each possible response. A distribution of individual guesses is not reported in the registry record.

The index should be read as a measure of blinding, not as a pain score or a direct estimate of analgesic effect. Its value is relevant to whether the study design can support blinded assessment, but it does not by itself establish that the treatment changes postoperative pain or opioid use.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a continuous score summarized by a group mean and a 95% confidence interval. A mean gives the central value across participants in a group, while a confidence interval describes the statistical uncertainty around that estimate. In repeated use, intervals constructed in the same way would cover the underlying quantity at the stated rate, under the assumptions of the method. For an individual trial, an interval is not a guarantee that the true value lies inside it. The primary intervals are arm-specific; they estimate each group’s mean index, not the difference between groups.

The index has a defined range from -1 to 1. Its interpretation depends on direction and distance from 0: values closer to 0 correspond to less likelihood that participants guessed their assignment, whereas either endpoint corresponds to participants being able to guess their group. The group means being near 0 are therefore relevant to the stated blinding question. A mean can nevertheless conceal variation in individual responses. Opposing guesses can average toward 0, so a group mean alone does not describe the pattern of responses or prove that each participant was unaware of assignment. Individual response counts or distributions are not reported in the registry record.

A direct treatment-group comparison would ordinarily estimate how far apart the group means are and quantify uncertainty around that contrast. The registry record does not report such a primary comparison. It is important not to infer a formal test by comparing the two arm-specific confidence intervals visually: interval overlap is not itself a test of the difference, and separate intervals answer a different question from an interval for a contrast. No primary between-group p-value is reported in the registry record.

For the continuous secondary outcomes, the registry reports arm means and standard deviations. A standard deviation describes how spread out participant values are around a group mean; it is not the same as the standard error or a confidence interval. The posted secondary comparisons are unadjusted recalculations from these summary statistics. They express the mean difference as the no-acupuncture group relative to the acupuncture group. A negative mean difference therefore indicates a lower observed mean in the no-acupuncture arm for these comparisons. The accompanying confidence intervals quantify uncertainty around those recalculated contrasts, and the unadjusted p-values describe the compatibility of the observed contrast with a null difference under the calculation’s assumptions.

A confidence interval for a mean difference that includes zero indicates that the summary data are compatible with no difference as well as with differences in either direction at the interval’s stated confidence level. It does not show that the groups are equivalent. Establishing equivalence would require a prespecified margin and an analysis designed for that purpose; neither is reported in the registry record. Similarly, a p-value above a conventional significance threshold does not show that the null hypothesis is true or that clinically meaningful differences have been ruled out.

The secondary outcome comparisons should be treated as exploratory descriptions rather than as confirmatory trial conclusions. The registry lists three secondary outcomes and no reported analyses for them. The displayed unadjusted comparisons do not account for the possibility of examining multiple outcomes. When several outcomes are assessed, some apparently notable results can occur by chance even if there is no underlying effect. Adjustment methods or a prespecified hierarchy can address that concern, but the registry record does not report a multiplicity plan. The unadjusted results are therefore best read as context for the trial’s feasibility question, not as independent proof of a treatment effect.

The sample-size illustrations use the observed secondary effect as a planning reference and show what participant counts per arm would correspond to selected fractions of that effect under stated assumptions. They assume a two-sided significance level of 0.05, equal allocation and a normal approximation. These are hypothetical planning calculations, not the trial’s original sample-size justification, which is not reported in the registry record. They are not observed power. Because the observed effects in a small study can be imprecise, planning directly from them can produce unstable estimates of future sample size. The illustrations should be read as conditional examples rather than prescriptions or evidence that a particular effect is real.

Continuous-outcome comparisons generally rely on assumptions about the outcome distribution and the sampling behavior of the mean. The registry’s posted summary statistics do not establish whether those assumptions were checked. The record does not report the method used to calculate the secondary comparisons, whether any adjustments were made for baseline characteristics, or whether analyses were conducted according to assignment regardless of treatment received. Those choices can affect interpretation, so they should not be posted by inference.

Missing outcome data also matter. The primary endpoint includes 20 participants in the acupuncture group and 19 in the no-acupuncture group, with one patient lost to follow up noted by the registry. Secondary outcome counts differ across endpoints. A change in the number of participants contributing to an outcome can affect precision and may affect the result if missingness is related to participant characteristics or outcome values. The registry record does not report why observations are missing, how missing outcomes were handled, or which analysis population was used. No imputation or sensitivity analysis is reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary endpoint and three secondary outcomes. It does not report a statistical analysis plan, a hierarchy for testing outcomes, or a method for controlling multiplicity. Without that information, the unadjusted secondary p-values should not be interpreted as if they came from a single prespecified confirmatory test. Examining multiple outcomes can increase the chance of apparently notable findings, which is why planned testing procedures and transparent outcome priorities matter.

The primary endpoint results are presented as group means and confidence intervals, but a formal between-group analysis is not reported in the registry record. The registry also lists no reported analyses for the secondary outcomes. The unadjusted comparisons calculated from the secondary summary statistics are descriptive re-calculations, not substitutes for a documented analysis plan. Whether they were intended as exploratory or confirmatory is not reported in the registry record.

One patient was lost to follow up for the primary endpoint, leaving 20 participants in the acupuncture group and 19 in the no-acupuncture group. Secondary outcome counts differ by outcome: pain at rest has 20 and 19 participants, pain with movement has 19 and 18, and opioid consumption has 20 and 20. Reasons for missing observations, the handling of missing data, and whether any imputation or sensitivity analyses were performed are not reported in the registry record.

The analysis population is also not reported in the registry record. In particular, the record does not say whether the estimates follow an intention-to-treat approach, a per-protocol approach, or another population definition. The randomized design alone does not answer that question. These omissions limit assessment of how missing outcomes and analysis choices may influence the results. They do not invalidate the posted summaries, but they make the results less fully auditable and narrow the conclusions that can be drawn.

11. 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 reports zero serious adverse events in each arm. There were 20 participants at risk in the acupuncture group and 20 in the no-acupuncture group. The registry also reports zero other adverse events in each group and zero deaths in both groups. No serious adverse event terms are listed.

These figures describe the adverse events recorded in the registry for this trial. They do not establish that no adverse events occurred beyond those captured or reported, and they do not demonstrate that uncommon harms are absent. With 20 participants at risk in each group, the safety figures provide only a limited view of events in this study. The registry does not provide additional detail about event definitions, surveillance procedures, timing, or the criteria used to judge relationship to the intervention.

The absence of recorded events in these summaries should therefore be read as a report of zero events in the posted categories, not as a broad safety conclusion. The findings apply to this trial’s enrolled participants and the perioperative care described in the registry record. They do not support medical advice or general conclusions about safety in other settings.

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

The main result concerns whether patients could identify their randomized assignment after undergoing ACL surgery with intraoperative sedation. The group means for the Bang Blinding Index were close to 0, and each group’s confidence interval includes 0. Under the index’s definition, that pattern is relevant to the feasibility of patient blinding. However, a mean near 0 does not show that every participant was unaware of assignment, and the registry does not report individual guesses or a formal primary comparison between groups.

The findings therefore do not settle whether blinding succeeded according to a prespecified criterion. No such criterion is reported in the registry record. They also do not establish that acupuncture changes pain, opioid consumption, or recovery. Those outcomes are secondary, and the available unadjusted comparisons have substantial uncertainty and no reported multiplicity strategy. A lack of clear separation in these results is not evidence of equivalence.

The study’s stated purpose was feasibility, particularly patient blinding in an intraoperative setting where participants were sedated. Its value is in addressing a design question that can influence how later trials are planned and interpreted. The result is specific to the population, intervention and perioperative procedures described in the registry record. The incomplete intervention descriptions and absence of details about masking implementation further limit how readily the findings can be applied to other contexts.

The trial’s enrollment of 40 and its endpoint-specific participant counts also constrain precision. The primary confidence intervals cover a range of possible group means, while the registry does not provide a direct contrast estimate. The secondary outcome calculations likewise do not rule out differences. The sample-size illustrations are planning examples based on observed effects, not proof that those effects exist and not a measure of power achieved by the completed trial.

In short, the posted results provide preliminary information about patient blinding and early postoperative outcomes in this feasibility study. They do not establish a clinical benefit, establish no benefit, or answer broader questions about acupuncture across procedures and care settings. Interpretation should remain anchored to the recorded endpoint definitions, available participants and limitations in the registry’s analysis reporting.

13. Why This Trial Matters Statistically

Blinding is a central design issue when outcomes depend on participants’ reports. If participants can infer their assignment, expectations may affect how they describe pain or other experiences. A trial that directly measures participants’ ability to guess assignment can therefore help researchers assess a potential source of bias, rather than assuming masking was successful because it was planned.

This trial focuses on that issue in a specific and challenging context: acupuncture during surgery while patients are sedated. The Bang Blinding Index offers a structured measure of participants’ beliefs about assignment, and the postoperative day 1 assessment makes the question concrete. The results are relevant to feasibility planning because they show the observed group-level index estimates and their uncertainty rather than relying only on the trial’s masking label.

The study also illustrates why feasibility outcomes should be separated from efficacy outcomes. Pain scores and opioid consumption may be important secondary measures, but their role does not turn the trial into a definitive treatment-effect study. Small enrollment, endpoint-specific participant counts, unadjusted comparisons and the absence of a reported multiplicity plan all limit what can be concluded from the secondary results. The primary blinding question remains distinct.

Finally, the registry record highlights the importance of reporting analysis details. Clear definitions of the target population, missing-data handling, planned comparisons and success criteria would help readers judge how strongly a feasibility result supports future study design. In the absence of those details, the posted estimates still inform discussion, but they should be interpreted as limited evidence about blinding in this particular trial rather than a general answer about acupuncture studies.

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 most direct limitation is that the registry reports arm-specific primary means and confidence intervals but not a formal between-group comparison. The group estimates are useful for describing the observed index, but they do not quantify the uncertainty around a contrast. The registry also does not report a threshold for deciding that patient blinding was adequate, so the feasibility result cannot be classified against a stated success criterion.

The primary endpoint is a mean score derived from participant guesses. A mean can hide the distribution of individual responses, including whether participants tended to guess correctly, incorrectly or not at all. Individual response counts and the reasons participants gave for their guesses are not reported in the registry record. The posted result therefore gives an incomplete view of how masking functioned for particular participants.

One participant was lost to follow up for the primary endpoint, and outcome counts vary for the secondary endpoints. The reason for the missing data and the methods used to address it are not reported. The analysis population, treatment adherence, and any sensitivity analyses are also not reported in the registry record. These details would help assess whether the estimates reflect all randomized participants and how robust they are to missing observations.

The intervention descriptions are truncated, and the record does not provide full details of the acupuncture procedure or how masking was maintained and assessed beyond the index. The statistical analysis plan, sample-size justification, and interim analysis procedures are not reported. The secondary comparisons are unadjusted recalculations, and no multiplicity strategy is recorded. Together, these gaps limit reproducibility and make the secondary results exploratory.

Finally, this was a feasibility trial with enrollment of 40 in a specific surgical and perioperative setting. Its estimates should not be assumed to apply to different procedures, patient groups, acupuncture protocols or anesthesia approaches. The record does not support broad conclusions about analgesic effects or safety beyond the participants and outcomes reported.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Acupuncture ACL (Anterior Cruciate Ligament) — NCT03711734.
• Registry record last updated 2024-12-27; status last verified 2024-12.
• Results first posted 2024-04-26.
• 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

NCT03711734 is a completed randomized, triple-masked, parallel-group feasibility trial sponsored by Hospital for Special Surgery, New York. It enrolled 40 participants undergoing ACL surgery and compared acupuncture plus standard of care with no acupuncture plus standard of care. The registry lists the primary outcome as the Bang Blinding Index on postoperative day 1, measuring participants’ ability to guess their assigned group.

The primary mean index was 0.2 in the acupuncture group and 0.11 in the no-acupuncture group; the registry notes one patient lost to follow up. Three secondary outcomes were posted: pain at rest, pain with movement and opioid consumption. The secondary comparisons are unadjusted recalculations from arm-level summaries, and no reported analyses are listed for those outcomes. The registry reports zero serious adverse events, other adverse events and deaths in both arms.

The record does not report a formal primary between-group analysis, a statistical analysis plan, multiplicity handling, missing-data methods, or an analysis population. The results provide limited feasibility and descriptive information, not a definitive assessment of treatment effects.