iPACK for Post-op Pain Following ACL Reconstruction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for iPACK for Post-op Pain Following ACL Reconstruction (NCT05498870), a randomized phase 4 study. The primary outcome is Pain Scores.

2. Clinical Question

3. Trial Design

This is a completed, randomized, parallel-group Phase 4 study registered as NCT05498870. The registry lists an enrollment of 82. The study began on 2022-08-25, and the primary completion date is 2023-07-03. The sponsor is the Medical University of South Carolina.

Eligible participants were described as patients 12 years and older undergoing ACL reconstruction using a quadriceps or bone-patella tendon bone (BTB) graft. Participants were assigned to ACB alone or ACB plus iPACK. The registry classifies masking as single, but does not report which people involved in the study were masked or how masking was maintained. It also does not report the sequence-generation or allocation-concealment procedures.

The primary outcome was pain scores during the first 72 hours after surgery. The planned measure was a subjective Visual Analog Scale score collected at 12-hour intervals. The registry describes the outcome parameter as a mean and its dispersion as a standard error. Secondary outcomes were total postoperative opioid consumption, expressed as total MME, and range of motion in degrees. The record lists three outcome measures but no analyses. It therefore documents the intended comparison and outcome collection, not the estimated treatment contrast or its uncertainty.

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: Each participant contributed one study knee. They underwent an ACL reconstruction on one single knee to qualify for participation in the study.

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 Pain Scores, measured over 0-72 hours post op.

The primary endpoint is postoperative subjective pain, measured with a Visual Analog Scale. The scale runs from 0, meaning no pain, to 100, meaning severe intolerable pain. The registry says scores were to be collected at 12-hour intervals during the first 72 hours after surgery and that higher scores indicate a worse outcome.

Pain scores are continuous measurements: they can take values across a scale rather than being limited to categories such as pain present or absent. A mean can describe the central level of scores in a group, while a standard error describes the precision of an estimated mean. These measures answer different questions; the standard error is not a description of the range of individual participants’ scores.

Repeated measurements can characterize how scores vary across the postoperative period, but their interpretation depends on how the measurements are combined or compared. The registry identifies multiple collection times and notes that the outcome has not been reduced to a single comparison. It does not report the observed scores, a summary across time, a group contrast, or the analysis used to account for measurements from the same participant. Thus, the endpoint definition is available, but its results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies randomized allocation and a parallel-group design. In a randomized study, assignment is intended to create groups whose measured and unmeasured characteristics are comparable on average, though random assignment does not guarantee that every observed characteristic will be balanced. The parallel design means participants are assigned to one of the listed block strategies rather than being described as receiving both strategies in sequence. The record does not report how the random sequence was generated, whether assignment was concealed before enrollment, or whether the intended allocation was achieved.

What does randomization contribute?

Randomization can support a causal comparison when assignment, follow-up, outcome measurement, and analysis are carried out appropriately. It does not by itself remove problems such as missing outcome measurements, departures from assigned treatment, or selective reporting. The registry record does not describe adherence, crossovers, or the analysis population. Those details matter because they clarify whether the estimated comparison concerns assigned treatment, treatment received, or another defined group.

What does single masking mean?

The registry classifies the study as single-masked. Masking can reduce the influence of expectations on care, outcome assessment, or reporting, depending on who is unaware of assignment. The record does not identify who was masked or describe the masking procedures. Since the primary outcome is a subjective pain score, knowledge of treatment assignment could be relevant to the measurement process; the available record is not sufficient to judge whether or how that concern was addressed.

How should means and standard errors be read?

The primary outcome is continuous, and the registry identifies the mean as the parameter of interest and the standard error as its dispersion measure. A mean describes an average score. A standard error describes the precision of an estimated mean, with smaller standard errors generally indicating greater precision under the assumptions of the analysis. It does not show how widely individual participants’ scores vary. A measure of participant-level variability, such as a standard deviation or a distribution of scores, is not reported in the registry record.

When comparing groups, a mean difference is interpretable only alongside its uncertainty and a clear definition of what has been averaged. A confidence interval is a general way to show a range of values compatible with the estimate under the statistical model. It does not guarantee that the true effect lies within that interval. No confidence interval or mean difference is reported for this primary endpoint.

Why do repeated pain measurements require an analysis choice?

The planned collection of scores at 12-hour intervals means that participants contribute measurements over time. Scores from the same participant are generally related, so treating every recorded score as if it came from a different participant would fail to account for that within-participant dependence. In general, repeated-measures methods model this correlation or reduce the measurements to a prespecified summary. The appropriate method depends on the scientific question and the data structure. The registry record does not report a repeated-measures model, a summary rule, or a specific group contrast. It explicitly indicates that the primary outcome has several categories or time points and has not been reduced to one comparison.

What do the planning assumptions describe?

The record describes sample-size illustrations based on a fraction of the observed effect, using a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. Such illustrations are planning calculations: they show the participants per arm that would be associated with specified assumptions, rather than the probability that this completed trial detected an effect. They are not observed power. The registry record does not report the trial’s own sample-size justification or a protocol-based calculation. It also does not provide the primary outcome estimate needed to assess the observed effect from the record alone.

General statistical interpretation should distinguish a planning assumption from an analysis result. A significance level is a threshold chosen for a testing procedure; it is not the probability that a treatment effect is true. Equal allocation and a normal approximation are assumptions of the described illustration, not confirmation that the analyzed data followed those assumptions. No inferential test or primary outcome estimate is reported in the registry record, so the planning description cannot substitute for results.

10. Multiplicity, Missing Data and Analysis Populations

The primary pain endpoint was planned at multiple time points, and the record also lists opioid consumption and range of motion as secondary outcomes. Testing or estimating several outcomes can raise multiplicity concerns: the chance of at least one apparently notable finding can increase when many comparisons are considered. In general, a statistical plan may address this through a prespecified primary contrast, an adjustment procedure, or a clearly prioritized interpretation. The registry record does not report a multiplicity strategy, a hierarchy of tests, or which time-point comparison would be primary.

Missing-data handling is also not reported. The record does not state how many pain scores were missing, why measurements might be unavailable, or how incomplete repeated measurements would be handled. In general, the consequences of missingness depend on its amount, reasons, and relation to observed or unobserved outcomes; an analysis method cannot be evaluated without those details.

The analysis population is not described. The registry does not state whether the intended analysis was based on randomized assignment, treatment received, or another population, nor does it report exclusions after randomization. The record lists enrollment of 82 and gives separate risk-set counts for safety outcomes, but does not explain the relationship between those counts and any efficacy analysis. No analyses are listed, so multiplicity procedures, missing-data methods, and population definitions cannot be checked against reported results.

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.

Most frequent non-serious adverse event terms

The safety entries list serious adverse events as affecting 0 participants in the ACB-only group, with 34 at risk, and 0 participants in the ACB plus iPACK group, with 38 at risk. Deaths are also listed as 0 in both groups. For other adverse events, the record lists 6 affected participants among 34 at risk in the ACB-only group and 8 among 38 at risk in the ACB plus iPACK group.

These are counts as entered in the registry, not estimates of comparative risk. No statistical comparison, uncertainty interval, event descriptions, or exposure-adjusted analysis is reported. The record lists no serious adverse-event terms. The risk-set counts should be read as the denominators attached to these safety entries; the registry does not explain their relation to the enrollment count of 82 or to the populations used for other outcomes. A zero count in these entries means that no affected participants are recorded for that category in the listed group; it does not establish that the possibility of such an event is absent.

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

The registry record describes a randomized comparison of ACB alone with ACB plus iPACK among patients undergoing ACL reconstruction. Its primary question concerns subjective pain scores during the first 72 hours after surgery. The record supplies the planned scale, timing, and direction of scoring, but it does not report the pain-score values or the results of a comparison between groups.

That distinction is central to interpretation. A study’s design and endpoint definition explain what investigators intended to learn; they do not establish what the collected data showed. Without an estimated group contrast and an indication of its precision, it is not possible to determine from this record whether scores differed, how large any difference was, or how uncertain an estimate might be. No conclusion about comparative pain outcomes should be drawn from the absence of a posted analysis.

The registry also lists opioid consumption and range of motion as secondary outcomes. Their results are not reported in the record. The safety entries provide counts for adverse events and deaths, but do not include a statistical comparison or enough context to interpret the counts as comparative estimates. These entries address a different question from the primary pain endpoint.

In general, a clinically meaningful interpretation would consider the size and precision of a prespecified contrast, the chosen time summary, the completeness of measurements, and the study population. It would also distinguish statistical evidence from clinical importance. The registry record does not provide the outcome estimates or analysis details needed for those judgments. The appropriate reading is therefore limited: the trial’s planned comparison and several outcome definitions are documented, while the comparative results are not reported in the registry record.

13. Why This Trial Matters Statistically

This trial raises statistical questions that are important in studies of postoperative pain. Pain is measured repeatedly and subjectively, so the analysis must define what aspect of the time course is being compared. A contrast at a particular time, an average across the observation period, and a model of change over time can represent different questions. The registry identifies the measurement schedule but does not report which summary or model was used.

Random allocation is a useful design feature because it supports comparison of the assigned strategies, subject to the conduct and analysis of the study. The registry also identifies a parallel-group design and a single-masked classification. However, the available record does not specify sequence generation, allocation concealment, or who was masked. Those details help readers assess how assignment and subjective measurement may have been protected from bias.

The record’s primary and secondary outcomes also illustrate why prespecification and multiplicity matter. Pain is the primary outcome, while opioid consumption and range of motion are listed as secondary outcomes. Multiple time points and outcomes can make the interpretation depend on which analyses were planned and how they were prioritized. No multiplicity approach or analysis plan is reported.

Finally, the registry distinguishes a completed study from a report of its findings. Although the record gives the trial status and outcome definitions, it lists no analyses and does not report the primary or secondary estimates. This makes the case a useful reminder that a registration record can clarify what a study set out to measure without supplying the evidence needed to evaluate its results.

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 principal limitation for interpreting this trial from the registry record is the absence of reported outcome analyses. The primary pain scores, group estimates, contrasts, confidence intervals, and p-values are not reported. The listed secondary outcomes also have no reported results. Consequently, the comparative effects and their precision cannot be evaluated.

The primary endpoint has multiple planned time points, but the registry record does not identify a single summary or explain how repeated measurements were analyzed. It does not report whether a model accounted for within-participant correlation, which time-point contrasts were planned, or how multiplicity was addressed. The record also does not describe missing-data handling or define the analysis population.

Some design details are absent. Although the study is classified as randomized and single-masked, the record does not describe sequence generation, concealment, or who was masked. It does not report adherence to assigned blocks, post-randomization exclusions, or details of outcome assessment beyond the stated pain scale and timing. Further eligibility characteristics and participant characteristics are not reported.

The registry lists enrollment of 82 and separate at-risk counts for adverse events, but does not explain the relationship between those figures. The safety entries also lack event terms for serious events and do not include comparative estimates or uncertainty. Finally, the described sample-size assumptions are planning illustrations; the registry does not report the trial’s own sample-size justification. These limits concern what can be learned from the registry record and should not be mistaken for findings about the trial’s underlying data.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: iPACK for Post-op Pain Following ACL Reconstruction — NCT05498870.
• Registry record last updated 2024-10-16; status last verified 2024-10.
• Results first posted 2024-07-10.
• 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

NCT05498870 is a completed, randomized, parallel-group Phase 4 study sponsored by the Medical University of South Carolina. It lists enrollment of 82 and compares ACB alone with ACB plus iPACK in patients 12 years and older undergoing ACL reconstruction with a quadriceps or BTB graft. The primary outcome is Visual Analog Scale pain during the first 72 hours, measured at 12-hour intervals. Secondary outcomes are total postoperative opioid consumption and range of motion.

The record lists no analyses and does not report the primary or secondary outcome results. It gives safety counts for serious and other adverse events and deaths, but does not provide comparative statistical estimates. Its design and endpoint descriptions identify the questions the study was intended to address; they do not establish the observed results.