Trial Evaluating Postop Pain and Muscle Strength Among Regional Anesthesia Techniques for Ambulatory ACL Reconstruction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Trial Evaluating Postop Pain and Muscle Strength Among Regional Anesthesia Techniques for Ambulatory ACL Reconstruction (NCT02584452), a randomized na study. The primary outcome is Subjective Postoperative Pain Scores After Preoperative Femoral Nerve Block Plus Postoperative Continuous Adductor Canal Nerve Catheter Compared to Preoperative Femoral Nerve Block Plus Postop Saphenous Nerve Block at 48 Hours After Discharge From PACU..

2. Clinical Question

The trial also lists outcomes concerning pain on postoperative day 1, opioid consumption, quadriceps strength, physical therapy participation, later pain, ambulation, nausea and vomiting, and participants’ experience with analgesia. Those additional questions provide context for the broader comparison of regional anesthesia approaches, but they do not substitute for the primary pain result. Without posted outcome values, it is not possible to quantify the size or precision of the primary comparison.

3. Trial Design

The registry describes a completed, randomized, parallel-group trial sponsored by Vanderbilt University Medical Center. It lists enrollment of 59 and identifies the condition as anterior cruciate ligament rupture or tear. The trial began on 2015-11-03, had a primary completion date of 2018-03-01, and is marked completed. Its phase is recorded as NA, which is not a drug-development phase designation.

The record lists two intervention arms: Continuous Adductor Canal Nerve Catheter and Long Acting Single Bolus Adductor Canal Nerve Block. It describes the trial as unmasked, meaning masking is listed as none. The listed intervention set also includes drugs and procedures such as mepivacaine, an adductor canal catheter, an adductor canal nerve block, normal saline followed by bupivacaine, ropivacaine and dexamethasone, propofol, and fentanyl. Listing an intervention does not establish which treatment differences were intended to isolate or how each item was used across all participants.

There is an important wording ambiguity in the record. The primary outcome title describes a comparison between a preoperative femoral nerve block plus postoperative continuous adductor canal catheter and a preoperative femoral nerve block plus postoperative saphenous nerve block. The arm names instead describe continuous catheter versus long-acting single-bolus adductor canal block. The record does not explain how these descriptions correspond, so the comparison should be identified using the wording attached to the specific outcome rather than assuming the arm labels settle the question.

The registry record does not report the detailed randomization procedure, allocation concealment, the protocol’s sample-size justification, or a full statistical analysis plan. It also does not report whether there were interim analyses. These details should not be inferred from the randomized label or the listed interventions.

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: Two participants consented but withdrew from the study prior to randomization.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Data was unavailable for 1 participant in the Long Acting Single Bolus Adductor Canal Nerve Block group.

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 Subjective Postoperative Pain Scores After Preoperative Femoral Nerve Block Plus Postoperative Continuous Adductor Canal Nerve Catheter Compared to Preoperative Femoral Nerve Block Plus Postop Saphenous Nerve Block at 48 Hours After Discharge From PACU., measured over Post Operative Day 2.

The primary endpoint concerns subjective postoperative pain on postoperative day 2. The record describes measurement 48 hours after discharge from the post-anesthesia care unit and specifies an 11-point numeric pain scale, where 0 is no pain and 10 is the worst pain. The endpoint title frames the measure as a comparison between a preoperative femoral nerve block followed by a continuous adductor canal catheter and a preoperative femoral nerve block followed by a saphenous nerve block.

A patient-reported pain score captures a participant’s own assessment of pain at the specified assessment time. It is therefore different from an observer rating or a measure of medication use. The stated numeric scale gives a common response format, but interpreting a group comparison would require the actual observations and a clear account of how scores were summarized and analyzed. The record does not report those outcome values or a treatment-effect estimate.

The registry identifies the endpoint unit as participants and describes its parameter as a count of participants, while the endpoint description itself refers to scores on a numeric scale. That difference in registry presentation makes it especially important not to assume an unreported summary or analysis. The registry record also notes that primary pain data were unavailable for 1 participant in the long-acting single-bolus group. It does not explain how missing pain data were handled. Without the posted group results, the endpoint definition can be described, but the observed pain comparison and its precision cannot be assessed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomized parallel-group design. Randomization assigns participants to treatment groups by chance, with the aim of reducing systematic differences between groups at the start of a trial. A parallel-group design means participants are assigned to a group and assessed under that group’s approach rather than crossing through multiple treatments. These general features help frame a comparison, but do not establish that allocation was concealed or that the groups were similar in every relevant characteristic. The registry record lists randomization and a parallel model; it does not report the allocation sequence method or concealment procedures.

Unmasked assessment context. The record lists masking as none. In general, masking can reduce the influence of treatment knowledge on behavior, care, outcome assessment, or reporting. For a subjective outcome such as a participant-rated pain score, knowledge of treatment assignment could potentially influence the assessment. That is a general methodological consideration, not a claim that bias occurred in this trial. The record does not describe whether outcome assessors were separate from participants or clinicians, or what steps were taken to standardize assessments.

Outcome scale and summary. The primary outcome description specifies a numeric pain scale from 0, no pain, to 10, worst pain, assessed on postoperative day 2. A scale of this kind records ordered responses with numerical labels. Researchers may summarize such observations in different ways, and the choice of summary and statistical model should be clear because it affects the interpretation of a group contrast. The registry record does not report the group score distributions, the chosen summary statistic, or the primary statistical test. Although the endpoint is described in terms of participants and a count parameter in one registry entry, the clinical description is a pain score; the record does not clarify this presentation.

Effect estimates and uncertainty. In general, an effect estimate describes the observed difference or contrast between groups, while a confidence interval describes a range of values compatible with the data and the statistical model at a stated confidence level. A narrow interval indicates greater precision than a wide interval, all else equal. Neither an estimate nor its interval is reported for the primary pain comparison. A p-value, if reported, would address compatibility with a specified null model, but would not by itself describe the size or clinical importance of a difference. No primary p-value is reported.

Missing observations. The record states that pain data were unavailable for 1 participant in the Long Acting Single Bolus Adductor Canal Nerve Block group. Missing outcome data can affect precision and may affect the interpretation if the reasons for missingness are related to the outcome or treatment. Standard approaches include analyzing observed cases, imputing missing values under explicit assumptions, or conducting sensitivity analyses; these are general options, not descriptions of what this trial did. The registry record does not report the reason for the unavailable observation or the method used to address it.

Multiplicity and multiple outcomes. The registry lists 12 outcome measures, including primary and secondary outcomes. When many outcomes or time points are examined, the chance of at least one apparently unusual result can increase if each is tested separately. Statistical plans may address this through prespecified outcome hierarchies or multiplicity adjustments. The registry record does not report a multiplicity strategy, nor does it report a set of outcome analyses. The count of listed outcome measures alone does not show that all were tested or that any adjustment was made.

Planning calculations. General sample-size planning uses assumptions about the expected effect, variability or event frequency, significance level, power, and allocation. The registry record does not report the trial’s own sample-size justification. A separate planning illustration is described as based on the observed effect, two-sided significance level 0.05, equal allocation, and a normal approximation, with the target effect expressed as a fraction of the observed effect. Such calculations are planning illustrations, not observed power and not evidence that the trial was designed around those assumptions. Since the registry record does not report primary outcome results, those illustrations should not be read as establishing the trial’s result or its precision.

Analysis population and model checks. An analysis population specifies which participants are included in an outcome analysis, for example all randomized participants or only those with available measurements. The registry record does not report the primary analysis population or the model used for the pain endpoint. It therefore does not support claims about an intention-to-treat analysis, a per-protocol analysis, covariate adjustment, or model diagnostics. In general, a statistical method should match the outcome’s scale and distribution, and its assumptions should be considered. No model assumptions or checks are described in the record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 12 outcome measures, covering pain, opioid consumption, quadriceps strength, physical therapy participation, ambulation, nausea and vomiting, and experience with analgesia. Testing several outcomes can create a multiplicity issue: if each is assessed independently, the overall chance of a false-positive finding may be higher than for a single prespecified test. This general concern does not mean that the trial necessarily tested every listed measure. The registry record does not report a multiplicity adjustment, a hierarchy for secondary outcomes, or a complete analysis plan.

The record lists 0 analyses and does not report primary outcome results. It therefore gives no basis for judging whether the planned statistical methods were followed, whether secondary outcomes were analyzed, or how any multiplicity was handled. The primary question should remain distinct from the additional outcomes rather than treating the full list as a set of confirmed findings.

For the primary pain outcome, the registry notes unavailable data for 1 participant in the Long Acting Single Bolus Adductor Canal Nerve Block group. It does not describe the reason, whether the participant remained in other analyses, or how the missing score was handled. There is no reported account of missingness for the other outcomes.

The record does not identify the primary analysis population, such as all randomized participants or participants with observed measurements. It also does not report whether analyses were adjusted for baseline variables or whether any sensitivity analyses were conducted. These absences limit assessment of how missing data and analysis choices may have influenced the findings; because outcome results are not posted, the impact cannot be quantified.

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 record lists serious adverse events in the two named groups. For the Continuous Adductor Canal Nerve Catheter group, 34 participants were at risk, with 0 serious adverse events reported. For the Long Acting Single Bolus Adductor Canal Nerve Block group, 23 participants were at risk, also with 0 serious adverse events reported. Deaths are listed as 0 in each group. These are the registry’s reported counts and denominators.

The record also reports other, non-serious adverse events: 3 events-affecting participants among 34 at risk in the continuous-catheter group, and 4 among 23 at risk in the single-bolus group. These counts should be read with their group denominators. They do not, by themselves, establish that one approach has a higher or lower risk. A comparative safety assessment would require a clear definition of the events, a specified analysis, and consideration of the amount and completeness of follow-up.

The registry does not list any top serious adverse event terms. A count of zero serious adverse events in the posted record is not proof that serious harms are impossible or that the groups have identical safety profiles. The record does not provide event-level descriptions, timing, relatedness assessments, or a statistical comparison. These safety counts are separate from the unreported primary pain outcome and should not be used to infer its result.

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

The registry entry establishes that a randomized, parallel-group trial was conducted to investigate postoperative analgesia and muscle strength in ambulatory anterior cruciate ligament reconstruction. It records a primary question about subjective pain on postoperative day 2 and describes a numeric pain scale. It also lists other outcomes spanning pain at different times, opioid consumption, strength, physical therapy participation, ambulation, nausea and vomiting, and participant experience.

What the entry does not establish is the observed effect of either regional anesthesia approach. No primary pain scores, group contrast, confidence interval, or p-value are reported. The registry’s stated hypothesis about lower pain and improved quadriceps strength is an objective, not an outcome result. Accordingly, the record cannot support a conclusion that one approach reduced pain, improved strength, or produced equivalent outcomes.

The record does include safety counts: no serious adverse events or deaths are listed in either group, and other adverse events are reported in both groups. These counts are descriptive. Without event details and a comparative analysis, they do not establish equivalence or a safety advantage.

There is also a discrepancy in how the comparison is named. The primary outcome description refers to a postoperative saphenous nerve block, while the two arm descriptions name continuous-catheter and long-acting single-bolus adductor canal approaches. The registry record does not explain the relationship between those formulations. Readers should not assume that the descriptions are identical or that the comparator can be resolved from the record.

Overall, the record supports a careful account of the trial’s purpose, design labels, outcome definitions, and reported adverse-event counts. It does not support a treatment-effect claim. The absence of posted efficacy results is an information limitation, not a finding of no difference. Any interpretation of the intended comparison must remain bounded by that missing outcome information and the uncertainty in the comparator description.

13. Why This Trial Matters Statistically

This trial raises several useful statistical issues for clinical researchers. First, a randomized design is an important basis for comparing groups, but randomization alone does not reveal the size or precision of an effect. The record identifies the design, yet without posted outcome estimates it is not possible to assess whether the primary comparison was small, large, or uncertain.

Second, the primary endpoint is a subjective score collected at a defined postoperative time. Clear reporting should connect the measurement scale to the statistical summary and analysis. Here, the clinical description specifies a pain rating from 0 to 10, while another part of the endpoint record describes the measure as a participant count. That presentation highlights why endpoint definitions should be internally clear before readers interpret a result.

Third, the entry illustrates the importance of consistent comparator descriptions. The primary outcome names a postoperative saphenous nerve block, whereas the listed arms distinguish continuous catheter from single-bolus adductor canal block. Without an explanation linking these terms, readers cannot be certain which intervention contrast the primary outcome represents.

Fourth, outcome completeness matters. The record identifies unavailable primary pain data for 1 participant in one group but does not describe the handling of that observation. Even a small amount of missing data should be accompanied by a transparent account of the analysis population and assumptions, particularly for a patient-reported endpoint.

Finally, multiple outcome measures and safety counts need appropriate context. A list of outcomes is not a set of findings, and descriptive adverse-event counts are not a comparative risk analysis. The record’s limited analysis reporting makes restraint essential: the design and questions can be described, but the treatment effect cannot be inferred. This distinction is central to statistical interpretation in clinical research.

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 for interpretation is that the registry record does not report the primary pain results. Group summaries, an estimated contrast, a confidence interval, and a p-value are all absent. The same limitation prevents assessment of the stated strength hypothesis and the other listed outcomes. The registry lists 0 analyses, so no inferential result can be evaluated.

The record’s description of the comparison is not fully consistent. The primary outcome names preoperative femoral nerve block plus postoperative continuous adductor canal catheter versus preoperative femoral nerve block plus postoperative saphenous nerve block. The arm descriptions instead name continuous catheter and long-acting single-bolus adductor canal block. The registry does not explain how these descriptions map to each other.

The entry gives limited information about participants beyond the condition and enrollment of 59. Detailed eligibility criteria, participant characteristics, and the reasons for unavailable primary data are not reported in the registry record. The record notes that data were unavailable for 1 participant in the long-acting single-bolus group, but does not state how that observation was handled or identify the analysis population.

Important design and analysis details are also not reported in the registry record, including the randomization procedure, allocation concealment, sample-size justification, primary statistical model, multiplicity strategy, and any interim analyses. The listed masking status is none, but the record does not further describe outcome assessment procedures. These gaps limit assessment of potential sources of bias and the precision or robustness of any result.

The safety information is limited to group-level event counts and denominators. Event descriptions, timing, relatedness, and comparative statistical analyses are not reported. Consequently, the adverse-event counts are descriptive and do not resolve comparative safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Trial Evaluating Postop Pain and Muscle Strength Among Regional Anesthesia Techniques for Ambulatory ACL Reconstruction — NCT02584452.
• Registry record last updated 2019-12-11; status last verified 2019-11.
• Results first posted 2019-11-18.
• 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

NCT02584452 is a completed randomized, unmasked, parallel-group trial sponsored by Vanderbilt University Medical Center. Enrollment is listed as 59. The record concerns regional anesthesia techniques for ambulatory anterior cruciate ligament reconstruction and identifies postoperative day 2 subjective pain as the primary outcome. Pain is described using an 11-point numeric scale from 0, no pain, to 10, the worst pain.

The primary outcome wording compares a continuous adductor canal catheter approach with a postoperative saphenous nerve block approach, while the arm descriptions name continuous catheter and long-acting single-bolus adductor canal block. The registry does not explain this difference. It lists 12 outcome measures and 0 analyses; primary pain results and other efficacy results are not reported. Primary pain data were unavailable for 1 participant in the long-acting single-bolus group.

The safety record lists 0 serious adverse events and 0 deaths in each group. Other adverse events are reported as 3 among 34 at risk in the continuous-catheter group and 4 among 23 at risk in the single-bolus group. These counts do not establish a comparative effect. The protocol’s sample-size justification and detailed statistical analysis plan are not reported in the registry record.