Hip Scope Fascia-iliaca (FI) Block Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Hip Scope Fascia-iliaca (FI) Block Study (NCT02365961), a randomized phase 4 study. The primary outcome is Visual Analog Scale.

2. Clinical Question

The trial concerns people undergoing a hip scope procedure. The registry lists hip dysplasia, femoroacetabular impingement and acetabular labrum tear among the conditions. It does not give further eligibility criteria or describe the characteristics of the participants who enrolled.

The registry describes postoperative pain and clinical outcomes as being assessed through 3 months. Opioid consumption is listed as a secondary outcome. The primary pain measure is on a scale where 0 is no pain and 10 is the worst possible pain. These data describe the registered outcome and trial arms; they do not establish that either approach caused a particular pain experience.

3. Trial Design

The registry identifies this as a Phase 4, randomized, single-masked, parallel-group trial. A total enrollment of 84 is recorded, with 41 participants listed in the fascia-iliaca block arm and 43 in the local-injection arm for the posted primary outcome. The record does not state the allocation ratio or identify who was masked. It also does not explain how the random sequence was generated or concealed.

The fascia-iliaca block arm is described as receiving up to 60 mL of 0.35% ropivacaine at 3 mg/kg, together with 100 mcg clonidine per 60 mL and epinephrine at 1:400,000. The comparator arm description specifies 30cc of 0.5% Noropin injected locally in the hip joint. The brief summary describes randomization to a nerve block or no nerve block, with pain medicine only in the latter arm. Because these descriptions differ, the precise comparator should be interpreted from the detailed arm description with that record-level inconsistency in mind.

The primary outcome is Visual Analog Scale pain at 3 Months. The record gives the mean and a 95% confidence interval for each arm. It does not give a standard deviation or an adjusted treatment-effect estimate. The trial is marked completed; the recorded start is 2015-04 and primary completion is 2017-06. The sponsor is The Hawkins Foundation. Further details of sites, follow-up procedures, protocol deviations and the analysis population are not reported in the registry record.

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

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 Visual Analog Scale, measured over 3 Months.

The primary endpoint is pain measured with the Visual Analog Scale (VAS), reported in units on a scale at 3 Months. The registry describes the scale as ranging from 0-10, where 0 is no pain and 10 is the worst possible pain. A score is a numerical summary of a participant’s reported pain at the specified assessment; it is not, by itself, a measure of function, recovery or opioid use.

Pain scales are used in clinical research because they turn a subjective experience into a consistently recorded outcome that can be summarized across participants and compared between randomized groups. Reporting the mean describes the group’s average score. It does not show the full distribution: participants may have different scores, and the registry record does not provide those individual values or a measure of spread such as a standard deviation.

The endpoint’s timing matters. A 3-month score describes pain at that registered follow-up point, not pain immediately after surgery or throughout the entire recovery period. The record says pain and clinical outcomes were assessed through 3 months post-operatively, but further assessment schedules and the procedures used to collect VAS scores are not reported in the registry record.

The posted arm means are accompanied by 95% confidence intervals. Those intervals convey uncertainty around each arm’s mean under the statistical method used to form them. They are not a range containing every participant’s score, and they do not directly provide a confidence interval for the difference between arms.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The main statistical distinction in this record is between an arm-specific summary and a randomized comparison. The registry reports a mean VAS score for each arm. A treatment comparison would ordinarily summarize how far apart the arm outcomes are and quantify uncertainty around that contrast. The posted record does not report such an estimate for this continuous outcome; it states that values were missing or not estimable for a two-arm comparison. The arm summaries therefore should not be recast as a test of a treatment effect.

What does a mean summarize?

For a continuous outcome such as a pain score, the mean is the arithmetic average of recorded scores in a group. It gives a concise description of the group’s central level, but it does not describe how clustered or dispersed individual scores are. Two groups can have similar means while differing in their distributions, and the mean alone does not show whether scores were concentrated or widely spread. The registry gives no standard deviation or other direct summary of within-arm variability.

The primary outcome is reported at 3 Months, and the registry describes its scale as 0-10, with lower values corresponding to less pain according to the scale’s anchors. That direction helps readers understand what the measure represents, but it does not supply a clinical threshold for an important difference. Such a threshold is not reported in the registry record.

How should the confidence intervals be read?

A confidence interval expresses statistical uncertainty around an estimate, subject to the method and assumptions used to calculate it. The registry reports a 95% confidence interval for each arm mean: 1.91 to 3.38 for FI Block and 1.77 to 3.23 for Local Injection. In general, a confidence interval is not a range intended to contain most individual participants’ scores. It concerns uncertainty in the estimated group mean. A narrower interval generally indicates greater precision than a wider interval, but precision also depends on the estimand and method being considered.

These intervals are for the separate means. They cannot be treated as the interval for the difference between arms. The uncertainty in a difference depends on the comparison’s statistical model and the variability and relationship of the observations. Since the record does not give the comparison estimate, its confidence interval and test result, those quantities cannot be inferred from the arm intervals alone.

Why does randomization matter?

Random assignment is intended to make treatment groups comparable, on average, with respect to factors that could influence outcomes. It supports a causal comparison when the analysis follows an appropriate design and important sources of bias are controlled. It does not guarantee that groups will be identical, and it does not remove concerns about missing outcomes, deviations from assigned treatment, measurement or analysis choices. The registry identifies the trial as randomized but does not report the sequence-generation or concealment methods, or the analysis population.

Single masking means the record classifies the study as masked at one level, but it does not say which individuals were unaware of treatment assignment. That detail matters when considering the potential for expectations to influence care, outcome assessment or reporting, especially for a participant-reported pain scale. The identity of the masked party and the masking procedures are not reported in the registry record.

What does a planning illustration mean?

In general, sample-size planning asks how many participants would be needed under specified assumptions to detect a chosen effect with a chosen probability, while controlling a stated false-positive rate. The registry’s planning assumptions describe two-sided significance level 0.05, equal allocation, a normal approximation and an effect defined as a fraction of the observed effect. Such calculations are planning illustrations based on an observed effect; they are not evidence of the trial’s original design rationale and are not observed power. The record does not report the trial’s own sample-size justification. No planning result should be read as an observed trial outcome.

Planning calculations can be sensitive to the assumed effect size and variability. If an effect used for planning comes from the same trial’s observed data, it is an uncertain estimate, not a fixed truth. A planning illustration therefore cannot repair the absence of a reported comparative estimate or determine whether the trial was adequately powered. The registry record does not report its protocol assumptions, anticipated effect, variance assumption or design calculation.

Why can over-dispersion matter?

In general, over-dispersion occurs when variability in the data exceeds what a statistical model assumes. If a model underestimates variability, standard errors may be too small and confidence intervals too narrow, making statistical evidence appear more precise than it is. The relevance of over-dispersion depends on the outcome and model. For continuous VAS scores, the registry does not provide enough distributional detail or a model description to assess whether this issue was considered. This is a general statistical point, not a finding about this trial.

Other details needed to reproduce or appraise the analysis—such as whether the comparison was adjusted, how missing scores were handled, and whether assumptions were checked—are not reported in the registry record. The registered means and intervals should therefore be interpreted as the posted summaries, without attributing an unreported model or analysis plan to the investigators.

10. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when multiple outcomes, time points, treatment contrasts or subgroup analyses are tested. When many tests are conducted, the chance of obtaining at least one apparently notable result by chance can increase. In general, a statistical plan may identify a primary outcome and prespecify how multiple comparisons will be handled. The registry identifies Visual Analog Scale pain at 3 Months as the primary outcome and lists opioid consumption as a secondary outcome. It also records five outcome measures. A multiplicity adjustment or strategy is not reported in the registry record.

The registry lists zero analysis entries, and its note says values were missing or not estimable for a two-arm comparison of the continuous endpoint. A between-arm p-value, confidence interval for the contrast and model specification are therefore not reported. This does not mean that no analysis was performed outside the registry; it means the record does not post those analysis details.

Missing-data information is also limited. The arm counts associated with the primary outcome are given, but the record does not explain whether all enrolled participants completed the 3-month assessment, whether any scores were missing, or how missing outcomes were handled. Reasons for missingness, imputation methods and sensitivity analyses are not reported in the registry record.

The analysis population is not specified. The record does not say whether results were based on all randomized participants, participants who received the assigned intervention, or another defined group. It also does not report exclusions after randomization or protocol deviations. These omissions limit assessment of the analysis and make it inappropriate to assume an intention-to-treat or per-protocol approach.

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 registry reports serious adverse event counts by arm. For FI Block, 0 serious adverse events are listed among 41 at risk; for Local Injection, 0 are listed among 43 at risk. Deaths are recorded as 0 in both arms. The registry also lists 1 other adverse event in each arm. These figures are counts as recorded, not a complete description of what happened to each participant.

The terms and event descriptions for the other adverse events are not reported in the registry record. The record also does not give further details about how adverse events were collected, the observation period for safety, or how events were classified. A zero count for reported serious events means none are recorded in these fields; it does not prove that no adverse experience occurred or exclude uncommon risks.

These arm-specific counts do not establish that an intervention caused or prevented an event. The record does not report a comparative safety analysis or an assessment of event relatedness. Safety interpretation should remain descriptive and limited to the classifications and counts actually posted.

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

The registry results provide a snapshot of mean pain scores at 3 Months for the two randomized arms. FI Block has a posted mean of 2.65, with a 95% confidence interval from 1.91 to 3.38; Local Injection has a posted mean of 2.5, with a 95% confidence interval from 1.77 to 3.23. These summaries communicate the observed group means and uncertainty around those means. They do not provide the estimated difference between treatment assignments.

Without a reported between-arm estimate, confidence interval for the contrast or p-value, the posted results do not quantify the comparative effect or its statistical precision. They also do not establish that the approaches are equivalent. Similar-looking arm means or intervals are not a formal equivalence or non-inferiority analysis; no such design or margin is reported in the registry record.

The outcome concerns pain at one stated follow-up time. It does not by itself describe pain at other times, overall clinical recovery, function or opioid consumption. Although opioid consumption is listed as a secondary outcome, its result is not reported in the registry record. The record does not specify a threshold for a clinically important VAS difference, so the clinical importance of any contrast cannot be judged from the posted numbers alone.

The safety fields record no serious adverse events and no deaths in either arm, alongside one other adverse event in each. These counts are not proof that either intervention is free of risk, nor do they identify the nature or cause of the events. The trial’s enrollment and registry summaries also do not show whether every randomized participant completed follow-up.

In short, the record describes a randomized study and posts primary-outcome means by arm, but does not post the principal comparative analysis needed to support a precise statement about the difference in pain scores. Missing analysis, follow-up and methods details further constrain interpretation. These results should be read as registry summaries, not as medical advice or a stand-alone basis for choosing care.

13. Why This Trial Matters Statistically

This trial illustrates an important distinction in clinical statistics: reporting outcomes separately by group is not the same as reporting a comparison between groups. Randomization makes the between-arm contrast the central quantity for assessing an intervention. Arm means are useful descriptions, but without a contrast estimate and its uncertainty, readers cannot tell how precisely the trial estimated the comparative outcome.

The example also shows why outcome timing and measurement scale should be made explicit. A VAS score at 3 Months is a specific summary of reported pain at a defined follow-up, on a scale with stated anchors. It is not interchangeable with immediate postoperative pain or with other outcomes such as opioid consumption. The registry’s listed secondary outcome underlines that different outcomes answer different questions.

Confidence intervals are valuable, but their target must be clear. Intervals around each mean describe uncertainty in each mean, not directly the uncertainty in a difference. Readers who interpret arm-level intervals as a formal comparison may overstate what the analysis shows. A clearly posted contrast, with its interval and analysis details, would make the comparative evidence easier to assess.

Finally, transparent reporting of masking, missing outcomes, analysis populations and multiplicity helps readers evaluate potential sources of bias and uncertainty. These items are not reported in the registry record. Their absence does not establish that the trial lacked procedures for addressing them, but it limits what can be concluded from the registry information alone.

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 main limitation for interpretation is that the registry posts arm-specific primary-outcome means and confidence intervals but no estimated between-arm contrast, p-value or confidence interval for the contrast. The record explicitly notes that values were missing or not estimable for a two-arm comparison of the continuous outcome. As a result, comparative precision cannot be assessed from the posted results.

The arm descriptions are not fully aligned with the brief summary. The detailed comparator description specifies local anesthetic injected in the hip joint, while the brief summary describes no nerve block and pain medicine only. This makes the comparator’s characterization less clear than it would be with consistent wording.

Important analysis details are not reported in the registry record: the statistical model, adjustment for baseline characteristics, analysis population, handling of missing outcomes, and treatment of multiple outcomes. The identity of the masked party and the randomization procedures are also not reported. The record does not give the VAS score distribution or a standard deviation, and it provides no participant-level results.

Safety information is limited to event counts. Descriptions of the other adverse events, collection methods, observation period and relatedness assessments are not reported. The listed primary-outcome counts should not be treated as confirmation that all enrolled participants completed follow-up, since the completion and missing-data details are not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Hip Scope Fascia-iliaca (FI) Block Study — NCT02365961.
• Registry record last updated 2019-03-14; status last verified 2019-02.
• Results first posted 2019-03-14.
• 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

The record describes NCT02365961, Hip Scope Fascia-iliaca (FI) Block Study, a Phase 4 randomized, single-masked, parallel trial sponsored by The Hawkins Foundation. It is marked completed, with a recorded start of 2015-04 and primary completion of 2017-06. Enrollment is listed as 84.

The primary outcome is mean Visual Analog Scale pain at 3 Months, on a scale from 0-10. The posted means are 2.65 for FI Block and 2.5 for Local Injection, each with a 95% confidence interval. No comparative estimate is posted. Opioid consumption is listed as a secondary outcome, but its result is not reported in the registry record.