This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Posterior Capsular Injection With Femoral Nerve Block for Total Knee Arthroplasty (NCT02701296), a randomized na study. The primary outcome is Pain Intensity.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02701296 |
| Phase | NA |
| Condition | Posterior Knee Infiltration |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 80 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Trinity Health Of New England |
| Results posted | Yes |
2. Clinical Question
Population
The registry describes patients following total knee arthroplasty. It lists an enrollment of 80, but does not report further eligibility details or describe the characteristics of the people enrolled. The specific population contributing to the primary-outcome analysis is not reported in the registry record.
Intervention
One group received continuous femoral nerve block combined with ultrasound-guided posterior capsular injection of ropivacaine with epinephrine. The registry identifies this arm as Posterior Capsular Injection.
Comparator
The other group received continuous femoral nerve block combined with ultrasound selective tibial nerve block of ropivacaine. The registry identifies this arm as Tibial Nerve Block. Both strategies therefore include continuous femoral nerve block; the additional technique differs.
Primary question
The primary outcome is pain intensity measured using a self-reported Numeric Pain Rating Scale (NPRS). The registry describes assessments in the Post Anesthesia Care Unit (PACU) and every 6 hours for 48 hours post surgery. The clinical question is whether the reported pain scores differ between the two approaches during that assessment period. The registry record does not report numerical scores or an analysis answering that comparison.
These details define the comparison, not its result. The record also lists opioid consumption and measures of movement or sensation in nerve distributions as secondary outcomes. Whether either technique produced lower pain scores, or how precisely any difference was estimated, cannot be determined from the registry information reported for the primary endpoint.
3. Trial Design
The registry describes a randomized, double-masked, parallel-group trial. Randomization means that assignment to the two strategies was intended to be determined by chance rather than by a clinician selecting a technique for each patient. A parallel design means the compared groups receive their respective strategies during the same trial rather than crossing over between them. These design labels do not, on their own, establish how assignments were generated, concealed, or implemented.
The trial compares continuous femoral nerve block combined with ultrasound-guided posterior capsular injection against continuous femoral nerve block combined with ultrasound selective tibial nerve block. The arm descriptions specify ropivacaine with epinephrine for the posterior capsular injection and ropivacaine for the tibial nerve block. The record does not explain the practical details of the continuous femoral nerve block or give the doses, timing, or administration schedule for the additional techniques.
Enrollment is listed as 80. The registry status is Completed. The recorded start date is 2011-11-07, and the primary completion date is 2014-08-31. These registry fields do not establish the number included in each outcome analysis. The adverse-event entries list separate at-risk counts for the two arms, but those figures should not be treated as the analyzed sample sizes for pain outcomes.
The phase is listed as NA. The sponsor is Trinity Health Of New England. Further information about eligibility criteria, recruitment, study locations, masking procedures, allocation concealment, protocol deviations, and the final analysis population is not reported in the registry record. The record also does not describe a planned sample-size justification or a 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
| Stage | Posterior Capsular Injection | Tibial Nerve Block |
|---|---|---|
| STARTED | 42 | 38 |
| COMPLETED | 42 | 36 |
| NOT COMPLETED | 0 | 2 |
Reasons for not completing this period:
| Reason | Posterior Capsular Injection | Tibial Nerve Block |
|---|---|---|
| Incomplete Data | 0 | 2 |
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.
| Characteristic | Unit | Posterior Capsular Injection | Tibial Nerve Block | Total |
|---|---|---|---|---|
| Participants analysed | 42 | 36 | 78 | |
| Age, Continuous | Years | 65.9 (SD 8.0) | 63.5 (SD 8.9) | 64.8 (SD 8.43) |
| Sex: Female, Male: Female | Participants | 24 | 19 | 43 |
| Sex: Female, Male: Male | Participants | 18 | 17 | 35 |
| Region of Enrollment: United States | participants | 42 | 36 | 78 |
6. Primary Endpoint
The registry lists the primary outcome as Pain Intensity, measured over 48 hours post surgery.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | pain score |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is pain intensity, expressed as the mean Numeric Pain Rating Scale (NPRS) score. The registry describes an 11-point scale, with 0 meaning no pain and 10 meaning the worst possible pain. Patients self-report their pain. Assessments are described in the Post Anesthesia Care Unit (PACU) and every 6 hours for 48 hours post surgery.
A pain rating is a direct report of the experience the trial aims to assess. Using the same stated scale across the two randomized groups gives a common outcome for comparison. Reporting a mean describes the average score, while the stated standard deviation describes how much individual scores vary around that average. These are general interpretations of the statistics named in the registry; numerical means and standard deviations for this trial are not reported in the registry record.
The repeated assessment schedule matters to interpretation. Scores at different times describe different moments in recovery, and a group difference at one assessment would not automatically establish a difference at another. An overall summary across assessments would require a specified method for combining or modeling those observations. The registry description names multiple assessment times but does not identify a single summary time point or provide a numerical comparison. It therefore does not establish the size, direction, or precision of a primary-outcome difference.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies the comparison and the intended primary measure, but it does not report pain-score estimates for either arm. It also gives no between-group effect estimate, confidence interval, or p-value for pain intensity. As a result, the posted registry information does not establish whether the groups had different mean NPRS scores, the direction of any difference, or how precisely a difference was estimated.
This absence is especially important because the primary outcome is described at multiple times: in the PACU and every 6 hours for 48 hours after surgery. A result at an individual assessment time would answer a time-specific question. A summary across time would answer a different question and would depend on how the repeated scores were handled. The registry record states that the primary outcome has several categories or time points and was not reduced to one comparison. There is therefore no single primary comparison to interpret from the outcome details available.
In general, an effect estimate describes the magnitude and direction of a group contrast, while a confidence interval describes the range of values compatible with the data and the analysis assumptions. A p-value addresses compatibility with a specified null hypothesis under those assumptions; it does not measure clinical importance or the probability that a treatment is effective. None of these quantities for the primary pain comparison is reported in the registry record, so no conclusion about statistical significance or precision can be drawn.
The trial is labeled randomized and double-masked, features that can help limit some biases when carried out successfully. The registry fields alone do not explain how randomization or masking was implemented, whether masking remained intact, or how missing observations and protocol deviations were handled. These details matter when judging whether a reported contrast would reflect the assigned strategies. They are not reported in the registry record.
The record lists opioid consumption and sensory or motor assessments as secondary outcomes. It does not report numerical findings for those measures or analyses linking them to pain scores. No inference about those outcomes should be made from the primary-outcome description or from the safety entries. Overall, the registry information describes what the trial set out to compare, but does not supply the outcome estimates needed to quantify that comparison.
9. Statistical Methods Explained
What does the trial design tell the reader?
The registry classifies the study as randomized, double-masked, and parallel. In general, random allocation is intended to make the comparison less dependent on baseline differences that influence treatment selection. Masking is intended to reduce the influence of expectations on care or outcome assessment. A parallel design compares groups assigned to different approaches over the trial period. These are design concepts, not proof that allocation and masking were implemented without problems. The specific procedures are not reported in the registry record.
The comparison has an active approach in each arm: continuous femoral nerve block is combined with one of two additional techniques. Thus, the clinical contrast is between the combined strategies described, not between receiving a nerve block and receiving no nerve block. The arm descriptions specify ultrasound-guided posterior capsular injection of ropivacaine with epinephrine or ultrasound selective tibial nerve block of ropivacaine. Doses and additional treatment details are not reported in the registry record.
What does a mean and standard deviation describe?
The primary measure is identified as a mean of a continuous measure, with standard deviation as the dispersion statistic. In general, a mean summarizes the average score across observations, and a standard deviation describes the spread of scores around that mean. The mean alone does not show whether scores are tightly clustered or widely dispersed. The standard deviation is not the same as a confidence interval: the former describes variability among observations, whereas the latter expresses uncertainty about an estimated quantity under an analysis method.
The NPRS is described as an 11-point self-reported scale running from 0, no pain, to 10, the worst possible. The registry describes repeated assessments from PACU through 48 hours post surgery. Repeated ratings from the same person are generally related rather than independent. In general, an analysis that treats all observations as independent may fail to account for that relationship; methods for repeated measures can model the correlation or define a patient-level summary. The registry record does not state which, if any, approach was used.
How should a group comparison be interpreted?
In general, a comparison of group means can be expressed as a difference in average scores, with the direction depending on which group is subtracted from which. A confidence interval around that contrast communicates uncertainty and helps show which effect sizes remain compatible with the data and assumptions. The interval does not guarantee that the true effect lies within its endpoints. A p-value, when reported, addresses the compatibility of the observations with a null hypothesis under a specified model; it does not indicate the size or importance of an effect.
No group means, standard deviations, contrast estimate, confidence interval, or p-value for the primary outcome is reported in the registry record. The primary outcome is also not reduced to one comparison because it has several time points. The record does not name a model, contrast, or time point as the primary analytic target. It would therefore be inappropriate to attribute a particular statistical test or result to this trial.
Why can variability and model assumptions matter?
As a general statistical point, greater variability makes it harder to estimate a group contrast precisely. If observations are more dispersed than a chosen model expects, uncertainty estimates can be too narrow unless the analysis accounts for that extra variability. This issue is often called over-dispersion in settings where a model assumes less variability than the data exhibit. It is a general consideration, not a reported feature of this trial: the registry record does not provide the outcome data or identify over-dispersion as an issue.
Repeated assessments also raise questions about correlation, timing, and incomplete follow-up. A model can represent the relationship between scores from the same participant, while a summary score can reduce repeated observations to a single value. Either choice answers a particular analytic question and has assumptions. Which approach is appropriate depends on the estimand, data structure, and analysis plan. These choices are not described in the registry record.
What do the planning assumptions mean?
The registry's sample-size assumptions describe planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. For non-time-to-event outcomes, the illustrations are expressed as participants per arm for 80% power or another stated power; time-to-event illustrations use a total number of events. These are planning illustrations, not observed power and not evidence that the original trial was designed using those assumptions.
The outcome effect and numerical planning results needed to assess such illustrations are not reported in the registry record. The record also does not report the trial's own sample-size justification. A planning calculation cannot replace observed estimates, and it does not show what the trial found. The distinction is particularly relevant when the primary outcome is measured repeatedly and no single comparison is specified.
10. Multiplicity, Missing Data and Analysis Populations
The primary pain measure is described at more than one assessment time: in PACU and every 6 hours for 48 hours post surgery. The registry identifies the primary outcome as having several categories or time points and does not reduce it to one comparison. It does not report a prespecified primary time point, an overall repeated-measures contrast, or a method for controlling multiplicity. When several tests or time points are examined, the chance of at least one apparently unusual result can increase; in general, a prespecified analysis strategy helps clarify how such comparisons should be interpreted. No multiplicity procedure is reported in the registry record.
The registry lists six outcome measures and names opioid consumption, plantar flexion in the tibial nerve distribution, cold sensation in the tibial nerve distribution, dorsiflexion in the peroneal nerve distribution, and sensation in the peroneal nerve distribution as secondary outcomes. It reports 0 analyses. No numerical outcome estimates or analysis results are reported in the registry record, so the extent to which those outcomes were measured, analyzed, or reported cannot be established from this record.
Missing-data handling is not reported in the registry record. The record does not state how many pain assessments were missing, why observations might have been unavailable, whether any imputation or model-based method was used, or whether analyses included all randomized participants. The population contributing to each outcome analysis is also not reported. These omissions limit assessment of bias and precision: incomplete observations can affect both an estimate and its uncertainty, depending on why data are missing and how the analysis handles them.
The registry's enrollment field lists 80, but that field does not establish the analysis denominator for pain scores. The safety entries use their own at-risk counts. No analysis population, exclusions, or deviations from an intended analysis are reported in the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Posterior Capsular Injection | 0 | 42 | 0.0% |
| Tibial Nerve Block | 0 | 36 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Posterior Capsular Injection | 0 of 42 |
| Tibial Nerve Block | 0 of 36 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Posterior Capsular Injection | 0 of 42 |
| Tibial Nerve Block | 0 of 36 |
The adverse-event entries report 0 serious adverse events among 42 at risk in the Posterior Capsular Injection group and 0 among 36 at risk in the Tibial Nerve Block group. They also report 0 other adverse events in each listed group and 0 deaths in each group. These are the registry's recorded figures for the listed categories; they should not be confused with the sample sizes used for the primary pain analysis.
A zero count means that no event in the specified category is recorded for the stated at-risk group. It does not establish that the true risk is zero, and it does not show that the strategies have identical safety. Rare events may not appear in a trial, and the interpretation depends on how events were defined, sought, and followed. The registry record does not provide adverse-event definitions, ascertainment procedures, follow-up details, or a comparative safety analysis.
The two group entries should be read separately as reported. They do not establish a risk difference or a confidence interval, neither of which is reported in the registry record. The figures also do not provide information about severity or timing beyond the listed serious, other, and death categories.
12. What the Result Does, and Does Not, Mean
The registry record is informative about the question the trial was designed to address: pain after total knee arthroplasty under two combined nerve-block approaches. It identifies the randomized, double-masked, parallel design, describes the intervention arms, and specifies repeated self-reported NPRS assessments through 48 hours post surgery. It also lists secondary measures related to opioid consumption and motor or sensory function.
That information does not answer which approach had lower average pain scores. Numerical outcome estimates, a between-group comparison, uncertainty intervals, and p-values for pain are not reported in the registry record. The record also does not identify a single summary comparison across the multiple assessment times. Accordingly, it does not support a conclusion about the direction, magnitude, precision, or statistical significance of a primary-outcome difference.
Nor does the registry information establish that the two approaches are equivalent. A lack of reported results is not evidence of no difference. Equivalence or non-inferiority requires a defined margin and an analysis designed to evaluate it; neither is reported in the registry record. Likewise, the trial's completion status and listed enrollment do not establish how many participants contributed to a particular outcome or whether the planned analyses were completed.
The adverse-event entries record zero events in the categories shown for the listed at-risk groups, but those entries do not demonstrate zero underlying risk or a comparative safety advantage. The record does not describe event definitions or the completeness of safety follow-up. The responsible interpretation is therefore limited to what is documented: the study compared two specified strategies, and the available registry entries do not report numerical primary-outcome findings or a comparative analysis.
These limitations concern the information in the registry record, not necessarily the full study record. They do not imply that no other analyses or reports exist; such information is simply not reported in the registry record.
13. Why This Trial Matters Statistically
This trial is statistically interesting because it compares two active, combined approaches while holding continuous femoral nerve block in common. That structure makes the target contrast clinically specific: the additional posterior capsular injection strategy is compared with the selective tibial nerve block strategy. It is not a comparison of nerve block against no nerve block, and conclusions would apply to the combined strategies as studied rather than automatically to each component on its own.
The pain endpoint is measured repeatedly rather than at one stated time alone. Repeated measurements can describe how scores vary over the postoperative period, but they also require a clear analysis target. An individual time point, an average over time, and a modeled pattern of change are different questions. The registry record does not specify one primary summary comparison, illustrating why endpoint definition and analysis plans matter before results are interpreted.
The registry also makes the distinction between trial conduct and outcome reporting important. Randomization and masking are meaningful design labels, but numerical estimates and details of implementation are needed to assess the evidence. Enrollment is listed as 80, while the registry reports 0 analyses and no numerical primary-outcome results. The listed adverse-event counts answer only a limited descriptive question and cannot substitute for an efficacy analysis.
In general, clear reporting of the analysis population, outcome timing, effect estimate, and uncertainty allows readers to judge both the size and precision of a comparison. In this record, those elements are not reported for the primary pain outcome. The statistical importance of the trial is therefore mainly in the structure of its question and the need for a prespecified, transparent way to summarize repeated pain assessments—not in a numerical treatment-effect conclusion that the registry record does not provide.
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.
Important details for interpreting this particular comparison are not reported in the registry record. Eligibility criteria and participant characteristics are absent, so the population represented by the trial cannot be described beyond patients following total knee arthroplasty. The registry lists an enrollment of 80, but it does not report the number included in the primary-outcome analysis or at each assessment time.
The outcome description gives a schedule extending from PACU through 48 hours post surgery, but the record does not define a single primary comparison across those times. It also does not give means, standard deviations, effect estimates, confidence intervals, or p-values. This prevents assessment of both the direction and precision of the pain comparison. The record reports 0 analyses, and the handling of repeated observations is not stated.
Further details about the intervention regimens are not reported, including doses, timing, and administration procedures beyond the arm descriptions. The procedures used for randomization and masking are not described. The registry also does not report protocol deviations, missing-data methods, analysis populations, or a trial-specific sample-size justification. Thus, the design labels cannot resolve questions about implementation or analysis.
The safety entries lack event definitions, ascertainment details, and follow-up information. Their zero counts are limited to the listed categories and at-risk groups and do not permit a precise comparative safety estimate. Secondary outcomes are named, but their numerical results and analyses are not reported in the registry record. These trial-specific gaps mean that the registry entry describes the study question and design more fully than it documents its outcome evidence.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Posterior Capsular Injection With Femoral Nerve Block for Total Knee Arthroplasty — NCT02701296.
- Registry record last updated 2018-10-03; status last verified 2018-10.
- Results first posted 2017-06-14.
- 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.
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18. Record Summary
NCT02701296 is a completed randomized, double-masked, parallel-group trial sponsored by Trinity Health Of New England. It compares continuous femoral nerve block combined with ultrasound-guided posterior capsular injection of ropivacaine with epinephrine against continuous femoral nerve block combined with ultrasound selective tibial nerve block of ropivacaine. Enrollment is listed as 80; the phase is listed as NA.
The primary outcome is mean self-reported NPRS pain intensity, assessed in PACU and every 6 hours for 48 hours post surgery. Opioid consumption and motor or sensory measures are listed as secondary outcomes. The registry record reports 0 analyses and does not give numerical primary-outcome results or a single comparison across assessment times.
For adverse events, the record lists 0 serious events, 0 other events, and 0 deaths in each arm, using the separately stated at-risk counts. Further outcome, analysis, missing-data, and safety-ascertainment details are not reported in the registry record.