Peripheral Nerve Blocks for Above-the-knee Amputations: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Peripheral Nerve Blocks for Above-the-knee Amputations (NCT03404180), a na phase 4 study. The primary outcome is Peripheral Nerve Block Success as a Primary Anesthetic.

2. Clinical Question

3. Trial Design

This is a Phase 4, completed, single-group study sponsored by the University of Florida. The registry record lists enrollment of 30 and dates the study start to 2018-02-09, with primary completion on 2024-12-18. Allocation is recorded as NA, and masking is recorded as none. The study is not a randomized comparison and does not include a like-for-like control group.

The intervention is peripheral nerve block as a primary anesthetic for above-the-knee amputation. The arm description specifies intravenous sedation with propofol or dexmedetomidine and ultrasound-guided femoral and sciatic nerve blocks. The registry also lists lateral femoral cutaneous and obturator nerve blocks among interventions. The record does not provide enough arm-description detail to establish how those additional listed blocks were used.

The registry summary presents the study as an evaluation of the approach in a high-risk clinical context, mentioning peripheral vascular disease, diabetes, hypertension, coronary artery disease, and chronic obstructive pulmonary disease. These conditions describe the stated motivation; they do not establish that every participant had any particular condition. Participant eligibility criteria and detailed baseline characteristics are not reported in the registry record.

A single-group design can describe outcomes among participants treated with the study approach. It cannot, by itself, separate the effect of that approach from other factors or estimate a controlled difference against another anesthetic strategy. The registry record does not report a protocol-level statistical plan, sample-size justification, or details of outcome adjudication. Its listed completion status does not fill in those missing design and analysis details.

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 Peripheral Nerve Block Success as a Primary Anesthetic, measured over Intraoperative period (typically one to three hours).

The primary endpoint is titled Peripheral Nerve Block Success as a Primary Anesthetic. Its unit is participants, and its measure is a count of participants. The stated assessment period is the intraoperative period, typically one to three hours. This endpoint is intended to capture whether the nerve-block approach serves as the primary anesthetic during the operation, rather than measuring a continuous quantity such as pain intensity.

A participant count can be useful for describing how often a defined procedural or anesthetic objective was achieved in the studied group. However, the registry record does not state the operational definition of success, what events would constitute failure, or how any transition to another anesthetic would be classified. It also does not report the observed endpoint count. Consequently, the endpoint’s meaning can be described from its title and measurement fields, but its result and the precise rule used to determine success are not reported in the registry record.

Without a reported endpoint result, the available information does not establish how many participants had successful blocks as the primary anesthetic. Nor does the endpoint alone provide a comparison with another anesthetic strategy; the study has a single group and no concurrent control arm.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count represent?

General statistical explanation: a count records how many participants meet an outcome definition. For a binary outcome such as success or no success, each participant is classified according to the chosen rule, and the count of participants classified as having the event is one summary of the group. To interpret the count fully, readers also need the relevant denominator and a clear definition of the event. A count alone does not explain how the outcome was classified or how precise the underlying estimate may be.

For this study, the primary measure is the count of participants with peripheral nerve block success as a primary anesthetic. The timeframe is the intraoperative period, typically one to three hours. The registry record does not report the observed count or specify the classification criteria. Although enrollment is listed as 30, the number included in the primary endpoint analysis is not reported in the registry record. Thus, a primary-outcome proportion or uncertainty interval cannot be read from the posted information.

What can a single-group study estimate?

General statistical explanation: a single-group study can describe what was observed among participants receiving the study intervention. A comparison between treatment strategies usually requires information from both strategies and a design that supports a meaningful contrast. In a randomized comparison, random assignment is intended to make the groups comparable, on average, with respect to both measured and unmeasured factors. This study has no separate control group and is not a randomized comparison, so it does not provide that type of controlled contrast.

The registry summary mentions general anesthesia and opioid therapy to frame the question, but the design fields identify a single group. Those references should not be interpreted as evidence that participants receiving those approaches were enrolled as controls. Any descriptive outcome from the study would need to be understood as applying to the study group, subject to the endpoint definition and the available participant data.

What do confidence intervals and tests add?

General statistical explanation: a confidence interval expresses uncertainty around an estimate under the assumptions of the statistical method used. A narrower interval indicates greater precision under those assumptions; a wider interval indicates less precision. A hypothesis test evaluates compatibility between data and a specified statistical model or null hypothesis. Neither a confidence interval nor a p-value establishes clinical importance on its own, and neither corrects design limitations such as the absence of a control group.

The registry record lists no analyses and reports no confidence interval, p-value, or primary endpoint result. It is therefore not possible to assess the precision of the primary outcome or interpret a hypothesis test. This is not a case where a reported non-significant finding can be distinguished from an imprecise estimate: no such finding is reported in the registry record.

How should planning illustrations be read?

General statistical explanation: sample-size calculations are planning tools. They describe the amount of information that a hypothetical design would require under stated assumptions; they are not observed outcomes and do not show the probability that a completed study has reached a conclusion. Calculations based on an observed effect are especially dependent on that effect estimate and should not be mistaken for the original trial’s design rationale.

The registry’s planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. It also distinguishes calculations expressed as total events for time-to-event outcomes using the Schoenfeld method from calculations expressed as participants per arm for other outcomes. These are planning assumptions, not evidence that this single-group trial enrolled two arms or used those assumptions in its original design. The trial’s own sample-size justification is not reported in the registry record. No numerical planning outputs are stated in the information available for this explanation.

Why do definitions and analysis populations matter?

General statistical explanation: a clear outcome definition makes it possible to determine whether participants were classified consistently. A prespecified analysis population clarifies which participants contribute to an estimate. Missing-outcome handling matters because excluding participants with unknown outcomes can alter the interpretation of a count, especially if missingness is related to participant condition or outcome. These choices should be described rather than inferred from enrollment alone.

For this study, the detailed success criteria, endpoint-specific denominator, missing-data approach, and analysis population are not reported in the registry record. The statistical analysis plan, including any adjustment or interim analysis, is also not reported in the registry record. Without these details, the endpoint can be identified by name and timeframe, but the analysis methods used to produce a result cannot be evaluated.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Peripheral Nerve Block")
n      <- c(30)
events <- c(1)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Peripheral Nerve Block  30  1  3.3  0.1  17.2  0.6  16.7  0.8  16.7

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists two outcome measures and identifies mortality as a secondary outcome. It lists no analyses. It does not report whether there were additional outcome comparisons, whether any outcomes were designated for formal hypothesis testing, or whether the analysis plan addressed multiplicity. Multiplicity refers, in general, to the interpretive issue that can arise when multiple outcomes or statistical tests are considered: the chance of at least one apparently notable result may depend on the number and arrangement of tests. The record does not provide enough information to assess that issue for this study.

Missing-data methods and endpoint-specific analysis populations are not reported in the registry record. The enrollment figure of 30 does not establish that all participants contributed data to every outcome. The record does not state whether outcome observations were incomplete, how any incomplete observations were handled, or whether analyses used all enrolled participants or another defined group.

Interim analyses, stopping criteria, and a detailed statistical analysis plan are also not reported in the registry record. Their absence from the record cannot be taken as evidence that a particular approach was or was not used. Because the primary outcome result and analysis are not posted, readers cannot assess multiplicity adjustment, missing-data sensitivity, or the robustness of the endpoint analysis.

12. 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 lists one group, Peripheral Nerve Block, with 30 participants at risk for serious adverse events and zero affected. It also lists 30 participants at risk for other adverse events and zero affected. The record separately lists one death. These are the safety figures recorded for the group; they do not provide a detailed event narrative.

The figures should be read as registry counts, not as proof that the intervention caused or prevented an event. The record does not report the timing or cause of the death, whether it was considered related to the intervention, or how it was classified in relation to the adverse-event categories. It does not provide participant-level follow-up duration or a comparative safety group. The listed mortality secondary outcome has no analysis reported in the registry record.

Zero affected in the adverse-event fields means no affected participants are listed for those categories in the posted safety record. It does not establish that no events occurred outside the recorded categories or observation period, and it does not quantify comparative risk. Without a control group and fuller event details, the safety entries are descriptive rather than a causal comparison.

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

The registry record establishes that a completed, single-group study evaluated peripheral nerve blocks as a primary anesthetic for above-the-knee amputations. It describes the primary outcome as the number of participants with successful peripheral nerve blocks as the primary anesthetic during the intraoperative period, typically one to three hours. It also records enrollment of 30 and lists a safety group with no participants affected by serious or other adverse events, alongside one death.

The record does not report the primary outcome count, a mortality analysis, or statistical analyses. It therefore does not establish how often the primary anesthetic objective was achieved or how precisely any outcome was estimated. The absence of a posted endpoint result must not be interpreted as a zero result, a favorable result, or an unfavorable result.

The single-group design does not provide a concurrent control comparison. Consequently, the record cannot estimate a controlled difference between peripheral nerve blocks and general anesthesia, opioid therapy, or another anesthetic approach. The summary’s description of the motivation for considering nerve blocks is not itself evidence of a comparative outcome.

These limits do not erase the descriptive purpose of the study. A well-defined result from a single group could inform understanding of the experience observed in that group. Here, however, the operational definition and result for the primary endpoint are not reported in the registry record. The available information supports a description of the design, intended endpoint, and posted safety counts, but not a conclusion about comparative effectiveness, causal effects, or the precision of the primary outcome.

14. Why This Trial Matters Statistically

This study raises a statistically important distinction between an intervention being evaluated and an intervention being compared. Peripheral nerve blocks are evaluated as the primary anesthetic in a single group. The registry summary frames the question in relation to general anesthesia and opioid therapy, but those approaches are not described as control arms. Keeping that distinction clear prevents a descriptive study from being read as a randomized or controlled comparison.

The primary endpoint is a participant count, a form of outcome that depends on a consistent definition of success and a clear denominator. The registry record supplies the endpoint title and timeframe but does not report the outcome count, success criteria, or analysis population. This illustrates why outcome labels alone are not enough for statistical interpretation: a reader needs both the observed data and the rules by which those data were classified.

The study also illustrates the separation between safety counts and a complete safety analysis. The registry records zero participants affected in the serious and other adverse-event categories and lists one death, but does not give timing, cause, relatedness, or comparative information. Those figures can be described as posted, while their causal meaning remains undetermined.

Finally, planning assumptions should not be confused with the original design or with evidence from the completed study. The listed sample-size approach describes hypothetical two-arm planning assumptions, whereas the trial design is single-group. The trial’s own sample-size justification is not reported in the registry record. Recognizing that mismatch helps readers distinguish a planning illustration from an observed result and from a protocol-level rationale.

15. 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 primary endpoint result is not reported in the registry record. The outcome title indicates that success as the primary anesthetic was measured as a participant count, but the definition of success and the endpoint-specific denominator are also not reported. These omissions prevent interpretation of the primary result and its precision.

The single-group design has no concurrent control group. The study therefore cannot provide a randomized or controlled estimate of the difference between peripheral nerve blocks and another anesthetic approach. The registry summary’s mention of general anesthesia and opioid therapy is background context, not a control-arm description.

Participant eligibility criteria and detailed baseline characteristics are not reported in the registry record. Although the summary names conditions relevant to the high-risk population motivating the study, it does not show which conditions were present among enrolled participants. The record also does not provide detailed information about the use of all listed nerve blocks or further procedural details beyond those stated in the arm description.

The record lists safety counts but does not report event timing, cause, relatedness, follow-up detail, or a mortality analysis. It also does not report missing-data methods, the analysis population, multiplicity handling, interim analyses, or a detailed statistical analysis plan. These are limitations of what can be evaluated from the posted registry information; they should not be treated as proof that a particular method was or was not used.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Peripheral Nerve Blocks for Above-the-knee Amputations — NCT03404180.
• Registry record last updated 2026-01-08; status last verified 2025-08.
• Results first posted 2026-01-08.
• 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.

19. Record Summary

NCT03404180 is a completed Phase 4, single-group study sponsored by the University of Florida, with enrollment listed as 30. The registry record gives a study start date of 2018-02-09 and primary completion date of 2024-12-18. The intervention evaluates peripheral nerve blocks as a primary anesthetic for above-the-knee amputations, with intravenous sedation described using propofol or dexmedetomidine and ultrasound-guided femoral and sciatic nerve blocks.

The primary outcome is the participant count for peripheral nerve block success as a primary anesthetic during the intraoperative period, typically one to three hours. Its result and detailed success definition are not reported in the registry record. No analyses are listed. Safety entries list zero participants affected by serious adverse events and zero affected by other adverse events among 30 at risk in each category, and one death; further event details and a mortality analysis are not reported.