Previously Implanted Pudendal Nerve Stimulation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Previously Implanted Pudendal Nerve Stimulation (NCT04473469), a na na study. The primary outcome is Evoked Bladder Contractions of at Least 20 Centimeters of Water (cmH2O) During Cystometrogram.

2. Clinical Question

The clinical question is exploratory and focused on an immediate measured bladder response during stimulation in people who already had an implanted neurostimulator. It is not framed as a comparison of stimulation against no stimulation in otherwise similar groups. Nor does the registry record define a clinical benefit threshold beyond the primary endpoint's stated contraction pressure threshold. The secondary outcomes concern selective stimulation of pudendal nerve branches and measurement of the effect of selective pudendal nerve stimulation on urethral leak point pressure. Their results are not reported in the registry record.

3. Trial Design

This was a completed, single-group study sponsored by the University of Michigan. The registry lists enrollment of 5 participants and identifies urinary retention and underactive bladder as conditions of interest. The study began on 2021-01-19, reached primary completion on 2023-05-02, and has completed status. These dates describe the registry record; they do not supply details about how long any participant was observed.

The study used a Medtronic Interstim II Model 3058 Neurostimulator, a device already implanted in the participants. The cystometrogram description states that the bladder would be filled to different volumes and electrical stimulation applied to the pudendal nerve through the implanted neurostimulator. The brief summary says the study sought to examine bladder response to different pudendal nerve stimulation frequencies. The specific stimulation settings, sequence, and duration are not reported in the registry record.

Masking is listed as none, allocation as not applicable, and the model as single-group. No control arm or randomized allocation is described, so the design does not support a like-for-like comparison between separately assigned groups. The study phase is listed as not applicable. Further operational details, including the eligibility criteria, recruitment approach, visit schedule beyond the primary outcome timeframe, and handling of participants who did not complete testing, are not reported in the registry record.

The primary outcome is a participant count: the number who experienced an evoked bladder contraction of at least 20 centimeters of water during stimulation. Its timeframe is Visit 1, approximately 1 week after consent. The registry lists three outcome measures, including secondary outcomes on selective stimulation of pudendal nerve branches and urethral leak point pressure. It does not report results for those outcomes. A trial-specific sample-size justification and detailed statistical analysis plan 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 Evoked Bladder Contractions of at Least 20 Centimeters of Water (cmH2O) During Cystometrogram, measured over Visit 1, approximately 1 week after consent.

The primary endpoint counts participants who experienced an evoked bladder contraction of at least 20 centimeters of water during pudendal nerve stimulation. The registry describes the contraction as evoked by stimulation through the participant's implanted stimulator. The outcome is recorded in participants and is assessed during the cystometrogram at Visit 1, approximately 1 week after consent.

This endpoint is used to describe whether a specified bladder response occurred during the test. A threshold-based count can make the outcome concrete: participants are classified according to whether the measured contraction reaches the stated pressure threshold, and the endpoint is the number meeting that criterion. It does not, by itself, describe the full range of measured pressures or how response varied across bladder volumes or stimulation settings. Those details are not reported in the registry record.

As a general statistical point, a participant count is an event count rather than a measurement of average response magnitude. The count can be informative about how many participants met the endpoint definition, while leaving other questions unanswered, such as the size and variability of responses among participants. The registry record does not report the observed primary count, so the endpoint definition is available but its observed result cannot be interpreted from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a single-group study and lists no randomized allocation. These features matter because the statistical question is not a comparison of outcomes between assigned groups. The primary endpoint is a count of participants meeting a specified response definition. The record lists no statistical analyses, and a trial-specific analysis plan is not reported in the registry record.

What does a participant count represent?

The primary measure is the number of participants with an evoked bladder contraction reaching at least 20 centimeters of water during stimulation. This is a binary outcome at the participant level: a participant either meets the stated threshold or does not. The count aggregates those classifications. It does not retain the full pressure value for each participant, so it cannot describe how far responses were above or below the threshold. Individual measurements and the observed count are not reported in the registry record.

As a general statistical explanation, counts are often paired with the number of participants assessed so readers can understand the scale of the observed data. An estimate of an event proportion and an uncertainty interval can help convey precision, but no such estimate or interval is reported for the primary outcome in the registry record. With a small enrolled group, each participant's classification can have a substantial influence on a count-based summary. This is a general property of small samples, not a claim about an unreported result from this study.

What can a single-group design establish?

A single-group study can describe measurements made in the participants under the recorded study conditions. It does not, by itself, estimate a contrast with an untreated or separately treated group. In this study, the cystometrogram description includes bladder filling and pudendal nerve stimulation through an implanted device. The registry does not report a control condition or a randomized assignment. Therefore, a causal comparison between stimulation and a distinct comparator cannot be obtained from the listed design.

The study aim mentions different stimulation frequencies. General statistical principle: when responses are measured under several conditions, the analysis needs to account for how those conditions were assigned or sequenced and whether observations within a participant are related. The frequency settings, testing order, and analysis of repeated measurements are not reported in the registry record. No conclusions about frequency-specific differences can be drawn from the stated aim alone.

Why do confidence intervals matter?

In general, a confidence interval describes the statistical uncertainty around an estimate under the assumptions of the method used. It helps distinguish a precise estimate from one compatible with a wider range of values. An interval does not repair limitations in study design, and it cannot establish that an observed relationship is causal. The registry record reports no confidence interval for the primary outcome, and no result is available from which to interpret one.

Likewise, a p-value is a summary of how data compare with a statistical model or null hypothesis under specified assumptions. It does not measure the size or importance of an effect. The registry record lists zero analyses and does not report a p-value for the primary or secondary outcomes. No inferential conclusion should be inferred from the completed status or from the outcome definitions.

What does the planning language mean?

General sample-size planning uses assumptions about the effect to detect, the desired statistical power, the significance level, allocation, and the analysis method. A planning illustration based on an observed effect is not an observed result and is not the same as the study's prospective design justification. The registry record does not report a trial-specific sample-size justification. Any planning illustration should therefore be understood as a hypothetical calculation under its stated assumptions, not as evidence that this study had a particular probability of detecting an effect.

In general, over-dispersion matters when observed count variability exceeds what a chosen statistical model expects; ignoring it can make uncertainty appear smaller than it is. This study's primary outcome is a participant count, but the registry record does not report a fitted count model or dispersion estimate. It is therefore not possible to say that over-dispersion was assessed or that a particular model was used.

These principles clarify what statistical summaries could mean, but they do not substitute for unreported data. The available record defines the endpoint and design, while the primary outcome value, analysis method, uncertainty estimates, and secondary outcome results are not reported in the registry record.

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("Cystometrogram")
n      <- c(5)
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  Cystometrogram  5  1  20.0  0.5  71.6  3.6  62.4  4.3  64.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures, including the primary bladder-contraction count and secondary outcomes on selective stimulation of pudendal nerve branches and urethral leak point pressure. It lists zero analyses. The registry record does not report a multiplicity strategy, such as a hierarchy of outcomes or an adjustment to account for examining multiple outcomes. Without posted outcome results and an analysis plan, it is not possible to assess how multiple statistical tests were handled or how any reported findings would relate to a prespecified primary question.

Missing-data handling is also not reported in the registry record. The record does not state whether all enrolled participants completed the cystometrogram, how incomplete measurements would be handled, or whether any outcome observations were unavailable. Enrollment of 5 participants does not by itself establish that all 5 contributed data to every outcome. The primary endpoint's observed count and the number assessed for that endpoint are not reported.

Analysis populations are not defined in the registry record. It does not specify whether results were intended to include every enrolled participant, only participants who completed testing, or another defined group. This matters because the denominator and inclusion rules determine what a participant count represents. No assumptions about missing values, exclusions, or analysis populations can be made from the stated design alone.

As a general statistical principle, missingness can affect interpretation when the availability of measurements is related to participant characteristics or outcomes. A transparent report ordinarily explains the number assessed, exclusions, and methods for incomplete observations. Those details are not reported in the registry record, so the effects of any missing data cannot be evaluated.

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.

For the Cystometrogram group, the registry reports 5 participants at risk for serious adverse events and 0 affected. It also reports 5 at risk for other adverse events and 0 affected. Deaths are reported as 0. No serious adverse-event terms are listed. These are the safety counts recorded for the group; they do not supply additional detail about event definitions, collection procedures, or the observation period.

A count of zero means that no affected participants are recorded in the registry for the stated category. It should not be read as proof that an event is impossible, or as a precise estimate of risk in other populations or settings. General statistical principle: when a study includes a small number of participants, zero recorded events still leaves uncertainty about how often events might occur outside the observed group. No uncertainty interval is reported for these safety counts.

The safety record does not describe severity categories for non-serious events, event timing, attribution to the device or procedure, or participant-level details. These details are not reported in the registry record. The counts therefore support a narrow description of the posted safety data, not a broader claim about safety.

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

The record establishes that a completed, single-group study enrolled 5 participants with previously implanted pudendal nerve neurostimulators and listed urinary retention and underactive bladder as conditions of interest. The study examined bladder responses during cystometrogram testing with stimulation applied through the implanted device. Its primary endpoint was the number of participants with an evoked bladder contraction of at least 20 centimeters of water.

The primary endpoint result is not reported in the registry record. As a result, the record does not show how many participants met the threshold, how responses varied, or whether results differed across stimulation frequencies. The study aim and endpoint definition are not themselves evidence of an observed response. Secondary outcome results are also not reported.

The single-group design does not provide a listed control group for a direct comparison. Even a reported count would describe the observed participants in the recorded testing context; it would not by itself establish what would have happened under a different condition. The registry record does not report the stimulation settings or sequence needed to interpret frequency-specific results, nor does it provide an analysis plan or uncertainty estimates.

The safety counts report 0 serious adverse events among 5 participants at risk, 0 other adverse events among 5 at risk, and 0 deaths. These counts describe what is recorded, but the absence of reported events in this group does not prove that no risk exists. Details about ascertainment and observation time are not reported.

Overall, the registry record allows readers to identify the study question, design, enrolled group, outcome definitions, and posted safety counts. It does not provide the primary or secondary efficacy results needed to characterize the measured bladder responses. The record therefore cannot support a conclusion about the magnitude, precision, or frequency-specific pattern of those responses.

14. Why This Trial Matters Statistically

This study illustrates a central statistical distinction between a clearly defined endpoint and a reported outcome. The registry defines a participant-level threshold for an evoked bladder contraction and gives a testing timeframe. However, the observed primary count is not reported. An endpoint definition tells readers what was intended to be measured; it cannot show what the measurements were.

The record also highlights how design constrains interpretation. A single-group study can describe observations under its testing conditions, but it does not provide a randomized comparison with a separate control group. This distinction is important when readers encounter a study aim involving different stimulation frequencies: the aim does not reveal how frequencies were tested or whether their results differed. Those details are not reported in the registry record.

The small enrollment of 5 participants makes the distinction between description and generalization especially important. As a general statistical principle, estimates from small groups are often uncertain, and individual observations can strongly affect count-based summaries. Without a reported outcome count or uncertainty estimate, the precision of the primary result cannot be assessed.

The registry also lists zero analyses and does not report a trial-specific analysis plan, missing-data approach, analysis population, or multiplicity strategy. These omissions limit the ability to evaluate how outcomes would have been analyzed and how much confidence to place in any potential comparisons. The posted safety counts are useful as a factual record of recorded events, but they do not establish absence of risk.

Statistically, the study is a reminder that design, measurement, analysis, and transparent reporting all contribute to interpretation. In this record, the study question and endpoint are identifiable, while the results needed to quantify the primary response are not reported.

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 most direct limitation for interpreting outcomes is that the registry record does not report the observed primary endpoint count. It also does not report results for the listed secondary outcomes. Thus, readers cannot assess the distribution of responses, the size of any response, or differences by stimulation frequency from this record.

The study is single-group, with no separate comparator listed and allocation recorded as not applicable. The design therefore does not support a randomized between-group contrast. The enrollment is 5 participants, and the record does not provide participant characteristics or eligibility details that would help readers judge how well the group represents other people with the listed conditions.

The stimulation frequencies, settings, order, and duration are not reported. The registry describes bladder filling to different volumes and stimulation through implanted neurostimulators, but does not give further procedural detail. This limits interpretation of the intended frequency-focused question. The analysis plan, trial-specific sample-size justification, missing-data methods, and analysis populations are also not reported.

The primary outcome is threshold-based, so it records whether a participant meets the stated criterion rather than the complete range of contraction measurements. Participant-level data and uncertainty estimates are not reported. The registry also lists three outcome measures but does not report a strategy for handling multiplicity.

For safety, zero events are recorded in the listed categories, but the record does not provide event ascertainment details or an observation period. These limitations concern what can be learned from the registry record; they do not establish that unreported outcomes or procedures were absent from the study itself.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Previously Implanted Pudendal Nerve Stimulation — NCT04473469.
• Registry record last updated 2024-06-03; status last verified 2024-05.
• Results first posted 2024-06-03.
• 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

NCT04473469 is a completed, single-group study titled Previously Implanted Pudendal Nerve Stimulation, sponsored by the University of Michigan. The registry lists enrollment of 5 participants, urinary retention and underactive bladder, and use of the Medtronic Interstim II Model 3058 Neurostimulator in participants who had previously been implanted.

The study sought to examine bladder responses to different pudendal nerve stimulation frequencies. The primary outcome counts participants with an evoked bladder contraction of at least 20 centimeters of water during a cystometrogram at Visit 1, approximately 1 week after consent. Secondary outcomes concern selective pudendal nerve branch stimulation and urethral leak point pressure.

The primary and secondary outcome results are not reported in the registry record. The record lists zero analyses. Safety counts are 0 serious adverse events among 5 at risk, 0 other adverse events among 5 at risk, and 0 deaths. A trial-specific statistical analysis plan, sample-size justification, and details on missing data are not reported in the registry record.