Addition of Pudendal Blocks to Pelvic Floor Physical Therapy for the Treatment of Pelvic Floor Tension Myalgia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Addition of Pudendal Blocks to Pelvic Floor Physical Therapy for the Treatment of Pelvic Floor Tension Myalgia (NCT00928564), a randomized na study. The primary outcome is Visual Analog Pain Score After 6 Weekly Injections.

2. Clinical Question

3. Trial Design

The registry describes a randomized, double-masked, parallel-group trial of pudendal blocks added to pelvic floor physical therapy. Participants were assigned to a pudendal block arm or a placebo arm. The active block mixture and the saline placebo were administered at each block site as described in the registry. The record does not describe how the random sequence was generated, how allocation was concealed, or how masking was maintained. Those design details are not reported in the registry record.

The study enrolled 40 participants and is marked completed. The registry lists a start date of 2009-04 and a primary completion date of 2015-12. The primary endpoint was mean Visual Analog Pain Score after 6 weekly injections, with an outcome timeframe of up to 8 weeks. A secondary outcome assessed improvement in pelvic floor symptoms through validated questionnaires, with an outcome timeframe of up to 6 months. The description says the final patient assessment would be performed at 6 months to assess durability of response.

The primary outcome results include 22 participants in the pudendal block arm and 12 in the placebo arm. The secondary outcome is reported for the same arm counts. The registry does not explain how those counts relate to enrollment, whether all randomized participants contributed outcome data, or why the reported arm counts differ. A participant flow account and the analysis population are not reported in the registry record.

The registry does not report the trial's original sample-size assumptions, a statistical analysis plan, or whether interim analyses were planned or conducted. The planning figures associated with the posted results are illustrations based on the observed effect, not the trial's own design assumptions. The registry identifies the sponsor as the University of California, Irvine and lists the phase as NA.

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

Reasons for not completing this period:

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 Pain Score After 6 Weekly Injections, measured over up to 8 weeks.

The primary endpoint is the mean Visual Analog Pain Score after 6 weekly injections. The registry describes the scale as a 10 point likert scale, with zero representing no pain and ten representing the worst possible pain. The listed outcome timeframe is up to 8 weeks. The result is summarized as a mean and standard deviation in each arm, so the comparison concerns average reported pain scores rather than the number of participants who crossed a defined response threshold.

Pain is a symptom directly identified in the trial's primary hypothesis, which proposed that adding pudendal blocks to pelvic floor physical therapy would result in lower pain and pelvic floor muscle tension scores, lower baseline vaginal pressure, and increased pelvic floor strength. The registry's posted primary result concerns the pain score; it does not provide posted primary outcome results for each other measure named in that hypothesis. Whether those measures were collected or analyzed is not reported in the registry record.

A mean offers a compact description of the group score, while the standard deviation describes the spread of individual scores around that mean. Neither summary alone shows how each participant's score changed from baseline. The registry's primary endpoint is described as a score after the injections, and a baseline-adjusted analysis or participant-level change analysis is not reported in the registry record.

7. Results Posted in the Registry

• Pudendal Block: mean 3.33 versus 2.99 on control; difference 0.34 (95% CI -1.05 to 1.73), standardized effect d = 0.18; z-test p = 0.631.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Improvement in Pelvic Floor Symptoms as Assessed Through Validated Questionnaires

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Pudendal Block: mean 47.20 versus 38.20 on control; difference 9.00 (95% CI -11.85 to 29.85), standardized effect d = 0.30; z-test p = 0.398.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Pudendal Block and the control. The interval gives the range of effects that remain compatible with the data.

The registry posts one secondary outcome: improvement in pelvic floor symptoms assessed through validated questionnaires, with a timeframe of up to 6 months. Its results are expressed as a mean and standard deviation in each arm. The posted comparison has a positive mean difference of 9.0, with a confidence interval from -11.85 to 29.85 and an unadjusted p-value of 0.398. The interval crosses zero, so the estimate does not precisely establish the direction of the difference. The questionnaire's scale direction and a clinically important threshold are not reported in the registry record.

Because there is only one posted secondary outcome, the record does not offer a set of secondary endpoints whose consistency can be compared with one another. The secondary comparison also does not independently settle the primary question: it measures a different outcome, on a different scale, at a different timeframe. Its estimate and uncertainty should be considered alongside the primary result, not treated as a replacement for it or as confirmation of a treatment effect.

Secondary outcomes often help describe broader aspects of a trial's research question, but they may be less definitive than the primary outcome. The registry does not report whether this endpoint was prespecified in a statistical analysis plan, whether a multiplicity adjustment was planned, or what analysis population was used. The reported p-value is unadjusted. When more than one outcome or comparison is examined, the chance of a nominally unusual result can increase unless the analysis accounts for the multiplicity or clearly distinguishes confirmatory from exploratory questions. The registry does not provide enough information to assess that issue fully.

The record lists no reported analyses for the secondary outcome, despite posting group summaries and a comparison estimate. That makes it unclear whether the posted estimate represents the sponsor's prespecified analysis, a registry summary, or another analysis approach. The statistical method and any model adjustments are not reported. Accordingly, the secondary result is best treated as an uncertain descriptive comparison rather than as a stand-alone basis for a firm conclusion.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Improvement in Pelvic Floor Symptoms as Assessed Through Validated Questionnaires

9. Statistical Interpretation

10. Statistical Methods Explained

The primary result is a comparison of means for a continuous outcome. A continuous score can take a range of numeric values; here, the outcome is a pain score on the scale described in the registry. The arm means provide the average recorded score in each group, and the standard deviations describe the variability of scores among participants within each group. A difference between means expresses the estimated separation of the group averages in the score's units.

What does the mean difference represent?

The posted mean difference is 0.34 for pudendal block minus placebo. A positive estimate means the reported average score in the pudendal block arm is numerically higher than the average in the placebo arm. The scale description identifies zero as no pain and ten as the worst possible pain, but the estimate alone does not establish why the group averages differ or whether the difference matters to participants. The registry does not report a threshold for a clinically important difference.

In general, a mean difference is a summary of the observed separation in group averages. It does not describe the full distribution of individual scores, guarantee that each participant experienced a change in the same direction, or indicate how scores changed from baseline. The registry does not report baseline values or a within-participant change analysis for the primary endpoint. The comparison method and any adjustment for baseline scores are not reported in the registry record.

How should the standard deviation be read?

The posted standard deviations are 1.87 for pudendal block and 2.03 for placebo. In general, a standard deviation describes how spread out observations are around a group mean. It is not the uncertainty of the mean itself, nor does it give the range of scores for every participant. A standard deviation can help readers understand that individual scores vary, while the confidence interval for a between-arm difference addresses uncertainty in that estimated contrast.

The registry reports a standard deviation for each group and a pooled standard deviation of 1.926 for the primary comparison. Pooling is a way to combine information about within-group variability for a comparison under assumptions about the groups' variability. The precise method used for the posted estimate and interval is not reported in the registry record. The pooled value should not be mistaken for either arm's standard deviation or for a measure of the precision of the mean difference.

What does the p-value add?

The unadjusted p-value for the primary comparison is 0.631. In general, a p-value evaluates the compatibility of the data with a specified null hypothesis under the statistical model and test used. It is not the probability that the observed difference occurred by chance, and it is not a measure of clinical importance. The test and model behind the posted p-value are not reported in the registry record. The term unadjusted indicates that the reported value is not presented as adjusted for multiple comparisons; whether any separate prespecified adjustment was planned is not reported.

A p-value and a confidence interval answer related but different questions. The p-value gives a test-based summary under a null model, while the interval presents a range of effect values compatible with the data under its method and confidence level. The confidence level and interval method are not reported in the registry record. The interval's inclusion of zero is consistent with the unadjusted p-value not indicating strong evidence against a zero difference, but neither feature proves that the groups are equivalent.

Why does variability matter?

Greater variability generally makes group means harder to distinguish precisely, all else being equal. The observed standard deviations describe variation in scores, and the outcome counts describe how many participants contributed to each summary. In general, estimates based on fewer observations tend to be less precise than estimates based on more observations when other features are comparable. In this trial, the primary outcome counts are 22 and 12. The interval is correspondingly important to interpretation because it communicates uncertainty around the estimated difference rather than presenting the point estimate alone.

In general, over-dispersion means the observed variation is greater than a model assumes. When a model underestimates variability, standard errors may be too small and intervals may be too narrow. The registry does not report an over-dispersion assessment for these continuous outcomes, and the concept should not be taken as a finding about this trial. More broadly, a suitable analysis needs to account for the outcome's scale, its distribution, the design, and any repeated measurements or missing observations; the detailed statistical plan is not reported in the registry record.

How do the planning illustrations differ from the trial analysis?

The posted sample-size illustrations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. They consider an effect equal to 100%, 75%, or 50% of the observed effect. The estimates are participants per arm for this continuous-outcome comparison. These assumptions describe the planning illustration, not the original design of the trial. The trial's own sample-size justification and design assumptions are not reported in the registry record.

Power is the probability that a study would meet a specified statistical criterion if a particular effect and model were true. In the illustrations, the 80% and 90% columns indicate the per-arm sample sizes associated with those target probabilities under the listed assumptions. The figures do not describe the probability that the completed trial found a true effect, and they are not observed power. The planning estimates are tied to the observed effect used as their reference; a smaller effect target requires more participants under the stated assumptions. A planning calculation based on a noisy observed estimate is not a substitute for a prespecified design justification.

11. Confidence Intervals and Precision

The primary confidence interval runs from -1.049 to 1.729 around a mean difference of 0.34. In general, a confidence interval summarizes the uncertainty of an estimate under a method and confidence level. It is not a range that guarantees the true value lies within it, nor does it describe the range of individual participants' scores. The confidence level and method used for the posted interval are not reported in the registry record.

The interval includes zero, the value corresponding to no difference in group means, and extends to both negative and positive values. The negative values are compatible with a lower mean score in the pudendal block arm than in placebo; the positive values are compatible with a higher mean score in the pudendal block arm. The interval therefore does not pin down the direction of the difference. Its width is a key part of the interpretation: the point estimate alone gives a much more definite impression than the full range of uncertainty supports.

For the secondary questionnaire outcome, the confidence interval extends from -11.85 to 29.85 around a mean difference of 9.0. This interval also includes zero and spans possible differences in both directions. The questionnaire scale's scoring direction and a clinically important threshold are not reported in the registry record, so the endpoints cannot be converted into a judgment about meaningful symptom change.

In general, precision depends on factors including variability, sample size, and the analysis method. The primary outcome counts are 22 and 12, and the reported standard deviations are 1.87 and 2.03. These counts and variability are relevant context for interpreting the interval, but the registry does not report enough analysis detail to reconstruct its method independently. The intervals show that these estimates are uncertain; they do not, on their own, establish whether the uncertainty is clinically acceptable.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning estimates for these continuous outcomes are stated as participants per arm, not as total participants and not as total events. The sample-size assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The calculation considers effects equal to 100%, 75%, and 50% of the observed effect. These are planning illustrations based on the observed effect, not the trial's original sample-size justification, which is not reported in the registry record.

The 80% power column gives the per-arm sample size associated with an 80% target probability of detecting the specified effect under the planning assumptions. The 90% power column does the same for a 90% target probability. In general, higher target power requires more participants when other assumptions stay the same. The estimates also increase as the target effect becomes smaller: a smaller difference is harder to distinguish from sampling variability, so more participants are needed under the same assumptions.

For the primary outcome, the planning estimates range from 504 to 2,016 participants per arm for the 80% target and from 675 to 2,699 participants per arm for the 90% target across the stated effect scenarios. For the secondary outcome, they range from 177 to 707 participants per arm for the 80% target and from 237 to 947 participants per arm for the 90% target. The ranges reflect different assumed fractions of the observed effect, not alternative observed trial results.

These calculations are not observed power. They do not measure the probability that the completed trial's findings are true or determine whether the trial succeeded. Their purpose is to illustrate how sample-size requirements change with the assumed effect and target power under the listed planning model. The original protocol assumptions, including any intended target sample size, are not reported in the registry record.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.340; pooled standard deviation σ = 1.926.
2. n = 2 × (1.96 + 0.842)² × 1.926² / 0.340² = 504.0, rounded up to 504 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 0.34                      # observed difference in means
sigma <- 1.92649941603936                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(928564)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 504 (80% power), 675 (90% power)
 75% of observed effect: n per arm = 896 (80% power), 1,200 (90% power)
 50% of observed effect: n per arm = 2,016 (80% power), 2,699 (90% power)
power.t.test: 504.9 
Simulated power at n = 504 per arm: 0.799 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary pain outcome and one secondary questionnaire outcome. The study description also names pelvic floor muscle tension, baseline vaginal pressure, and pelvic floor strength in its primary hypothesis, but the posted primary outcome result is the Visual Analog Pain Score. Whether those other measures were collected, specified as endpoints elsewhere, or analyzed is not reported in the registry record. The complete set of planned outcomes and comparisons is therefore unclear.

The reported p-values are unadjusted. A multiplicity strategy can control the increased chance of false-positive findings when several outcomes or comparisons are evaluated. The registry does not report whether an adjustment was planned, how outcomes were prioritized, or whether the secondary measure was intended to be confirmatory or exploratory. No adjustment should be inferred from the posted results, and the effect of any unreported multiplicity plan cannot be assessed.

Handling of missing data is also not reported in the registry record. The primary and secondary outcome summaries use 22 participants in the pudendal block arm and 12 in the placebo arm, while total enrollment is listed as 40. The record does not explain participant disposition, the amount or pattern of missing outcome data, or how missing values were treated. It does not identify whether the analyses included all randomized participants, only participants with available observations, or another population.

The registry does not describe the statistical analysis plan, model specification, assumptions about the outcome distributions, baseline adjustment, or sensitivity analyses. Interim analyses and stopping rules are not reported. Without these details, readers cannot determine how closely the posted estimates follow a prespecified analysis or how robust they are to alternative assumptions. These omissions do not by themselves show that the analysis was inappropriate, but they limit independent assessment of the results and their inferential context.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

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 zero serious adverse events among 22 participants at risk in the pudendal block arm and zero among 12 participants at risk in the placebo arm. These are reported counts within the listed groups. The registry does not provide serious adverse event terms, and deaths are not reported in the registry record. A count of zero in the posted record should be read as a report about the recorded events and observation period, not as proof that serious events could not occur.

Other adverse events are reported for 4 participants in each arm, with 22 at risk in the pudendal block group and 12 at risk in the placebo group. The registry does not provide the event descriptions, severity, timing, relationship to the assigned intervention, or whether participants could experience more than one event. Without those details, the counts do not reveal the type or clinical significance of the events, and comparisons should not be converted into conclusions about safety.

Adverse event counts are descriptive and depend on what was monitored and recorded. The registry record does not give the safety assessment procedures or a detailed account of follow-up for adverse events. These posted figures should therefore be interpreted narrowly as the event counts recorded for the listed groups.

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

The posted primary comparison estimates a mean pain-score difference of 0.34, with a confidence interval from -1.049 to 1.729 and an unadjusted p-value of 0.631. These statistics describe the observed arm summaries and the uncertainty around their difference. The interval includes zero and permits both negative and positive differences, so the data do not clearly determine the direction or size of the between-arm difference.

The result does not establish that the arms are equivalent. Demonstrating equivalence requires a prespecified margin and an analysis designed to assess whether differences fall within that margin; neither is reported in the registry record. Nor does a non-significant p-value prove that there is no difference. It indicates that the posted comparison does not provide strong statistical evidence against a zero-difference null under the analysis used, whose method is not reported.

The results also do not show how individual participants changed from baseline. The registry posts group mean scores after the injections but does not report baseline group values or a participant-level change analysis. The outcome timeframe is up to 8 weeks, while the study description mentions a final assessment at 6 months. The registry record does not provide a posted primary result at that later time point.

The secondary questionnaire result has its own uncertainty and a different measurement scale. The scoring direction and clinically important threshold for that scale are not reported, so its numeric estimate cannot be translated into a claim about the practical meaning of symptom change. Neither the primary nor secondary comparison alone establishes that an intervention works or does not work.

Interpretation is further limited by missing information about participant flow, analysis populations, missing data, prespecified statistical methods, and multiplicity. The reported summaries are evidence about the data recorded in the registry, but they are not a complete account of the trial's design and analysis. No medical recommendation follows from these statistics.

17. Why This Trial Matters Statistically

This trial illustrates why a point estimate should not be read in isolation. The primary mean difference is 0.34, but the confidence interval extends from -1.049 to 1.729. The estimate alone gives a single numerical contrast; the interval communicates that the data are compatible with a range of differences on either side of zero. The p-value adds a test-based summary but does not remove that uncertainty.

The outcome summaries also show why the number of observations and the variability of a measure matter. The reported primary outcome counts are 22 in the pudendal block arm and 12 in the placebo arm, and the standard deviations are 1.87 and 2.03. Those features provide context for the precision of a comparison, while the confidence interval gives a direct view of uncertainty in the estimated difference. The registry's lack of participant-flow and missing-data details prevents a fuller assessment of who contributed to the reported results.

The planning illustrations highlight the dependence of sample-size requirements on the assumed effect and desired power. They use the observed effect as a reference and show that smaller target effects require more participants under the stated assumptions. Because the registry's original design assumptions are not reported, these illustrations should not be mistaken for the rationale behind enrollment or for evidence about the trial's achieved power.

Finally, the record demonstrates the importance of analysis transparency. The outcome summaries are accompanied by estimates and unadjusted p-values, but the statistical test, confidence level, missing-data handling, analysis population, and multiplicity plan are not reported. Such details help readers assess whether estimates answer the prespecified question and how much confidence to place in secondary findings. Their absence limits interpretation without changing the numerical results that are posted.

18. 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 outcome counts are 22 for the pudendal block arm and 12 for placebo, while the registry lists 40 participants enrolled. The record does not explain this difference in reported counts or provide a participant flow account. Without that information, it is not possible to determine whether the summaries include all randomized participants or whether missing outcome data could affect the comparisons.

The registry labels the trial randomized and double masked, but does not report sequence generation, allocation concealment, or masking procedures. It does not report the statistical analysis plan, the method used to calculate the p-values and confidence intervals, the confidence level of those intervals, or any baseline adjustment. These omissions prevent a detailed assessment of the analysis choices and their assumptions.

The primary endpoint is described as a score after 6 weekly injections, with a timeframe of up to 8 weeks. The study description also mentions a final patient assessment at 6 months, but the posted primary result is not given at that later timeframe. The record does not show whether scores were collected repeatedly or how any repeated observations were analyzed. Baseline pain-score results are not reported.

The secondary questionnaire's scoring direction and a threshold for clinically important change are not reported. The registry posts one secondary outcome but lists no reported analyses for it. It also does not report a multiplicity plan or the analysis population. These limitations are specific to the available record and restrict conclusions about the interpretation, robustness, and generalizability of the posted estimates.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Addition of Pudendal Blocks to Pelvic Floor Physical Therapy for the Treatment of Pelvic Floor Tension Myalgia — NCT00928564.
• Registry record last updated 2021-02-10; status last verified 2021-01.
• Results first posted 2021-02-10.
• 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.

22. Record Summary

The registry record describes a completed, randomized, double-masked, parallel trial sponsored by the University of California, Irvine. It lists 40 participants enrolled and compares pudendal block plus pelvic floor physical therapy with placebo blocks plus pelvic floor physical therapy. The primary outcome is mean Visual Analog Pain Score after 6 weekly injections, with a timeframe of up to 8 weeks.

The primary mean difference is 0.34, with a confidence interval from -1.049 to 1.729 and an unadjusted p-value of 0.631. One secondary questionnaire outcome is posted, with a mean difference of 9.0, a confidence interval from -11.85 to 29.85, and an unadjusted p-value of 0.398. Both comparisons have uncertainty that includes zero. Participant flow, analysis populations, missing-data methods, the analysis plan, and the confidence level are not reported in the registry record.