Assess the Effectiveness of Pulse RadioFrequency in Patients With Chronic Lumbar Radicular Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Assess the Effectiveness of Pulse RadioFrequency in Patients With Chronic Lumbar Radicular Pain (NCT01117870), a randomized na study. The primary outcome is Recruitment Rate.

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group, placebo-controlled study sponsored by McMaster University. The registry record lists an enrollment of 31 and a status of completed. The study start is recorded as 2010-07, with primary completion in 2012-06. The record labels masking as triple, while the official title calls the study double-blinded. It does not identify which study roles were masked or explain the difference between those descriptions.

The active group received pulsed radiofrequency treatment of the dorsal root ganglion. The intervention description specifies application for 120 seconds at 42 degrees celsius. Participants assigned to placebo received low-voltage continuous stimulation through the needle, intended to give a sensation of PRF treatment. The record does not report details about how random assignments were generated, concealed, or implemented.

The primary outcome was recruitment rate. Its description set expectations of at least 4 patients per month and recruitment of at least 80% of eligible patients. It states that final assessment was at the 15 month point and that all subjects were enrolled by then. The posted information does not give the observed monthly recruitment rate, the number eligible, or the fraction of eligible patients recruited, so those expectations cannot be evaluated from the record.

Secondary outcomes included change in mean visual analogue scale scores from baseline to 4 weeks, side effects, change in Oswestry Disability Index from baseline to 4 weeks, and discontinuation of analgesics after intervention. The record lists six outcome measures in total, but quantitative results are not reported for the clinical outcomes. It also does not report a detailed 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Patients with suspected leg pain were initially approached by the research assistant. Further screening for eligibility was done in the presence of the physician. Suitable patients met with the research assistant (blind to intervention), who noted down the baseline parameters of the patient after obtaining an informed consent.

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.

Population: Adult population both male and female \>=18 years old

6. Primary Endpoint

The registry lists the primary outcome as Recruitment Rate, measured over 15 month point.

The listed primary endpoint is recruitment rate, expressed as a count of participants. The registry describes two feasibility expectations: recruitment of at least 4 patients per month and recruitment of at least 80% of eligible patients. It identifies the 15 month point as the final assessment and states that all subjects were enrolled by then. These statements make recruitment and the ability to enroll eligible patients the focus of the primary endpoint, rather than change in pain or function.

Recruitment outcomes are used to assess whether a study can enroll its intended population within its planned period. They can inform whether the recruitment process appears workable and whether a larger study may be feasible. A count alone does not describe recruitment efficiency fully: interpretation also depends on the eligible population, the time over which recruitment occurred, and the number of people approached or screened. The registry record does not report the eligible-patient denominator or the observed monthly recruitment rate. Thus, the statement that all subjects were enrolled by the final assessment does not by itself show whether both stated recruitment expectations were met.

The registry also names clinical outcomes, including pain, disability, side effects, and analgesic discontinuation. Those outcomes address different questions from recruitment feasibility. Their quantitative results are not reported in the registry record, so the primary endpoint description cannot be read as evidence about clinical benefit or harm.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization assigns participants to study groups by chance. In general, this is intended to reduce systematic differences between groups at the start of a trial, so that a later comparison is less vulnerable to selection effects. The registry record identifies this study as randomized and parallel-group. It does not describe the sequence-generation method, allocation concealment, or any stratification factors. Without those details, the quality of those implementation steps cannot be assessed from the registry record.

What does masking mean?

Masking is intended to limit the influence of knowledge about treatment assignment on participant experience, clinical management, outcome assessment, or analysis. The record labels masking as triple, while its official title uses the term double-blinded. It does not say which roles were masked, how masking was maintained, or whether masking was evaluated. The placebo procedure used low-voltage continuous needle stimulation to create a sensation of PRF treatment. That description explains the intended comparison, but it does not establish whether participants or staff could distinguish assignments.

What can the recruitment endpoint tell us?

A recruitment rate describes enrollment over time; a recruitment proportion compares those enrolled with an eligible population. In general, both can help assess whether a study can recruit its target population. The registry gives expectations of at least 4 patients per month and at least 80% of eligible patients, and says all subjects were enrolled at the 15 month point. It does not report the observed rate or eligible-patient denominator. The enrollment count and completion statement therefore do not permit a direct check of both expectations.

How should clinical comparisons be assessed?

For a clinical endpoint, an analysis would ordinarily define the outcome, the treatment-group contrast, the time point, and the population included. A point estimate describes the estimated contrast; a confidence interval conveys its uncertainty under the chosen model. A p-value addresses how compatible the observed data are with a specified null hypothesis and assumptions. These quantities are not interchangeable: a small p-value does not state the size or clinical importance of an effect, and a confidence interval is needed to understand its precision. The registry record lists clinical outcomes but does not report quantitative results, effect estimates, confidence intervals, or p-values for them.

Outcome type also matters. Visual analogue scale and Oswestry Disability Index changes are measurements of pain and disability, while discontinuation of analgesics is a count-based outcome. The registry identifies side effects as an outcome, but does not provide its detailed definition. Different outcome types may need different statistical models and summaries. No model choices or endpoint-specific analysis details are reported in the registry record, so it is not possible to determine how these outcomes were analyzed.

What do the planning assumptions mean?

The planning illustration associated with the record uses a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. It describes the effect to detect as a stated fraction of the observed effect. Such sample-size illustrations are planning exercises, not evidence of the power achieved in the completed trial and not the trial's original design justification. The registry record does not report the study's sample-size justification or a statistical plan establishing that these assumptions governed the trial.

In general, power is the probability that a specified analysis will reject a null hypothesis when a particular effect is present, under its assumptions. It depends on the chosen effect, outcome variability, sample size, allocation, and analysis. A planning calculation based on an observed effect is especially dependent on that estimated effect and should not be presented as observed power. No numerical sample-size result is reported in the registry record, and the primary outcome is a recruitment count rather than a comparison with two treatment arms. The record notes that the primary-outcome setup does not support the planning calculation.

Why do uncertainty and model assumptions matter?

Every statistical model makes assumptions about the data and how observations relate to one another. If a model does not represent the outcome distribution or study process well, its uncertainty estimates and tests can be misleading. For count outcomes, for example, over-dispersion means that observed variability exceeds what a simple model assumes; a model that ignores it may give overly narrow uncertainty estimates. This is a general statistical consideration, not a reported feature of this trial. The registry does not give enough outcome data or model details to assess distributional assumptions, over-dispersion, or robustness.

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("Eligible Patients")
n      <- c(41)
events <- c(32)
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  Eligible Patients  41  32  78.0  62.4  89.4  63.3  88.0  63.2  87.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures. Named secondary outcomes include visual analogue scale change from baseline to 4 weeks, side effects, Oswestry Disability Index change from baseline to 4 weeks, and discontinuation of analgesics after intervention. The primary outcome is recruitment rate. The record does not report a hierarchy among all outcomes, a prespecified strategy for controlling multiplicity, or whether any adjustment for multiple comparisons was planned. When several outcomes or contrasts are tested, the chance of at least one apparently unusual result can increase; a prespecified approach helps readers understand how that possibility was handled. No such approach is reported in the registry record.

The registry description says participants withdrawing within 4 weeks after intervention were not to be included, while participants withdrawing after 4 weeks were to be included in the final analysis on an intention-to-treat principle. This is a stated analysis rule, not a report of how many participants withdrew or how the rule was applied. The record does not report missing outcome data, reasons for missingness, imputation methods, or sensitivity analyses. It also does not explain how the stated withdrawal rule relates to the analysis of each secondary outcome.

The registry record lists no analyses. It does not provide analysis populations, endpoint-specific models, or an account of deviations from the planned approach. Therefore, the handling of multiplicity, missing data, and analysis populations cannot be fully evaluated. The stated intention-to-treat approach for later withdrawals should not be taken to establish that every randomized participant contributed to every reported analysis.

12. 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.

The registry reports zero serious adverse events and zero other adverse events in the placebo group, with 15 participants at risk for each category. For the PRF Treatment group, it reports zero serious adverse events and zero other adverse events, with 16 participants at risk for each category. No serious adverse event terms are listed. These entries describe the registry's event counts and denominators; they do not establish that no symptoms or harms occurred outside the reported categories or reporting process.

The death counts are not reported in the registry record. The absence of listed serious adverse event terms is not the same as a complete description of all safety observations. The record does not give event definitions, observation completeness, duration of safety follow-up, or detail about how events were collected. Zero reported events in a study of this size also cannot rule out uncommon harms or estimate precisely how frequently events might occur in a broader population. These safety entries should therefore be read as limited descriptive reporting, not as proof of safety or as a comparison demonstrating that either treatment is safer.

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

This record documents a randomized comparison of pulsed radiofrequency and placebo in people with chronic lumbar radicular pain, with total enrollment reported as 31. Its primary outcome concerns recruitment feasibility. The registry says all subjects were enrolled by the final assessment at the 15 month point, but does not report the observed recruitment rate or the eligible-patient denominator. That information is insufficient to verify the stated recruitment expectations.

The record also names clinical outcomes relating to pain, disability, side effects, and discontinuation of analgesics. Their quantitative results are not reported in the registry record. Accordingly, the posted information does not establish the direction, size, or precision of a treatment-group difference in pain or disability. It does not support a conclusion that PRF is effective or ineffective, and it does not permit assessment of whether any difference would be clinically important.

The reported adverse-event counts are zero in both groups, but the registry does not provide enough detail to treat those entries as a complete safety assessment. Death counts are not reported. The counts should not be interpreted as proving that treatment caused no harms.

In general, the interpretation of a randomized trial depends on complete outcome reporting, clear analysis methods, and uncertainty estimates alongside effect estimates. Those elements are not available for the clinical outcomes in this record. The study's documented completion and enrollment statement can inform discussion of feasibility, but they cannot substitute for comparative clinical results. Any broader conclusion would go beyond what the registry record reports.

14. Why This Trial Matters Statistically

Feasibility is an important statistical question because a clinical study needs to recruit the population on which its planned comparisons depend. This trial made recruitment rate its primary outcome and stated expectations for monthly recruitment and the proportion of eligible patients recruited. The record's statement that all subjects were enrolled by the 15 month assessment point provides a limited indication that enrollment occurred, while the missing eligible-patient denominator and observed rate prevent a full assessment of the stated targets.

The study also illustrates why an outcome's label and its role matter. Recruitment is not a treatment-effect endpoint. A completed recruitment process does not establish comparative effects on pain or disability, and clinical outcome results are not reported in this record. Keeping feasibility findings separate from treatment-effect evidence avoids interpreting an enrollment statement as a clinical result.

The contrast between the registry's triple-masking label and the official title's double-blinded wording is another reason to look for operational detail. The record does not identify the masked roles, allocation procedures, or statistical analyses. These omissions limit assessment of how the trial was implemented and how its outcomes would have been interpreted.

Finally, the limited safety counts illustrate the value of reporting definitions and follow-up context, as well as event counts. Zero recorded events do not by themselves establish absence of risk. Transparent reporting of denominators, missing observations, analysis populations, and uncertainty is essential for readers to distinguish what a study measured from what its record can support.

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 registry record does not provide the complete eligibility criteria, the number of people screened or eligible, or the number not recruited. Although it states that all subjects were enrolled at the 15 month assessment point, the observed recruitment rate and eligible-patient recruitment proportion are not reported. This limits evaluation of the stated feasibility expectations.

Details of randomization and masking are also limited. The record labels masking as triple, while the official title describes a double-blinded trial, and it does not identify the roles masked or explain the difference. Sequence generation, allocation concealment, and masking procedures are not reported in the registry record.

Quantitative results for the clinical outcomes are not reported, and the record lists no analyses. It does not give effect estimates, uncertainty intervals, endpoint-specific models, or a statistical analysis plan. Although the registry describes how withdrawals before and after 4 weeks were to be treated, it does not report actual withdrawals, missing outcome data, or how the rule was implemented for each outcome.

The safety record is limited to reported event counts and participants at risk. Event definitions, collection procedures, follow-up completeness, and death counts are not reported. These omissions restrict interpretation of both the zero event counts and the feasibility findings. The record does not report the study's sample-size justification, so the basis for the planned enrollment cannot be assessed from the registry information.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Assess the Effectiveness of Pulse RadioFrequency in Patients With Chronic Lumbar Radicular Pain — NCT01117870.
• Registry record last updated 2026-08-28; status last verified 2026-08.
• Results first posted 2017-03-21.
• 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

NCT01117870 is a completed randomized, parallel-group, placebo-controlled trial sponsored by McMaster University. The registry reports enrollment of 31, a study start of 2010-07, and primary completion in 2012-06. The intervention was pulsed radiofrequency treatment of the dorsal root ganglion; the placebo procedure used low-voltage continuous needle stimulation. The record labels masking as triple, while the official title says double-blinded.

Recruitment rate was the primary outcome, with expectations of at least 4 patients per month and at least 80% of eligible patients recruited. The record says all subjects were enrolled at the 15 month assessment point but does not report the observed rate or eligible-patient denominator. Clinical secondary outcomes are named, but their quantitative results and analysis details are not reported in the registry record. The record reports zero serious and zero other adverse events in each group; death counts are not reported.