Patients With Chronic Knee Pain Treated With Conventional Radiofrequency of the Genicular Nerves: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Patients With Chronic Knee Pain Treated With Conventional Radiofrequency of the Genicular Nerves (NCT04234984), a registered phase not stated study. The primary outcome is The Number of Patients Reaching Treatment Succes at 6 Weeks Defined as Global Perceived Effect (GPE) of ≥ 50% Compared to Baseline..

2. Clinical Question

3. Trial Design

This is a retrospective, single-center cohort study of conventional radiofrequency treatment of the genicular nerves in patients with chronic knee pain. The registry names Ziekenhuis Oost-Limburg as sponsor and lists the study status as completed. The registry start date is 2020-01-26, and the primary completion date is 2020-11-15. These registry dates are distinct from the period of patient treatment described in the study summary: 1 September 2017 to 31 December 2019.

The study summary says that patients treated with radiofrequency ablation at the multidisciplinary chronic pain center during that period were to be analyzed retrospectively, excluding patients with chronic widespread pain. Enrollment is listed as 66, but the record does not specify the number with observed data at each follow-up or outcome. It also does not describe recruitment details, the number screened, or reasons for any exclusions beyond the stated exclusion criterion.

The registry describes one treatment arm: conventional radiofrequency treatment. No randomized allocation or control arm is reported. The allocation method is not stated, so this cohort cannot be interpreted as a randomized treatment comparison or as a direct comparison with an untreated group. The record also does not report a protocol-level sample-size justification or explain whether the enrollment reflects all eligible patients in the review period.

The primary outcome is measured six weeks after treatment and is based on global perceived effect. Secondary outcomes address NRS pain, patient-reported physical functioning, strong opioid use, treatment success at a later time point, and post-treatment complications. The registry lists nine secondary outcome measures. It does not report outcome-level results or statistical analyses; the analyses field lists zero analyses.

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.

Before assignment: Excluded patients (n=7): Chronic widespread pain (n=7)

Follow-up at 6 Weeks

Reasons for not completing this period:

Follow-up at the Second Time Point

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 The Number of Patients Reaching Treatment Succes at 6 Weeks Defined as Global Perceived Effect (GPE) of ≥ 50% Compared to Baseline., measured over 6 weeks after treatment.

The primary endpoint is the number of patients reaching treatment success six weeks after treatment. Success is defined as a global perceived effect (GPE) of at least 50% compared with baseline. The registry describes GPE as an overall patient-reported assessment of the effect of treatment on pain symptoms, expressed on a scale from 0 % for no improvement to 100 for total improvement, with symptoms gone.

The purpose of an overall perceived-effect measure is to capture a patient’s appraisal that may include aspects beyond pain intensity and physical function. In general, such a measure can reflect how the patient weighs multiple aspects of their experience, rather than recording only one symptom dimension. That broader interpretation also means that the response is subjective and depends on the patient’s own assessment.

The endpoint is a count of participants meeting a defined threshold, rather than a mean change in a continuous score. Its interpretation therefore depends on the number of patients with an observed GPE response and the number assessed at the relevant time point. Neither the success count nor the outcome-specific denominator is reported in the registry record. The primary endpoint’s result, and its precision, cannot therefore be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the study as a retrospective single-center cohort. In general, a retrospective cohort uses records of people who have already received care to describe outcomes after that care. It can characterize what was recorded in the cohort, but without a randomized comparison it does not ensure that groups being compared are similar in all respects. In this record, no comparison arm is described and the allocation method is not stated.

What does a count endpoint represent?

The primary outcome is a count of participants meeting the GPE threshold at six weeks. The registry defines success as a GPE of at least 50% compared with baseline. A count endpoint records whether each assessed participant meets the stated definition; the interpretation also requires the number assessed. In general, a count without its denominator does not show the frequency of the outcome among those evaluated. The record does not report either the primary success count or the outcome-specific denominator.

Thresholding a patient-reported scale can make a clinical definition easier to communicate, but it discards information about the distance between individual scores and the threshold. In general, two cohorts with the same number crossing a threshold could have different underlying score distributions. The registry does not report the GPE responses themselves, so the degree of variation in responses cannot be assessed.

How should uncertainty be understood?

In general, a confidence interval describes a range of values compatible with the data and the method used, and communicates the precision of an estimate. It does not remove limitations from study design, missing observations, or measurement. No confidence interval or other uncertainty estimate for the primary outcome is reported in the registry record. Because the outcome count and denominator are also unreported, the precision of the primary estimate cannot be evaluated from this record.

The same principle applies to other outcomes: an estimate should be read alongside the number of observations contributing to it and an uncertainty measure when available. The registry lists secondary outcome measures but does not report outcome-level estimates or denominators. It is therefore not possible to assess their precision or compare their estimates statistically.

What do the planning assumptions mean?

The registry describes sample-size planning illustrations based on an observed effect, with a two-sided significance level 0.05, equal allocation between two arms, and a normal approximation; the target effect is described as a stated fraction of the observed effect. These are planning assumptions, not evidence that the study had a particular power to detect its findings. A planned sample size is not observed power, and a planning illustration is not the same as the study’s actual design. The record does not report a sample-size justification for the retrospective cohort, nor does it establish that the cohort was allocated equally between comparison arms.

In general, an assumed effect size influences a sample-size calculation: a smaller effect to detect requires more information for the same target operating characteristics, all else equal. A normal approximation is a calculation method, and its suitability depends on the setting and the outcome. The registry does not report the numerical planning outputs or a study-specific rationale that would allow those assumptions to be evaluated against the cohort’s actual data. No new sample-size estimate or power claim can be inferred from the record.

Why does study design matter?

Randomization is one way to balance measured and unmeasured prognostic factors between treatment groups on average. This registry describes a retrospective cohort and does not report randomization or a control arm. General statistical adjustment can address measured factors under suitable assumptions, but the registry record does not describe an adjusted analysis. Even a detailed statistical model would not by itself establish that all sources of confounding had been addressed.

Follow-up and available records also affect estimates. If outcome data are missing, the people with observed results may differ from those without them. In general, missingness can change both the estimated outcome frequency and its uncertainty. The registry does not report missing-data counts, reasons for missingness, or a method for handling missing outcomes. These are important limits when interpreting any outcome estimate, but the outcome estimates themselves 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("Degenerative Knee Pain", "PPSP")
n      <- c(13, 46)
events <- c(4, 15)
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  Degenerative Knee Pain  13  4  30.8  9.1  61.4  12.7  57.6  12.8  58.1
ARM  PPSP  46  15  32.6  19.5  48.0  20.9  47.0  20.9  47.1

11. Multiplicity, Missing Data and Analysis Populations

The registry lists nine secondary outcome measures in addition to the primary endpoint. When a study evaluates multiple outcomes or multiple analyses, the chance of at least one apparently unusual finding can increase if no multiplicity strategy is used. General approaches include identifying a primary outcome in advance, adjusting inference across selected tests, or treating secondary findings as exploratory. The registry record does not report a multiplicity plan, a hierarchy among secondary outcomes, or an adjustment procedure. It is therefore not possible to determine how any secondary-outcome inference was intended to be interpreted.

The registry lists zero analyses. It does not report a statistical analysis plan, the statistical tests or models used, adjusted estimates, or uncertainty estimates. No interim-analysis plan is reported in the registry record. These absences do not establish that no analysis was performed; they mean that the registry record does not describe one.

Outcome-specific missingness is also not reported. The registry does not give the number assessed at each follow-up, reasons for unavailable observations, or a method for handling missing data. It does not state whether analyses used all eligible patients, only patients with complete records, or another analysis population. The enrollment figure alone should not be treated as the denominator for every outcome. Without those details, the representativeness of observed outcomes and the possible influence of missing data cannot be assessed.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: complex regional pain syndrome (crps) (2.2%).

The registry safety fields report serious and other adverse-event counts separately for Degenerative Knee Pain and PPSP. For Degenerative Knee Pain, the serious-event fields list 0 affected among 13 at risk, the other-event fields list 3 affected among 13 at risk, and the death count is 1. For PPSP, the serious-event fields list 1 affected among 46 at risk, the other-event fields list 5 affected among 46 at risk, and the death count is 0. These are the recorded group-specific figures; they should not be combined into a total or treated as comparable treatment groups.

The registry also lists Complex regional pain syndrome (CRPS) as a top serious term at 2.2%. The record does not provide further context for that entry in the registry record, so its relationship to the group counts or the circumstances of the event should not be inferred. The safety counts are descriptive, and the record does not establish that an event was caused by treatment. No randomized control group is described, and allocation is not stated. The safety fields do not, by themselves, quantify comparative risk or show whether a treatment caused, prevented, or changed the likelihood of an event.

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

The study record identifies a clinically focused outcome: patient-reported global perceived effect after conventional radiofrequency treatment for chronic knee pain. It also documents a retrospective review at a single center and lists several secondary outcomes concerning pain, functioning, opioid use, and complications. Those features make the intended questions clear, but they do not supply the outcome results needed to answer them.

The primary outcome count and denominator are not reported in the registry record. No estimate of precision is reported either. The record therefore cannot establish the frequency of six-week treatment success in the analyzed cohort or show how uncertain that frequency might be. The absence of a reported result should not be read as a zero result, and the listed enrollment should not be used as a substitute for an outcome-specific denominator.

Even if cohort outcomes were reported, this design would describe experience in the reviewed patients rather than provide a randomized comparison. The study is retrospective and single-center, no control arm is described, and allocation is not stated. Differences from other populations or settings could affect how well the findings apply elsewhere. The registry also does not report an adjusted analysis or information about missing outcomes, limiting assessment of possible confounding and selection into the analyzed data.

The safety entries document counts in the registry’s group categories, but they cannot establish treatment causality or comparative safety. Likewise, the planning assumptions described in the record do not constitute observed power and do not replace a study-specific sample-size justification. The available record supports describing the design, definitions, and recorded safety counts; it does not support a quantitative conclusion about efficacy or comparative benefit.

14. Why This Trial Matters Statistically

This record illustrates why outcome definitions and outcome results need to be read together. The primary endpoint sets a patient-reported threshold for success at six weeks, but the registry does not report the number meeting it or the number assessed. Without both, readers cannot determine the observed frequency or its precision. An enrollment figure is not a substitute for those outcome-specific details.

It also highlights the difference between a cohort description and a treatment comparison. A retrospective, single-center cohort can describe outcomes among patients seen in that setting. A randomized comparison addresses a different question by using allocation to support comparisons between groups. No randomized comparator is described in this record, and allocation is not stated. These design distinctions shape what statistical claims the data could support, even if outcome results were available.

The record further lists multiple secondary outcomes and safety counts. Multiple outcomes can raise questions about how findings were selected and interpreted, while safety counts require attention to denominators, group definitions, and causal limitations. Here, the registry does not report an analysis plan, missing-data methods, or outcome-level statistical estimates. Those gaps make it important to distinguish registered intentions and recorded counts from inferential evidence.

Finally, planning assumptions are not the same as observed evidence. A sample-size illustration based on an assumed effect and calculation method can inform planning, but it does not show that an effect occurred or establish observed power. Keeping these distinctions explicit helps readers avoid interpreting an incomplete registry record as a definitive estimate of treatment effect.

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 leaves important details unavailable for evaluating this specific cohort. It describes the review period and an exclusion for chronic widespread pain, but does not report the patient-selection flow, the number eligible, or the number with data available at each follow-up. Enrollment is listed as 66, but outcome-specific denominators are not reported. The record therefore does not show whether missing records or follow-up affected the observed data.

The primary result is not reported. The registry does not give the six-week GPE success count, its denominator, or an estimate of uncertainty. Secondary outcome results are also not reported. Although the registry names outcomes related to NRS, physical functioning, strong opioid use, later treatment success, and complications, it does not provide the outcome values or their analysis.

The study is retrospective and single-center. No control arm or random allocation is described, and the allocation method is not stated. The registry does not report adjustment for confounding, a statistical analysis plan, or details of how the recorded data were assessed. It also does not report how missing data were handled or define the analysis populations.

Although adverse-event and death counts are listed by group, the record does not establish causality or provide a randomized comparison. The context for the serious-event term listed as Complex regional pain syndrome (CRPS) is not detailed. The registry also does not report a sample-size justification for this retrospective cohort. Together, these limits mean the record supports a description of the registered design and selected safety entries, but not a quantitative conclusion about treatment effects or comparative safety.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Patients With Chronic Knee Pain Treated With Conventional Radiofrequency of the Genicular Nerves — NCT04234984.
• Registry record last updated 2022-06-14; status last verified 2022-03.
• Results first posted 2022-06-14.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT04234984 is a completed retrospective single-center cohort study sponsored by Ziekenhuis Oost-Limburg. It concerns conventional radiofrequency treatment of the genicular nerves for chronic knee pain. The registry lists enrollment of 66 and gives a study start date of 2020-01-26 and a primary completion date of 2020-11-15. The patient treatment period described in the summary runs from 1 September 2017 to 31 December 2019, with patients with chronic widespread pain excluded.

The primary endpoint is treatment success at six weeks, defined by a GPE of at least 50% compared with baseline. The registry lists nine secondary outcome measures but reports zero analyses. It does not report the primary result, outcome-specific denominators, missing-data methods, or a statistical analysis plan. Safety counts are listed for Degenerative Knee Pain and PPSP, but the retrospective cohort design does not establish causality or comparative effects.