This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Efficacy and Cost: Benefit Ratio of 0, 1, and 2 Medial Branch Blocks for Lumbar Facet Joint Radiofrequency Denervation (NCT00484159), a randomized na study. The primary outcome is Cost Per Successful Procedure.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00484159 |
| Phase | NA |
| Condition | Low Back Pain |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 151 |
| Arms in the primary outcome | 3 |
| Lead sponsor | Johns Hopkins University |
| Results posted | Yes |
2. Clinical Question
Population
Patients with chronic low back pain of suspected facet-joint origin. The registry record describes lumbar facet pain as the clinical context and reports an enrollment of 151 participants.
Intervention
A strategy in which radiofrequency denervation was undertaken only after a positive response to two diagnostic facet blocks. The blocks were intended to help identify facet-joint pain before denervation.
Comparator
Two alternative pathways: denervation after a positive response to a single diagnostic block, and denervation without a diagnostic block, based on history and physical examination.
Primary question
What was the total cost per successful treatment at 3 months for each pathway? A successful procedure was defined as at least 50% pain relief and satisfaction lasting at least 3 months.
The trial addresses a choice about how to select patients for lumbar radiofrequency denervation, rather than a comparison of denervation with no denervation. The three groups represent distinct diagnostic and treatment pathways: proceeding without a block, requiring one positive block, or requiring both a positive screening block and a positive confirmatory block. The registry record says that no standard number of diagnostic blocks was established and describes concern about false positive and false negative block results and the cost-benefit balance of using them.
The clinical question therefore combines treatment selection with resource use. A pathway that uses more diagnostic procedures might select patients differently, while also adding costs before denervation. The posted primary outcome is cost per successful procedure at 3 months, and successful treatment is also posted as a secondary outcome. The record does not report a separate question about longer-term pain relief, function, or durability beyond the stated success definition. It also does not report a direct clinical recommendation or a prespecified preferred pathway.
3. Trial Design
This was a randomized, parallel-group study with no masking reported. The registry record lists 151 participants and a completed status. The recorded study dates are 2007-02 for study start and 2009-01 for primary completion. Johns Hopkins University is listed as the sponsor. The phase is recorded as not applicable.
Participants were allocated to one of three approaches to lumbar facet joint radiofrequency denervation. The double-block group received denervation only after positive responses to two diagnostic facet blocks. The single-block group received denervation after a positive response to one block. The radiofrequency group received denervation without a diagnostic facet block, based on history and physical examination. The record also lists 0.5% bupivacaine and 2% lidocaine among the interventions, but does not describe the detailed medication sequence or which agent was used in each pathway.
The posted group sizes were 50 for the double-block group, 50 for the single-block group, and 51 for the radiofrequency group. The primary outcome was cost per successful procedure at 3 months. Successful treatment was also posted as a secondary outcome at 3 months postprocedure. The record does not report the method used to generate the random sequence, allocation concealment, eligibility criteria in detail, or the analysis population. Those design details are not reported in the registry record and should not be inferred from the randomized label alone.
The three arms compare complete care pathways, including whether diagnostic blocks were required before denervation. As a result, differences between groups would represent contrasts among these strategies as implemented, not an isolated estimate of the biological effect of one diagnostic block. The registry record does not provide further operational details about adherence to the assigned pathways or deviations from them.
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: Subjects had to be candidate for facet blocks or radiofrequency denervation. They had to have no neurological symptoms, failed conservative treatment and not had spinal fusion.
Overall Study
| Stage | Double-block Group | Single-block Group | Radiofrequency Group |
|---|---|---|---|
| STARTED | 50 | 50 | 51 |
| COMPLETED | 49 | 49 | 51 |
| NOT COMPLETED | 1 | 1 | 0 |
Reasons for not completing this period:
| Reason | Double-block Group | Single-block Group | Radiofrequency Group |
|---|---|---|---|
| Lost to Follow-up | 1 | 1 | 0 |
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.
| Characteristic | Unit | Double-block Group | Single-block Group | Radiofrequency Group | Total |
|---|---|---|---|---|---|
| Participants analysed | 50 | 50 | 51 | 151 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 44 | 44 | 45 | 133 |
| Age, Categorical: >=65 years | Participants | 6 | 6 | 6 | 18 |
| Sex: Female, Male: Female | Participants | 23 | 24 | 20 | 67 |
| Sex: Female, Male: Male | Participants | 27 | 26 | 31 | 84 |
6. Primary Endpoint
The registry lists the primary outcome as Cost Per Successful Procedure, measured over 3-months.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | U.S. dollars |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled “Cost Per Successful Procedure.” It measures the total cost per effective treatment at 3 months. The record defines a successful procedure as achieving at least 50% pain relief and satisfaction lasting at least 3 months. The endpoint is intended to put resource use in the context of treatment success: it is not simply the cost of a block or the cost of denervation considered alone.
The posted values were U.S. dollars 15,240 for the double-block group, U.S. dollars 17,140 for the single-block group, and U.S. dollars 6,286 for the radiofrequency group. These are the registry’s reported group values. No dispersion measure, confidence interval, or inferential comparison for these cost figures is reported in the registry record. Therefore, the values describe the recorded cost-per-successful-procedure outcome, but do not by themselves show how variable the estimates were or how precisely the groups differ.
This kind of endpoint is used when a decision involves both outcomes and costs. Its interpretation depends on the definition of success, the cost components included, and the time horizon. The registry record supplies the success definition and a 3-month timeframe, but does not describe the costing methods or itemized components. The endpoint should therefore be read as the posted cost measure under the registry’s definition, not as a complete estimate of costs across other settings or longer periods.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry reports cost-per-successful-procedure values of U.S. dollars 15,240 in the double-block group, U.S. dollars 17,140 in the single-block group, and U.S. dollars 6,286 in the radiofrequency group. These values describe the posted primary outcome at 3 months. No uncertainty estimates or primary statistical comparisons are reported alongside them. It is not possible from these figures alone to determine the precision of the cost estimates or whether apparent differences are compatible with substantial sampling variation.
The secondary successful-treatment outcome gives additional clinical context. The registry records 9 successful treatments among 50 participants in the double-block group, 7 among 50 in the single-block group, and 17 among 51 in the radiofrequency group. The posted unadjusted comparison between the single-block and double-block groups has a p-value of 0.585. The comparison between the radiofrequency and double-block groups has a p-value of 0.078. These are unadjusted results, and the registry record does not report sponsor analyses for this outcome.
The reported risk-difference intervals for both comparisons include zero. That means the estimates are compatible with no risk difference as well as with differences in either direction within the respective intervals. The point estimates and p-values should not be treated as proof that the strategies are equivalent or that a difference is established. In particular, a p-value is not the probability that the treatment strategies are the same, and it does not indicate the size or practical importance of an effect.
The primary endpoint and the secondary outcome answer related but different questions. The primary outcome combines costs with the registry’s definition of a successful procedure. The secondary outcome records successful-treatment counts. The registry does not supply enough detail about cost construction to derive the primary values independently from the success counts, nor does it report uncertainty around the primary cost outcome. The posted findings therefore support a descriptive reading of the group results, while leaving uncertainty about precision and the strength of comparative evidence.
These data do not establish that one pathway is preferable for every clinical or economic context. The comparison is limited to the recorded participants, the posted definitions, and the 3-month outcome horizon. The registry record does not provide longer-term results or a complete analysis plan that would clarify how the primary outcome was compared or how the secondary analyses were intended to be interpreted.
9. Statistical Methods Explained
Three kinds of statistical information are relevant to interpreting this study: the posted cost outcome, the secondary counts of successful treatment, and planning illustrations based on observed effects. They answer different questions and should not be conflated. The cost outcome is reported as a group-level value without a measure of variability. The secondary outcome is a count of participants meeting the success definition. The planning figures describe hypothetical sample sizes under stated assumptions; they are not evidence about the actual power of the completed trial.
What does a risk difference describe?
A risk difference compares the proportion with an outcome in one group with the proportion in another. A value of zero corresponds to no difference in the proportions. Positive and negative values indicate opposite directions, depending on which group is subtracted from which. The posted secondary comparisons use risk differences, with the double-block group as the reference. The reported interval estimates for both comparisons include zero, so the data are compatible with no difference as well as with nonzero differences across the intervals.
A confidence interval expresses the range of effect estimates compatible with the data and the statistical method used, under its assumptions. It provides information about precision that a point estimate alone cannot convey. An interval that includes zero does not prove equality; it indicates that the data do not rule out zero difference at the interval’s stated confidence level. The registry record does not give a confidence level in the narrative description, so no level should be assumed beyond what is available in the posted comparison output.
How should the p-values be read?
The posted unadjusted p-values for the secondary comparisons are 0.585 for single-block versus double-block and 0.078 for radiofrequency versus double-block. A p-value measures how unusual results at least as incompatible with a no-difference model would be under that model and the test’s assumptions. It does not measure the probability that the no-difference model is true, and it does not quantify clinical importance. Because these results are unadjusted, they should be interpreted cautiously, particularly when multiple group contrasts are considered. The record does not describe a prespecified testing hierarchy or a multiplicity adjustment.
The p-values are secondary calculations rather than analyses reported by the sponsor in the registry record. The registry lists no reported analyses for the secondary outcome. Accordingly, these calculations are useful as descriptive statistical context but cannot substitute for a complete sponsor analysis with documented methods, analysis populations, and missing-data handling.
What do the planning illustrations mean?
The registry includes sample-size planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The requested effect is set to the observed effect or a stated fraction of it. For radiofrequency versus double-block, the illustrations give 127 participants per arm for 80% power and 169 for 90% power when planning for 100% of the observed effect; 214 and 286 when planning for 75% of the observed effect; and 455 and 609 when planning for 50% of the observed effect.
For single-block versus double-block, the corresponding illustrations are 1,318 and 1,764 participants per arm when planning for 100% of the observed effect; 2,402 and 3,215 when planning for 75% of the observed effect; and 5,537 and 7,411 when planning for 50% of the observed effect. These values are hypothetical planning requirements under the stated assumptions. They are not the trial’s original design justification, and they are not observed power. The registry record does not report the trial’s own sample-size assumptions or justification. Planning from an observed effect can also be unstable, because the observed estimate is subject to sampling variation.
Over-dispersion is a general concern when outcomes vary more than a simple statistical model assumes. If it is present and ignored, standard errors may be too small and intervals too narrow. The posted secondary outcome is binary, and the registry does not report an over-dispersion assessment or a model-based analysis. The key limitation is therefore not evidence that over-dispersion occurred, but that the record does not document a formal analysis model or its assumptions.
What is missing from the statistical record?
The record does not report a primary-outcome hypothesis test, confidence interval for cost, adjustment method, analysis population, or approach to missing outcome data. It also does not report interim analyses or a detailed prespecified statistical plan. These absences limit how much can be inferred about confirmatory testing and precision. The posted group summaries remain informative descriptions, but they do not supply the full inferential framework needed to interpret them as a complete statistical analysis.
10. Multiplicity, Missing Data and Analysis Populations
The study has three randomized groups, and the posted secondary comparisons contrast two groups with the double-block group. Considering multiple comparisons raises a multiplicity question: if several hypotheses are tested, the chance of at least one apparently unusual result can increase. The registry record does not report a prespecified testing hierarchy, a family of primary contrasts, or an adjustment for multiple testing. No multiplicity correction should therefore be assumed.
The primary endpoint is reported through group-level cost values, but no confidence intervals, dispersion measures, or inferential comparison are reported in the registry record. The secondary outcome has two posted unadjusted comparisons and no sponsor-reported analyses listed. The record does not say whether these comparisons were planned in advance. This distinction matters because an analysis chosen after seeing the data has a different evidential status from a prespecified confirmatory analysis.
Missing-data handling and analysis populations are also not reported in the registry record. The posted group denominators are 50, 50, and 51 for the primary outcome and secondary outcome, but the record does not explain whether all randomized participants contributed data, how unavailable outcomes were handled, or whether any participants were excluded from an analysis. No assumptions about imputation, complete-case analysis, or intention-to-treat analysis can be made.
The registry record also does not report an interim-analysis plan, stopping rules, or a detailed statistical analysis plan. These omissions do not show that such procedures were absent from the study; they mean that they are not documented in the registry record. Without this information, readers cannot determine whether the posted analyses correspond to the planned analyses or how all outcome and comparison decisions were handled. The cost values and secondary counts remain descriptive, but the record does not support a full assessment of confirmatory inference.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Double-block Group | 0 | 50 | 0.0% |
| Single-block Group | 0 | 50 | 0.0% |
| Radiofrequency Group | 0 | 51 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Double-block Group | 0 of 50 |
| Single-block Group | 0 of 50 |
| Radiofrequency Group | 0 of 51 |
The registry reports zero serious adverse events and zero other adverse events in each group: the double-block group had 50 participants at risk, the single-block group had 50, and the radiofrequency group had 51. No serious adverse event terms are listed. Death counts are not reported in the registry record.
These entries describe what was recorded for the adverse-event categories and group denominators. A count of zero does not establish that no harm occurred, and it does not show that the strategies have identical safety profiles. Rare events may not appear in a study of this size, and the registry record does not describe the method or duration of adverse-event surveillance, event definitions, or completeness of reporting. The safety figures should therefore be read as registry-reported counts, not as a comprehensive estimate of risk.
The record’s adverse-event information is separate from the cost and treatment-success outcomes. It does not provide detailed event narratives or a comparison with a formal statistical analysis. Readers should avoid drawing conclusions about relative safety from zero recorded events alone, particularly when the reporting and follow-up procedures are not described.
12. What the Result Does, and Does Not, Mean
The results describe a randomized comparison of three pathways to lumbar radiofrequency denervation: proceeding after two positive diagnostic blocks, after one positive block, or without a diagnostic block. The registry posts group values for cost per successful procedure at 3 months and counts for successful treatment. The costs are descriptive values without reported uncertainty estimates, while the secondary comparisons are unadjusted and lack sponsor-reported analyses in the record.
These findings do not establish that any pathway is universally preferable. Cost-per-successful-procedure values depend on how costs were defined and measured, and the record does not provide an itemized costing method. The success outcome combines pain relief and satisfaction sustained for the stated period. The posted results do not provide separate component outcomes or follow-up beyond the 3-month timeframe.
The study’s randomized design is relevant to comparing assigned strategies, but important details about sequence generation, allocation concealment, analysis populations, and missing data are not reported in the registry record. The absence of those details limits assessment of how the trial was conducted and how the posted results should be interpreted. Similarly, the record does not provide a reported primary statistical comparison for the cost outcome or a full analysis plan for the secondary outcome.
The appropriate interpretation is therefore bounded: the registry gives observed group summaries and unadjusted secondary comparisons, but does not provide enough statistical or costing detail to establish the precision, robustness, or broader economic meaning of the primary values. The results should not be treated as proof of equivalence, proof of a causal mechanism for blocks, or a general rule for treatment selection. They describe outcomes under the study’s recorded pathways and definitions.
13. Why This Trial Matters Statistically
This trial is statistically notable because it compares complete diagnostic-treatment pathways rather than isolating one procedure from the rest of care. The decision to use no block, one block, or two blocks can affect both who proceeds to denervation and the resources used along the way. A cost-per-successful-procedure endpoint reflects that joint question, while the secondary success outcome gives a separate view of treatment results.
The comparison also illustrates why point estimates need uncertainty information. The registry reports cost values but no variability or confidence intervals for them. Without those measures, the apparent ordering of group values cannot show how precisely each cost was estimated or how stable the comparisons might be. The secondary outcome includes unadjusted comparisons, but the registry record does not document a full analysis plan or sponsor-reported inferential analysis.
The planning illustrations are another useful statistical distinction. They show how hypothetical sample-size requirements change when the effect to detect is reduced to a fraction of the observed effect. They are not the original trial’s design justification and cannot be read as observed power. Keeping planning calculations separate from evidence about the completed study prevents a common misinterpretation of sample-size information.
Finally, this record demonstrates the importance of reporting methods alongside results. Randomization and group summaries are useful, but details about missing data, analysis populations, cost construction, and multiplicity are needed to evaluate the strength and scope of conclusions. The study’s central statistical question is not only which group has a lower posted cost value, but also how reliably that value represents the underlying strategy and how it relates to the clinical definition of success.
14. 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.
Several limitations are specific to the information recorded for this trial. The primary cost outcome has no reported dispersion measure, confidence interval, or inferential comparison. The registry gives cost-per-successful-procedure values, but does not describe the cost components, perspective, or detailed costing method. That leaves uncertainty about how the values were constructed and how transferable they are to other settings.
The secondary successful-treatment outcome is accompanied by unadjusted comparisons, while no sponsor-reported analyses are listed. The record does not say whether the comparisons were prespecified or whether multiplicity was considered. It also does not provide a detailed statistical analysis plan, analysis population, or approach to missing data. These omissions limit assessment of the intended analyses and of whether all randomized participants contributed to each result.
The registry record reports no masking and does not give details of random-sequence generation or allocation concealment. It does not report longer-term outcome results beyond the stated 3-month timeframe, or separate results for pain relief and satisfaction. The adverse-event entries are limited to zero counts in the listed categories; surveillance details and death counts are not reported in the registry record.
These limitations concern what can be assessed from the registry record and do not establish that unreported procedures or analyses were not performed. They do mean that the posted summaries alone cannot answer questions about long-term durability, detailed economic assumptions, or the robustness of comparative effects.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Efficacy and Cost: Benefit Ratio of 0, 1, and 2 Medial Branch Blocks for Lumbar Facet Joint Radiofrequency Denervation — NCT00484159.
- Registry record last updated 2011-07-26; status last verified 2009-01.
- Results first posted 2011-07-21.
- 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.
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18. Record Summary
NCT00484159 is a completed randomized, parallel-group study sponsored by Johns Hopkins University. The registry reports no masking and an enrollment of 151 participants. It compares lumbar radiofrequency denervation after two diagnostic facet blocks, after one block, or without a diagnostic block.
The primary outcome is cost per successful procedure at 3 months, with success defined as at least 50% pain relief and satisfaction lasting at least 3 months. The registry posts cost values for all three groups but no uncertainty estimates or primary inferential comparison. Successful treatment is the posted secondary outcome; the record includes group counts and unadjusted comparisons, with no sponsor-reported analyses listed.
The record does not report a detailed statistical analysis plan, missing-data approach, analysis populations, cost construction, or longer-term results. The posted findings are best read as group summaries with limited documented inferential detail.