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 Pilot Study to Evaluate The Effectiveness And Safety Of Axiom Worldwide Drx9000™ Spinal Decompression System (NCT00414596), a na phase 2 study. The primary outcome is Post-treatment Numerical Pain Intensity Rating Scale (VRS), Which is a Scale From 0-10 (0=no Pain, 10= Worst Pain).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00414596 |
| Phase | Phase 2 |
| Condition | Low Back Pain |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 20 |
| Arms in the primary outcome | n/a |
| Lead sponsor | NEMA Research, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned patients with chronic low back pain. The registry record lists an enrollment of 20 and identifies low back pain as the condition. Further eligibility details, such as diagnostic criteria or symptom duration requirements, are not reported in the registry record.
Intervention
Participants used the DRX9000™ device. The primary outcome description refers to a standard six-week series of 20 treatments. The registry record identifies the intervention as a device but does not report additional treatment-delivery details in the registry record recorded for this study.
Comparator
No separate control group is described. The study is recorded as single-group, with allocation listed as NA and masking listed as none. Consequently, the registry record does not describe a concurrent comparison against usual care, a sham procedure, or another intervention.
Primary question
The primary endpoint was the post-treatment verbal numerical pain intensity rating scale (VRS) at six weeks, recorded as a median with an inter-quartile range. It asks what pain rating was reported after the treatment series, not how much each participant changed from baseline. The numerical median and inter-quartile range are not reported in the registry record, so the endpoint's observed level cannot be assessed from these registry entries.
This structure makes the study a description of outcomes after device use rather than a controlled estimate of the effect of the device relative to another option. A post-treatment score may be useful for describing the participants' reported pain at the specified assessment, but without a concurrent comparator it cannot establish what would have happened over the same period without the device. The registry record also does not report baseline pain ratings alongside the primary endpoint, so a before-and-after change cannot be determined from the stated primary measure.
3. Trial Design
The registry describes a completed phase 2 pilot study of the Axiom Worldwide DRX9000™ spinal decompression system for chronic low back pain. Its recorded design is single-group, allocation is NA, and masking is none. Enrollment was 20. NEMA Research, Inc. is listed as the sponsor. The recorded study start is 2006-12 and primary completion is 2007-04.
All participants are described within a DRX Group using the device. There is no separate randomized or non-randomized control arm in the registry entries. The allocation entry of NA is consistent with the single-group description; it should not be read as evidence that participants were assigned among competing treatments. Because masking is listed as none, the registry record does not describe blinded assessment or blinded participants.
The primary endpoint was assessed at six weeks after a standard series of 20 DRX9000 treatments. Listed secondary outcomes include recurrence of significant low back pain following treatment, change in functional capacity from baseline to six weeks using the Revised Oswestry Pain Questionnaire, satisfaction with treatment procedures, adverse events following treatment, and study withdrawals. The registry lists 6 outcome measures and 1 analysis. Those counts do not, by themselves, clarify which outcomes were analyzed together or how each outcome was handled.
A pilot study can describe how a treatment protocol was implemented and provide preliminary outcome and safety observations. It does not automatically provide a reliable comparative estimate. The registry record does not report a control group, randomization, a detailed sample-size justification, or enough analysis information to determine whether the enrollment was selected to estimate a particular treatment effect with a specified precision.
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
| Stage | DRX Group |
|---|---|
| STARTED | 20 |
| COMPLETED | 18 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | DRX Group |
|---|---|
| Protocol Violation | 2 |
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 | DRX Group |
|---|---|---|
| Participants analysed | 20 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 20 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age, Continuous | years | 46.6 (SD 15) |
| Sex: Female, Male: Female | Participants | 7 |
| Sex: Female, Male: Male | Participants | 13 |
| Region of Enrollment: United States | participants | 20 |
6. Primary Endpoint
The registry lists the primary outcome as Post-treatment Numerical Pain Intensity Rating Scale (VRS), Which is a Scale From 0-10 (0=no Pain, 10= Worst Pain), measured over Six weeks.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | units on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the post-treatment numerical pain intensity rating on the verbal numerical rating scale (VRS), measured at six weeks. The registry describes the scale as ranging from 0 to 10, with 0 meaning no pain and 10 meaning the worst pain. The result was to be expressed as a median and inter-quartile range, in units on the scale.
In general, a pain rating gives a participant a structured way to report symptom intensity at a defined assessment. The median describes the middle of the observed ratings when ordered; the inter-quartile range describes the spread of the central portion of those ratings. These summaries can be useful when individual ratings are not well represented by a mean, or when the distribution is skewed. The inter-quartile range describes variability among the observed ratings; it is not a confidence interval for the median.
The endpoint is a post-treatment level, not a change from baseline. It therefore does not directly quantify improvement or worsening from each participant's starting rating. The registry record does not report the numerical median, inter-quartile range, or a confidence interval for this endpoint. Without those values, the observed distribution and its precision cannot be assessed. The endpoint also does not, on its own, distinguish an effect of treatment from changes that could occur over time or from other influences.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a relevant descriptive question: what pain ratings were recorded at the six-week assessment after a course of DRX9000 treatment? It specifies the outcome, scale, summary statistic, and assessment time. However, the numerical primary result is not reported in the registry record. There is therefore no posted median or inter-quartile range in the registry record to interpret, and no basis for describing the direction or size of the observed endpoint.
Even if a post-treatment median were available, a single-group result would describe the participants' ratings at that time; it would not establish a treatment effect relative to a comparator. In general, symptoms may change over time for reasons other than the intervention, and participants' expectations or other care may also influence reported outcomes. A concurrent control group can help distinguish treatment-associated differences from such influences. This study's registry description does not include one.
The primary endpoint is also not a baseline-to-follow-up change. The secondary outcomes include a functional-capacity change from baseline to six weeks, but the numerical result for that measure is not reported in the registry record. No baseline VRS value is given with the primary outcome details. As a result, the posted details do not establish whether pain ratings changed during treatment, nor how any change was distributed across participants.
Precision cannot be judged from a median alone. In general, an inter-quartile range conveys the spread of observed values, while a confidence interval conveys uncertainty about an estimated quantity. The registry entries do not include the primary endpoint's numerical inter-quartile range or a confidence interval. They also do not report an analysis population, missing-outcome counts, or a method for handling missing ratings. The enrollment figure should not be mistaken for the number with a recorded primary endpoint.
The safety information is descriptive as well. The registry lists 0 serious adverse events among 20 participants at risk and 8 participants affected in the other adverse-event category, among 20 at risk. These counts do not provide event descriptions or a comparison against another group. They should not be converted into a claim about comparative safety or interpreted as ruling out uncommon harms.
Overall, the record describes the study question and design but does not include the numerical primary outcome result needed to characterize the observed pain ratings. The single-group design would limit causal interpretation even if that result were available. The registry entries support describing the planned endpoint and recorded adverse-event counts, not drawing a conclusion about the device's efficacy.
9. Statistical Methods Explained
Several statistical ideas help clarify what can and cannot be concluded from this study. The explanations below are general; the registry record does not report a full statistical analysis plan.
What does a median with an inter-quartile range describe?
In general, a median is the central observation after values are ordered. It is less affected by unusually high or low observations than an arithmetic mean. The inter-quartile range describes the span between the lower and upper quartiles, giving a sense of the spread of the central part of the data. It describes observed variability, not the precision of the estimated median. A confidence interval is a different summary: in general, it expresses uncertainty about an estimated quantity under the assumptions of the analysis.
For this study, the registry specifies a post-treatment VRS median and inter-quartile range at six weeks. It does not report their numerical values. Thus, the scale and summary method are known, but the endpoint's observed level and spread are not. Nor is a confidence interval for the median reported in the registry record.
Why does the single-group design matter?
In general, an outcome observed after treatment combines any treatment-associated change with the natural course of symptoms, contextual influences, other care, and measurement variability. A single-group study has no concurrent comparator to help separate those influences. A before-and-after comparison can describe change over time, but it is not equivalent to a randomized comparison: the participants' starting measurements do not show what their outcomes would have been without treatment.
Here, the primary endpoint is a post-treatment score, not a baseline-to-follow-up difference. Although a secondary outcome concerns change in functional capacity, its numerical result is not reported in the registry entries. The record does not provide a baseline VRS result with the primary endpoint. It therefore does not support a numerical within-participant change assessment for pain.
How should the planning assumptions be understood?
The sample-size assumptions describe a planning illustration based on an observed effect, rather than the study's own design justification. The stated assumptions include a two-sided significance level of 0.05, equal allocation between 2 arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. For time-to-event calculations, the stated output is the total number of events; for other calculations, it is participants per arm.
These assumptions are not a description of the trial's actual design. The registry describes a single-group study, while the planning illustration assumes allocation between 2 arms. Planning calculations estimate a sample size under specified assumptions; they do not show that a study had a particular probability of detecting an effect after it was completed. Such a probability is sometimes called observed power, but it should not be inferred from a planning illustration. The registry record does not report the trial's own sample-size justification, and no numerical planning outputs are included in the registry record.
Why can over-dispersion matter?
In general, count outcomes may vary more than a simple statistical model expects. This is called over-dispersion. If it is ignored, standard errors can be too small and confidence intervals too narrow, making results appear more precise than they are. Appropriate modeling depends on the outcome, its distribution, and the study design. The registry entries do not identify a count model or report an analysis of over-dispersion, so no claim can be made about whether this issue was assessed. This general point does not establish that over-dispersion occurred in this trial.
What does an analysis count establish?
The record lists 6 outcome measures and 1 analysis. In general, the number of analyses recorded does not by itself specify whether every outcome was included, whether the analysis was descriptive or inferential, which participants were included, or which model was used. To interpret an analysis fully, readers need details such as the estimand, analysis population, handling of missing values, and uncertainty estimates. Those details are not reported in the registry record.
Finally, adverse-event counts are descriptive unless the comparison and follow-up methods support a comparative inference. The registry lists participants at risk and participants affected, but does not provide event-level descriptions in the registry record. Counts of participants affected should not be treated as counts of all events, since a participant can experience more than one event unless the record specifies otherwise. The record does not state whether event counts were analyzed using a particular statistical model.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 6 outcome measures, including the post-treatment VRS primary outcome and secondary measures concerning recurrence, functional capacity, satisfaction, adverse events, and withdrawals. Considering several outcomes raises a general multiplicity issue: the more statistical comparisons made, the greater the chance that at least one result may appear notable by chance. A prespecified hierarchy, adjustment method, or clear separation of primary and exploratory outcomes can help readers understand that risk.
The registry entries identify a primary endpoint and list secondary outcomes, but they do not report a multiplicity adjustment, a testing hierarchy, or enough detail to determine how the outcomes were analyzed. The listed count of 1 analysis does not establish that only one statistical test was performed, nor does it show how the secondary outcomes were handled. The analysis plan and any adjustment for multiple comparisons are not reported in the registry record.
Missing data are also important for interpreting an endpoint. The enrollment is 20, but the number with an observed six-week VRS result is not reported in the registry record. The record does not state how missing ratings, withdrawals, or incomplete follow-up were handled, or whether any sensitivity analysis was performed. The secondary outcomes include the number of patients who withdraw, but no withdrawal result is included in the registry record.
The analysis population is not reported in the registry record. It is therefore unclear which participants contributed to each outcome, whether the analysis included everyone enrolled, or how participants with unavailable measurements were treated. These omissions limit assessment of potential bias and precision; they do not establish that data were missing or that a particular method was used.
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 |
|---|---|---|---|
| DRX Group | 0 | 20 | 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 |
|---|---|
| DRX Group | 8 of 20 |
Most frequent non-serious adverse event terms
| Event term | Organ system | DRX Group |
|---|---|---|
| Head Colds | General disorders | 2 of 20 |
| Sinus Headaches | General disorders | 2 of 20 |
| Neck Pain | Musculoskeletal and connective tissue disorders | 1 of 20 |
| Sinus Infection | Infections and infestations | 1 of 20 |
| Shoulder Pain | Musculoskeletal and connective tissue disorders | 1 of 20 |
| Influenza | Infections and infestations | 1 of 20 |
| Vertigo | Ear and labyrinth disorders | 1 of 20 |
| Adrenal Insufficiency | Endocrine disorders | 1 of 20 |
The registry lists 0 serious adverse events among 20 participants at risk in the DRX Group. It also lists 8 participants affected in the other adverse-event category, with 20 at risk. These are separate category counts: the serious-event count should not be combined with or substituted for the other adverse-event count.
The figures describe participants recorded as affected, not necessarily the total number of individual events. The registry entries do not give event terms, severity details for the other category, timing, or information about whether any events led to withdrawal. Serious adverse-event terms are not listed. The death figure is not reported in the registry record.
In general, an observed count of zero serious events does not prove that serious events cannot occur. A small single-group study can describe what was recorded during its follow-up, but without a comparator it cannot estimate relative safety. The registry entries do not give a comparative safety analysis or enough detail to assess completeness of event reporting. The counts should therefore be read as descriptive observations, not as evidence of a safety advantage or a guarantee of safety.
12. What the Result Does, and Does Not, Mean
This study's registry record describes a completed phase 2 pilot study of a device for chronic low back pain. It identifies a single-group design, a six-week treatment period, and a post-treatment VRS endpoint reported as a median and inter-quartile range. It also lists several secondary outcomes and records adverse-event counts. Those details help define what the study set out to assess.
The primary endpoint's numerical result is not reported in the registry record. Without the median and inter-quartile range, the post-treatment pain ratings cannot be characterized from these registry entries. The registry also does not report a baseline VRS result alongside the primary measure, so the endpoint cannot be interpreted as a demonstrated change from baseline.
Even a numerical post-treatment result from this design would remain descriptive. Because the study has no separate comparator, it cannot isolate the device's effect from other influences on pain ratings. The registry entries also do not provide a reported comparative estimate, confidence interval, or detailed statistical analysis plan. They do not establish that a change was caused by the intervention.
The adverse-event counts are likewise limited: they record 0 serious adverse events and 8 participants affected in the other adverse-event category, but do not give the event descriptions or a comparator. These counts cannot establish comparative safety or exclude harms that were not observed in the study.
Accordingly, the record can be used to understand the study's design, endpoint, and scope, but the registry entries stated do not support a conclusion about treatment efficacy. They also do not provide enough outcome or analysis detail to judge the precision of the primary result. The distinction is between a study that evaluates outcomes after treatment and evidence that estimates what difference the treatment itself makes.
13. Why This Trial Matters Statistically
This trial matters statistically because its design makes the distinction between observing an outcome and estimating a treatment effect especially important. The registry records a single-group pilot, with no masking and no separate comparator. Such a design can document outcomes after a defined treatment course, but it cannot control for changes that might have occurred without the intervention. Readers should therefore separate descriptive findings from causal claims.
The endpoint choice also illustrates the difference between a level and a change. The primary outcome is a VRS rating after six weeks, summarized by a median and inter-quartile range. It is not specified as a change from baseline. A post-treatment level alone does not reveal how participants' ratings compare with their own starting values, and the numerical primary result is not reported in the registry record.
Precision is another important issue. An estimate is more informative when its uncertainty and the spread of observations are available. The registry specifies an inter-quartile range but does not report its numerical value or a confidence interval for the endpoint. The enrollment figure alone cannot substitute for these summaries, and it does not establish how many participants had evaluable endpoint data.
Finally, the record lists multiple outcome measures but does not explain how they were prioritized analytically or how missing data were handled. These details affect how confidently readers can interpret the results. The case underscores why clear reporting of outcome values, analysis populations, uncertainty, and prespecified methods is central to evaluating a clinical study.
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.
The registry record leaves several trial-specific uncertainties. It describes the study as a pilot and single-group, but does not report detailed eligibility criteria, recruitment methods, or the characteristics of enrolled participants beyond the condition. The treatment is described as a six-week series of 20 DRX9000 treatments, but further delivery and adherence details are not reported in the registry record.
The primary endpoint is defined, yet its numerical median and inter-quartile range are not reported in the registry record. The record also does not report a baseline VRS value, a confidence interval, or the number of participants with an observed endpoint. Therefore, neither the endpoint distribution nor its precision can be evaluated from the stated details.
The record does not describe an analysis population, missing-data procedures, or a detailed statistical analysis plan. It lists 6 outcome measures and 1 analysis, but does not explain the analysis methods or how multiple outcomes were treated. A sample-size justification for the actual single-group study is not reported in the registry record. The planning assumptions describe an illustration with equal allocation between 2 arms, rather than the recorded single-group design.
For safety, the registry lists counts but not event terms or detailed follow-up information. It does not report a comparative safety analysis, and the death figure is not reported in the registry record. These limitations constrain interpretation of both outcomes and harms; they do not show that a particular event, bias, or analysis problem occurred.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Pilot Study to Evaluate The Effectiveness And Safety Of Axiom Worldwide Drx9000™ Spinal Decompression System — NCT00414596.
- Registry record last updated 2016-06-06; status last verified 2016-05.
- Results first posted 2016-06-06.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry describes a completed phase 2 pilot study sponsored by NEMA Research, Inc., evaluating the DRX9000™ device for chronic low back pain. The design is single-group, allocation is NA, masking is none, and enrollment is 20. The recorded study start is 2006-12 and primary completion is 2007-04.
The primary outcome is the post-treatment VRS at six weeks, summarized as a median and inter-quartile range on a 0-10 scale. The numerical primary result is not reported in the registry record. Listed secondary outcomes address recurrence, functional capacity, satisfaction, adverse events, and withdrawals.
The registry records 0 serious adverse events among 20 at risk and 8 participants affected in the other adverse-event category among 20 at risk. Event descriptions, the primary endpoint values, analysis-population details, and missing-data methods are not reported in the registry record. The single-group design limits causal interpretation.