Study to Investigate the Long Term Survivorship of Coflex: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study to Investigate the Long Term Survivorship of Coflex (NCT02918669), a na na study. The primary outcome is Number of Participants With Radiographic Analysis of Evidence of Fracture or Healing Based on CT Scan.

2. Clinical Question

This is a focused follow-up question about imaging findings in a selected group, rather than a comparison of treatment groups. The study description links eligibility for the CT assessment to a fracture observation at 24 months in the earlier coflex IDE Study. The primary outcome is a participant count based on radiographic analysis of evidence of fracture or healing. The record does not report how many participants had either finding, the detailed criteria used to classify the images, or how uncertain or equivocal observations were handled. It also does not state whether fracture and healing were treated as mutually exclusive categories. Accordingly, the registry record identifies the clinical question and the planned assessment, but it does not provide the numerical findings needed to describe the distribution of imaging outcomes.

3. Trial Design

The registry record describes a completed, single-group study with an enrollment of 12. The participants had received the coflex device in the Paradigm Spine coflex IDE Study and had a spinous process fracture identified at 24 months by an independent radiographic review lab. They were to undergo CT scanning after 60 months to assess for evidence of fracture or healing. The study’s primary completion date is 2017-05-26, and its status is listed as completed.

This design is observational at the follow-up stage: the listed intervention is a CT scan, and the record does not describe a new treatment assignment. There is no randomized comparison or concurrent control group. The record lists allocation as NA, masking as NONE, and the model as SINGLE GROUP. These features mean the study is structured to describe imaging findings in the selected follow-up group, not to estimate a comparative effect between assigned treatments.

The study is a sub-analysis of 24-month spinous process fractures from the earlier IDE Study, with CT assessment after 60 months. The registry record does not report the criteria for selecting participants beyond the described fracture finding, whether all eligible participants completed the CT scan, or how many scans were evaluable. It also does not report additional operational details such as scan acquisition procedures, image-reading rules, or the handling of missing or uninterpretable scans. Those details should not be inferred from the study title or summary.

The phase is listed as NA. A statistical analysis plan, a sample-size justification for this single-group follow-up study, and interim analysis information are not reported in the registry record. The record lists four outcome measures and no analysis records. Therefore, the design and intended assessment can be described, but the planned inferential approach and the numerical results cannot be reconstructed from the registry entry.

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

Analysis population for the primary outcome, as defined in the registry: To examine the long-term survivorship via CT Scan of the coflex in patients who presented with spinous process fractures at 24 months in the Paradigm Spine coflex IDE Study.

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: Patients who presented with spinous process fractures at 24 months in the Paradigm Spine coflex® IDE Study.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Radiographic Analysis of Evidence of Fracture or Healing Based on CT Scan, measured over Post-60 Months.

The primary endpoint is the number of participants with radiographic analysis of evidence of fracture or healing based on CT scan at the post-60-month assessment. Its unit is participants, and the record describes the assessment as applying to coflex patients with radiographic observations of spinous process fracture at post-24 months. In practical terms, the endpoint is a count of people whose CT images are assessed for these findings, rather than a measurement of the size of a fracture or a time-to-event outcome.

A participant count is useful for a focused imaging follow-up because it can describe how many members of the selected group have a particular radiographic finding at the specified assessment. The endpoint’s categories—evidence of fracture or of healing—are relevant to the stated long-term survivorship question. However, a count alone does not convey the details of each image, the severity or extent of a finding, or changes in an individual participant’s imaging over time.

The record does not report the observed count, the denominator with completed and evaluable CT scans, or separate counts for fracture and healing. It does not state whether those findings could overlap or how indeterminate readings were classified. Without those details, the endpoint’s definition is clear at a high level, but its observed distribution and precision cannot be described. A numerical primary endpoint result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record defines the primary outcome as a count of participants with radiographic analysis of evidence of fracture or healing based on CT scan. The unit is participants, and the assessment is specified for the post-60-month timeframe. These features distinguish a descriptive count endpoint from outcomes such as a continuous measurement or the time until an event. The record does not report an analysis method for this endpoint, so no particular statistical test or model should be attributed to the study.

What does a participant count convey?

A count describes the number of people classified with an outcome. To interpret such a count fully, readers generally need both the count and the number of people whose outcomes were assessed. If some enrolled participants did not undergo imaging, or if scans could not be interpreted, the enrolled number alone would not necessarily be the correct denominator for an observed percentage. The registry record lists enrollment as 12, but does not report the number with completed and evaluable post-60-month CT scans or the primary outcome count.

When a count is converted to a proportion, the denominator must match the outcome assessment being described. That proportion can help communicate frequency, but it does not remove uncertainty, especially when the group is small. A confidence interval is a statistical range expressing the precision of an estimate under a stated method and assumptions. It does not guarantee that the true value lies in the range, and its interpretation depends on how the estimate and interval were calculated. No interval or other uncertainty estimate for the primary endpoint is reported in the registry record.

Why does the single-group design matter?

A single-group study can summarize findings among the participants followed, but it cannot directly estimate a contrast against a concurrent control group. A treatment comparison usually depends on defining groups and estimating how their outcomes differ, with uncertainty around that contrast. The registry record lists a SINGLE GROUP model and does not describe a comparator arm. Thus, comparative statistics are not part of the stated design. The fact that participants previously received coflex in an IDE Study does not create a control group within this follow-up study.

The cohort is selected based on a fracture observation at 24 months. This selection defines the population to which the follow-up description pertains. It also means that the findings, if available, would not be a general summary of imaging for every participant who received coflex. The registry record does not report how many people in the earlier study met the follow-up eligibility criteria, how many were invited, or whether the enrolled group represents all eligible people.

What information is needed to assess missing outcomes?

Missing-data assessment starts with knowing how many participants were expected to have an outcome, how many were assessed, and why any assessments were unavailable. The reasons can matter because missingness may be related to participant characteristics or outcomes. For example, if the likelihood of having a scan differs according to health status, the observed participants may not represent everyone eligible for follow-up. This is a general statistical concern, not a claim that such a pattern occurred in this study. The registry record does not report scan completion, reasons for missing scans, or a method for handling missing outcomes.

Image interpretation also introduces classification questions. A prespecified reading process can help make outcome classifications consistent, and independent assessment can reduce some forms of subjectivity. Here, the record identifies an independent radiographic review lab for the 24-month fracture identification, but it does not state who read the post-60-month CT scans, whether readers were blinded to prior findings, or how disagreement or uncertain findings were addressed. These details are not reported in the registry record and should not be assumed.

What can be said about inferential methods?

The registry record lists no analysis records and does not report a primary statistical analysis plan, hypothesis test, confidence interval, adjustment strategy, or interim analysis. Therefore, a p-value or a model-based estimate cannot be reconstructed from the record. Statistical significance is a property of a specified analysis and its assumptions; it is not a substitute for the observed outcome count or for evaluating uncertainty and study design. In this instance, no inferential result for the primary endpoint is reported.

General planning calculations based on an observed effect are distinct from the analysis of trial outcomes. The recorded planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect set as a stated fraction of the observed effect. Those are hypothetical planning assumptions, not evidence that this single-group study was designed with two arms. They do not represent observed power, and they should not be interpreted as the study’s own sample-size justification. The registry record does not report that justification.

In general, over-dispersion occurs when count variability exceeds what a chosen statistical model expects; if ignored, uncertainty estimates can be too small. That concept is not a finding about this study. The primary endpoint is described as a participant count, and the record does not report a count model or provide data with which to assess dispersion. More broadly, statistical methods can only be evaluated when the outcome data, analysis population, and model details are available. Those elements are not reported for the primary outcome 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("Coflex")
n      <- c(8)
events <- c(8)
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  Coflex  8  8  100.0  63.1  100.0  67.6  100.0  66.4  99.7

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists four outcome measures, but it does not report their numerical results or identify a full set of analysis details. It lists no analysis records. A multiplicity plan describes how a study handles the increased chance of false-positive findings when several hypotheses or outcomes are tested. The record does not report whether outcomes were organized into primary and secondary testing families, whether any adjustment was planned, or whether formal hypothesis tests were conducted. No multiplicity method should be inferred.

The primary outcome is described as the number of participants with CT evidence of fracture or healing at post-60 months. The record does not report the observed count or the number of participants with an evaluable scan. It also does not report missing-data rules, reasons for absent scans, or an analysis population. These omissions prevent assessment of whether the recorded enrollment of 12 corresponds to the number included in the primary analysis. They also prevent assessment of possible bias from missing or uninterpretable imaging.

General approaches to missing outcomes include describing completeness, documenting reasons, and stating how analyses handle unavailable measurements. The appropriate approach depends on the pattern and cause of missingness, which cannot be assessed without details. The registry record does not state whether any missing-data sensitivity analyses were performed. It also does not report a prespecified statistical analysis plan or interim analyses. Accordingly, neither the handling of multiplicity nor the handling of missing data can be evaluated from the registry record.

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

The record describes a CT follow-up assessment of a selected group: participants who received coflex in the IDE Study and had a spinous process fracture identified at 24 months. The intended primary assessment was for evidence of fracture or healing after 60 months. These details define the study’s question and target group. They do not, by themselves, say what the CT scans showed.

The primary endpoint result is not reported in the registry record. As a result, it is not possible to state the number of participants with evidence of fracture or healing, the proportion of the assessed group with either finding, or the precision of such an estimate. The enrollment of 12 is not a substitute for the missing outcome count or a reported denominator of evaluable scans.

Even if the numerical imaging findings were available, a single-group follow-up would describe this selected cohort rather than provide a direct comparison with a control group. It would not, by itself, establish what would have happened under a different treatment or in participants without a 24-month fracture observation. It also would not determine whether a radiographic finding caused symptoms or had a particular clinical consequence; such information is not reported in the registry record.

The registry status is completed, but completion status is distinct from complete reporting of outcomes. The record lists no analysis records, and details about missing scans, image classification, and the statistical analysis are not reported. The adverse-event summary entries list zeros in their fields, but the record does not provide explanatory details. These limitations mean the registry entry supports a description of the intended follow-up assessment, not a conclusion about the observed primary outcome or its clinical implications.

13. Why This Trial Matters Statistically

This study illustrates how a narrow follow-up question can differ from the broader treatment question readers may associate with a device study. The focus is on CT findings in participants with a spinous process fracture identified at 24 months, not on a randomized comparison of coflex with another treatment. Keeping the target population and design explicit helps prevent a descriptive imaging assessment from being read as a comparative treatment evaluation.

It also highlights the importance of reporting the denominator alongside a participant count. Enrollment of 12 establishes the recorded size of the follow-up study, but readers need to know how many participants had an evaluable scan and how their findings were classified. Without those details and the outcome count, neither the observed frequency nor its statistical precision can be assessed.

The registry entry records the assessment timeframe and a clear high-level endpoint, yet no primary result or analysis record is reported. This distinction matters: a completed study designation does not itself provide evidence about the endpoint. Statistical interpretation depends on outcome data, a defined analysis population, and methods that make uncertainty and missingness assessable. The record does not report those elements for the primary result.

Finally, the entry underscores the limits of planning calculations when they are detached from the actual design and results. Hypothetical assumptions involving two arms are not a description of this single-group study, and a planning illustration is not observed power. For statistical readers, separating design, planning, and outcome reporting is essential to avoid assigning evidentiary meaning to information that does not answer the stated clinical question.

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 primary limitation for interpretation is that the numerical result for the primary endpoint is not reported in the registry record. The record also does not state how many of the 12 enrolled participants completed the CT scan or had evaluable images. Without an outcome count and its denominator, the frequency of fracture or healing findings and the precision of any estimate cannot be assessed.

The study has a single-group design and no concurrent comparator. Its participants were selected because they had a fracture observation at 24 months in the earlier IDE Study. Thus, any imaging description would apply to this selected follow-up group and would not itself provide a comparative estimate for other treatments or for all coflex recipients.

Important procedural details are not reported in the registry record, including post-60-month image-reading procedures, classification rules, and the handling of equivocal readings. The record does not describe missing-data methods, an analysis population, a statistical analysis plan, or interim analyses. It also does not report a sample-size justification for this follow-up study. These gaps limit assessment of potential selection, measurement, and analysis issues.

The registry lists four outcome measures but no analysis records. The adverse-event summary contains zero-valued fields, without further event detail that would clarify their interpretation. Together, these reporting gaps mean the record is informative about the study’s purpose and design, but limited for evaluating the observed imaging outcomes, statistical uncertainty, and safety information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Study to Investigate the Long Term Survivorship of Coflex — NCT02918669.
• Registry record last updated 2020-02-24; status last verified 2020-02.
• Results first posted 2019-07-08.
• 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.

18. Record Summary

NCT02918669 is listed as a completed, single-group study titled “Study to Investigate the Long Term Survivorship of Coflex.” Its official title identifies a sub-analysis of 24-month spinous process fractures using CT scans after 60 months. The registry record lists an enrollment of 12, a primary completion date of 2017-05-26, and Paradigm Spine as sponsor.

Participants had received coflex in the IDE Study and had a spinous process fracture identified at 24 months by an independent radiographic review lab. The listed intervention was CT scanning. The primary outcome was the number of participants with radiographic analysis of evidence of fracture or healing at post-60 months.

The registry record lists four outcome measures and no analysis records. It does not report a numerical result for the primary endpoint, the number with evaluable scans, or the statistical analysis details. The study is a selected-group imaging follow-up, not a randomized treatment comparison.