Prospective, Multi-Center Clinical Outcomes Study Evaluating the chronOS Strip Combined With Bone Marrow Aspirate: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Prospective, Multi-Center Clinical Outcomes Study Evaluating the chronOS Strip Combined With Bone Marrow Aspirate (NCT00943384), a na na study. The primary outcome is Posterolateral Fusion Success.

2. Clinical Question

The study was designed to evaluate posterolateral fusion rates in a prospective series of patients with degenerative disc disease. The surgical procedure combined instrumented posterolateral fusion with interbody support, while the chronOS Strip, bone marrow aspirate and local bone were applied to the posterolateral gutters. This describes the treatment setting and the endpoint question; it does not establish how the device compares with an alternative.

The registry also lists patient-reported outcomes, including the Oswestry Disability Index, back pain and leg pain on a visual analog scale, and the physical component summary of the Short Form 12. These are secondary outcomes, distinct from the radiographic and hardware-based composite primary endpoint. Their numerical results are not reported in the registry record.

3. Trial Design

This was a prospective, multi-center, single-group clinical outcomes study, described in the registry summary as a clinical case series. The study status is completed, and enrollment is listed as 104. The study began in 2009-07, with primary completion in 2013-10. The condition listed is degeneration of the lumbar intervertebral disc.

The sole intervention arm was chronOS Strip. Participants underwent instrumented posterolateral fusion with interbody support; the device combined with bone marrow aspirate and local bone was placed in the posterolateral gutters. The registry describes the intended study population as patients with degenerative disc disease, with or without stenosis, undergoing interbody fusion and use of a posterolateral pedicle screw system.

Allocation is listed as NA, masking as none, and the study model as single group. These entries are consistent with a design that has no randomized allocation and no masking. Since there is no comparator arm, observed outcomes would describe participants treated within this study rather than an estimated treatment contrast against a concurrent control group. Differences from another treatment or from outcomes under usual care cannot be inferred from this design alone.

The primary endpoint was assessed at Month 24 in the per-protocol population. The record states that 55 patients were evaluated at that visit and that six lacked complete radiographic data needed for primary endpoint evaluation. It does not report the primary endpoint count or rate, the size or reasons for any other exclusions, or a participant flow accounting from enrollment through analysis.

The record lists 11 outcome measures and zero analyses. Phase is recorded as NA. The protocol's sample-size justification, planned interim analyses, and detailed statistical analysis plan are not reported in the registry record. A study-design label or completed status does not fill in those missing details, nor does it imply that every enrolled participant contributed to every endpoint.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The primary endpoint was evaluated for the per-protocol population. Of the 55 patients who were evaluated at the Month 24 visit, six patients were missing complete radiographic data needed to evaluate the primary endpoint.

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: Number of subjects treated per protocol

6. Primary Endpoint

The registry lists the primary outcome as Posterolateral Fusion Success, measured over Month 24.

The primary endpoint is posterolateral fusion success at Month 24. It is a binary composite: each participant is classified as successful only if all four components are successful at every investigated level. The listed components concern posterior bridging bone, intersegmental motion assessed through angular and translational motion, and posterior hardware status. Failure on any one component means the participant does not meet the composite definition of successful posterolateral fusion.

A composite endpoint can combine several features of the clinical or imaging assessment into one classification. In general, this can represent a broader outcome than any single component, but it also means the overall classification depends on every component and the rule used to combine them. Under this endpoint's all-components requirement, an individual component failure is enough to classify the overall endpoint as unsuccessful. The composite result would not, by itself, show which component most often determined the classification; component-specific counts would be needed for that interpretation.

The endpoint is used to summarize fusion status under a prespecified-style operational definition, rather than treating one imaging or hardware finding as sufficient on its own. However, the registry record does not report a primary endpoint result or component-level results. It therefore gives the definition and assessment time but not the observed number of successes, the corresponding rate, or the precision of that estimate.

The primary endpoint population is described as per-protocol. Of 55 patients evaluated at Month 24, six were missing complete radiographic data required to evaluate it. The record does not state how those cases were handled in the endpoint analysis or provide the final endpoint denominator.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary because each participant's composite fusion status is classified as success or failure. The record identifies the outcome unit as participants and describes the result type as a number of participants with an event. In general, a binary outcome can be summarized by counting participants in each category and, when the appropriate denominator is available, reporting the proportion in each category. The registry record does not report the primary endpoint count or denominator used for that calculation.

The composite rule requires success on all four components at all investigated levels. This is an all-or-none rule: one failed component at one investigated level is sufficient for an overall failure classification. In general, composite outcomes can capture multiple dimensions in a single endpoint, but their interpretation depends on the components and combination rule. The overall result would not identify the contribution of each component unless component-specific results were also reported. Those results are not reported in the registry record.

The listed primary endpoint population is per protocol. In general, a per-protocol analysis concerns participants who satisfy protocol-defined criteria for analysis, but the exact criteria vary by study and cannot be inferred from the label. The record does not report the criteria used to define this population, the count included in the final primary analysis, or all reasons for exclusion. It notes that 55 patients were evaluated at Month 24 and that six lacked complete radiographic data for endpoint evaluation. The treatment of those missing endpoint assessments is not reported.

Missing outcome data matter because a participant without an evaluable endpoint cannot automatically be classified as either a success or a failure unless the analysis rule explicitly does so. In general, excluding participants with missing assessments can change the analyzed population, while assigning a value can introduce assumptions about their outcomes. Different approaches can produce different estimates. The registry record does not describe an approach for handling the six incomplete radiographic assessments or any sensitivity analyses addressing missing data.

For a binary estimate, uncertainty depends in part on the number of participants contributing to the estimate and the observed distribution of outcomes. In general, a confidence interval communicates a range of estimates compatible with the data under a chosen method and assumptions; it is not a guarantee that the true value lies within that interval. The registry record does not report a primary outcome estimate or confidence interval. It therefore is not possible to assess precision or compare the estimate with a threshold using the record information described.

Allocation is listed as NA and the study model as single group, with no masking. These are design features rather than statistical tests. In general, a single-group study can describe outcomes observed after an intervention, but cannot directly estimate a randomized between-group treatment contrast. Differences between a study cohort and an external population or historical experience could reflect differences in participant selection, treatment setting, follow-up, outcome ascertainment, or other factors. No external comparison is reported in the registry record.

There is no statistical analysis plan in the registry record that specifies the primary analysis method, model, handling of multiple levels within a participant, or adjustment for other variables. The endpoint definition refers to all investigated levels, but the record does not provide a statistical method for accounting for any within-participant structure. These details should not be presumed from the endpoint description alone.

The study lists 11 outcome measures, including the primary fusion endpoint and secondary patient-reported measures. In general, when several outcomes are examined, multiplicity can arise from testing or estimating multiple outcomes, time points, subgroups, or comparisons. The statistical consequences depend on which analyses were planned and how claims are made. The record lists zero analyses and does not report a multiplicity strategy, hierarchy among secondary outcomes, or inferential results. Therefore, no adjustment method or testing plan can be attributed to the study from this entry.

The sample-size assumptions described for planning illustrations are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. These are planning assumptions, not a report of the trial's own design justification. The study itself is single group, so a two-arm illustration does not describe its allocation. The protocol's sample-size justification is not reported in the registry record. Any such illustration is not observed power; it is a planning calculation conditional on its assumptions. The observed effect used for that illustration is not reported in the registry entry described.

Over-dispersion is a general concern when count data vary more than a simple statistical model expects; accounting for it can affect standard errors and intervals. It is not identified as a method used in this study, and no count-model analysis is reported. Likewise, interim analyses, covariate adjustment, and methods for repeated measurements are not reported in the registry record. Statistical methods should not be inferred solely from the study's prospective or multi-center description.

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("chronOS Strip")
n      <- c(49)
events <- c(45)
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  chronOS Strip  49  45  91.8  80.4  97.7  80.8  96.8  80.8  96.7

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 11 outcome measures, including the composite primary endpoint and secondary measures of disability, back pain, leg pain, and physical health status. It also lists percent-change outcomes for several of these measures. The record does not describe a hierarchy among outcomes, a multiplicity adjustment, or which outcomes were treated as confirmatory. It reports zero analyses. Accordingly, no testing strategy or multiplicity correction can be attributed to the registry entry.

In general, multiplicity arises when multiple outcomes or analyses are considered, because the chance of at least one apparently notable finding can increase as the number of opportunities for a finding grows. How to address this depends on the planned questions and inferential goals. Listing several outcomes does not establish that each was tested, nor does it reveal whether a formal adjustment was planned. Numerical results and analysis details for the listed secondary outcomes are not reported in the registry record.

The primary endpoint was intended for the per-protocol population. The record states that 55 patients were evaluated at Month 24 and that six lacked complete radiographic data needed for primary endpoint assessment. It does not report the final analysis denominator, the disposition of those missing assessments, or whether any other participants were excluded from the per-protocol analysis. The reasons for missing radiographic data and any methods used to address missingness are not reported.

In general, missing data can affect both the size and interpretation of an analyzed population. A per-protocol estimate may not describe all enrolled participants if eligibility for analysis depends on post-enrollment criteria or availability of assessments. Without a stated handling rule and supporting sensitivity analyses, the extent to which missing endpoint observations affect the result cannot be evaluated. The record also does not provide a complete participant flow from enrollment to the primary analysis.

Interim analyses, stopping rules, and additional analysis populations are not reported in the registry record. Their absence from the record should not be taken to mean that a specific approach was or was not used; it means the entry does not document those details.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cardiovascular (7.4%), surgery, other (6.2%), surgery, index level (3.7%), dural tear (2.5%), pain: back (2.5%).

The registry lists 24 participants with serious adverse events among 81 at risk, and 34 participants with other adverse events among 81 at risk, in the chronOS Strip group. These are participant counts, not counts of individual event episodes. A participant may experience more than one event, and the registry figures alone do not describe event frequency over time, severity beyond the serious-event classification, or duration.

The serious adverse event terms with the highest listed percentages are Cardiovascular at 7.4%, Surgery, other at 6.2%, Surgery, index level at 3.7%, Dural tear at 2.5%, Pain: back at 2.5%, and Pain: back and legs at 2.5%. These percentages are reproduced as recorded; the registry entry does not provide additional context about timing, recurrence, or how each term relates to individual participants.

The number of deaths is not reported in the registry record. This should not be interpreted as a count of zero. The safety information presented is descriptive and comes from a single-group study. There is no concurrent comparator, so these figures cannot establish whether event occurrence differs from another treatment or whether events were caused by the device or the surgical procedure. The safety observation period and detailed event attribution are not reported in the registry record.

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

The study addresses an important descriptive question: how posterolateral fusion status was defined and assessed after surgery involving the chronOS Strip, bone marrow aspirate, and local bone. Its prospective, multi-center, single-group design can organize follow-up observations in a defined cohort. The primary endpoint has a clear composite structure requiring success on all four components at every investigated level.

However, the primary endpoint result is not reported in the registry record. Without an observed count or rate, the record does not establish how many participants met the composite definition, and it does not allow the precision of that estimate to be assessed. The Month 24 evaluation count and the count with incomplete radiographic data do not substitute for the outcome result.

Even if an outcome estimate were available, a single-group case series would describe the observed cohort rather than provide a randomized comparison. It could not by itself show what would have happened to comparable participants under a different device or treatment. The study design also cannot separate the contribution of the device from the accompanying surgical procedure and other features of care.

The listed secondary outcomes indicate that disability, pain, and physical health status were of interest, but their numerical results are not reported in the registry record. The adverse-event counts provide descriptive safety information, but lack a comparator and do not establish causation. Thus, neither the outcome list nor the safety counts alone support a causal claim about benefit or harm.

The registry entry is most informative about study structure, the endpoint definition, the reported follow-up assessment, and selected adverse-event summaries. It is not sufficient to determine the observed fusion success rate, assess statistical precision, evaluate changes in patient-reported outcomes, or make comparative conclusions.

14. Why This Trial Matters Statistically

This study illustrates why endpoint definitions matter. Posterolateral fusion success is not based on a single finding: the composite requires success across four components and all investigated levels. That rule makes the endpoint's meaning explicit, while also making component-level reporting important for understanding what determines an overall classification.

It also illustrates the difference between enrollment and an evaluable endpoint population. Enrollment is listed as 104, while 55 patients were evaluated at Month 24; six of those lacked complete radiographic data for primary endpoint evaluation. Without a complete participant flow and a reported final analysis denominator, readers cannot reconstruct the population underlying the primary estimate. The result itself is not reported in the registry record.

The design is another central statistical feature. A prospective, multi-center study can describe outcomes collected across participating settings, but a single-group case series does not create a randomized comparison. Statistical descriptions of outcomes and causal comparisons answer different questions. Recognizing this distinction helps prevent a cohort outcome from being interpreted as a treatment effect.

Finally, the entry records multiple secondary outcomes and selected safety counts without reporting detailed analyses or outcome estimates. This makes clear that listing an outcome is not the same as reporting its result, and that an adverse-event count is not a comparative safety analysis. For readers evaluating clinical evidence, the design, analysis population, missing assessments, and level of result reporting are as important as the endpoint label.

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 primary limitation of the registry information is that it does not report the primary endpoint result. No number of participants meeting the composite definition, endpoint rate, or uncertainty interval is given. The registry does not report numerical results for the listed secondary outcomes either.

The primary endpoint was evaluated in the per-protocol population, but the criteria defining that population and the final analysis denominator are not reported. Although 55 patients were evaluated at Month 24 and six lacked complete radiographic data for endpoint evaluation, the handling of those missing assessments is not stated. The record does not describe reasons for missingness, sensitivity analyses, or a complete participant flow.

The study has a single group and no randomized comparator. Its observed outcomes therefore cannot, on their own, quantify a difference versus another treatment or separate the device's contribution from the rest of the surgical procedure. The absence of masking is recorded, but the registry does not describe endpoint assessment procedures in enough detail to evaluate the potential influence of knowledge of treatment on assessment.

Although 11 outcome measures are listed, the record does not report which analyses were conducted, how multiple outcomes were handled, or the statistical methods for the primary endpoint. It does not state the protocol's sample-size justification, interim analyses, or detailed analysis plan. The safety entries likewise do not specify the observation period, event timing, or attribution, and the number of deaths is not reported.

These limitations concern what the registry record documents; they do not establish that an unreported procedure or analysis was absent from the full study materials. They do restrict the conclusions that can be drawn from this record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Prospective, Multi-Center Clinical Outcomes Study Evaluating the chronOS Strip Combined With Bone Marrow Aspirate — NCT00943384.
• Registry record last updated 2014-11-26; status last verified 2014-11.
• Results first posted 2014-11-26.
• 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

The registry record describes NCT00943384, a completed prospective, multi-center, single-group clinical outcomes study sponsored by Synthes USA HQ, Inc. It enrolled 104 participants with degeneration of the lumbar intervertebral disc. The listed intervention was the chronOS Strip, used with bone marrow aspirate and local bone during instrumented fusion with interbody support.

The primary endpoint was posterolateral fusion success at Month 24, defined by a composite requiring success across all four components at all investigated levels. The endpoint was evaluated in the per-protocol population. The record states that 55 patients were evaluated at Month 24 and six lacked complete radiographic data for endpoint assessment, but the primary endpoint result and final analysis denominator are not reported.

Secondary outcomes included disability, pain, and physical health status measures. Their numerical results are not reported in the registry record. Safety entries list 24 participants with serious adverse events and 34 with other adverse events, each among 81 at risk. The record does not provide a randomized comparator, detailed analysis methods, or a reported number of deaths.