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 Study Performance of The Plexur P™ Bone Void Filler Device in Patients Undergoing Iliac Crest Harvesting Procedures (NCT00837473), a na na study. The primary outcome is Number of Participants With Reconstitution of Bone Growth in the Iliac Crest Bone Void Determined by an Independent Radiologist.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00837473 |
| Phase | NA |
| Condition | Iliac Crest Harvesting Procedure-Bone Void Filler |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 15 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Osteotech, Inc |
| Results posted | Yes |
2. Clinical Question
Population
Patients requiring back surgery who have bone removed from the iliac crest for the procedure. The registry record describes a study enrollment of 15 and says the primary analysis dataset included study subjects with available data.
Intervention
Plexur-P Bone Void Filler placed in the iliac crest void created by bone harvesting. The intervention is identified as a device, and the single arm is described as open label.
Comparator
There is no comparator arm in this single-group study. Allocation is recorded as NA, so the study does not provide a randomized comparison or a like-for-like control comparison.
Primary question
At 6 wks, 3 mths, 6 mths 12 mths, and 24 mths, how many participants had reconstitution of bone growth in the iliac crest bone void, as determined by an independent radiologist using the stated radiographic criteria?
The clinical question concerns radiographic bone growth at a surgically created bone void. The endpoint is assessed repeatedly over follow-up, with the radiologist evaluating bony ingrowth and whether a gap remains. The registry record does not report how many participants met the endpoint at any assessment time. It also does not state which of the radiographic grades counted as reconstitution for the participant count. Those omissions prevent a numerical answer to the primary question from the record alone.
3. Trial Design
The registry identifies this as a prospective pilot study of Plexur P, a bone void filler device used in iliac crest harvesting procedures. Its stated purpose is to examine bone growth in the area where bone was removed for back surgery. The record lists one intervention arm, Plexur-P Bone Void Filler, and describes that arm as single group and open label. Masking is recorded as none. Allocation is recorded as NA, and there is no comparator arm in the design described.
The study enrollment is 15. The primary outcome concerns the number of participants with reconstitution of bone growth in the iliac crest bone void. An independent radiologist determined reconstitution using criteria based on bony ingrowth, mineralization, coalescence, and the presence or absence of a gap. Assessments are listed at 6 wks, 3 mths, 6 mths 12 mths, and 24 mths. The registry record says the primary analysis dataset included all study subjects with available data; it does not specify the number contributing data at each time point.
The record lists secondary outcomes covering general health status, disability, pain, harvest location and amount, operative time, blood loss, and hospital stay. It records 10 outcome measures and 0 analyses. The study status is completed, with a start of 2009-01 and primary completion of 2011-03. The record does not report a control group, a randomization procedure, or a statistical analysis plan. The available design information therefore supports describing a single-group pilot evaluation, not an estimate of comparative treatment effect.
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 | Plexur-P Bone Void Filler |
|---|---|
| STARTED | 15 |
| COMPLETED | 12 |
| NOT COMPLETED | 3 |
Reasons for not completing this period:
| Reason | Plexur-P Bone Void Filler |
|---|---|
| Lost to Follow-up | 1 |
| Withdrawal by Subject | 2 |
Analysis population for the primary outcome, as defined in the registry: The primary analysis dataset included all study subjects with available data.
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 | Plexur-P Bone Void Filler |
|---|---|---|
| Participants analysed | 15 | |
| Age, Continuous | years | 56.13 (SD 9.45) |
| Sex: Female, Male: Female | Participants | 13 |
| Sex: Female, Male: Male | Participants | 2 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Reconstitution of Bone Growth in the Iliac Crest Bone Void Determined by an Independent Radiologist, measured over 6 wks, 3 mths, 6 mths 12 mths, and 24 mths.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the number of participants with reconstitution of bone growth in the iliac crest bone void, determined by an independent radiologist. The assessment is scheduled at 6 wks, 3 mths, 6 mths 12 mths, and 24 mths. The radiographic criteria describe four grades: absent, mild, moderate, and extensive. They distinguish limited or absent mineralization from visible mineralization and coalescence of the graft mass, with more extensive grades requiring greater continuity and trabecular development. The criteria also refer to radiolucent areas and the presence or absence of a gap.
Such an endpoint is used to characterize radiographic healing at the site where bone was harvested and the void was filled. It focuses on the local imaging appearance rather than a direct measure of pain, function, or overall health. The independent radiologist provides an assessment separate from the treating team, but the registry record does not report whether the radiologist was masked to treatment or other participant information. Nor does it state which grades were classified as “reconstitution” for the participant count. The record does not report endpoint results at any assessment time, so the observed count and its precision cannot be described.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record describes the primary outcome and its assessment schedule but does not report the number of participants with reconstitution of bone growth at any of the listed times. It therefore does not support a numerical summary of the primary outcome, a comparison across visits, or a conclusion about how consistently the endpoint was observed. No confidence interval, hypothesis test, or other primary-outcome estimate is reported in the registry record.
The endpoint is a count of participants meeting a radiographic definition. To interpret such a count, readers need both the number meeting the definition and the number assessed at the relevant time. The record says that the primary analysis dataset included all study subjects with available data, but it does not report the available-data denominator at each visit. It also does not specify how the four radiographic grades were collapsed into the endpoint count. Without those details and the observed results, the degree of uncertainty around the endpoint cannot be evaluated from the registry entry.
The repeated assessments could describe how radiographic appearance changes over follow-up, but a sequence of visit-specific results is not present in the record. Repeated measurements on the same participants are related rather than independent observations; a formal analysis would need to account for that structure if it were estimating change over time. The registry record does not report such an analysis. The outcome schedule alone is not evidence that improvement occurred or that the measure changed in a particular direction.
The single-group design also limits what can be inferred. Without a comparator, observed imaging findings could not be separated from other explanations through a concurrent between-group comparison. The study is described as a prospective pilot, but the record does not report a prespecified statistical plan or a sample-size justification. The enrollment of 15 is a design fact, not evidence of adequate precision or statistical power.
Safety information is reported separately from the primary endpoint. The registry lists serious adverse events affecting 12 of 15 participants and other adverse events affecting 14 of 15 participants. These counts do not supply missing radiographic results and should not be treated as evidence about the primary endpoint. Overall, the posted record permits a description of the study design, outcome definition, and listed safety counts, but not a quantitative interpretation of the primary efficacy outcome.
9. Statistical Methods Explained
What does a participant count convey?
A count endpoint records how many people meet a stated condition. For interpretation, the count needs a clearly defined rule for classifying participants and a denominator showing how many were assessed. A count by itself does not indicate how common the outcome was in the study group, and a count without a corresponding denominator cannot describe the observed proportion. In this trial, the primary endpoint is a count of participants with radiographic reconstitution. The registry record identifies the available-data population but does not report visit-specific counts or denominators.
General statistical principle: an estimate based on a limited group of observations is subject to sampling uncertainty. A confidence interval expresses a range of values compatible with the data under the assumptions of the method used. Its width depends on the amount and pattern of information and on the method. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed from that entry.
How should the radiographic grades be understood?
The outcome description lays out ordered categories from absent through extensive. The categories reflect differing amounts and patterns of mineralization, coalescence, remodeling, and trabeculation. Because these are ordered descriptions rather than a simple continuous measurement, treating the grades as if the distance between each adjacent grade were equal would require justification. The primary outcome title refers to the number with reconstitution, but the registry record does not specify which grades met that binary definition. The grading criteria alone should not be used to infer the classification rule.
The independent radiologist is identified as the assessor. The record does not report a masking procedure for that assessment. In general, masking can reduce the opportunity for knowledge of other information to influence an assessment, while an independent assessor provides a separate evaluation. Neither feature, by itself, establishes that measurements are free of bias; the assessment procedures and their implementation matter.
What do repeated follow-up assessments add?
The endpoint is scheduled at 6 wks, 3 mths, 6 mths 12 mths, and 24 mths. Repeated assessments can describe the timing and course of radiographic findings, but each visit may have a different number of available observations. Participants’ measurements across visits are usually related because the same people may be assessed repeatedly. General statistical principle: analyses of repeated observations should account for that within-person relationship rather than treating each visit as unrelated data. The registry record does not report a longitudinal analysis, an approach to missing visits, or results at the scheduled assessments.
Assessments at multiple visits also create interpretive choices: whether each visit is a separate endpoint, whether a particular visit is primary, and how results across visits are interpreted together. The record names the assessment times but does not report a hierarchy among them or a method for handling multiple tests. As a result, no claim about a prespecified primary time point or multiplicity adjustment can be made.
What can be inferred from the design?
This is a single-group, open-label study with no comparator arm. A single-group outcome can describe what was observed among participants with available data, if results are reported. It cannot, on its own, estimate a between-group difference. General statistical principle: causal comparisons require a basis for distinguishing the effect associated with an intervention from other factors that could influence outcomes. A concurrent control can help with that distinction; this study’s design does not include one.
The registry record lists an enrollment of 15 and identifies a pilot study, but does not report the rationale for that enrollment, the intended precision, or a formal power calculation for the trial design. The record’s planning illustrations are described as calculations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They are planning illustrations, not the study’s design rationale or observed power. The stated convention is that time-to-event illustrations give total events and other illustrations give participants per arm. Those assumptions should not be mistaken for an analysis plan for this single-group study.
The registry records 0 analyses. That entry does not provide estimates or tests to interpret, and the record does not describe the sponsor’s statistical methods. No unadjusted recalculation is reported in the registry record. Without outcome values, analysis methods, denominators, and uncertainty estimates, the statistical interpretation must remain limited to the design and endpoint description.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 10 outcome measures and 0 analyses. The secondary outcomes named in the record cover general health status, the Oswestry Disability Index, pain assessed by VAS, harvest location, amount of cancellous bone harvested, operative time, blood loss, and length of hospital stay. The primary endpoint has assessments at 6 wks, 3 mths, 6 mths 12 mths, and 24 mths. Considering several outcomes and visits can raise multiplicity concerns: when many statistical tests are conducted, the chance of at least one apparently notable result may increase. The registry record does not report a testing hierarchy, multiplicity adjustment, or analysis plan, so it is not possible to determine how this issue was handled.
For the primary endpoint, the record says that the analysis dataset included all study subjects with available data. It does not report how many participants had data at each assessment, the amount or reasons for missing data, or whether missing observations were imputed. It also does not describe assumptions or sensitivity analyses for missingness. The enrollment of 15 should not be treated as the denominator at every follow-up visit.
The analysis population is described only as study subjects with available data. The record does not report additional population definitions, exclusions, or a participant flow through the analyses. It also does not report whether all enrolled participants were included in each secondary outcome analysis. These omissions prevent assessment of how missingness or analysis-population choices could affect the posted results.
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 |
|---|---|---|---|
| Plexur-P Bone Void Filler | 12 | 15 | 80.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0.0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Plexur-P Bone Void Filler | 14 of 15 |
Most frequent serious adverse event terms
| Event term | Organ system | Plexur-P Bone Void Filler |
|---|---|---|
| Other | Injury, poisoning and procedural complications | 5 of 15 |
| Other | Product Issues | 3 of 15 |
| Other | Respiratory, thoracic and mediastinal disorders | 3 of 15 |
| Other | Endocrine disorders | 1 of 15 |
| Other | General disorders | 1 of 15 |
| Infection other | Infections and infestations | 1 of 15 |
| Other | Infections and infestations | 1 of 15 |
| Other | Metabolism and nutrition disorders | 1 of 15 |
| Other | Musculoskeletal and connective tissue disorders | 1 of 15 |
| Other | Nervous system disorders | 1 of 15 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Plexur-P Bone Void Filler |
|---|---|---|
| Other | Respiratory, thoracic and mediastinal disorders | 9 of 15 |
| Ileus | Gastrointestinal disorders | 3 of 15 |
| Other | Investigations | 3 of 15 |
| Edema | General disorders | 2 of 15 |
| Infection, other | Infections and infestations | 2 of 15 |
| Other | Infections and infestations | 2 of 15 |
| Other | Nervous system disorders | 2 of 15 |
| Other | Cardiac disorders | 1 of 15 |
| Other | General disorders | 1 of 15 |
| Infection, operative site | Infections and infestations | 1 of 15 |
Serious events with the highest arm-level rate: other (33.3%), infection other (6.7%).
The registry lists serious adverse events affecting 12 of 15 participants in the Plexur-P Bone Void Filler group. It separately lists other adverse events affecting 14 of 15 participants. These are participant counts, not a statement of the total number of individual event episodes. The serious-event terms listed most prominently are “Other” at 33.3% and “Infection other” at 6.7%. The record does not explain the category “Other” further in the information.
These figures describe the safety entries in the registry record; they do not establish whether an event was caused by the device or by another aspect of care. The record does not report event-level details such as timing, duration, severity beyond the serious-event classification, or causal attribution. A death count is not reported in the registry record. Because this is a single-group study, the listed counts do not provide a controlled comparison of adverse-event experience. They should be read as descriptive safety information for the study group, not as a comparative estimate.
12. What the Result Does, and Does Not, Mean
The study addresses a defined local question: whether radiographic assessment identified reconstitution of bone growth in an iliac crest void after Plexur P was used as a bone void filler. The registry record identifies the endpoint, the independent radiologist assessment, the grading criteria, and the scheduled follow-up times. It also describes a prospective, open-label, single-group pilot study with an enrollment of 15.
What the record does not provide is the primary endpoint result. There is no reported count of participants meeting the reconstitution definition at any assessment time, no visit-specific denominator, and no estimate of uncertainty. The threshold for converting the absent, mild, moderate, and extensive grades into the participant-level endpoint is also not stated. Accordingly, the record cannot establish the observed frequency or course of radiographic reconstitution.
Even if outcome counts were available, a single-group study would remain descriptive rather than a controlled estimate of comparative effect. Without a comparator, the study cannot distinguish the outcome associated with the device from outcomes that might occur for other reasons. The open-label design and unreported masking details for the radiologist are additional considerations when interpreting an imaging assessment.
The safety counts provide a separate description of reported adverse events among participants in the study group. They do not answer the primary radiographic question, establish causation, or supply a comparison with another treatment. The appropriate interpretation is therefore limited: the registry record documents the question, design, outcome definitions, and safety counts, but it does not report the primary results needed to quantify the radiographic outcome.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of the difference between an outcome definition and an outcome result. The registry describes a participant-count endpoint, a radiographic grading system, an independent assessor, and multiple follow-up assessments. Those details clarify what investigators intended to measure. They do not indicate how many participants met the endpoint or how uncertain that finding would be.
The study also illustrates the limits of inference from a single-group pilot design. A count observed after device use can describe the enrolled group, but the absence of a comparator prevents a direct estimate of how outcomes differ from another approach. The enrollment of 15 gives context for the scale of the study, but does not by itself demonstrate that estimates would be precise or that the study was sized for a specific statistical objective. The registry record does not report a trial-specific sample-size justification.
Repeated imaging assessments make clear why time-specific denominators, missing-data information, and a prespecified interpretation of the ordered grades matter. Without those details and endpoint results, readers cannot assess change over follow-up or distinguish a robust pattern from one that is uncertain. The record’s limited analysis information also means that multiplicity and analysis choices cannot be evaluated.
These features do not make the study uninformative: its design and measurement description identify the intended clinical and statistical question. They do, however, define the boundary of what can be concluded from the registry record. The posted information supports a careful account of what was planned and how safety counts were recorded, not a quantitative claim about the primary endpoint.
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 registry record does not report the primary endpoint results. It provides neither participant counts meeting the endpoint nor denominators at each follow-up assessment. The record also does not state which radiographic grades counted as reconstitution, leaving the operational rule for the participant count unclear.
The study has one open-label group and no comparator. Consequently, it cannot provide a controlled comparison, and the record does not describe a randomized allocation. Masking is recorded as none; whether the independent radiologist was masked to other information is not reported in the registry record. The radiographic endpoint is local and does not by itself capture pain, function, or general health, although those are listed among secondary outcome areas.
The record does not report visit-specific missingness, reasons for missing assessments, imputation, or sensitivity analyses. It does not report a statistical analysis plan, a multiplicity strategy, or a sample-size justification for the trial. Although the status is completed, completion status does not supply the missing outcome estimates or analysis details. Safety information is also limited to the participant counts and event terms listed; event-level descriptions and causal attribution are not reported in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study Performance of The Plexur P™ Bone Void Filler Device in Patients Undergoing Iliac Crest Harvesting Procedures — NCT00837473.
- Registry record last updated 2018-04-30; status last verified 2012-09.
- Results first posted 2018-04-30.
- 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
The registry record describes a completed prospective pilot study of Plexur P as a bone void filler in iliac crest harvesting procedures. It lists a single open-label group, no masking, allocation recorded as NA, and enrollment of 15. The primary outcome is the number of participants with reconstitution of bone growth in the iliac crest void, assessed by an independent radiologist at 6 wks, 3 mths, 6 mths 12 mths, and 24 mths. The primary analysis dataset is described as including study subjects with available data.
The record lists 10 outcome measures and 0 analyses. It reports serious adverse events affecting 12 of 15 participants and other adverse events affecting 14 of 15 participants. It does not report the primary endpoint counts, visit-specific denominators, or confidence intervals. The available information supports a description of the study design and measurement approach, but not a quantitative interpretation of the primary outcome.