KAVIAR Study - Kyphoplasty And Vertebroplasty In the Augmentation and Restoration of Vertebral Body Compression Fractures: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for KAVIAR Study - Kyphoplasty And Vertebroplasty In the Augmentation and Restoration of Vertebral Body Compression Fractures (NCT00323609), a randomized na study. The primary outcome is Percent of Subjects With One or More Subsequent Radiographic Fractures at 12 Months.

2. Clinical Question

The KAVIAR study asked whether balloon kyphoplasty and vertebroplasty differed in their short- and long-term safety and effectiveness for painful, acute osteoporosis-related vertebral body compression fractures. The main outcome was the percentage of participants with one or more subsequent radiographic fractures at 12 months.

The registry describes a broader comparison over 2 years of follow-up. Planned outcomes included back pain, back function, quality of life, adverse events, subsequent fractures and cumulative healthcare costs. The listed secondary outcomes also include serious adverse events at 30 days and changes in anterior and middle vertebral body height.

The available record does not give the arm-specific primary endpoint percentages or a direct estimate of the difference between procedures. It therefore does not establish from the posted primary outcome whether the groups differed, or how precisely any difference was estimated.

3. Trial Design

KAVIAR was a multicenter, randomized, prospective, parallel-group clinical trial comparing balloon kyphoplasty with vertebroplasty. The registry lists allocation as randomized and masking as none; the trial was therefore not masked according to the record. The record lists phase as not applicable.

Enrollment is listed as 404. The study start is recorded as 2006-08, and primary completion as 2011-07. The current registry status is terminated. The registry record does not report the reason for termination, so the status alone does not establish why the trial ended or whether the planned follow-up was completed.

Participants were assigned to one of the two procedures. The brief summary describes planned follow-up over 2 years, with assessments covering pain, function, quality of life, adverse events, subsequent fractures and cumulative healthcare costs. The primary endpoint concerns subsequent radiographic fractures at 12 months. Several listed safety outcomes concern events at 30 days.

The registry lists 15 outcome measures and 45 analyses. That breadth indicates that the study record includes more than the single primary endpoint, but the number of listed outcomes does not itself explain which comparisons were prespecified as primary, how outcomes were prioritized, or how statistical multiplicity was handled. Those details are not reported in the registry record.

The primary endpoint population is described as an intent-to-treat population comprising randomized participants who had initial treatment carried out. The record also says that the number with available 12-month data is indicated for each group, but arm-specific primary-outcome denominators and endpoint results are not reported in the registry record.

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: Intent to treat population comprised of all subjects randomized and had initial treatment carried out. The n for each group with available data at 12-months is indicated.

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.

6. Primary Endpoint

The registry lists the primary outcome as Percent of Subjects With One or More Subsequent Radiographic Fractures at 12 Months, measured over 12 months.

The primary endpoint is the percentage of participants with one or more subsequent radiographic fractures at 12 months. It is a binary participant-level outcome: a participant either met the stated criterion during the endpoint assessment or did not. The measure concerns radiographic fractures, rather than pain, function, quality of life or a measure of fracture severity.

Counting participants with at least one event is a way to describe how commonly the defined outcome occurred in each group. It gives a clinically interpretable summary of participants experiencing a subsequent radiographic fracture, but it does not describe the total number of fractures per participant or the timing of each fracture. Those are different questions and would require different outcome definitions.

The record defines the analysis population as randomized participants who had initial treatment carried out and notes that the group-specific number with available data at 12 months is indicated. The actual arm-specific counts with endpoint data and the percentages meeting the endpoint are not reported in the registry record available for this analysis. As a result, the endpoint's definition is clear, but its observed comparative result cannot be interpreted from the record.

Radiographic follow-up makes the endpoint dependent on whether imaging and outcome ascertainment were available. The record does not describe the imaging schedule, assessment procedures, or how missing endpoint data were handled. Those omissions matter when judging how completely the endpoint was measured and how representative the observed data might be.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical methods that were actually used for the primary comparison are not reported in the registry record. The explanations below describe general statistical concepts relevant to interpreting the stated binary endpoint and the posted safety counts; they do not claim that any particular method was used in KAVIAR.

What does a percentage measure?

For a binary endpoint, a percentage describes the share of participants meeting a defined criterion among those assessed. Here, the criterion is having one or more subsequent radiographic fractures by the 12-month assessment. The denominator matters: a percentage based on participants with observed endpoint data may differ from one based on everyone randomized if some endpoint data are missing. The record describes an intent-to-treat population that includes randomized participants with initial treatment carried out, and it notes available data by group. It does not report the actual group-specific endpoint denominators or percentages in the registry record available for this analysis.

A group percentage is descriptive. A treatment comparison requires a contrast between groups, along with an assessment of uncertainty. Different contrast measures can express that comparison, and the registry record does not state which one was used for the primary analysis. No specific comparison measure should therefore be attributed to the trial from this information.

Why does a confidence interval matter?

General statistical explanation: a confidence interval expresses the range of values for a population effect that are reasonably compatible with the observed data under a stated statistical model. Its width conveys precision: a wider interval indicates greater uncertainty, while a narrower interval indicates greater precision. The interval also helps readers assess whether the data are compatible with effects of different magnitudes, rather than reducing interpretation to a single threshold judgment.

No confidence interval for the primary comparison is reported in the registry record. Without the estimate and interval, readers cannot evaluate either the magnitude or precision of the between-group result. The absence of an interval should not be interpreted as evidence that uncertainty is small.

What role does a p-value play?

General statistical explanation: a p-value measures how unusual data at least as inconsistent with a specified null hypothesis would be, under the assumptions of the statistical test. It does not give the probability that the null hypothesis is true, and it does not describe the size or clinical importance of an effect. A p-value is most informative alongside an effect estimate, its confidence interval, the endpoint definition and the analysis population.

A primary-outcome p-value is not reported in the registry record available for this analysis. Even if a p-value were available, it would not replace the missing group percentages and effect estimate. The record also does not report the testing procedure or whether the analysis was adjusted for other variables.

Why can event counts and participant counts differ?

General statistical explanation: a participant-level outcome that records whether someone had one or more events counts each participant according to whether the criterion was met. It does not count repeated events separately. An event-level analysis may instead count every event, and a time-to-event analysis may use the time until an event. These approaches answer different questions and can produce different summaries.

The primary endpoint is expressly participant-based: the percentage with one or more subsequent radiographic fractures. The record does not provide a count of all fractures or the timing of subsequent fractures. The serious adverse event information is also presented in terms of participants affected and participants at risk, rather than a full account of event episodes.

What do the planning illustrations represent?

General statistical explanation: a sample-size calculation is a planning exercise that estimates how many participants or events may be needed under chosen assumptions. It is not a description of the observed results, and it does not show the power achieved after a trial has finished. The registry's planning assumptions are described as a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. For time-to-event tables, the stated planning quantity is total events using the Schoenfeld approach; other planning quantities are participants per arm.

These are planning illustrations based on an observed effect, not the trial's own design justification. The registry record does not report the original sample-size justification or enough detail to establish the assumptions used in the trial's design. No planning illustration should be read as observed power or as evidence that a target sample size was reached for the primary endpoint.

How should multiple outcomes be considered?

General statistical explanation: when many outcomes or comparisons are tested, the chance of finding at least one apparently notable result by chance can increase. Statistical plans may address this through a hierarchy of outcomes, adjusted thresholds, or other strategies. Whether and how to account for multiplicity depends on the analysis plan and the claims being made. The registry lists 15 outcome measures and 45 analyses, but the approach to multiplicity is not reported in the registry record. These counts alone do not show which analyses were confirmatory or whether any adjustment was applied.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 15 outcome measures and 45 analyses. That range of recorded outcomes and analyses raises questions about which comparisons were intended to provide confirmatory evidence and how the primary endpoint was distinguished from secondary or exploratory analyses. The registry record does not report a multiplicity strategy, a testing hierarchy, or adjusted significance thresholds. General statistical context: when researchers test many hypotheses, some results can appear notable by chance, so interpretation should account for the number and priority of analyses. The available record does not allow readers to determine how this issue was handled.

The primary endpoint description defines an intent-to-treat population as randomized participants who had initial treatment carried out, and says the number with available 12-month data is indicated for each group. However, the arm-specific available-data counts and observed primary endpoint results are not reported in the registry record. Nor does the record describe how participants with missing radiographic follow-up were handled, whether any imputation was used, or whether sensitivity analyses were performed.

Missing endpoint data can affect a percentage if the participants with observed assessments differ from those without them. General statistical context: complete-case results may be biased when the likelihood of missing data is related to participant characteristics or outcomes. The record does not provide enough information to assess that possibility or the robustness of the result to missingness.

The registry does not report the analysis model, covariate adjustment, or a statistical analysis plan. It is therefore not possible to determine from the record whether the primary comparison followed a prespecified plan or how deviations, if any, were addressed. The absence of these details is uncertainty about the reporting record, not proof that no such procedures existed.

11. 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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: back pain (22.1%), fall (16.8%), thoracic vertebral fracture (10.0%), urinary tract infection (9.5%), arthralgia (7.9%).

For serious adverse events, the registry lists 125 affected participants among 191 at risk in the kyphoplasty group and 125 affected participants among 190 at risk in the vertebroplasty group. These figures are counts of participants recorded as affected and the corresponding at-risk groups, not counts of all individual event episodes. A participant may experience more than one event; these counts alone do not describe event frequency per participant.

The registry also lists 55 participants with other adverse events among 191 at risk in the kyphoplasty group, and 69 among 190 at risk in the vertebroplasty group. The record does not fully define the relationship between this category and serious adverse events, so the categories should not be assumed to be mutually exclusive or directly comparable without further detail. Death counts are not reported in the registry record.

Listed serious-event terms and associated percentages include back pain, 22.1%; fall, 16.8%; thoracic vertebral fracture, 10.0%; urinary tract infection, 9.5%; arthralgia, 7.9%; and pneumonia, 7.3%. Their denominators and treatment-group allocation are not reported in the registry record. These terms and percentages are descriptive entries; they do not establish that an event was caused by a procedure. Interpretation also depends on definitions, follow-up, severity and comparative analyses, details that are not fully.

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

The registry record establishes that KAVIAR was designed as a randomized comparison of balloon kyphoplasty and vertebroplasty for painful, acute osteoporosis-related vertebral body compression fractures. It identifies subsequent radiographic fracture at 12 months as the primary endpoint and describes a broader set of planned outcomes over 2 years of follow-up. It also reports serious and other adverse-event counts for the two groups.

Those details do not provide the primary arm-specific fracture percentages or a comparative estimate. The posted primary outcome information therefore does not show whether one group had a higher or lower percentage with subsequent radiographic fractures, or how precisely a difference was estimated. It cannot support a conclusion of equivalence, benefit or lack of benefit.

The serious adverse event counts are descriptive safety data. They do not, on their own, establish that a treatment caused or prevented an event, nor do they replace a prespecified comparative safety analysis. The listed event-term percentages have no reported denominator or group allocation in the record available for this analysis. Caution is also appropriate because the record does not describe event definitions, adjudication procedures or the handling of incomplete follow-up.

The registry status is terminated, while the reason for termination is not reported in the registry record. Termination should not be interpreted as proof of an unfavorable result, a safety concern or failure to complete planned follow-up. The registry record also does not supply the statistical analysis plan, multiplicity approach, missing-data methods or primary inferential results needed to evaluate those possibilities.

In short, the record supports an account of the trial's question, design, endpoint definition and posted safety counts. It does not provide enough primary-outcome information to resolve the central comparative question or to assess the precision and robustness of a treatment effect.

13. Why This Trial Matters Statistically

KAVIAR is statistically important because it addresses a randomized comparison between two procedures using a patient-level outcome that is straightforward to define: whether a participant had one or more subsequent radiographic fractures at 12 months. Randomization is intended to support a fair comparison by reducing systematic differences between groups at the point of assignment. The record identifies the randomized parallel-group design, but does not provide the primary comparative estimate needed to judge the result.

The trial also illustrates why an endpoint definition is not enough to interpret an outcome. The group denominators, observed percentages, effect estimate and uncertainty are all essential for understanding a binary endpoint. The record describes the target population and available-data approach, yet the actual arm-specific primary results are not reported in the registry record. Without them, the statistical question remains unresolved even though the trial's main endpoint is clearly named.

The breadth of listed outcomes is another statistical consideration. Pain, function, quality of life, safety, vertebral height, fractures and costs concern different aspects of treatment and may be analyzed in different ways. Listing 15 outcome measures and 45 analyses does not explain which findings were most important or how multiplicity was managed. Transparent prioritization and reporting help readers distinguish a primary confirmatory comparison from additional analyses.

Finally, the record shows why safety counts need context. At-risk denominators and affected-participant counts are useful descriptive information, but a full interpretation also depends on definitions, follow-up, group comparisons and uncertainty. KAVIAR's registry record preserves important design and safety details while leaving key elements of primary statistical interpretation unreported.

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 main limitation for interpreting the primary outcome is that arm-specific percentages and a direct comparison for subsequent radiographic fractures at 12 months are not reported in the registry record available for this analysis. No confidence interval or p-value for that comparison is reported either. Consequently, the direction, magnitude and precision of the primary result cannot be assessed.

The record describes the primary population as randomized participants who had initial treatment carried out, with the available-data count intended to be shown for each group. The actual arm-specific endpoint denominators are not reported. The registry also does not describe how missing radiographic assessments were handled, whether any sensitivity analyses were conducted, or how endpoint assessment was standardized.

The trial is listed as terminated, but the reason is not reported in the registry record. The status alone does not establish whether planned follow-up was completed or whether termination affected the data available for analysis. The record does not report the original sample-size justification, the analysis model, the handling of multiplicity, or the statistical analysis plan.

For safety, the registry lists counts of affected participants and at-risk participants, but the available information does not fully define the adverse-event categories or clarify the denominators for the serious-event term percentages. Death counts are not reported in the registry record. These gaps limit a complete comparison of safety patterns, and the counts should not be treated as causal estimates.

These reporting limitations do not prove that the trial lacked detailed methods or additional analyses. They mean that those details and results cannot be evaluated from the registry record available for this analysis.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: KAVIAR Study - Kyphoplasty And Vertebroplasty In the Augmentation and Restoration of Vertebral Body Compression Fractures — NCT00323609.
• Registry record last updated 2018-01-02; status last verified 2012-06.
• Results first posted 2012-08-08.
• 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

KAVIAR (NCT00323609) was a multicenter, randomized, prospective, parallel-group trial comparing balloon kyphoplasty with vertebroplasty for painful, acute osteoporosis-related vertebral body compression fractures. The record lists enrollment of 404, masking as none, study start as 2006-08, primary completion as 2011-07, and status as terminated. The reason for termination is not reported in the registry record.

The primary endpoint was the percentage of participants with one or more subsequent radiographic fractures at 12 months. The record describes an intent-to-treat population of randomized participants who had initial treatment carried out. Arm-specific primary endpoint results and a comparative estimate are not reported in the registry record available for this analysis.

The registry lists 15 outcome measures and 45 analyses, planned follow-up over 2 years, and serious and other adverse-event counts for both groups. The analysis plan, missing-data methods and approach to multiplicity are not reported in the registry record.