Bone Marrow Aspirate Compared to Platelet Rich Plasma for Treating Knee Osteoarthritis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Bone Marrow Aspirate Compared to Platelet Rich Plasma for Treating Knee Osteoarthritis (NCT03289416), a randomized phase 4 study. The primary outcome is Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Measurements.

2. Clinical Question

The central statistical question is whether the recorded pain scores differed between the randomized groups over the planned follow-up. To answer it from results, readers would need the group estimates, their uncertainty, and the analysis used to account for repeated measurements. Those comparative results and analysis details are not reported in the registry record. The record lists the Subjective International Knee Documentation Committee Subjective Score (IKDC) as a secondary outcome, but does not provide its results.

3. Trial Design

The registry describes a randomized, parallel-group, open-label clinical trial, listed as phase 4. Participants were assigned to a Platelet Rich Plasma (PRP) arm or a Bone Marrow Concentrate (BMC) arm. The enrollment is recorded as 90. The sponsor is Andrews Research & Education Foundation, and the registry status is completed.

The recorded study start date is 2013-12-05, and the primary completion is recorded as 2020-02. The primary measure is WOMAC pain score, with assessments listed at baseline, 1 month, 3 months, 6 months, 9 months, and 12 months. The secondary outcome listed is the Subjective International Knee Documentation Committee Subjective Score (IKDC).

The record identifies the interventions as Pure PRP II and PureBMC. It describes blood collection and processing for PRP, and bone marrow collection from the posterior iliac crest and processing for BMC. The arm descriptions are truncated, so the full procedures cannot be reconstructed from the registry record.

Randomization supports a comparison between assigned groups, but the record does not report the randomization method, allocation concealment, or further details of trial conduct. Masking is listed as none. Whether participants, outcome assessors, or analysts were masked in any other way is not reported in the registry record. The analysis population, handling of adherence or treatment changes, and primary statistical model are also not reported. The record contains no reported outcome analyses, so the design information alone does not establish the direction, size, or precision of any treatment-group difference.

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

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 Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Measurements, measured over Baseline, 1 month, 3 months, 6 months, 9 months, and 12 months.

The primary outcome is described as WOMAC Measurements, reported as a mean score with a 95% confidence interval. The registry characterizes the measure as a pain score collected through patient surveys. The scale runs from 0 to 20, with 20 representing most pain and 0 representing least pain.

The listed assessment schedule runs from baseline through 12 months, with measurements at 1 month, 3 months, 6 months, and 9 months as well as the 12-month assessment. A repeated patient-reported measure can describe how scores change over follow-up and whether the groups' recorded patterns differ. This is a general statistical point, not a claim about the findings of this trial.

The WOMAC pain measure is relevant to the stated trial question because the study was intended to compare treatments for symptomatic knee osteoarthritis using patients' reports of pain. However, the registry record does not report the observed means, confidence intervals, or a specific between-group contrast at any assessment. It also does not report how baseline scores were incorporated into the analysis or which assessment was designated as the primary comparison. Consequently, the endpoint definition and schedule can be described, but the comparative result cannot be interpreted from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a confidence interval describe?

The primary outcome is specified as a mean with a 95% confidence interval. In general, a confidence interval conveys uncertainty around an estimated quantity under the assumptions of the statistical method. It is not a range containing every participant's score, and it does not by itself indicate whether a difference matters to patients. A reader would interpret the interval alongside the treatment contrast, the score scale, and the clinical context. The registry record does not report the WOMAC means or confidence intervals, so this trial's outcome precision cannot be assessed from the record.

Why does the follow-up schedule matter?

WOMAC was scheduled at baseline and several follow-up assessments through 12 months. General statistical methods for repeated measurements must account for the fact that scores from the same participant are related. Treating each assessment as if it came from a different set of people can misrepresent uncertainty. A model can also make different assumptions about change over time, correlations among measurements, and how to use incomplete follow-up. The registry record does not report which approach was used.

There are different reasonable ways to summarize a longitudinal comparison. An analysis may estimate a treatment-group contrast at a selected assessment, compare change from baseline, or model the pattern across assessments. These are general examples, not descriptions of the analysis in this trial. The registry record does not identify a selected assessment for a single primary contrast or report a model for the repeated scores.

What does randomization contribute?

In general, random assignment is intended to make treatment groups comparable at the start of a trial, on average, with respect to measured and unmeasured characteristics. It does not guarantee that every characteristic will be balanced in a particular trial. Baseline descriptions and the analysis approach help readers assess the realized comparison. This record identifies randomized allocation but does not report baseline outcome values, covariate balance, allocation concealment, or the randomization procedure.

Randomization also does not resolve what happens after assignment. Participants may not follow the assigned treatment, may discontinue, or may have missing outcome measurements. General analysis approaches differ in how they handle these circumstances. The analysis population and the handling of adherence, discontinuation, and missing observations are not reported in the registry record.

How should statistical significance be read?

In general, a p-value measures how unusual data at least as inconsistent with a stated null model would be, assuming the model and analysis conditions hold. It is not the probability that the null hypothesis is true, and it does not quantify the size or importance of an effect. A p-value should be read with an effect estimate and its uncertainty. No p-value or treatment-effect estimate for the primary outcome is reported in the registry record.

Repeated outcomes can raise a multiplicity question: testing several assessments or outcomes can increase the chance of at least one apparently notable result if no adjustment or prespecified testing strategy is used. This is a general consideration, not evidence that a particular procedure was or was not used. The registry record does not report a multiplicity plan. It lists WOMAC as primary and IKDC as secondary, but does not state how inference across time points or outcomes was controlled.

What do planning assumptions say?

The record describes a sample-size planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It also states that the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not a report of the trial's observed power. The record does not report the effect used for the illustration or the calculated sample-size values in the registry record for interpretation. Such planning figures cannot replace observed estimates and confidence intervals.

Over-dispersion is a general concern when outcome variability exceeds the assumptions of a statistical model, potentially making standard errors and confidence intervals too small if it is ignored. It is not reported whether over-dispersion is relevant to the WOMAC analysis, and the registry record does not identify the model used. Because WOMAC is described as a continuous score summarized by means, model assumptions and the distribution of scores could inform analysis, but no distributional information is reported.

Overall, the statistical methods needed to judge the primary comparison—model specification, analysis population, missing-data approach, and multiplicity handling—are not reported in the registry record. The endpoint definition and design are available, but no trial-specific method can be inferred from those details alone.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome is measured at baseline and at multiple follow-up assessments. The registry record does not specify which follow-up comparison is primary for inference, whether the measurements were analyzed jointly, or whether any adjustment for multiple assessments was used. It also lists the IKDC subjective score as a secondary outcome without reporting a hierarchy or multiplicity procedure. These details are not reported in the registry record.

Missing outcome data can affect the interpretation of a longitudinal comparison, particularly if the availability of measurements is related to participants' scores or treatment experience. In general, analysis methods make assumptions about why data are missing and how observed measurements can inform unobserved values. The record does not report the amount or pattern of missing WOMAC or IKDC data, the reasons for missingness, or the method used to address it.

The analysis population is not reported in the registry record. There is no statement about whether analyses followed randomized assignment, included only participants with available outcomes, or used another population definition. The record lists 90 enrolled participants, while the safety denominators are reported separately by group; those safety figures do not establish the population used for efficacy analyses.

Without a stated multiplicity approach, missing-data strategy, and analysis population, readers cannot determine how those choices may have affected the primary comparison. No trial-specific inference about these issues is possible from the registry record.

11. Safety Results

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

Deaths

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

Serious events with the highest arm-level rate: patient hospitalized due to unrelated ailments (2.0%), patient withdrawn due to unrelated ailments (2.0%).

The registry reports serious adverse event figures separately by group. In the PRP group, 0 of 41 participants at risk are recorded as having a serious adverse event, and 0 deaths are listed. In the BMC group, 2 of 49 participants at risk are recorded as having a serious adverse event, and 0 deaths are listed. The record lists no other adverse events in either group.

The registry's serious-event terms include “Patient Hospitalized due to Unrelated Ailments” at 2.0% and “Patient Withdrawn due to Unrelated Ailments” at 2.0%. The record labels these as unrelated ailments. The listed terms should not be read as evidence of treatment causation, and the figures alone do not establish a comparative safety difference.

These entries are descriptive counts, not a statistical comparison. The registry record does not report a safety analysis plan, confidence intervals, event timing, severity beyond the serious-event classification, or detailed ascertainment procedures. A zero count in a group does not prove that the risk is absent. The denominators are the numbers recorded as at risk for the respective safety entries; the record does not explain how those denominators relate to the population included in outcome analyses.

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

The registry record describes a randomized comparison of PRP and BMC for knee osteoarthritis, with WOMAC pain score as the primary outcome and IKDC subjective score as a secondary outcome. It reports the intended assessment schedule, enrollment, design, and selected safety counts. These registry entries clarify what the trial set out to compare.

The record does not report WOMAC or IKDC results, a treatment-effect estimate, confidence intervals, p-values, or an analysis method. It therefore does not show whether the groups' scores differed, how large any difference was, or how precisely a difference was estimated. The completed status does not fill that evidence gap.

Even when results are available, statistical evidence and clinical importance are distinct. General interpretation considers the estimate's size and uncertainty, the outcome scale, the study conduct, and the relevance of the difference to patients. A test result alone cannot establish clinical importance. In this record, the missing comparative results prevent those judgments altogether.

The safety counts are also limited. They report serious events by group, but do not provide a comparative analysis or enough detail to attribute events to treatment. The event labels recorded as unrelated ailments should be read as registry classifications, not as a complete account of safety.

Accordingly, the available record supports describing the trial's design and planned outcomes, but not a conclusion about comparative efficacy or safety. It cannot establish that either treatment is superior, equivalent, or ineffective. Those conclusions would require reported outcome estimates and adequate information about the analyses and data completeness.

13. Why This Trial Matters Statistically

This trial raises statistical questions common to randomized studies with patient-reported outcomes measured over time. Its primary measure is a continuous pain score, and the registry specifies means with 95% confidence intervals. Interpreting that kind of endpoint requires both a group contrast and an estimate of its uncertainty; the endpoint label alone is not an effect estimate.

The schedule includes multiple assessments, making the analysis strategy important. General approaches to repeated measurements can differ in how they account for within-participant correlation, baseline scores, incomplete follow-up, and the choice of assessment used for the main comparison. The registry record does not report the approach used, so the intended design cannot be connected to a specific inferential result.

The record also illustrates the distinction between trial completion and accessible results. It marks the study completed and records 90 enrolled, yet lists zero analyses and does not report comparative outcome values. Without those values, readers cannot evaluate effect size or precision, regardless of the trial's design.

Finally, the separate safety counts demonstrate why denominators and event definitions matter. Counts can describe what the registry records, but by themselves they do not provide adjusted comparisons or causal attribution. The record's limitations make clear that statistical interpretation depends not only on a planned endpoint and randomized allocation, but also on transparent reporting of estimates, uncertainty, analysis choices, and data completeness.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record does not report the primary WOMAC results, despite identifying the measure and its follow-up schedule. It also does not report the secondary IKDC results. No treatment contrasts, confidence intervals, p-values, or detailed analyses are listed, and the record states that there are zero analyses. As a result, the trial's outcome findings cannot be assessed from the registry record.

The record does not specify the primary comparison among the listed assessment times, the statistical model, or how baseline scores were handled. It does not report an analysis population, missing-data strategy, multiplicity procedure, or whether analyses were adjusted for other variables. These omissions limit interpretation of both the intended estimand and the uncertainty that would accompany an estimate.

The trial is listed as open-label, with masking recorded as none. Further information about outcome assessment is not reported in the registry record. The arm descriptions are truncated, so the full intervention procedures cannot be reviewed from the descriptions. Eligibility criteria and detailed information about participant characteristics are also not reported in the registry record.

The safety entries include group-specific denominators and event counts but no comparative safety analysis or detailed event ascertainment information. The relationship between the safety populations and any efficacy analysis population is not reported. These limitations do not establish that a particular bias occurred; they identify information unavailable for evaluating the results.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Bone Marrow Aspirate Compared to Platelet Rich Plasma for Treating Knee Osteoarthritis — NCT03289416.
• Registry record last updated 2025-04-20; status last verified 2025-04.
• Results first posted 2025-04-20.
• 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

NCT03289416 is a completed, randomized, parallel-group, open-label phase 4 trial sponsored by Andrews Research & Education Foundation. It enrolled 90 participants with knee osteoarthritis and compared Platelet Rich Plasma (PRP), using Pure PRP II, with Bone Marrow Concentrate (BMC), using PureBMC.

The primary outcome was WOMAC pain score, defined on a scale from 0 to 20, with higher scores representing more pain. Measurements were scheduled at baseline, 1 month, 3 months, 6 months, 9 months, and 12 months. The listed secondary outcome was the IKDC subjective score.

The registry record does not report efficacy analyses or comparative outcome results. It records serious adverse events for 0 of 41 participants in the PRP group and 2 of 49 in the BMC group, with 0 deaths in both groups. The statistical analysis plan, missing-data methods, and analysis populations are not reported in the registry record.