Intra Articular Injections With Platelet Rich Plasma in Patients With Juvenile Osteochondritis Dissecans of the Knee: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Intra Articular Injections With Platelet Rich Plasma in Patients With Juvenile Osteochondritis Dissecans of the Knee (NCT02397278), a randomized na study. The primary outcome is Greater Cartilage Healing Measured by Glycosaminoglycan Content on dGEMRIC MRI.

2. Clinical Question

The study asked whether adding platelet-rich plasma (PRP) injections to conservative care could improve cartilage healing in patients with juvenile osteochondritis dissecans of the knee. The planned primary measure was glycosaminoglycan content assessed with post-contrast dGEMRIC MRI at 6 months. The study description also identifies pain, daily activities, sports activities, overall function, and symptoms as areas of interest. The registry record does not report numerical results for these clinical outcomes.

The registry record says the protocol was amended to include non-contrast studies because of difficulty recruiting patients. It does not report whether those non-contrast studies produced an alternative primary endpoint result. Therefore, the main question can be described from the planned outcome, but its answer cannot be inferred from the registry record. A planned comparison and a measured comparison are different: without the specified endpoint observations and an analysis, there is no estimate of the treatment contrast to interpret.

3. Trial Design

This was a randomized, single-masked, parallel-group trial listed as completed. The registry record gives enrollment as 15 and identifies the sponsor as University of Colorado, Denver. The study start is recorded as 2015-03, and primary completion as 2020-01-08. Phase is listed as NA. The registry record does not say who was masked, how randomization was generated or concealed, or whether the intended allocation was equal.

The intervention arm was assigned three PRP injections into the symptomatic knee, in addition to the brace and conservative-care instructions described in the arm record. The conventional-therapy arm received a hinged brace locked in extension, with weight bearing as tolerated, crutches for those with pain upon weight bearing, and a period of complete rest from impact activities. The arm descriptions are truncated in the registry record, so further details of progression and follow-up cannot be reconstructed from it.

The study description says the investigators intended to compare PRP with conservative therapy and to assess cartilage healing as well as pain, daily activities, sports activities, function, and symptoms. The planned primary MRI endpoint was at 6 months. Listed secondary outcomes include IKDC and KOOS measures, with KOOS recorded at baseline, 6 months, and 12 months. The registry record does not specify the scoring procedures, the time point for IKDC, or the analysis population for these measures.

Randomization is intended to make treatment groups comparable, on average, with respect to factors that can affect outcomes. In a small trial, chance differences between groups may nevertheless remain. The record does not report the randomization method, allocation concealment, masking details, or baseline group characteristics, so those features cannot be assessed. More importantly for interpreting efficacy, the intended post-contrast primary outcome was not collected, and the registry record does not report a replacement primary result.

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: This outcome measure for post-contrast dGEMRIC studies was not collected. The protocol was amended to include non-contrast studies due to difficulty recruiting patients.

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 Greater Cartilage Healing Measured by Glycosaminoglycan Content on dGEMRIC MRI, measured over 6 months.

The planned primary endpoint was greater cartilage healing, measured by glycosaminoglycan content on dGEMRIC MRI at 6 months. dGEMRIC is an MRI approach used to assess cartilage composition; glycosaminoglycan content is relevant because it is a component of cartilage matrix. As a general measurement principle, a quantitative imaging endpoint can provide information about tissue characteristics that may not be captured by symptom scores alone. It does not, by itself, establish how a person feels or functions.

The registry description specifies post-contrast dGEMRIC studies, but states that this outcome was not collected. It further says the protocol was amended to include non-contrast studies because of difficulty recruiting patients. The record does not provide a numerical result for the planned endpoint, a description of an alternative endpoint definition, or an analysis of non-contrast imaging. Thus, the intended measure and timing can be identified, but there is no endpoint estimate from which to judge the direction or precision of a treatment difference.

Interpretation of an endpoint ordinarily depends on the measurement scale, summary statistic, group-level data, and uncertainty around the contrast. Those details are not reported for this primary measure. Nor does the registry record state a clinically meaningful threshold for glycosaminoglycan change. Even with an observed MRI difference, clinical relevance would require careful interpretation alongside symptoms and function rather than treating an imaging measure as a complete account of patient benefit.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods help distinguish a treatment comparison from a simple description of outcomes. The registry record identifies a randomized, single-masked, parallel design, but does not report the detailed statistical analysis plan. The concepts below are general explanations of how such data are often interpreted; they should not be read as methods confirmed for this trial.

What does randomization contribute?

In a randomized study, assignment is determined by a chance process rather than by participants’ or clinicians’ choice. This is intended to reduce systematic differences between treatment groups at baseline. Randomization does not guarantee that groups will be identical, especially in a small study, and it does not address missing outcomes that arise after assignment. To assess the process, readers would ordinarily need details about sequence generation, concealment, and the analysis population. Those details are not reported in the registry record.

What does a treatment effect estimate represent?

A treatment effect is a defined contrast between outcomes under the compared strategies. The contrast might be a difference in group means, a difference in proportions, or another quantity appropriate to the outcome scale. The choice must fit the outcome and the clinical question. A useful estimate also needs a clear time point and population. Here, the planned primary measure and its time point are stated, but the intended post-contrast outcome was not collected and no primary estimate is reported. The registry record therefore does not support calculation or interpretation of a treatment contrast.

How should uncertainty be read?

A confidence interval is a general way to communicate the range of effect sizes compatible with the observed data under a specified statistical model. A narrow interval indicates greater precision than a wide interval, while an interval spanning effects in different directions may leave the result uncertain. A confidence interval does not mean that a particular probability has been assigned to the fixed true effect. No primary estimate or confidence interval is reported in the registry record, so precision for the intended MRI endpoint cannot be assessed.

What do significance tests answer?

A significance test evaluates data against a specified null hypothesis using a chosen model and significance threshold. A p-value is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. Interpretation should consider the estimate, its uncertainty, the outcome definition, and the analysis plan together. The registry record does not report an analysis for the primary endpoint or a p-value for it. No significance conclusion can be drawn from the endpoint's non-collection.

Why do outcome definitions and missingness matter?

Changing a measurement procedure can affect what is measured and how results are compared. The record says post-contrast dGEMRIC was not collected and the protocol was amended to include non-contrast studies because of difficulty recruiting patients. It does not report a replacement endpoint definition or an analysis linking the amended imaging to the original primary question. When outcomes are missing, the implications depend on why they are missing, which participants are affected, and the assumptions used in analysis. Those details are not reported in the registry record.

As a general principle, analyzing only participants with observed data can produce a biased comparison if observation is related to treatment or outcome. Other approaches may use explicit assumptions or sensitivity analyses to examine the effect of missingness. The registry record does not report which approach, if any, was used. Similarly, a per-protocol analysis and an analysis based on randomized assignment answer different questions; the record does not identify an analysis population for the outcomes listed.

How should planning illustrations be interpreted?

The registry record describes planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation; the effect to detect is described as a fraction of the observed effect. These are planning assumptions, not the trial's reported design justification. The registry record does not report the sample-size justification or the observed effect underlying a particular planning contrast. The illustrations are not observed power and cannot substitute for an analysis of trial outcomes. Because the primary endpoint was not collected, the connection between those planning assumptions and the intended primary MRI question is not established in the record.

In general, over-dispersion means outcome variability is greater than a model assumes; if not handled, uncertainty may be understated. The registry record does not report whether over-dispersion was relevant or whether any model was fitted. For repeated measurements, methods may account for correlation among measurements from the same participant, but the record does not report a repeated-measures model or other strategy for the listed KOOS time points. These are considerations for interpreting an analysis, not claims about methods used in this study.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists six outcome measures, including the primary MRI measure and secondary clinical measures involving IKDC and KOOS. Multiple outcomes and time points create a multiplicity issue: the more comparisons considered, the greater the chance that some results appear unusual by chance if each is tested separately. General approaches include identifying a primary comparison in advance, adjusting for multiple testing, or treating secondary analyses as exploratory. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or analyses for the listed measures.

The intended primary outcome was not collected. The record says the protocol was amended to include non-contrast studies because of difficulty recruiting patients, but it does not explain how that amendment affected the endpoint hierarchy or what primary analysis replaced the planned post-contrast measure. This leaves uncertainty about which outcome, if any, was intended to carry the main inferential claim.

Missing-data interpretation depends on how many outcomes were unavailable, why they were unavailable, and how the analysis handled them. Those details are not reported in the registry record. It does not report an intention-to-treat analysis, a per-protocol analysis, imputation, sensitivity analyses, or the analysis population for the clinical outcomes. The stated enrollment is 15, but the record does not provide outcome-specific denominators for those measures. Therefore, neither completeness of follow-up nor the possible effect of missingness can be assessed from the listed information.

The absence of reported analyses is distinct from a finding of no difference. Without outcome estimates, uncertainty intervals, and a stated analysis population, readers cannot judge the size, direction, or robustness of any treatment comparison. The record reports 0 analyses, so claims based on inferential testing are not supported by its analysis information.

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 5% reporting threshold.

The registry record reports adverse-event counts by group. In the PRP group, 7 participants were listed at risk for serious adverse events, with 0 affected; in the conventional-therapy group, 8 were listed at risk, with 0 affected. For other adverse events, the corresponding entries are 7 at risk and 0 affected in the PRP group, and 8 at risk and 0 affected in the conventional-therapy group. Deaths are recorded as 0 in both groups, and no serious-event terms are listed.

These are event counts as recorded, not a complete account of all possible safety outcomes. A zero count means no events were entered in that category for the recorded group; it does not prove that the intervention has no risk. The registry record does not report event definitions, follow-up duration for safety, severity details beyond the serious/other categories, or whether non-serious events were actively collected. It also does not report an exposure-adjusted analysis or a comparative safety test.

The groups are small, so the absence of recorded events cannot rule out uncommon harms or establish equivalence in safety. The counts should be read descriptively and alongside the limitations of the registry record, rather than as evidence that either strategy is definitively safe.

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

The record shows that investigators planned a randomized comparison of PRP injections plus conservative care against conventional therapy for juvenile osteochondritis dissecans of the knee. Its central MRI question concerned glycosaminoglycan content on post-contrast dGEMRIC at 6 months. The record explicitly states that this outcome was not collected. Accordingly, it does not provide a result that establishes whether the groups differed in the intended cartilage-healing measure.

The study description also identifies pain, daily activities, sports activities, function, and symptoms as important areas of interest. IKDC and KOOS measures are listed, including KOOS at baseline, 6 months, and 12 months. However, numerical results and analyses for these measures are not reported in the registry record. It is not possible to infer improvement, no improvement, or a difference between groups from the fact that outcomes were listed.

The adverse-event record contains zero reported serious and other adverse events in both groups, and zero deaths in both groups. Those figures describe the entries in the registry record; they do not establish that no event occurred outside the recorded categories or that risks are equal. No comparative safety estimate is reported.

In general, a randomized comparison can support causal interpretation when the outcome is measured consistently, follow-up is adequate, and the analysis follows a clearly stated plan. The registry record does not provide enough information to evaluate those conditions for the primary outcome. It also does not report masking details beyond single masking, analysis populations, missing-data methods, or a multiplicity plan. These gaps constrain interpretation independently of the outcome's non-collection.

The record therefore supports a description of the intended question, design, amendment, and recorded safety counts. It does not support a conclusion that PRP improves cartilage healing, pain, or function, nor a conclusion that it fails to do so. Absence of a reported efficacy result is not evidence of no effect. The result is unavailable for the planned primary endpoint, and the listed clinical outcomes have no numerical results reported in the registry record.

13. Why This Trial Matters Statistically

This trial illustrates why a study’s endpoint and its actual data collection must be considered together. The primary question was framed around cartilage healing measured by post-contrast dGEMRIC MRI at 6 months. The registry record states that this endpoint was not collected and that non-contrast studies were added after difficulty recruiting patients. Without a reported result for the specified measure or a clearly described replacement, the central statistical question remains unanswered in the record.

The case also demonstrates that a randomized design does not by itself guarantee an interpretable treatment-effect estimate. Random allocation can strengthen a comparison, but inference still requires outcome observations, transparent analysis methods, and clear reporting of missing data and uncertainty. Here, the record reports enrollment of 15 but provides no primary endpoint estimate or analysis. The clinical outcomes are listed, yet numerical results are not reported.

Safety counts require similarly careful interpretation. No serious or other adverse events and no deaths are recorded in either group, but descriptive zero counts do not establish absence of risk, particularly when the registry record does not provide details about event collection and follow-up.

For clinical researchers, this record highlights the value of reporting protocol changes, endpoint definitions, analysis populations, missing-data handling, and estimates with uncertainty. These details allow readers to distinguish an unmeasured outcome from a measured outcome that showed little difference, and to evaluate whether a revised measurement still addresses the original question. Statistical transparency is essential even when a study is completed, because completion status alone does not establish that its intended comparison can be answered.

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 most direct limitation is that the planned primary outcome—post-contrast dGEMRIC glycosaminoglycan content at 6 months—was not collected. The record attributes this to a protocol amendment that included non-contrast studies because of difficulty recruiting patients. It does not report an alternative primary outcome result or explain whether the non-contrast imaging could answer the original endpoint question.

Enrollment is listed as 15, and the registry record does not report group baseline characteristics or outcome-specific participant counts. The adverse-event entries list 7 at risk in the PRP group and 8 in conventional therapy, but those safety denominators do not establish denominators for efficacy outcomes. The arm descriptions are truncated, so the full treatment and follow-up procedures cannot be assessed from the record.

Important design and analysis details are also absent. The record identifies single masking but not who was masked. It does not report the randomization method, allocation concealment, a sample-size justification, a statistical analysis plan, the analysis population, missing-data methods, or a multiplicity strategy. It lists clinical outcomes but does not report their numerical results or analyses. Consequently, effect size, precision, and robustness cannot be evaluated.

Finally, the recorded absence of adverse events is descriptive and cannot rule out unrecorded events or uncommon harms. The record does not provide enough detail about safety definitions, ascertainment, or follow-up to interpret those counts beyond their recorded categories. These limitations are specific to the information available in the registry record and constrain conclusions about efficacy and safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Intra Articular Injections With Platelet Rich Plasma in Patients With Juvenile Osteochondritis Dissecans of the Knee — NCT02397278.
• Registry record last updated 2021-08-05; status last verified 2021-07.
• Results first posted 2021-08-05.
• 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

NCT02397278 is a completed, randomized, single-masked, parallel-group study sponsored by University of Colorado, Denver. It compares three intra-articular PRP injections plus conservative care with conventional therapy for juvenile osteochondritis dissecans of the knee. Enrollment is listed as 15; the study start is 2015-03 and primary completion is 2020-01-08.

The planned primary outcome was glycosaminoglycan content measured by post-contrast dGEMRIC MRI at 6 months. The registry record states that this outcome was not collected and that the protocol was amended to include non-contrast studies because of difficulty recruiting patients. IKDC and KOOS clinical outcomes are listed, but numerical results and analyses are not reported in the registry record.

Recorded serious and other adverse events are 0 in each group, and deaths are recorded as 0 in both groups. The registry record does not provide an analyzable result for the intended primary question or enough methodological detail to assess efficacy analyses.