In Vivo Arthroscopic Behavior of the Infrapatellar Plica of the Knee: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for In Vivo Arthroscopic Behavior of the Infrapatellar Plica of the Knee (NCT00643487), a registered phase not stated study. The primary outcome is Number of Participants With Successful Recording..

2. Clinical Question

The study concerns the infrapatellar plica (IPP), a structure described in the registry summary as a vestigial remnant from embryonic development. Its stated purpose was to document the plica’s mechanical behavior during knee movement, using arthroscopic video and fluoroscopic imaging. The registry summary notes that the relationship between the IPP and anterior knee pain was unclear; the study’s stated measurement focus was the observed motion of the plica and the surrounding plica-fat pad complex, rather than a direct test of pain relief.

The primary outcome is titled Number of Participants With Successful Recording. Its description defines a complete recording by visualization of the plica, central body, and fat pad, followed by a series of maneuvers demonstrating the complex’s mechanical behavior. The registry reports a complete recording in 2 patients. It does not report a pain outcome, a comparison of pain before and after an intervention, or a clinical efficacy analysis. Accordingly, the central question addressed by the posted result is whether the specified recording was obtained, not whether resection changes symptoms.

3. Trial Design

NCT00643487 is listed as a completed study sponsored by State University of New York - Upstate Medical University. The registry gives a start date of 2006-02 and a primary completion date of 2013-01. Enrollment was 8. The listed condition is Anterior Knee Pain Syndrome, and the listed intervention is a procedure described as observation of the behavior of the infrapatellar plica.

The record does not describe a randomized allocation. It lists one intervention and provides no concurrent comparator arm. The registry’s own caution states that this is not a randomized comparison and that the arms are not a like-for-like control comparison. There is therefore no basis in this record for treating the study as a controlled estimate of an intervention’s effect.

The brief summary describes an imaging sequence during arthroscopy. It states that the plica’s behavior would be recorded by video, with contrast material and fluoroscopy used to visualize motion during a standard series of maneuvers. It further describes resection of the plica and additional fluoroscopy without plical attachment, intended to assess kinematic behavior after resection. These details describe the planned procedural sequence in the summary; the registry does not report how many participants completed each part of it or provide a numerical before-and-after comparison.

The primary outcome is a count of participants with a successful, complete recording. One outcome measure is listed, and no analyses are listed. The record does not report a statistical analysis plan, a sample-size justification, interim analyses, a defined analysis population, or a protocol for handling missing observations. It also does not explain whether every enrolled participant was included in the primary outcome assessment. Completion status and enrollment alone do not establish that all participants contributed a usable recording.

Because the design is descriptive and the listed outcome concerns recording success, the result is best read as a report of observed procedural documentation. It does not provide a randomized contrast, a treatment-effect estimate, or an estimate of change in symptoms.

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:

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 Number of Participants With Successful Recording., measured over During procedure, on average one hour..

The primary endpoint is the number of participants with a successful recording during the procedure, with the timeframe stated as during the procedure, on average one hour. The outcome description says a complete recording required visualization of the plica, central body, and fat pad, and that participants then completed maneuvers demonstrating the mechanical behavior of the infrapatellar plica-fat pad complex. In the posted results, a complete recording was obtained in 2 patients.

This endpoint is used to characterize whether the imaging procedure produced the specified observation. For a study focused on kinematics, documenting that the relevant structures can be visualized together during motion is directly connected to the stated descriptive objective. It does not, by itself, quantify how much the structures moved, establish that their movement caused pain, or measure the effect of resection on pain or function.

The endpoint is reported as a participant count, not as a comparative treatment effect. Although enrollment was 8, the registry does not state the analysis denominator for this outcome or describe the outcome status of every enrolled participant. The result should therefore be read as the reported count of complete recordings, without converting it into a proportion or assuming that participants without a reported complete recording had a failed procedure. The definition and count also do not establish whether recordings were assessed using a prespecified scoring rule or independently reviewed; those details are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The posted result is a count endpoint: the outcome description concerns the number of participants with a complete recording. For a count of participants meeting a defined condition, the key interpretive elements are the condition’s definition, the number assessed, and the number meeting it. The registry describes the condition for a complete recording, and reports 2 patients with such a recording. It does not report the outcome denominator or describe the status of every enrolled participant, so the count cannot be safely converted into a fraction or rate.

What does a count communicate?

A count states how many observations met an outcome definition. It is useful for a descriptive question such as whether a planned imaging procedure produced a complete view of specified structures. It is different from a comparison between groups, where the analysis would estimate how outcomes differ under distinct assigned conditions. NCT00643487 lists one intervention and no concurrent comparator. Its primary result therefore describes participants with complete recordings rather than a between-group contrast.

The distinction between participants and procedures also matters. The endpoint is expressed as a number of participants, and the description refers to complete recordings in patients. The registry does not report repeated recording counts, a participant-level dataset, or a rule for handling multiple observations from one person. The result should be interpreted at the level actually described: participants with a complete recording.

Why does the denominator matter?

A count has limited meaning without knowing how many participants were assessed for that outcome. Enrollment was 8, but the record does not explicitly identify the number included in the endpoint analysis. It also does not state whether participants lacking a complete recording were classified as unsuccessful, had missing measurements, or were not assessed. Those possibilities have different meanings. General statistical practice distinguishes an observed failure from a missing or unrecorded result; the registry does not provide enough detail to classify any unreported outcome status.

A confidence interval is, in general, a range of values intended to express uncertainty around an estimate under specified assumptions. It does not guarantee that the true value lies within the range, and its interpretation depends on the design and analysis. No confidence interval is reported for this endpoint. With no denominator or analysis method stated, an uncertainty interval cannot be interpreted from the registry result alone. No numerical interval should be inferred from the posted count.

What can a comparison establish?

In general, a comparison requires clearly defined groups and an analysis that reflects how those groups were formed. Random assignment can help balance measured and unmeasured characteristics on average, while a nonrandom comparison may be affected by differences between groups. This record does not describe random allocation and does not list a concurrent control group. The registry’s caution also says the arms are not a like-for-like control comparison. Thus, the record does not support a randomized treatment-effect interpretation.

The summary describes observations before and after plica resection, including fluoroscopy after resection. A before-and-after sequence can be informative about motion within the same procedural setting, but interpretation would depend on the measurements, timing, completeness, and analysis. The registry does not post numerical kinematic measurements or a statistical comparison of observations with and without plical attachment. Consequently, the described sequence is not itself evidence of a quantified mechanical change.

What do the planning assumptions mean?

The registry includes a description of planning illustrations based on an observed effect. It specifies a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. These are planning assumptions, not reported features of an inferential analysis of the observed participants. The record does not give a trial-specific sample-size justification or report that the study enrolled according to those two-arm assumptions.

In general, a sample-size calculation asks how many observations a proposed design would need to have a chosen chance of detecting a prespecified effect under stated assumptions. It is not a measure of the chance that the observed result is correct. When calculations are based on an observed effect, the result is particularly dependent on that effect estimate and the planning assumptions. Any such figures are planning illustrations, not observed power and not evidence that the study was adequately powered. The registry provides no numerical planning result in the record summarized for this study.

Equal allocation between two arms does not match the listed design, which has a single intervention and no concurrent comparator. A normal approximation is a statistical assumption that can simplify some planning calculations, but its suitability depends on the outcome and design. The record does not state how these planning assumptions were adapted to this descriptive procedural study. They should not be read as a reported analysis plan.

Why might variability matter?

General statistical analyses must account for the form of the outcome and the way observations vary. Over-dispersion is a general concern when count data vary more than a model assumes; ignoring it can make uncertainty appear smaller than it is. That issue is not established for this study’s primary endpoint, which is a count of participants meeting a recording criterion, rather than a reported repeated-event count. The registry gives no model, variance estimate, or inferential analysis from which over-dispersion could be assessed.

Similarly, statistical significance is not a substitute for a meaningful outcome definition or a valid comparison. A p-value, when reported, measures compatibility of data with a specified statistical model and null hypothesis; it does not measure the probability that a hypothesis is true or establish clinical importance. No p-value or hypothesis test is reported for the primary result. The proper reading is therefore descriptive and limited to the recording result stated in the registry.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and no analyses. That is not enough to establish that only one outcome was considered in the study, or that no additional outcomes were collected; it describes what is listed in the registry record. The record does not report a multiplicity plan, such as a prespecified hierarchy of outcomes or an adjustment for testing multiple hypotheses. With no listed hypothesis tests or p-values, the impact of multiplicity cannot be evaluated from the posted results.

Missing-data handling is also not reported in the registry record. Enrollment was 8, and a complete recording was reported in 2 patients, but the record does not state the number assessed for the primary endpoint or the status of the other participants. It does not say whether missing recordings were treated as unsuccessful, excluded, repeated, or handled by another method. Those distinctions matter because excluding participants with unavailable recordings can make an observed count different in meaning from a count that treats every unavailable recording as a failure.

The record does not identify an intention-to-treat, per-protocol, or other analysis population. It does not report participant flow, reasons for non-assessment, or a denominator used for the primary result. Therefore, enrollment should not be assumed to equal the analysis population. No imputation method or sensitivity analysis is reported.

In general, a multiplicity plan helps control the risk of misleading positive findings when multiple statistical questions are tested, while a missing-data plan clarifies how incomplete observations affect the analysis. These are distinct issues: the first concerns how many questions are assessed, and the second concerns the availability of measurements. Neither can be reconstructed from the reported complete-recording count. The primary result is best read as the stated count, with its analysis population and handling of incomplete data left unspecified.

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.

The adverse-event summary lists All Participants, with 8 at risk for serious events and 0 affected, and 8 at risk for other events and 0 affected. No serious-event terms are listed. These are registry counts; they do not establish how events were defined, how actively they were collected, or what observation period was used for safety monitoring.

The deaths entry is not reported in the registry record. It should not be interpreted as a reported count of zero deaths. Likewise, the listed zero counts refer to the serious and other event categories shown in the record; they do not establish that no symptoms, complications, or other experiences occurred outside those categories or that all participants had complete safety follow-up.

General interpretation of safety counts depends on clear event definitions, follow-up duration, completeness of ascertainment, and whether events are counted as events or as participants affected. The registry provides participant counts at risk and affected, but it does not provide further definitions or detailed event narratives. The absence of listed serious-event terms means no such terms appear in the record; it does not supply information about the monitoring process or prove the absence of every possible adverse experience.

These figures should therefore be read narrowly as the posted safety counts, not as a comprehensive assessment of procedural risk.

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

The result establishes that the registry reports complete recordings in 2 patients according to its stated definition: visualization of the plica, central body, and fat pad, followed by maneuvers demonstrating the mechanical behavior of the plica-fat pad complex. That observation is relevant to the study’s descriptive objective of documenting plica motion during arthroscopy.

The result does not establish a success rate because the analysis denominator and outcome status for all enrolled participants are not reported. Enrollment was 8, but the record does not explain whether all 8 were assessed for complete recording. It also does not allow an unreported outcome to be treated as a failed recording. The count is a limited description, not a population estimate.

The result does not show whether the infrapatellar plica causes anterior knee pain, whether removing it changes pain, or whether any change in movement after resection is clinically important. The brief summary describes a rationale related to pain and a procedure involving resection, but the primary endpoint is recording success, not symptoms or function. No clinical outcome comparison is reported.

Nor does the result demonstrate that one method of imaging is superior, that the same recording can be obtained reliably in other settings, or that the observed movement is reproducible. The registry does not report repeated-measure reliability, blinded assessment, or numerical kinematic measurements. These are separate questions that require data and methods not described in the posted results.

In general, descriptive findings can help characterize whether an observation is possible under a study’s procedural conditions. They do not, on their own, establish causation or comparative benefit. The absence of a concurrent comparator and the lack of a reported inferential analysis constrain interpretation further. The appropriate conclusion is narrow: complete visualization meeting the registry’s stated definition was reported for 2 patients, while the denominator, remaining outcomes, and clinical implications are not reported in the registry record.

13. Why This Trial Matters Statistically

This study is statistically notable because its stated objective and reported endpoint are descriptive, while the topic can invite a broader clinical interpretation. The registry summary discusses anterior knee pain and the uncertain relationship between pain and the infrapatellar plica. The primary outcome, however, counts participants with a complete recording. Keeping the measurement question separate from a clinical-effect question prevents the observed procedural result from being overstated.

The record also illustrates why a numerator without a clearly stated analysis denominator is difficult to interpret. Enrollment was 8, and 2 patients had complete recordings, but the registry does not say how many participants were assessed for the endpoint or what happened for each participant without a reported complete recording. That reporting gap limits interpretation even when the outcome itself is described.

Design features matter as well. There is no concurrent comparator and no randomized allocation described. The result therefore cannot support a controlled estimate of differences between treatment strategies. The brief summary’s described imaging before and after resection does not substitute for a reported numerical analysis of those observations. Stated procedural intent and posted statistical evidence are different things.

Finally, the record offers a useful reminder that sample-size planning assumptions are not results. Its planning description refers to a two-arm calculation framework, while the listed study intervention is a single procedural observation and no like-for-like comparator is reported. Any planning illustration should not be mistaken for the study’s design, observed power, or evidence of precision. These distinctions help readers identify what the record answers—and what remains unresolved—without inferring more than the reported count supports.

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 principal limitation is the gap between the narrow endpoint and the broader clinical motivation. The study summary discusses anterior knee pain and a proposed relationship to the infrapatellar plica, but the posted primary result concerns complete recording, not pain or function. No symptom outcome or clinical comparison is reported.

The registry does not report the denominator for the primary outcome or the status of every enrolled participant. Although enrollment was 8, only 2 complete recordings are specifically reported. The record does not clarify whether other participants were assessed, whether recordings were incomplete, or whether outcome data were unavailable. This prevents a clear interpretation of the count relative to all participants.

The design information also limits inference. No randomized allocation or concurrent comparator is listed, and the record cautions that the arms are not a like-for-like control comparison. The summary describes imaging after resection, but no numerical before-and-after kinematic result or analysis is posted. Therefore, the described procedure cannot be read as a reported estimate of the effect of resection on motion.

Additional methodological details are not reported in the registry record, including the statistical analysis plan, sample-size justification, interim analyses, analysis population, missing-data approach, and any method for assessing the recordings. The record also does not describe blinding, repeatability assessment, or detailed safety-monitoring definitions. These omissions do not prove that such methods were absent; they mean their use cannot be established from the registry.

Finally, enrollment of 8 gives a limited descriptive base, and the registry provides no confidence interval or other precision estimate. The result should not be generalized beyond the specific observation documented without further evidence.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: In Vivo Arthroscopic Behavior of the Infrapatellar Plica of the Knee — NCT00643487.
• Registry record last updated 2018-04-24; status last verified 2018-04.
• Results first posted 2016-05-18.
• 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

NCT00643487, titled In Vivo Arthroscopic Behavior of the Infrapatellar Plica of the Knee, is listed as completed and sponsored by State University of New York - Upstate Medical University. The registry lists Anterior Knee Pain Syndrome as the condition, enrollment of 8, a start date of 2006-02, and a primary completion date of 2013-01.

The listed procedure was observation of infrapatellar plica behavior. The primary outcome was the number of participants with a successful recording during the procedure, on average one hour. A complete recording was reported in 2 patients. One outcome measure is listed, and no analyses are listed.

The registry does not describe a randomized comparison or a like-for-like control group. It does not report the primary outcome denominator, the status of all enrolled participants, a statistical analysis plan, or a clinical outcome comparison. Safety counts list 0 affected for serious events and 0 affected for other events among 8 participants at risk in each category; deaths are not reported in the registry record.