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 Evaluation of the Safety and Effectiveness of the Kinamed Gem Ceramic Femoral Component for Total Knee Replacement (NCT00743717), a randomized phase 2 study. The primary outcome is Knee Score at 2 Years Post Operation.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00743717 |
| Phase | Phase 2 |
| Condition | Knee Osteoarthritis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 4 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Kinamed Incorporated |
| Results posted | Yes |
2. Clinical Question
Population
The registry lists knee osteoarthritis as the condition and describes a trial of total knee replacement. It records enrollment of four participants. The characteristics of the enrolled participants, eligibility criteria, and details of the analysis population are not reported in the registry record.
Intervention
The investigational device was a zirconia femoral component for the Gem Total Knee System. The study aim was to assess whether its safety and effectiveness were similar to those of implants used in total knee replacement. The registry does not report further details about device use or the surgical procedure.
Comparator
The comparison arm used a cobalt-chrome femoral component, abbreviated CoCr in the arm description. The registry’s brief summary refers to FDA-approved implants as the intended comparison, but the posted arm description identifies the control component as cobalt chrome. Further details about the control device are not reported in the registry record.
Primary question
The primary outcome was Knee Score at two years after operation, with a criterion of a score greater than 80 points used to assess success. The study summary states that the hypotheses concerned equivalence in patient success rate and complication-free rate. The posted primary outcome, however, is a group mean score with a full range; no formal equivalence analysis or participant-level success counts are reported. The registry therefore presents descriptive outcome values, rather than a reported test establishing whether the components are equivalent.
3. Trial Design
This was a Phase 2, randomized, single-masked, parallel-group trial, and its status is completed. It evaluated the zirconia femoral component against a cobalt-chrome femoral component for total knee replacement. Enrollment was four. The registry reports two participants in each arm for the primary outcome.
The study began in 2004-02, and primary completion was recorded as 2012-12. These dates describe the registry record; they do not establish how long each participant was followed. The primary outcome timeframe is described as within two years, while the outcome title refers to two years post operation. More precise timing or visit-window details are not reported in the registry record.
Random allocation indicates that assignment was intended to be determined by a random process. The method used to generate the allocation sequence, conceal assignments, and handle deviations is not reported in the registry record. Masking is described as single, but the identity of the masked parties is not reported. The record does not provide arm-specific treatment or follow-up details beyond the component descriptions.
The brief summary frames the aim as evaluating similarity in patient success rate and complication-free rate. The posted primary outcome is a mean Knee Score, and the registry contains no analysis records. A protocol, detailed statistical plan, equivalence margin, or account of planned interim analyses is not reported in the registry record. Consequently, the trial’s design labels and summary of intent should not be mistaken for a complete account of the methods used to analyse outcomes.
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 | 1: Zirconia Femoral | 2: CoCr Femoral |
|---|---|---|
| STARTED | 2 | 2 |
| COMPLETED | 2 | 2 |
| NOT COMPLETED | 0 | 0 |
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 | 1: Zirconia Femoral | 2: CoCr Femoral | Total |
|---|---|---|---|---|
| Participants analysed | 2 | 2 | 4 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 1 | 0 | 1 |
| Age, Categorical: >=65 years | Participants | 1 | 2 | 3 |
| Age Continuous | years | 62.5 (SD 13.4) | 65.5 (SD 4.94) | 64 (SD 8.45) |
| Sex: Female, Male: Female | Participants | 2 | 1 | 3 |
| Sex: Female, Male: Male | Participants | 0 | 1 | 1 |
| Region of Enrollment: United States | participants | 2 | 2 | 4 |
6. Primary Endpoint
The registry lists the primary outcome as Knee Score at 2 Years Post Operation, measured over within 2 years.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Full Range |
| Unit | units on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is Knee Score at two years post operation, described as being assessed within two years. The score is defined by the Knee Society Clinical Rating System and ranges from a minimum of 0, described as worst, to a maximum of 100, described as best. The registry states that a score greater than 80 was used as a criterion for assessing success.
A score of this kind summarizes a clinical assessment on a bounded scale. Reporting the group mean provides a concise description of the average score in each arm. The full range indicates the lowest and highest observed values reported for that arm; it does not show how scores are distributed between those endpoints. Individual scores and participant-level success counts are not reported.
The threshold and the mean answer different questions. The threshold describes a criterion for classifying success, whereas the mean describes the group’s average score. A mean above the threshold does not establish that every participant exceeded it, or reveal how many did so. The registry’s primary endpoint is therefore informative as a descriptive score summary, but it does not by itself provide the success-rate comparison described in the study summary.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The zirconia arm has a reported mean Knee Score of 91, with a full range from 85 to 97. The cobalt-chrome arm has a reported mean of 89, with a full range from 88 to 90. The outcome is expressed in units on a scale whose stated limits are 0 and 100. Both reported means are above the registry’s success criterion of greater than 80. These are descriptive group summaries, not evidence that each participant met the criterion.
There are two participants represented in each arm’s primary outcome summary. With so few observations, each participant’s score can have substantial influence on a group mean and range. The ranges show that the observed scores varied within each arm, but they do not establish the precision of the means in the way a confidence interval would. No standard deviations, standard errors, confidence intervals, p-values, or formal between-arm estimate are reported in the registry record.
The registry identifies equivalence in patient success rate and complication-free rate as hypotheses of interest. Establishing equivalence statistically generally requires a prespecified margin defining how large a difference could still be considered acceptably small, together with an estimate and uncertainty interval assessed against that margin. The margin, such an interval, and a formal equivalence result are not reported in the registry record. A small numerical separation between the posted means cannot substitute for this analysis.
The posted outcome is a mean score, while the stated success criterion is participant-level. The summary does not provide the number of participants in either arm whose score exceeded the criterion, and it does not report a comparative analysis of success rates. It also does not provide the complication-free rate. As a result, the posted data do not directly answer the two rate-based hypotheses described in the brief summary.
The registry reports zero serious adverse events and zero other adverse events in the reported at-risk count of two for each arm. This is a description of the posted event counts, not proof that no events occurred outside the recorded outcome data or that the devices have equal safety. Deaths are not reported. Overall, the results support a limited descriptive reading of the recorded scores and event counts; the record does not report the inferential analysis needed to draw a comparative conclusion.
9. Statistical Methods Explained
The posted primary outcome is a group mean and full range, rather than a reported model-based comparison. The registry has no analysis records and notes that values are missing or not estimable for a two-arm comparison for this other endpoint. Accordingly, the reported numbers can be read as descriptive summaries, but they do not supply a formal estimate of the between-arm effect with uncertainty.
What does the mean describe?
In general, a mean summarizes the central value of a set of observations by averaging the scores. It is easy to interpret on the original measurement scale, but it can be affected by individual observations, particularly when the group is small. The registry reports a mean for each component arm, but it does not provide the individual scores or a measure such as the standard deviation that would describe how scores are distributed around the mean.
The full range gives the lowest and highest reported values. It is useful for seeing the observed span, but it does not describe the pattern of values within that span or how stable the endpoints might be in another sample. A range is not a confidence interval. It should not be interpreted as a precision interval for the mean or as a prediction of the scores in future participants.
What would an inferential comparison add?
In general, a comparative analysis estimates how outcomes differ between groups and quantifies the uncertainty in that estimate. A confidence interval gives a range of values compatible with the data under the analysis assumptions; it is not a guarantee that the true effect lies within the interval. A p-value, when reported, addresses compatibility with a specified statistical null hypothesis and is not a measure of clinical importance. Neither a confidence interval nor a p-value is reported for the primary outcome in the registry record.
These concepts matter especially for an equivalence question. In general, failure to find a statistically significant difference does not demonstrate equivalence. An equivalence analysis needs a prespecified margin and an appropriate comparison of the estimated effect and its uncertainty with that margin. The registry describes an equivalence aim in its brief summary, but the margin, analysis method, and result are not reported. No conclusion about equivalence can therefore be drawn from the means alone.
How does the outcome criterion relate to the mean?
The registry describes a score greater than 80 as the criterion for assessing success. A group mean and a participant-level threshold summarize different features of the data. The mean can be above a threshold even when some individual scores are below it, and the mean alone does not reveal the count above the threshold. The posted record does not give participant-level success counts or a success-rate comparison. Nor does it give the complication-free rate named in the study summary.
What do the planning assumptions mean?
The registry’s planning description refers to a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. It describes the effect to detect as a stated fraction of the observed effect. In general, a sample-size calculation translates assumptions about an effect, variability, error tolerance, and design into a planning target. Such a target is not an observed result and does not show whether a completed trial had adequate power. The record does not report the planning outputs or the trial’s own sample-size justification. No observed power should be inferred from the posted group summaries.
Over-dispersion is a general concern when outcomes vary more than the statistical model assumes: standard errors can then be understated, making uncertainty appear smaller than it is. The registry does not report a model or a variance estimate for this endpoint, so there is no basis to assess over-dispersion or adjust for it. In a small trial, assumptions about outcome distributions and variance can be consequential, which makes transparent reporting of the analysis particularly important.
What does randomization contribute?
In general, randomization aims to make assignment independent of participant characteristics, reducing systematic differences between groups at assignment. It does not guarantee that small groups will be balanced on every characteristic, and it does not remedy missing outcomes or an unsuitable analysis. The record says the study was randomized, but allocation-generation details, concealment procedures, baseline characteristics, and an analysis population are not reported. The effect of these design features on the reported comparison cannot be assessed from the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome measure and no posted secondary outcomes. It reports no analysis records. The number of analyses available for review is therefore zero in the registry record, but this does not establish whether investigators conducted analyses that were not posted. A prespecified statistical analysis plan, including any hierarchy of outcomes or adjustment for multiple testing, is not reported in the registry record.
In general, multiplicity arises when several outcomes, comparisons, time points, or subgroup analyses are tested. Conducting many tests can increase the chance of at least one apparently notable result by chance. Approaches such as prespecifying a primary comparison, prioritizing outcomes, or adjusting inference can help address that issue. The registry record does not provide enough information to determine what multiplicity considerations were planned or applied. The single listed primary measure should not be taken as evidence that no other analyses were performed.
Participant flow, missing outcome counts, and reasons for missingness are not reported in the registry record. The posted primary outcome summaries each have two participants, but that alone does not establish whether all randomized participants were included in an intended analysis population or whether observations were missing at other time points. The analysis population, handling of missing data, and any imputation or sensitivity analyses are not reported.
In general, missingness can affect interpretation when the availability of an outcome is related to participant characteristics or results. Complete-case summaries describe the observed cases, but without information on missingness they may not represent all randomized participants. No claim about missing-data bias or its absence can be made from the posted summaries.
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 |
|---|---|---|---|
| 1: Zirconia Femoral | 0 | 2 | 0.0% |
| 2: CoCr Femoral | 0 | 2 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| 1: Zirconia Femoral | 0 of 2 |
| 2: CoCr Femoral | 0 of 2 |
The registry reports serious adverse events for an at-risk count of two in each arm: zero affected participants in the zirconia arm and zero in the cobalt-chrome arm. It also reports other adverse events for an at-risk count of two in each arm, with zero affected participants in each. These are the event counts recorded in the registry.
Zero recorded events in these small groups does not establish that the underlying risk is zero, nor does it show that risks are equal between the components. With so few participants, the data provide limited information about uncommon or delayed harms. The registry does not list serious-event terms, and deaths are not reported. Follow-up details for safety outcomes, event definitions, and whether events were counted per participant or in another way are not reported in the registry record.
In general, an at-risk denominator identifies the group considered for an event outcome, while an affected count records participants reported to have experienced it. These figures should be interpreted within the registry’s reporting scope. They do not supply a comprehensive safety profile or a formal comparison of adverse-event rates.
12. What the Result Does, and Does Not, Mean
The posted results establish that the registry contains descriptive Knee Score summaries for the zirconia and cobalt-chrome arms, as well as adverse-event counts. The zirconia arm’s mean score is 91, with a full range of 85 to 97; the cobalt-chrome arm’s mean is 89, with a full range of 88 to 90. The registry identifies scores greater than 80 as meeting its criterion for assessing success. The summaries do not state how many individual participants met that criterion.
These results do not establish that the devices are equivalent. The study summary names equivalence in success rate and complication-free rate as the hypotheses of interest, but no equivalence margin, formal test, interval estimate, or analysis result is reported. Similar-looking group means are not a substitute for a prespecified equivalence analysis. Nor can the means determine the proportion of participants who succeeded or remained complication-free.
The event counts record zero serious adverse events and zero other adverse events among the at-risk participants in each arm. Those observations do not demonstrate equal safety or rule out harms. The registry does not report deaths, and the small amount of posted safety information limits what can be concluded.
In general, a trial’s findings apply most directly to the population and conduct represented by its data. The registry does not report participant characteristics, full eligibility criteria, detailed follow-up, or the analysis population. Those omissions restrict assessment of how broadly the posted results might apply. The record supports a descriptive account of the reported observations, not a treatment recommendation or a definitive comparative conclusion.
13. Why This Trial Matters Statistically
This trial illustrates a distinction that is central to clinical statistics: a study’s stated objective and its posted outcome summaries are not necessarily the same thing as a reported analysis answering that objective. The summary describes equivalence in patient success rate and complication-free rate. The posted primary measure is a mean Knee Score, while the registry gives neither participant-level success counts nor a complication-free rate comparison.
Equivalence is a statistical claim requiring more than an absence of an obvious difference in group summaries. In general, investigators must define a margin for acceptable differences and interpret an estimate and its uncertainty relative to that margin. The registry does not report those elements. This makes the record useful for understanding why trial objectives, endpoint definitions, and analysis reporting need to align.
The trial also shows why sample size and precision matter. The registry reports two participants per arm for the primary outcome. Means and ranges can be calculated from observed data, but small groups give limited information about the variability and uncertainty of a comparison. A planning calculation, where available, is not evidence that a trial has demonstrated an effect or equivalence; the registry’s planning description is not accompanied by reported calculation outputs.
Finally, a threshold-based success definition and a continuous score answer related but distinct questions. Reporting a mean does not reveal how many individuals crossed the threshold. Clear reporting of participant-level outcomes, missingness, analysis populations, and uncertainty would be needed to connect the endpoint to the stated clinical hypotheses. The registry record underscores the importance of complete results reporting for interpreting a small randomized trial.
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 interpretation is the small number of participants represented in the arm-level primary outcome summaries: two per arm. The registry reports means and full ranges, but no standard deviations, confidence intervals, or formal comparison. The precision of the group means and any between-arm difference therefore cannot be assessed from the posted results.
The primary outcome reporting does not directly match the success-rate hypotheses in the brief summary. Although greater than 80 is identified as a success criterion, individual threshold status and success rates are not reported. The complication-free rate is also not reported. An equivalence margin and formal equivalence analysis are absent from the registry record.
Further details that would help evaluate the results are not reported: participant characteristics, eligibility criteria, allocation procedures, identities of masked parties, baseline outcome values, participant flow, reasons for missing data, analysis populations, and the statistical analysis plan. The endpoint timeframe is described both as within two years and as two years post operation, without more precise timing information.
Safety interpretation is limited by the small at-risk counts and the absence of reported deaths, event definitions, detailed follow-up, or serious-event terms. The record also does not report the trial’s own sample-size justification or planning outputs. These limitations constrain conclusions about comparative performance, safety, precision, and applicability.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Evaluation of the Safety and Effectiveness of the Kinamed Gem Ceramic Femoral Component for Total Knee Replacement — NCT00743717.
- Registry record last updated 2013-05-27; status last verified 2013-05.
- Results first posted 2013-05-22.
- 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 Phase 2, randomized, single-masked, parallel-group trial of zirconia and cobalt-chrome femoral components for total knee replacement. Enrollment was four. The primary outcome was Knee Score at two years post operation, described as occurring within two years, with a score greater than 80 used as a success criterion.
The zirconia arm had a reported mean score of 91 and full range of 85 to 97; the cobalt-chrome arm had a mean of 89 and full range of 88 to 90. Each arm’s primary summary represents two participants. The registry reports zero serious adverse events and zero other adverse events in the at-risk count of two per arm; deaths are not reported.
No formal analysis records, comparative uncertainty estimates, success-rate comparison, or equivalence result are reported. The posted information is descriptive and does not establish equivalence or a comparative safety conclusion.