Vanguard TKA With KneeAlign 2 and Without KneeAlign 2: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Vanguard TKA With KneeAlign 2 and Without KneeAlign 2 (NCT02695329), a randomized na study. The primary outcome is Proportion of Subjects That Have Alignment Within 2 Degrees From Neutral on Tibia.

2. Clinical Question

The study asks whether tibial component alignment after total knee arthroplasty is more often within 2 degrees from neutral when surgery uses the KneeAlign 2 navigation system rather than conventional instruments. The condition listed is knee osteoarthritis. The comparison concerns the surgical instrumentation used during the procedure, not a comparison of different implants: both groups are described as receiving Vanguard total knee arthroplasty.

The primary endpoint is the number or proportion of participants whose tibial alignment falls within the stated threshold, assessed postoperatively at 6 months. The registry description says the intent is to compare the accuracy of tibial component alignment between the groups. This makes the clinical question one of comparative alignment precision as represented by a threshold-based outcome.

The registry record also lists outcomes for tibial posterior slope alignment and femoral varus/valgus angle within predetermined thresholds, along with adverse events and adverse device effects. These outcomes provide additional dimensions of alignment and safety that may be relevant to interpreting a navigation system. However, the record does not report their group-level results or statistical comparisons.

The central question can therefore be stated precisely, but its answer cannot be determined from the posted results described in the registry record. No primary endpoint counts, proportions, effect estimate, confidence interval, or test result are reported. The study’s stated objective is not itself evidence of a difference. Any conclusion about comparative alignment would require outcome data and an analysis that are not reported in the registry record.

3. Trial Design

This is a randomized, single-masked, parallel-group study comparing Vanguard total knee arthroplasty with KneeAlign 2 navigation against Vanguard total knee arthroplasty performed with conventional surgical instruments and without KneeAlign 2. The registry identifies the study as completed and reports enrollment of 100 participants. Its listed condition is knee osteoarthritis, and Zimmer Biomet is identified as the sponsor.

The intervention is a device, KneeAlign 2. In the navigation group, total knee arthroplasty is performed using the KneeAlign 2 navigation system. In the comparison group, surgery uses conventional surgical instruments without that navigation system. The descriptions therefore define the contrast as navigation-assisted versus conventional instrumentation within the Vanguard arthroplasty context.

The record gives a study start date of 2016-05-24 and a primary completion date of 2018-10-03. The phase is listed as not applicable. The allocation is randomized, the masking is listed as single, and the model is parallel. The registry record does not identify who was masked, so the masking description should not be interpreted as specifying whether participants, clinicians, assessors, or another group were unaware of assignment.

Although enrollment is reported, the registry material does not provide the number randomized to each arm for the primary endpoint, the number included in its analysis, or participant flow by group. The adverse-event figures list 50 participants at risk in each arm, but those safety counts do not establish the analysis population for the primary endpoint. The protocol details, including allocation procedures and the rationale for the design choices, 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:

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 Proportion of Subjects That Have Alignment Within 2 Degrees From Neutral on Tibia, measured over Postoperative 6 months.

The primary endpoint is the proportion of participants whose tibial alignment is within 2 degrees from neutral, with assessment specified at postoperative 6 months. The registry also labels the measure as a count of participants. These descriptions indicate a threshold-based endpoint: each participant is classified according to whether the observed alignment falls within the stated range, and the group result would ordinarily be expressed through the number or proportion meeting that criterion.

A threshold can make a technical measurement easier to interpret by distinguishing alignment inside a prespecified range from alignment outside it. Comparing the groups on this endpoint can address whether one approach is associated with more participants meeting the stated alignment criterion. It does not, by itself, show the full distribution of alignment measurements, how far measurements fall from neutral, or whether values just outside the threshold differ meaningfully from values farther away.

The registry description frames the endpoint as a way to compare the accuracy of tibial component alignment. The threshold and the postoperative assessment time are specified, but the measurement method, assessor, handling of missing measurements, and any prespecified analysis details are not reported in the registry record. Most importantly, the registry record does not report the participant counts or proportions meeting the threshold in either group. The endpoint’s definition is available; its comparative result is not.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical interpretation depends first on the distinction between an endpoint definition and an endpoint result. The registry specifies a threshold-based primary outcome: participants are classified according to whether tibial alignment is within 2 degrees from neutral at postoperative 6 months. That description identifies what would be counted. It does not state how many participants met the threshold in either group, nor does it report a comparison between groups.

What does a threshold-based outcome represent?

In general, a binary outcome places each observation into one of two categories, such as meeting or not meeting a defined criterion. A group-level summary can describe the count or proportion in the category of interest. Such a summary is straightforward to interpret, but it compresses information: it does not retain the exact measurement for each participant. Two groups could have similar proportions meeting a threshold while having different distributions of measurements, or a small change in measurements around the cutoff could alter classifications. These are general properties of threshold-based outcomes, not findings about this study.

The registry calls the endpoint a proportion and also identifies its unit as participants and its parameter as a count of participants. Those labels are compatible with counting participants who meet the criterion and expressing the count as a proportion of an eligible group. The record does not report the denominators used for the primary endpoint or how participants without an evaluable measurement were handled.

What would a group comparison tell the reader?

In general, a comparative analysis would report the outcome in each arm and an estimate of the difference or another contrast between arms. A confidence interval would describe the range of values reasonably compatible with the observed data under the statistical model and its assumptions. Its width conveys precision: a wider interval indicates greater uncertainty about the size of the contrast. A test result may address compatibility with a specified null hypothesis, but it does not by itself describe the magnitude or practical importance of a difference. These are general explanations; the registry record reports no primary comparison estimate, confidence interval, or test result for this trial.

Because the primary outcome is not reported by group, there is no posted estimate to interpret for direction, size, or precision. It would be inappropriate to reconstruct an effect from the study objective, enrollment, or safety counts. The registry record does not provide the primary outcome values needed for a recalculation.

How does randomization relate to inference?

Generally, random allocation aims to make assigned groups comparable with respect to measured and unmeasured baseline characteristics. It supports a causal comparison when the allocation process is implemented appropriately and the analysis follows a suitable approach. It does not eliminate the need to report baseline information, participant flow, outcome ascertainment, and analysis decisions. The record identifies the allocation as randomized, but the sequence-generation method, concealment procedures, baseline characteristics, and primary analysis population are not reported in the registry record.

The study is also described as single-masked. Masking can reduce some forms of bias when the people who might influence care, measurement, or reporting are unaware of assignment. The registry does not say who was masked or how masking was maintained. Therefore, the label alone is not enough to evaluate possible effects of knowledge of treatment assignment on alignment measurement or outcome recording.

What can the safety counts establish?

The safety summary lists serious adverse events, other adverse events, and deaths for each group. These are descriptive counts. In general, counts are easier to interpret when their definitions, observation periods, ascertainment procedures, and denominators are clear. The registry gives participants at risk and affected counts for the listed categories, but does not report further details such as event descriptions or statistical comparisons. Sparse counts, including zero counts, do not establish that an event is impossible or that the groups are equivalent; they describe only what is recorded in this study.

The record lists no serious-event terms. It reports no deaths in either arm and reports one other adverse event in the KneeAlign 2 arm and zero in the conventional-instrument arm. The meaning of those categories should not be extended beyond the registry’s labels. In particular, the summary does not establish causation or provide enough detail to evaluate the nature or timing of the event.

What analysis details remain unknown?

The registry record does not report the primary statistical model or test, the handling of missing observations, any adjustment variables, or the analysis population. It also does not report whether there were interim analyses or a prespecified sample-size rationale. These omissions matter because analytic choices can affect how estimates are produced and interpreted. They cannot be filled in from general conventions or inferred from the randomized design.

More broadly, the outcome measure is a count-based binary endpoint rather than a continuous alignment value in the information available. A full statistical report could include both the threshold result and the underlying measurement distribution, as well as an estimate with uncertainty. That is a general reporting consideration, not a claim that these analyses were conducted. Since the posted registry information lacks the primary outcome data and analysis, statistical methods cannot recover the trial’s comparative result.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary endpoint and several secondary outcomes, but it does not report a statistical analysis plan explaining how those outcomes were to be analyzed or interpreted together. The secondary outcomes include tibial posterior slope alignment within a predetermined threshold, femoral varus/valgus angle within a predetermined threshold, and adverse events and/or adverse device effects. The record identifies four outcome measures in total, but does not provide results or analysis details for the alignment outcomes.

In general, when a study assesses multiple outcomes or makes multiple comparisons, the chance of observing at least one apparently notable result can increase. A prespecified strategy can clarify which outcome is primary and whether adjustments or other interpretive safeguards are planned. The registry record identifies the primary endpoint, but does not report any multiplicity adjustment, testing hierarchy, or related decision rules. It is therefore not possible to determine how multiplicity was handled.

Missing-data handling is also not reported. The record does not state how participants without an evaluable postoperative alignment measurement were treated, whether missingness was assessed by group, or whether any sensitivity analyses were planned. These details matter because a threshold-based endpoint requires an outcome classification, and unobserved measurements cannot automatically be treated as meeting or failing the criterion.

The record does not specify the primary analysis population, such as whether all randomized participants were intended for analysis or whether inclusion depended on available measurements or adherence. It also does not report participant flow by arm for the primary endpoint. The safety summary’s at-risk counts do not define the primary endpoint analysis population. In general, complete reporting of enrollment, assignment, follow-up, missing observations, and analysis populations helps readers assess whether exclusions could affect a comparison. Those details are not reported in 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 non-serious adverse event terms

The registry’s safety summary lists 50 participants at risk in each arm. It reports zero serious adverse events in the Vanguard with KneeAlign 2 group and zero in the Vanguard without KneeAlign 2 group. For other adverse events, it reports one affected participant in the KneeAlign 2 group and zero in the conventional-instrument group. Deaths are reported as zero in both groups.

These figures are descriptive counts in the categories used by the registry. They do not identify the nature, timing, severity, or duration of the other adverse event, and the record does not provide a list of serious-event terms. The figures also do not establish whether an event was caused by the device or procedure. The registry’s category for other adverse events should not be treated as interchangeable with a specific device-related outcome.

In general, a zero count means that no events in that category were recorded in the reported group; it does not prove that the underlying risk is zero. Sparse counts also provide limited information for comparing groups. The registry record does not report a statistical safety comparison, confidence interval, or additional event-level details. These counts should therefore be read as the posted descriptive safety information, not as proof of equivalence or a comprehensive account of all possible harms.

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

The registry record establishes that a randomized, parallel-group study compared Vanguard total knee arthroplasty with KneeAlign 2 navigation against the same arthroplasty approach using conventional instruments. Its stated primary question concerns the proportion of participants with tibial alignment within 2 degrees from neutral at postoperative 6 months. The study is listed as completed, with enrollment of 100 participants.

Those design details explain what the study was intended to examine, but they do not reveal the primary result. The registry record does not report the number of participants meeting the alignment threshold in either group, an effect estimate, or a measure of uncertainty. It therefore does not support a conclusion about whether the groups differed, the direction of any difference, or how precise an estimate might be. The study objective cannot substitute for observed outcome data.

The record also names additional alignment outcomes, but does not report their group results. The available safety summary reports zero serious adverse events and zero deaths in both groups, along with one other adverse event in the KneeAlign 2 group and zero in the conventional-instrument group. These limited counts describe the posted categories; they do not establish that there were no other safety concerns or that the approaches are equivalent in safety.

In general, statistical interpretation requires more than knowing that a trial was randomized and completed. Readers need the observed outcomes, denominators, analysis methods, missing-data information, and uncertainty around comparative estimates. For this trial, those primary efficacy details are not reported in the registry record. The defensible conclusion is consequently about the scope and limits of the record: it documents the question, design, and selected safety counts, but does not report the primary comparative finding.

13. Why This Trial Matters Statistically

This study presents a useful statistical question because it defines a technical outcome as a threshold-based measure of alignment and compares navigation-assisted surgery with conventional instrumentation in a randomized design. The contrast is specific: both groups are described as receiving Vanguard total knee arthroplasty, while use of KneeAlign 2 differs. That structure focuses the question on the navigation system rather than on a comparison between different named arthroplasty approaches.

Threshold outcomes can be accessible to readers because they classify whether a stated criterion is met. At the same time, they require careful reporting. The cutoff determines how measurements are grouped, and the resulting count does not show how close individual measurements are to the boundary or how the full distribution differs. In general, reporting both the threshold result and appropriate measurement detail can help readers understand what a classification captures and what it leaves out.

Randomization is also statistically important: in general, it is intended to support a fair comparison by reducing systematic differences in assignment. But a randomized label does not replace reporting the allocation procedures, participant flow, analysis population, outcome data, and uncertainty. Those elements are needed to assess how the intended comparison was carried out and how informative the estimate is.

Here, the registry identifies the primary endpoint and the completed study but does not report the outcome data or primary analysis. That absence is consequential: without group-level endpoint results, the central statistical question remains unanswered in the registry record. The study is therefore informative about how the comparison was framed, but the posted record does not permit evaluation of the comparative alignment result.

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 primary limitation for statistical interpretation is that the registry record does not report the primary endpoint results. Although the endpoint definition and assessment time are stated, there are no group-specific counts or proportions, no comparative estimate, and no confidence interval or test result. The direction, magnitude, and precision of the primary comparison are therefore unavailable.

The registry also does not report results for the listed secondary alignment outcomes. It names tibial posterior slope alignment and femoral varus/valgus angle within predetermined thresholds, but their participant counts and group comparisons are not reported. The endpoint measurement procedures, the assessor, and the operational definition of the secondary thresholds are not reported in the registry record.

Other information needed to evaluate the analysis is absent as well. The record does not report the primary analysis population, participant flow by arm, the number with evaluable alignment measurements, missing-data handling, or the statistical method used for the primary comparison. It does not report the random-sequence method, allocation concealment, or who was masked. The single-masked designation alone does not resolve those questions.

The registry record does not report the sample-size justification, statistical analysis plan, adjustment for multiple outcomes, or whether interim analyses were conducted. These omissions prevent assessment of whether the reported design was linked to a prespecified analysis strategy. The adverse-event summary is limited to category counts and does not describe the event recorded as an other adverse event or provide detailed event-level information. These limitations reflect what is not reported in the registry record and should not be replaced by assumptions about the trial’s conduct or analysis.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Vanguard TKA With KneeAlign 2 and Without KneeAlign 2 — NCT02695329.
• Registry record last updated 2020-02-12; status last verified 2020-01.
• Results first posted 2019-10-03.
• 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

NCT02695329 is a completed randomized, single-masked, parallel-group study sponsored by Zimmer Biomet. It enrolled 100 participants with knee osteoarthritis and compared Vanguard total knee arthroplasty using KneeAlign 2 navigation with Vanguard surgery using conventional instruments. The registry lists the study start as 2016-05-24 and primary completion as 2018-10-03.

The primary endpoint is tibial alignment within 2 degrees from neutral at postoperative 6 months. Secondary outcomes include tibial posterior slope alignment, femoral varus/valgus angle, and adverse events and/or adverse device effects. The registry record does not report the primary endpoint results, secondary alignment results, or a primary statistical analysis. Its safety summary lists 50 participants at risk in each arm, zero serious adverse events and deaths in both arms, and one other adverse event in the KneeAlign 2 arm versus zero in the conventional-instrument arm.