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 CM Asia Nail With AS2 Without AS2 （AS2 Study） (NCT03196193), a randomized na study. The primary outcome is Number of Patient With and Without Excessive Lag Screw Sliding Distance.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03196193 |
| Phase | NA |
| Condition | Trochanteric Fracture of Femur |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 240 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Zimmer Biomet |
| Results posted | Yes |
2. Clinical Question
Population
Patients with a trochanteric fracture of the femur treated with open reduction and internal fixation using a ZNN CM Asia nail. The registry record does not give further eligibility criteria or a more detailed description of the enrolled population.
Intervention
The ZNN CM Asia nail used with an Anterior Support Screw (AS2), intended to provide additional screw fixation to stabilize the bone fragment.
Comparator
The same ZNN CM Asia nail and open reduction and internal fixation technique without additional AS2 screw fixation.
Primary question
Does the proportion of patients whose lag screw sliding distance is below the registry's 4 mm threshold differ between the AS2 and no-AS2 groups at postoperative 2-3 week assessment? The registry describes the comparison but does not report its result.
The study is framed as a randomized controlled comparison of two fixation approaches. Its brief summary describes the intended primary question as whether reduction position is maintained at 3 weeks after surgery. The detailed endpoint description operationalizes that question using the relative position of the lag screw on CT images taken immediately after surgery and at postoperative 2-3 weeks.
The central statistical issue is whether the binary success classification differs between groups, not simply whether an individual screw moved. A sliding distance below 4 mm is classified as success; a distance equal to or greater than 4 mm is classified as failure. The registry does not provide group-specific success or failure counts, an estimated difference between groups, or uncertainty around such a difference. Accordingly, the clinical question can be described, but the comparative result cannot be determined from the registry record.
3. Trial Design
The AS2 Study is recorded as a randomized, parallel-group trial with quadruple masking. It compares open reduction and internal fixation using a ZNN CM Asia nail with an additional Anterior Support Screw against the same nail fixation without that additional screw. The record lists the condition as trochanteric fracture of the femur and the sponsor as Zimmer Biomet. The study status is completed.
The registry lists an enrollment of 240. The brief summary describes 120 cases in each arm and a maximum of 15 sites. Those are described as planned features in the summary; the primary-outcome analysis and the actual number analyzed in each group are not reported in the registry record. Safety denominators are listed separately and do not match the planned arm counts. The reason for this difference is not reported in the registry record.
The recorded start date is 2017-03-21 and the primary completion date is 2020-04-02. The brief summary describes a total study duration of 22months. The phase is recorded as NA. No further information about the masking procedures, allocation implementation, recruitment flow, or site-level enrollment is reported in the registry record.
The principal endpoint is assessed using CT measurements of lag screw sliding over the period from immediately after surgery to postoperative 2-3 weeks. The record also lists surgery time, CT image assessment, and intraoperative safety among secondary outcomes. It does not describe their analysis methods or report their findings. Although the study is marked completed, the registry record contains no primary-outcome comparison or analysis results. Completion status alone does not indicate what the results were or how precisely the groups differed.
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 | ZNN CM Asia With AS2 Technique | ZNN CM Asia Without AS2 Technique |
|---|---|---|
| STARTED | 121 | 119 |
| COMPLETED | 118 | 119 |
| NOT COMPLETED | 3 | 0 |
Reasons for not completing this period:
| Reason | ZNN CM Asia With AS2 Technique | ZNN CM Asia Without AS2 Technique |
|---|---|---|
| Adverse Event | 1 | 0 |
| Computed Tomography (CT) data missing | 2 | 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 | ZNN CM Asia With AS2 Technique | ZNN CM Asia Without AS2 Technique | Total |
|---|---|---|---|---|
| Participants analysed | 118 | 119 | 237 | |
| Age, Continuous | years | 85.9 (SD 8.9) | 86.7 (SD 7.9) | 86.3 (SD 8.4) |
| Sex: Female, Male: Female | Participants | 103 | 97 | 200 |
| Sex: Female, Male: Male | Participants | 15 | 22 | 37 |
| Race and Ethnicity Not Collected | Participants | — | — | 0 |
| Region of Enrollment: Japan | participants | 118 | 119 | 237 |
| Height | cm | 148.9 (SD 8.8) | 150.0 (SD 9.0) | 149.4 (SD 8.9) |
| Weight | kg | 45.3 (SD 9.8) | 46.2 (SD 9.3) | 45.8 (SD 9.6) |
6. Primary Endpoint
The registry lists the primary outcome as Number of Patient With and Without Excessive Lag Screw Sliding Distance, measured over Postoperative 2-3 week.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint counts patients according to whether their lag screw sliding distance meets a binary threshold. The measurement is the relative position of the lag screw between CT images taken immediately after surgery and at postoperative 2-3 weeks. A distance below 4 mm is defined as success, while a distance equal to or greater than 4 mm is defined as failure. The brief summary describes the underlying objective as comparing reduction position maintenance at 3 weeks.
This endpoint turns a measured change in position into a clinically interpretable classification for a group comparison. A binary outcome can be summarized by the number or proportion of participants in each category, then compared between randomized groups. The threshold also makes the endpoint definition explicit: observations on either side of the boundary are assigned different classifications. The registry does not report the observed counts in either category, so the direction and magnitude of any group difference cannot be stated.
As a general statistical consideration, converting a continuous measurement into categories can make a result easier to communicate, but it discards information about how far measurements fall from the threshold. Participants just below and well below the boundary share a success classification, just as participants at or above it share a failure classification. The registry does not provide the underlying sliding-distance measurements, so the distribution around the threshold cannot be assessed. It also does not report measurement reproducibility or any further details of CT assessment.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the design and endpoint definition, but it does not provide the primary-outcome counts or a between-group estimate. There is therefore no reported basis for describing which group had more successes or failures, whether the groups differed, or how precise a comparison would be. A completed study status does not substitute for outcome data.
The endpoint is binary. For an interpretable group comparison, readers would need the number classified as successful and the number classified as failures in each group, together with the analysis estimate and its uncertainty. The registry record does not report these. No confidence interval, p-value, or adjusted comparison is reported for the primary endpoint. The analysis results are not reported in the registry record.
Even if group counts were available, a numerical difference alone would not show how precisely the effect was estimated. A confidence interval, as a general statistical concept, gives a range of effect values compatible with the data under the method used. Its width reflects uncertainty, and the interpretation depends on the analysis and assumptions. No such interval is reported for this endpoint. The registry also does not identify an analysis model or explain whether the primary comparison was adjusted for any factors.
The endpoint's threshold is important to interpretation. A distance below 4 mm is called success, and a distance equal to or greater than 4 mm is called failure. This definition allows categorization, but does not show the actual distances or how many observations were close to the boundary. General statistical reasoning cautions that classifications near a cutoff can be sensitive to measurement variation; the registry does not report data that would allow that issue to be evaluated in this study.
The registry lists 240 as enrollment and describes planned allocation of 120 cases to each arm. Separately, the safety record lists 121 at risk in the AS2 group and 119 in the group without AS2. These safety denominators should not be assumed to be the denominators for the primary endpoint: the primary analysis populations are not reported in the registry record. The reason for the difference between planned arm sizes and safety counts is also not reported.
For these reasons, the posted record supports a description of the randomized comparison and the prespecified threshold, but not a conclusion about the comparative primary result. The absence of a reported estimate is not evidence that the groups were identical, and it is not evidence that they differed. The result and its precision are simply not reported in the registry record.
9. Statistical Methods Explained
The registry describes a randomized, parallel-group comparison with quadruple masking. Random allocation is intended, in general, to make treatment groups comparable in expectation, including with respect to factors that were not measured. That principle does not by itself establish that allocation was implemented as intended, that all randomized participants were analyzed, or that the groups were balanced in the realized trial. Further details about the allocation process and analysis populations are not reported in the registry record.
What is the endpoint?
The primary outcome is a participant count based on a binary classification of lag screw sliding distance. CT images immediately after surgery and at postoperative 2-3 weeks are compared to measure relative screw position. The registry defines success as a distance below 4 mm and failure as a distance equal to or greater than 4 mm. This definition sets the outcome rule, but the observed group counts are not reported.
In general, a binary outcome can be compared using a difference in proportions, a ratio of proportions, or a model-based effect measure. These methods answer related but distinct questions and can produce estimates with different interpretations. The record does not say which effect measure or statistical model was used for the primary outcome. None should be attributed to the trial without a reported analysis.
Why does uncertainty matter?
A point estimate is a single summary of an observed group contrast. A confidence interval, as a general concept, communicates statistical uncertainty around an estimate under a stated method. A narrower interval indicates greater precision under that method; a wider interval indicates less precision. Interpretation also depends on the endpoint definition, the analysis population, and potential missing observations. The registry does not report a point estimate or confidence interval for the primary endpoint, so precision cannot be assessed.
A p-value, in general, summarizes how incompatible the observed data are with a specified null model, given the analysis assumptions. It does not measure the size or clinical importance of an effect, and it does not establish that the null hypothesis is true or false. No primary-outcome p-value is reported in the registry record. It would therefore be inappropriate to characterize the comparison as statistically significant or not statistically significant.
How should the threshold be understood?
The cutoff gives the binary endpoint a clear operational rule, but categorization loses information about the exact measurement. As a general point, measurements close to a boundary may change categories with small measurement differences, while measurements far from it may be less sensitive to such variation. The record does not provide the underlying CT measurements, measurement reliability, or sensitivity analyses using another cutoff. The impact of categorization cannot be evaluated from the registry record.
Randomization supports a between-group comparison, but valid inference also depends on how participants are handled after allocation. For example, excluding participants without a follow-up CT can affect the comparison if missingness is related to outcome or treatment group. This is a general concern, not a claim about what occurred in this trial. The registry does not report missing endpoint counts, reasons for missingness, imputation methods, or a detailed analysis population.
What can safety counts show?
Safety counts describe recorded events among participants represented in the safety record. They are not a substitute for the primary efficacy comparison, and small event counts can make group estimates imprecise. General statistical methods for rare events may require approaches suited to sparse data; the registry record does not identify a method for comparing the safety groups. The reported serious-event counts are described separately under safety.
The enrollment statement and safety denominators describe different aspects of the record. The enrollment is listed as 240, and the brief summary says 120 cases per arm were planned. Safety denominators are listed as 121 and 119. The record does not explain the distinction or identify whether those safety populations correspond to randomized, treated, or otherwise defined participants.
What is not documented?
The registry record does not report a statistical analysis plan, a sample-size justification, a primary-outcome model, an interim-analysis plan, or multiplicity procedures. The posted results contain no primary-outcome analysis. These omissions mean that a reader cannot determine from the registry whether the endpoint definition or analysis changed, how uncertainty was calculated, or how multiple outcomes were handled. General statistical principles can explain why these details matter, but cannot establish which methods this trial used.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists the primary CT-based endpoint and secondary outcome domains of surgery time, CT image assessment, and intraoperative safety. It does not report a multiplicity strategy. In general, when several outcomes or comparisons are tested, the chance of at least one false-positive finding can increase if each is assessed without adjustment. Whether an adjustment is needed depends on the trial's testing plan and the claims intended. Neither that plan nor an adjustment method is reported in the registry record.
The record does not describe interim analyses, early stopping criteria, or any monitoring plan. Their presence or absence cannot be inferred from the completed status. A sample-size justification and the assumptions behind the planned enrollment are also not reported in the registry record.
Missing-data information is not reported for the primary endpoint. The record does not give the number of participants without the follow-up CT measurement, reasons for missing measurement, or methods for handling missing outcomes. It also does not describe whether the primary analysis included all randomized participants, only participants who received the procedure, or another defined population. These details matter because exclusions or incomplete follow-up can affect both the estimated group contrast and its uncertainty.
The safety record includes group-specific at-risk counts, but these do not establish the primary analysis denominators. No analysis populations for the primary or secondary outcomes are reported. The registry record therefore does not support a judgment about the effect of missing data, multiplicity, or analysis-population choices on the study's findings.
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 |
|---|---|---|---|
| ZNN CM Asia With AS2 Technique | 1 | 121 | 0.8% |
| ZNN CM Asia Without AS2 Technique | 0 | 119 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| ZNN CM Asia With AS2 Technique | 0 of 121 |
| ZNN CM Asia Without AS2 Technique | 0 of 119 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| ZNN CM Asia With AS2 Technique | 0 of 121 |
| ZNN CM Asia Without AS2 Technique | 0 of 119 |
Most frequent serious adverse event terms
| Event term | Organ system | ZNN CM Asia With AS2 Technique | ZNN CM Asia Without AS2 Technique |
|---|---|---|---|
| Cut-out | Musculoskeletal and connective tissue disorders | 1 of 121 | 0 of 119 |
Serious events with the highest arm-level rate: cut-out (0.8%).
The registry lists serious adverse events for the AS2 group as 1 affected participant among 121 at risk, and for the group without AS2 as 0 affected among 119 at risk. It lists 0 other adverse events and 0 deaths in each group. The serious adverse-event term identified as the top term is Cut-out, with a reported value of 0.8%.
These are descriptive safety figures. The registry does not report a statistical comparison of the groups for serious adverse events, a confidence interval, or details about event timing or severity beyond the serious-event classification. The Cut-out percentage is listed as a top serious term; the record does not state its group attribution in that term listing. It should not be treated as a separate group-specific estimate.
Rare or absent events provide limited information about comparative risk. In general, a zero count does not establish that an event cannot occur, and a small count does not support a precise estimate of a group difference. The reason the safety denominators differ from the planned allocation is not reported in the registry record. The primary endpoint is a separate CT-based measure and should not be inferred from these safety counts.
12. What the Result Does, and Does Not, Mean
The registry record describes a randomized comparison of ZNN CM Asia nail fixation with and without an Anterior Support Screw. It defines the primary outcome as a CT-based classification of lag screw sliding at postoperative 2-3 weeks, using a 4 mm threshold. It also records the study as completed and lists safety counts for each group.
What the record does not establish is the comparative primary result. It does not provide the number of participants meeting the success criterion in either group, the number classified as failures, or an effect estimate. Without those data, it is not possible to describe the direction or size of the group difference, or how precisely it was estimated. No conclusion about whether the groups differed on the primary endpoint can be drawn from the registry record.
The endpoint itself has a specific interpretation: it reflects whether measured screw sliding falls below the stated cutoff. It is not a report of all CT findings, and the registry does not include the underlying measurement distribution. General statistical reasoning also distinguishes a threshold-based endpoint from the full range of observed measurements; the registry does not allow assessment of how close measurements were to the boundary.
The safety record reports few serious events, with none recorded in the no-AS2 group and one in the AS2 group. These descriptive counts are not a comparative safety analysis and should not be used to infer a precise difference. The listed Cut-out term and percentage do not supply a complete account of the event's group attribution or other clinical details.
In short, the registry supports an account of the question, design, endpoint definition, and reported safety counts. It does not support a claim that one fixation approach produced a better primary outcome, a claim that they were equivalent, or a claim about the precision of any treatment effect. Those results are not reported in the registry record.
13. Why This Trial Matters Statistically
This trial addresses a focused statistical question: whether adding an Anterior Support Screw changes a CT-based classification of lag screw sliding after fixation of a trochanteric femur fracture. Because the endpoint is defined using a clear threshold and the study is randomized, the intended comparison can be stated directly: compare the proportion classified as successful in the AS2 group with the proportion in the group without AS2.
The case also illustrates why an outcome definition and a result are different things. A detailed measurement description and a prespecified threshold tell readers how the endpoint is intended to be classified. They do not reveal the observed group counts, the size of a contrast, or its uncertainty. Those results are not reported in the registry record, so statistical interpretation must remain limited to the design and measurement definition.
The safety record offers another useful distinction. Counts of adverse events can be described, but sparse counts do not automatically support a reliable estimate of comparative risk. Group denominators, event definitions, and an analysis method all matter. The registry reports some of these descriptive elements but not a statistical safety comparison.
Finally, the record shows why reporting analysis populations, missing outcomes, and multiplicity plans matters. Such details help readers understand what evidence a reported estimate represents and how much confidence to place in it. Their absence does not prove that a particular method was or was not used; it limits what can be evaluated from the registry. This distinction between a trial's design and its publicly reported analysis is central to sound clinical biostatistical interpretation.
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 for interpreting this trial from the registry is that the primary outcome results are not reported. Although the endpoint is described in detail, there are no group-specific success or failure counts, comparative estimates, confidence intervals, or p-values. The primary question therefore remains unanswered in the registry record.
The registry does not report the statistical analysis plan, model choice, analysis population, missing-data handling, or any sensitivity analyses. It also does not report whether the outcome definition or analytic approach changed during the study. These omissions limit assessment of the prespecified analysis and the robustness of any result.
The outcome uses a binary cutoff applied to CT-measured sliding distance. The underlying measurements, distribution around the cutoff, and assessment reliability are not reported. Consequently, readers cannot assess how observations were distributed or how sensitive classification might be to measurement variation. Additional details about CT acquisition and assessment are not reported in the registry record.
The planned enrollment and arm sizes are described in the summary, while the safety record gives different at-risk counts. The record does not explain this difference or clarify whether the safety populations align with the randomized groups. The reason for the discrepancy is not reported in the registry record.
Finally, the registry identifies secondary outcome domains but does not report their findings or a multiplicity strategy. It does not give further clinical eligibility details, recruitment flow, or site-level results. These are limitations of what can be evaluated from the registry record; they do not establish that the trial itself lacked the relevant procedures or analyses.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: CM Asia Nail With AS2 Without AS2 （AS2 Study） — NCT03196193.
- Registry record last updated 2020-09-29; status last verified 2020-09.
- Results first posted 2020-09-29.
- 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
NCT03196193 is a completed randomized, parallel-group study with quadruple masking, comparing ZNN CM Asia nail fixation with and without an Anterior Support Screw for trochanteric femur fractures. The registry lists enrollment of 240; the brief summary describes 120 cases per arm and a maximum of 15 sites. Recorded dates are 2017-03-21 for study start and 2020-04-02 for primary completion.
The primary endpoint counts participants according to CT-measured lag screw sliding at postoperative 2-3 weeks. Sliding below 4 mm is classified as success; a distance equal to or greater than 4 mm is classified as failure. The record also lists surgery time, CT image assessment, and intraoperative safety as secondary outcomes.
Primary-outcome counts and comparative analyses are not reported in the registry record. The safety record lists 1 serious adverse event among 121 at risk in the AS2 group and 0 among 119 at risk in the group without AS2. The record does not report a comparative safety analysis.