Wright Foot & Ankle Post-Market Observational Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Wright Foot & Ankle Post-Market Observational Study (NCT04118894), a registered phase not stated study. The primary outcome is EuroQol (EQ-5D-5L)..

2. Clinical Question

3. Trial Design

This is a post-market observational study of foot and ankle devices, rather than a randomized treatment comparison. The registry describes the study as multi-year, multi-site, multi-device and lists 10 sites. Its brief description states a minimum of 40 patients per device. That statement describes the study as registered; it does not establish how many participants were enrolled for each device or how many completed follow-up. Overall enrollment is listed as 119.

The study group comprises subjects treated with one or more approved or cleared Wright Medical products included in the study. No randomized allocation is described, and the method of allocation is not stated. There is no separate comparator arm described in the registry record, so the data do not constitute a like-for-like control comparison.

The study start date is 2020-01-22, and the primary completion date is 2022-12-08. Its status is TERMINATED. The reason for termination, the timing of termination, and whether follow-up ended as planned are not reported in the registry record. The listed sponsor is Stryker Trauma and Extremities.

The primary outcome is the EQ-5D-5L at 1 year, with change from preoperative through postoperative assessment described as the focus. Secondary outcomes named in the record are the Foot and Ankle Ability Measure, Safety Assessment, Surgeon Survey, and Patient Survey. The record lists five outcome measures overall, but does not provide results for these outcomes or explain the schedule and completeness of their assessments.

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.

Before assignment: No specific method (such as randomization, blinding or stratification) for assigning subjects was used in this protocol. Consecutive subjects at each site meeting all the eligibility criteria were enrolled in this study.

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 EuroQol (EQ-5D-5L)., measured over 1 year.

The primary endpoint is patient-reported health assessed using the EuroQol EQ-5D-5L. The registry describes evaluating changes in patient-reported pain and social interaction for quality of life from preoperative assessment through postoperative assessment, with a timeframe of 1 year. It specifies the EQ VAS, reported in units on its scale, and identifies the planned summary as a mean and standard deviation.

The instrument has two relevant components in the registry description. Its descriptive system covers mobility, self-care, usual activities, pain or discomfort, and anxiety or depression. Each dimension has five response levels, ranging from no problems to extreme problems. The record notes that health utility values generated from EQ-5D generally range from 0 (death) to 1 (perfect health), and that values less than 0 are possible for states considered worse than death. These utility values are distinct from the EQ VAS.

The EQ VAS records a patient’s self-rated health on a scale from 0 to 100. Its endpoints are described in the registry as “The best health you can imagine” and “The worst health you can imagine.” A mean can describe the average score in a group, while the standard deviation describes how dispersed individual scores are around that average. Using a patient-reported measure can capture a person’s assessment of health rather than relying only on clinical events. However, the registry record does not report the observed scores, change, or variability at the one-year timeframe.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary outcome as continuous and specifies a mean with standard deviation. The listed measure is the EQ VAS, a patient self-rating on a scale from 0 to 100. A mean is a measure of the group’s average score. A standard deviation describes the spread of individual scores around that mean; it is not the same as the uncertainty in the estimated mean. These are general statistical concepts. The registry record does not report the outcome values needed to interpret either quantity.

What would a change estimate describe?

The endpoint description focuses on changes from preoperative assessment through postoperative assessment, with a 1-year timeframe. In general, a change estimate describes how a measured outcome differs between specified assessments. To interpret it, readers need to know which observations were included, how the change was calculated, and how incomplete or repeated measurements were handled. Those analysis details and the observed estimates are not reported in the registry record. No particular change calculation should therefore be assumed.

A comparison of group means and an analysis of within-person change answer related but not identical questions. A within-person analysis uses measurements from the same participant at different times. A comparison of means at separate time points may use a different set of available observations if follow-up is incomplete. General statistical interpretation depends on the approach and the data included. The registry record does not state which approach was used.

How should uncertainty be understood?

A confidence interval is a general way to express uncertainty around an estimated quantity. It gives a range of values compatible with the data and the statistical method under its assumptions; it does not guarantee that the true value falls in that particular interval. A narrow interval indicates greater precision than a wide interval, all else being equal. No confidence interval for the primary outcome is reported in the registry record, so its precision cannot be assessed.

A p value, when reported, addresses compatibility between data and a specified null hypothesis under a statistical model. It does not measure the size or clinical importance of an effect, and it does not establish causation. No p value or hypothesis test for the primary endpoint is reported in the registry record. The registered description of a mean and standard deviation alone does not indicate that a significance test was performed.

What do the planning assumptions mean?

The registry information describes planning illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The assumed effect to detect is expressed as a fraction of the observed effect. In general, a sample-size calculation estimates the number of participants needed to meet specified design and statistical assumptions. Such calculations are planning illustrations, not evidence that a study had a particular probability of detecting an effect after it was conducted.

The illustrations described are hypothetical two-arm calculations. The registered study is observational, has no stated allocation method, and does not describe a like-for-like control comparison. The two-arm assumption therefore should not be mistaken for the study’s actual design. The registry record does not report a sample-size justification for the study itself. No numerical planning estimates are stated in the record, and none should be inferred from the assumptions alone.

How do the device and event data affect interpretation?

The study includes one or more approved or cleared products and is described as multi-device. In general, pooling results across devices can conceal variation between products or between participant groups. A device-specific interpretation requires knowing which product each participant received and how outcomes were analyzed by device. Those details are not reported in the registry record.

Adverse-event counts are descriptive. A serious-event count records the occurrence of events under the study’s reporting definitions; by itself, it does not show whether an event was caused by the device or whether its frequency differs from another treatment. A comparative safety analysis would require a suitable comparator and information about event definitions, follow-up, and analysis. The registry record does not report such a comparison.

The record lists zero analyses. It therefore does not provide an analysis result for the primary endpoint or explain which statistical methods were applied to the listed outcomes. The statistical analysis plan, model specifications, handling of multiple outcomes, and treatment of missing data are not reported in the registry record.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Foot and Ankle Devices")
n   <- c(84)
m   <- c(74.1)
sp  <- c(22.5)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Foot and Ankle Devices  84  74.100  22.500  69.217  78.983

11. Multiplicity, Missing Data and Analysis Populations

The record names a primary outcome and four secondary outcomes: the Foot and Ankle Ability Measure, Safety Assessment, Surgeon Survey, and Patient Survey. It also lists five outcome measures overall. When several outcomes or multiple analyses are considered, the chance of at least one apparently notable result can increase. General approaches to multiplicity include prespecifying a primary analysis, adjusting inference across a family of tests, or treating secondary analyses as exploratory. Which approach was planned or used is not reported in the registry record.

The registry lists zero analyses. It does not report results for the primary or secondary outcomes, nor does it identify a statistical analysis plan, a hierarchy among secondary outcomes, or any adjustment for multiple comparisons. It is therefore not possible to assess the role of multiplicity in the reported evidence.

Missing data can affect both the number of participants contributing to an outcome and the interpretation of an estimate. In general, missingness may be related to health, follow-up, or other participant characteristics; different assumptions and methods can lead to different estimates. The registry record does not report how many participants completed the EQ-5D-5L at each assessment, how missing observations were handled, or whether any sensitivity analyses were conducted.

The analysis population is also not described. The registry lists enrollment of 119, but does not report the number included in the primary analysis or how participants with incomplete follow-up were treated. No inference about completion or retention should be made from the enrollment figure alone.

12. 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 serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: infection (3.4%), pain (1.7%), acute aortic dissection (0.8%), below knee amputation (0.8%), non-union (0.8%).

For the Foot and Ankle Devices group, the registry lists 119 at risk for serious adverse events and 9 affected. For other adverse events, it lists 119 at risk and 19 affected. The record reports 0 deaths. These are descriptive counts; they do not establish that events were caused by a device, and they do not compare risks with another group.

The registry also lists serious-event terms with percentages: Infection, 3.4%; Pain, 1.7%; acute aortic dissection, 0.8%; Below Knee Amputation, 0.8%; and Non-Union, 0.8%. These are the entries recorded for the listed terms. The record does not provide enough detail to determine from these entries alone whether a term represents one or more events per participant, how overlapping events were handled, or the event-specific follow-up time.

Counts of participants affected and counts of events are not necessarily interchangeable: one participant may experience more than one event. The registry does not provide a comparative safety analysis, an attribution assessment, or further details on event definitions in the information reported. The figures should therefore be read as recorded adverse-event data rather than as estimates of treatment-caused risk or evidence of a difference between treatments.

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

The record documents a terminated post-market observational study of foot and ankle devices, with enrollment listed as 119 and a planned primary assessment of EQ-5D-5L at 1 year. It gives a description of the patient-reported measure, names secondary outcomes, and records adverse-event counts. These details describe the scope and registered aims of the study.

They do not show the primary endpoint result. The registry record does not report the EQ VAS mean, standard deviation, change from preoperative assessment, confidence interval, or statistical test. As a result, the direction, size, and precision of any change in patient-reported health cannot be assessed from the reported information. The absence of posted analyses also means that the named secondary outcomes cannot be interpreted as results.

The observational design and lack of a described comparator limit causal interpretation. A change over time, if reported, would not alone show that the device caused that change. Participants were treated with one or more included products, and the record does not report product-specific outcome estimates or analyses that account for differences among participants.

The adverse-event counts and listed terms describe events recorded in the study. They do not establish device attribution or comparative safety. The status TERMINATED is reported, but the reason is not reported in the registry record; it should not be used to infer either favorable or unfavorable outcomes.

In general, a registry entry can clarify what a study intended to assess and what information was recorded, while still leaving outcome evidence unavailable for interpretation. Here, the study description and safety counts are available, but the primary outcome analysis is not. Conclusions should remain limited to those documented features rather than extending to claims about benefit, lack of benefit, or comparative risk.

14. Why This Trial Matters Statistically

This study illustrates a useful distinction in clinical research: registering an outcome is not the same as reporting its result. The registry specifies a patient-reported primary measure, its general assessment period, and a summary based on the mean and standard deviation. Without outcome estimates, however, readers cannot assess the size or precision of the result. Statistical interpretation depends on observed data and analysis details, not only on an endpoint description.

It also highlights the limits of descriptive evidence from an observational, multi-device study. The record describes participants treated with one or more included products and does not describe a control group or allocation method. Such a design can document outcomes and adverse events among participants, but a causal comparison requires more than counts or changes over time. Clear descriptions of who was analyzed, what device was used, how follow-up was measured, and how other explanations were addressed are important to interpretation.

The planned EQ-5D-5L outcome is patient-reported, making the measurement process and completeness of follow-up especially relevant. In general, interpretation of a change in a patient-reported score depends on comparable assessments over time and on understanding which participants contributed data. The registry record does not report those details or the results needed to evaluate them.

Finally, the record demonstrates why study status and analysis status should be distinguished. The study is marked TERMINATED, while the reason for that status and the primary analysis are not reported. Neither fact by itself determines what the outcome would have been. Statistical reading requires separating documented design and event information from unreported estimates and avoiding conclusions that the available record cannot support.

15. 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.

Several limitations specific to this study constrain interpretation. It is described as observational, with no comparator group and no stated allocation method. The record therefore does not describe a design that directly compares device use with an alternative. The study is also multi-device: participants could be treated with one or more included products, but product-specific enrollment, exposure, and outcome results are not reported.

The stated primary outcome is patient-reported EQ-5D-5L at 1 year, yet no primary analysis is reported. Baseline and follow-up scores, the number assessed at each time point, and the method used to estimate change are not reported in the registry record. Without them, neither the outcome pattern nor its statistical precision can be evaluated.

The study description mentions 10 sites and a minimum of 40 patients per device, while overall enrollment is listed as 119. The record does not state site-specific or device-specific enrollment or whether the described minimum was achieved. It also does not report the reason for termination, whether follow-up was completed, or how the termination affected data collection.

Further information needed to assess the evidence includes the analysis population, missing-data methods, statistical analysis plan, outcome results, event definitions, and details of adverse-event attribution. These items are not reported in the registry record. The adverse-event counts are consequently descriptive and cannot support a controlled estimate of comparative risk.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Wright Foot & Ankle Post-Market Observational Study — NCT04118894.
• Registry record last updated 2025-01-14; status last verified 2025-01.
• Results first posted 2025-01-14.
• 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.

19. Record Summary

The Wright Foot & Ankle Post-Market Observational Study is listed as a terminated observational study sponsored by Stryker Trauma and Extremities. The registry reports a start date of 2020-01-22, a primary completion date of 2022-12-08, and enrollment of 119. The study description identifies 10 sites and a minimum of 40 patients per device.

The primary outcome is EQ-5D-5L at 1 year, with the EQ VAS described as a mean and standard deviation. The record names the Foot and Ankle Ability Measure, Safety Assessment, Surgeon Survey, and Patient Survey as secondary outcomes. No analyses are listed, and primary-outcome results are not reported in the registry record.

For the Foot and Ankle Devices group, 9 participants are listed as affected by serious adverse events and 19 by other adverse events, with 119 at risk in each category and 0 deaths. The reason for termination and further analysis details are not reported in the registry record.