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 An Investigation on Function and Performance of a New Microprocessor Controlled Prosthetic Knee (NCT05523349), a na na study. The primary outcome is Satisfaction During Stair Descent.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05523349 |
| Phase | NA |
| Condition | Prosthesis User, Amputation |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 14 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Össur Iceland ehf |
| Results posted | Yes |
2. Clinical Question
Population
People described in the registry as prosthesis users with amputation. The listed enrollment is 14. The registry does not give further eligibility details or describe the participants’ characteristics.
Intervention
NAVii, a new passive microprocessor-controlled prosthetic knee. The arm description says users were fitted with it for 3 weeks before comparison with their usual device.
Comparator
Each participant’s usual or prescribed microprocessor-controlled prosthetic knee, as described in the registry. This is not a separately randomized control arm.
Primary question
How does satisfaction with walking downstairs, measured using a Prosthesis Evaluation Questionnaire question, compare between the NAVii-use visit and the visit using the participant’s prescribed device? The primary measure is a score on a scale from 1 to 10, with higher scores representing greater satisfaction.
The registry describes the primary comparison as the difference between visit scores, calculated as Visit 3 minus Visit 2. Visit 2 represents participants using the investigational device, and Visit 3 represents participants using their prescribed device. Under this stated direction, a negative difference means the Visit 2 score was higher, which the registry says would support the corresponding hypotheses. The registry does not report the numerical median difference or interval estimate, so the size and precision of the observed comparison cannot be assessed from the reported primary outcome information.
3. Trial Design
This completed investigation is registered as a single-group study of a device. The intervention is NAVii, a new passive microprocessor-controlled prosthetic knee. The registry lists enrollment of 14 and identifies prosthesis use and amputation as the relevant conditions. Allocation is recorded as NA, and masking is recorded as none. The record does not describe a randomized allocation or a separately assigned control group.
The comparison is between device-use conditions: the investigational knee and the participant’s usual or prescribed microprocessor-controlled knee. The arm description says users were fitted with NAVii for 3 weeks to compare it with their usual device. For the primary outcome, the registry identifies data from Visit 2, 3 weeks after Visit 1, and Visit 3, 3 weeks after Visit 2. It describes Visit 2 as use of the investigational device and Visit 3 as use of the prescribed device. These observations are therefore framed as a within-participant comparison, rather than as a comparison between independent groups.
The registry lists the study start as 2022-08-15, primary completion as 2022-09-30, and overall status as completed. It does not report the order-selection method, whether the sequence was fixed for all participants, whether there was a washout period, or how device fitting and adaptation were handled. Those details matter when interpreting sequential observations, because changes between visits could reflect more than the device condition alone. The record also does not give a separate account of participant flow or state how many participants contributed data to each endpoint.
The stated secondary outcome is the Six Minute Walk Test. The registry lists two outcome measures, but gives no numerical results for the primary comparison in the record summarized for this analysis. There are no listed analyses. The description of the primary measure nevertheless says that a Bayesian approach was used to estimate the posterior distribution of the effect.
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 | All Participants |
|---|---|
| STARTED | 14 |
| COMPLETED | 14 |
| NOT COMPLETED | 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 | All Participants |
|---|---|---|
| Participants analysed | 14 | |
| Age, Continuous | years | 46.4 (SD 16.8) |
| Sex: Female, Male: Female | Participants | 3 |
| Sex: Female, Male: Male | Participants | 11 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: United States | Participants | 12 |
| Region of Enrollment: Iceland | Participants | 2 |
| PLUS-M T-Score | T-score | 55.3 (SD 4.9) |
| Socket Comfort Score | scores on a scale | 9.1 (SD 0.9) |
6. Primary Endpoint
The registry lists the primary outcome as Satisfaction During Stair Descent, measured over for analysis data from visit 2 (3 weeks after visit 1) and visit 3 (3 weeks after visit 2) were used.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | 89% Confidence Interval |
| Unit | score on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is satisfaction during stair descent, assessed with a question from the Prosthesis Evaluation Questionnaire about satisfaction with walking downstairs. The score is on a scale from 1 to 10: 1 represents very low satisfaction and 10 represents high satisfaction. It is a patient-reported measure of perceived function in a specific activity, rather than a direct measurement of walking speed or physical capacity.
The registry compares the score at Visit 2, when participants were using the investigational device, with the score at Visit 3, when they were using their prescribed device. The stated parameter is the difference calculated as Visit 3 minus Visit 2. Consequently, a negative value indicates that the Visit 2 score was higher, consistent with the direction the registry says would support the corresponding hypotheses. That sign convention is important: the difference is not defined as investigational-device score minus prescribed-device score.
A satisfaction question is relevant because the investigation concerns functional performance as experienced by prosthesis users, and stair descent is the activity named in the endpoint. However, one scale score captures only one aspect of experience. It does not by itself establish performance across other activities or explain why a participant gave a particular rating. The registry does not report the numerical endpoint estimate, its 89% interval, or the underlying visit-level scores, so the magnitude and precision of the comparison are not available in the recorded result information.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary outcome description specifies a Bayesian comparison of satisfaction scores at Visit 2 and Visit 3, with the estimated difference defined as Visit 3 minus Visit 2. Since the score is higher for greater satisfaction, a negative difference would mean a higher score at Visit 2, when participants were using the investigational device. The registry explicitly identifies that direction as one that would support the corresponding hypotheses. This is a statement about the direction of the contrast, not evidence that the contrast was observed.
The record does not report a median difference, an 89% interval, or numerical visit scores. It is therefore not possible to say whether the posted data favored either device condition, how large any difference was, or how precisely it was estimated. The registry’s endpoint description says those quantities are reported in the outcome measure data table, but numerical primary outcome results are not present in the record used for this analysis. Without them, neither the direction nor the uncertainty of the observed comparison can be evaluated.
The within-participant framing has a useful statistical feature: each person’s observations can be compared across device conditions, making the contrast responsive to change within the same user. But observations collected at different visits can also be affected by time, order, adaptation, or other changes. The registry does not report whether the order was varied, whether there was a washout, or how such effects were addressed. The single-group design also does not provide a concurrent randomized control group to separate device-related changes from other influences.
The registry gives an enrollment of 14 and indicates 14 participants at risk in the adverse-event record. Those details do not establish how many contributed complete primary-outcome observations. The participant count used for the primary analysis and handling of missing scores are not reported in the registry record. Thus, even if a point estimate were available, interpretation would require knowing the analysis population and the amount of missing data.
The described 89% interval is an uncertainty measure associated with the Bayesian analysis, but the record does not give its endpoints or enough methodological detail to assess how it was constructed. An interval describes uncertainty in an estimate under the specified analysis; it is not a measure of the range of individual responses. Since the estimate itself is absent, no conclusion about the degree of uncertainty is possible. The registry also gives no analysis results for the stated Six Minute Walk Test in the information.
These observations should be read as a registered, single-group device investigation with a planned comparison between two use conditions, not as evidence from a randomized parallel-group trial. The available details identify the question and the direction of the contrast, but do not establish the result. No claim about benefit or lack of benefit can be drawn from a missing numerical estimate.
9. Statistical Methods Explained
What is the contrast?
The registry defines the primary parameter as the difference between Visit 3 and Visit 2 scores. Visit 2 is described as the investigational-device condition; Visit 3 is described as the prescribed-device condition. Writing the contrast in that order determines how to read its sign. A negative difference means the Visit 2 score is higher, while a positive difference means the Visit 3 score is higher. This interpretation follows from the registry’s stated subtraction order and the scale’s direction, where higher values represent greater satisfaction.
The outcome parameter is the median difference, and the registry says the analysis used a Bayesian approach to present the posterior distribution of effects between visits. A median is a measure of central location: it identifies the middle of a distribution under the analysis, rather than describing every participant’s response. The record does not include the reported median value, so the central estimate cannot be interpreted numerically.
What does the interval communicate?
The endpoint description calls the uncertainty measure an 89% Confidence Interval and says it is a range for the difference. In general, an interval conveys uncertainty around an estimate: a narrower interval indicates greater precision under the assumptions and method used, while a wider interval indicates less precision. Because the analysis is described as Bayesian, an interval based on the posterior distribution is often interpreted as a range containing a stated proportion of that distribution. The registry does not explain the interval construction or provide its endpoints, so its width and relationship to any decision threshold cannot be evaluated. The label used in the registry is retained rather than assuming a particular calculation.
An interval is not the range of individual scores, nor does it show how much participants varied from one another. It also does not by itself determine whether a difference is important in practice. Such judgments require the estimate, its uncertainty, and relevant context; those numerical outcome details are not reported in the registry record.
What does a Bayesian analysis add?
In general, Bayesian analysis represents uncertainty about a parameter using a probability distribution informed by the data and a prior distribution. A posterior distribution describes uncertainty about the parameter after combining those elements. Its interpretation depends on the model, prior choices, and data. The registry says a Bayesian approach was used, but does not report the prior, model specification, computational procedure, or diagnostic checks. As a result, readers cannot independently assess how these choices shaped the reported posterior distribution.
The posterior distribution is about the estimated contrast, not a probability that an individual participant will have a particular score. If its median and interval were available, they would describe the estimated difference and uncertainty under the specified Bayesian analysis. Since neither the estimate nor interval endpoints are included in the result information, no such interpretation can be made for this investigation’s observed primary outcome.
How does the single-group structure matter?
In general, comparing repeated observations from the same participant can account for stable differences between people when estimating a within-person contrast. This can be useful when each person experiences both conditions. It does not automatically control for changes over time, order effects, learning, adaptation, or other factors that differ between visits. Those concerns are especially relevant when measurements are taken sequentially. The registry identifies the visit conditions and timing, but does not report randomization of sequence, a washout period, or an adjustment for visit effects. The record therefore does not establish how these potential influences were handled.
The study is listed as single group, with allocation recorded as NA and no masking. The comparison is not a randomized comparison between separate intervention and control groups. Any contrast should therefore be understood in the setting of the study’s sequential device-use observations, rather than as a direct estimate from a parallel randomized trial.
What can planning calculations tell readers?
In general, a sample-size calculation is a planning exercise that depends on assumptions about the effect to detect, variability, design, and statistical method. The stated planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect framed as a fraction of an observed effect. These are planning illustrations, not the trial’s reported design or an observed-power calculation. Equal allocation between two arms does not describe this single-group investigation’s comparison structure. The record does not give numerical planning estimates or an observed effect value that would allow those illustrations to be assessed.
Planning estimates cannot replace the observed endpoint estimate or its uncertainty. In particular, they do not show whether the study’s actual data support a particular conclusion. The registry does not report a sample-size justification for the original study, so the basis for its enrollment cannot be inferred from the planning assumptions.
What remains unavailable?
The registry record does not report the numerical primary outcome results, analysis population, missing-score handling, model details, prior distribution, or whether any adjustments were made. It lists no analyses. The description of a Bayesian method supplies a broad framework, but not enough information to reproduce or fully evaluate the analysis. These omissions limit both interpretation and independent verification of the reported endpoint.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary outcome of satisfaction during stair descent and a secondary outcome of the Six Minute Walk Test. It also lists two outcome measures, but no analyses. The record does not report a multiplicity strategy, such as whether the primary endpoint alone was treated as confirmatory, whether secondary outcomes were exploratory, or whether any adjustment was planned for considering multiple outcomes. Without that information, the implications of examining more than one outcome cannot be assessed. No claim about a multiplicity-adjusted result is supported by the record.
Missing-data handling is also not reported in the registry record. The endpoint description identifies observations at Visit 2 and Visit 3, but does not state how incomplete visit scores were treated, whether participants with only one score contributed to any analysis, or whether the analysis required paired scores. The listed enrollment and adverse-event counts do not establish the number contributing to the primary endpoint. No imputation method, sensitivity analysis, or assumptions about missingness are described.
The analysis population is not specified. The record does not say whether the primary analysis included all enrolled participants, only those who used both devices, or another defined group. It also does not provide participant-flow details for endpoint completion. These are important distinctions: an analysis based on a subset with complete observations may not represent everyone enrolled if completion is related to the outcome or device experience. The available registry information does not allow that possibility to be evaluated.
The description of a Bayesian approach does not resolve these gaps. A Bayesian model still requires decisions about the observations included, missing values, model structure, and prior assumptions. The registry does not report those details or a strategy for multiple outcomes. Accordingly, interpretation is limited to the stated endpoint definition and direction of contrast, without a basis for assessing missing-data or multiplicity effects.
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 |
|---|---|---|---|
| All Participants | 0 | 14 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| All Participants | 0 of 14 |
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 |
|---|---|
| All Participants | 1 of 14 |
Most frequent non-serious adverse event terms
| Event term | Organ system | All Participants |
|---|---|---|
| Fall | Social circumstances | 1 of 14 |
The adverse-event record lists 14 participants at risk for serious events and 0 with a serious adverse event. It lists 14 at risk for other events and 1 with an other event. The record also lists 0 deaths and no top serious-event terms. These are the counts reported for the categories in the registry; they are not estimates of comparative risk because the study does not have a separately randomized control arm.
The registry does not give a description of the other event, its timing, severity, outcome, or relationship to the device. Nor does the listed count establish whether an event was caused by the investigational device. A count of zero serious events in this study means none are recorded in this adverse-event entry; it does not establish that serious events are impossible or that risk is absent. The record also does not provide further detail about how events were collected or classified.
Safety counts should be interpreted alongside the study design and the scope of reporting. A single-group investigation with the listed enrollment can describe events recorded during the study, but it does not provide a randomized comparative estimate of adverse-event rates. The registry’s entries are limited to the event categories and counts shown; they do not resolve broader questions about safety.
12. What the Result Does, and Does Not, Mean
The record establishes that a completed single-group device investigation compared satisfaction during stair descent across use of NAVii and the participant’s prescribed prosthetic knee. It specifies the scale, visit conditions, subtraction order, and Bayesian approach. It also states how to interpret the sign: a negative Visit 3 minus Visit 2 difference corresponds to a higher Visit 2 satisfaction score. These details define the clinical and statistical question.
The record does not include the primary outcome’s numerical median difference or 89% interval. It therefore does not show whether satisfaction scores were higher in either condition, the size of any difference, or the precision of an estimate. The absence of a numerical result is not evidence of no difference. It also does not support a claim that the investigational device performed better or worse.
The study’s structure matters. It is not a randomized comparison between two parallel groups; the described comparison uses successive visits and device conditions. This allows a within-participant question to be posed, but the record does not state whether order, adaptation, or time effects were addressed. The registry also does not report the analysis population or missing-data procedures, limiting assessment of who contributed to the endpoint estimate.
The adverse-event record contains counts for serious events, other events, and deaths, but provides little detail about the other event and no comparative safety estimate. The listed secondary outcome is the Six Minute Walk Test, but its numerical result is not reported in the record summarized for this analysis. Overall, the registry entries the study question and some design features, while leaving the primary efficacy-related estimate and important analytical details unavailable. Interpretations should remain limited to that distinction.
13. Why This Trial Matters Statistically
This investigation illustrates why a trial’s design and the direction of its contrast matter as much as the name of an endpoint. The registry defines the primary difference as Visit 3 minus Visit 2, even though Visit 2 is the investigational-device condition. Reading the sign correctly depends on noticing that subtraction order and the scale’s direction: higher scores represent greater satisfaction. Without those definitions, a negative estimate could easily be misread.
The study also raises a central issue in repeated-measures analyses. Observing the same user under both device conditions can make the comparison more directly focused on within-person change than a comparison between unrelated groups. But the sequence of visits creates possible influences from time, order, and adaptation. The registry does not say whether these were controlled or modeled. Statistical interpretation must therefore reflect both the value and the limitations of the within-person framing.
A further lesson is that describing an analysis method is not the same as reporting a result. The registry names a Bayesian approach and an 89% interval, but the estimate and interval endpoints are not reported in the outcome information. Without those values, readers cannot evaluate direction, magnitude, or precision. Naming a method cannot substitute for the numerical evidence needed to interpret it.
Finally, enrollment, endpoint completion, and safety counts answer different questions. Enrollment is listed as 14, while the record does not state how many contributed paired primary-outcome observations. Safety entries provide event counts, not a randomized comparison of risk. Keeping those quantities distinct prevents conclusions from exceeding what the design and recorded results can support.
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 interpretation is the absence of numerical primary outcome results in the registry record. Although the endpoint description specifies a median difference and an 89% interval, neither the estimate nor interval endpoints are reported in the result information available for this analysis. The direction and precision of the observed comparison therefore cannot be evaluated.
The study is single group, with allocation recorded as NA and no masking. The primary comparison uses sequential visits under two device conditions rather than a separately randomized control group. The record does not describe how the order was determined, whether there was a washout, or whether time and adaptation effects were considered. These missing design details restrict interpretation of any between-visit contrast.
The registry lists enrollment of 14, but does not report the number of participants with complete primary-outcome data or identify the analysis population. Missing-data handling and participant flow are not described. The record also does not specify the Bayesian model, prior distribution, computational methods, or diagnostic checks. It gives no multiplicity strategy despite listing a secondary outcome, and the numerical results for that outcome are not reported in the information.
The safety record reports event counts but does not describe the other event or establish its relation to the device. The absence of serious events in the registry entry should not be interpreted as proof that serious risk is absent. More generally, the available information supports description of the study question and recorded safety counts, but not a complete assessment of endpoint results, analysis robustness, or comparative safety.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: An Investigation on Function and Performance of a New Microprocessor Controlled Prosthetic Knee — NCT05523349.
- Registry record last updated 2026-02-02; status last verified 2026-01.
- Results first posted 2026-02-02.
- 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
NCT05523349 is a completed, single-group device investigation sponsored by Össur Iceland ehf. It lists enrollment of 14 and evaluates NAVii, a new passive microprocessor-controlled prosthetic knee, against participants’ usual or prescribed device. The primary outcome is satisfaction during stair descent, measured with a Prosthesis Evaluation Questionnaire score on a scale from 1 to 10. The registry describes a Bayesian analysis of the Visit 3 minus Visit 2 difference and an 89% interval, but the numerical primary outcome estimate and interval are not reported in the outcome information.
The study lists the Six Minute Walk Test as a secondary outcome. The adverse-event record reports 0 serious events, 1 other event, and 0 deaths. Details about the other event, endpoint completion, missing-data handling, and the statistical model are not reported in the registry record.