Ascension® Post- Approval Study; PyroCarbon Metacarpophalangeal Total Joint Prosthesis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Ascension® Post- Approval Study; PyroCarbon Metacarpophalangeal Total Joint Prosthesis (NCT02408471), a na na study. The primary outcome is Number of Participants With Revisions.

2. Clinical Question

3. Trial Design

This is a non-randomized, consecutive-enrollment, one-year post-approval study. The registry lists a single group treated with the Ascension® PyroCarbon MCP implant and classifies the model as single group. Allocation is listed as NA and masking as none. These features describe an observational follow-up of treated participants rather than a randomized, masked comparison.

The registry records enrollment of 97 participants. That is the listed enrollment figure; the record does not establish how many participants contributed data to each outcome or completed follow-up. The study began in 2002-06, had primary completion in 2015-01, and is listed as terminated. The reason for termination is not reported in the registry record. Phase is listed as NA, and Smith & Nephew, Inc. is identified as the sponsor.

The primary outcome timeframe is 12 months. The brief summary describes the study as one-year follow-up, while the registry also lists secondary measures concerning joint motion, deviation, pinch, grip, function, pain, cosmetic appearance, and joint position. These are outcome domains in the record, not evidence that results for each are available.

Because there is no comparator group, changes over follow-up cannot by themselves distinguish device-related change from other influences, such as the underlying condition or changes in care. No randomized treatment contrast is available. The registry record contains no analysis entries, so it does not specify which participants were included in particular analyses or how outcome data were handled.

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: One bilateral participant completed the study in 2010 for the left hand and the same participant enrolled in the study again in 2011 for the right hand. Each enrollment is accounted for separately as appropriate for the total number of participants enrolled.

Overall Study

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.

Population: One bilateral participant enrolled in the study twice. The second enrollment was the contralateral hand after this participant completed the study.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Revisions, measured over 12 months.

The primary endpoint is the number of participants with revision surgery during the 12-month timeframe. The registry defines it as a count of participants with a revision surgery. It therefore concerns whether a participant underwent revision, rather than the number of revision procedures or the timing of each procedure. The registry does not provide further operational detail about what qualified as revision surgery or how events were ascertained.

A revision endpoint is clinically interpretable as a recorded subsequent operation involving the implant or joint, but the precise meaning depends on the study’s definition and event collection procedures. Those details are not reported in the registry record. The endpoint is expressed as a participant count, which can describe the observed experience in the study group if a result is reported. By itself, it does not establish how that experience compares with another treatment or with the course expected without the implant.

The result for this endpoint is not reported in the registry record. The enrollment figure is not a substitute for the number with revision surgery, and it does not establish how many participants had complete 12-month outcome information. Without the endpoint count and its analysis population, the size and precision of the observed revision outcome cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation begins with identifying the estimand: the outcome, participants, timeframe, and comparison that an analysis is intended to describe. In this study, the primary outcome is a participant count for revision surgery at 12 months. The study has one treated group and no comparator, so its natural descriptive target is the observed revision experience among participants with available outcome information. The registry does not report an analysis population or the endpoint count, leaving the actual estimate unavailable.

What does a participant count represent?

A count records how many participants meet the endpoint definition. It is not automatically a rate or a risk. To interpret a proportion, the numerator must be paired with an appropriate denominator, such as the number of participants whose endpoint status was assessed over the relevant timeframe. The enrollment entry of 97 does not establish that all enrolled participants had complete 12-month follow-up. The registry does not report a primary-outcome denominator or state how missing assessments were handled.

Counts also depend on outcome definitions and ascertainment. The record describes the endpoint as participants with revision surgery, but does not give criteria for classifying a procedure as a revision, describe adjudication, or explain how surgeries were captured. Those omissions do not show that the procedures were classified incorrectly; they mean the registry record alone does not document the operational details needed to evaluate classification.

What can a single-group design estimate?

A single-group follow-up can describe outcomes observed among the treated participants. It cannot, on its own, estimate what would have happened to the same participants under another treatment. This missing counterfactual is central to causal interpretation. Even if outcomes change during follow-up, a change may reflect the intervention, underlying disease, other care, or other influences. Randomization and a suitable comparator can help address some sources of confounding; neither is part of the posted design.

Consecutive enrollment describes how participants entered the study according to the brief summary, but it does not make treatment assignment random. The record does not describe a sampling frame, recruitment refusals, or participant characteristics that would allow assessment of how representative the enrolled group was. Generalization beyond the observed study group therefore requires caution.

How should uncertainty be assessed?

For an estimated proportion or count, uncertainty depends on the outcome data and the number of participants with usable observations. A confidence interval is a range of values compatible with the estimate under a specified statistical procedure; it communicates precision, not certainty that the true value lies within the interval. No confidence interval or other uncertainty measure for the primary endpoint is reported in the registry record. Because the endpoint result itself is also absent, its precision cannot be evaluated.

Statistical significance and clinical importance are different concepts. A statistical test addresses compatibility between data and a specified model or null hypothesis; it does not by itself establish that an outcome difference matters clinically. In this single-group record, no primary test or comparative estimate is reported. No p-value should be inferred from the endpoint description or from the safety counts.

What do the planning illustrations mean?

The sample-size assumptions describe planning illustrations computed from an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The stated effect to detect is a fraction of the observed effect. These are planning assumptions, not a description of the study’s original design. The record identifies this study as single group, so a hypothetical two-arm calculation does not create a comparison group or show that such a comparison was conducted.

Sample-size planning illustrates how the number of participants per arm may depend on an assumed effect, statistical significance level, allocation, and model. Such planning values are not observed outcomes, and they are not observed power. They also do not demonstrate that the study was adequately powered for its actual design. The registry does not report a sample-size justification for the post-approval study, and the primary endpoint result needed to understand the stated observed-effect basis is not reported in the registry record.

What role does over-dispersion play?

In general, over-dispersion occurs when observed variation in count data exceeds what a model assumes. If a count analysis assumes less variability than the data have, uncertainty can be understated and statistical evidence can appear stronger than warranted. Assessing over-dispersion requires outcome data and a specified model. The registry does not report an analysis model or count-data results for the primary endpoint, so over-dispersion cannot be evaluated for this study from the record.

These general concepts explain what would be needed for a fuller analysis; they do not fill in missing results. The record does not report the primary endpoint estimate, its uncertainty, analysis details, or the handling of missing observations. Statistical conclusions should therefore remain limited to the design and descriptive entries that are actually recorded.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Ascension® MCP Finger Implant")
n      <- c(97)
events <- c(6)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Ascension® MCP Finger Implant  97  6  6.2  2.3  13.0  2.9  12.8  2.9  12.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 11 outcome measures, including the primary revision endpoint and secondary measures of joint range of motion, radial-ulnar deviation, tip pinch, grip strength, function, pain, cosmetic appearance, and joint position. When multiple outcomes are examined, the chance of at least one apparently unusual statistical finding can increase if each is tested separately. Statistical approaches to multiplicity can address that issue, but the appropriate approach depends on the questions and analysis plan.

Multiplicity procedures, a prespecified testing hierarchy, and an analysis plan are not reported in the registry record. The record also contains no analysis entries. It is therefore not possible to determine which outcomes were analyzed, whether any adjustment was used, or how primary and secondary findings were prioritized. The absence of this information does not establish that no plan existed; it means the registry record does not document one.

Missing-data handling and analysis populations are likewise not reported. The record does not state how many participants had endpoint information, whether participants with incomplete follow-up were included in any analysis, or whether missing observations were imputed or otherwise addressed. These details matter because incomplete follow-up can affect both the estimate and its precision, especially if outcome availability is related to participants’ health or outcomes.

The enrollment figure cannot resolve these issues. It does not identify the denominator used for an outcome analysis or establish complete follow-up. The primary endpoint result, its analysis population, missing-data approach, and multiplicity strategy are not reported in the registry record, limiting reproducibility and interpretation of any potential outcome findings.

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: recurrent ulnar deviation (3.1%), stiffness (3.1%), tendon adhesion (3.1%), dislocation (2.1%), flexion contracture (2.1%).

The safety record lists one group, the Ascension® MCP Finger Implant group. It reports 97 participants at risk for serious adverse events and 25 affected. For other adverse events, it reports 97 at risk and 30 affected. Deaths are listed as 0. These are registry counts; the record does not provide further detail about event-specific observation time or the method of collection.

The listed serious adverse-event terms are recurrent ulnar deviation at 3.1%, stiffness at 3.1%, tendon adhesion at 3.1%, dislocation at 2.1%, flexion contracture at 2.1%, and subluxation at 2.1%. The registry does not specify the denominator or further counting rules for these term percentages. They should not be interpreted as rates calculated over a known follow-up period from the information in the record.

Participants can potentially have more than one event or event term, and the record does not report whether the serious and other adverse-event counts overlap. These figures are descriptive for the single group. With no comparator group, they do not establish whether event occurrence is more or less frequent than under another treatment.

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

The record establishes that a post-approval, non-randomized, single-group study of the Ascension® MCP Finger Implant was registered, with consecutive enrollment described in its brief summary. It identifies revision surgery by 12 months as the primary endpoint and lists other joint and function-related outcomes. The safety entries provide group-level counts and a list of serious adverse-event terms.

The record does not report the primary endpoint result. It therefore cannot establish how many participants had revision surgery at 12 months, nor how precise an estimate of that outcome would be. The enrollment entry is not an outcome result and should not be treated as one. The record also does not provide endpoint-specific denominators, follow-up completeness, confidence intervals, or analysis results for the listed secondary measures.

Even if a descriptive result were available, the single-group design would not directly answer how outcomes compare with another treatment or with no implant. There is no randomized comparator, and allocation is listed as NA. Changes observed during follow-up could have multiple explanations, so attributing them to the implant would require evidence beyond an unadjusted description of one treated group.

The safety counts likewise describe what the registry records for the study group; they are not comparative estimates. The record does not document event overlap, detailed ascertainment, or event-specific follow-up. The status is listed as terminated, but the reason is not reported in the registry record. Taken together, the posted information describes the study structure and selected safety counts, while leaving the primary efficacy outcome and important analysis details unreported.

14. Why This Trial Matters Statistically

Post-approval studies can add information about outcomes collected after a device has entered clinical use. This record is statistically useful to examine because it makes the distinction between study registration, study design, and reported results especially important. The presence of a named primary endpoint and an enrollment figure does not mean the endpoint estimate is available or that the full enrolled group contributed to its assessment.

The single-group design also illustrates why descriptive outcomes and causal comparisons answer different questions. A count among treated participants can describe recorded experience, but without a comparator it cannot isolate the effect of the implant from other influences. That limitation is not repaired by planning calculations that assume two arms; hypothetical planning assumptions do not change the actual design.

The registry’s safety counts offer some descriptive information, while the lack of event-collection detail, denominator definitions for listed terms, and overlap information constrains interpretation. The absence of analysis entries and the unreported handling of missing data and multiplicity further limit reproducibility. These are not merely technical details: they help readers understand which participants and outcomes support an estimate and how much uncertainty surrounds it.

Statistically, the record is a reminder to separate what is registered from what is measured, analyzed, and reported. It identifies the endpoint and study structure, but the primary result is not reported in the registry record. That boundary should guide conclusions rather than be filled by assumptions about the protocol or the observed outcome.

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 are specific to the information recorded for this study. The primary endpoint is defined as a participant count with revision surgery at 12 months, but the result is not reported in the registry record. The record also does not give a denominator for the endpoint, follow-up completion, or the criteria used to classify revision surgery. As a result, neither the observed outcome nor its precision can be assessed from the posted endpoint information.

The study has one treated group, no randomized allocation, and no comparator. It can therefore support descriptive interpretation of the group only when results are reported; it cannot directly estimate a treatment contrast. The registry does not provide sufficient detail about participant characteristics, eligibility, or recruitment to assess how well the enrolled group represents other populations with the listed conditions.

The registry lists 11 outcome measures but contains no analysis entries. It does not report which outcomes were analyzed, how missing observations were handled, whether outcome assessments were blinded, or whether multiplicity was addressed. Masking is listed as none, but the record does not describe outcome ascertainment procedures. The reason for the terminated status is not reported in the registry record.

Safety interpretation is also limited by the lack of information on event timing, collection procedures, overlap between categories, and the denominator used for the listed adverse-event term percentages. The reported counts are not comparative. These limitations describe gaps in the registry record and do not establish that the study procedures themselves were inadequate.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Ascension® Post- Approval Study; PyroCarbon Metacarpophalangeal Total Joint Prosthesis — NCT02408471.
• Registry record last updated 2023-10-10; status last verified 2017-08.
• Results first posted 2023-10-10.
• 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

NCT02408471 is a post-approval study of the Ascension® PyroCarbon MCP Finger Implant sponsored by Smith & Nephew, Inc. The registry describes non-randomized, consecutive enrollment, a single treated group, no masking, enrollment of 97, and a 12-month primary endpoint timeframe. The study began in 2002-06, had primary completion in 2015-01, and is listed as terminated.

The primary outcome is the number of participants with revision surgery. Its result is not reported in the registry record. The record lists 11 outcome measures and no analysis entries. It also records serious adverse events for 25 of 97 at risk, other adverse events for 30 of 97 at risk, and 0 deaths. These safety entries are descriptive and have no comparator. Missing endpoint results and analysis details limit interpretation.