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 External Fixation Versus Splinting of Acute Calcaneus Fractures (NCT04063657), a randomized na study. The primary outcome is Time to Definitive Surgery.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04063657 |
| Phase | NA |
| Condition | Calcaneus Fracture |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 1 |
| Arms in the primary outcome | 2 |
| Lead sponsor | University of California, Davis |
| Results posted | Yes |
2. Clinical Question
Population
Adults with an acute calcaneal fracture recommended for operative treatment. The registry descriptions define acute injury as fewer than 2 days from injury.
Intervention
External fixation while the participant awaited clinical suitability for definitive surgical fixation.
Comparator
A short leg splint while the participant awaited clinical suitability for definitive surgical fixation.
Primary question
How much time elapsed from injury to definitive surgery, and could the two approaches be compared on this interval? The study summary also identifies soft tissue complications, time to surgery, definitive fixation, and functional outcomes as aims.
The clinical question concerns the period before definitive surgery, rather than a comparison of definitive surgical procedures. The registry describes two approaches to temporary stabilization: an external fixator or a short leg splint. In both groups, the temporary approach was to continue until the participant was considered clinically appropriate for definitive fixation.
The stated primary outcome was time to definitive surgery, measured in days from injury, with a timeframe of within 2 weeks from injury. The study summary also lists aims concerning soft tissue complications, definitive fixation, and functional outcomes assessed with validated scoring systems. Secondary outcomes listed in the registry include union rate, radiographic measures, and functional measures. These aims describe the questions the trial set out to address; they do not establish that the trial collected enough observations to answer them.
Only 1 participant was enrolled, and the registry reports that the study stopped prematurely because of poor recruitment. The posted data therefore cannot support a meaningful comparison of the two temporary approaches. They describe the enrolled participant’s recorded time to surgery in the external-fixation arm, but there is no enrolled participant in the splinting arm.
3. Trial Design
The registry describes a randomized, parallel-group trial with no masking. The planned comparison was external fixation versus splinting before definitive surgery for acute calcaneus fractures. The listed sponsor is the University of California, Davis. The trial status is terminated; the registry gives a start date of 2019-06-14 and a primary completion date of 2019-09-03.
Enrollment was 1. The primary-outcome record explains that the study stopped prematurely because of poor recruitment and that only 1 subject was enrolled. The posted arm data show 1.0 participant in the external-fixation group and 0.0 participants in the splinting group. Thus, although randomization and a parallel comparison were specified, the enrolled data do not contain observations in both groups. No treatment contrast can be estimated from these arm counts.
The registry describes the external-fixation intervention as placement in an external fixator until the participant was considered clinically appropriate for definitive surgical fixation. The splinting intervention was placement in a short leg splint until that point. The eligibility description specifies adults with an acute calcaneal fracture recommended for operative treatment; acute injury is described as fewer than 2 days from injury.
The registry lists phase as NA. Further detail about the randomization procedure, allocation concealment, or a protocol for handling departures from assigned treatment is not reported in the registry record. The statistical analysis plan is not reported in the registry record. The outcome record includes a value for time to definitive surgery in the external-fixation group, but does not provide a two-arm estimate or a measure of variability.
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 | External Fixation | Splinting |
|---|---|---|
| STARTED | 1 | 0 |
| COMPLETED | 0 | 0 |
| NOT COMPLETED | 1 | 0 |
Reasons for not completing this period:
| Reason | External Fixation | Splinting |
|---|---|---|
| Lost to Follow-up | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: Study stopped prematurely due to poor recruitment. Only 1 subject was enrolled.
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: Study stopped prematurely, only 1 participant enrolled in the external fixation arm.
| Characteristic | Unit | External Fixation | Splinting | Total |
|---|---|---|---|---|
| Participants analysed | 1 | 0 | 1 | |
| Age, Continuous | years | 50 (50 to 50) | — | 50 (50 to 50) |
| Sex: Female, Male: Female | Participants | 0 | — | 0 |
| Sex: Female, Male: Male | Participants | 1 | — | 1 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 | — | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 1 | — | 1 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | — | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | — | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | — | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | — | 0 |
| Race (NIH/OMB): Black or African American | Participants | 1 | — | 1 |
| Race (NIH/OMB): White | Participants | 0 | — | 0 |
| Race (NIH/OMB): More than one race | Participants | 0 | — | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | — | 0 |
| Region of Enrollment: United States | participants | 1 | — | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Time to Definitive Surgery, measured over Within 2 weeks from injury.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | days |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is time to definitive surgery, defined as the duration from injury to definitive surgery and measured in days. The registry gives the outcome timeframe as within 2 weeks from injury. The posted value for the external-fixation arm is 3.0 days. There is no corresponding value for the splinting arm because that arm enrolled 0.0 participants.
In general, elapsed time is a direct way to describe how long a participant waits between an injury and a later procedure. It is relevant to the study’s stated aim of determining whether external fixation decreases time to definitive surgical stabilization compared with splinting. The endpoint is a measure of timing, however; it does not by itself describe soft tissue complications, the quality of definitive fixation, or functional outcomes.
A group comparison of this endpoint would ordinarily require outcome observations in both groups and an analysis suited to the way the data were collected. With only one observed value in one arm and none in the other, the record cannot show a comparative difference or characterize how much times might vary among participants. No confidence interval or other uncertainty estimate for a between-group effect is posted. The single value is descriptive of the enrolled participant, not an estimate of the typical time to surgery in either treatment group.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary outcome record reports 3.0 days from injury to definitive surgery for the external-fixation arm. That arm includes 1.0 participant. The splinting arm includes 0.0 participants and has no primary-outcome value. These data describe an observation in one group; they do not provide a comparison of external fixation with splinting.
The study was randomized, but random assignment alone does not create a usable treatment comparison when enrollment stops before both groups contribute observations. In this trial, there is no measured outcome in the splinting group against which to interpret the external-fixation observation. A relative effect, an absolute difference between groups, and a statistical test of the primary outcome are therefore not estimable from the posted data. The registry lists no analyses.
The 3.0-day value should also be read in light of its limited precision. It is one participant’s recorded interval, not a group average supported by multiple observations. The record does not provide a measure of spread, a confidence interval, or other uncertainty information for this endpoint. It cannot indicate the range of times that might occur among other participants or how reproducible this observation would be.
The trial summary states that recruitment was poor and the study stopped prematurely. This explains why the intended comparison is unavailable, but it does not establish what the outcome would have been with greater enrollment. Nor can the direction or size of a treatment effect be inferred from the single observed value. The posted data do not establish that either approach shortens or lengthens time to surgery.
The same caution applies to the study’s broader aims. The registry lists soft tissue complications, definitive fixation, and functional outcomes among the aims, and it lists secondary outcomes such as union rate, radiographic parameters, VAS, and FFI-R. A list of intended outcomes is not evidence of a treatment effect. The limited enrollment and absence of a splinting participant prevent a meaningful arm-to-arm assessment of these questions from the posted results.
In short, the record gives a descriptive primary-outcome observation and documents early termination after limited recruitment. It does not provide an estimate of comparative effectiveness, a measure of comparative precision, or evidence that resolves the stated clinical question. The registry does not report a sponsor analysis that could supersede a recalculation; no comparative recalculation is estimable from the available arm data.
9. Statistical Methods Explained
What does randomization mean in this record?
In general, randomization assigns participants to study groups using a chance-based process. Its purpose is to reduce systematic differences between groups at the point of assignment, supporting a fair comparison when outcomes are collected and analyzed. The registry labels this trial randomized and parallel, with external fixation and splinting as the groups. The record does not describe the randomization sequence or allocation procedures, so those details are not reported in the registry record.
A randomized design still needs participants and outcome observations in the groups to estimate a contrast. Here, the posted enrollment is 1, with 1.0 participant in the external-fixation arm and 0.0 in the splinting arm. Randomization cannot supply the missing outcome observation in the splinting arm. Consequently, the design label should not be mistaken for evidence that a randomized treatment comparison was completed.
What can the primary endpoint estimate?
The primary endpoint is a duration: time from injury to definitive surgery, measured in days. The registry posts 3.0 days for the external-fixation group. A duration can be summarized within each group and compared between groups, but the appropriate summary and analysis depend on the design and available data. In general, a treatment comparison needs observations from each treatment group. The absence of a splinting observation means no between-group effect can be estimated.
For a well-supported group summary, multiple observations are usually needed to describe both the center of the data and its variability. With one recorded duration, the value is an individual observation and does not characterize the distribution of times in the group. The registry provides no dispersion measure or confidence interval for this outcome. A confidence interval, in general, expresses uncertainty around an estimated quantity under a specified statistical model; no such interval for the treatment contrast is available in this record.
Why are no comparative analyses available?
The registry lists 0 analyses. Its endpoint information also indicates that values are missing or not estimable for a two-arm comparison. This is consistent with the posted arm enrollment: the splinting group has no participants and no outcome value. Without data from both groups, a comparative effect and its uncertainty cannot be calculated from the posted summaries. The registry’s statistical analysis plan, including any planned model or test, is not reported in the registry record.
In general, an analysis plan describes how outcomes will be summarized, how treatment groups will be compared, and how uncertainty will be quantified. It may also specify how to handle missing observations, protocol deviations, or multiple outcomes. Those details should not be inferred from the trial’s randomized design or from its stated aims. They are not reported in the registry record.
How should planning illustrations be understood?
In general, sample-size planning asks how many participants would be needed to detect a prespecified effect under stated assumptions. The planning assumptions described for this record use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. They define the effect to detect as a stated fraction of the observed effect. For time-to-event tables, the stated convention is to give total events; for other outcomes, it is participants per arm.
These are planning conventions, not evidence about the trial’s achieved ability to detect an effect. A planning illustration is not observed power, and it does not replace analysis of trial outcomes. In this trial, the posted arm data do not yield an estimable two-arm effect for the primary endpoint. The registry indicates that a two-arm comparison is not estimable; therefore, a planning illustration based on a comparative observed effect should not be treated as a usable treatment-effect estimate. Any sample-size calculations are illustrations under assumptions, not observed trial findings or a record of the original design justification. The trial’s own sample-size justification is not reported in the registry record.
In general, over-dispersion means that observed variability is greater than a statistical model assumes. If present, it can make uncertainty estimates too narrow when a model does not account for it. The registry does not report a dispersion estimate for the primary endpoint, and the single observed value cannot characterize between-participant variability. There is consequently no basis in the posted data for assessing over-dispersion or choosing an adjustment for it.
What does the lack of masking imply?
The trial is listed as having no masking. In general, masking can reduce the chance that knowledge of treatment assignment influences aspects of care, outcome assessment, or reporting, depending on the outcome and trial procedures. The registry does not describe the outcome-assessment procedures or any safeguards against such influence. For the primary endpoint, the record defines an elapsed time from injury to surgery, but does not state who determined or recorded the dates. The implications of no masking for measurement therefore cannot be assessed in detail from the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary outcome of time to definitive surgery and a set of secondary outcomes. The secondary outcomes include union rate; radiographic measures of Bohler’s angle, calcaneal height, Angle of Gissane, calcaneal width, and calcaneal length; and functional outcomes assessed with VAS and FFI-R. The record reports 10 secondary outcomes posted and 17 outcome measures overall. Multiple outcomes can create a multiplicity concern: in general, evaluating many outcomes can increase the chance of at least one apparently notable result unless the analysis plan addresses that issue.
Whether and how multiplicity was addressed is not reported in the registry record. The statistical analysis plan, including any hierarchy among secondary outcomes or adjustment procedure, is not reported in the registry record. No analyses are listed, so the posted record does not establish which outcomes were formally analyzed or how any results were interpreted across outcomes.
The registry does not report a missing-data strategy or an analysis population definition. These details matter in general because missing outcomes and decisions about which participants are included can affect estimates and their interpretation. Here, there is no splinting participant, so the lack of that arm’s outcome is not an ordinary missing measurement among enrolled participants; it reflects the absence of enrollment in that arm. The record does not provide enough information to infer how any broader missing-data or analysis-population rules would have been applied.
The endpoint record reports the primary outcome for the enrolled external-fixation participant, but comparative results for the listed secondary outcomes are not available in the registry record. Their inclusion as registered outcomes should not be read as evidence that analyses were completed.
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 |
|---|---|---|---|
| External Fixation | 0 | 1 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| External Fixation | 0 of 1 |
| Splinting | 0 of 0 |
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 |
|---|---|
| External Fixation | 0 of 1 |
| Splinting | 0 of 0 |
The adverse-event record reports 0 serious adverse events among 1 participant at risk in the external-fixation group. It also reports 0 other adverse events among 1 participant at risk in that group, and 0 deaths. In the splinting group, 0 participants were at risk; the record reports 0 affected for the event counts and 0 deaths. No leading serious-event terms are listed.
These figures are counts within the enrolled groups, not comparative evidence about safety. In particular, the splinting group had no enrolled participants, so its zero event count does not represent observation of participants receiving splinting. The external-fixation count describes only the enrolled participant and cannot characterize the frequency or range of events in a broader group.
In general, an observed count of zero does not demonstrate that an event cannot occur. With such limited exposure and no participant in one group, the posted figures provide little information about comparative event risk. The registry record does not give a comparative safety estimate or an uncertainty interval for adverse events.
12. What the Result Does, and Does Not, Mean
The posted results establish that the trial enrolled 1 participant before it was terminated for poor recruitment. They also establish that the primary endpoint record contains a time from injury to definitive surgery of 3.0 days for the external-fixation arm. The splinting arm has 0.0 participants and no corresponding endpoint value. These are descriptive details about the trial record.
They do not establish whether external fixation or splinting leads to a shorter time to definitive surgery. There is no observed splinting outcome to compare with the external-fixation value, and no comparative effect estimate or confidence interval is reported. The single duration cannot show the typical outcome, variability, or precision expected in a larger group.
The results also do not settle the study’s other stated questions about soft tissue complications, definitive fixation, union, radiographic measures, or functional outcomes. Those outcomes appear among the study aims or registered measures, but the posted record does not contain a usable comparison of the two groups. The safety counts likewise cannot establish comparative safety because one group has no enrolled participants and the other has only 1.
In general, a trial that ends early may leave its clinical question unresolved even when it has a randomized design. Its enrollment and outcome data describe what happened in the study, not what would necessarily happen if recruitment continued or in a different group of patients. The registry does not report a completed comparative analysis that changes this interpretation.
The appropriate statistical reading is therefore narrow: a single outcome observation is recorded, while the intended two-arm comparison is not estimable from the posted data. The record neither demonstrates a benefit nor demonstrates a lack of benefit for either approach. It documents the trial’s limited enrollment and the resulting limits on inference.
13. Why This Trial Matters Statistically
This trial illustrates an important distinction between a study’s design and the information its results can support. The registry describes a randomized, parallel-group comparison, but enrollment stopped after 1 participant. Because the splinting arm has 0.0 participants, the intended treatment contrast cannot be estimated. A randomized label does not by itself ensure that a useful comparison is available.
The record also shows why endpoint observations and treatment effects are not interchangeable. The 3.0-day primary-outcome value is an observation in the external-fixation arm. A treatment effect would require a comparison with an appropriate estimate from the splinting arm. Without that observation, the value cannot answer whether the approaches differ or quantify how precisely they might differ.
Early termination for poor recruitment is statistically consequential: it leaves the trial’s central questions unresolved and limits what can be learned from both primary and secondary outcomes. The adverse-event counts are also a reminder that zero observed events in a group with very little or no exposure do not provide a precise assessment of comparative safety.
Finally, the record distinguishes planning assumptions from trial evidence. Sample-size planning illustrations are conditional on assumptions and an effect to detect; they are not observed power or proof that the intended comparison was adequately studied. Since a comparative effect is not estimable from these arm data, planning calculations should not be mistaken for results. The trial matters statistically because it makes clear how recruitment, group representation, and available outcome data determine whether a planned clinical question can be answered.
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 is the enrollment of only 1 participant, followed by premature termination because of poor recruitment. The posted arm counts show that the external-fixation group contains 1.0 participant and the splinting group contains 0.0 participants. The missing splinting group is not a small sample with an imprecise estimate; it leaves no outcome estimate for that group at all.
The primary endpoint consequently has only one posted value, 3.0 days in the external-fixation arm. No measure of variability or uncertainty is reported, and the registry lists no analyses. A comparative estimate and its precision cannot be recovered from the available arm summaries. This limits interpretation of the primary outcome independently of the randomized design.
The posted record does not establish whether the listed secondary outcomes were collected or analyzed. It reports 10 secondary outcomes posted and 17 outcome measures overall, but no analysis records. The statistical analysis plan, missing-data methods, analysis populations, multiplicity approach, and sample-size justification are not reported in the registry record. These gaps prevent assessment of planned analytic choices.
The study is listed as unmasked, while further detail on outcome assessment and procedures to limit measurement or reporting bias is not reported in the registry record. The adverse-event counts come from the same very limited enrollment and do not support a reliable comparison between groups. Together, these limitations mean that the record is primarily informative about trial conduct and the presence of one recorded outcome, rather than about differences between the two approaches.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: External Fixation Versus Splinting of Acute Calcaneus Fractures — NCT04063657.
- Registry record last updated 2022-02-09; status last verified 2022-01.
- Results first posted 2022-02-09.
- 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
The registry record for NCT04063657, titled “External Fixation Versus Splinting of Acute Calcaneus Fractures,” describes a randomized, unmasked, parallel-group trial sponsored by the University of California, Davis. The listed interventions were external fixation and splinting before definitive surgery. The trial began on 2019-06-14, had a primary completion date of 2019-09-03, and is listed as terminated.
Enrollment was 1. The registry attributes early termination to poor recruitment. The primary outcome was time from injury to definitive surgery, measured in days, with a timeframe of within 2 weeks from injury. The external-fixation arm has a posted value of 3.0 days; the splinting arm has no enrolled participants. No analyses are listed, and a two-arm comparison is not estimable from the posted data.