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 Comparison of Subcutaneous INFIX and EXFIX for Anterior Pelvic Ring Fractures Requiring Stabilization (NCT02403154), a randomized na study. The primary outcome is Functional Outcomes (PROMIS v1.2-Physical Function Instrument).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02403154 |
| Phase | NA |
| Condition | Anterior Pelvic Ring Fractures |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 4 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Indiana University |
| Results posted | Yes |
2. Clinical Question
Population
People with anterior pelvic ring fractures requiring stabilization were the intended study population. The registry lists the condition as anterior pelvic ring fractures. The reported enrollment was 4. The record also describes observational arms for people who consented but declined randomization, and for people whose fractures did not require anterior fixation according to the treating surgeon. The latter group is described in the study summary, while the listed observational arms concern internal and external fixation.
Intervention
The intervention under study was subcutaneous internal fixation, called INFIX in the study description and represented by an internal fixator arm. Participants randomized to this arm agreed to random assignment, and the randomization system assigned the internal fixation procedure. The observational internal-fixator arm instead included people who did not want randomization and whose procedure was selected by the treating physician or patient.
Comparator
The comparator was external fixation, called EXFIX in the study description. Randomized participants assigned to this arm were to receive the external fixator procedure. A separate observational external-fixator arm included people who declined randomization and received external fixation based on physician preference or patient choice. These observational groups do not have the same assignment process as the randomized groups.
Primary question
The primary objective was to compare functional outcomes between subcutaneous internal fixation and external fixation using the PROMIS v1.2-Physical Function instrument. The registered timeframe was 24 hrs - 24 months. The registry states that no data were analyzed for the study, so it does not report an estimate of the difference between the randomized treatment groups.
3. Trial Design
The study was registered as a prospective randomized comparison of subcutaneous internal fixation and external fixation for anterior pelvic ring fractures requiring stabilization. Its allocation was randomized, its model was parallel, and its masking was recorded as single. The registry does not identify who was masked, describe the masking procedure, or provide the details of sequence generation or allocation concealment; those details are not reported in the registry record.
The randomized arms were intended to compare internal fixation with external fixation. The record also describes observational participants who consented to the study but declined randomization. Their treatment could be selected by the treating physician or the patient. This creates a distinction between the randomized comparison, where treatment assignment is determined by randomization, and observational treatment groups, where assignment reflects preference or clinical judgment. The registry summary additionally describes an observational group for participants whose fractures did not require anterior fixation, although that group is not among the listed arm descriptions.
Enrollment was 4. The study began in 2014-04, had a primary completion date of 2016-06, and its status is terminated. The registry says the principal investigator left the institution and the study was prematurely closed. It further states that the collected data were not analyzed because the patient population was small and achieving statistical significance was not possible.
The primary outcome was functional outcomes measured by the PROMIS v1.2-Physical Function instrument, with a registered timeframe of 24 hrs - 24 months. Listed secondary outcomes include implant breakage or failure, infection, revision surgery, health-related quality of life, predictors of outcome, and functional outcome scores using several named instruments. The registry does not report a completed analysis for these outcomes. It also does not report a detailed recruitment target, sample-size justification, allocation ratio, or visit schedule.
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 | Randomized to Internal Fixator | Randomized to External Fixator | Observational - Internal Fixator | Observational - External Fixator |
|---|---|---|---|---|
| STARTED | 2 | 0 | 1 | 1 |
| COMPLETED | 0 | 0 | 0 | 0 |
| NOT COMPLETED | 2 | 0 | 1 | 1 |
Analysis population for the primary outcome, as defined in the registry: No data was analyzed for this study. The PI left our institution and the study was pre-maturely closed. With such a small patient population, the data that was collected was not analyzed because achieving statistical significance was not possible.
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 | Randomized to Internal Fixator | Randomized to External Fixator | Observational - Internal Fixator | Observational - External Fixator | Total |
|---|---|---|---|---|---|---|
| Participants analysed | 2 | 0 | 1 | 1 | 4 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 2 | 0 | 1 | 1 | 4 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 | 0 | 0 |
| Sex: Female, Male: Female | Participants | 1 | 0 | 1 | 0 | 2 |
| Sex: Female, Male: Male | Participants | 1 | 0 | 0 | 1 | 2 |
| Race and Ethnicity Not Collected | Participants | — | — | — | — | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Functional Outcomes (PROMIS v1.2-Physical Function Instrument), measured over 24 hrs - 24 months.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint was functional outcomes measured with the PROMIS v1.2-Physical Function instrument. The registered timeframe was 24 hrs - 24 months. The stated objective was to compare functional outcomes between subcutaneous internal fixation and external fixation. The registry record does not provide a unit, a score summary, a direction of benefit, or a specific analysis time point within that broad timeframe.
In general, a functional outcome measure is intended to represent how a person functions, rather than to count a clinical event such as a revision procedure. Comparing such outcomes can help describe whether groups differ in the experience or ability captured by the instrument. The interpretation depends on how the instrument is scored, what constitutes a meaningful change, and how measurements are timed. Those details are not reported in the registry record, so no particular score interpretation or threshold can be assigned to this trial.
The endpoint is relevant to the registered comparison because the study sought to assess outcomes following two stabilization procedures. However, the primary endpoint was not analyzed. There is no posted group-level score, treatment contrast, confidence interval, or test result. Consequently, the record identifies what the investigators intended to measure, but it does not establish what the comparison found.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central statistical fact is that the registry reports no analysis of the study data. Although enrollment was 4, the record does not post primary outcome values or a comparison between the internal-fixation and external-fixation groups. There is therefore no treatment-effect estimate to interpret, no confidence interval describing its precision, and no p-value with which to assess statistical evidence. This is an absence of an analyzed result, not evidence that the groups had the same outcome.
The registry explains that the study was prematurely closed after the principal investigator left the institution. It says that the small patient population meant the collected data were not analyzed because achieving statistical significance was not possible. This is the registry's stated rationale. Without an analysis, readers cannot assess the observed direction or size of any difference, or determine how much uncertainty would surround an estimate. Statistical significance is not a substitute for effect size or precision, and neither can be evaluated from the posted primary outcome information.
The enrollment figure also needs to be read alongside the group details. The adverse-event record lists 2 people at risk in the randomized internal-fixator group and none in the randomized external-fixator group. It lists 1 at risk in each observational fixation group. These are the reported safety-group counts; they do not supply a randomized comparison of functional outcomes. In particular, the randomized external-fixator group has no participants listed at risk in the safety record, so the registry does not furnish a two-group randomized safety comparison.
General statistical interpretation: estimates based on very limited data are often imprecise, and an analysis may not reliably distinguish a real difference from random variation. That general point does not produce an estimate for this trial. Because the record says the data were not analyzed, no recalculated result or estimate of precision can be drawn from the primary endpoint.
Planning illustrations based on an observed treatment effect are different from observed trial findings. The registry's stated planning assumptions describe a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the target effect expressed as a fraction of the observed effect. The primary comparison has no posted analyzed effect to anchor such a calculation, and there are no planning counts to interpret as trial results. Any sample-size planning figure is not the number of people observed and is not observed power.
The secondary outcomes do not fill this gap. They identify outcomes the study intended to consider, including complications, quality of life, functional scores, and possible outcome predictors, but the registry lists no analyses. The record therefore supports a description of the question and the study's early termination, not a conclusion about comparative effectiveness, equivalence, or the absence of differences.
9. Statistical Methods Explained
The registered design and the missing analysis determine what can be said statistically. The study was randomized and parallel, but its primary outcome was not analyzed. The concepts below explain how such a comparison would generally be interpreted; they do not describe unreported procedures used in this trial.
What does randomization contribute?
General: Randomization assigns eligible participants to treatment groups by chance. When implemented appropriately, it can reduce systematic differences in baseline characteristics between groups and supports a causal comparison of assigned treatments. With a very small enrolled group, chance imbalances can still occur, and randomization does not guarantee that the groups will be similar in every respect. The registry identifies random allocation but does not report the sequence-generation method, concealment process, or allocation ratio. No details beyond the registered designation should be inferred.
The parallel model means that the intended comparison is between groups assigned to different procedures, rather than a design in which each participant receives both interventions in sequence. The record does not post analyzed outcome data for those groups. The observational arms should not be treated as randomized groups: treatment selection in those arms was based on patient preference, physician preference, or both, according to the arm descriptions. Such selection can be associated with participant characteristics or clinical circumstances, which complicates causal comparisons.
What can masking tell readers?
The registry labels masking as single. In general, masking can reduce the influence of knowledge of treatment assignment on outcome reporting, assessment, or care, depending on who is masked and how the procedure is implemented. The record does not identify the masked party or explain how masking was maintained. It is therefore not possible to judge which potential sources of bias the masking designation was intended to address.
How should an effect estimate and confidence interval be read?
General: An effect estimate expresses the observed difference or contrast between groups using a defined outcome scale. A confidence interval gives a range of values compatible with the data and the statistical model at a stated confidence level. A narrow interval indicates greater precision than a wide interval, while an interval spanning materially different values leaves greater uncertainty about the size and direction of an effect. Neither an estimate nor an interval is reported for the primary endpoint in this record. Thus, there is no numerical contrast to interpret and no precision measure to evaluate.
A p-value, when reported, describes how unusual data at least as discrepant as the observed data would be under a specified null model and its assumptions. It does not measure the probability that a treatment works, nor does it measure the size or clinical importance of a difference. Here, the registry says no data were analyzed, and no p-value is reported. The registry's statement that statistical significance was not possible is an explanation for non-analysis, not a test result.
Why does sample size matter?
General: Sample size affects the amount of information available for estimating group differences. Smaller studies generally produce less precise estimates and have less ability to detect modest differences under a particular design and analysis. A sample-size calculation is a planning exercise based on assumptions, such as the target effect, variability, significance level, power, and allocation. It does not guarantee that a study will achieve a given result, and it cannot replace observed data.
The registry record does not report a sample-size justification or a planned recruitment target. It gives assumptions for a planning illustration: two-sided significance level 0.05, equal allocation, normal approximation, and effects expressed as fractions of an observed effect. Those are calculation assumptions, not reported features of the trial's enrollment or proof that a particular power was achieved. No analyzed primary effect is posted, so a planning illustration based on that effect cannot be used to infer a trial finding. Sample sizes in a planning calculation are not observed power.
What role can over-dispersion play?
General: Over-dispersion occurs when count data vary more than a chosen statistical model expects. If it is ignored, standard errors can be too small and intervals or tests can appear more certain than warranted. This issue can matter for event-count outcomes, but the registry does not report an over-dispersion assessment, a count model, or an analysis of the listed secondary events. It would be inappropriate to claim that over-dispersion was present or handled in this study.
What does the record permit?
The trial record permits description of the randomized question, the parallel design, the small enrollment, the termination, and the lack of analysis. It does not permit reconstruction of an adjusted or unadjusted treatment effect. The number of analyses listed is 0. The registry does not report an analysis population, covariate adjustment plan, missing-data method, or multiplicity procedure. Those omissions mean that readers cannot determine how an eventual estimate would have been calculated or how uncertainty across outcomes would have been addressed.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists several secondary outcomes in addition to the primary functional outcome. These include implant breakage or failure, infection, revision surgery, health-related quality of life, predictors of outcome, and multiple functional measures. Considering multiple endpoints or repeated measurements can raise multiplicity concerns: in general, conducting many statistical tests can increase the chance of at least one apparently positive result under a null hypothesis. Analysts may address this through a prespecified hierarchy, adjustment, or an explicitly exploratory interpretation. The registry does not report a multiplicity procedure or a hierarchy for interpreting outcomes.
The record does not describe how missing outcome data would have been handled, whether data were collected at all scheduled assessments, or what analysis population would have been used. It does state that no data were analyzed for the study. The registry does not report whether an intention-to-treat, per-protocol, or other population was specified. Therefore, none of these analysis choices can be attributed to the trial.
These omissions matter because missingness and the analysis population can affect both the estimate and its uncertainty. General: If outcome availability is related to participants' condition, treatment, or experience, an analysis limited to observed measurements may not represent all assigned participants. The appropriate approach depends on why measurements are missing and on the study design. No missing-data assumptions or sensitivity analyses are reported in the registry record, so their influence cannot be assessed.
There is no reported primary comparison to which a multiplicity adjustment or missing-data method can be applied. The number of analyses listed is 0. The result is not an unadjusted finding or a null finding; it is no analyzed finding posted in the registry.
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 |
|---|---|---|---|
| Randomized to Internal Fixator | 0 | 2 | 0.0% |
| Observational - Internal Fixator | 0 | 1 | 0.0% |
| Observational - External Fixator | 0 | 1 | 0.0% |
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 |
|---|---|
| Randomized to Internal Fixator | 0 of 2 |
| Randomized to External Fixator | 0 of 0 |
| Observational - Internal Fixator | 0 of 1 |
| Observational - External Fixator | 0 of 1 |
The adverse-event record reports no serious adverse events among those listed at risk in the randomized internal-fixator group: 2 at risk and 0 affected. For the randomized external-fixator group, 0 are listed at risk and 0 affected. The observational internal-fixator group lists 1 at risk and 0 affected; the observational external-fixator group also lists 1 at risk and 0 affected. These figures should be read as group-specific registry counts, not as a complete comparative safety analysis.
For other adverse events, the same group counts are listed: 2 at risk and 0 affected in the randomized internal-fixator group, 0 at risk and 0 affected in the randomized external-fixator group, and 1 at risk and 0 affected in each observational group. Death counts are not reported in the registry record. The record does not list serious adverse-event terms.
General interpretation: zero events among a small number of people does not establish that an event cannot occur or that the groups have equivalent safety. A group with no participants at risk cannot provide an observed event rate for that group. The registry also reports that the study data were not analyzed; these adverse-event counts do not supply the missing primary functional outcome comparison.
12. What the Result Does, and Does Not, Mean
The registry establishes that investigators planned a randomized comparison of subcutaneous internal fixation and external fixation for anterior pelvic ring fractures requiring stabilization. It records enrollment of 4, a terminated status, and a primary endpoint based on the PROMIS v1.2-Physical Function instrument over 24 hrs - 24 months. It also records that the primary outcome data were not analyzed.
That means the record does not show whether functional outcomes differed between the randomized groups. It does not provide an estimated effect, a confidence interval, or a statistical test. The absence of a reported analysis is not evidence of no difference, equivalence, or lack of effect. It also cannot establish that one procedure is superior. Those conclusions require outcome data and an analysis that the registry does not report.
The small enrollment and early termination are important context for understanding why the record contains no comparative result. The registry attributes premature closure to the principal investigator leaving the institution and says the small patient population made statistical significance impossible, so the collected data were not analyzed. The record does not provide further detail on recruitment, follow-up completion, or why the randomized external-fixator group has no participants listed at risk in the safety record.
The listed adverse-event counts show zero affected participants in each group with participants listed at risk, while deaths are not reported. These counts are limited and are not a substitute for a formal comparative safety analysis. Likewise, listed secondary outcomes indicate the intended scope of measurement but do not show findings for those outcomes.
For readers, the defensible interpretation is narrow: the study posed a clinically specific randomized question, but it did not produce an analyzed primary outcome result in the registry record. No treatment recommendation or conclusion about comparative clinical outcomes can be drawn from these posted data.
13. Why This Trial Matters Statistically
This trial illustrates an important distinction between a study question and an interpretable result. A randomized design can be useful for comparing assigned treatments, but the design alone does not produce evidence about outcomes. The record identifies the intended randomized contrast and primary measure, yet the study was terminated and the primary data were not analyzed. Without a treatment-effect estimate and its uncertainty, the central statistical question remains unanswered in the registry.
The record also shows why enrollment and analysis status need to be read together. Enrollment was 4, while the safety groups list no participants at risk in the randomized external-fixator group. The observational arms involve treatment choices rather than random assignment. These details make it especially important not to treat all listed groups as if they formed a balanced randomized comparison or to infer a comparative result from the event counts.
General statistical lesson: when a study ends early or has very limited data, the key issue is not simply whether a significance threshold was crossed. Readers need estimates, uncertainty intervals, and transparent information about who was analyzed and how. A non-significant result, if one existed, would not by itself demonstrate that treatments are equivalent. In this case, the registry reports no analyzed result at all, so even that distinction cannot be made from a test output.
The trial is also a reminder that registered secondary outcomes and a detailed primary question are not the same as completed evidence. Listing complications, quality-of-life measures, and functional instruments documents intended measurement domains; it does not show that those measurements were collected, analyzed, or compared. The registry supports a clear account of what was planned and why the intended comparison is unavailable, while leaving its clinical outcome question unresolved.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The principal limitation for interpreting the trial is that the registry states no data were analyzed. There is no posted primary outcome estimate, interval, or test result, and the record lists 0 analyses. The study was terminated after enrollment of 4. The registry says the principal investigator left the institution and the study was prematurely closed, and gives the small patient population as the reason the collected data were not analyzed.
The registered timeframe, 24 hrs - 24 months, does not specify the particular assessment times used for the primary endpoint. A unit, scoring details, and an interpretation threshold are not reported in the registry record. The record does not identify who was masked, how masking was maintained, or the randomization implementation details. It also does not report a recruitment target or sample-size justification.
There is no reported analysis population, missing-data method, multiplicity plan, covariate adjustment, or sensitivity analysis. The record does not explain the discrepancy between overall enrollment and the group-specific safety counts in a way that permits reconstruction of follow-up or outcome availability. In particular, it lists no participants at risk in the randomized external-fixator group. Death counts are not reported.
The registry's listed observational arms were not randomized according to their descriptions, so they should not be interpreted as interchangeable with randomized treatment groups. The study summary also mentions an observational group for fractures that did not require anterior fixation, but this group is not included in the listed arm descriptions. These record limitations prevent a complete accounting of the populations and outcomes, and reinforce that no comparative clinical conclusion can be recovered from the posted information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Comparison of Subcutaneous INFIX and EXFIX for Anterior Pelvic Ring Fractures Requiring Stabilization — NCT02403154.
- Registry record last updated 2018-03-13; status last verified 2018-02.
- Results first posted 2017-12-19.
- 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
This terminated parallel randomized study compared intended subcutaneous internal fixation (INFIX) with external fixation (EXFIX) for anterior pelvic ring fractures requiring stabilization. The registry reports enrollment of 4, a single-masking designation, and a primary outcome of PROMIS v1.2-Physical Function over 24 hrs - 24 months. It also describes observational treatment groups for participants who declined randomization.
The registry states that the principal investigator left the institution, the study was prematurely closed, and no data were analyzed. It attributes non-analysis to the small patient population and the stated inability to achieve statistical significance. No primary outcome estimate or comparative analysis is reported. Safety counts list 0 serious and 0 other adverse events in each group, with the listed at-risk counts varying across groups; deaths are not reported. The record therefore describes the intended question and study status but does not report an analyzed comparison of outcomes.