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 Biomechanical Reconstruction of Three Different Hip Stem Designs in Hip Dysplasia Using a 3D CT-based Planning Software (NCT04904640), a registered phase not stated study. The primary outcome is Correct Reconstruction CLS.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04904640 |
| Phase | Phase not stated |
| Condition | Dysplasia; Hip |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 150 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Istituto Ortopedico Rizzoli |
| Results posted | Yes |
2. Clinical Question
Population
Adults affected by hip dysplasia are the population described in the registry summary. The summary says a random population of 200 CT scans of the pelvis and thigh would be selected. The record lists enrollment as 150, so the scan count in the summary and the enrollment figure are not the same. The registry does not explain how those figures relate or provide further details about the population represented by the scans.
Intervention
The study evaluates three hip stem designs using 3D CT-based software for surgical planning. The CLS arm describes a single-wedge, tapered Zimmer stem; the Wagner Cone arm describes a conical tapered Zimmer stem; and the Aptafix arm describes an anatomical Ortho stem. The record describes implantation plans, but whether the study included actual implantations is not reported in the registry record.
Comparator
The three stem designs are the alternatives of interest: CLS, Wagner Cone, and Aptafix. The registry says allocation is not stated and flags that the arms are not a like-for-like control comparison. It therefore does not establish randomized assignment or a controlled comparison in which the groups began under comparable conditions.
Primary question
The primary outcome is titled “Correct Reconstruction CLS” and concerns the percentage of hips meeting all specified reconstruction criteria for the CLS stem at Day 0. The broader study aim is to evaluate reconstruction with three stem designs. The listed primary endpoint is specific to CLS, however, and the registry does not report a primary endpoint value or an analysis comparing the three designs.
3. Trial Design
The registry describes a completed study of biomechanical reconstruction in hip dysplasia using 3D CT-based software for surgical planning. The brief summary says a random population of 200 pelvis and thigh CT scans from adults affected by hip dysplasia would be selected. The registry enrollment is 150. The record does not explain the difference between the scan count in the summary and the enrollment figure, or whether enrollment refers to people, scans, hips, or another unit.
Three stem designs are described: CLS, a single-wedge tapered Zimmer stem; Wagner Cone, a conical tapered Zimmer stem; and Aptafix, an anatomical Ortho stem. The arm descriptions refer to implantation using CT-based pre-operative planning software. The registry does not clarify whether the designs were implanted in participants or evaluated as plans applied to the scans. The study is marked completed, with start and primary completion dates of 2021-05-10 and 2021-07-10.
This is not documented as a randomized comparison: allocation is not stated, and the registry warns that the arms are not a like-for-like control comparison. The study's stated aim is to evaluate reconstruction across the designs, but the listed primary outcome concerns CLS specifically. Secondary outcomes list combined anteversion, offset, and leg lengthening measures for some or all of the designs. The registry lists 12 outcome measures, but does not provide analysis results. It records zero analyses. The statistical analysis plan, the analysis population, and details about how the study groups or scan-based evaluations were formed are not reported in the registry record.
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: All the 150 patients enrolled in the study underwent a preoperative planning with a particular software, and each hip (200) was studied with three different stem design, so each of them results enrolled in each arm group which represents a different kind of hip stem.
Overall Study
| Stage | Simulated Hips |
|---|---|
| STARTED | 150 |
| COMPLETED | 150 |
| 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.
Population: All the 150 patients enrolled in the study underwent a preoperative planning with a particular software, and every eligible dysplastic hip (200) was studied with three different stem design
| Characteristic | Unit | Simulated Hips |
|---|---|---|
| Participants analysed | 150 | |
| Age, Continuous | years | 50.8 (SD 11) |
| Sex: Female, Male: Female | Participants | 115 |
| Sex: Female, Male: Male | Participants | 35 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 150 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: Italy | hips | 150 |
| height | centimeters | 159.8 (SD 18.3) |
| weight | kg | 66.1 (SD 15.3) |
| BMI | kg/m² | 25.8 (SD 4.9) |
6. Primary Endpoint
The registry lists the primary outcome as Correct Reconstruction CLS, measured over Day 0.
| Element | Registry entry |
|---|---|
| Result type | Count Of Units |
| Measure of spread | not applicable |
| Unit | Hips |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is titled “Correct Reconstruction CLS,” has hips as its unit, and is assessed at Day 0. Its description defines a correctly reconstructed hip as one meeting all five stated criteria at the same time: combined anteversion between 25° and 50°, global offset not inferior to 12% of native offset, leg lengthening not superior to 3 cm, sagittal and coronal tilt not superior to +/-5°, and canal filling not inferior to 80%. The description gives a possible range from 0 to 100 percent, with 100 described as the best result and 0 as the worst.
This combined endpoint is intended to capture several aspects of biomechanical reconstruction together, rather than treating a single parameter as sufficient. Requiring all five criteria simultaneously makes it a stringent composite definition: a hip must meet each condition to count as correctly reconstructed under the registry definition. That can make the endpoint clinically interpretable as a bundled target, while obscuring which individual parameter contributes most when the composite is not met.
The record labels the unit as hips but describes the result as a percentage. It does not report the observed number or percentage meeting the definition, nor does it report how the composite was analyzed. The reason for selecting this endpoint, or its role in the statistical design, is not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted record supplies the study aim, the endpoint definition, three stem descriptions, and a completed status, but no outcome result. It records zero analyses. Consequently, the primary endpoint cannot be interpreted as an observed reconstruction rate, and the registry record does not support a numerical comparison among the three designs. No effect estimate, confidence interval, test statistic, or p value is reported in the registry record.
The primary endpoint is CLS-specific even though the overall aim refers to three designs. This means that the registered primary question, as described, is not itself a direct three-way comparison. Secondary outcome names include measures for combined anteversion and offset across the designs, as well as leg lengthening for CLS and Wagner Cone. The record does not establish a complete set of equivalent outcome measures for all three stems, nor does it report results for any of them.
The registry notes that allocation was not stated and that the arms are not a like-for-like control comparison. Those design features matter when interpreting differences: if groups or scan-based evaluations are not comparable, observed differences could reflect factors other than stem design. The record does not provide sufficient details to assess baseline comparability, assignment, or adjustment for differences. No causal interpretation can be drawn from the registry information alone.
The record lists enrollment as 150, while the summary describes selecting 200 CT scans. It does not reconcile these figures or state clearly how the analysis unit relates to the participant count. This limits assessment of the denominator underlying any percentage, even if an outcome value were available. The registry also describes the primary measure as a percentage while identifying its unit as hips. Further detail about how the percentage was calculated is not reported in the registry record.
The record's completed status does not mean that results are available in the posted information. Similarly, zero entries for events at risk or affected in the adverse-event groups do not establish that no adverse events occurred; the record does not explain those entries. Overall, the available information describes what the investigators intended to evaluate, but not what the evaluation found or how precisely any finding was estimated.
9. Statistical Methods Explained
What does a composite endpoint capture?
As a general statistical concept, a composite endpoint combines multiple criteria into one outcome. In this study's definition, a hip counts as correctly reconstructed only if every listed condition is met at once. This can provide a compact summary of whether several targets were achieved together. It also means that a failure on any one component prevents the hip from meeting the composite, regardless of how well the other components perform. Component-level results are therefore useful for understanding what drives a composite result.
The registry describes five parameters and specifies their thresholds, but does not report component-level values or the primary endpoint result. It also does not state whether the result was planned to be represented as a count, a percentage, or both. The endpoint title and unit refer to a count of hips, while its description defines a percentage. This presentation should be clarified before interpreting any reported estimate.
What would a confidence interval tell a reader?
In general, a confidence interval describes the uncertainty around an estimated effect or outcome under the assumptions of the analysis. A narrower interval indicates greater precision; a wider interval indicates less precision. It is not a guarantee that the true value lies within a particular interval, and its interpretation depends on the study design and statistical method. No confidence interval or outcome estimate is reported in the registry record, so precision cannot be evaluated.
What is known about the statistical analysis?
The record lists 12 outcome measures and zero analyses. A statistical analysis plan, the selected statistical tests, any adjustment strategy, and the treatment of multiple outcomes are not reported in the registry record. The record also does not report an analysis population, missing-data approach, or whether analyses were adjusted for covariates. It would be inappropriate to infer those choices from the endpoint definitions or study aim.
As a general matter, comparison methods should reflect the outcome type, analysis unit, design, and dependencies in the data. For example, multiple hips or multiple planned stem evaluations associated with one participant or scan may not be statistically independent. Methods that ignore such clustering can misstate uncertainty. Whether repeated measurements, paired planning assessments, or clustered observations occurred is not reported in the registry record, so no specific method can be attributed to this study.
How should planning calculations be read?
The record describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. These are assumptions for an illustrative calculation, not a description of the trial's own design or evidence that the study had a particular level of power. The registry does not report the trial's sample-size justification or design assumptions.
In general, planning calculations estimate how many participants per arm would be needed to detect a chosen effect under specified assumptions. When the effect is defined as a fraction of an observed effect, the calculation depends on that effect estimate and on the assumptions used. Such calculations are not observed power and do not show that a completed study has demonstrated an effect. The record's illustration is explicitly not the trial's own design. No calculated participant counts are reported in the registry record.
General statistical interpretation also depends on whether the assumptions match the data. A normal approximation may be an approximation to a sampling distribution; its appropriateness depends on the specific outcome and design. The registry does not report enough information to assess that fit for a study analysis.
Why do allocation and comparability matter?
In general, random allocation can help balance measured and unmeasured characteristics across groups, while nonrandom allocation can leave groups differing in ways that affect outcomes. The registry says allocation is not stated and explicitly notes that the arms are not a like-for-like control comparison. It therefore does not support an assumption that the three groups were randomized or exchangeable. Statistical adjustment can sometimes address measured differences, but cannot automatically remove unmeasured confounding. No adjustment method is reported in the registry record.
There is also uncertainty about the analysis unit: the registry lists enrollment as 150, while the summary describes 200 CT scans, and the endpoint unit is hips. These are distinct descriptions, and the record does not explain their relationship. The appropriate statistical method and interpretation depend on the actual unit of observation and on any within-person or within-scan dependencies. Those details are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 12 outcome measures, including the CLS primary endpoint and secondary measures relating to combined anteversion, offset, and leg lengthening. It records zero analyses. A strategy for controlling the chance of false-positive findings across multiple outcomes is not reported in the registry record. Without results, the number and direction of any statistical comparisons are also unknown. No inference about statistical significance across outcomes can be made from the outcome list alone.
Missing-data methods and the amount of missing outcome information are not reported in the registry record. The record does not state whether all eligible scans, hips, or planned evaluations contributed data, or how incomplete measurements would be handled. It also does not identify an analysis population, such as all enrolled participants or a subset with evaluable scans. This matters because exclusions or incomplete measurements can change both the effective denominator and the group composition.
Enrollment is listed as 150, while the study summary refers to selecting a random population of 200 CT scans. The relationship between participants, scans, and hips is not stated. The registry also does not report whether the three stem plans were assessed in the same scans or in separate groups. Those design details would affect both the analysis population and the dependence structure of the data. These omissions prevent a complete assessment of multiplicity, missingness, and the population represented by any potential estimate.
11. What the Result Does, and Does Not, Mean
The registry record establishes that the study was marked completed and that it aimed to assess biomechanical reconstruction in hip dysplasia with three stem designs using CT-based planning software. It also gives a detailed threshold-based definition for the CLS primary endpoint and identifies several secondary outcomes. These details describe the research question and the planned measurements; they do not establish an outcome.
No primary or secondary results are reported in the registry record, and zero analyses are listed. Therefore, there is no posted evidence in this record to quantify how often the CLS criteria were met, how the stem designs differed, or how uncertain any comparison might be. The endpoint definition alone cannot show whether a design achieved a better or worse reconstruction.
The study's completed status should not be read as confirmation that a result was entered into the registry. Nor should the adverse-event entries, which show zeros for the listed groups, be read as proof that no events occurred: the registry does not explain whether those entries reflect collected data, unavailable data, or another reporting state.
The record also does not permit conclusions about real-world surgical outcomes, patient benefit, or comparative safety. Its stated focus is biomechanical reconstruction evaluated with planning software, and the record does not clarify whether actual implantations took place. Further, the allocation and group comparability are not established. The information supports describing the study's aim and endpoint, but not claiming that any stem design works, fails, or is superior.
12. Why This Trial Matters Statistically
This study raises a useful statistical question: how should reconstruction be evaluated when success depends on several anatomical parameters being within specified limits at the same time? A composite endpoint can express a multi-part target in one measure, but the all-criteria requirement makes component-level reporting important. Without those components, a reader cannot tell which parameter most often prevents a hip from meeting the combined definition.
The comparison also illustrates why the analysis unit and study design need clear reporting. The registry refers both to 150 enrolled participants and to selecting 200 CT scans, while the primary measure uses hips as its unit. The relationship among these units is not explained. If multiple measurements are related within a person or scan, that structure can affect statistical uncertainty. The record does not provide the details needed to evaluate it.
Finally, a completed registry entry is not a substitute for reported estimates. The record specifies three designs and multiple outcomes but lists zero analyses. Without numerical results and a statistical plan, readers cannot assess effect size, precision, multiplicity, or comparability. These reporting gaps are important because a well-defined question and endpoint are only part of the evidence needed to interpret a clinical study.
13. 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 main limitation of the registry information is the absence of outcome results and analyses. The primary endpoint is defined, but no value, uncertainty estimate, or comparison is reported. The registry's completed status therefore cannot be used to infer what the study found.
There are unresolved design and denominator details. The record lists enrollment as 150, while the summary describes a random population of 200 CT scans. It does not explain the difference, define the relationship between participants and scans, or clarify how hips entered the analysis. Allocation is not stated, and the record warns that the arms are not a like-for-like control comparison. It is also unclear whether the stem designs were evaluated through actual implantation, through plans applied to scans, or through another process.
The primary outcome description defines a percentage but labels the unit as hips. The record does not explain the calculation or provide component-level outcome values. Although 12 outcome measures are listed, the registry does not report an analysis plan, multiplicity strategy, missing-data methods, or analysis population. The reason for the endpoint thresholds and the sample-size justification are not reported in the registry record.
These limitations concern what can be learned from the registry record; they do not establish that the full study had no additional methods or results. Such information is not reported in the registry record.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Biomechanical Reconstruction of Three Different Hip Stem Designs in Hip Dysplasia Using a 3D CT-based Planning Software — NCT04904640.
- Registry record last updated 2021-09-09; status last verified 2021-02.
- Results first posted 2021-09-09.
- 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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17. Record Summary
NCT04904640 is a completed registry study sponsored by Istituto Ortopedico Rizzoli. It concerns biomechanical reconstruction in hip dysplasia using 3D CT-based pre-operative planning software and describes CLS, Wagner Cone, and Aptafix stem designs. The registry lists enrollment as 150 and the study summary describes selecting a random population of 200 pelvis and thigh CT scans from adults affected by hip dysplasia.
The primary outcome is titled “Correct Reconstruction CLS,” uses hips as its stated unit, and defines success by meeting five biomechanical criteria together at Day 0. Secondary outcomes include measures of combined anteversion, offset, and leg lengthening. The study is marked completed, with start and primary completion dates of 2021-05-10 and 2021-07-10.
The registry lists zero analyses and reports no outcome results. Allocation is not stated, and the registry notes that the arms are not a like-for-like control comparison. The relationship between the enrollment figure and scan count, the analysis population, and the statistical analysis plan are not reported in the registry record.