HIP: Hip Imaging Protocol: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for HIP: Hip Imaging Protocol (NCT04126161), a non-randomized na study. The primary outcome is Area of Intramuscular Adipose Tissue (IMAT) - CT Scan.

2. Clinical Question

The study asks whether muscle area and intramuscular adipose tissue (IMAT) content measured in the rectus femoris by standard CT imaging can be compared with measurements made using point-of-care handheld musculoskeletal ultrasound. The participants are patients presenting for primary total hip arthroplasty who have both ultrasound and CT scan data available. The registry describes this population as suitable for the comparison because hip CT is performed as standard care before surgery.

The scientific motivation is that muscle characteristics can be used to assess muscle quality, while CT involves ionizing radiation and may only be performed intermittently. The registry describes ultrasound as a handheld approach that does not use ionizing radiation and can be repeated more readily. Those points explain the rationale for studying the measurement methods; they are not evidence that the methods agree in this study.

The primary outcome listed in the record is area of IMAT measured by CT, in cm^2, at Visit 1, up to 1 hour. The stated outcome population requires data from both imaging methods, but the registry does not post the observed CT or ultrasound measurements or a numerical comparison between them. It therefore does not establish from the posted results whether the methods give similar, different, or closely related measurements.

3. Trial Design

The registry identifies HIP: Hip Imaging Protocol as a completed study sponsored by Duke University. The record gives an enrollment of 18 and classifies the study as nonrandomized, unmasked, and crossover. The phase is listed as NA. The registry lists the start as 2019-11-01 and primary completion as 2025-07-10.

The design is intended to compare measurements obtained using two imaging methods: CT and handheld musculoskeletal ultrasound. The CT arm description says patients have standard-of-care CT before primary hip replacement. The ultrasound arm description says patients have ultrasound scans together with standard-of-care CT before primary hip replacement. The registry also identifies a crossover model. These descriptions frame the study as a comparison of measurement methods, not a randomized comparison of two treatments.

The record explicitly cautions that the allocation is nonrandomized and that the arms are not a like-for-like control comparison. The labels CT and Ultrasound should therefore not be read as treatment groups whose clinical outcomes can be contrasted as if participants had been randomly assigned to alternative care. The study objective is measurement-focused: it concerns muscle area and IMAT content in the rectus femoris as assessed with CT and ultrasound.

The record does not report the order in which scans were performed, the time interval between the methods, or whether image acquisition and interpretation were blinded. It lists masking as none, but does not provide further detail about who was unmasked or how measurements were assessed. Specific details of the imaging protocol, including the actual measurement procedures beyond the brief descriptions, are not reported in the registry record.

The registry lists two outcome measures, but no analyses are posted. The status is completed, yet the record contains no numerical endpoint results or statistical comparison. Completion describes the registry status; it should not be mistaken for evidence that results are available or that the study objective was met.

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

Analysis population for the primary outcome, as defined in the registry: Participants with both ultrasound and CT scan data available.

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.

6. Primary Endpoint

The registry lists the primary outcome as Area of Intramuscular Adipose Tissue (IMAT) - CT Scan, measured over Visit 1, up to 1 hour.

The listed primary endpoint is area of intramuscular adipose tissue (IMAT) measured by CT scan. It is a continuous measure reported in cm^2, with the registry specifying a mean and standard deviation. The timeframe is Visit 1, up to 1 hour. The stated population consists of participants with both ultrasound and CT scan data available.

IMAT represents adipose tissue deposited within muscle. The registry describes it as a biomarker of muscle quality. In this study, measuring IMAT is relevant because the objective is to compare muscle characteristics derived from standard CT imaging with those derived from handheld musculoskeletal ultrasound. The rectus femoris is the muscle named for the comparison.

The endpoint description also refers to short-axis and long-axis views, defined by whether the transducer is perpendicular or parallel to muscle fibers. That description does not report an observed value, nor does it give a CT-versus-ultrasound effect estimate. Although the registry’s objective includes both muscle area and IMAT content, the primary endpoint title specifically names CT-measured IMAT area. The record does not report a numerical outcome result, an estimate of agreement, or the precision of a comparison. Consequently, the listed endpoint clarifies what was intended to be measured but does not, by itself, answer whether the imaging methods produce comparable readings.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous outcome summarized as a mean and standard deviation. General statistical explanation can help distinguish what those summaries would convey from what is actually reported. A mean describes the central level of measurements in a group or set of observations. A standard deviation describes the spread of individual measurements around that mean. Neither statistic alone shows how closely CT and ultrasound agree for each participant; the numerical summaries are also absent from the registry record.

What would a paired measurement comparison address?

When two measurement methods are applied to the same participants, each participant can contribute a pair of readings. A paired analysis can focus on within-participant differences, accounting for the fact that the two readings from a person are related. In general, this can be more directly aligned with a method-comparison question than treating the measurements as independent groups. The record classifies this study as crossover and describes both scans, but does not report the exact pairing structure used in analysis, the order of imaging, or any paired analysis results.

A mean difference between methods, if reported, would describe average directional bias: whether one method tends to produce larger readings than the other. A confidence interval around such an estimate would express the uncertainty in the estimated average difference, under the analysis assumptions. A narrow interval would indicate greater precision for that estimate than a wide interval. The registry reports neither a difference nor a confidence interval, so no conclusion about average bias or its precision can be drawn.

Association is not the same as agreement

Correlation is a measure of how readings vary together. If participants ranked similarly on both methods, the measurements could be highly correlated even if one method systematically produced higher values. Conversely, a small average difference could coexist with meaningful disagreement for individual participants. For that reason, method comparison often distinguishes association from agreement and considers the range of individual differences, not only averages. This is general statistical guidance; the registry record does not state that correlation, limits of agreement, or another agreement method was used.

The background summary notes that a correlation between psoas muscle parameters measured by abdominal CT and rectus femoris parameters measured by musculoskeletal ultrasound has previously been shown. It also says a direct comparison of parameters for the same skeletal muscle measured by CT and musculoskeletal ultrasound had not been done. That background rationale is not a result of HIP and does not substitute for the absent study-specific estimates.

What uncertainty measures would add

A confidence interval gives a range of values compatible with the observed data and the statistical model, reflecting sampling uncertainty. It is not a guarantee that the true value falls in that range, and it does not resolve systematic measurement error, selection effects, or missing data. A p-value, when used, evaluates how compatible the data are with a specified null hypothesis under stated assumptions; it does not measure the size or practical importance of an effect. No confidence intervals or p-values are reported in the registry record.

Measurement variability matters because ultrasound and CT may differ in acquisition and interpretation. General sources of variation in imaging comparisons can include positioning, landmark selection, image quality, operator technique, and reading procedures. These are considerations for interpreting a measurement study, not confirmed problems in this study. The registry does not report reliability assessments, repeated reads, operator details, or an evaluation of measurement error.

Why over-dispersion can matter

General explanation: over-dispersion occurs when the observed variability is greater than assumed by a statistical model. When a model understates variability, standard errors may be too small and confidence intervals too narrow, making results appear more precise than the data justify. For continuous measurements, analysts may need to assess the distribution and variability of the observations, including whether a small number of unusually high or low values strongly influence summaries. The registry does not report the measurement distributions or any assessment of model fit, so it is not possible to say whether over-dispersion or another distributional concern arose.

The sample-size illustrations are described as planning calculations based on the observed effect, rather than as the trial’s original design justification. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of the observed effect. General power calculations estimate the sample size that would be expected to detect a prespecified effect under assumptions about variability and analysis. They are planning tools, not a measure of whether a completed study has demonstrated a result. The record does not report the numerical observed effect used for the illustrations or a trial-specific sample-size justification.

The registry does not list an analysis plan or any analysis results. It therefore does not identify the statistical test, model, adjustment variables, handling of paired measurements, or approach to outliers. None of these methods should be inferred from the crossover classification or from the endpoint summary fields. Without those details and the observed estimates, readers cannot independently evaluate the analysis assumptions or reproduce a numerical comparison.

10. Multiplicity, Missing Data and Analysis Populations

The record lists two outcome measures, while identifying CT-measured IMAT area as the primary endpoint. It does not provide the title or result of the other measure in the available registry information. There are no analyses listed. The statistical plan for deciding which outcomes or comparisons would be treated as primary, and how multiple comparisons would be handled, is not reported in the registry record.

Multiplicity arises when several outcomes, comparisons, or analyses are examined. In general, testing many hypotheses can increase the chance that at least one result appears unusual by chance. A prespecified hierarchy, adjustment procedure, or clear distinction between primary and exploratory analyses can help readers understand that risk. The record does not describe such procedures, so it is not possible to determine whether multiplicity was addressed or how it might affect interpretation.

The primary endpoint population is participants with both ultrasound and CT scan data available. This specifies a data-availability condition, but the number of participants meeting it is not reported in the registry record. The registry does not describe how missing imaging data were handled, whether any participants were excluded from an analysis, or whether missing values were imputed. It also does not report reasons for missing measurements or compare participants with and without complete paired data.

Those omissions matter in a method-comparison study because a complete-pair analysis can describe only participants with usable readings from both methods. If data availability is related to measurement quality or participant characteristics, the analyzed observations may not represent all enrolled participants. This is a general limitation to consider, not evidence that such selection occurred. The record does not describe an intention-to-analyze population, a per-protocol population, or any other analysis population beyond the primary endpoint’s both-data-available description.

11. 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.

The registry reports one group titled Ultrasound and Standard of Care Computed Tomography (CT) Scan. In that group, 18 participants were listed as at risk for serious adverse events, 0 were reported as having a serious adverse event, and 0 deaths were reported. The number listed as at risk for other adverse events was 18, with 0 affected. No top serious adverse event terms are listed.

These counts describe what appears in the registry record; they do not establish that no unrecorded events occurred. The record does not provide event narratives, follow-up details, or a separate safety comparison between imaging methods. Since the group includes ultrasound and standard-of-care CT, the figures should not be interpreted as a randomized comparison of the safety of CT against ultrasound. The record reports counts but does not explain how events were collected, assessed, or attributed.

Zero recorded events is a descriptive registry finding, not a statistical demonstration that an event is impossible or that risk is absent. Safety interpretation also depends on the observation period and completeness of reporting, details that are not reported in the registry record. These counts do not provide a basis for treatment advice.

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

The registry record establishes the purpose and broad design of HIP: Hip Imaging Protocol. It describes a nonrandomized crossover study in patients presenting for primary total hip arthroplasty, with the objective of comparing rectus femoris muscle characteristics measured by CT and handheld musculoskeletal ultrasound. CT is described as standard care before surgery, and ultrasound is performed together with CT in the study description.

What the record does not establish is the numerical relationship between the two methods. There are no posted means, standard deviations, differences, correlations, agreement estimates, confidence intervals, or statistical tests. The record therefore does not show whether one method yielded larger measurements, whether the methods tracked one another, or how close paired readings were. The completed status is not a substitute for posted findings.

Even if a future or separate report presents an association between methods, association alone would not demonstrate interchangeability. General statistical interpretation distinguishes ranking participants similarly from producing sufficiently close values for individual measurements. The study question concerns comparison of measurement approaches, so the type of estimate and its uncertainty would be central to interpretation. Those results are not reported in the registry record.

The study also does not compare clinical outcomes of alternative treatment strategies. The registry cautions that allocation was nonrandomized and the arms are not a like-for-like control comparison. It would therefore be inappropriate to interpret the arm labels as randomized treatment assignments or to make causal claims about patient outcomes from them.

The listed primary endpoint gives useful information about what the researchers intended to measure: CT-derived IMAT area, in cm^2, at Visit 1, up to 1 hour, among participants with data from both imaging methods. But an endpoint definition is not an endpoint result. The absence of posted estimates, analysis details, and the number with complete paired data means that neither the magnitude nor precision of the method comparison can be assessed from this registry record.

13. Why This Trial Matters Statistically

This study addresses a practical measurement question: whether handheld musculoskeletal ultrasound can be compared directly with CT for muscle characteristics in the same skeletal muscle. The registry background distinguishes this question from earlier correlations involving different muscles and imaging contexts. Comparing methods within a defined population can clarify whether a less intermittent imaging approach yields measurements that correspond to CT-derived values, but a study objective alone cannot establish that correspondence.

The statistical issue is not only whether group averages differ. For a measurement method to be useful for decisions about individual measurements, researchers and readers may need to know how much readings differ from person to person, whether one method has systematic bias, and how uncertain those estimates are. General method-comparison principles therefore call for attention to paired observations, agreement, and measurement variability, rather than relying on association alone.

The registry’s design labels and population description help set appropriate expectations. It is nonrandomized, classified as crossover, and explicitly cautions that the arms are not a like-for-like control comparison. That framing discourages treatment-effect interpretations and focuses attention on the measurement question. The stated endpoint population, participants with both scan types available, also makes completeness of paired observations relevant.

At the same time, the record lacks the actual outcome results and analysis methods. The statistical importance of the question should not be confused with evidence that either modality performs better or that readings agree. The study is relevant because it targets a direct comparison of CT and ultrasound measures of rectus femoris muscle area and IMAT content; the registry data available for interpretation do not quantify the answer.

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 main limitation for statistical interpretation is that the registry record contains no posted outcome values or analysis results. It lists CT-measured IMAT area as the primary endpoint and states that the comparison concerns muscle area and IMAT content, but does not report estimates for either imaging method. Without those data, readers cannot assess the size, direction, or precision of any difference or agreement.

The primary endpoint is defined for participants with both ultrasound and CT scan data available, but the number meeting that condition is not stated. Enrollment is 18, which does not by itself reveal how many complete paired measurements were available for analysis. The handling of missing measurements and reasons for missing data are not reported.

The registry classifies the study as nonrandomized and crossover and warns that the arms are not a like-for-like control comparison. This limits interpretation of the arm labels as conventional independent treatment groups. The record also does not specify scan sequence, timing between methods, assessor blinding, operator training, reliability procedures, or the statistical method used to compare readings. These details can matter in imaging measurement studies but should not be presumed either present or absent beyond what the record states.

The registry lists two outcome measures but does not provide a complete account of their results or a multiplicity strategy. It reports no analysis populations beyond the both-data-available description for the primary endpoint. The protocol, statistical analysis plan, and sample-size justification are not reported in the registry record. The planning illustrations described for the page are based on an observed effect and stated assumptions, but the observed effect and numerical illustration values are not available in this record. These limitations prevent a full assessment of analytic choices, missingness, and statistical precision.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: HIP: Hip Imaging Protocol — NCT04126161.
• Registry record last updated 2026-08-28; status last verified 2026-08.
• Results first posted 2026-08-28.
• 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.

18. Record Summary

HIP: Hip Imaging Protocol is a completed, nonrandomized crossover study sponsored by Duke University, with enrollment of 18 and phase listed as NA. The registry gives a start date of 2019-11-01 and primary completion date of 2025-07-10.

The study objective is to compare rectus femoris muscle area and IMAT content measured with standard CT imaging and handheld musculoskeletal ultrasound in patients presenting for primary total hip arthroplasty. CT is described as standard care before surgery, and ultrasound is conducted together with CT.

The primary endpoint is CT-measured IMAT area in cm^2 at Visit 1, up to 1 hour, among participants with both ultrasound and CT data available. The registry lists two outcomes and no analyses. Numerical outcome results, a statistical analysis plan, and details of missing-data handling are not reported in the registry record. Safety reporting lists 0 serious adverse events, 0 other adverse events, and 0 deaths among the reported group, with 18 at risk in each adverse-event count.