Feasibility of the Hip Instructional Prehabilitation Program for Enhanced Recovery (HIPPER): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Feasibility of the Hip Instructional Prehabilitation Program for Enhanced Recovery (HIPPER) (NCT02969512), a randomized na study. The primary outcome is Hospital Anxiety and Depression Scale - Anxiety Subscale (HADS-A).

2. Clinical Question

The study summary describes the work as a randomized controlled trial focused on feasibility, including process, resource, management, and treatment issues, alongside clinical outcomes. The other outcomes listed include depression, hip-related symptoms and function, rehabilitation self-efficacy, usability, physical activity, health-related quality of life, and equipment. The registry record does not report a result for these measures or an estimate of how the groups differed. Accordingly, the clinical question can be described from the planned comparison, but the record does not establish the observed size or precision of any clinical effect.

3. Trial Design

HIPPER is identified in the registry as a randomized, parallel-group study with single masking. The masking field does not state which people were masked, and the randomization procedure is not reported in the registry record. The study is marked completed, with enrollment of 51. The registry lists a start date of 2021-01-10 and a primary completion date of 2023-04-25. Its phase is listed as NA.

The two groups received different forms of online education before hip replacement. HIPPER participants were offered 12 interactive web modules of approximately 20 minutes each. Portal access was arranged through email or phone, according to participant preference; the available description ends before further access details are given. The OASIS group received 2 hours of online educational webinars, described as current practice. No additional details about treatment adherence, completion of modules, webinar attendance, or intervention fidelity are reported in the registry record.

The study summary describes a 2-year randomized controlled trial intended to assess feasibility indicators as well as clinical outcomes. The listed clinical measures include anxiety, depression, pain, daily activities, self-efficacy, physical function, and health-related quality of life. The registry also lists usability and an equipment checklist among its secondary outcomes. The primary outcome was HADS-A anxiety score, with measurement planned at baseline, 7-10 days before surgery, and 30 days after surgery.

The record does not describe how participants were recruited, the sequence used to allocate them, whether allocation was concealed, or the planned approach to analysis. Those design details are not reported in the registry record. The record identifies the sponsor as the University of British Columbia, but does not provide a detailed protocol or a statistical analysis plan.

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

Reasons for not completing this period:

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 Hospital Anxiety and Depression Scale - Anxiety Subscale (HADS-A), measured over T1 (Baseline); T2 (7-10 days before surgery); T3 (Post-Intervention, 30 days after surgery).

The primary endpoint is the Hospital Anxiety and Depression Scale anxiety subscale (HADS-A). The registry describes it as a measure of anxiety symptoms made up of 7 items, each rated from 0-3 and summed to a total score from 0-21. Higher scores indicate worse outcomes, meaning greater anxiety. The score is reported as a mean with standard deviation, consistent with treating it as a continuous measure.

The listed measurement occasions are T1 at baseline, T2 7-10 days before surgery, and T3 30 days after surgery. This repeated schedule can describe anxiety at different points in the pre-surgical and post-intervention period. The record labels the last occasion as post-intervention, 30 days after surgery; it does not explain how the timing was handled for participants whose surgery dates or follow-up schedules differed.

As a patient-reported symptom measure, HADS-A provides a standardized way to quantify reported anxiety rather than relying only on a general impression. A group mean can describe the average score, while the standard deviation describes how spread out participants' scores are around that mean. These summaries do not, by themselves, show each participant's experience or establish whether a group difference is statistically or clinically important.

The registry record does not report HADS-A means, standard deviations, changes, group contrasts, confidence intervals, or test results. It therefore supports a description of what the primary endpoint measures and when it was intended to be measured, but not a conclusion about the observed anxiety outcomes.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized, parallel-group design. In a randomized study, a procedure is used to assign participants to groups, with the aim of reducing systematic differences in participant characteristics between groups. Randomization does not guarantee that groups will be identical, especially in a study with limited enrollment. The specific randomization procedure and allocation concealment are not reported in the registry record, so the safeguards used to implement assignment cannot be assessed from this information.

Parallel-group means that participants were assigned to one of the two education approaches: HIPPER or OASIS. The intervention descriptions distinguish an interactive online module program from educational webinars. The record identifies the study as single-masked, but does not specify who was masked. Because the interventions differ in format, the registry description alone does not clarify how masking was implemented or which assessments could have been affected by knowledge of group assignment.

The primary outcome is continuous: HADS-A is a numerical score, and the registry says it is summarized using a mean and standard deviation. A mean is the arithmetic average of scores in a group. The standard deviation describes the variability of individual scores around that average. These summaries are useful for describing the outcome distribution, but they do not give a direct account of every participant’s response. No group means or standard deviations are reported for HADS-A in the registry record.

Measurement is planned at three occasions: baseline, 7-10 days before surgery, and 30 days after surgery. Repeated measurements can be used to describe how scores vary over time and to compare patterns between groups. Such analyses need to account for the relationship between measurements from the same participant. The registry record does not report the statistical model, contrast definitions, or method used to account for repeated observations. It also does not report an analysis that reduces the multiple time points to a single comparison; the record notes that the primary outcome has several categories or time points and is not reduced to one comparison.

General statistical explanation: a confidence interval communicates uncertainty around an estimated quantity. A narrower interval indicates greater precision under the model and assumptions used; a wider interval indicates less precision. An interval is not a guarantee that the true value lies within its bounds. No confidence interval for HADS-A is reported in the registry record, so the precision of a comparative estimate cannot be evaluated.

General statistical explanation: a p-value is calculated under a statistical model and a null hypothesis, and indicates how compatible the observed data are with that hypothesis. It does not quantify the probability that the hypothesis is true, the clinical importance of a difference, or the probability that a finding will replicate. No primary-outcome p-value or inferential analysis is reported in the registry record. As a result, statistical significance cannot be assessed from this record.

The registry lists several secondary outcomes. When multiple outcomes, time points, or comparisons are considered, the chance of obtaining at least one apparently unusual result can increase. Statistical methods may address this through prespecified testing hierarchies or adjustments, but the registry record does not report whether such methods were planned or used. It also does not identify a hierarchy among the secondary outcomes.

General statistical explanation: over-dispersion occurs when the observed variability is greater than a statistical model expects. If a model does not account for that extra variability, its standard errors and confidence intervals may be too optimistic. This concept is not directly assessable from the registered HADS-A summaries because no outcome distributions or fitted models are reported; the endpoint is described as a continuous score, and the record gives no diagnostic information.

The sample-size assumptions described for planning illustrations are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The illustrations are based on fractions of the observed effect. Such figures are planning scenarios, not observed power and not a report of the trial’s original design justification. The registry record does not report the original sample-size justification or the numerical planning estimates in the registry record for this account.

The record does not state whether the primary analysis was intended to follow intention-to-treat, per-protocol, or another population definition. It does not describe a missing-data method, adjustment variables, model diagnostics, or interim analyses. These omissions limit the ability to reconstruct or evaluate the intended statistical analysis. General principles can explain what these methods would address, but cannot identify which approach was used in this trial.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome is HADS-A, measured at multiple time points, and the registry lists several secondary outcomes. This creates the possibility of multiple statistical comparisons if group differences are assessed across outcomes or occasions. General statistical explanation: testing many hypotheses without an appropriate plan can increase the chance of at least one result appearing notable by chance. Prespecifying a primary contrast, ordering secondary tests, or adjusting for multiple comparisons are possible approaches. The registry record does not report whether any of these approaches were planned or applied.

The primary outcome is not reduced in the record to one comparison because it has several categories or time points. The record does not specify whether the main analysis would compare groups at a particular time, compare changes from baseline, or model the full pattern over time. The analysis plan and any multiplicity strategy are not reported in the registry record. Therefore, the intended interpretation of a primary-outcome test cannot be reconstructed.

Missing data are also important for repeated outcomes. Participants may have scores at some occasions but not others, and the number included can differ across analyses. The registry record does not report how many HADS-A observations were available at each time point, reasons for missingness, or how incomplete records were handled. It does not state whether any imputation or other missing-data method was used.

The analysis population is not specified. In particular, the registry does not say whether all randomized participants were intended to be analyzed in their assigned groups or whether a different population definition was used. The number analyzed for the primary endpoint is not reported in the registry record. Without these details, it is not possible to judge whether the analysis preserved the randomized comparison or how missing outcomes might have affected its interpretation.

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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: death of a participant (4.0%).

The adverse-event entries record 0 serious adverse events among 26 participants in HIPPER and 1 among 25 participants in OASIS. The death count is 0 for HIPPER and 1 for OASIS. The listed top serious-event term is “Death of a participant,” with 4.0% recorded. These are registry counts and a registry-listed term; they should not be read as a causal comparison between the education approaches.

The figures do not establish that an intervention caused or prevented an event. The registry record does not report the relationship of the death or serious event to study participation, the educational intervention, or surgery. It also does not provide narrative details about the event, its timing, or the criteria used to classify seriousness. Those details are not reported in the registry record.

Counts should be read alongside their group denominators, since the groups contain different numbers of participants. The entries describe the number of participants affected, not a complete account of all possible harms or symptoms. No other non-serious adverse-event counts are listed in the adverse-event details. The serious-event data therefore provide limited descriptive safety information, not a basis for attributing the event to either group’s educational program.

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

The registry record establishes that HIPPER was a randomized comparison of online prehabilitation education with OASIS online webinars among people with hip osteoarthritis. It identifies anxiety measured by HADS-A as the primary outcome and gives the intended assessment occasions. It also lists 51 enrolled participants and describes the two education approaches. These details explain the trial question and its general design.

The record does not report numerical HADS-A results, a comparison between groups, confidence intervals, or p-values. It therefore cannot show whether average anxiety scores differed, how large a difference might have been, or how precisely a difference was estimated. The same limitation applies to the listed secondary outcomes. The study summary describes the intent to assess feasibility, but numerical feasibility findings are not reported in the registry record.

General interpretation: a nonsignificant result, if one were reported, would not by itself establish that two approaches are equivalent. An equivalence or non-inferiority conclusion requires a suitable design and prespecified margins, neither of which is reported in the registry record. Likewise, the absence of a reported outcome result is not evidence that no difference occurred.

The enrollment total should not be treated as the number with complete outcome data. The record does not state how many participants contributed HADS-A scores at each occasion, whether all randomized participants were retained, or how missing data were managed. Without those details and the numerical outcome analyses, neither the size of any group effect nor its robustness can be judged.

The adverse-event entries record one serious adverse event and one death in OASIS, and none in HIPPER. These counts do not establish a causal relationship with group assignment. The record does not report relatedness or event context. Thus, the safety information is descriptive and should not be used to claim that either educational approach is safer.

The study is presented as a feasibility trial whose findings were intended to inform refinement of a future program and a larger multi-site evaluation. Its registered design and outcomes are relevant to that developmental question. However, the registry record alone does not give the findings needed to determine whether feasibility targets were met or what clinical outcome estimates were observed.

13. Why This Trial Matters Statistically

Feasibility studies address whether a larger study and its procedures can be carried out, alongside the possibility of collecting clinical outcome information. The HIPPER summary explicitly includes process, resource, management, and treatment issues among its feasibility indicators. It also lists clinical outcomes spanning anxiety, depression, function, self-efficacy, activity, and quality of life. Separating feasibility questions from treatment-effect questions is important: a study can inform trial procedures without providing a precise estimate of clinical benefit.

The comparison also concerns two delivery formats for pre-surgical education. HIPPER is described as interactive online modules, while OASIS is described as webinars. The registered descriptions make the intervention contrast understandable, but do not report attendance, module completion, user experience results, or the extent to which each approach was delivered as intended. These implementation details would help interpret feasibility, but are not reported in the registry record.

The primary outcome is measured before and after surgery, allowing the planned assessment to cover more than one stage of care. Repeated assessments can be informative, but they require clear definitions of the principal contrast and careful treatment of incomplete follow-up. The registry record specifies the time points, yet does not report the statistical analysis plan or outcome results. This leaves the proposed measurement structure visible while the empirical findings remain unavailable in the record.

The study summary states that the findings were intended to support refinement of a standardized and geographically accessible program for evaluation in a larger multi-site trial. That goal gives the feasibility focus practical relevance as a research-development step. The registry record does not report whether the program was refined or whether a subsequent trial was undertaken. Statistically, the record is most useful for understanding the design and planned measurement, not for drawing conclusions about comparative effectiveness.

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 outcomes is the absence of numerical results. Although HADS-A is identified as the primary endpoint and several secondary outcomes are listed, outcome means, standard deviations, group contrasts, and inferential results are not reported in the registry record. The analysis count is 0. No clinical outcome conclusion can be drawn from an endpoint description alone.

The record does not report the original sample-size justification, a statistical analysis plan, or details of the randomization procedure. It identifies the study as single-masked but does not say who was masked. These omissions prevent assessment of how assignment was implemented and what safeguards were used to limit bias.

For the repeated HADS-A measurements, the record gives assessment occasions but not a primary contrast or model. It does not state how missing observations, participants who did not complete the intervention, or changes in timing were handled. The number with outcome data at each time point and the analysis population are not reported in the registry record. These details matter when evaluating the completeness and comparability of observed data.

The interventions are described at a high level, but adherence and implementation outcomes are not reported in the record. The HIPPER access description is incomplete, and the record does not give results for usability or equipment outcomes. Further details about recruitment, participant characteristics beyond the summary description, and follow-up are also not reported in the registry record.

Finally, the adverse-event entries provide limited information about event context and relatedness. The recorded death cannot be attributed to an intervention from the available information. These limitations are specific to what the registry record reports; they do not establish that the underlying study lacked additional methods or results.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Feasibility of the Hip Instructional Prehabilitation Program for Enhanced Recovery (HIPPER) — NCT02969512.
• Registry record last updated 2026-08-17; status last verified 2026-06.
• Results first posted 2026-08-17.
• 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

NCT02969512 is the completed HIPPER randomized, parallel-group study sponsored by the University of British Columbia. The registry records enrollment of 51 participants and compares 12 interactive HIPPER online modules with OASIS online educational webinars. The primary outcome is HADS-A anxiety score, planned at baseline, 7-10 days before surgery, and 30 days after surgery.

The record lists secondary outcomes covering depression, hip symptoms, rehabilitation self-efficacy, usability, daily activities, physical activity, health-related quality of life, and equipment. It records 0 serious adverse events among 26 HIPPER participants and 1 among 25 OASIS participants, including 1 death in OASIS. The registry does not report numerical primary or secondary outcome analyses, the analysis population, missing-data methods, or a detailed statistical plan. Consequently, comparative clinical effects and their precision cannot be evaluated from the registry record.