Feasibility of Bridge for Post-Operative Pain Management in Hip Arthroplasty: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Feasibility of Bridge for Post-Operative Pain Management in Hip Arthroplasty (NCT05017701), a randomized phase not stated study. The primary outcome is Change in Total Opioid Consumption Between Active and Sham Arms..

2. Clinical Question

The study asked whether use of the active Bridge device could be assessed for feasibility in managing pain after total hip arthroplasty. Its primary question concerned the change in total opioid consumption between participants assigned to the active device and those assigned to a sham device, from the day of surgery through Day 5 (120 hours) post-op. Pain, postoperative nausea, and functional recovery were also listed as outcomes.

The registry identifies the study as randomized and quadruple masked, but details about how randomization was conducted and which roles were masked are not reported in the registry record. The study was terminated prematurely by sponsor decision; the record states that the test device was deemed end-of-life by the manufacturer and gives no clinical rationale for termination.

3. Trial Design

The registry describes a randomized, parallel-group study comparing the Bridge device with a sham device. In a parallel design, participants are assigned to a group and the groups are compared; the registry does not describe a crossover between devices. The masking classification is quadruple, although the specific people or roles masked are not reported in the registry record. Allocation concealment, the randomization procedure, and whether masking was assessed are also not reported in the registry record.

The study was a feasibility study focused on post-operative pain management after total hip arthroplasty. The active Bridge device delivered electrical stimulation to the cranial and occipital nerves. The sham device looked the same and used the same placement technique, but did not deliver electrical impulses. This sham arrangement was intended to make the device experience similar across groups while differing in active stimulation.

Actual enrollment was 5: 2 participants with active devices and 3 with sham devices. The registry states that 60 participants were anticipated. The study began on 2022-04-26, and its primary completion date is listed as 2022-11-19. Its status is terminated. The registry states that termination was due to a sponsor decision, without a clinical rationale, and that the test device was deemed end-of-life by the manufacturer.

The primary outcome was change in total opioid consumption between the active and sham arms, measured in doses over the period from the day of surgery to Day 5 (120 hours) post-op. Secondary outcomes addressed pain using the Numeric Rating Scale, postoperative nausea using a Postoperative Nausea and Vomiting Rating Scale, and functional recovery using the Timed Up and Go assessment and the 12-Item Short Form Survey on post-op Day 30. The registry record does not report further details of the intervention schedule, follow-up procedures, or the 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

Analysis population for the primary outcome, as defined in the registry: The study was terminated prematurely due to sponsor decision, with no clinical rationale for the termination. This was a feasibility study and the test device was deemed "end-of-life" by the manufacturer. Only 5 subjects were enrolled out of the 60 anticipated -2 with active devices and 3 with sham devices. All available demographic and outcome measure data from the limited sample size have been reported. Further data reporting would be statistically inappropriate due to the sample size.

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 Change in Total Opioid Consumption Between Active and Sham Arms., measured over Day of surgery to Day 5 (120 hours) post-op.

The primary endpoint concerns change in total opioid consumption between the active and sham arms. The registry specifies the unit as doses and the measurement period as the day of surgery to Day 5 (120 hours) post-op. Opioid consumption is a measure of medication use during the specified recovery period; comparing groups can describe whether recorded use differed between assignments. The registry record does not define the exact data-collection method, which medications counted, or how the change was calculated.

The endpoint is relevant to the stated study aim because the study sought feasibility information about a device for managing pain after total hip arthroplasty. It is not itself a direct pain rating. The listed secondary outcomes include pain measured with the Numeric Rating Scale, as well as postoperative nausea and functional recovery. These measures address different aspects of the post-operative experience and should not be treated as interchangeable with opioid consumption.

The registry description says the sample size was well below the threshold needed to reliably assess outcomes and perform statistical comparisons, and that raw data were included for comparison of opioid consumption. However, numerical outcome values, a group contrast, and an uncertainty estimate are not reported in the registry record. The primary outcome is categorized as having several categories or time points and is not reduced to a single comparison in the registry analysis record. Consequently, the endpoint definition can be described, but its observed magnitude and precision cannot be assessed from the reported information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the study as randomized, quadruple masked, and parallel. These labels describe broad design features, but they do not by themselves explain how participants were assigned or how the data were analyzed. The random sequence method, concealment of assignment, identities of masked roles, and any checks on masking are not reported in the registry record. The statistical analysis plan, including the planned model and handling of repeated measurements, is also not reported.

What does randomization contribute?

General statistical explanation: random assignment is intended to make treatment groups comparable on average with respect to measured and unmeasured characteristics. In small studies, randomization does not guarantee that groups will be balanced. Here, the enrolled groups contained 2 participants with active devices and 3 with sham devices. With such a small sample, individual differences can have a substantial influence on group summaries. Randomization therefore does not eliminate uncertainty or make a small comparison precise.

The parallel design means the two device groups were compared as separate arms rather than by assigning each participant to both devices in sequence. The registry record does not describe the timing of device use beyond the stated outcome timeframes, nor does it report any crossover or rescue-treatment procedures. The sham device shared the active device's appearance and placement technique but did not deliver electrical impulses. That design feature supports a masked comparison in principle; the registry does not report whether participants or other roles correctly guessed their assignment.

What does an outcome comparison require?

General statistical explanation: an analysis of a continuous or count-like outcome typically defines a summary for each group and a contrast between those summaries. The contrast describes the estimated separation between groups, while an uncertainty measure describes how variable that estimate may be. The primary outcome is recorded in doses and described as change in total opioid consumption over the stated post-operative period. The record does not specify whether the intended summary was a mean, median, count model estimate, or another measure. Nor does it report a numerical group contrast or its uncertainty.

The registry describes the primary outcome information as raw data for comparison and explicitly notes that the sample size was too small to reliably assess outcomes and perform statistical comparisons. No individual observations or group-level opioid consumption values appear in the registry record for this analysis. As a result, there is no basis for reconstructing an effect estimate or judging its variability. The primary outcome's several categories or time points were not reduced to a single comparison in the registry analysis record.

Why does precision matter?

General statistical explanation: an estimate is more informative when accompanied by an uncertainty interval. A confidence interval expresses uncertainty under the assumptions of its statistical method; a narrow interval indicates greater precision than a wide interval. Small samples usually contain less information for estimating group differences, so uncertainty may be substantial. This is a general point about statistical precision, not a numerical estimate for this study. The registry record contains no primary-outcome confidence interval or other uncertainty interval.

Statistical significance is not a substitute for effect size or precision. A p-value, if reported, would address compatibility between the observed data and a specified null model under assumptions; it would not state the probability that a treatment works. No p-value or inferential comparison is reported in the registry analysis record. It is therefore not appropriate to interpret the missing analysis as either evidence of equivalence or evidence of a meaningful difference.

How should planning calculations be understood?

General statistical explanation: a sample-size calculation is a planning exercise tied to assumptions about the effect to detect, variability, allocation, significance level, and desired power. A planning illustration based on an observed effect is not the same as a prespecified design calculation, and it is not observed power. The registry record states that any sample-size assumptions use a two-sided significance level of 0.05, equal allocation, a normal approximation, and a stated fraction of the observed effect. Those are assumptions for planning illustrations, not evidence that the trial was designed or conducted according to that calculation. The trial's own sample-size justification is not reported in the registry record.

Because the primary outcome is not represented by a single comparison in the analysis record, no outcome-specific recalculation should be inferred from a single summary contrast. No recalculated estimate is available in the registry entries. More generally, an illustration of the number of participants needed under specified assumptions cannot repair missing outcome data or convert this feasibility study into a confirmatory comparison.

What can be said about the analysis plan?

The registry record lists 0 analyses. This means the record does not list analysis results; it does not establish that no analyses were ever conducted outside the record. The intended statistical model, covariate adjustment, treatment of baseline values, approach to count distributions, and any interim analyses are not reported in the registry record. No assumptions about those choices should be imputed.

General statistical explanation: count outcomes can have variability that differs from the assumptions of simple normal models. Over-dispersion occurs when observed variation exceeds what a model assumes; if it is ignored, uncertainty estimates can be misleading. Whether opioid consumption in this study showed over-dispersion, and whether any model accounted for it, is not reported in the registry record. This general issue cannot be used to infer a specific analysis or result for the trial.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple outcomes: opioid consumption as the primary outcome, and measures of pain, postoperative nausea, and functional recovery. Considering several outcomes or time points creates a multiplicity issue: when many comparisons are examined, the chance of at least one apparently notable result can increase. General statistical practice may address this through a prespecified hierarchy, adjustment, or careful emphasis on estimates and uncertainty. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or which comparisons were planned for formal testing.

The primary outcome description states that the sample size was too small to reliably assess outcomes and perform statistical comparisons. The record lists 0 analyses and does not report a single primary comparison. This prevents assessment of whether any multiplicity procedure was applied or whether outcome reporting followed a prespecified plan. The protocol's statistical analysis plan is not reported in the registry record.

Missing-data methods are not reported in the registry record. The record does not state whether all enrolled participants contributed measurements at each time point, how incomplete observations were handled, or whether any imputation or sensitivity analysis was used. The number of participants in each arm is known, but that alone does not reveal completeness of outcome data.

Analysis populations are likewise not reported in the registry record. It is not stated whether analyses were intended to follow assignment regardless of device use, to include only participants who completed treatment, or to use another population definition. These choices matter because they determine which observations contribute to a comparison. Without the analysis population and missing-data approach, even a numerical outcome summary would require caution; in this record, no numerical outcome comparison is reported.

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 records 0 serious adverse events among 2 participants at risk in the Bridge Device group and 0 among 3 participants at risk in the Sham Device group. Other adverse events were recorded as 0 among 2 at risk in the Bridge Device group and 0 among 3 at risk in the Sham Device group. Deaths were recorded as 0 in each group. No top serious adverse event terms are listed.

These counts describe only the participants included in this small terminated study. Zero recorded events does not establish that an event cannot occur or that the groups have equivalent safety. With so few participants, uncommon events may not appear, and the record does not provide an uncertainty estimate for event frequency. The counts also do not provide information about event severity beyond the serious-versus-other categories or about the timing and relationship of events to device use.

General statistical explanation: safety counts are most informative when read alongside the number of participants followed and the completeness and duration of event monitoring. The registry identifies the numbers at risk, but further details on event collection and follow-up are not reported in the registry record. The absence of listed event terms should be understood as no terms listed, not as a detailed account of all possible safety outcomes.

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

The registry record documents a randomized, quadruple-masked, parallel feasibility study of the Bridge device and a sham device after total hip arthroplasty. It specifies a primary outcome of change in total opioid consumption, measured in doses from the day of surgery to Day 5 (120 hours) post-op, and names additional pain, nausea, and functional recovery outcomes. It also records that 5 participants enrolled, compared with 60 anticipated, and that the study was terminated by sponsor decision.

The record does not report a numerical primary-outcome result, a group difference, a confidence interval, or a p-value. Therefore, it cannot establish the direction, size, or precision of a difference in opioid consumption. The same limitation applies to the listed secondary outcomes: their outcome definitions appear, but numerical findings are not reported in the registry record. The registry's statement that raw data were included for comparison does not substitute for a posted estimate and uncertainty measure in the information available for interpretation.

The small enrollment and premature termination constrain what can be learned. A feasibility study can generate information about the practicality of conducting a larger study, but the registry record does not report specific feasibility metrics such as recruitment rates, device adherence, or completion rates. It would be inappropriate to infer those characteristics from enrollment alone. The stated reason for termination was sponsor decision, with no clinical rationale, and the record says the device was deemed end-of-life by the manufacturer.

The safety counts show no recorded serious or other adverse events and no deaths among the enrolled participants. Those counts do not establish the absence of risk outside this sample. Nor do they show that one device is safer than the other: the observed counts are limited by the small numbers at risk and are not accompanied by comparative uncertainty estimates.

Overall, the registry record supports a description of the study design, intended outcomes, enrollment, termination, and recorded adverse event counts. It does not support a definitive comparative conclusion about opioid consumption, pain, nausea, functional recovery, or safety. Missing results should not be interpreted as proof of no effect, equivalence, or benefit.

13. Why This Trial Matters Statistically

This study is statistically important as an example of the distinction between a clinical question and the evidence needed to answer it. The registry specifies a randomized comparison and a clinically relevant primary measure, opioid consumption after surgery. But the enrollment of 5 participants, rather than the 60 anticipated, and the absence of a posted numerical comparison leave the primary question unresolved in the registry record.

Randomization and masking are valuable design features, but they do not guarantee a precise estimate when the enrolled sample is very small. The allocation was 2 participants with active devices and 3 with sham devices. As a general statistical matter, outcomes in small groups can be strongly influenced by individual observations, and estimates are often uncertain. Reporting an effect estimate together with an uncertainty interval would be important for interpreting any comparison, but neither is reported for the primary outcome.

The trial also illustrates why outcome definitions, analysis plans, and results need to be considered together. The registry identifies measures of pain, nausea, and functional recovery alongside opioid consumption, but does not report numerical results or a multiplicity plan. Without those details, readers cannot determine how the outcomes were analyzed or how much weight to place on a particular comparison.

Finally, feasibility and clinical effect are different questions. The stated aim was to gather feasibility data, while the registry also names clinical outcome measures. The record's enrollment and termination information provide context, but it does not report enough feasibility results to characterize implementation, and it does not provide an estimate of comparative clinical outcomes. Careful separation of these evidence types prevents an incomplete record from being mistaken for either a positive or a negative efficacy finding.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The principal limitation is the very small enrollment: 5 participants, with 2 assigned to the Bridge device and 3 to the sham device, compared with 60 anticipated. The registry itself states that the sample size was well below the threshold needed to reliably assess outcomes and perform statistical comparisons. This limits the precision and stability of any possible group comparison.

The study was terminated prematurely by sponsor decision. The registry reports no clinical rationale for termination and states that the device was deemed end-of-life by the manufacturer. The record does not describe whether termination affected follow-up, outcome collection, or analysis completion. Those details are not reported in the registry record.

Numerical results for the primary outcome and listed secondary outcomes are not reported in the registry record. The record lists 0 analyses and does not provide an effect estimate, uncertainty interval, or p-value. The primary outcome description refers to raw data for comparison, but the summary information does not permit evaluation of the observed group values or their variability.

Other methodological details are absent, including eligibility criteria, participant characteristics, allocation concealment, the identities of masked roles, outcome completeness, analysis populations, missing-data handling, and the statistical analysis plan. The registry also does not report a multiplicity strategy or details of how opioid consumption was collected and summarized. These omissions limit assessment of bias, comparability, and analytic choices.

The recorded absence of adverse events must also be interpreted in the context of the small groups and the limited details about monitoring and follow-up. No event terms are listed as top serious events, but the registry record does not provide enough detail to assess the completeness of event ascertainment. These limitations do not determine what the unreported data would show; they restrict the conclusions that can be drawn from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Feasibility of Bridge for Post-Operative Pain Management in Hip Arthroplasty — NCT05017701.
• Registry record last updated 2025-10-21; status last verified 2025-10.
• Results first posted 2025-10-21.
• 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

The registry record describes a randomized, quadruple-masked, parallel feasibility study of the Bridge device versus a sham device for postoperative pain management following total hip arthroplasty. The primary outcome was change in total opioid consumption, in doses, from the day of surgery to Day 5 (120 hours) post-op. Other listed outcomes address pain, postoperative nausea, and functional recovery.

Enrollment was 5 participants: 2 with active devices and 3 with sham devices, out of 60 anticipated. The study began on 2022-04-26, its primary completion date is listed as 2022-11-19, and its status is terminated. The stated reason was sponsor decision without clinical rationale; the test device was deemed end-of-life by the manufacturer.

The registry record does not report a numerical primary outcome comparison, statistical uncertainty, or a listed analysis result. It records 0 serious adverse events, 0 other adverse events, and 0 deaths in each arm. These counts and the intended outcome definitions describe the record, but they do not establish comparative effectiveness or safety.