NSS-2-BRIDGE Study for Total Knee and Hip Arthroplasties, Bariatric, and Kidney Transplant Surgeries: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for NSS-2-BRIDGE Study for Total Knee and Hip Arthroplasties, Bariatric, and Kidney Transplant Surgeries (NCT03834142), a non-randomized na study. The primary outcome is Efficacy of NSS-2 Bridge Device in Changing Perioperative Opioid Consumption.

2. Clinical Question

This is a feasibility and tolerability pilot, as reflected in the official title, as well as an investigation of opioid consumption. Its broad surgical scope includes total knee and hip arthroplasties, bariatric surgery, and kidney transplant donor surgery. However, the primary outcome description and population field do not define one uniform surgical cohort: the population field specifies Kidney Transplant Donor, while the description lists several types of surgery. The record does not report how the primary analysis would handle differences among these populations.

The clinical question is therefore narrower than whether the device generally improves postoperative pain or reduces opioid-related harm. The registered primary endpoint concerns opioid consumption, while pain scores and several recovery measures are secondary outcomes. No numerical results for those endpoints are reported in the registry record. The posted information consequently supports describing the study question and design, but not estimating a change in opioid use or drawing conclusions about pain control.

3. Trial Design

NCT03834142 is registered as a completed study with an enrollment of 20. Its listed start date is 2019-03-08, and its primary completion date is 2021-03-30. The phase is listed as NA. The sponsor is Jacques E. Chelly. The study uses a parallel model, non-randomized allocation, and no masking.

The intervention arm is described as receiving NSS-2-Bridge auricular therapy in addition to standard of care. The control arm receives standard of care without an intervention. The primary outcome description states that the investigators compare with historical controls and can analyze control data only from the period when those controls were in the hospital. The registry also explicitly cautions that the arms are not a like-for-like control comparison. Thus, the control description should not be read as evidence that participants were concurrently randomized to treatment and control.

That distinction matters statistically. In a randomized comparison, allocation is designed to make groups comparable on average, subject to chance. In a non-randomized comparison, treatment groups may differ in measured or unmeasured ways before outcomes are compared. Historical controls add the possibility that care, patient selection, or measurement practices differed over time. These are general design considerations, not claims that a particular difference occurred in this study; the registry record does not report control-selection procedures or a detailed assessment of baseline comparability.

The enrollment figure alone does not describe how participants were distributed across surgical populations, which participants contributed primary-outcome data, or how many were included in each analysis. Those details, along with eligibility criteria, recruitment procedures, and a sample-size justification, are not reported in the registry record. The study's completed status indicates its recorded status, but does not supply the missing numerical endpoint results or establish that every planned analysis was completed.

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: Kidney Transplant Donor

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: Kidney Transplant Donor

6. Primary Endpoint

The registry lists the primary outcome as Efficacy of NSS-2 Bridge Device in Changing Perioperative Opioid Consumption, measured over This could be within a 24hrs, 48hrs, 72 hours, 96 hours, or 120 hours timeframe..

The primary endpoint is mean perioperative opioid consumption, expressed in mg morphine equivalent (MME). A morphine-equivalent measure expresses opioid consumption using a common unit, allowing different opioid medicines to be represented on a shared scale. That is a general property of the measure; the registry does not specify the conversion procedures used in this study.

The registry identifies the endpoint parameter as a mean and its dispersion as standard deviation. A mean describes the average consumption in a group, while the standard deviation describes how spread out individual values are around that average. Reporting both can convey the group-level amount and the variability between participants. The registry record does not report the observed means, standard deviations, an effect estimate, or a confidence interval.

The timeframe is not fixed to a single stated duration: the record says it could be within a 24hrs, 48hrs, 72 hours, 96 hours, or 120 hours timeframe. The primary outcome description limits the historical-control analysis to the time controls were in the hospital. It does not identify which timeframe was ultimately used for the primary result or how different hospitalization lengths were handled.

Opioid consumption is used as a measure of medication exposure, distinct from a direct pain score. Pain Scores are listed among the secondary outcomes, as are postoperative complications and recovery measures. These outcomes may address different aspects of the postoperative course, but the registry record does not provide their numerical results. Without endpoint values and the corresponding analysis details, the primary measure cannot be used to quantify a between-group change.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary measure is continuous: opioid consumption is recorded as an amount in mg morphine equivalent, and the registry names the mean as the summary parameter. For a continuous outcome, a group mean describes its average value. A standard deviation describes the spread of individual measurements around that average. These two summaries are useful for understanding a distribution, but they do not by themselves establish a treatment effect. A comparison also needs an estimate of the difference between groups and information about uncertainty. Those results are not reported in the registry record.

What does a confidence interval convey?

In general, a confidence interval gives a range of values compatible with the data under a specified statistical procedure. Its width reflects precision: a wider interval indicates less precision, while a narrower interval indicates greater precision. A confidence interval is not a guarantee that the true value lies within the particular interval. No confidence interval for opioid consumption is reported in this registry record, so neither the direction nor the precision of an estimated difference can be evaluated.

How should a p-value be read?

In general, a p-value measures how inconsistent the observed data are with a stated null model, assuming the model and analysis are appropriate. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of an effect. A p-value is most informative alongside an effect estimate and its uncertainty. No p-value or primary-outcome analysis is listed in the registry record, so statistical significance cannot be assessed.

Why does allocation matter?

Random allocation can reduce systematic differences between groups at the point of assignment, although it does not ensure identical groups in a particular study. This trial is registered as non-randomized and unmasked. Its primary outcome description refers to historical controls, and the record warns that the arms are not a like-for-like control comparison. In general, historical comparisons can be influenced by changes over time, differences in participant characteristics, or variation in care and outcome measurement. These are possible sources of bias in this design, not confirmed events in this study. The registry record does not report a detailed method for selecting controls, adjustment for baseline differences, or a sensitivity analysis.

What does the timeframe imply?

The primary outcome timeframe could be within a 24hrs, 48hrs, 72 hours, 96 hours, or 120 hours timeframe. The description also says that only control data from when controls were in the hospital can be analyzed. In general, opioid consumption measured over different observation windows is not directly comparable unless the windows and data handling are clearly defined. A longer period could capture more medication use simply because it covers more time; this is a general measurement consideration, not a reported finding. The record does not identify the timeframe selected for the primary analysis or explain how discharge timing was addressed.

Why might over-dispersion matter?

In general, over-dispersion means that outcome variability is greater than a statistical model assumes. When a model underestimates variability, standard errors can be too small and uncertainty can appear narrower than it is. Opioid consumption can be unevenly distributed in many settings, but the registry record does not provide a distribution, model, or evidence of over-dispersion for this study. It also does not report whether the primary analysis used a model, or how the mean and standard deviation were estimated. This concept is therefore relevant as a general consideration, not as a description of the study's reported analysis.

What can planning calculations establish?

The stated planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a fraction of the observed effect. Such calculations are planning illustrations, not observed power and not evidence that a treatment effect exists. Their interpretation depends on an effect estimate and other assumptions. The registry record does not report the observed primary effect or numerical planning sample sizes, and it does not report the trial's own sample-size justification. The stated assumptions should not be mistaken for proof that the study was designed to detect a particular effect.

Because the record lists no analyses, it is not possible to determine which statistical procedure was ultimately used, how missing measurements were handled, whether any covariates were included, or whether results were checked under alternative assumptions. These details are not reported in the registry record. Statistical concepts can clarify what would be needed to interpret a result, but they cannot replace the absent outcome estimates.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Intervention", "Control")
n   <- c(10, 10)
m   <- c(8.3, 33.5)
sp  <- c(9.6, 37.3)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Intervention  10  8.300  9.600  1.433  15.167
CARM  Control  10  33.500  37.300  6.817  60.183

11. Multiplicity, Missing Data and Analysis Populations

The record lists Pain Scores, postoperative complications, comfort wearing the device, time to hospital discharge, time to discharge from the recovery room, time to oral intake, and time to ambulation as secondary outcomes. It identifies eight outcome measures, but does not report an analysis for any of them. The registry record does not describe a multiplicity procedure, such as adjusting inference when several outcomes are tested, or state which secondary outcomes were intended to be confirmatory. In general, examining multiple outcomes can increase the chance of at least one apparently unusual result, so the outcome hierarchy and analysis plan matter.

The registry record does not report a missing-data approach, the number of participants with complete primary-outcome measurements, reasons for missing observations, or an analysis population definition. It does not state whether results were analyzed according to treatment received, assignment, or another rule. Because allocation was non-randomized, there is no basis in this record for describing an intention-to-treat comparison. These absent details limit assessment of selection and attrition concerns.

Likewise, the record does not report a prespecified statistical analysis plan, interim analyses, or any adjustments to the analysis after data collection. No assumptions about these procedures can be made from the completed status alone. These gaps matter because outcome selection, missingness, and analysis choices affect how confidently estimates can be interpreted. With no numerical analyses posted, neither multiplicity nor missing-data effects can be assessed for this study.

12. 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.

For the two kidney groups, the registry records 10 participants at risk in the Intervention-Kidney group and 10 in the Control-Kidney group. Serious adverse events affected 0 participants in each group. Other adverse events affected 0 participants in each group, and deaths are recorded as 0 in each group. The registry lists no top serious adverse-event terms.

These are counts recorded for the listed kidney groups. They should not be generalized automatically to every surgical population named in the study description, and they do not establish that no adverse event of any kind occurred outside the categories or reporting represented by these fields. A count of zero also does not mean that the true risk is known to be zero; with limited observations, uncertainty may remain. That is a general statistical consideration, not a numerical risk estimate for this study.

The record does not report the observation period for these safety counts, detailed event definitions, completeness of adverse-event collection, or a comparative safety analysis. The counts therefore describe what is recorded, but do not permit a precise estimate of relative safety or a conclusion about uncommon events.

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

The registry record establishes that this was a completed, non-randomized pilot study of NSS-2-Bridge, with perioperative opioid consumption designated as the primary outcome. It describes the intervention as device therapy alongside standard care and the control as standard care without an intervention. It also lists secondary measures related to pain, complications, comfort, and recovery. These details define the study's aims; they are not evidence of an outcome.

The record does not report numerical primary-outcome results or analyses. It therefore cannot show whether mean opioid consumption differed between groups, how large any difference was, or how precisely it was estimated. It also cannot establish an effect on pain scores, complications, or recovery measures. The lack of reported results is not equivalent to a finding of no difference, and it should not be interpreted as evidence of benefit or lack of benefit.

The design further limits the interpretation of any potential group contrast. The trial was non-randomized and unmasked, and the primary outcome description refers to historical controls. The record cautions that the groups are not a like-for-like comparison. In general, differences between such groups can arise from factors other than the intervention. The registry record does not report enough detail to assess or adjust for those potential differences.

The safety counts show zero recorded serious adverse events, other adverse events, and deaths in each of the two kidney groups, each with 10 participants at risk. These counts are limited to the reported groups and fields. They cannot establish that risks are absent, particularly for events that are uncommon or incompletely captured.

The most defensible conclusion is therefore about the available evidence: the registry describes the intended comparison and several outcome domains, but its posted information does not permit an estimate of effectiveness or a comprehensive safety assessment. Further interpretation would require numerical outcome results, analysis methods, and information about which participants contributed data.

14. Why This Trial Matters Statistically

This study raises several important statistical issues in a compact pilot design. First, it combines several surgical populations while naming Kidney Transplant Donor in the primary outcome population field. Surgical context can shape baseline characteristics, pain experience, recovery, and medication exposure. Those are general reasons why population definition matters; the registry record does not report how participants were distributed across the procedures or whether results were planned separately by procedure.

Second, the comparison is non-randomized and described as involving historical controls. That means a contrast in opioid use would need careful interpretation even if numerical results were available. In general, randomization helps address systematic baseline differences, while historical comparisons may be affected by time and selection. The record itself notes that the arms are not a like-for-like control comparison. Reporting control selection and adjustment methods would be important for evaluating the strength of any contrast.

Third, the primary outcome has a flexible observation timeframe, with possible windows from 24hrs through 120 hours, and the control data are limited to the hospital period. The time over which medication use is measured is central to interpreting a total consumption measure. Clear specification of the selected window and handling of discharge would help readers understand whether measurements are comparable.

Finally, the study is identified as a pilot focused on feasibility and tolerability, but the registry record does not report numerical primary results, analyses, or a sample-size justification. Pilot studies can inform the practicality of procedures and future study planning, but a small enrollment and absent effect estimates do not establish an intervention effect. The statistical importance of this record lies in the questions it makes visible: clear population definitions, comparable controls, consistent outcome windows, and transparent reporting of estimates and uncertainty.

15. 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 registry record describes a broad set of surgeries, while the primary outcome population field specifies Kidney Transplant Donor. It does not report enrollment by surgery type, so the extent to which each population contributed to the study is unclear. This limits the ability to judge whether a single summary of opioid consumption would represent all participants or whether outcomes might need to be considered separately by surgical group.

The primary outcome timeframe is presented as several possible windows, and control data are described as usable only while controls were hospitalized. The record does not say which window was used, how length of stay affected measurement, or whether intervention and control observations covered comparable periods. This is particularly relevant for a cumulative medication measure.

The control group is described as receiving standard care without intervention, while the primary outcome description refers to historical controls. The registry warns that the arms are not a like-for-like control comparison. It does not report how historical controls were selected, when they received care, or what methods were used to address potential differences between groups. Masking was none, and allocation was non-randomized.

The enrollment is 20, but participant counts for the primary analysis are not reported. Neither numerical primary results nor analyses are listed. The registry record also does not report a sample-size justification, analysis plan, missing-data methods, detailed adverse-event definitions, or the observation period for safety counts. These omissions prevent assessment of effect size, precision, attrition, and the completeness of safety reporting.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: NSS-2-BRIDGE Study for Total Knee and Hip Arthroplasties, Bariatric, and Kidney Transplant Surgeries — NCT03834142.
• Registry record last updated 2022-08-03; status last verified 2022-07.
• Results first posted 2022-08-03.
• 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.

19. Record Summary

NCT03834142 is a completed, non-randomized, unmasked, parallel pilot study with an enrollment of 20 and phase listed as NA. The registered intervention is NSS-2-Bridge auricular therapy in addition to standard of care; the control is standard of care without intervention. The primary endpoint is mean perioperative opioid consumption in mg morphine equivalent (MME), with a possible timeframe within a 24hrs, 48hrs, 72 hours, 96 hours, or 120 hours timeframe.

The primary outcome description refers to historical controls and limits their analysis to the hospital period. The registry cautions that the arms are not a like-for-like control comparison. No numerical primary-outcome results or analyses are reported. In the kidney-group safety counts, 0 serious adverse events, 0 other adverse events, and 0 deaths are recorded in each group, with 10 participants at risk per group. These counts do not provide a complete assessment across all surgical populations.