BFR Therapy in Patients With Rotator Cuff Tears: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for BFR Therapy in Patients With Rotator Cuff Tears (NCT04384120), a randomized na study. The primary outcome is Strength.

2. Clinical Question

3. Trial Design

The registry record describes a randomized, double-masked, parallel-group trial with an enrollment of 30. It lists two rehabilitation groups: rotator cuff rehabilitation using BFR and rotator cuff rehabilitation without BFR. The posted outcome summaries include 15 participants in each group. The record does not describe who was masked or how masking was maintained.

Eligible participants were described as people with rotator cuff tears planning either nonoperative physical therapy or operative arthroscopic rotator cuff repair. The two treatment pathways appear within each rehabilitation strategy, but the record does not report how many participants followed each pathway, whether allocation was stratified by treatment pathway, or separate outcomes by pathway. Consequently, the posted group summaries do not establish whether the results were similar for operative and nonoperative care.

The study start is listed as 2020-06-01 and primary completion as 2022-05-01. Its status is TERMINATED. A reason for termination is not reported in the registry record. The record describes follow-up through study completion, with an average of 12 months post-operative follow-up. It does not explain how that timeframe was applied to participants treated nonoperatively.

The intervention is a rehabilitation approach using BFR cuffs; the comparator is rehabilitation without the cuffs. The registry lists strength as the primary outcome and range of motion, pain score, and Patient Reported Outcomes Measurement Information System as secondary outcomes. The original sample-size justification, planned analysis model, interim analyses, and analysis populations are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

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 Strength, measured over through study completion, an average of 12 months post-operative follow-up.

The primary endpoint is strength, quantified in pounds using dynamometers. Strength is a continuous measure: each participant’s measurement can take a range of values, and the registry reports group means with standard deviations. Muscle strength is relevant to the trial’s stated aim because the investigators wanted to assess whether rehabilitation with BFR would be associated with strength gains after a rotator cuff tear and its treatment.

The timeframe is listed as through study completion, with an average of 12 months post-operative follow-up. The record does not specify which measurement occasions contributed to the reported mean, whether the figure represents a particular follow-up visit or a summary across visits, or how the timeframe was handled for participants who did not have surgery. It also does not report a separate result for change from baseline or for strength at each time point.

The posted summaries give a mean and standard deviation for each rehabilitation group, along with a mean-difference estimate and an unadjusted comparison. These describe the observed group summaries; they do not by themselves show the pattern of individual trajectories or establish whether any difference would be important to patients. A threshold for a clinically important strength difference is not reported in the registry record.

7. Results Posted in the Registry

• Rotator Cuff Rehabilitation Without BFR: mean 6.05 versus 7.39 on control; difference -1.34 (95% CI -3.87 to 1.19), standardized effect d = -0.38; z-test p = 0.300.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Range of Motion

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Rotator Cuff Rehabilitation Without BFR: mean 65.10 versus 82.40 on control; difference -17.30 (95% CI -33.01 to -1.59), standardized effect d = -0.79; z-test p = 0.031.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Rotator Cuff Rehabilitation Without BFR than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Pain Score

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Rotator Cuff Rehabilitation Without BFR: mean 26.30 versus 30.30 on control; difference -4.00 (95% CI -7.98 to -0.02), standardized effect d = -0.72; z-test p = 0.049.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Rotator Cuff Rehabilitation Without BFR than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The registry lists range of motion, pain score, and Patient Reported Outcomes Measurement Information System as secondary outcomes. Summary results are posted for range of motion and pain score, while results for Patient Reported Outcomes Measurement Information System are not reported in the registry record. The available secondary comparisons have a different pattern from the primary strength comparison: their unadjusted confidence intervals exclude zero, whereas the strength interval includes zero.

This contrast in statistical results does not mean the secondary outcomes are more reliable or more important than the primary outcome. Each outcome measures a different aspect of the rehabilitation experience, and a difference on one measure does not establish a difference on another. The registry does not report the scale interpretation, a clinically important threshold, or how outcome measurements were selected and summarized across follow-up. The score differences therefore cannot be assigned a clinical meaning from the posted numbers alone.

Unadjusted secondary results carry less weight when multiple outcomes are examined because the chance of at least one apparently notable result can increase with repeated testing. The record does not report a correction or other multiplicity plan, and it does not list reported secondary analyses. The results are best treated as descriptive or exploratory signals rather than as independent confirmation of the primary result. The unavailable patient-reported outcome summary further limits any overall account of participant experience.

The secondary outcomes are related to the trial’s stated aims, but they do not fill gaps in the primary analysis. Separate results by operative and nonoperative pathway, by follow-up time, and by analysis population are not reported in the registry record. Accordingly, the overall pattern should be interpreted as incomplete evidence across several distinct outcomes, not as a single combined judgment about rehabilitation.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Range of Motion
• Pain Score
• Patient Reported Outcomes Measurement Information System

9. Statistical Interpretation

10. Statistical Methods Explained

What does a group mean describe?

A mean is the average of the observed measurements in a group. For a continuous outcome such as strength, it gives a concise description of the group’s central value, but it does not show every participant’s measurement or the spread of individual responses. The standard deviation describes how dispersed measurements are around the group mean. A larger standard deviation indicates greater variability among the recorded measurements; it is not the uncertainty in the estimated mean itself.

For strength, the registry reports means and standard deviations in pounds. The two group summaries are based on the posted group sizes. They are descriptive statistics, and interpretation of a between-group contrast also depends on how the contrast and uncertainty were estimated. The specific analysis model used by the study team is not reported in the registry record.

How should the mean difference be read?

The comparison is oriented as the group without BFR minus the group using BFR. A negative estimate therefore indicates a lower group mean in the without-BFR group for that outcome; it is not a separate measurement of individual change. The primary comparison is an unadjusted mean difference based on the posted summaries. It does not account, in the reported result, for whether a participant had operative or nonoperative treatment, or for any other participant characteristics.

In general, an unadjusted comparison is a direct contrast between groups without adjustment for additional variables. Random allocation is intended to create groups that are comparable on average, but a small trial can still have chance imbalances. The registry does not report adjusted analyses or enough detail to determine whether other planned analyses were conducted.

What do a confidence interval and a p-value contribute?

In general, a confidence interval expresses uncertainty around an estimated quantity under the analysis assumptions. Its width communicates precision: a wider interval allows a broader range of values than a narrower one. Whether the interval includes zero is relevant for a difference, because zero corresponds to no difference on that scale. The confidence-interval level is not reported in the registry record, so it should not be assigned a level that the record does not state.

A p-value describes how compatible the observed data are with a specified null hypothesis under the statistical model. It is not the probability that the null hypothesis is true, nor does it measure the size or importance of an effect. The reported p-values are unadjusted. The registry record does not report the statistical test or model underlying a sponsor analysis, and no primary analyses are listed in the analysis fields. The displayed comparisons should therefore be read as unadjusted summary-statistic comparisons, not as a complete account of the trial’s analysis plan.

Why does variability matter?

General explanation: when participant measurements vary substantially, a group mean is estimated less precisely unless the study includes enough observations to characterize that variation. The standard deviations in the registry describe observed variability in each group. They do not capture every source of uncertainty, such as missing measurements, differences between treatment pathways, or choices about which follow-up measurement to analyze.

For repeated outcomes, measurements from the same participant are related rather than independent. A model that uses measurements over time may account for that relationship, but the registry record does not report whether such a model was used. The primary result is a summary through study completion, and the exact construction of that summary is not reported.

What can the posted comparisons establish?

The comparisons characterize differences between the posted group summaries, with uncertainty described by the confidence intervals. They do not show whether BFR caused an outcome difference, whether a change occurred within either group, or whether results differ between operative and nonoperative participants. Those questions require details about allocation, follow-up, analysis populations, and outcome timing that are not reported in the registry record. The randomized design is important context, but it does not remove uncertainty arising from the small enrollment, incomplete analysis information, or the terminated status.

Secondary comparisons require additional caution because several outcomes are listed. When many outcomes are examined, some results may appear notable by chance even if no true differences exist. The registry record does not report a multiplicity strategy. The unadjusted secondary p-values therefore should not be interpreted as if they were the sole planned test. The missing Patient Reported Outcomes Measurement Information System results also mean that the posted secondary summaries do not cover every listed outcome.

11. Confidence Intervals and Precision

Precision concerns how narrowly the data estimate a group difference. For strength, the mean-difference estimate is -1.34 pounds, and its confidence interval runs from -3.873 to 1.193. Because the interval includes zero, the posted result does not distinguish clearly between a negative difference, no difference, and a positive difference under the interval’s analysis assumptions. The estimate is not precise enough to establish the direction of the difference.

In general, a confidence interval gives a range of values compatible with the data and the statistical procedure used. A narrower interval indicates greater precision, while a wider interval indicates more uncertainty. It is not a range that contains every participant’s result, and it does not express the probability that the true effect lies within the particular interval. The confidence level and the procedure used to construct these intervals are not reported in the registry record.

The posted group sizes are 15 participants per arm. Limited enrollment can make estimated differences sensitive to the measurements of individual participants, especially when outcomes vary. The registry gives standard deviations for the group summaries, but does not report individual-level data, missing-data handling, or an analysis that accounts for operative and nonoperative pathways. Those omissions constrain assessment of precision beyond the reported intervals.

The secondary confidence intervals for range of motion and pain score do not include zero, but this does not resolve uncertainty about clinical importance, multiplicity, or the analysis choices. No clinically important difference thresholds are reported. Statistical precision should therefore be considered alongside the outcome definitions and analysis limitations, rather than treated as a standalone judgment about practical relevance.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size estimates are planning illustrations expressed as participants per arm, not total events. They use the observed effect as a reference and show estimates for planning around 100% of that effect, 75% of that effect, and 50% of that effect. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is the stated fraction of the observed effect. The trial’s own original sample-size assumptions are not reported in the registry record.

The 80% power column describes a planning target under which the assumed design would have an 80% chance of detecting the specified effect if that effect were the true one and the assumptions held. The 90% power column represents a higher planning target for that same task. These are design calculations, not statements about the chance that the trial’s finding is true.

Smaller effects require more participants per arm to detect under the stated assumptions, so the estimates rise as the assumed effect decreases from the full observed effect to a smaller fraction. Read the curve as a visual expression of this planning relationship: it connects assumptions about effect size with the number of participants needed. The displayed estimates are illustrations based on the observed effect, not observed power for this trial.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -1.340; pooled standard deviation σ = 3.539.
2. n = 2 × (1.96 + 0.842)² × 3.539² / -1.340² = 109.5, rounded up to 110 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -1.34                      # observed difference in means
sigma <- 3.53941379327142                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(4384120)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 110 (80% power), 147 (90% power)
 75% of observed effect: n per arm = 195 (80% power), 261 (90% power)
 50% of observed effect: n per arm = 439 (80% power), 587 (90% power)
power.t.test: 110.5 
Simulated power at n = 110 per arm: 0.799 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome and three secondary outcomes. When several outcomes are tested, the chance of at least one result appearing notable by chance can rise. Statistical approaches can address this problem by defining a testing hierarchy or adjusting the interpretation of multiple comparisons. A multiplicity plan is not reported in the registry record. The posted secondary p-values are unadjusted, so they should not be read as if multiplicity had been addressed.

The record does not report whether interim analyses were planned or performed, whether outcomes or analysis choices changed, or how missing measurements were handled. It also does not provide participant flow, withdrawal counts, reasons for missingness, or the number contributing to each outcome at each time point. Although each posted group summary lists 15 participants, that does not establish that every randomized participant contributed every measurement or that all participants completed the same follow-up schedule.

The analysis population is not reported in the registry record. It is therefore unclear whether the posted summaries represent all randomized participants, participants who received their assigned rehabilitation, or another analysis set. The record also does not report how participants with operative and nonoperative care were analyzed together, whether any subgroup comparisons were planned, or whether repeated observations were modeled.

These omissions matter because missing measurements and analysis choices can affect both estimated differences and their uncertainty. They also limit readers’ ability to distinguish a planned analysis from an exploratory one. The registry’s termination status is recorded, but a reason for termination is not reported. No conclusion about the cause of termination or its effect on the results can be drawn from the registry record.

15. 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 adverse-event summaries list 15 participants at risk in each rehabilitation group. For serious adverse events, zero events are reported in the BFR group and zero in the group without BFR. The other-adverse-event counts are also zero in each group, and deaths are listed as zero in both groups. No serious adverse-event terms are listed.

These figures describe the events recorded in the registry for the participants at risk; they do not establish that the treatments have no safety risks. The groups are small, and the record does not provide event definitions, surveillance details, exposure duration, or a narrative explaining how events were collected and assessed. It also does not report whether any events were considered related to rehabilitation. A zero count in this study should therefore be read as no events recorded in these summaries, not as evidence that events cannot occur.

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

The randomized comparison is a useful framework for asking whether rehabilitation with BFR differs from rehabilitation without BFR. The posted strength summaries show group averages and an unadjusted mean difference, with uncertainty that includes no difference. They do not establish that BFR produces greater strength gains, nor do they demonstrate that the two approaches are equivalent. The trial’s stated hypothesis and rationale are not substitutes for the observed evidence.

The registry describes intended interest in faster strength gains, muscle atrophy, fatty infiltration, pain, range of motion, and patient-reported outcomes. The available results do not address all of those aims. In particular, strength is posted as a summary through study completion, not as a reported comparison of change at every time point. Results for muscle atrophy and fatty infiltration are not reported in the registry record, and the listed patient-reported outcome results are also not reported. The posted data therefore cannot answer every question the study set out to examine.

Nor can the pooled summaries determine whether outcomes differ between participants treated nonoperatively and those undergoing surgery. The registry includes both pathways but does not report their group sizes or separate outcome results. The timeframe is described as an average of 12 months post-operative follow-up, and its application to nonoperative participants is not explained.

Statistical significance, even when suggested by an unadjusted secondary comparison, does not by itself establish clinical importance. The record does not give clinically important thresholds or enough information about scale interpretation to judge the practical meaning of those differences. The terminated status, limited enrollment, lack of reported analysis details, and uncertainty about missing data further constrain conclusions. The most defensible reading is a description of the posted group summaries and their uncertainty, not a definitive judgment about benefit or lack of benefit.

17. Why This Trial Matters Statistically

This trial is statistically instructive because the central question concerns a rehabilitation strategy tested in two groups, while the registry includes both operative and nonoperative treatment pathways. That structure makes the overall group contrast difficult to interpret without information about pathway allocation, follow-up, and whether the outcomes were analyzed separately. A single average can conceal variation across clinically distinct pathways.

The primary strength result also illustrates why the point estimate, confidence interval, and p-value need to be read together. The estimate gives the direction and size of the posted contrast, while the interval communicates uncertainty. The interval includes zero, so the result does not establish a clear direction of difference. This is not the same as evidence that the approaches are equivalent.

The secondary outcomes illustrate a further issue: several measures can be assessed, and unadjusted findings may be more vulnerable to chance patterns when no multiplicity strategy is reported. Different outcomes may also use scales with different meanings, so numerical differences cannot be combined into one overall conclusion without a prespecified approach.

Finally, the enrollment and termination status matter to interpretation. The available sample-size calculations are planning illustrations based on the observed effect, not documentation of the trial’s original design rationale. Missing details about analysis populations, repeated measures, and missing data prevent a full assessment of how the posted summaries were generated. The case shows why transparent reporting of estimands, follow-up, analysis decisions, and participant flow is essential alongside outcome numbers.

18. 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.

Several limitations are specific to the available record. Enrollment was 30, with 15 participants in each posted group summary, and the study status is TERMINATED. A reason for termination is not reported in the registry record. Small group summaries can provide imprecise estimates, as reflected in the confidence interval for strength, and the record does not report a clinically important threshold for interpreting the size of a difference.

Both operative and nonoperative treatment pathways are included, but their participant counts and separate results are not reported. The timeframe refers to an average of 12 months post-operative follow-up, without explaining how it applies to nonoperative participants. The primary result is not reported by measurement occasion, and the record does not clarify whether it summarizes a single time point or measurements across follow-up.

Analysis details are limited. The statistical model, analysis population, missing-data approach, interim analyses, and multiplicity strategy are not reported in the registry record. Participant flow and outcome-specific follow-up counts are also not reported. These gaps limit assessment of potential bias and of whether the posted group summaries include all randomized participants.

Results are not reported for the listed Patient Reported Outcomes Measurement Information System outcome or for the registry’s stated interests in muscle atrophy and fatty infiltration. No adverse events are recorded in the posted safety summaries, but the record lacks event-collection details. These limitations restrict interpretation of both the effectiveness questions and the safety summaries.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: BFR Therapy in Patients With Rotator Cuff Tears — NCT04384120.
• Registry record last updated 2025-06-05; status last verified 2025-06.
• Results first posted 2025-06-05.
• 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.

22. Record Summary

NCT04384120 is a randomized, double-masked, parallel-group trial of rehabilitation with or without blood flow restriction in people with rotator cuff tears planning operative or nonoperative care. The registry lists enrollment of 30, a start date of 2020-06-01, primary completion on 2022-05-01, and status TERMINATED. A reason for termination is not reported in the registry record.

The primary outcome is dynamometer-measured strength in pounds, with follow-up described as through study completion and an average of 12 months post-operative follow-up. The posted summaries include 15 participants per group. The strength comparison is imprecise and does not establish a clear group difference. Secondary summaries are available for range of motion and pain score; patient-reported outcome results are not reported in the registry record. Analysis plans, handling of missing data, and the original sample-size justification are also not reported.