This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Rotator Cuff Repair Using Standard Double Row Technique With Platelet Rich Fibrin Membrane vs. Standard Double Row Technique (NCT02256891), a randomized phase 4 study. The primary outcome is Return to Function.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02256891 |
| Phase | Phase 4 |
| Condition | Rotator Cuff Tear |
| Allocation | Randomized |
| Design model | Single Group |
| Masking | Single |
| Enrollment | 97 |
| Arms in the primary outcome | 2 |
| Lead sponsor | HealthPartners Institute |
| Results posted | Yes |
2. Clinical Question
Population
The registry describes people with rotator cuff tear undergoing arthroscopic rotator cuff repair. The study enrolled 97 participants. For the baseline primary measure, results are posted for 44 participants in the Double Row group and 32 in the Double Row With PRFM group. These baseline analysis counts do not represent the total enrollment, and the registry notes that more participants completed a baseline measure than completed the entire study.
Intervention
The intervention of interest combined standard double-row repair, using medial and laterally based anchor fixation, with platelet-rich fibrin membrane (PRFM). The registry lists PRFM as a device and describes the study as comparing this approach with the standard double-row technique. The intervention description does not establish what was used in each specific operation beyond the assigned technique.
Comparator
The comparison group received standard double-row repair using medial and laterally based anchor fixation without the PRFM addition. The registry identifies the study as randomized and single-blind. It does not report who was blinded, how allocation was concealed, or the details of the randomization procedure.
Primary question
The registered primary measure is Return to Function, defined as the Western Ontario Rotator Cuff Index total score at baseline. The study summary describes intended outcomes at 6 months and 2 years and states the hypothesis that participants receiving PRFM would report a higher quality of life. However, the posted primary result is explicitly at baseline. It therefore describes the groups’ starting scores, not a later response to surgery or a change attributable to PRFM. The registry record does not report a posted primary comparison at 6 months or 2 years.
3. Trial Design
The registry describes a randomized, single-blind study of arthroscopic rotator cuff repair. The planned comparison was standard double-row repair alone versus standard double-row repair with platelet-rich fibrin membrane. The study is listed as Phase 4, and HealthPartners Institute is identified as the sponsor. The record lists enrollment of 97 and status as completed. The recorded start is 2011-07 and primary completion is 2015-12.
Randomization means that assignment to the two techniques was intended to occur by chance, rather than being chosen solely by the participant or clinician. In general, random allocation can help balance known and unknown baseline characteristics across groups. That design feature does not by itself show that the groups were balanced on every measure, nor does it establish how assignment was generated or concealed. Those implementation details are not reported in the registry record.
The record describes the study as single-blind, but it does not identify who was masked or explain how masking was maintained. The official title calls it a randomized blinded outcomes study. The registry also lists a single-group model while describing two intervention arms and a randomized comparison. Those entries do not align on their face; the record does not explain the model designation.
The study summary refers to outcomes at 6 months and 2 years. The registered primary measure posted for analysis is instead labeled Baseline. Its results include 44 participants in the Double Row group and 32 in the Double Row With PRFM group. The registry notes that more participants completed a baseline measure than completed the entire study. The record does not report the allocation counts by arm for all 97 enrolled participants or a participant-flow account that would resolve the baseline analysis counts against the overall enrollment.
There are 10 outcome measures listed in the record, but no secondary outcome results are posted in the registry record, and the count of posted analyses is 0. The original statistical analysis plan, the study’s sample-size justification, interim analyses, and the trial’s own design assumptions are not reported in the registry record. The planning illustrations associated with the observed comparison are not evidence of the design used when the trial was planned.
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
| Stage | Double Row | Double Row With PRFM |
|---|---|---|
| STARTED | 55 | 42 |
| COMPLETED | 43 | 29 |
| NOT COMPLETED | 12 | 13 |
Reasons for not completing this period:
| Reason | Double Row | Double Row With PRFM |
|---|---|---|
| Death | 0 | 2 |
| Lost to Follow-up | 0 | 3 |
| Physician Decision | 7 | 3 |
| Screen Fail | 5 | 4 |
| Equipment Malfunction | 0 | 1 |
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.
| Characteristic | Unit | Double Row Only | Double Row With PRFM | Total |
|---|---|---|---|---|
| Participants analysed | 55 | 42 | 97 | |
| Age, Continuous | years | 53.00 (34 to 73) | 58.64 (42 to 75) | 56.15 (34 to 75) |
| Sex: Female, Male: Female | Participants | 24 | 15 | 39 |
| Sex: Female, Male: Male | Participants | 31 | 27 | 58 |
| Region of Enrollment: United States | participants | 55 | 42 | 97 |
6. Primary Endpoint
The registry lists the primary outcome as Return to Function, measured over Baseline.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary measure is titled Return to Function and is the Western Ontario Rotator Cuff Index total score, recorded in units on a scale. The measure is reported as a mean with standard deviation. The registry describes a possible score range of 0-2100 and states that 0 is the best score. It does not further explain the endpoint title or how the total score was interpreted in the study’s analysis.
In general, a patient-reported measure can capture how participants describe their symptoms, function, or quality of life, rather than relying only on an examination or imaging result. A scale with a defined direction can make group summaries interpretable: for this measure, the registry identifies 0 as best, so the numerical direction should be kept in mind when reading the group means. The index is relevant to the study’s stated interest in function and quality of life.
The primary measure’s recorded timeframe is Baseline. That timing is central to interpretation: a baseline mean describes scores before the later outcomes described in the study summary. It is not a measure of improvement after surgery, and a difference between baseline group means cannot by itself establish a treatment effect. The registry’s description says that more participants completed a baseline measure than completed the entire study, which also means the baseline analysis counts should not be mistaken for the number who completed follow-up.
The registry record does not report a primary result at the stated 6-month or 2-year follow-up timeframes. It also does not report a clinically important difference threshold for the index. Without those details, the posted baseline estimates can be described statistically, but their clinical importance or relationship to later recovery cannot be determined from this result.
7. Results Posted in the Registry
- Double Row With PRFM: mean 1,106 versus 1,257 on control; difference -151.14 (95% CI -330.89 to 28.61), standardized effect d = -0.38; z-test p = 0.099.
Mean difference: Double Row With PRFM
95% CI: -330.89 to 28.61
Recalculated from the posted summary statistics
8. Statistical Interpretation
The baseline mean Western Ontario Rotator Cuff Index score was 1257.0 (standard deviation 396.1; 44 participants) in the Double Row group and 1106.0 (standard deviation 393.8; 32 participants) in the Double Row With PRFM group. The registry’s comparison is a mean difference of -151.1, expressed as PRFM minus Double Row. Because 0 is identified as the best score, the PRFM group’s posted baseline mean is numerically closer to that end of the scale. This is a description of the starting scores, not evidence that PRFM changed function.
The reported confidence interval for the mean difference extends from -330.9 to 28.61. It includes zero, so the range of values compatible with the interval includes no difference as well as differences in either direction. The unadjusted p-value is 0.099. These statistics describe uncertainty around the baseline contrast; neither turns a baseline comparison into a later treatment-effect estimate. The registry record does not state the trial’s own decision threshold or identify an adjusted analysis for this result.
The reported standard deviations, 396.1 and 393.8, indicate substantial variation in baseline scores within each group relative to the separation between the posted means. The interval is also wide enough to include a positive difference, despite the negative point estimate. It is therefore more informative to consider the estimate and interval together than to focus only on the point estimate or p-value. The endpoint direction matters as well: lower scores are toward the stated best value of 0, but no threshold for a clinically important difference is reported.
The study summary describes 6-month and 2-year outcomes, yet the primary result is labeled Baseline. No later primary result is reported in the registry record. Consequently, the posted comparison does not answer whether either technique was associated with better subsequent function, whether scores changed over time, or whether any difference persisted. Those questions require results at the relevant follow-up time and an analysis that compares the groups’ outcomes or changes.
There is also a difference between the enrollment count and the baseline analysis counts: 97 participants were enrolled, while 44 and 32 are analyzed for this measure. The record itself notes that more participants completed baseline than completed the entire study, but it does not give enough detail to reconstruct participant flow or explain the analysis population. The observed baseline data should therefore be read as the results for the participants included in that measure, not as a complete accounting of all enrolled participants.
Overall, the posted result is a baseline group comparison with an uncertain estimated difference. It can describe where the groups began on the scale among those analyzed. It cannot establish postoperative benefit, harm, or comparative effectiveness, and it does not substitute for the follow-up results described in the study summary.
9. Statistical Methods Explained
The reported endpoint is continuous: each participant’s Western Ontario Rotator Cuff Index total score is a numerical measurement, and the registry summarizes it using a mean and standard deviation. For a continuous measure, a group mean describes the average score among participants included in that group’s analysis. A standard deviation describes how dispersed individual scores are around that group mean. It is not the same quantity as the uncertainty in the mean or the uncertainty in a difference between means.
What does the mean difference represent?
The comparison is reported as a mean difference for Double Row With PRFM relative to Double Row. The displayed group means are 1106.0 and 1257.0, and the reported contrast is -151.1. The negative sign indicates that the PRFM group’s mean was lower on the score scale at baseline. Since the registry identifies 0 as the best score, the direction can be described in terms of the scale; it should not be treated as an effect of the intervention because the measurement was taken at baseline.
In general, a mean difference puts a contrast between two group averages into the original units of the measure. That makes it possible to relate the estimate to the scale, provided the scale’s interpretation is known. It does not by itself tell whether the contrast is clinically important. The registry record does not report a threshold for a meaningful difference on this index.
Why report standard deviations?
The standard deviations are 396.1 for Double Row and 393.8 for Double Row With PRFM. In general, standard deviations give information about the spread of participant scores within groups. When participant measurements vary considerably, a group mean can be estimated less precisely than when measurements are tightly clustered, all else being equal. The standard deviation is descriptive of individual variation; the confidence interval for the mean difference addresses uncertainty in the contrast.
In general, over-dispersion refers to variation greater than a model assumes. If a model underestimates variability, its standard errors may be too small and its confidence intervals too narrow. The registry’s primary result is presented as a mean and standard deviation, with a mean-difference confidence interval; the record does not describe a model-based over-dispersion assessment. This general issue should not be confused with a claim that over-dispersion was present in this study.
How should the confidence interval and p-value be read?
A confidence interval gives a range of estimates that are compatible with the observed data under the method’s assumptions. In general, a wider interval indicates less precision than a narrower interval. The posted interval for the baseline difference is -330.9 to 28.61, and it includes zero. Zero represents no difference between the two group means on the contrast scale. The interval therefore does not rule out no difference and also spans estimates on either side of zero.
The unadjusted p-value is 0.099. In general, a p-value measures how unusual data at least this discordant with a specified null hypothesis would be if that null hypothesis and the analysis assumptions held. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of a difference. The registry does not report the trial’s planned significance threshold or a complete analysis plan. The p-value is explicitly unadjusted, and the record does not state what adjustments, if any, were planned for multiple comparisons.
What can randomization contribute?
In general, random assignment is intended to make treatment groups comparable in expectation, reducing systematic differences in the factors that influence assignment. With finite groups, baseline differences can still occur by chance. A randomized design is useful for estimating comparative effects when outcomes are measured after assignment and analyzed appropriately. Here, the primary result is at baseline, so it describes the groups’ starting values rather than an effect of the assigned procedure.
The registry identifies the design as randomized and single-blind but does not report the random sequence method, allocation concealment, who was blinded, or whether the reported comparison was adjusted for baseline or other variables. No adjusted estimate is posted. Those details cannot be inferred from the label randomized alone.
What does the sample-size illustration estimate?
The planning illustration uses the observed effect and gives participant counts per arm under stated assumptions. It is not the trial’s original sample-size justification, which is not reported in the registry record. In general, such calculations ask how many participants would be needed to detect a chosen effect size with a specified power and significance level, under the assumed design and statistical approximation. They do not establish what the study actually planned or what power it had after enrollment.
The illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is set to a stated fraction of the observed effect. For a continuous measure, the figures are participants per arm, not total events. The assumed fractions and participant counts are planning scenarios rather than observed outcomes. Smaller effects generally require more participants to detect under otherwise unchanged assumptions. The assumptions and counts should be considered as planning examples only.
What analysis details remain unknown?
The registry reports 10 outcome measures and 0 posted analyses, alongside the baseline primary result. It lists 0 secondary results as posted. It does not report the full statistical analysis plan, the treatment of missing outcome data, any prespecified covariate adjustments, interim analyses, or the method used to address multiplicity. The record also does not identify an intention-to-treat, per-protocol, or other analysis population. These omissions limit assessment of whether the posted result follows a prespecified plan and how it relates to all randomized participants.
10. Confidence Intervals and Precision
The point estimate for the baseline mean difference is -151.1, with a 95% confidence interval from -330.9 to 28.61. The interval is the main summary of statistical precision: it shows that estimates compatible with the analysis range from a negative contrast to a positive one, including zero. The data therefore do not pin down the direction of the baseline difference with high precision.
In general, a confidence interval combines an estimate with its uncertainty under the statistical method used. A narrow interval indicates greater precision than a wide interval, while a wide interval leaves more possible values compatible with the data. An interval that includes zero does not prove that the true difference is zero. Nor does an interval excluding zero, by itself, establish clinical importance. Interpretation also depends on the scale, the timing of measurement, and the size of difference that would matter; a clinically important threshold is not reported for this endpoint.
The group means are based on 44 participants for Double Row and 32 for Double Row With PRFM. The corresponding standard deviations are 396.1 and 393.8, indicating meaningful variation among the recorded scores. Both the amount of variation and the number of participants contribute to precision. The interval should not be read as a range containing most individual participants’ scores; it concerns uncertainty in the group contrast.
Most importantly, this interval concerns a baseline comparison. Its precision does not answer how precisely a later treatment effect was estimated. The registry record does not report a primary estimate and confidence interval for the 6-month or 2-year outcomes described in the study summary. The baseline confidence interval cannot be used as a substitute for those follow-up results.
11. 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.
| Effect to detect | Participants per arm, 80% power | Participants per arm, 90% power |
|---|---|---|
| 100% of the observed effect | 108 | 144 |
| 75% of the observed effect | 191 | 256 |
| 50% of the observed effect | 430 | 575 |
The planning figures are participants per arm, not total events. The registry’s 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 specified as a fraction of the observed effect. These calculations are planning illustrations based on the observed comparison; the trial’s own original design assumptions and sample-size justification are not reported in the registry record.
The 80% power column gives the estimated participants per arm under the stated assumptions for a planning scenario designed to have an 80% chance of detecting the chosen effect if that effect were the true one. The 90% power column gives the corresponding planning count for a 90% chance under the same general assumptions. In general, higher target power requires more participants when the other assumptions are held fixed. These are not observed power.
The scenarios are labeled as planning for 100%, 75%, and 50% of the observed effect. For planning for 100% of the observed effect, the figures are 108 participants per arm for 80% power and 144 participants per arm for 90% power. For planning for 75% of the observed effect, they are 191 and 256 participants per arm. For planning for 50% of the observed effect, they are 430 and 575 participants per arm. These are hypothetical planning counts, not the numbers enrolled in the trial.
The pattern reflects a general property of sample-size planning: smaller effects are harder to distinguish from random variation, so smaller effects need more participants when the design assumptions are otherwise unchanged. The observed effect can be uncertain, especially when its confidence interval is wide. Using it as the basis for a planning illustration does not mean that the observed estimate is the true effect, nor does it establish that the original study was designed around that estimate.
12. 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 z1−α/2 = 1.960) and the desired power (z1−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
- Observed difference Δ = -151.140; pooled standard deviation σ = 395.112.
- n = 2 × (1.96 + 0.842)2 × 395.1122 / -151.1402 = 107.3, rounded up to 108 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 <- -151.14 # observed difference in means
sigma <- 395.112291105241 # 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(2256891)
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 = 108 (80% power), 144 (90% power)
75% of observed effect: n per arm = 191 (80% power), 256 (90% power)
50% of observed effect: n per arm = 430 (80% power), 575 (90% power)
power.t.test: 108.2
Simulated power at n = 108 per arm: 0.796 (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.
13. Multiplicity, Missing Data and Analysis Populations
The registry lists 10 outcome measures, reports 0 posted secondary outcomes, and records 0 posted analyses. The primary measure discussed in the record is the baseline Western Ontario Rotator Cuff Index score. The study summary describes outcomes at 6 months and 2 years, but the registry result for the primary measure is labeled Baseline. The registry record does not report a posted primary result at either later time point.
Multiplicity arises when multiple outcomes, time points, subgroups, or analyses are tested. In general, the more comparisons that are made, the greater the chance that at least one result appears unusual by chance if each is considered in isolation. Adjustment methods or a prespecified hierarchy can help control interpretation, but the record does not state whether any such approach was planned or used. The unadjusted p-value of 0.099 should therefore be understood as unadjusted; it cannot be assumed to account for all outcomes or analyses.
The registry description notes a discrepancy between the number of participants analyzed for the baseline measure and the participant flow module: more participants completed a baseline measure than completed the entire study. The measure has results for 44 participants in Double Row and 32 in Double Row With PRFM, while total enrollment is 97. The record does not give the full sequence of randomized, treated, followed, and analyzed participants by arm, or explain every reason for missing data.
In general, missing outcomes can affect precision and can also bias a comparison if the chance of having a recorded score is related to participant characteristics or outcomes. The available record does not report a missing-data method, an imputation procedure, or a sensitivity analysis. It also does not identify the analysis population as intention-to-treat, per-protocol, or another defined set. The baseline counts should therefore be interpreted as the participants included in that measure, without assuming that they represent all randomized participants.
The original analysis plan, any planned interim analyses, and the trial’s prespecified multiplicity strategy are not reported in the registry record. Their absence from the record does not establish that the investigators did or did not use particular procedures; it means those procedures cannot be assessed from the posted information.
14. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Double Row | 0 | 55 | 0.0% |
| Double Row With PRFM | 0 | 42 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Double Row | 9 of 55 |
| Double Row With PRFM | 2 of 42 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Double Row | Double Row With PRFM |
|---|---|---|---|
| Pulmonary/Respiratory | Respiratory, thoracic and mediastinal disorders | 4 of 55 | 1 of 42 |
| Musculoskeletal | Musculoskeletal and connective tissue disorders | 2 of 55 | 1 of 42 |
| Oncological | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 0 of 55 | 1 of 42 |
| Optomological | Eye disorders | 1 of 55 | 0 of 42 |
| ENT | Ear and labyrinth disorders | 1 of 55 | 0 of 42 |
| Urinary | Renal and urinary disorders | 1 of 55 | 0 of 42 |
| Dermatological | Skin and subcutaneous tissue disorders | 1 of 55 | 0 of 42 |
| Endocrine | Endocrine disorders | 1 of 55 | 0 of 42 |
| Neurological | Nervous system disorders | 1 of 55 | 0 of 42 |
The registry reports serious adverse events for 0 of 55 participants at risk in the Double Row group and 0 of 42 participants at risk in the Double Row With PRFM group. These are the posted counts and denominators. The serious-event terms list is empty. Death counts are not reported in the registry record.
For other, non-serious adverse events, the record lists 9 of 55 participants at risk in Double Row and 2 of 42 at risk in Double Row With PRFM. These are counts of participants affected as recorded in the registry, not a measure of severity or an estimate of whether an event was caused by the assigned technique. The record does not name the individual non-serious events in the information.
In general, an adverse-event count describes what was recorded during the study and does not by itself establish causality. The at-risk denominators for these safety summaries differ from the baseline measure analysis counts. They should not be substituted for the numbers contributing to the primary score analysis. The registry record does not provide further detail about event definitions, collection procedures, follow-up periods for these safety counts, or how events were judged to be related to treatment.
15. What the Result Does, and Does Not, Mean
The posted primary result describes baseline scores on the Western Ontario Rotator Cuff Index among the participants included in the analysis. The Double Row mean was 1257.0, and the Double Row With PRFM mean was 1106.0. The reported difference, PRFM minus Double Row, was -151.1, with a confidence interval from -330.9 to 28.61 and an unadjusted p-value of 0.099. Since the scale identifies 0 as best, the PRFM group’s mean was numerically closer to that end of the scale at baseline.
That result does not show that PRFM improved function. The endpoint timeframe is Baseline, before the later outcomes described in the study summary. A baseline difference is not an estimate of change after surgery or of the effect of one technique relative to the other. The confidence interval includes zero and spans values on either side, so the estimate is uncertain about the direction of the baseline contrast. The registry does not provide a clinically important difference threshold for judging the size of the contrast.
The study was described as randomized and single-blind, but design labels alone cannot replace outcome results at the relevant follow-up time. The registry record does not report the primary measure results at 6 months or 2 years, nor does it provide a posted analysis of change over time. The stated hypothesis about quality of life is a study aim, not a finding established by the baseline numbers.
The safety counts report no serious adverse events in either group among the listed participants at risk, while other adverse events are recorded for 9 of 55 in Double Row and 2 of 42 in Double Row With PRFM. Those descriptive counts do not establish causality, and the registry does not report deaths or name the serious-event terms. They should not be interpreted as a complete assessment of the comparative safety of the procedures.
Overall, the registry supports a description of the baseline score comparison and the posted adverse-event counts. It does not support a conclusion about whether either technique improves later function, quality of life, or safety relative to the other. Those conclusions would require the relevant follow-up results and sufficient information about participant flow and analysis methods.
16. Why This Trial Matters Statistically
This trial illustrates why endpoint timing is as important as endpoint choice. The study summary focuses on outcomes at 6 months and 2 years, while the posted primary measure is labeled Baseline. A numerical contrast on a patient-reported scale can look like a treatment comparison if timing is overlooked, even though baseline results describe the starting groups rather than their response to treatment. Reading the timeframe carefully prevents a descriptive comparison from being mistaken for a treatment-effect estimate.
The result also demonstrates why estimates and uncertainty should be read together. The mean difference is -151.1, but the confidence interval ranges from -330.9 to 28.61. The estimate is therefore compatible with a range of baseline contrasts, including zero. The unadjusted p-value of 0.099 is another summary of the data under a statistical test; it does not identify the probability that a treatment works or resolve the question of clinical importance.
The scale’s direction matters for interpretation. The registry identifies 0 as the best score, so a lower score is numerically nearer that stated endpoint of the scale. But direction alone is not enough to identify a meaningful difference, and the record does not report a threshold for clinical importance. Statistical interpretation needs the measurement definition, group summaries, uncertainty, and timeframe together.
Finally, the record separates enrollment from the number contributing to the baseline result and notes that baseline completion exceeded completion of the entire study. This makes participant flow and missing-outcome methods important context. The registry does not report enough detail to identify the analysis population or assess how missing data were handled. The example reinforces that a trial’s title, design, and hypothesis cannot stand in for posted outcome estimates at the prespecified follow-up time.
17. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The main limitation for interpreting the primary result is that its timeframe is Baseline. Although the study summary describes outcomes at 6 months and 2 years, the registry record does not report the primary outcome results at those times. As a result, the posted baseline comparison does not answer the main longitudinal question suggested by the study summary.
The registry notes that more participants completed a baseline measure than completed the entire study. The baseline analysis includes 44 participants in Double Row and 32 in Double Row With PRFM, compared with total enrollment of 97. The record does not provide enough detail to reconcile these counts with randomization, participant flow, or the number followed at later time points. It does not state whether the primary analysis used all randomized participants or a different population.
The record does not report the trial’s original sample-size justification, full statistical analysis plan, missing-data methods, or any sensitivity analyses. It also does not report a clinically important difference threshold for the Western Ontario Rotator Cuff Index. These omissions limit assessment of whether the observed precision was adequate for the intended question and whether the difference would matter to participants.
Although the registry describes randomization and single blinding, it does not identify who was blinded, explain allocation concealment, or describe the randomization procedure. The listed single-group model designation also sits alongside two described randomized arms, and the record does not explain that discrepancy. These reporting gaps limit assessment of implementation without changing the fact that the record labels the study randomized.
Safety reporting is limited to the listed counts and at-risk denominators. Deaths are not reported, serious-event terms are not listed, and the record does not explain event definitions, ascertainment, or attribution. The posted safety counts are therefore descriptive and do not resolve comparative safety.
18. Related Tutorials
19. Related Statistical Calculators
20. Sources
- ClinicalTrials.gov: Rotator Cuff Repair Using Standard Double Row Technique With Platelet Rich Fibrin Membrane vs. Standard Double Row Technique — NCT02256891.
- Registry record last updated 2017-08-09; status last verified 2015-10.
- Results first posted 2017-08-09.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
21. Record Summary
The registry record describes a completed Phase 4 randomized, single-blind study sponsored by HealthPartners Institute, comparing standard double-row arthroscopic rotator cuff repair with the same technique plus platelet-rich fibrin membrane. It lists 97 enrolled participants and gives the start as 2011-07 and primary completion as 2015-12.
The primary measure is the Western Ontario Rotator Cuff Index total score, labeled Return to Function and recorded at Baseline. The posted means are 1257.0 for Double Row and 1106.0 for Double Row With PRFM. The reported mean difference is -151.1, with a confidence interval from -330.9 to 28.61 and an unadjusted p-value of 0.099. The analysis counts are 44 and 32, respectively.
The registry describes planned outcomes at 6 months and 2 years, but does not report primary results at those timeframes. It notes that more participants completed a baseline measure than completed the entire study. Serious adverse events are listed for 0 of 55 and 0 of 42 participants at risk; other adverse events are listed for 9 of 55 and 2 of 42. Deaths are not reported. The original sample-size justification, full analysis plan, and analysis population are not reported in the registry record.