Evaluation of High-Purity Type I Collagen Biologic Wrap to Improve Function After Extensor Tendon Repair of the Hand: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of High-Purity Type I Collagen Biologic Wrap to Improve Function After Extensor Tendon Repair of the Hand (NCT07335653), a randomized na study. The primary outcome is Total Active Motion (TAM) of Involved Finger(s).

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group trial of a high-purity Type I collagen wrap used with standard extensor tendon repair versus standard repair alone. It lists 60 participants enrolled, with 30 in each arm in the posted primary outcome results. The trial status is completed. The registry lists the phase as NA.

The study concerns extensor tendon injuries of the hand, particularly the risk of adhesions and associated functional impairment. Its brief summary describes the trial as multicentric, but the number and locations of participating centers are not reported in the registry record. The identity of the party or parties masked is also not reported, so single masking cannot be interpreted more specifically.

The registry lists a start date of 2025-12-05 and a primary completion date of 2026-02-21. The primary endpoint is total active motion of the involved finger or fingers, measured in degrees at 8 weeks postoperatively. The posted primary outcome gives the mean and standard deviation in each arm. Secondary outcomes include measures of hand function, tendon lag, adhesions, grip strength, return to work or daily activities, and patient satisfaction.

The original protocol, its sample-size justification, the intended statistical analysis plan, and the definition of analysis populations are not reported in the registry record. The planning illustrations associated with the posted results are based on observed effects and stated assumptions; they should not be read as the trial’s original design rationale.

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 Total Active Motion (TAM) of Involved Finger(s), measured over 8 weeks postoperatively.

Total active motion (TAM) is a measure of the active movement available across the involved finger’s metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints. The registry defines it as the sum of active flexion at those joints minus extension deficits, with the result expressed in degrees. Higher values indicate better functional outcome.

This endpoint is relevant to tendon repair because motion at the joints reflects how well the finger can move after surgery. Adhesions around a repaired tendon can restrict its glide and may contribute to reduced motion; the trial’s stated purpose is to evaluate whether placing a collagen wrap around the repair site can reduce adhesion formation and improve function. TAM therefore gives a quantitative measure of finger movement that can be compared between the randomized groups.

The primary assessment is specified for 8 weeks postoperatively. That timing gives a snapshot of function at an early postoperative follow-up, not a measure of longer-term recovery. The registry record does not report a minimal clinically important difference or a threshold for interpreting a particular TAM change as important to patients. Statistical evidence about a difference in group means should therefore be distinguished from evidence about the practical importance of that difference.

7. Results Posted in the Registry

• Standard Extensor Tendon Repair Alone: mean 201.30 versus 232.40 on control; difference -31.10 (95% CI -43.42 to -18.78), standardized effect d = -1.28; z-test p = <0.001.

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.

Extensor Lag

• 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:
  • Standard Extensor Tendon Repair Alone: mean 15.70 versus 6.40 on control; difference 9.30 (95% CI 6.65 to 11.95), standardized effect d = 1.78; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Standard Extensor Tendon Repair Alone than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Number of Participants With Clinically Significant Tendon Adhesions

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Standard Extensor Tendon Repair Alone: 30.0% (9/30) versus 6.7% (2/30) on control; risk difference 23.3 percentage points (95% CI 4.7 to 42.0), risk ratio 4.50 (1.06–19.11); unadjusted two-proportion z-test p = 0.020.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for Standard Extensor Tendon Repair Alone than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Grip Strength

• 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:
  • Standard Extensor Tendon Repair Alone: mean 63.20 versus 78.60 on control; difference -15.40 (95% CI -20.60 to -10.20), standardized effect d = -1.50; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Standard Extensor Tendon Repair Alone than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The posted secondary results broadly point in the same functional direction as the primary TAM comparison: the wrap-plus-repair arm has better group summaries on the measures with numerical results, while the adhesion counts also favor that arm. This coherence across movement, strength, and adhesion-related outcomes can be viewed as supportive context for the primary finding. It does not make the secondary outcomes independent confirmations, because they arise from the same randomized groups and may be related to one another.

The registry lists six secondary outcomes, but numerical results are posted for only three of them. QuickDASH score, time to return to work or activities of daily living, and patient satisfaction are not reported in the registry record. The absence of posted results for these outcomes means that their findings cannot be assessed from this record; it should not be interpreted as evidence of no effect or as evidence that they were not measured.

The secondary comparisons are unadjusted. When several outcomes are tested, the chance of finding at least one apparently notable result can increase, even if none reflects a true difference. The registry does not report a multiplicity procedure or a hierarchy for interpreting secondary outcomes. Consequently, these findings carry less inferential weight than the designated primary outcome and should be treated as exploratory or supportive rather than as conclusive evidence on their own.

The secondary measures also differ in scale and meaning. Continuous measurements, such as movement or strength, describe group averages, while the adhesion outcome is a participant count. Their estimates should not be treated as interchangeable or combined into a single overall effect. The record does not report a prespecified composite endpoint or an analysis that integrates them.

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

• QuickDASH Score
• Extensor Lag
• Number of Participants With Clinically Significant Tendon Adhesions
• Grip Strength
• Time to Return to Work or Activities of Daily Living
• Patient Satisfaction

9. Statistical Interpretation

10. Statistical Methods Explained

The reported primary outcome is continuous: it is a measurement in degrees, and the registry presents an arithmetic mean and standard deviation for each arm. A comparison of group means estimates the average difference between the assigned groups. In this record, the comparison is expressed as standard repair alone minus HPTC wrap plus standard repair. Keeping the order of the groups clear is essential when reading the sign of the estimate.

What does the confidence interval describe?

A confidence interval describes a range of values that are compatible with the observed data under the statistical model and its assumptions. For the primary outcome, the posted interval is -43.42 to -18.78 degrees for the stated comparison direction. Since the contrast is standard repair alone minus wrap plus repair, a negative value corresponds to a higher mean in the wrap-plus-repair arm. The interval conveys uncertainty in the estimated group contrast; it does not show the range of individual participants’ outcomes, and it does not itself determine whether a difference is clinically important.

How should the p-value be read?

The unadjusted primary p-value is <0.001. A p-value describes how unusual data at least as inconsistent with a specified null hypothesis would be if that hypothesis and the statistical model were true. It is not the probability that the null hypothesis is true, and it is not a measure of the probability that the result occurred by chance in an everyday sense. The posted p-value is unadjusted, so it does not account for testing multiple outcomes or comparisons.

What do the standard deviations add?

The standard deviation describes the spread of participant measurements around the group mean. The primary outcome standard deviations are 21.6 degrees for the wrap-plus-repair arm and 26.8 degrees for standard repair alone. These values describe variability within the arms; they are not uncertainty intervals for the mean difference. A standard error, in contrast, describes uncertainty in an estimated statistic, such as a group mean. The registry record does not report a detailed account of the original analysis method or whether it used any adjustment beyond the posted summary comparison.

What does “unadjusted” imply?

An unadjusted comparison is presented without a reported correction for testing multiple outcomes or without a reported adjustment for other variables. The record does not identify a primary analysis model beyond the outcome summaries and comparisons, so it is not possible to determine from the registry whether additional model-based analyses were conducted. The posted p-values should therefore be understood as unadjusted evidence for the individual comparisons, not as results protected against the chance of false-positive findings across a family of outcomes.

How do effect-size summaries differ from raw-unit results?

The primary outcome is naturally interpreted in degrees, which retains the clinical measurement scale. A standardized effect summary expresses a mean difference relative to variability, which can help describe magnitude on a scale that is less tied to the outcome’s units. It is not a substitute for the raw-unit estimate or its confidence interval, and its interpretation depends on the observed variability. The registry does not report a clinical threshold that would make a particular value on either scale meaningful to patients.

What does the planning illustration represent?

The planning figures are illustrations based on fractions of the observed effect, equal allocation, a two-sided significance level of 0.05, and a normal approximation. They estimate the participants per arm associated with the stated power targets under those assumptions. They are not an account of the trial’s original design process. The registry record does not report the trial’s original sample-size assumptions, and observed effects can be unstable, especially in a trial of this size. The illustration is therefore best read as a conditional planning aid rather than as evidence about the reliability of the trial’s results.

Across all these methods, interpretation depends on the design and conduct as well as the arithmetic. The registry does not report the masking details, allocation concealment, missing-data handling, analysis populations, or a complete prespecified analysis plan. Those omissions constrain how fully the reported estimates can be evaluated.

11. Confidence Intervals and Precision

The primary mean difference is -31.1 degrees for standard repair alone minus HPTC wrap plus repair, with a 95% confidence interval from -43.42 to -18.78. This interval shows the range of values compatible with the observed comparison under the method used to calculate it. Its direction is consistent with a higher average TAM in the wrap-plus-repair arm, while its width reflects uncertainty around the estimated contrast.

The arm means are based on 30 participants in each group, and the reported standard deviations are 21.6 and 26.8 degrees. These measures provide context for the amount of variation in the observed data. The interval does not mean that most participants’ individual differences fall within its limits; it concerns the estimated difference in group means.

Precision is not the same as clinical importance. The registry record does not report a threshold for a meaningful difference in TAM, nor does it provide longer-term primary outcome follow-up. The interval therefore helps assess statistical uncertainty at 8 weeks postoperatively but cannot, by itself, establish the practical value or durability of the observed difference.

The interval also depends on the statistical method and analysis assumptions. Details of the original analysis plan, missing-data methods, and analysis population are not reported in the registry record. The posted interval should be read as precision for the reported comparison, not as a complete account of uncertainty arising from study conduct, measurement, or selective reporting.

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 planning figures are participants per arm, not total participants across both arms. They are calculated for three fractions of the observed effect: 100%, 75%, and 50%. For each assumed effect, the display gives the participants per arm associated with 80% power and with 90% power. The 80% column means that, under the planning assumptions and if the assumed effect were true, a study of that size would have an 80% chance of detecting an effect at the stated significance level. The 90% column represents a higher chance of detection under the same conditions.

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. These are planning illustrations based on the observed results, not the trial’s original design assumptions; those original assumptions are not reported in the registry record. The outcome is not a time-to-event measure, so the figures are participants per arm rather than a total number of events.

Smaller assumed effects require more participants to achieve the same power target. This reflects the greater difficulty of distinguishing a smaller signal from variability in the measurements. The figures are not observed power: they do not measure how much power the completed trial actually had after its results were known. They are conditional estimates for future planning under the stated assumptions, and changing the assumptions or the true effect would change the required sample size.

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 = -31.100; pooled standard deviation σ = 24.339.
2. n = 2 × (1.96 + 0.842)² × 24.339² / -31.100² = 9.6, rounded up to 10 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 <- -31.1                      # observed difference in means
sigma <- 24.3392686825221                     # 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(7335653)
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 = 10 (80% power), 13 (90% power)
 75% of observed effect: n per arm = 18 (80% power), 23 (90% power)
 50% of observed effect: n per arm = 39 (80% power), 52 (90% power)
power.t.test: 10.7 
Simulated power at n = 10 per arm: 0.774 (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 identifies TAM at 8 weeks postoperatively as the primary outcome and lists several secondary outcomes. It does not report a multiplicity adjustment, a hierarchy for testing secondary outcomes, or a complete statistical analysis plan. The posted secondary comparisons are unadjusted. As a result, their p-values do not account for the number of outcomes examined, and they should be interpreted more cautiously than the primary result.

The registry record does not report how missing outcome data were handled, how many participants contributed data to each measure, or whether an intention-to-treat, per-protocol, or other analysis population was used. The arm summaries list 30 participants per group, but that does not establish that every randomized participant had complete data for every endpoint. No missing-data method or sensitivity analysis is reported in the registry record.

Other important analysis details are also not reported: the original statistical analysis plan, the model used for the primary comparison, whether baseline values were considered, and how protocol deviations or changes in assigned treatment were handled. The record does not give details of allocation concealment or specify who was masked. These gaps make it difficult to evaluate the potential effects of analytic choices or study conduct on the posted estimates.

The absence of these details does not establish that a particular method was or was not used. It means the registry record does not allow readers to verify those choices. In particular, the unadjusted results should not be treated as if they were protected from multiplicity or as if missing observations and analysis populations had been fully documented.

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.

Most frequent non-serious adverse event terms

The registry reports serious adverse events for 30 participants at risk in each arm. There were 0 serious adverse events in the HPTC wrap plus standard repair arm and 0 in the standard-repair-alone arm. No deaths were reported in either group.

For other adverse events, 0 participants were affected in the wrap-plus-repair arm and 1 participant was affected in the standard-repair-alone arm, with 30 at risk in each arm. The type and severity of that other adverse event are not reported in the registry record. These counts describe what was posted for the trial; they do not establish that no unreported or unrecorded events occurred.

Safety counts from a trial of this size and follow-up do not, on their own, rule out uncommon events or characterize longer-term safety. The registry record does not provide event-level descriptions, timing, relatedness assessments, or a broader safety analysis. The figures should be read as the reported event counts, not as a complete safety profile.

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

The primary result shows a higher mean total active motion at 8 weeks postoperatively in the HPTC wrap plus standard repair arm than in the standard-repair-alone arm. The posted mean difference and confidence interval indicate a clear separation between the group averages on the measured endpoint. This is evidence about the groups in this trial at the stated follow-up and under the analysis represented by the posted comparison.

The result does not establish that the collagen wrap caused the observed difference through a particular biological mechanism. Although the trial’s rationale concerns adhesions, a difference in TAM does not by itself show that reduced adhesions explain the difference. Nor does a group-average result mean that every participant experienced better motion. Individual outcomes can vary within each arm.

The endpoint is a measure of finger motion, not a complete measure of hand function, return to work, satisfaction, or long-term recovery. The registry record does not report a threshold for clinically important TAM differences, and it does not provide longer-term primary outcome results. The posted comparison therefore cannot establish how durable the group difference is or how it relates to outcomes that matter in daily life.

Randomization supports a comparative interpretation, but important details about trial conduct and analysis are not reported. The record does not describe allocation concealment, who was masked, missing-data handling, or analysis populations. Those limitations should be considered alongside the numerical result. Secondary results offer additional context but are unadjusted and incomplete in the registry record.

In sum, the posted data describe a statistically distinct difference in average TAM at the specified follow-up. They do not, by themselves, establish a treatment recommendation, guarantee an individual outcome, or answer questions about longer-term benefit, practical importance, or outcomes not reported in the registry record.

17. Why This Trial Matters Statistically

This trial illustrates why a clinical result should be read at several levels. The primary endpoint has a direct unit—degrees of active finger motion—and the group means, mean difference, confidence interval, and p-value each answer a different question. The means describe the observed groups, the difference expresses the contrast, the interval conveys uncertainty, and the p-value assesses compatibility with a specified null hypothesis under the comparison method.

It also shows the distinction between a statistical finding and a clinically meaningful one. The primary comparison is statistically persuasive in the posted analysis, but the registry does not report a threshold for a meaningful TAM difference or longer-term outcomes. A small p-value does not replace those questions. Readers need to consider the measured endpoint, follow-up timing, variability, and the uncertainty around the estimate.

The secondary results demonstrate why outcome multiplicity matters. Several functional and adhesion-related measures are of interest, but the registry does not report an adjustment or testing hierarchy. Consistent directions can be informative, yet unadjusted secondary findings should not be treated as equivalent to a prespecified primary result. Outcomes without posted results remain unresolved rather than negative.

Finally, the record shows the limits of registry reporting for evaluating a trial fully. Randomization and balanced posted arm sizes are relevant, but missing details on masking, analysis populations, missing data, and the original statistical plan make it harder to assess risk of bias and reproducibility. Clear interpretation requires both attention to the numerical estimates and recognition of what the registry record does not report.

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.

The primary outcome is assessed at 8 weeks postoperatively, so the posted results do not establish whether the group difference persists at later follow-up. The registry record does not report longer-term TAM results. It also does not provide a clinically important difference threshold, which limits interpretation of the practical significance of the observed contrast.

The trial enrolled 60 participants, with 30 represented in each arm’s primary summary. Estimates from a trial of this size may be sensitive to participant variation, and the confidence interval remains important when considering the range of plausible group differences. The registry record does not report the original sample-size justification, so the adequacy of the planned enrollment for the primary question cannot be evaluated from the registry.

The record describes the study as multicentric but does not identify the number or locations of centers. It specifies single masking without stating who was masked. Details of allocation concealment, treatment adherence, protocol deviations, analysis populations, and missing data are not reported. These omissions limit assessment of how the trial was conducted and how the posted estimates were generated.

Several listed secondary outcomes do not have numerical results in the registry record, and the reported secondary comparisons are unadjusted. The type of the one other adverse event is also not reported. Together, these limits mean the posted findings address a specific early functional endpoint more clearly than they address broader function, durability, or the complete safety picture.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Evaluation of High-Purity Type I Collagen Biologic Wrap to Improve Function After Extensor Tendon Repair of the Hand — NCT07335653.
• Registry record last updated 2026-04-13; status last verified 2026-03.
• Results first posted 2026-04-13.
• 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

The registry describes a completed randomized, single-masked, parallel-group trial comparing high-purity Type I collagen wrap plus standard extensor tendon repair with standard repair alone. It lists 60 participants enrolled and reports primary outcome summaries for 30 participants in each arm. The primary endpoint is mean total active motion of the involved finger or fingers in degrees at 8 weeks postoperatively.

The posted primary comparison favors the wrap-plus-repair arm on average TAM, with an unadjusted p-value of <0.001. Secondary results are available for three outcomes; additional listed secondary outcomes are not reported in the registry record. No serious adverse events or deaths are posted in either arm, and one other adverse event is reported in the standard-repair-alone arm.

The registry does not report the original sample-size rationale, a full statistical analysis plan, missing-data handling, analysis populations, or longer-term primary results. These gaps limit assessment beyond the posted comparison at the specified follow-up.