Comparison of Three Methods for Anterior Cruciate Ligament Reconstruction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Three Methods for Anterior Cruciate Ligament Reconstruction (NCT00529958), a randomized na study. The primary outcome is Anterior Cruciate Ligament Quality of Life (ACL-QOL) Outcome.

2. Clinical Question

The clinical question is comparative: among participants undergoing anterior cruciate ligament reconstruction, how do patient-reported quality-of-life outcomes vary by graft procedure? The trial also listed other outcomes, including graft failures, knee examination grades, activity level, kneeling pain and knee laxity. Those measures broaden the clinical assessment, but the stated primary endpoint is the ACL-QOL outcome. The registry record does not provide enough outcome data to determine the direction or size of any between-group difference.

3. Trial Design

The registry describes a randomized, double-masked, parallel-group clinical trial sponsored by the University of Calgary. The study is listed as completed, with an enrollment of 330. It began in 2007-09, and its primary completion was in 2010-12. The record lists the phase as NA.

Participants were assigned to one of three surgical approaches: patellar tendon autograft, quadruple-strand semitendinosus/gracilis hamstring single-bundle autograft, or semitendinosus/gracilis hamstring double-bundle autograft. The registry states that 110 participants were randomized to each group. The trial is described as double-masked, but which participants, clinicians or assessors were masked is not reported in the registry record. Details of the allocation sequence and concealment are also not reported in the registry record.

The primary outcome was ACL-QOL, assessed at baseline and at 3 and 6 months, 1, 2 and 5 years post-operatively. The record says outcome data were not collected for all participants at 1- and 2-year follow-up because of loss-to-follow-up, withdrawal or missed study visits. It does not describe the number of missing observations at each time point or the methods used to handle them.

The registry lists 13 outcome measures and one analysis. The outcome list includes several types of measures, such as scores, clinical grades, failures and activity outcomes. The record does not provide a complete statistical analysis plan or the results of the primary comparison. Therefore, the trial design can be described, but its comparative primary outcome findings cannot be reconstructed from 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.

2-Year Follow-up

Reasons for not completing this period:

5-Year Follow-up

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: There were 110 participants randomized to each study group. At 1- and 2-year follow-up, outcome data was not collected for all participants due to loss-to-follow-up, withdrawal or missed study visits.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: N=110 patients were randomized to each study group. One cross-over from the DB group received an HT graft, but was analyzed as part of the DB study group.

6. Primary Endpoint

The registry lists the primary outcome as Anterior Cruciate Ligament Quality of Life (ACL-QOL) Outcome, measured over Baseline, 3 and 6 months, 1, 2, and 5 years post-operatively.

The primary endpoint was the Anterior Cruciate Ligament Quality-of-Life (ACL-QOL) outcome. It is a patient-reported questionnaire with 32 items covering symptoms and physical complaints, work-related concerns, sports and recreation, lifestyle, and social and emotional concerns. The registry describes the score on a 0 to 100mm visual analog scale, with higher scores representing better quality of life.

Patient-reported quality of life is used to capture aspects of recovery that may not be represented by examination findings alone. It can reflect how symptoms and knee function affect everyday activities and concerns that matter to participants. The ACL-QOL score therefore addresses the trial’s stated aim of comparing quality of life after the three reconstruction procedures.

The score was scheduled for assessment at baseline and at 3 and 6 months, 1, 2 and 5 years post-operatively. Repeated assessment can describe how scores change over follow-up, but a comparative interpretation requires the actual group results and a defined analysis. The registry record does not report the group means, standard deviations, confidence intervals or a test of the primary outcome. It also does not identify a single follow-up time point as the sole primary comparison. Without those details, the endpoint’s measurement and schedule are clear, but the trial’s observed quality-of-life results are not.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies ACL-QOL as a continuous outcome summarized by a mean and standard deviation. Those statistics describe different features of a group’s scores: the mean indicates its average score, while the standard deviation describes how spread out individual scores are around that average. The record does not give the group means or standard deviations, so neither the average scores nor their variability can be compared from the posted results.

What would a group difference describe?

In a randomized trial, a comparison of outcome scores between assigned groups is intended to estimate how the outcome differs across the randomized procedures. The meaning of that estimate depends on the analysis definition. For a repeated outcome, investigators might compare scores at a specified visit, compare change from baseline, or model scores across visits. These are general examples, not descriptions of the analysis used in this trial. The registry record does not report the primary comparison’s definition or estimate.

How should uncertainty be read?

In general, a confidence interval expresses uncertainty around an estimated effect. A narrower interval indicates greater precision under the model and assumptions used; a wider interval indicates less precision. It is not a guarantee that the true effect lies within the interval. The registry record does not report a confidence interval for ACL-QOL, so the precision of any between-group estimate cannot be assessed.

A p-value, in general, measures how incompatible the observed data are with a specified null hypothesis under the statistical model. It does not measure the size or clinical importance of an effect. No primary ACL-QOL p-value is reported in the registry record. A non-significant result, if one had been reported, would not by itself demonstrate equivalence; an equivalence or non-inferiority interpretation requires a suitable design and prespecified margins, which are not reported in the registry record.

Why can repeated measurements matter?

Scores from the same participant across visits are related rather than independent observations. General methods for repeated measurements account for that within-participant relationship and can use information across visits. Their assumptions and handling of incomplete follow-up affect the estimate and its uncertainty. The registry identifies several assessment times, but the statistical model, covariance structure, baseline adjustment and method of handling incomplete repeated measures are not reported in the registry record.

What does the planning illustration represent?

The record describes a planning illustration based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation. The effect to detect is defined as a stated fraction of the observed effect. For continuous outcomes, the planning quantities are participants per arm for 80% power or 90% power. Such values are planning illustrations, not observed power and not evidence about the reliability of the trial’s result. They do not establish the trial’s original sample-size rationale: that rationale is not reported in the registry record. The record does not give a result for the primary outcome from which to judge its precision.

In general, a planning calculation estimates the sample size needed to detect an effect under chosen assumptions. It does not show the probability that a particular observed result is true. Nor does a calculation based on an observed effect substitute for a prespecified design calculation, because the observed effect is itself uncertain. The displayed planning approach is described as an illustration rather than the trial’s own design method.

What can be inferred from the available analysis information?

The registry lists one analysis, but does not provide its estimate, test statistic, confidence interval, p-value, adjustment variables or detailed model specification. The number of listed analyses alone does not establish how all outcome measures and follow-up times were analyzed. Statistical procedures beyond the stated planning illustration are not reported in the registry record. The appropriate interpretation is therefore limited to the study’s stated randomized design, specified outcome measure and follow-up schedule—not a reconstructed analysis or an inferred result.

10. Multiplicity, Missing Data and Analysis Populations

The trial assessed more than one outcome: the registry lists 13 outcome measures. The primary ACL-QOL score was scheduled at baseline and multiple post-operative follow-up points, while secondary outcomes included scores, grades, failure outcomes and activity measures. Considering several outcomes or time points can increase the chance of at least one apparently unusual result when many statistical tests are performed. General approaches to multiplicity include designating a primary contrast, adjusting for multiple tests, or interpreting secondary comparisons as exploratory. Which approach, if any, was prespecified or used is not reported in the registry record.

The registry lists one analysis, but does not give enough detail to determine whether that entry represents a single primary analysis, a summary of analyses, or a particular comparison. It does not report an adjustment for multiple comparisons, a testing hierarchy, interim analyses or stopping rules. These details should not be inferred from the number of listed analyses.

Outcome data were not collected for all participants at 1- and 2-year follow-up, with loss-to-follow-up, withdrawal or missed study visits named as reasons. The registry does not report the number of missing observations at those visits, whether missingness differed among groups, or whether all randomized participants were included in each analysis. Methods such as complete-case analysis, imputation or likelihood-based modeling are not identified. The analysis population and handling of withdrawals are also not reported in the registry record.

Because missing-data methods rely on assumptions about why measurements are absent, incomplete follow-up can affect both the estimated group difference and its uncertainty. This is a general statistical concern, not a claim that a particular bias occurred in this trial. With the available information, the extent and impact of missing data cannot be quantified.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: septic arthritis (0.9%), massive pulmonary embolism (0.9%), deep vein thrombosis (0.9%).

The registry reports serious adverse event counts of 0 for the Patellar Tendon (PT) group, 1 for the Hamstring (HT) group and 2 for the Double-Bundle (DB) group. Each group lists 110 participants at risk. The record also lists other adverse event counts of 20, 22 and 38 for PT, HT and DB, respectively, with 110 at risk in each group. No deaths are listed in any of the three groups.

These figures are descriptive counts. They do not, on their own, establish that the procedures caused the events or that one procedure has a higher risk. A comparative safety interpretation would require information about event definitions, timing, severity, relatedness, completeness of collection and the statistical comparison. Those details are not reported in the registry record. The record does not state whether an individual could contribute more than one event to the other-adverse-event counts, so those counts should not be interpreted as a count of unique participants without further information.

The listed serious-event terms are Septic Arthritis, Massive Pulmonary Embolism and Deep Vein Thrombosis, each reported as 0.9%. The record does not specify the group assignment for those terms. The percentages should therefore not be used to infer a group-specific rate or to reconcile the event terms with the group counts. Adverse-event information gives safety context, but it does not replace the missing primary outcome results.

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

The trial’s stated purpose was to compare quality-of-life outcomes after three anterior cruciate ligament reconstruction methods. Its design is randomized, parallel-group and double-masked according to the registry. It enrolled 330 participants, with 110 randomized to each group. The primary endpoint and its follow-up schedule are described, and the record lists a range of secondary clinical and activity outcomes.

What the posted results do not establish is whether ACL-QOL scores differed between the groups, how large any difference was, or how precise an estimate might be. The registry record does not report group scores, a contrast, a confidence interval or a primary-outcome test. This absence is not evidence of no difference. It means the comparative result cannot be evaluated from the registry record.

Even if a numerical difference were available, its interpretation would depend on the scale, uncertainty, analysis population, missing-data handling and clinical context. Statistical evidence and clinical importance are related but distinct: a small effect can be estimated precisely, while a larger-looking estimate can remain uncertain. The record does not provide an effect estimate or a threshold for a meaningful ACL-QOL difference, so neither question can be resolved.

The listed safety counts are also descriptive rather than causal. They identify serious and other adverse events recorded by group, but the record does not supply enough detail to determine comparative risk or attribution. Similarly, listing secondary outcomes does not mean that a statistically reliable difference was found for any of them.

The defensible conclusion is narrow: the registry describes a randomized three-procedure trial with a patient-reported quality-of-life primary outcome and incomplete data collection for some participants at 1- and 2-year follow-up. It does not report the numerical primary results or sufficient analysis details for a comparative effectiveness conclusion. No treatment recommendation follows from this record alone.

13. Why This Trial Matters Statistically

This trial is statistically notable for comparing three active surgical approaches while measuring a patient-reported outcome over several follow-up times. That structure raises familiar questions about how to define the primary contrast, account for repeated measurements and interpret multiple outcomes. These are important design and analysis issues even when the registry does not supply the results needed to answer them.

The ACL-QOL measure also illustrates why patient-reported outcomes can complement clinical examination measures. A questionnaire can capture symptoms and concerns across work, recreation, lifestyle and social or emotional experience, while other listed outcomes assess clinical grades, laxity, failures or activity. These measures address different dimensions and should not be treated as interchangeable.

Follow-up completeness matters to interpretation. The record specifically notes that not all participants had outcome data at 1- and 2-year follow-up, due to loss-to-follow-up, withdrawal or missed visits. Without counts of missing observations and a description of the analysis population, readers cannot determine how much information contributed to those follow-up comparisons or how missingness was handled.

Finally, the registry distinguishes the study’s design from the evidence needed to interpret its findings. Randomization and equal group allocation describe how participants entered the study groups; they do not themselves reveal the outcome differences. The record’s planning illustration is not a substitute for reported estimates and uncertainty. This case therefore highlights a basic principle of clinical trial reporting: a clear question and design are essential, but readers also need outcome estimates, uncertainty, analysis details and missing-data information to assess the evidence.

14. Limitations

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

The most important limitation for interpreting this registry record is that it does not report numerical results for the primary ACL-QOL outcome. There are no group means, standard deviations, between-group estimates, confidence intervals or p-values in the record. As a result, the primary comparative question cannot be answered from the posted results.

The outcome was scheduled at several time points, but the record does not state which time point or contrast defined the principal analysis. It also does not describe whether the analysis compared follow-up scores, change from baseline or longitudinal patterns. The statistical model and any adjustment for baseline score or other variables are not reported in the registry record.

Incomplete outcome collection is noted at 1- and 2-year follow-up, but the number of missing observations and their distribution across study groups are not reported. The record does not explain how missing data were handled or define the analysis population. These omissions limit assessment of potential bias and precision.

Further design details are also absent, including eligibility criteria beyond the broad conditions listed, the specific parties masked, allocation concealment, and the original sample-size justification. The record does not describe a multiplicity strategy for the listed outcome measures or the repeated assessment times. These omissions should not be filled by assumptions about standard practice.

For safety, event counts are listed, but event definitions, timing, relatedness and group-specific details for the named serious-event terms are not reported. The registry information supports a description of recorded counts, not a complete comparative safety analysis. These limitations concern what can be concluded from the registry record; they do not establish that the trial itself lacked additional methods or results outside that record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Comparison of Three Methods for Anterior Cruciate Ligament Reconstruction — NCT00529958.
• Registry record last updated 2024-12-11; status last verified 2024-11.
• Results first posted 2019-02-20.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry record describes NCT00529958, a completed randomized, double-masked, parallel-group trial sponsored by the University of Calgary. Enrollment was 330, with 110 participants randomized to each of three anterior cruciate ligament reconstruction methods: patellar tendon autograft, quadruple-strand hamstring single-bundle autograft and hamstring double-bundle autograft.

The primary outcome was ACL-QOL, a patient-reported score on a 0 to 100mm scale, assessed from baseline through 5 years post-operatively. The record notes incomplete outcome collection at 1- and 2-year follow-up. It lists 13 outcome measures and provides descriptive adverse-event counts, but does not report the primary outcome results, a comparative estimate or its uncertainty. Accordingly, the registry record describes the trial question and design but does not establish how the three groups compared on quality of life.