Bone Tunnel Widening Following ACL Reconstruction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Bone Tunnel Widening Following ACL Reconstruction (NCT00198042), a na na study. The primary outcome is Bone Tunnel Diameter.

2. Clinical Question

3. Trial Design

The registry lists a completed, single-group study of surgical reconstruction of the ACL, with enrollment of 18. The study start is recorded as 2004-06, and primary completion as 2015-12-31. The phase is recorded as NA. Allocation is recorded as NA, and masking as none. These fields describe the registry classification; they do not supply a detailed account of how participants were recruited, treated, or followed.

The listed intervention is a procedure, rather than a drug. Although the brief summary frames hypotheses involving bone-patella tendon-bone, hamstring, and Achilles tendon grafts, the record does not give arm descriptions or define groups for those graft types. Its single-group model and the note that this is not a randomized comparison caution against interpreting the hypotheses as evidence of a controlled, like-for-like comparison. Details of the fixation methods, graft assignment, and whether different graft types were actually represented are not reported in the registry record.

The primary outcome is bone tunnel diameter, a continuous measure expressed in mm, with the mean and standard deviation identified as the outcome format. It is described as measured on MRI, with a timeframe of 2 years. The registry lists 2 outcome measures and 0 analyses. Numerical summaries for the primary outcome, participant flow, and analysis populations are not reported in the registry record.

The sponsor is Hospital for Special Surgery, New York. The record’s hypotheses also address early tunnel widening and pre-operative bone mineral density, but it does not provide enough design or results detail to determine how those questions were assessed. Procedures for follow-up, imaging, and handling deviations 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

Analysis population for the primary outcome, as defined in the registry: MRI measurement of tunnel dimensions.

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 Bone Tunnel Diameter, measured over 2 years.

The primary endpoint is bone tunnel diameter measured on MRI at 2 years, reported in mm. It is a continuous outcome, and the registry identifies the mean and standard deviation as its summary format. The stated population for the measurement is MRI assessment of tunnel dimensions.

In general, a continuous measurement preserves information about the size of an anatomical feature rather than reducing it to categories such as present or absent. A mean describes the central level of measurements across the analyzed observations, while a standard deviation describes how spread out those measurements are around the mean. Both are needed to understand not only the typical measured diameter but also the variability among observations.

Bone tunnel diameter is relevant to the stated research topic because the hypotheses concern tunnel widening after ACL reconstruction. The primary endpoint’s specified timeframe is 2 years; it is distinct from the hypothesis about widening in the early postoperative period, described as occurring before 8 weeks. A measurement at one timeframe does not, by itself, show when a change occurred or how it developed over time.

The registry record does not report the observed mean, standard deviation, number of measurements analyzed, or a comparison of measurements. It therefore does not establish the magnitude or precision of any tunnel diameter result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous primary measure and names the mean and standard deviation as its summary statistics. It does not identify a statistical test, model, adjustment strategy, or confidence interval method. The explanations below are general statistical context, not a description of methods confirmed for this study.

What does a mean describe?

In general, the mean is the arithmetic average of the measurements included in an analysis. It provides a measure of the central level of a continuous outcome. For bone tunnel diameter, a mean would describe the average measured diameter in the analyzed observations at the specified assessment time. The mean alone does not show whether values cluster closely together or vary substantially. The standard deviation conveys that spread, although neither summary reveals the full shape of the measurements or the presence of unusual values.

To interpret a mean clinically or statistically, readers need to know which observations contributed to it, whether measurements were available for all eligible participants, and how missing measurements were handled. Those details are not reported in the registry record. The record also does not report the observed mean or standard deviation, so no numerical interpretation is possible.

Why does the study structure matter?

In general, a between-group comparison requires clearly defined groups and an outcome summary for each group, together with an estimate of the difference and its uncertainty. Random allocation, when used and reported, can help make groups comparable on average, but this record lists allocation as NA and the model as single group. It also notes that this is not a randomized comparison and that arms are not a like-for-like control comparison. The registry does not provide group definitions or results that would support a quantitative graft comparison.

A single-group measurement can describe the observations within that group, but it cannot by itself distinguish a treatment-related change from other explanations. For example, a change over time can be assessed only if the relevant repeated measurements and their analysis are available. A comparison of graft types requires the group-specific data and a suitable analysis. Neither set of results is reported in the registry record.

What would uncertainty convey?

In general, a confidence interval combines an estimate with information about its sampling uncertainty. A narrower interval indicates greater precision under the assumptions of the analysis; a wider interval indicates less precision. The interval does not guarantee that the true value lies within its bounds, and it does not account automatically for bias, measurement error, or problems in study design. No confidence interval is reported for this primary outcome.

A p-value, if reported, would describe how unusual data at least as extreme as those observed would be under a specified null hypothesis and analysis model. It is not the probability that a hypothesis is true, nor does it convey the size or practical importance of an effect. The registry lists 0 analyses and gives no p-value for the outcome. No statistical significance claim can therefore be evaluated.

How should planning calculations be read?

The planning assumptions recorded for sample-size illustrations specify a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They describe an effect to detect as a stated fraction of the observed effect. Such calculations are planning illustrations based on an observed effect, not the study’s own design justification, and their participant counts are intended per arm. The registry record does not report a sample-size justification for the study.

In general, a planning calculation asks how much information a future study might need under chosen assumptions. Its output depends on those assumptions, including the effect size selected, variability, statistical threshold, allocation, and model. A planning estimate is not observed power and does not demonstrate that a completed study had adequate power. Here, no primary outcome estimate is reported in the registry record, so the observed effect underlying a planning illustration cannot be assessed from the registered outcome results.

Normal approximations can be useful when their assumptions are appropriate, but they do not correct for a mismatch between the assumed comparison and the actual study design. The planning assumptions describe two arms, whereas the registered model is single group and the record cautions that there is no like-for-like control comparison. Any resulting planning illustration should therefore be understood as a hypothetical design calculation, not as an analysis of this study’s outcomes.

Why might variability and measurement matter?

In general, standard deviation is useful for describing variability in a continuous measure. If measurements are strongly skewed or contain influential observations, the mean and standard deviation may not fully convey the distribution. Repeated MRI measurements can also raise questions about measurement consistency and whether assessors were blinded, but details of image assessment, measurement reliability, and assessor procedures are not reported in the registry record. Masking is recorded as none; the record does not explain which study roles that field refers to.

More generally, analysis should match the data structure. If observations are repeated within participants, their dependence may need to be reflected in the analysis; treating related measurements as independent can misstate uncertainty. The registry does not report whether repeated observations were collected or how any such dependence was handled. These are general considerations, not evidence that a particular analysis was conducted.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures and 0 analyses. It identifies bone tunnel diameter as the primary outcome, but the other outcome measure and its analysis are not described in the available record. The analysis plan, including any hierarchy among outcomes or hypotheses, is not reported in the registry record.

In general, evaluating multiple outcomes or hypotheses creates a multiplicity issue: the more statistical tests conducted, the greater the chance that at least one result may appear notable by chance. Methods such as prespecifying a primary outcome, adjusting significance thresholds, or treating secondary findings as exploratory can address different aspects of this problem. The registry record does not report whether any such approach was planned or used. The stated hypotheses about graft type, timing, and bone mineral density should not be treated as confirmed findings or as a documented testing plan.

Missing-data procedures and analysis populations are also not reported in the registry record. The enrollment listing does not establish how many participants contributed an MRI measurement at 2 years, whether any measurements were unavailable, or how unavailable data were handled. The record does not describe exclusions, deviations, imputation, or a rule defining which participants entered an analysis. Without those details, the relationship between enrollment and any outcome estimate cannot be assessed.

In general, missingness can affect both the precision and interpretation of an estimate, especially if the availability of measurements is related to participant characteristics or outcomes. The registry contains no information that would support a conclusion about the presence or absence of such bias. No inferential results are reported, so multiplicity adjustments and analysis-population choices cannot be evaluated.

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.

The registry lists 0 serious adverse events among 18 patients at risk and 0 affected. It also lists 0 other adverse events among 18 at risk and 0 affected, with 0 deaths. These are the safety counts recorded for the Patients group. No serious adverse event terms are listed.

In general, a count of zero means that no events of that category were recorded in the listed group during the registry’s reporting context. It does not establish that the underlying risk is zero. Interpretation depends on the period of observation, how events were defined and collected, completeness of follow-up, and the number of participants with safety data. Those details are not reported in the registry record.

These figures are not a comparison between graft types or between treated and untreated groups. The study is recorded as single group, and comparative safety analyses are not reported. The counts therefore describe the posted safety record but do not establish that one graft or procedure has fewer events than another. They also do not resolve risks that may be uncommon or not captured in the record.

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

The record establishes that a completed study listed MRI-measured bone tunnel diameter at 2 years as its primary outcome. It also records hypotheses about possible differences by graft type, early postoperative widening, and an association with pre-operative bone mineral density. Those details identify the scientific questions of interest, but they are not outcome findings.

The primary endpoint’s mean and standard deviation are not reported, and the registry lists 0 analyses. There is no reported estimate of tunnel diameter or widening, no confidence interval, and no p-value. As a result, the posted information does not show the size or precision of a possible difference, whether tunnel dimensions changed over time, or whether any relationship with graft type or bone mineral density was observed.

The listed study structure further limits what can be concluded. The model is single group, allocation is NA, and the record cautions that the study is not a randomized comparison with like-for-like control arms. The graft types named in the hypotheses do not amount to documented comparison groups. Without group definitions, outcome results, and an analysis plan, a causal or comparative interpretation is not supported by the registry information.

In general, an observed association does not by itself establish causation, and a difference in a continuous outcome needs both an estimate and uncertainty to assess its precision. A single measurement timeframe also cannot establish when a change occurred. The hypothesis about widening before 8 weeks is not answered by the primary outcome timeframe of 2 years unless relevant early measurements and their analyses are reported; they are not reported in the registry record.

The safety counts record no serious adverse events, other adverse events, or deaths in the listed categories. These counts are descriptive and do not constitute evidence of comparative safety or absence of risk. The defensible interpretation is therefore limited: the record documents the study questions, design classification, outcome definition, and safety counts, but does not report results that answer the stated efficacy or association questions.

13. Why This Trial Matters Statistically

This study is statistically interesting because its stated questions involve several distinct forms of evidence: describing a continuous anatomical measurement, comparing graft types, assessing when widening occurs, and examining an association with pre-operative bone mineral density. Each question requires outcome data and an analysis suited to the question. A single primary measurement at 2 years cannot, by itself, answer every question about group differences, timing, and association.

The record also illustrates why a hypothesis is not the same as a result. The brief summary describes expected or proposed relationships, but the registry lists a single-group model and does not report analyses. Without measured estimates and uncertainty, readers cannot tell whether the data supported, contradicted, or were inconclusive about those hypotheses. That distinction is essential when interpreting clinical research records.

Design and analysis must also align. The planning assumptions describe two-arm calculations, while the registered study model is single group and the record warns that the arms are not a like-for-like control comparison. Planning calculations can help illustrate what a future comparison might require, but they do not create a valid comparison in an existing study or show that a study’s results are precise.

Finally, the record highlights the importance of reporting the pathway from enrollment to analysis: who had usable imaging, which timepoints were measured, how the continuous outcome was summarized, and how missing observations were handled. Those details are not reported in the registry record. Their absence prevents readers from judging the completeness and precision of the outcome evidence, even though the research question itself is clinically specific.

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.

A central limitation of the available record is that it contains no numerical primary outcome results. The mean and standard deviation are identified as the intended summary statistics, but neither is reported. There is also no reported confidence interval, p-value, or analysis result. The magnitude and precision of bone tunnel diameter at 2 years therefore cannot be assessed.

The registry records a single-group model, allocation as NA, and no masking. It also states that this is not a randomized comparison and that arms are not a like-for-like control comparison. Although the hypotheses discuss multiple graft types, the record does not describe corresponding groups, group sizes, or graft assignment. This prevents a meaningful assessment of the proposed graft comparisons.

The primary endpoint is specified at 2 years, whereas one hypothesis concerns widening before 8 weeks. The record does not report early measurements or their analysis, so the timing hypothesis cannot be evaluated. Details about image measurement procedures, reliability, follow-up completeness, and participant characteristics are also not reported in the registry record.

The record lists 2 outcome measures but only identifies the primary measure in detail, and it lists 0 analyses. It does not report a statistical analysis plan, missing-data handling, analysis populations, or multiplicity procedures. The enrollment listing does not establish how many participants contributed to the primary outcome analysis.

Finally, the safety figures are counts without detailed information about observation periods or event-collection procedures. They are not comparative estimates. These limitations concern what can be learned from the registry record; they do not establish what the full study may have collected or analyzed outside that record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Bone Tunnel Widening Following ACL Reconstruction — NCT00198042.
• Registry record last updated 2017-05-17; status last verified 2017-05.
• Results first posted 2017-05-17.
• 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 a completed, single-group study of surgical ACL reconstruction, with enrollment of 18. The listed primary outcome is bone tunnel diameter measured by MRI at 2 years, summarized as a mean and standard deviation. The study hypotheses concern graft type, early postoperative tunnel widening, and pre-operative bone mineral density.

The record lists 2 outcome measures and 0 analyses. Numerical primary outcome results, comparator group details, and analysis methods are not reported in the registry record. Safety counts list 0 serious adverse events, 0 other adverse events, and 0 deaths. The record documents the questions and outcome definition, but does not report findings that answer the stated hypotheses.