Radiographic and Clinical Outcomes Following Unilateral or Bilateral Posterior Fixation in MI-TLIF: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Radiographic and Clinical Outcomes Following Unilateral or Bilateral Posterior Fixation in MI-TLIF (NCT01996371), a randomized na study. The primary outcome is Compare Bony Fusion Rates Radiographically Using CT Scans.

2. Clinical Question

The central question concerned whether the pattern of posterior fixation was associated with differences in fusion observed after surgery. The registry describes assessment of new solid osseous trabeculations bridging across the interspace on postoperative CT scans. This makes the primary endpoint a radiographic assessment of bone bridging rather than a patient-reported measure.

The registry also describes comparisons of clinical outcomes and immediate and delayed medical and surgical complications. Listed secondary outcomes include the Visual Analog Scale (VAS), Oswestry Disability Index v2 (ODI v2), and Short Form 36 Health Survey v2 (SF-36 v2). Those measures address aspects of symptoms, disability, and health status, but the registry record does not report their results. It also does not report a numerical comparison of the three approaches for any outcome. Because the record states that the research was discontinued and data were not collected or analyzed, it cannot answer whether the groups differed in radiographic fusion or clinical outcomes.

3. Trial Design

The registry classifies the study as randomized, with a parallel-group model and no masking. It lists three groups: unilateral pedicle screws; ipsilateral pedicle screws with a contralateral facet screw; and bilateral pedicle screws. The listed intervention is a pedicle screw device. Enrollment is recorded as 15, but the registry does not describe the randomization procedure, allocation concealment, or how participants were assigned among groups.

The study concerns posterior fixation following MI-TLIF for lumbar disease. The primary outcome was planned as a comparison of bony fusion rates assessed radiographically at 24 months. The registry describes postoperative CT evaluation using the Brantigan, Steffee and Fraser scale, with attention to new solid osseous trabeculations bridging across the interspace. Clinical outcomes and immediate and delayed medical and surgical complications were also included in the study description. VAS, ODI v2, and SF-36 v2 are listed as secondary outcomes.

The record gives a study start of 2014-01 and a primary completion date of 2020-05. Its status is terminated. Most importantly for interpreting the design, the primary-outcome entry states that research was discontinued and that data were not collected and therefore not analyzed. No analyzed population, follow-up completeness, or participant flow is reported in the registry record. The enrollment figure therefore should not be read as the number with an observed primary outcome.

The record does not report the reason for termination, a protocol amendment history, the planned allocation ratio, or the intended statistical analysis plan. It does not report whether participants or assessors were masked; the study-level masking classification is none. A randomized design can reduce systematic differences between groups when implemented as planned, but randomization alone does not establish that outcomes were collected or that a valid comparison was completed. In this study, the absence of primary-outcome data prevents assessment of the intended group comparison.

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: Research has been discontinued. Data not collected and therefore not analyzed.

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: All subject ethnicity: White

6. Primary Endpoint

The registry lists the primary outcome as Compare Bony Fusion Rates Radiographically Using CT Scans, measured over 24 months.

The primary endpoint was the comparison of bony fusion rates among the three groups at 24 months. The registry describes fusion assessment from postoperative CT scans, using the Brantigan, Steffee and Fraser scale. The feature specified for evaluation is new solid osseous trabeculations bridging across the interspace. In general, a radiographic endpoint provides an imaging-based way to assess structural healing at the operated level. A scale can standardize how images are classified, although the registry does not provide scoring details or thresholds for the categories in this entry.

The endpoint is distinct from a report of symptoms or functional status. A radiographic assessment addresses whether imaging evidence of bridging bone is present according to the scale; it does not by itself quantify pain, disability, overall health, or complications. The registry identifies VAS, ODI v2, and SF-36 v2 as secondary clinical measures, which would address different aspects of patient experience and function.

The planned follow-up point was 24 months, but no result is available. The primary-outcome record explicitly states that research was discontinued and data were not collected and therefore not analyzed. Accordingly, there is no observed fusion rate, group estimate, uncertainty interval, or statistical comparison to interpret. The registry record also does not report the number of CT scans obtained, how scans were read, or whether image assessment was blinded. These details cannot be inferred from the endpoint description.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomized parallel-group design. The registry identifies the study as randomized and parallel, with three fixation groups and no masking. In a randomized study, allocation is intended to limit systematic selection differences between groups. In a parallel-group design, each participant is assigned to one approach rather than moving through several approaches. These design labels describe the intended structure; they do not show how allocation was carried out in practice. The randomization method, allocation concealment, and allocation ratio are not reported in the registry record.

The study is listed as unmasked. In general, masking can limit the influence of knowledge about group assignment on outcome assessment or reporting. Its absence does not automatically invalidate a study, but it can matter when outcomes involve judgment or participant reports. The registry does not report whether CT readers were masked to group assignment, or whether those collecting VAS, ODI v2, and SF-36 v2 responses were masked. The study-level masking entry alone does not answer those specific questions.

What would a group comparison estimate?

For the primary endpoint, a group comparison would ordinarily summarize radiographic fusion outcomes for each fixation approach and estimate how those outcomes differ. A point estimate describes the observed contrast in the analyzed participants. A confidence interval, when reported, conveys the range of values compatible with the data and the specified statistical method. Neither an estimate nor a confidence interval is reported for the primary endpoint in this registry record, because the record says data were not collected and therefore not analyzed.

The Brantigan, Steffee and Fraser scale is named as the method for classifying CT evidence of fusion. The registry specifies new solid osseous trabeculations bridging across the interspace as the radiographic feature to evaluate. It does not say whether the analysis would treat the scale as categories, a binary fusion classification, or another form of outcome. The record also does not describe the scoring process, reader agreement, handling of equivocal scans, or an analysis model. It would be inappropriate to assume a particular test or model.

How should clinical endpoints be distinguished?

The listed secondary measures are VAS, ODI v2, and SF-36 v2. In general, patient-reported measures can complement imaging by recording symptoms, disability, or health status from the participant’s perspective. A radiographic finding and a clinical score are different outcomes and need not move together. Interpreting a clinical measure usually requires knowing how it was scored, when it was collected, what baseline values were, and how missing responses were handled. These analysis details and the clinical results are not reported in the registry record.

The study description also refers to immediate and delayed medical and surgical complications. In general, safety summaries may count participants with at least one event, total events, or events within defined categories; these quantities are not interchangeable. The registry displays participant counts for serious events, other events, and deaths by group. It does not report the definitions, event-level descriptions, observation periods, or statistical comparisons needed to interpret those counts beyond their descriptive form.

What do the absence of estimates and tests imply?

A p-value is a measure calculated under a statistical model to describe how compatible data are with a specified null hypothesis. It is not a measure of clinical importance, and it cannot be interpreted without an analyzed outcome and a stated comparison. No p-values are reported for the primary or secondary outcomes. A confidence interval is also not reported. Consequently, there is no basis for assessing statistical significance, precision, or the range of plausible group differences in the primary endpoint.

The registry record lists no analyses. It does not report an analysis population, a primary model, covariate adjustment, handling of repeated or incomplete measurements, or a plan for multiple comparisons. These omissions mean that the analysis strategy cannot be reconstructed from the record. General statistical principles can explain why these choices matter, but cannot substitute for the missing trial-specific details.

Enrollment is recorded as 15. Enrollment is a study-level figure and does not establish how many participants contributed data to any outcome. For the adverse-event entries, the registry gives denominators at risk separately by group. Those figures describe the displayed safety entries; they do not establish follow-up completeness for the planned 24-month CT outcome. The primary outcome was not analyzed, so there is no observed effect on which to base a conventional estimate of uncertainty.

The registry includes a description of assumptions used for planning illustrations based on an observed effect, but it reports no calculated planning values in this record and no analyzed primary effect. Such illustrations are not observed power and do not represent an outcome from the trial. Because no observed primary effect is available, the listed assumptions cannot support a trial-specific estimate of the sample size needed to detect a difference.

10. Multiplicity, Missing Data and Analysis Populations

The study includes a primary radiographic outcome, several listed secondary clinical outcomes, and safety outcomes. When many outcomes or comparisons are tested, the chance of at least one apparently notable result can increase unless the analysis plan addresses multiplicity. In general, a prespecified hierarchy or adjustment can clarify how multiple tests are to be interpreted. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or which contrasts among the three groups were planned.

Missing-data methods are also not reported. The primary-outcome entry states that research was discontinued and data were not collected and therefore not analyzed. It does not provide participant-level follow-up, numbers with missing CT scans, reasons for missing assessments, or a procedure for handling incomplete outcomes. As a result, no missing-data assumptions or sensitivity analyses can be evaluated. The recorded enrollment should not be treated as an analyzed sample for the primary endpoint.

The analysis population is not reported in the registry record. There is no statement about whether an intended analysis would include all randomized participants, only participants with available outcomes, or another group. The registry also does not report how protocol deviations, withdrawals, or eligibility changes were handled. These details are important because the set of participants included in an analysis affects the interpretation of a randomized comparison.

Without outcome data and an analysis plan, the statistical consequences of multiple outcomes and missing observations cannot be quantified. No adjusted or unadjusted primary comparison is available, and there are no reported sensitivity analyses to show whether conclusions would change under different assumptions.

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: bilateral pes (25.0%), compression fracture (20.0%), disc herniation (16.7%).

The registry lists serious adverse events for each group: 1 of 5 participants in Group 1, 1 of 4 in Group 2, and 1 of 6 in Group 3. It separately lists other adverse events affecting 2 of 5, 2 of 4, and 4 of 6 participants, respectively. Deaths are recorded as 0 in all three groups. These figures should be read as descriptive participant counts in the registry, not as a comparative analysis.

The registry also names Bilateral PEs at 25.0%, Compression Fracture at 20.0%, and Disc Herniation at 16.7% among its listed top serious terms. The entry does not give event counts or further context for these percentages, so they should not be converted into participant counts or used to infer differences between groups. The record does not report event timing, exposure duration, severity detail beyond the serious-event category, or whether participants could contribute more than one event.

In general, safety counts depend on how events are defined, collected, and followed over time. The registry record does not describe those procedures or provide an inferential comparison. The recorded deaths of 0 in each group do not establish that the approaches have equal safety, particularly without a reported safety analysis and complete follow-up information.

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

The registry record documents a planned randomized comparison of three posterior fixation approaches in MI-TLIF, with a 24-month CT-based fusion outcome and several clinical measures. It also records an enrollment of 15 and a terminated study status. These registry entries describe the study’s intended question and its registry status; they do not constitute an efficacy result.

The primary-outcome entry states that research was discontinued and data were not collected and therefore not analyzed. Accordingly, there is no radiographic fusion result to compare among unilateral pedicle screws, ipsilateral pedicle screws with a contralateral facet screw, and bilateral pedicle screws. No conclusion about which approach had higher or lower fusion rates is supported by the registry record. The same limitation applies to VAS, ODI v2, and SF-36 v2: the outcomes are listed, but no results are reported.

The safety entries offer limited descriptive information, including participant counts for serious and other adverse events and deaths by group. They do not provide a full safety analysis or establish a comparative risk. The listed serious-event terms and percentages likewise do not provide a basis for ranking the approaches, particularly because event counts and contextual details are absent.

These results do not demonstrate equivalence or prove that the approaches differ. An absence of analyzed results is different from a well-estimated absence of a difference. The record also does not report why the study was terminated, whether any other data were collected outside the primary outcome, or whether further analyses were conducted but not registered. Those matters remain unknown from the registry record.

The appropriate conclusion is narrow: the study’s planned clinical and radiographic comparisons are described, but the registered record does not contain analyzed outcome data with which to answer them. Readers should distinguish that lack of evidence in this record from evidence that one approach is better, worse, or the same as another.

13. Why This Trial Matters Statistically

This trial is statistically notable because its design description and its outcome record tell different parts of the story. The registry identifies a randomized, parallel-group comparison among three fixation approaches, which frames a comparative question. At the same time, it reports that the research was discontinued and that primary-outcome data were not collected or analyzed. A clearly stated design cannot yield an interpretable effect estimate in the absence of analyzed outcomes.

The distinction matters for reading trial registrations. Enrollment is not the same as an analyzed sample, and a planned endpoint is not a result. Here, the record lists enrollment of 15 and a 24-month CT outcome, but does not report a fusion estimate, a confidence interval, or a statistical test. Those missing elements prevent readers from assessing either the direction or precision of the planned comparison.

The three-arm structure also makes it important to know which comparisons were intended and how multiple outcomes were to be handled. There are primary radiographic and secondary clinical outcomes, along with complications, but the registry does not report the analysis plan or multiplicity strategy. Without those details—and without outcome data—it is not possible to reconstruct a confirmatory analysis.

The record’s adverse-event entries illustrate another distinction: descriptive counts are not comparative evidence. Counts can inform a basic description of what was recorded, but interpretation depends on definitions, follow-up, and analysis. Those details are not reported. The study therefore highlights why a statistical reading should separate the question a trial was designed to ask from the evidence actually available in its registry results.

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 principal limitation is that the registry states the study was discontinued and that primary-outcome data were not collected or analyzed. This means there is no reported radiographic outcome at the planned 24-month assessment, despite the detailed description of CT-based fusion evaluation. The reasons for discontinuation are not reported in the registry record, so the effect of termination on the study’s conduct cannot be assessed.

The record lists enrollment as 15 but does not provide participant flow, group-specific enrollment for the primary endpoint, withdrawal information, or follow-up completion. It also does not report whether any CT assessments or clinical questionnaires were collected before discontinuation. No baseline characteristics are available in the record, so the groups’ characteristics cannot be described or compared.

Several operational details are absent: the randomization procedure, allocation concealment, timing of assignment, CT reading process, assessor masking, and scoring details for the Brantigan, Steffee and Fraser scale. The registry does not report the planned statistical model, comparison structure, analysis population, handling of missing data, or multiplicity approach. These omissions prevent assessment of the intended analysis even apart from the lack of outcome data.

The safety entries are also limited. The record provides participant counts by group and a short list of serious-event terms with percentages, but does not report event timing, definitions, participant-level histories, duration of observation, or a comparative safety analysis. The adverse-event figures should therefore be treated as registry descriptions, not as a complete assessment of comparative safety.

Finally, no primary or secondary outcome estimates, confidence intervals, or p-values are reported. The record does not establish that any group difference was present, absent, or clinically meaningful. These limitations are specific to what the registry documents and should not be filled in by assumptions about the protocol or the conduct of the study.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Radiographic and Clinical Outcomes Following Unilateral or Bilateral Posterior Fixation in MI-TLIF — NCT01996371.
• Registry record last updated 2021-11-09; status last verified 2021-10.
• Results first posted 2021-11-09.
• 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.

18. Record Summary

The registry record describes a randomized, unmasked, parallel-group study of three posterior fixation approaches following MI-TLIF for lumbar disease. The approaches were unilateral pedicle screws, ipsilateral pedicle screws with a contralateral facet screw, and bilateral pedicle screws. Enrollment is listed as 15, and the status is terminated.

The primary endpoint was a comparison of radiographic bony fusion at 24 months, assessed on CT scans using the Brantigan, Steffee and Fraser scale. VAS, ODI v2, SF-36 v2, and complications are also described. The primary-outcome entry states that research was discontinued and data were not collected and therefore not analyzed. No analyzed outcome estimates or statistical comparisons are reported. Adverse-event participant counts and deaths are listed by group, but the registry does not report a full comparative safety analysis.