Optimization of Spinal Manipulative Therapy Protocols: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Optimization of Spinal Manipulative Therapy Protocols (NCT02868034), a randomized phase 2 study. The primary outcome is Spinal Stiffness.

2. Clinical Question

3. Trial Design

This was a randomized, double-masked, Phase 2 trial with a factorial model. The registry lists 273 participants and identifies the condition as low back pain. The study status is completed. Its start date is 2017-02-22, and its primary completion date is 2019-01-12. The sponsor was the University of Utah.

The factorial design focused on three treatment components: SMT, mobilizing exercise, and activating exercise. The listed treatment regimens vary in whether these components are included and combined. They include SMT during week 1 without additional treatment; extended SMT during weeks 2-4; exercise components during weeks 2-4; and combinations of SMT with one or both exercise components. The descriptions specify two SMT sessions in week 1 for regimens that include initial SMT, with six additional sessions or exercise sessions during weeks 2-4 where applicable.

Considering treatment components separately and jointly is a key feature of a factorial design. A main effect represents the average association of a component across the levels of other components in the design; an interaction asks whether the association of one component depends on another. These are general explanations of factorial analysis, not confirmation of the precise contrasts or model terms used for every posted analysis. The registry says the primary outcome was examined using main effects and interactions among the three components.

The registry identifies double masking, but does not report which parties were masked or how masking was maintained. The method used to generate the random assignment, allocation concealment, treatment adherence, and the reasons for selecting the enrollment target are not reported in the registry record. The design description alone does not establish that every participant received or completed the assigned regimen.

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.

Before assignment: Participants were enrolled into Phase I of the study (enrollment - 1 week). After the completion of Phase I participants were randomized to an intervention arm for Phase II (1 week - 12 weeks). Baseline data are provided from the 1-week assessment, which corresponds to the time of randomization and beginning of Phase II.

Only the first 6 of 8 groups are shown.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Results were examined based on the main effects and interactions among the 3 treatment components in the factorial study design (SMT, Mobilizing Exercise, Activating Exercise). Scores were missing for participants in the SMT group (n=21 at 4 weeks and 12 weeks), Mobilizing exercise (n=14 at 4 weeks and n=19 at 12 weeks), and Activating exercise (n=16 at 4 weeks and n=22 at 12 weeks)

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: 315 individuals provided consent and 273 met all eligibility criteria and enrolled in Phase I. Of these 32 (11.7%) withdrew during treatment phase I, leaving 241 participants who completed the 1-week assessment and were randomized to receive additional treatment components in Phase II. The Phase II baseline information is provided.

Only the first 6 of 9 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Spinal Stiffness, measured over Assessed at Phase II Baseline, 4 weeks, 12 weeks. 4 weeks and 12 weeks reported. Phase II baseline values were constrained to be equal to a common overall mean for analyses..

The primary endpoint is spinal stiffness, measured in N/mm using the VerteTrack device. The device applies a vertical load along the lumbar spine while the participant is prone. A sensor in the indenter continuously measures spinal deformation in response to the defined load. Stiffness is calculated as the ratio of the maximum applied force to the resulting displacement. The registry states that higher values indicate greater stiffness.

This measure captures a physiologic response of the spine under a standardized loading procedure. The trial’s stated rationale is that prior research had identified physiologic effects related to clinical benefits from spinal manipulation, and that such effects could help inform optimized treatment protocols. That rationale explains why a stiffness measure was selected for study; it does not establish that a change in stiffness is itself a clinical benefit or that it predicts a clinical outcome in this trial.

The primary outcome description gives assessments at Phase II baseline, 4 weeks, and 12 weeks, but says that baseline values were constrained to be equal to a common overall mean for the analyses. It identifies 4-week and 12-week results as reported time points. The outcome is summarized as a mean with a 97.5% confidence interval. Numerical means and intervals by treatment component or regimen are not reported in the registry record. The registry also does not report a threshold for a clinically important difference in stiffness.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a randomized, double-masked trial with a factorial model. Those labels describe design features, but do not supply the full statistical analysis plan. Randomization is generally used to make treatment groups comparable in expectation, including with respect to factors that were not measured. It does not guarantee that groups will be identical, and it does not by itself establish how missing measurements or multiple analyses were handled. The randomization method and allocation concealment are not reported in the registry record.

What does a factorial model ask?

In general, a factorial design studies more than one treatment component within the same trial. This record identifies SMT, mobilizing exercise, and activating exercise as the components. Main effects ask about the association of each component averaged across the levels of the other components. Interactions ask whether the association of a component changes depending on whether another component is present. An interaction can matter because a component’s effect may not be the same in every combination.

The registry says that the primary outcome was examined using main effects and interactions among the three components. It does not report the exact model specification, contrast coding, covariates, or the estimates and tests used for those terms. The component-based description is therefore useful for understanding the study’s intended structure, but it is not enough to reconstruct the analysis or identify which particular comparisons drove any result.

How should the endpoint summary be read?

The primary measure is a mean spinal-stiffness value in N/mm, reported with a 97.5% confidence interval. In general, a mean represents the arithmetic center of measurements, while its confidence interval describes uncertainty about the estimated mean under the chosen statistical model. The interval does not describe the spread of individual participants’ measurements. A narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty, but precision depends on the data and analysis assumptions.

The registry says that Phase II baseline values were constrained to a common overall mean for analyses and that 4-week and 12-week values were reported. This is a description of how baseline values were treated in the analysis, not a reported baseline result for each treatment group. The detailed model, the reason for this constraint, and whether other baseline adjustments were used are not reported in the registry record. No numerical means or confidence limits for the primary endpoint are included in the record described.

What is the role of the confidence level?

In general, a confidence interval is constructed by a method intended to have a stated long-run coverage under its assumptions. A 97.5% confidence interval is the interval type named for this outcome. That label alone does not show whether an estimate is compatible with no difference, nor does it identify the size of a treatment effect. The interval endpoints and the contrast to which an interval applies are needed for that interpretation; they are not reported in the registry record. No p-value for the primary outcome is reported there either.

Why do missing measurements matter?

The primary-outcome population description notes missing scores for participants in the SMT group, with n=21 at 4 weeks and 12 weeks, and in the Mobilizing exercise group, with n=14 at 4 weeks, followed by an incomplete description. The record excerpt does not give a complete account of missing scores across components, regimens, and time points. It also does not report whether the analysis used complete cases, imputation, likelihood-based methods, or another approach.

In general, missing outcome data can affect both precision and the interpretation of an estimate. If the likelihood of a score being missing is related to the unobserved score or to treatment experience, an analysis of only observed measurements may not represent the originally randomized groups. Different missing-data assumptions can produce different estimates. The counts alone do not establish why data were missing or whether missingness differed systematically between groups.

What does the analysis count tell the reader?

The registry lists 56 analyses and four outcome measures. It names Oswestry Disability Index and Pain Intensity as secondary outcomes; the other outcome names are not reported in the registry record. A large set of analyses can raise multiplicity concerns because repeatedly testing hypotheses increases the chance of finding an apparently notable result by chance. In general, multiplicity can be addressed through a prespecified hierarchy, adjustment procedures, or a carefully defined focus on selected estimates. The registry record does not report whether any such approach was used, so the number of analyses should not be mistaken for evidence that results were adjusted or that a particular result was prespecified.

How should planning calculations be interpreted?

The planning assumptions describe illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They define the effect to detect as a stated fraction of the observed effect. In general, such calculations describe sample sizes under assumed conditions; they are not observed power and do not describe the trial’s actual enrollment outcome. The record does not report the trial’s own sample-size justification. The effect estimate underlying the illustration and the resulting planning values are not reported in the registry record, so no numerical planning conclusion can be drawn from the assumptions alone.

Overall, the registry gives enough information to identify the broad factorial structure and endpoint but not to reproduce the statistical analysis. The exact model, analysis populations, handling of missing data, multiplicity strategy, and numerical outcome estimates are not reported in the registry record. General statistical principles help explain what the design could address, but they cannot substitute for those trial-specific details.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 56 analyses and four outcome measures. It names Oswestry Disability Index and Pain Intensity as secondary outcomes, while the primary outcome is spinal stiffness. The registry record does not report a multiplicity strategy, such as a prespecified testing hierarchy or adjustment procedure. With multiple outcomes, time points, treatment components, interactions, and analyses, the number of opportunities to observe an apparently notable result can increase. That general concern does not establish that the reported analyses are invalid; it means that the role of prespecification and any adjustment cannot be evaluated from the record.

The primary outcome is described at 4 weeks and 12 weeks, with baseline values constrained to a common overall mean for analyses. The population description reports missing scores for the SMT group (n=21 at 4 weeks and 12 weeks) and for the Mobilizing exercise group (n=14 at 4 weeks), but the description is incomplete. The full pattern of missingness is not reported in the registry record. Reasons for missing scores, analysis populations, and methods for handling missing data are also not reported there.

In general, an analysis population determines which participants contribute to an estimate. An intention-to-treat approach aims to retain participants in their randomized groups, while other approaches may use different inclusion criteria. The registry record does not state which population was used for the primary analysis, so the analysis cannot be classified on that basis. Missingness can affect both estimates and precision, and its influence depends on why measurements are absent and how the analysis handles them. Those details are not reported in the registry record.

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 non-serious adverse event terms

The safety figures report zero serious adverse events in each listed group and zero deaths in each listed group. The numbers at risk are reported by group: 30 for No Further Treatment, 29 for Extended SMT, 30 for Activating Exercise Component Only, 31 for Mobilizing Exercise Component Only, 30 for SMT With Activating Exercise Component, 29 for SMT With Mobilizing Exercise Component, 30 for Activating Exercise and Mobilizing Exercise Components, and 32 for SMT With Activating Exercise and Mobilizing Exercise Components.

The reported counts affected by other adverse events are 3, 8, 9, 10, 12, 7, 5, and 13, respectively, in those same listed groups. The registry does not identify the types of these other events or provide a detailed account of their severity, timing, or duration. It also does not report a statistical comparison of adverse events between groups.

These are descriptive counts, not adjusted risks or evidence of a causal difference between regimens. In general, safety comparisons depend on consistent event definitions, follow-up, ascertainment, and the denominator used. The registry reports numbers at risk, but the information described does not establish whether every group had identical follow-up or event collection. The zero serious-event and death counts should be read as the counts reported for this trial, not as evidence that such events are impossible or that broader safety has been established.

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

The registry record establishes that this completed, randomized, double-masked Phase 2 trial studied combinations of SMT, mobilizing exercise, and activating exercise for low back pain. It identifies spinal stiffness as the primary outcome and describes how that measure was obtained. It also reports that the primary outcome was examined using main effects and interactions among the three treatment components.

However, the numerical estimates for spinal stiffness at 4 weeks and 12 weeks are not reported in the registry record described. That means the size and direction of the primary-outcome findings, and the precision of those estimates, cannot be assessed from the available registry information. The endpoint definition does not indicate whether stiffness changed, whether components differed, or whether combinations interacted. The registry also does not report a clinically important threshold for spinal stiffness, so clinical importance cannot be judged from the endpoint description.

The record names Oswestry Disability Index and Pain Intensity as secondary outcomes, but their results are not reported in the registry record described. Therefore, no conclusion can be drawn from this information about the findings for disability or pain, or about whether those measures align with spinal stiffness.

The safety record reports zero serious adverse events and zero deaths in each listed group, alongside group-specific counts affected by other adverse events. Those counts are descriptive and do not establish a treatment-related safety difference. Event types and a formal comparison are not reported in the registry record.

The trial’s stated aim was to examine strategies for identifying optimized treatment protocols using physiologic effects related to spinal manipulation. The record supports describing that objective and the design used to investigate it. It does not support a claim that a specific regimen was superior, that a treatment works or does not work, or that the trial established a clinical benefit. Such claims require interpretable outcome estimates and supporting analysis details that are not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically notable for its factorial structure. Rather than treating each regimen only as an isolated package, the design identifies SMT, mobilizing exercise, and activating exercise as components whose main effects and interactions were examined. In general, that approach can help distinguish component-level patterns from the effect of a single bundled regimen. It can also ask whether the contribution of one component depends on another. Those questions are relevant to protocol development, which was the stated purpose of the study.

The primary outcome adds a physiologic measure to the trial’s clinical context. VerteTrack quantifies spinal deformation under a defined load, and the registry describes stiffness as the ratio of applied force to displacement. The study rationale connects physiologic effects with the effort to optimize treatment protocols. This is a research question about how a measured physiologic response relates to treatment components; the rationale itself is not evidence that the response predicts clinical outcomes.

Statistically, factorial interpretation depends on clear estimates for main effects and interactions, as well as uncertainty around those estimates. The registry record identifies the intended component-based analysis but does not provide its numerical results. It also lists 56 analyses and reports missing outcome scores without a complete missing-data account. These details make prespecification, multiplicity, and analysis-population reporting important for interpreting the evidence, yet those methods are not reported in the registry record.

The record therefore illustrates both the potential and the limits of a registry summary. It describes the design, measurement, and safety counts in a way that frames the statistical questions. Without primary-outcome estimates, full analysis details, and complete missing-data information, the substantive component effects and their precision remain unclear. That distinction matters: an informative design can pose useful questions, but its conclusions depend on results and methods sufficiently reported to evaluate them.

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 main limitation for interpretation is that numerical primary-outcome estimates are not reported in the registry record described. The record identifies the measure, units, time points, and summary type, but not the mean spinal-stiffness values or confidence-interval endpoints. Consequently, the magnitude, direction, and precision of component effects and interactions cannot be evaluated. Numerical results for the named secondary outcomes are also not reported in the registry record.

The description of missing primary-outcome scores is incomplete. It reports missing scores for the SMT group at 4 weeks and 12 weeks and for the Mobilizing exercise group at 4 weeks, but does not provide a complete account across all treatment components and time points. Reasons for missingness, the analysis population, and the method used to handle missing measurements are not reported in the registry record. These omissions limit assessment of possible bias and precision.

The record says that main effects and interactions were examined, but does not give the full statistical model, contrasts, covariate adjustments, or multiplicity strategy. It lists 56 analyses, making it important to know how primary and secondary questions were prioritized; that information is not reported. The trial’s sample-size justification and the basis for the enrollment target are also not reported in the registry record.

Masking is identified as double, but which parties were masked and how masking was implemented are not reported. The randomization procedure and allocation concealment are also not reported. For safety, the record gives counts but does not identify other adverse-event types or provide a formal group comparison. These registry reporting limitations do not establish that the trial lacked these methods or analyses; they mean that the details cannot be assessed from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Optimization of Spinal Manipulative Therapy Protocols — NCT02868034.
• Registry record last updated 2023-05-17; status last verified 2023-04.
• Results first posted 2023-05-17.
• 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

NCT02868034, titled Optimization of Spinal Manipulative Therapy Protocols, is a completed randomized, double-masked Phase 2 factorial trial sponsored by the University of Utah. It enrolled 273 participants with low back pain. The study evaluated regimens involving SMT, mobilizing exercise, and activating exercise.

Spinal stiffness, measured in N/mm using the VerteTrack device, was the primary outcome. The registry identifies results at 4 weeks and 12 weeks and says baseline values were constrained to a common overall mean for analyses. It lists Oswestry Disability Index and Pain Intensity as secondary outcomes. Numerical efficacy results and full statistical-analysis details are not reported in the registry record described.

The safety record reports zero serious adverse events and zero deaths in every listed group, with varying counts affected by other adverse events. Missing-score information is incomplete, and the registry does not report the missing-data approach, analysis populations, multiplicity strategy, or the trial’s sample-size justification.