The Mechanisms of Manual Therapy in the Treatment of Low Back Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Mechanisms of Manual Therapy in the Treatment of Low Back Pain (NCT01168999), a randomized phase 1, phase 2 study. The primary outcome is Believability of Placebo.

2. Clinical Question

The study’s stated purpose included testing whether a novel placebo was believable and created expectations for treatment effectiveness similar to those associated with the studied spinal manipulation technique. It also proposed comparing low back pain, function, and pain sensitivity across placebo, spinal manipulation, and no-therapy groups. The posted primary outcome, however, is specifically belief about receiving spinal manipulative therapy at baseline; it is not itself a measure of pain relief, function, or sensitivity.

The posted results compare the standard sham with spinal manipulative therapy and with enhanced sham spinal manipulative therapy. The percentages believing they received spinal manipulative therapy were 37% for sham, 67% for spinal manipulative therapy, and 78% for enhanced sham. These observed beliefs address how participants interpreted treatment assignment. They do not establish whether the intervention changed pain or function, and the primary outcome does not report a direct measure of treatment expectation.

3. Trial Design

The registry describes a randomized, single-masked, parallel-group study in Phase 1 and Phase 2, with status listed as completed. The sponsor is the University of Florida. The recorded start was 2009-09 and primary completion was 2013-01. Enrollment is reported as 110. These registry entries describe the study’s broad design and timing, but the record does not report the allocation sequence method, the person or group masked, or the operational details of masking.

The four described groups were spinal manipulative therapy, sham spinal manipulative therapy, enhanced sham spinal manipulative therapy, and natural history. The standard sham was intended to mimic the studied manipulation. The enhanced sham used a similar sham procedure but included an expectation-setting statement. The natural-history arm received no intervention, according to its description. The primary outcome lists results for the three manipulation-related groups but gives a group size of 0 and no value for natural history. The registry record does not report a primary outcome result for that arm.

The primary outcome was assessed at baseline and expressed as the percentage of participants in each arm who believed they had received spinal manipulative therapy. For this endpoint, the posted groups contain 28 participants in the spinal-manipulation arm and 27 participants in each sham arm. The outcome record does not explain why these group counts differ from the overall enrollment or why the natural-history arm has no primary outcome result. Those details are not reported in the registry record.

The record lists nine outcome measures and six analyses. The posted secondary results include changes from baseline at 2 weeks in low back flexion, extension, and right-sidebending range of motion. The registry also names left-sidebending range of motion among its secondary outcomes, but numerical results for that outcome are not reported in the registry record. The record does not report the original sample-size justification, detailed analysis plan, or the approach used to handle missing outcome data.

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

Reasons for not completing this period:

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 Believability of Placebo, measured over baseline.

The primary endpoint is the percentage of participants who believed they had received spinal manipulative therapy, assessed at baseline. It is a binary belief outcome summarized as a percentage for each group. The registry describes it as a way to assess whether participants receiving placebo were blinded to the fact that they were receiving placebo. In this context, a higher percentage means more participants in that group reported believing they received spinal manipulative therapy; it does not by itself indicate that the sham procedure reduced pain or improved function.

This kind of endpoint is relevant to a study comparing a procedure with a simulated version. If participants receiving a sham commonly believe they received the active technique, that observation can inform interpretation of whether the sham seemed credible to participants. The enhanced sham adds a statement about possible benefit, so comparing its belief outcome with the standard sham can describe whether the groups differed in participants’ stated beliefs. The endpoint measures belief, not the success of masking under every definition, and the registry does not report a separate measure of treatment expectation.

The posted results are 67% for spinal manipulative therapy, 37% for sham spinal manipulative therapy, and 78% for enhanced sham spinal manipulative therapy. The natural-history group has no reported primary value. These figures describe the endpoint as recorded at baseline; they should not be read as outcomes measured after a course of treatment. The registry does not report a longer-term primary belief assessment.

7. Results Posted in the Registry

• Spinal Manipulative Therapy: 67.9% (19/28) versus 37.0% (10/27) on control; risk difference 30.8 percentage points (95% CI 5.7 to 55.9), risk ratio 1.83 (1.05–3.19); unadjusted two-proportion z-test p = 0.022.
• Enhanced Sham Spinal Manipulative Therapy: 77.8% (21/27) versus 37.0% (10/27) on control; risk difference 40.7 percentage points (95% CI 16.7 to 64.8), risk ratio 2.10 (1.23–3.57); unadjusted two-proportion z-test p = 0.002.

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.

Change From Baseline at 2 Weeks in Low Back Flexion Range of Motion

• 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:
  • Spinal Manipulative Therapy: mean 1.58 versus 2.67 on control; difference -1.09 (95% CI -7.39 to 5.21), standardized effect d = -0.09; z-test p = 0.734.
  • Enhanced Sham Spinal Manipulative Therapy: mean -0.33 versus 2.67 on control; difference -3.00 (95% CI -9.45 to 3.45), standardized effect d = -0.25; z-test p = 0.362.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Spinal Manipulative Therapy and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Enhanced Sham Spinal Manipulative Therapy and the control. The interval gives the range of effects that remain compatible with the data.

Change From Baseline at 2 Weeks in Low Back Extension Range of Motion

• 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:
  • Spinal Manipulative Therapy: mean -1.50 versus -0.07 on control; difference -1.43 (95% CI -7.11 to 4.25), standardized effect d = -0.14; z-test p = 0.622.
  • Enhanced Sham Spinal Manipulative Therapy: mean 1.26 versus -0.07 on control; difference 1.33 (95% CI -3.38 to 6.04), standardized effect d = 0.15; z-test p = 0.580.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Spinal Manipulative Therapy and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Enhanced Sham Spinal Manipulative Therapy and the control. The interval gives the range of effects that remain compatible with the data.

Change From Baseline at 2 Weeks in Low Back Right Sidebending Range of Motion

• 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:
  • Spinal Manipulative Therapy: mean 0.92 versus -0.19 on control; difference 1.11 (95% CI -2.26 to 4.48), standardized effect d = 0.18; z-test p = 0.519.
  • Enhanced Sham Spinal Manipulative Therapy: mean 0.63 versus -0.19 on control; difference 0.82 (95% CI -2.06 to 3.70), standardized effect d = 0.15; z-test p = 0.577.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Spinal Manipulative Therapy and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Enhanced Sham Spinal Manipulative Therapy and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcomes concern changes in low back range of motion from baseline at 2 weeks. Across the available flexion, extension, and right-sidebending results, the recalculated pairwise confidence intervals include zero and the unadjusted p-values are greater than 0.05. The sponsor-reported repeated-measures ANOVA for flexion is also listed with p > 0.05. The registry does not report sponsor analyses for extension or right sidebending. Numerical results for left-sidebending range of motion are not reported in the registry record, despite that outcome appearing in the registry’s outcome list.

As a group, these secondary results do not show a clear pairwise separation from standard sham in the posted recalculations. They should be considered alongside, but not combined with, the primary belief outcome: range of motion and treatment belief are different measures. The primary result concerns what participants believed they received at baseline; the secondary measures concern physical range-of-motion change at 2 weeks. A difference in belief does not imply a difference in range of motion, and a lack of clear separation in these posted secondary estimates does not resolve the primary endpoint.

Unadjusted secondary analyses carry less weight when many outcomes or contrasts are examined because the chance of finding at least one apparently notable result can rise as more tests are conducted. This is a general statistical concern. The record lists nine outcome measures and six analyses, but does not report a multiplicity strategy, a hierarchy of outcomes, or which comparisons were designated in advance. Without those details, isolated secondary p-values should not be treated as confirmatory evidence. The range-of-motion findings are best read as exploratory descriptions of the posted measurements, with their uncertainty and the incomplete sponsor analyses kept in view.

The registry’s stated study purpose also refers to low back pain, function, and pain sensitivity. Numerical results for those outcomes are not reported in the posted results included in the registry record. Consequently, the available secondary range-of-motion data cannot stand in for those unreported outcomes or support conclusions about them.

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

• Change From Baseline at 2 Weeks in Low Back Flexion Range of Motion
• Change From Baseline at 2 Weeks in Low Back Extension Range of Motion
• Change From Baseline at 2 Weeks in Low Back Right Sidebending Range of Motion
• Change From Baseline at 2 Weeks in Low Back Left Sidebending Range of Motion

9. Statistical Interpretation

10. Statistical Methods Explained

What does the reported overall test address?

The registry reports a chi-squared analysis across the spinal-manipulation, standard-sham, and enhanced-sham groups, with p < 0.01. In general, a chi-squared test can assess whether the distribution of a categorical outcome differs among groups. For a binary belief outcome, it evaluates whether the pattern of participants reporting that they believed they received spinal manipulative therapy is compatible with the same underlying proportion across the groups included in the test. The registry does not provide the test statistic or details sufficient to reconstruct the sponsor’s analysis.

An overall test and a pairwise contrast answer different questions. The overall test concerns whether the set of groups differs in its outcome distribution. A pairwise comparison focuses on a particular contrast, such as spinal manipulative therapy versus standard sham. The registry’s posted p < 0.01 is an overall result; it should not be assigned to either pairwise contrast. The pairwise risk differences and their p-values described elsewhere are simple unadjusted recalculations from the posted counts, not the reported chi-squared analysis.

What is a risk difference?

General explanation: a risk difference expresses the difference between two groups’ proportions experiencing or reporting an outcome. For this endpoint, the outcome is believing that the participant received spinal manipulative therapy. A positive risk difference for the comparison groups as ordered in the recalculation means that the belief proportion was higher in the named comparison arm than in standard sham. This measure remains on the proportion scale and is generally easier to interpret as an absolute contrast than a relative measure. It does not adjust for other variables.

The recalculations use the posted counts: 19 of 28 participants in the spinal-manipulation group and 10 of 27 in standard sham, and 21 of 27 in enhanced sham and 10 of 27 in standard sham. Their unadjusted p-values are 0.022 and 0.002, respectively. The registry does not report adjusted pairwise analyses for these comparisons. In a randomized study, an unadjusted group contrast can be informative, but the posted information does not establish whether the sponsor used additional covariates, a different analysis population, or a multiplicity adjustment for its own work.

What does a confidence interval communicate?

General explanation: a confidence interval describes the range of effect estimates compatible with the data under the method’s assumptions, and it conveys uncertainty in an estimate. A wider interval indicates less precision than a narrower interval on the same scale. For a risk difference, an interval that excludes zero is conventionally consistent with evidence of a nonzero difference at the corresponding confidence level, when the method’s assumptions and testing framework apply. A confidence interval is not a guarantee that the true effect lies within its endpoints, nor does it account automatically for design limitations, missing data, or multiple testing.

The pairwise recalculated confidence intervals are 95% intervals. Both reported risk-difference intervals lie above zero. That observation aligns with the unadjusted pairwise p-values, but it does not make those recalculations equivalent to the sponsor’s overall test. The registry record does not report confidence intervals for the sponsor’s chi-squared result.

Why is the secondary analysis different?

The flexion outcome is continuous: it is change from baseline in range of motion, measured in degrees at 2 weeks. The registry reports means and standard deviations by group, and lists a repeated-measures ANOVA for the four groups with p > 0.05. In general, analysis of variance compares group means while accounting for the structure specified by the analysis. A repeated-measures approach can be used when measurements are related within participants over time. The record does not give enough detail to determine the exact model, covariance assumptions, or time points included in the sponsor’s model.

The separately recalculated mean differences contrast each sham-related group with standard sham using posted summary statistics. These simple comparisons are not the same as the reported repeated-measures ANOVA. The registry does not report sponsor p-values for the extension or right-sidebending outcomes. This means the available secondary evidence is incomplete for comparing all listed outcomes under a common analysis framework.

What does the planning illustration mean?

General explanation: a sample-size calculation estimates how many participants a future study might need under specified assumptions. The listed calculations use the observed effect as a planning reference and consider smaller fractions of that effect. They are illustrations, not evidence about how the original trial was designed or about the probability that the original trial detected an effect. Statistical power is a design property under stated assumptions, not a retrospective measure of whether a result is true. The original trial’s sample-size assumptions and justification are not reported in the registry record.

For these non-time-to-event outcomes, the planning figures are participants per arm. The calculations assume a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect equal to the stated fraction of the observed effect. In general, planning to detect a smaller effect requires more participants, all else held constant. The planning display therefore needs to be read as a set of hypothetical future-design scenarios rather than as part of the sponsor’s reported inferential analysis.

11. Confidence Intervals and Precision

The primary outcome percentages are based on modest group counts: 28 participants for spinal manipulative therapy and 27 for each sham group. With group sizes of this scale, an estimate can be sensitive to the reported belief of a small number of participants. Percentages alone do not show that uncertainty, so the pairwise recalculated confidence intervals help describe how precisely the group contrasts are estimated from the posted counts.

For spinal manipulative therapy compared with standard sham, the 95% confidence interval for the recalculated risk difference runs from 0.057 to 0.559. For enhanced sham compared with standard sham, it runs from 0.167 to 0.648. Each interval lies above zero, while both also cover a range of possible positive differences. The intervals are not especially narrow, so the estimates do not pinpoint a single precise difference. They are unadjusted recalculations and should not be confused with intervals from the sponsor’s overall chi-squared analysis, for which the registry does not report an interval.

These intervals reflect sampling uncertainty under the recalculation method. They do not resolve uncertainty about how the outcome was measured, the masking process, the handling of missing data, or whether participants were analyzed according to their randomized groups. Those details are not reported in the registry record. The intervals also do not incorporate adjustment for multiple comparisons. Thus, their apparent exclusion of zero should be interpreted as pairwise unadjusted statistical evidence, not as a complete account of all uncertainty around the study’s conclusions.

The primary endpoint is a baseline belief report, and its precision should be considered separately from the precision of secondary outcomes. For flexion, extension, and right sidebending, the registry posts group means and standard deviations and recalculated mean-difference intervals, but these continuous outcomes do not measure the same construct as treatment belief. Statistical precision in a range-of-motion estimate cannot establish precision in pain, function, or pain sensitivity, for which the relevant numerical results are not reported in the registry record.

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 events. 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 set at the stated fraction of the observed effect: 100%, 75%, or 50%. The trial’s own original sample-size assumptions and justification are not reported in the registry record.

The 80% power column gives the hypothetical participants per arm under which the calculation targets an 80% chance of detecting the specified effect, if the assumptions hold and the effect is present. The 90% power column uses a higher target chance of detection and therefore generally calls for more participants per arm for the same assumed effect. These are design targets, not guarantees about a future result.

Reading across the effect scenarios, the smaller assumed effect requires more participants per arm than the larger assumed effect, all else held constant. For example, planning for 75% or 50% of the observed effect uses more participants per arm than planning for 100% of the observed effect. The numerical requirements differ by comparison and endpoint because the calculations use their respective observed effects and variability.

These figures are planning illustrations, not observed power. They do not describe the original trial’s design process and do not estimate the chance that the posted result is correct. The observed effect used as a planning reference is itself uncertain, particularly with the posted group sizes, so the calculations should be read as conditional scenarios rather than fixed requirements for every future study.

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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.370; treatment proportion p₁ = 0.679; average p̄ = 0.524.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.7063 = 1.3842.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6718 = 0.5654.
4. n = (1.3842 + 0.5654)² / (0.3082)² = 40.0, rounded up to 41 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
p0 <- 0.37037037037037                          # control proportion
p1 <- 0.678571428571429                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(1168999)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 41 (80% power), 54 (90% power)
 75% of observed effect: n per arm = 73 (80% power), 97 (90% power)
 50% of observed effect: n per arm = 163 (80% power), 217 (90% power)
power.prop.test: 40 
Simulated power at n = 41 per arm: 0.829 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-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. Analyses Reported by the Sponsor

The registry’s reported primary analysis is a chi-squared comparison across spinal manipulative therapy, standard sham spinal manipulative therapy, and enhanced sham spinal manipulative therapy, with p < 0.01. This is the sponsor-reported result recorded for the primary outcome. It is an overall group test, not a reported pairwise test of either active manipulation versus standard sham or enhanced sham versus standard sham.

The pairwise risk differences, confidence intervals, and p-values are simple unadjusted recalculations from the posted group counts. They offer a transparent way to describe two particular contrasts but do not reproduce or supersede the sponsor’s overall analysis. The registry does not provide enough detail about the sponsor’s analysis to determine the exact test implementation, the analysis population, or whether other adjustments were used. No discrepancy is flagged between the posted results and the recalculations, but that does not make their analytic questions identical.

The primary outcome’s posted proportions and counts are consistent with the groups used in the recalculated contrasts. Even so, the sponsor’s result should be interpreted according to the analysis actually reported in the registry: an overall chi-squared result across the three named groups. Pairwise recalculated evidence is supplementary and unadjusted. The registry does not report sponsor-reported pairwise estimates or confidence intervals for the primary endpoint.

For flexion, the registry also records a sponsor-reported repeated-measures ANOVA with p > 0.05. The recalculated pairwise mean differences are distinct analyses, not a replacement for that model. For extension and right sidebending, the record does not list a sponsor-reported analysis result. The registry record does not report a comparable sponsor analysis for those outcomes.

15. Multiplicity, Missing Data and Analysis Populations

The primary outcome has a reported overall chi-squared test and two natural pairwise contrasts that can be recalculated from the posted counts. The registry does not report whether pairwise tests were part of the prespecified analysis, whether any adjustment for multiple comparisons was planned, or whether the overall test was followed by a defined sequence of contrasts. That information matters because examining several outcomes and comparisons can increase the chance of observing a small p-value by chance. The recalculated pairwise p-values are unadjusted and should be interpreted with that limitation.

The record lists nine outcome measures and six analyses, while the posted numerical secondary results include flexion, extension, and right sidebending. The registry also names left sidebending, but numerical results for it are not reported in the registry record. The multiplicity plan, outcome hierarchy, and any prespecified distinction between confirmatory and exploratory analyses are not reported in the registry record. Without them, the relative priority of the various outcome tests cannot be established from the registry alone.

Missing-data handling is also not reported in the registry record. The posted primary outcome groups have 28, 27, and 27 participants, while the natural-history primary outcome entry has a group size of 0 and no value. The registry describes a natural-history group and reports 28 participants at risk in the safety information. The record does not explain why the natural-history primary outcome is absent, whether participants were excluded from that endpoint, or how any missing responses were handled. The secondary outcome group counts also differ by measure, and the reasons for those counts are not reported.

The analysis population is not reported in sufficient detail to determine whether the primary and secondary results follow intention-to-treat, per-protocol, or another approach. The registry record does not describe exclusions after randomization, adherence handling, imputation, or sensitivity analyses for missing data. These omissions limit assessment of whether the posted group comparisons preserve the benefits of randomization and how robust the results are to incomplete outcome information.

16. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The registry reports zero serious adverse events in each of the four listed groups: spinal manipulative therapy, sham spinal manipulative therapy, enhanced sham spinal manipulative therapy, and natural history. The serious-event counts at risk are 28, 27, 27, and 28, respectively. These entries describe what was recorded in the registry; they do not establish that no other safety events occurred or that all possible harms were actively assessed and reported.

The registry also reports zero other adverse events in each group, with the same group counts at risk. No serious-event terms are listed. The record does not provide additional details about event definitions, severity categories, assessment methods, duration of follow-up for safety, or whether events were judged related to the intervention. Death counts are not reported in the safety record.

Zero recorded events in these groups is not proof that risk is absent. With the reported group sizes, the safety entries describe the observed record rather than establishing the frequency of rare events or the comparative safety of the interventions. The natural-history safety group is listed even though its primary outcome entry has no participants or result; these are separate registry entries and should not be conflated.

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

The primary result describes participants’ beliefs about treatment assignment at baseline. The posted percentages differ across the spinal-manipulation, standard-sham, and enhanced-sham groups, and the sponsor reports an overall chi-squared result with p < 0.01. The finding is relevant to the credibility of the sham procedures as experienced by participants, but it is not a direct measure of pain relief, functional improvement, or physiological response.

The standard-sham group had a lower posted percentage believing they received spinal manipulative therapy than either of the other groups. The enhanced-sham group had the highest posted percentage. These observations can inform consideration of whether the sham procedures produced similar treatment beliefs, but the registry does not report a direct expectation score or enough detail to determine why participants answered as they did. The contrast between sham groups therefore should not be interpreted as proof that the expectation-setting statement caused a particular belief response.

The primary assessment is recorded at baseline, while the posted range-of-motion secondary outcomes concern change from baseline at 2 weeks. Those outcomes address different questions. The available secondary findings do not provide clear pairwise separation from standard sham in the recalculations, and pain, function, and pain-sensitivity results are not reported in the registry record. The data therefore do not support a broad conclusion about the clinical effects of spinal manipulation or sham procedures.

The recalculated pairwise results are unadjusted and distinct from the sponsor’s overall analysis. Their confidence intervals convey uncertainty, and the registry does not report the multiplicity plan, detailed missing-data approach, or analysis-population definition. Those gaps matter when judging the strength and generalizability of the statistical evidence. The appropriate reading is narrow: the registry reports different baseline beliefs across the three groups in its overall test, while the information available does not establish treatment effects on the other clinical outcomes named in the study purpose.

18. Why This Trial Matters Statistically

This trial raises a statistical design issue central to studies of hands-on interventions: the control procedure needs to be credible enough that group differences are not simply differences in participants’ beliefs about what treatment they received. Measuring belief can help assess this aspect of the comparison. The study’s inclusion of a standard sham and an enhanced sham also makes clear that the words accompanying a procedure may be relevant to how participants interpret treatment assignment.

The primary endpoint is therefore useful for understanding an aspect of the trial’s measurement context, even though it is not a clinical outcome. Statistical conclusions about pain or function can be difficult to interpret if participants’ treatment beliefs differ across groups, particularly when outcomes include participant reports. A belief outcome cannot by itself show that masking succeeded or failed in every respect, but it makes the credibility question empirically visible.

The record also illustrates why overall and pairwise analyses should be kept distinct. The sponsor’s chi-squared result addresses the three posted manipulation-related groups together, whereas the recalculated contrasts focus on each sham group against standard sham. Both can be informative, but they answer different questions and have different implications for multiplicity. The same distinction applies to the sponsor’s repeated-measures analysis of flexion and the separately recalculated mean differences.

Finally, the registry provides a useful case for reading outcome records cautiously: a completed randomized study can have a clear primary belief result while leaving important details about missing data, analysis populations, multiplicity, and other stated clinical outcomes unreported. Statistical interpretation depends not only on p-values but also on what was measured, which comparisons were planned, and how precisely and completely results were recorded.

19. 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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

The registry record does not report the allocation sequence method, the identity of the masked parties, or detailed procedures for maintaining masking. Although the study is labeled single-masked, the record does not explain who was masked or how masking was assessed beyond the primary belief outcome. This limits evaluation of the design features that support interpretation of the sham comparison.

The natural-history arm is described as receiving no intervention and appears in the safety record and secondary range-of-motion results, but the primary endpoint lists a group size of 0 and no value for it. The registry does not explain this difference. The posted primary result therefore supports comparison among the three groups with values, not a primary-outcome comparison including natural history.

The primary endpoint is a baseline belief report. It does not directly quantify expected treatment benefit, and the registry does not report a separate expectation measure. It is also not a post-treatment clinical outcome. The study purpose names low back pain, function, and pain sensitivity, but numerical results for these outcomes are not reported in the registry record. Left-sidebending range-of-motion results are also not reported numerically, although that outcome is listed.

Important analysis details are absent, including the original sample-size justification, multiplicity plan, analysis-population definition, and handling of missing data. The sponsor’s primary test is reported only as a chi-squared result with a p-value; a test statistic and confidence interval are not recorded. Pairwise primary comparisons and secondary mean differences described in the posted results are unadjusted recalculations, not sponsor-reported pairwise analyses. These limitations constrain how broadly the findings can be interpreted.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: The Mechanisms of Manual Therapy in the Treatment of Low Back Pain — NCT01168999.
• Registry record last updated 2015-10-28; status last verified 2015-10.
• Results first posted 2013-12-23.
• 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.

23. Record Summary

The registry describes a completed randomized, single-masked, parallel-group Phase 1 and Phase 2 study sponsored by the University of Florida, with enrollment of 110. Its primary outcome assesses the percentage of participants who believed they had received spinal manipulative therapy at baseline. Posted values are 67% for spinal manipulative therapy, 37% for standard sham, and 78% for enhanced sham; the natural-history group has no primary value. The sponsor reports an overall chi-squared result of p < 0.01 across the three groups with posted primary results.

Simple unadjusted recalculations compare each sham-related group with standard sham. Secondary numerical results concern changes in flexion, extension, and right-sidebending range of motion at 2 weeks; the registry reports a repeated-measures ANOVA result for flexion, while sponsor analyses for extension and right sidebending are not reported. Numerical results for pain, function, pain sensitivity, and left-sidebending range of motion are not reported in the registry record. The record also does not report the original sample-size rationale, multiplicity strategy, missing-data approach, or analysis-population definition.