Foot Orthoses and Elderly Women With Osteoporosis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Foot Orthoses and Elderly Women With Osteoporosis (NCT01508169), a randomized na study. The primary outcome is Berg Balance Scale (BBS).

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group study with no masking. The study status is completed. The listed sponsor is University of Campinas, Brazil. The recorded start was 2011-04 and the primary completion was 2011-10. The phase is listed as NA, which is a registry classification rather than a treatment-comparison result.

The study concerned women with osteoporosis aged 60 or above who were receiving outpatient care. The intervention was a foot orthosis, while the control group received no foot intervention. The arm descriptions state that 47 women were assigned to each group. The registry enrollment is 94, while the posted outcome summaries report 44 participants in the foot-orthosis group and 45 in the control group. The reason for the different counts is not reported in the registry record; the summaries do not establish why some assigned participants are absent from the posted outcome counts.

The primary endpoint was the BBS score at 4 weeks. The secondary outcomes posted at the same timeframe were Numeric Pain Scale and Manchester Foot and Pain Disability Index (MFPDI). Although the registry identifies four outcome measures, only two secondary outcome summaries are included in the posted results. The other measure or measures and their results are not reported in the registry record.

The registry describes a pilot study as part of its sample-size rationale and says that 45 subjects in each group were considered satisfactory for identifying group differences in the listed variables with 80% power and a significance level of 5 %. The protocol details, including the original statistical analysis plan and the justification underlying the initial enrollment, 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.

Before assignment: From the 242 patients considered eligible, 148 were not included due exclusing criteria (compromised skin integrity of the lower limbs, autoimmune rheumatic diseases, vestibular symptoms, central nervous system pathologies, peripheral neuropathy, use of insoles in the last month, previous foot surgery, inability to attend the reevaluations).

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: A pilot study (with 14 subjects wearing insoles and 15 controls) was conducted.To identify differences between groups for the variables (Berg, TUG, pain, disability) with a 80% power and a significance level of 5 % the number of 45 subjects in each group was considered satisfactory.

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 Berg Balance Scale (BBS), measured over 4 weeks.

The primary endpoint was the Berg Balance Scale (BBS) score at 4 weeks. The BBS assesses the ability to maintain balance while performing 14 movements related to everyday activities, including transferring, standing unsupported, rising from sitting to standing, tandem standing, turning 360° and single-leg standing. Each movement is rated on an ordinal scale from 0 to 4, and the total score ranges from 0 to 56. A smaller score indicates worse balance.

The BBS is used as a structured measure of balance performance across several tasks rather than as a report of a single movement. The registry also gives broad descriptions of score ranges in relation to mobility and assistance, but it does not report a threshold for a clinically important difference between groups. The outcome is summarized using group means and standard deviations, even though its individual movement ratings are ordinal. Such a summary describes average scores and their spread; it does not show how many participants had a particular level of function or how scores changed for each individual.

The four-week BBS comparison addresses the registered balance question at that follow-up. It does not, by itself, establish how long any difference may persist or how the result relates to outcomes not measured or not reported in the registry record.

7. Results Posted in the Registry

• Foot Orthosis: mean 50.68 versus 43.13 on control; difference 7.55 (95% CI 5.35 to 9.75), standardized effect d = 1.42; z-test p = <0.001.

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.

Numeric Pain Scale

• 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:
  • Foot Orthosis: mean 1.68 versus 4.20 on control; difference -2.52 (95% CI -3.67 to -1.37), standardized effect d = -0.90; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Foot Orthosis than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Manchester Foot and Pain Disability Index(MFPDI)

• 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:
  • Foot Orthosis: mean 11.48 versus 22.64 on control; difference -11.16 (95% CI -14.31 to -8.01), standardized effect d = -1.46; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Foot Orthosis than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The posted secondary outcomes are Numeric Pain Scale and Manchester Foot and Pain Disability Index (MFPDI), both measured at 4 weeks. Across these outcomes, the group summaries follow a direction consistent with the primary BBS pattern: lower average reported pain and disability scores in the Foot Orthosis group than in the Control Group. The registry does not fully describe the score interpretation or a clinically important difference for these measures, so the direction of the mean contrast should not be equated with a quantified level of practical importance.

These measures address aspects of the study objective that are related to, but distinct from, balance. Their pattern can add context to the primary outcome, but pain and disability scores do not directly validate a balance result. Each outcome also represents a separate statistical comparison. The registry lists no reported analyses for the secondary outcomes, and the posted comparisons are unadjusted.

General: when several outcomes are examined, the chance of obtaining at least one apparently strong result by chance can increase unless the analysis accounts for the number and structure of the comparisons. The registry record does not report a multiplicity adjustment or a prespecified hierarchy for interpreting these outcomes. Consequently, the secondary results carry less inferential weight than a single prespecified primary endpoint and are best read as supportive descriptive evidence, not as independent proof or a replacement for the primary comparison.

The relationship among balance, pain, and disability cannot be established from these group summaries. The registry does not report an analysis of associations between outcomes or individual changes over time. It is therefore not possible to tell whether participants with different balance scores also had corresponding pain or disability scores, or whether any changes in one measure accompanied changes in another.

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

• Numeric Pain Scale
• Manchester Foot and Pain Disability Index(MFPDI)

9. Statistical Interpretation

10. Statistical Methods Explained

The registry presents continuous outcomes as means and standard deviations. The comparisons are unadjusted calculations from the posted group summaries. No sponsor-reported analysis is listed. The registry record does not report a detailed statistical analysis plan, the specific testing procedure used by the investigators, or any adjustment for baseline variables.

What does a mean difference describe?

For the primary outcome, the mean difference is defined as the Foot Orthosis group mean minus the Control Group mean. A positive estimate therefore means the orthosis group had the higher mean BBS score. Since the registry says that smaller BBS scores indicate worse balance, the positive direction corresponds to a higher average balance score in the orthosis group. This is a comparison of group averages; it does not say that every participant had a higher score or that every participant changed in the same way.

A standard deviation describes how spread out individual scores are around a group mean. It is not the same as the uncertainty in the estimated mean, and it is not a confidence interval. The posted BBS standard deviations are 4.18 for the orthosis group and 6.24 for the control group. Differences in spread can matter when estimating how precisely group means and their contrast are known.

How should a confidence interval be understood?

General: a confidence interval expresses the statistical uncertainty around an estimate under the calculation's assumptions. It gives a range of values compatible with the observed data and method; it is not a range containing a stated proportion of individual participants. For the BBS mean difference, the interval runs from 5.348 to 9.752. Because the interval is above zero, it supports a positive unadjusted average difference under the calculation. The interval does not account for unreported sources of bias, missing outcomes, or choices not included in the calculation.

What does the p-value convey?

General: a p-value describes how unusual data at least as discrepant as those observed would be if a specified null hypothesis and statistical model were true. It does not give the probability that the null hypothesis is true, and it does not measure clinical importance. The primary comparison is reported as p < 0.001. The registry does not state the investigators' complete testing procedure or whether this value was part of a prespecified analysis.

Why can outcome distributions matter?

General: means and standard deviations are most informative when the summary adequately represents the outcome distribution. The BBS is assembled from ordinal ratings, but the posted result treats its total score as a continuous measure summarized by a mean and standard deviation. The registry does not provide the individual-level distribution, so it is not possible to assess whether the mean captures features such as clustering near the scale limits or skewness. No alternative summary or distributional check is reported in the registry record.

General: over-dispersion means that observations vary more than a statistical model expects. When that occurs, standard errors based on the narrower model may understate uncertainty. The posted record does not describe an over-dispersion assessment, and the continuous-outcome summaries do not establish that over-dispersion was a concern. More generally, model assumptions should be considered alongside estimates rather than inferred from a small p-value.

What is and is not known about the analysis?

The posted comparison is unadjusted and based on group summary statistics. No reported analyses are listed for the secondary outcomes, and no detailed analysis methods are reported in the registry record. The record does not specify how missing outcomes were handled, whether analyses followed assigned groups, whether there were interim analyses, or how multiple outcomes were addressed. These are not details that can be reconstructed from group means and standard deviations.

The numerical comparison is therefore useful as a transparent summary of the posted group results, but it should not be mistaken for a full account of the investigators' analysis. Because the registry does not flag a discrepancy, there is no stated conflict between the summary-based calculation and a sponsor analysis in the posted record. The absence of a listed sponsor analysis still means that its methods cannot be compared with the unadjusted calculation.

11. Confidence Intervals and Precision

The primary mean difference is 7.55 BBS points, with a 95% confidence interval from 5.348 to 9.752. This interval gives a sense of statistical precision for the unadjusted difference estimated from the posted group summaries. Its endpoints are both above zero, while the interval's width indicates that the exact size of the mean difference is not known with certainty.

Precision is distinct from clinical importance. The registry record does not report a threshold for a clinically important BBS difference, so the interval cannot be classified as demonstrating a meaningful benefit on that basis. The interval also reflects only the uncertainty represented by the calculation. It does not capture possible bias from unmasked assessment, incomplete outcome reporting, or other design and analysis issues that are not quantified in the registry.

The outcome means are based on 44 participants in the orthosis group and 45 in the control group. Those counts differ from the group assignment counts stated in the arm descriptions. The reason is not reported in the registry record, so the potential effect of the missing outcome information on precision or bias cannot be assessed from the posted summaries. A confidence interval cannot resolve that uncertainty.

The p-value, p < 0.001, is consistent with evidence against a zero mean difference under the unadjusted calculation, but it is not a substitute for the interval. The interval is more informative about the range of estimates compatible with the calculation, while neither the p-value nor the interval addresses multiplicity or unreported analysis choices.

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 sample-size figures are planning illustrations based on fractions of the observed effect, not a record of the trial's original sample-size calculation. For these continuous outcomes, the figures are participants per arm, not total event counts. The planning 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 the stated fraction of the observed effect. The original trial's design assumptions beyond what the registry states are not reported in the registry record.

The 80% power column gives the planned number of participants per arm for a calculation with 80% power under those assumptions and for the effect size specified in that row. The 90% power column gives the corresponding number per arm for 90% power. In plain terms, power is the chance that a study will detect an effect of the assumed size at the stated significance level if that effect is present and the planning assumptions hold. The table is an illustration, not a guarantee of a future study's result.

Rows planning for 100%, 75%, and 50% of the observed effect show how the illustrative requirement changes as the assumed effect becomes smaller. Smaller effects need more participants per arm to reach the same power under the same assumptions. These figures are not observed power for the completed trial; they are planning scenarios derived from the observed estimate. They should not be read as evidence that the trial was designed around those effect sizes or that any particular future sample size is sufficient without considering its own design and analysis.

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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 7.550; pooled standard deviation σ = 5.322.
2. n = 2 × (1.96 + 0.842)² × 5.322² / 7.550² = 7.8, rounded up to 8 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
delta <- 7.55                      # observed difference in means
sigma <- 5.3224395927423                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1508169)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 8 (80% power), 11 (90% power)
 75% of observed effect: n per arm = 14 (80% power), 19 (90% power)
 50% of observed effect: n per arm = 32 (80% power), 42 (90% power)
power.t.test: 8.9 
Simulated power at n = 8 per arm: 0.757 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-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. Multiplicity, Missing Data and Analysis Populations

The registry identifies the BBS as the primary outcome and lists Numeric Pain Scale and MFPDI as secondary outcomes. It also reports four outcome measures overall, but only two secondary summaries are posted. The other outcome measure or measures are not reported in the registry record. The record does not describe a prespecified hierarchy among the outcomes, a multiplicity adjustment, or a plan for interpreting several tests together.

General: multiplicity arises when researchers make several statistical comparisons. Without an adjustment or a clearly prespecified strategy, the chance of at least one result appearing statistically notable by chance can rise. This is why the secondary results should be interpreted with more caution than a clearly designated primary result. The posted secondary comparisons are unadjusted, and no analyses are listed for them beyond the summary-based comparisons.

The outcome summaries also do not establish how missing data were handled. The arm descriptions state that 47 women were assigned to each group, whereas the BBS and secondary outcome summaries report 44 and 45, respectively. The reason for the difference, the outcomes of participants not included in the summaries, and any imputation or sensitivity analyses are not reported in the registry record. It is therefore not possible to determine whether the posted summaries represent all randomized participants or to assess the effect of missing outcomes on the estimates.

The record does not state whether the analysis followed original assignment regardless of intervention received, whether participants were excluded for protocol deviations, or how outcome data were collected when a measurement was unavailable. These analysis-population details are not reported in the registry record. Nor are interim analyses, stopping rules, or a complete statistical analysis plan reported. Their absence from the record should not be interpreted as proof that a particular procedure was or was not used.

15. 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 4.5% reporting threshold.

Most frequent non-serious adverse event terms

For serious adverse events, the registry lists 47 participants at risk in the Foot Orthosis group and 0 affected; the Control Group has 0 listed at risk and 0 affected. Because the control group has no participants recorded as at risk in this safety summary, the figures do not provide a meaningful between-group comparison of serious adverse events. The record lists no serious adverse event terms.

For other adverse events, the Foot Orthosis group has 47 listed at risk and 6 affected. The Control Group has 0 listed at risk and 0 affected. These counts describe what the safety fields record; the control group's zero at-risk count prevents a like-for-like comparison. The registry does not explain why the safety at-risk counts differ between groups or how adverse events were collected.

Deaths are not reported in the registry record. These figures should therefore be read as registry reporting, not as evidence that events were comprehensively monitored or that risks can be compared between groups. The record does not provide further details about the nature, timing, severity, or relatedness of the other adverse events.

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

The posted results show a higher average BBS score at 4 weeks in the Foot Orthosis group than in the Control Group. The unadjusted mean difference is 7.55 points, and its 95% confidence interval is above zero. The result describes a group-average contrast in this trial; it does not describe the experience of every participant, establish a clinically important threshold, or show how durable the difference might be.

The finding does not, by itself, establish a causal effect free of bias. Random assignment is an important feature of the design, but the registry lists no masking and does not explain the difference between assigned group sizes and outcome-summary counts. The record also does not report a complete analysis plan, missing-data approach, or multiplicity strategy. Those limitations affect how confidently the numerical estimate can be interpreted.

The results do not establish that all women with osteoporosis would have the same outcome. The study population is described as women aged 60 or above receiving outpatient care at a specific clinic. The registry does not report a threshold for meaningful BBS change, detailed participant characteristics beyond the inclusion description, or follow-up beyond the stated 4 weeks for these outcomes. Broader applicability and longer-term outcomes are therefore not established by these summaries.

The secondary summaries concern pain and disability and point in a direction consistent with the primary group pattern, but they are unadjusted and carry less inferential weight. Safety information is also incomplete for comparison because the control group is listed with no participants at risk. The results can be understood as posted statistical findings, not as medical advice or a conclusion about what an individual should do.

17. Why This Trial Matters Statistically

This trial illustrates several statistical issues that matter when reading clinical results. First, the primary outcome is a score with ordinal item ratings, yet the posted comparison summarizes group means and standard deviations. That approach makes the average contrast easy to state, while leaving the individual score distribution and potential scale limitations unshown.

Second, random assignment and the reported analysis counts should be considered together. The arm descriptions record 47 assigned participants in each group, whereas the posted outcome summaries include 44 and 45. Without an explanation of the difference or a missing-data analysis, readers cannot determine how the outcome summaries relate to all assigned participants.

Third, the primary estimate is accompanied by a confidence interval and a p-value, allowing readers to consider both the direction and statistical uncertainty of the comparison. These measures do not answer whether the difference is clinically important, because the registry does not state a meaningful-difference threshold. Nor do they account for design limitations that are not represented in the calculation.

Finally, the registry includes secondary outcomes and sample-size illustrations but does not report a full analysis plan or multiplicity strategy. This distinction matters: a planning illustration based on an observed effect is not the original design justification, and several unadjusted outcomes do not carry the same inferential weight as a clearly specified primary comparison. Reading the estimates alongside what is not reported helps keep statistical evidence separate from stronger claims that the record cannot support.

18. 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 registry record leaves several trial-specific uncertainties. The group descriptions state that 47 women were assigned to each arm, while the posted primary and secondary outcome summaries include 44 in the Foot Orthosis group and 45 in the Control Group. The reason for this difference and the handling of missing measurements are not reported in the registry record. The effect of missing outcomes on the estimates cannot be assessed from the available summaries.

The trial is listed as unmasked. The registry does not explain whether outcome assessment was performed independently of treatment assignment or whether participants and assessors knew the allocation. This is relevant because the primary measure involves performance on balance tasks, while the secondary measures include reported pain and disability.

The arm description for the orthosis is incomplete in the registry record, and details of intervention use or adherence are not reported. The record does not describe the full statistical analysis plan, an adjustment for multiple outcomes, analysis populations, interim analyses, or sensitivity analyses. It also lists four outcome measures but posts only two secondary outcome summaries.

The results address a 4-week follow-up. Longer-term outcomes are not reported in the registry record. The record does not provide a clinically important difference threshold for the BBS or the secondary scales, making it difficult to judge practical importance from the estimates alone. The safety summary lists no participants at risk in the control group, which limits comparison of adverse events; further event details are not reported.

These limitations do not erase the posted mean differences, but they constrain interpretation of precision, possible bias, and applicability beyond the participants and follow-up described in the record.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Foot Orthoses and Elderly Women With Osteoporosis — NCT01508169.
• Registry record last updated 2012-04-06; status last verified 2012-02.
• Results first posted 2012-04-06.
• 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.

22. Record Summary

The completed study was a randomized, parallel-group trial with no masking, comparing a foot orthosis with no foot intervention among elderly women with osteoporosis. The primary outcome was BBS score at 4 weeks. The posted mean was 50.68 for the Foot Orthosis group and 43.13 for the Control Group, with an unadjusted mean difference of 7.55 points (95% confidence interval 5.348 to 9.752; p < 0.001).

The record also posts 4-week Numeric Pain Scale and MFPDI summaries. These secondary comparisons are unadjusted. Group assignment counts differ from the outcome-summary counts, and the reason is not reported in the registry record. The registry does not report a full analysis plan, missing-data approach, or multiplicity strategy, and its safety summary does not permit a comparable serious-adverse-event assessment between groups.