Effect of Intraarticular Steroids on Bone Turnover in Osteoarthritis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Intraarticular Steroids on Bone Turnover in Osteoarthritis (NCT00682357), a randomized na study. The primary outcome is Change in Serum Osteocalcin.

2. Clinical Question

The clinical question concerns a biological marker and its change over a defined follow-up period, rather than a reported clinical symptom or functional outcome. The registry record lists osteoarthritis as the condition and describes serum osteocalcin change from Day 0 to Day 28 as the primary outcome. It also lists serum cortisol and testosterone as secondary outcomes, although testosterone results are not reported in the registry record.

The trial has three groups, but the posted primary result focuses on the difference between the low-dose and standard-dose groups. The placebo group contributes a posted mean change, but the registry record does not report a statistical comparison of that group with either steroid group. Consequently, the results do not establish how either steroid group differed from placebo. The distinction matters: a comparison between two doses addresses a different question from a comparison of steroid exposure with placebo.

3. Trial Design

This was a randomized, unmasked, parallel-group trial with an enrollment of 25 participants. The registry record marks the phase as not applicable. Participants were assigned to one of three groups: standard dose, low dose, or placebo. The posted outcome data include 10 participants in each steroid group and 5 in the placebo group. The record does not report the randomization procedure, allocation concealment, or reasons for the group sizes.

The intervention descriptions list Methylprednisolone and Lidocaine for the steroid interventions, and Placebo and Lidocaine for the placebo intervention. The arm descriptions specify Methylprednisone 80 mg and Lidocaine 20 mg for Group 1, Methylprednisolone 16 mg and Lidocaine 20 mg for Group 2, and Placebo and Lidocaine 20 mg for Group 3. The different spelling of the steroid name in the Group 1 arm description is retained as recorded. Further details about administration are not reported in the registry record.

The primary endpoint is change in serum osteocalcin from the baseline visit to Day 28, expressed as a mean with standard deviation and measured in ng/mL. Serum cortisol change over the same timeframe is posted as a secondary outcome. The trial description also lists change in testosterone as a secondary outcome, but its results are not reported in the registry record. The registry record lists four outcome measures, while posted analyses are limited: it lists no reported analyses in its analyses field and shows one comparison for the primary result and one for cortisol.

The record states that the study is completed, with a start in 2008-05 and primary completion in 2009-11. Details of the protocol, the intended analysis population, missing-data handling, and the trial's original sample-size justification are not reported in the registry record. These omissions limit how fully the design and analysis can be assessed.

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

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 Change in Serum Osteocalcin, measured over Change from Baseline Visit to Day 28.

The primary endpoint is change in serum osteocalcin from the baseline visit to Day 28. Osteocalcin is identified in the outcome description as a serum marker of bone formation. The outcome is reported as a mean change with standard deviation, in ng/mL. A change score describes movement from a participant's baseline value over the specified period, rather than the participant's Day 28 value alone.

As general context, measuring a biological marker can help researchers examine a proposed biological response to an intervention. Here, the trial background proposes that intra-articular steroids may suppress bone formation temporarily. The Day 28 endpoint therefore focuses on change over a period that the study description connects to the hypothesis about a return toward pretreatment levels within four weeks. The endpoint itself does not establish whether a change is clinically important, nor does it directly measure symptoms, joint function, or longer-term bone outcomes.

The posted arm summaries show mean changes of -2.18 for the standard-dose group, -0.45 for the low-dose group, and -1.1 for the placebo group. Their standard deviations are 2.24, 2.9, and 2.56, respectively. These summaries describe the observed changes within each group. The registry record posts an inferential comparison of low dose with standard dose, but does not report a statistical comparison between either steroid group and placebo. The endpoint should therefore be read together with the comparison that was actually posted, not as a complete assessment of all three groups against one another.

7. Results Posted in the Registry

• Group 2 - Low Dose: mean -0.45 versus -2.18 on control; difference 1.73 (95% CI -0.54 to 4.00), standardized effect d = 0.67; z-test p = 0.135.

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 in Serum Cortisol

• 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:
  • Group 2 - Low Dose: mean 0.65 versus -1.16 on control; difference 1.81 (95% CI -2.72 to 6.34), standardized effect d = 0.35; z-test p = 0.434.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Group 2 - Low Dose and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary results include serum cortisol change from baseline to Day 28. The registry record also lists change in testosterone as a secondary outcome, but testosterone results are not reported in the registry record. Thus the posted secondary evidence is incomplete relative to the outcomes listed in the trial description.

Across the reported primary and secondary comparisons, the estimates do not provide a precise distinction between the low-dose and standard-dose groups: both intervals include zero and extend across a range of possible differences. The directions of the observed mean differences are not identical in biological interpretation across osteocalcin and cortisol. These are different markers, so a pattern in one should not be treated as confirmation of a pattern in the other. The secondary result does not resolve the uncertainty in the primary osteocalcin result or establish the hypothesized time course.

The posted secondary comparison is unadjusted. As general statistical context, when several outcomes or comparisons are examined, the chance of seeing an apparently notable result by chance can increase if the analysis does not account for the number of tests. This is why unadjusted secondary results generally carry less weight than a clearly designated primary endpoint, particularly when the registry record does not report a prespecified multiplicity strategy. The record does not describe how the secondary outcomes were prioritized or how missing secondary measurements were handled.

These secondary findings are best treated as supporting descriptive information rather than independent confirmation. They may help frame questions for further study, but the registry record does not establish a comprehensive secondary analysis or document a correction for multiple testing. No additional inference about testosterone is possible from the posted results.

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

• Change in Testosterone
• Change in Serum Cortisol

9. Statistical Interpretation

10. Statistical Methods Explained

The registry record reports the primary endpoint as a continuous measure summarized by its mean and standard deviation. The table presents the mean change for each group and the posted mean difference for low dose versus standard dose. These are different kinds of information: group means describe each arm separately, while the mean difference summarizes the contrast between the two groups named in the comparison.

What the mean difference represents

For the primary comparison, the posted estimate is 1.73. It describes the low-dose group mean relative to the standard-dose group mean, using the comparison direction shown in the posted results. A positive estimate corresponds to the low-dose group's mean change being less negative than the standard-dose group's mean change. The estimate is a point estimate: it is the single best summary value in the posted comparison, but it does not convey how uncertain that value is by itself.

The same approach is used for the secondary cortisol comparison. A mean difference is useful for a continuous outcome because it stays in the original measurement units. It does not, on its own, establish whether the observed size is important in a clinical or biological sense. The registry record does not report a threshold for an important osteocalcin or cortisol difference.

Why the standard deviations matter

A standard deviation describes the spread of observations around a group mean. The primary endpoint standard deviations are 2.24 in the standard-dose group, 2.9 in the low-dose group, and 2.56 in the placebo group. As general statistical context, a mean is more informative when read alongside the variability of individual observations: participants can have changes that differ substantially from the average. Standard deviations describe that spread; they are not confidence intervals for the mean.

As general explanation, the standard error describes the estimated uncertainty in a statistic such as a mean or mean difference. It is influenced by both variability and the amount of information available. With small group sizes, estimates can remain uncertain even when a difference in observed means is present. The record's small groups and the displayed confidence intervals are relevant to that interpretation. No additional assumptions about the distribution of individual changes or the analysis model are reported in the registry record.

How to read the confidence interval

A confidence interval gives a range of values compatible with the data and the method used to calculate it. In repeated use of a method, intervals constructed in this way have their stated coverage under the method's assumptions. For an individual study, it is best read as a display of uncertainty about the estimated difference, rather than as a list of equally likely values or a guarantee that the true effect lies inside the interval.

The primary interval runs from -0.541 to 4.001. It includes zero, which represents no mean difference in the comparison scale. Its lower and upper limits span differences in opposite directions, so the data do not establish the direction of a nonzero difference. The cortisol interval also includes zero and extends across a broad range. The posted intervals are more informative about precision than a point estimate alone.

What the p-values say

The posted primary p-value is unadjusted and equals 0.135; the cortisol p-value is unadjusted and equals 0.434. As general statistical explanation, a p-value describes how unusual data at least as discrepant as those observed would be under a specified null model and analysis procedure. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect.

Because the record labels these values unadjusted, they should not be read as accounting for a family of multiple outcome or comparison tests. The registry record does not report whether a multiplicity adjustment was planned or applied. The intervals and p-values should consequently be interpreted as the posted comparison-level results, not as a fully documented confirmatory analysis plan.

Why the posted comparison matters

The trial has three arms, but the primary comparison reported is low dose versus standard dose. A three-arm study could address multiple contrasts, but only the displayed contrast is available for inferential interpretation. The placebo arm's mean and standard deviation are useful descriptive information, but they do not substitute for a placebo comparison with an estimate and uncertainty interval. The record does not report such a primary or secondary placebo contrast.

Likewise, the record does not report an adjusted model, covariate adjustment, an analysis population, or a method for missing outcome data. Those details should not be inferred from the presence of arm means and comparison statistics. The posted values allow a focused reading of the summaries and comparisons shown; they do not reveal every decision in the underlying analysis.

11. Confidence Intervals and Precision

The primary estimate is a mean difference of 1.73 for low dose compared with standard dose. Its 95% confidence interval is -0.541 to 4.001. This range includes zero and includes both a negative and a positive difference. The estimate therefore gives a direction for the observed contrast, but the interval shows that the data are compatible with a range of possible differences, including no difference on the comparison scale.

The interval is wide relative to the point estimate, which signals limited precision. In practical reading, the result should not be reduced to the point estimate alone or described as a known effect of a particular size. The posted data do not tightly locate the difference. The unadjusted p-value of 0.135 is consistent with the interval's inclusion of zero; neither statistic proves that the groups are the same.

The cortisol mean difference is 1.81, with a 95% confidence interval from -2.721 to 6.341. This interval also covers zero and allows a broad range of possible differences. As with the primary endpoint, the interval cautions against treating the observed estimate as precise evidence about the underlying group contrast.

Confidence intervals are useful because they place an estimate in the context of its uncertainty. As general explanation, a narrower interval indicates greater precision under the calculation method, while a wider interval leaves more uncertainty about the effect size. Precision depends on features such as data variability and the amount of information available. The registry record reports small group sizes, and the displayed intervals show that the comparisons remain uncertain. The record does not report confidence intervals for the placebo contrasts, so no interval-based precision assessment can be made for those comparisons.

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 table is a planning illustration based on the observed low-dose versus standard-dose effect, not the trial's own original design assumptions. For these continuous outcomes, the listed sample sizes are participants per arm, not total events. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to the stated fraction of the observed effect. The trial's original sample-size justification is not reported in the registry record.

The 80% power column gives the illustrative number of participants per arm for a design with an 80% chance of detecting the specified effect under the stated assumptions, if that effect is the true one and the analysis assumptions hold. The 90% power column gives the corresponding per-arm planning figure for a design with a 90% chance under those same assumptions. These percentages describe the planned operating characteristics of hypothetical future studies; they do not describe the probability that this completed study found a true effect.

The rows vary the effect used for planning: 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. The table shows that planning for smaller effects requires more participants per arm. For the primary comparison, the displayed values are 36 and 48 participants per arm at 100% of the observed effect, 63 and 84 at 75%, and 141 and 189 at 50%, for the 80% and 90% columns respectively. The cortisol planning figures are also displayed in the table. These are illustrations based on observed estimates, which may themselves be uncertain. This is not observed power.

The table should not be treated as a reconstruction of the original protocol: the registry record does not report the trial's own design assumptions or sample-size justification. The calculated curve and table are alternative views of this same planning exercise, not additional trial outcomes.

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 = 1.730; pooled standard deviation σ = 2.591.
2. n = 2 × (1.96 + 0.842)² × 2.591² / 1.730² = 35.2, rounded up to 36 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 <- 1.73                      # observed difference in means
sigma <- 2.5911001524449                     # 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(682357)
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 = 36 (80% power), 48 (90% power)
 75% of observed effect: n per arm = 63 (80% power), 84 (90% power)
 50% of observed effect: n per arm = 141 (80% power), 189 (90% power)
power.t.test: 36.2 
Simulated power at n = 36 per arm: 0.798 (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 record identifies change in serum osteocalcin as the primary outcome and lists change in testosterone and change in serum cortisol among the secondary outcomes. It also lists four outcome measures overall. The posted results include the primary osteocalcin summaries and comparison, and a cortisol summary and comparison; testosterone results are not reported in the registry record. The record does not explain the status or results of the other outcome measure.

The comparisons displayed are labelled unadjusted. The registry record does not report whether a multiplicity strategy was specified in the protocol, whether any correction was applied elsewhere, or how the primary and secondary tests were organized into a confirmatory testing plan. As general statistical context, testing several outcomes or contrasts without accounting for multiplicity can make chance findings more likely across the set of tests. This is one reason to put greater emphasis on the designated primary result and to regard unadjusted secondary findings as less conclusive.

Missing-data handling and analysis populations are also not reported in the registry record. The arm summaries show outcome sample sizes of 10, 10, and 5, matching the group counts displayed for the posted results, but this alone does not establish whether every randomized participant contributed to every analysis or how any unavailable measurement was handled. The record does not state whether the analysis followed an intention-to-treat principle, used a per-protocol population, or applied another approach. These methods should not be inferred from the displayed denominators.

The registry record also does not report the statistical analysis plan, covariates, model diagnostics, or any interim-analysis procedures. Without these details, readers cannot determine whether all analysis decisions were prespecified or whether the reported tests account for design features beyond the displayed comparison. This does not invalidate the posted summaries, but it limits their interpretation as a complete account of the planned analysis.

Accordingly, the clearest reading is confined to the displayed outcome estimates, uncertainty intervals, and unadjusted p-values. The record leaves important questions about multiplicity, missing observations, and analysis populations unanswered.

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 0% reporting threshold.

The serious adverse event figures show zero affected participants in the standard-dose group, zero in the low-dose group, and zero in the placebo group. The number at risk is 10, 10, and 5, respectively. The posted other adverse event figures also show zero affected participants in each group, with the same group counts at risk. No serious adverse event terms are listed.

These figures describe what was recorded for the groups and event categories shown. A zero count in this small study does not establish that an event cannot occur, nor does it provide a precise estimate of event risk. As general statistical context, safety estimates are more uncertain when the number of observed participants is limited, especially for uncommon events.

The death counts are not reported in the registry record. The record does not provide further detail about adverse-event definitions, collection procedures, follow-up completeness, or how events were assessed. These entries should therefore be read as the posted safety counts, not as a comprehensive assessment of all possible harms.

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

The posted primary result describes a mean difference in Day 28 osteocalcin change between the low-dose and standard-dose groups. The estimate favors a less negative mean change in the low-dose group, but the confidence interval includes zero and covers values in both directions. The result is therefore uncertain in direction and size. It does not establish a precise difference between these groups, and it does not establish that the groups are equivalent.

The placebo group's mean change is shown, but a statistical comparison with placebo is not reported in the registry record. The main posted result therefore cannot establish whether either steroid dose differs from placebo. It also cannot, by itself, confirm the background hypothesis that a steroid-related suppression is transient and returns to pretreatment levels within four weeks. The primary outcome is a change through Day 28; a detailed time course and a formal test of return to baseline are not reported.

The endpoint is a biological marker rather than a reported measure of symptoms, function, or longer-term bone outcomes. The result does not directly tell readers about those outcomes. The registry record also does not report a threshold for a clinically meaningful osteocalcin change, so the observed estimate cannot be classified by such a threshold from this record alone.

The trial's small groups, broad intervals, unadjusted comparisons, and missing details about analysis populations and missing data all constrain interpretation. The cortisol result is secondary and does not resolve the primary comparison; testosterone results are not reported in the registry record. Taken together, the posted results are informative as a limited set of observed summaries and comparisons, but they do not provide a definitive account of the biological effect across all three groups.

These findings should be understood as evidence from this completed trial, not as medical advice or a recommendation about treatment. They describe what the registry record reports for the measured outcomes and timeframe. They do not establish what would occur in other populations, with other regimens, over other follow-up periods, or for clinical outcomes not reported.

17. Why This Trial Matters Statistically

This trial illustrates the distinction between a point estimate and the uncertainty around it. The low-dose and standard-dose groups have different observed mean changes, but the confidence interval for their comparison includes zero and spans a broad range. Reading only the means or the point estimate would obscure how much uncertainty remains. The interval is central to interpreting what the study can distinguish.

It also illustrates why a three-arm design does not automatically answer every comparison a reader might want. The record shows means for standard dose, low dose, and placebo, but posts an inferential comparison only for low dose versus standard dose. Without a reported contrast and its uncertainty, the placebo mean is descriptive rather than a formal test of steroid versus placebo. The planned or intended status of other contrasts is not reported in the registry record.

The small group sizes make the precision issue especially visible. The posted confidence intervals are wide, and the sample-size illustration shows how planning for smaller effects calls for larger groups under its stated assumptions. That illustration is not evidence about the trial's original planning or about the probability that its results are true.

Finally, the record highlights the importance of reporting analysis details alongside results. Multiplicity handling, missing-data methods, analysis populations, and the original sample-size justification are not reported in the registry record. Their absence does not change the numerical summaries, but it limits assessment of how comprehensively the posted results reflect the trial's intended analysis. For biostatistical interpretation, these details are part of understanding not just the estimate, but the scope and reliability of the evidence.

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.

Several trial-specific limitations follow from the registry record. Enrollment was 25, with posted outcome groups of 10 participants in each steroid arm and 5 in the placebo arm. The small groups limit the information available for estimating between-group differences and are reflected in the broad confidence intervals. The group imbalance also means that the placebo summary is based on fewer participants than either steroid summary.

The primary result posted is a comparison of low dose with standard dose. Although a placebo group is included and its mean change is shown, comparisons involving placebo are not reported in the registry record. The available inferential result therefore does not answer whether a steroid group differed from placebo. Results for change in testosterone are also not reported, despite its listing as a secondary outcome.

The primary outcome is limited to change from baseline to Day 28. Earlier measurements, longer-term measurements, and a formal assessment of the proposed transient response are not reported in the registry record. The endpoint is a serum marker, and the record does not report a clinical outcome or threshold for an important change in this marker.

Important design and analysis details are unavailable: the original sample-size justification, eligibility details, analysis population, missing-data handling, multiplicity strategy, and full statistical analysis plan are not reported in the registry record. The arm description for the standard-dose intervention uses the spelling Methylprednisone, while the intervention listing uses Methylprednisolone; the record does not clarify this difference. These limitations call for a restrained reading of the posted comparisons and prevent a fuller reconstruction of the trial's methods.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Effect of Intraarticular Steroids on Bone Turnover in Osteoarthritis — NCT00682357.
• Registry record last updated 2024-08-13; status last verified 2024-08.
• Results first posted 2016-11-29.
• 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

This completed randomized, unmasked, parallel-group trial enrolled 25 participants with osteoarthritis. It compared standard-dose and low-dose intra-articular steroid regimens with a placebo group. The primary outcome was change in serum osteocalcin from baseline to Day 28.

The posted primary comparison is low dose versus standard dose. Its mean difference is 1.73, with a 95% confidence interval from -0.541 to 4.001 and an unadjusted p-value of 0.135. The interval includes zero and indicates substantial uncertainty about the size and direction of the difference. A statistical comparison with placebo is not reported in the registry record.

Serum cortisol results are posted as a secondary outcome; testosterone results are not reported in the registry record. The record shows zero serious and other adverse events in each group, while death counts are not reported. The original sample-size justification, analysis population, missing-data methods, and multiplicity plan are also not reported in the registry record. The posted results are best read as limited, imprecise comparisons over the stated timeframe.