C7-T1 Epidural Steroid Injections Versus Targeted Injection for Treatment of Cervical Radicular Pain: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for C7-T1 Epidural Steroid Injections Versus Targeted Injection for Treatment of Cervical Radicular Pain (NCT02095197), a randomized phase 4 study. The primary outcome is Percentage of Participants With ≥50% Pain Reduction on the Numeric Rating Score (NRS) for Pain.

2. Clinical Question

The practical contrast is therefore the delivery approach, rather than the listed medication or total injection volume. The study was designed as a prospective randomized comparison, with the registry describing a single-masked, parallel-group design. The research question also connects to the investigators’ stated interest in medication use, function and patient satisfaction. Those outcomes appear as secondary measures in the posted results, while the primary endpoint is the proportion meeting the pain-reduction threshold at the one-month assessment.

This is a question about group-level outcomes in the enrolled trial population. It is not a comparison of every possible cervical injection approach, and the record does not establish that results apply to people outside the study population. The record also does not report detailed eligibility criteria, so the exact boundaries of that population cannot be reconstructed from the posted information.

3. Trial Design

The registry describes a prospective, randomized, single-masked, parallel-group Phase 4 trial sponsored by Northwestern University. The comparison was between standard C7-T1 epidural steroid injection without catheter delivery and targeted delivery via a cervical epidural catheter. Both arms are listed with triamcinolone 80mg and 1 mL 1% lidocaine, with a total volume of 2 cc. The registry status is completed. Enrollment is listed as 79, with the study start recorded as 2014-03 and primary completion as 2016-07.

For the primary outcome, the posted arm summaries contain 38 participants in the no-catheter group and 36 in the catheter-targeted group. Secondary outcome summaries list 40 and 36 participants, respectively. These endpoint denominators are not identical, and the registry record does not explain the difference. The primary measure is the percentage meeting a pain-reduction threshold at 1 month. The posted secondary measures concern medication quantification, patient global impression of change and neck disability, also at 1 month.

Random allocation is intended, in general, to make comparison groups more alike with respect to both measured and unmeasured characteristics at the point of allocation. Masking can reduce some influences on care or outcome assessment, depending on who is masked. The registry says the study was single-masked but does not report who was masked or how masking was maintained. Allocation concealment details, eligibility criteria, the planned analysis population, the original sample-size justification, and the full statistical analysis plan are not reported in the registry record.

The record’s enrollment figure should not be read as the denominator for every result: endpoint-specific denominators are shown in the result tables. The posted analysis is therefore best interpreted using the participants identified for each outcome, while recognizing that reasons for the denominator differences and any missing observations are not described.

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 Percentage of Participants With ≥50% Pain Reduction on the Numeric Rating Score (NRS) for Pain, measured over 1 month.

The primary endpoint is the percentage of participants who reported at least 50% pain reduction on the Numeric Rating Score for Pain at the 1 month follow-up. The registry describes the pain scale as ranging from 0, meaning no pain, to 10, meaning extreme pain. The endpoint converts each participant’s reported change into a binary outcome: meeting the specified reduction threshold or not meeting it. Results are then summarized as the proportion in each group who met that threshold.

A threshold-based endpoint can be easier to interpret than a group average on a pain scale because it focuses on the share of participants reaching a stated level of improvement. It also makes the outcome directly expressible as a percentage of participants. This approach has a trade-off: it does not show how far above or below the threshold an individual’s result was, and it discards gradations in response when turning a continuous pain experience into two categories. That is a general feature of binary threshold outcomes, not a finding specific to this trial.

The endpoint is relevant to the stated trial question because the registry’s summary describes pain control as a central objective. It does not, on its own, measure medication use, function, satisfaction, procedure-related safety or durability beyond the assessment time. Those questions require separate outcomes. The posted primary result concerns the proportion meeting the pain threshold at one month; it should not be read as a complete account of all patient outcomes or as evidence about later follow-up.

7. Results Posted in the Registry

• Catheter Targeted Delivery: 72.2% (26/36) versus 60.5% (23/38) on control; risk difference 11.7 percentage points (95% CI -9.6 to 33.0), risk ratio 1.19 (0.86–1.65); unadjusted two-proportion z-test p = 0.288.

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.

Decrease of > 6.8 Point Reduction in Medication Quntification Scale (MQS-III)

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Catheter Targeted Delivery: 25.0% (9/36) versus 32.5% (13/40) on control; risk difference -7.5 percentage points (95% CI -27.8 to 12.8), risk ratio 0.77 (0.37–1.58); unadjusted two-proportion z-test p = 0.472.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Catheter Targeted Delivery and the control. The interval gives the range of effects that remain compatible with the data.

Patient Global Impression of Change Score (PGIC) Less Than 3

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Catheter Targeted Delivery: 66.7% (24/36) versus 55.0% (22/40) on control; risk difference 11.7 percentage points (95% CI -10.1 to 33.5), risk ratio 1.21 (0.84–1.74); unadjusted two-proportion z-test p = 0.299.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Catheter Targeted Delivery and the control. The interval gives the range of effects that remain compatible with the data.

Greater Than or Equal to a 30% Reduction in Oswestry Neck Disability Index Score

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Catheter Targeted Delivery: 66.7% (24/36) versus 57.5% (23/40) on control; risk difference 9.2 percentage points (95% CI -12.6 to 30.9), risk ratio 1.16 (0.81–1.65); unadjusted two-proportion z-test p = 0.411.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Catheter Targeted Delivery and the control. The interval gives the range of effects that remain compatible with the data.

The three posted secondary measures add information about medication quantification, patient global impression of change and neck disability at 1 month. Taken together, they do not form a single consistent pattern across every endpoint. The proportions meeting the global-impression and neck-disability criteria are numerically higher in the catheter-targeted group, while the medication-quantification reduction criterion is numerically lower in that group. These are different outcomes with different definitions, so the direction of a numerical contrast cannot be assumed to carry the same meaning across measures.

The secondary results can be read alongside the primary pain-threshold result as an exploratory picture of several outcome domains. They do not independently establish that the primary pattern is reproducible, and they do not replace the primary endpoint. Each measure asks a separate question; for example, the medication criterion is not a substitute for pain response, and a disability threshold is not a direct measure of patient satisfaction.

The registry reports unadjusted analyses for these secondary outcomes. When several outcomes are examined, the chance of finding an apparently notable result somewhere among them can increase, even if no corresponding effect exists. Statistical adjustment or a pre-specified hierarchy can address aspects of this multiplicity, but the registry record does not report whether either was used. Consequently, unadjusted secondary p-values carry less weight than a clearly prespecified primary result and should be treated as supporting description rather than definitive evidence.

The displayed secondary denominators also differ from those for the primary outcome. The reason is not reported in the registry record. That makes it important not to interpret the secondary set as though every endpoint necessarily reflects the same participants or the same analysis population. Overall, the secondary outcomes broaden the scope of what was measured, but they leave uncertainty about their interpretation and do not remove the imprecision in the primary comparison.

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

• Decrease of > 6.8 Point Reduction in Medication Quntification Scale (MQS-III)
• Patient Global Impression of Change Score (PGIC) Less Than 3
• Greater Than or Equal to a 30% Reduction in Oswestry Neck Disability Index Score

9. Statistical Interpretation

10. Statistical Methods Explained

This discussion explains the statistical ideas behind the result display. The posted primary endpoint is binary: each participant either meets the pain-reduction threshold or does not. Binary outcomes are commonly summarized as a count and a proportion in each group. Here, the posted counts are 23 of 38 for no-catheter delivery and 26 of 36 for catheter-targeted delivery. The registry also displays the arm percentages and confidence intervals. Since the endpoint is a proportion, the analysis does not preserve the amount of pain reduction beyond whether the threshold was met.

What does a risk difference describe?

A risk difference subtracts the proportion in one group from the proportion in the other, with the comparison direction stated explicitly. In this display, the catheter-targeted group is compared with the no-catheter group. A positive estimate means the event proportion is higher in the catheter-targeted group for the event as defined; a negative estimate means it is lower. The recalculated risk difference is 0.117. This is an absolute contrast in proportions, not a relative measure. It does not by itself say whether the difference is clinically important, and its interpretation depends on what counts as an event.

Relative measures such as a risk ratio or odds ratio describe the contrast differently. The posted calculations include these measures, but the risk difference is useful for showing an absolute contrast between the group proportions. Different measures can emphasize different aspects of the same data. None should be interpreted without its uncertainty interval and an understanding of the endpoint definition.

What does a confidence interval add?

A confidence interval expresses uncertainty about an estimated quantity under the assumptions of the analysis. The 95% confidence interval for the primary risk difference runs from -0.097 to 0.330. In general, a wider interval indicates less precision, while a narrower interval indicates greater precision. An interval that includes zero means the data do not rule out no difference under this interval-based description. It also does not establish that the true difference is zero: values on either side of zero remain compatible with the interval.

The arm-level intervals answer a different question from the interval for the risk difference. The posted 45.0% to 75.0% interval belongs to the no-catheter group’s proportion, while 57.0% to 87.0% belongs to the catheter-targeted group’s proportion. Comparing overlap between these separate intervals is not a substitute for reading the direct interval for the group contrast. The calculated comparison display gives the direct estimate and its interval.

Why do tests differ?

A hypothesis test summarizes how incompatible the observed data are with a specified null model, subject to the test’s assumptions. The registry lists Fisher Exact for the primary comparison, with p = 0.23. Fisher Exact is a test for categorical data that evaluates possible tables of counts under a null of no association, using an exact calculation. A simple unadjusted re-calculation from the posted summary statistics reports p = 0.288. The p-values are not identical because the calculations and methods differ; the re-calculation should not be mistaken for the registry’s own analysis.

A p-value is not the probability that the null hypothesis is true, nor does it measure the probability that a result will reproduce. It also does not quantify effect size or clinical importance. The estimate, interval, endpoint definition and analysis method are all needed to interpret the result. The original statistical plan and full details of the sponsor’s analysis are not reported in the registry record, so the displayed analyses do not permit a complete audit of every modeling or data-handling decision.

How should unadjusted calculations be read?

The calculations labeled as recalculated are simple, unadjusted re-calculations from the posted summary statistics. They do not account for covariates or other possible design features. They provide a transparent way to describe the displayed counts, but they are not a reconstruction of an unavailable full analysis plan. The registry’s own primary test should be identified separately from the recalculation, and the two should not be combined as though they were one test.

For a binary outcome, uncertainty depends on the event counts and denominators as well as the difference between group proportions. Small samples can leave substantial uncertainty even when the observed percentages differ. This general principle is visible in the primary comparison’s interval, which spans zero. The same caution applies to the secondary comparisons: their point estimates are summaries of the posted samples, and their unadjusted p-values are not proof of effects.

What does the one-month endpoint leave out?

The primary endpoint captures whether participants met one pain-response threshold at one time point. It does not describe the full distribution of pain changes, later outcomes, medication use, neck disability, patient global impression or adverse events. Those are distinct questions. The registry includes secondary measures for some of these domains, but their presence does not make the primary endpoint comprehensive. The statistical interpretation must remain tied to the particular outcome and assessment time displayed.

Finally, participant denominators differ between the primary and secondary results. Statistical summaries depend on which observations are included. The registry does not explain why those denominators differ, whether any missing observations were imputed, or which analysis population was planned. These omissions limit assessment of how robust the estimates are to missing data or departures from the randomized allocation.

11. Confidence Intervals and Precision

Precision is about how tightly the data locate an estimated quantity. The primary arm proportions are displayed with 95% confidence intervals: 60.0% with an interval from 45.0% to 75.0% for no-catheter delivery, and 72.0% with an interval from 57.0% to 87.0% for catheter-targeted delivery. Both intervals cover a broad range of possible proportions. The calculated plot and table show these intervals visually and numerically; they are more informative than the point estimates alone.

For the direct comparison, the recalculated risk difference is 0.117, with a 95% confidence interval from -0.097 to 0.330. Because this interval includes zero, it is compatible with no group difference as well as with differences in either direction. The interval’s endpoints also show that the data do not pin down a single precise magnitude. The point estimate is therefore best treated as the center of an uncertain range, not as a settled value.

Confidence intervals are not guarantees that a particular realized interval contains the true value, and they do not describe the range of individual participant outcomes. In general, they summarize sampling uncertainty under the method’s assumptions. Here, the primary endpoint is a proportion and the comparison is based on relatively limited endpoint denominators as shown in the registry tables. The record does not give enough detail to assess every assumption behind the reported arm intervals or sponsor analysis.

Precision and statistical significance are related but not identical ideas. A test result can be described by a p-value, while an interval makes the range of compatible estimates easier to see. For this comparison, the broad interval is a central feature of interpretation regardless of which p-value is emphasized. Readers should use the displayed intervals to understand uncertainty and avoid treating the difference between the two arm percentages as exact or definitive.

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 and curve are planning illustrations based on the observed effect, not a record of the trial’s original design calculation. For these posted outcomes, the entries are participants per arm. The distinction matters: in a time-to-event analysis, a planning display may instead count total events, but the outcomes are binary and the figures refer to participants per arm.

The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect used for each planning row is the stated fraction of the observed effect. The 80% power column describes the participants per arm that the illustration estimates would be needed to have an 80% chance of detecting the specified effect under those assumptions, if that effect were the one present and the model assumptions held. The 90% power column gives the corresponding planning amount for a 90% chance.

Rows for a smaller fraction of the observed effect require more participants per arm. That pattern reflects a general property of study planning: smaller group differences are harder to distinguish from random variation, so more information is needed to detect them with the same planned power and significance level. The curve visualizes the same relationship across the displayed planning range; it is not a separate observed result.

These entries are not observed power. They are hypothetical planning illustrations calculated after the results were available, using the observed effect as their starting point. They should not be interpreted as proof that the completed trial was adequately or inadequately powered. The trial’s own original sample-size justification and design assumptions are not reported in the registry record.

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 = 0.605; treatment proportion p₁ = 0.722; average p̄ = 0.664.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6681 = 1.3095.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6630 = 0.5580.
4. n = (1.3095 + 0.5580)² / (0.1170)² = 254.9, rounded up to 255 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 <- 0.605263157894737                          # control proportion
p1 <- 0.722222222222222                          # 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(2095197)
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 = 255 (80% power), 341 (90% power)
 75% of observed effect: n per arm = 464 (80% power), 620 (90% power)
 50% of observed effect: n per arm = 1,064 (80% power), 1,423 (90% power)
power.prop.test: 254.9 
Simulated power at n = 255 per arm: 0.799 (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 reports the sponsor’s primary comparison as a Fisher Exact analysis, with p = 0.23. The calculated tables also show a simple unadjusted re-calculation from the posted counts and denominators, which gives p = 0.288 and a risk difference of 0.117 with a 95% confidence interval from -0.097 to 0.330. These are distinct results from distinct calculations, not two versions of a single reported test.

The sponsor’s test is the registry-reported analysis and should be identified as such. The recalculation is useful for describing the group contrast in a transparent, unadjusted way, but it is not a replacement for the sponsor’s analysis or a reconstruction of the full statistical plan. The registry does not provide enough detail to explain all analytical choices or to reconcile the difference in p-values fully. The record does not flag a discrepancy between posted and recalculated results.

Both values should be read alongside the effect estimate and interval rather than used as stand-alone verdicts. The interval communicates that the group contrast is imprecise and includes zero. Neither p-value changes the underlying endpoint definition, resolves the limitations of the available denominators, or establishes a clinically meaningful difference. In reporting, the sponsor’s result and the recalculated summary should remain clearly labeled so readers can distinguish the registry analysis from the secondary descriptive calculation.

15. Multiplicity, Missing Data and Analysis Populations

The trial includes a primary endpoint and three posted secondary endpoints. Examining multiple outcomes creates a multiplicity concern: even when each individual test uses a conventional threshold, the probability of at least one apparently unusual result across a family of tests can be greater than the probability for one test considered alone. This is a general statistical issue and does not mean that any specific result is false.

The registry record does not report whether the secondary outcomes were prespecified in a formal hierarchy, whether the sponsor adjusted for multiple comparisons, or whether the primary result was protected from multiplicity through a particular testing strategy. The listed secondary analyses are reported without a stated adjustment. Their p-values should therefore be read as unadjusted, and interpreted cautiously rather than as confirmatory evidence independent of the primary endpoint.

Missing-data handling is also not reported in the registry record. The primary outcome denominators are 38 and 36, while the secondary outcome summaries list 40 and 36. The record does not explain why the denominators vary, whether observations were unavailable, whether any participants were excluded from particular analyses, or how missing outcomes were handled. It does not state whether an intention-to-treat, per-protocol or other analysis population was used. These details matter because the population included in an analysis can affect the estimated proportions and the validity of a randomized comparison.

The record also does not describe whether the analysis accounted for baseline characteristics, how randomization was implemented, or whether any interim analyses were planned or conducted. Those elements should not be inferred from the randomized design label or from the completed status. Their absence does not prove that a particular method was or was not used; it means the registry entry does not document it. Readers can assess the reported summaries and tests, but cannot fully evaluate the analysis strategy or its handling of multiple outcomes and missing observations from this record alone.

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 adverse-event summary lists zero participants affected by serious adverse events in both groups: the no-catheter group has 40 participants at risk, and the catheter-targeted group has 36 participants at risk. The summary also lists zero participants affected by other adverse events in each group, using the same at-risk counts. These entries describe what is recorded in the posted adverse-event fields; they are not estimates of comparative safety with precise uncertainty bounds.

The death fields are not populated with a numerical result, so deaths are not reported in the registry record. The serious adverse event term list is empty. An empty term list and zero affected counts should be read narrowly as registry entries, not as proof that no event could have occurred or that all possible harms were comprehensively captured. The record does not provide event definitions, follow-up duration for safety, ascertainment procedures or a detailed narrative of adverse events.

The adverse-event denominators differ from the primary endpoint denominators. The registry does not explain that difference. As a result, safety counts should be read using their own stated at-risk groups, not silently substituted with the primary outcome sample. The posted figures are useful for identifying what the registry reports, but the limited detail and absence of a fuller safety description constrain interpretation.

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

The posted data show a higher observed percentage meeting the one-month pain-reduction threshold in the catheter-targeted group than in the no-catheter group. The direct recalculated comparison is uncertain: its 95% confidence interval includes zero and extends in both directions. The registry’s own Fisher Exact test is reported separately. Taken together, the results describe the outcomes observed in this trial, but they do not establish that one delivery method is superior.

A group-level proportion does not predict what will happen to a particular individual. The trial compared randomized groups, and its estimate represents an average contrast in the enrolled sample for a defined endpoint and time point. It does not say whether any one participant will meet the threshold, how much pain any individual will report, or how outcomes might differ in a population not represented in the study. The record does not report enough eligibility detail to define the full limits of generalizability.

The endpoint also captures only one part of the broader clinical question. It does not directly measure the full experience of pain, sustained benefit beyond 1 month, medication use, function, satisfaction or every safety outcome. Secondary results address some related domains, but their unadjusted nature and endpoint-specific denominators call for caution. The available summary does not resolve whether the observed patterns would persist under a larger study or at later assessment times.

Statistical uncertainty should not be translated into a claim that the approaches are identical. An interval that includes zero means the data are compatible with no difference under the stated analysis, but also with differences on either side of zero. Likewise, a numerical advantage in a point estimate does not establish a reliable advantage. The result is best described as an observed contrast with considerable uncertainty, interpreted in the context of the registry’s limited reporting on missing data, analysis populations and the original statistical plan.

This page is a statistical interpretation of posted registry results, not medical advice. It cannot decide which procedure is appropriate for an individual or replace a clinical assessment. Its purpose is to distinguish the observed data from what they can and cannot demonstrate.

18. Why This Trial Matters Statistically

This trial is statistically informative because it directly randomized two delivery approaches while listing the same medication and total injection volume in both arms. That design focuses the stated comparison on whether catheter-targeted delivery differs from delivery without a catheter, rather than presenting a contrast in which the listed drug regimen also differs. The distinction helps readers identify what the trial was intended to compare.

The endpoint also illustrates a common analytic choice in clinical research: converting a patient-reported scale into a threshold response. A threshold can make a result straightforward to express as the proportion of participants reaching a specified level of pain reduction. At the same time, dichotomization loses detail about changes that fall on either side of the threshold. This makes it important to read the endpoint definition rather than treating the reported percentages as a complete summary of pain experience.

The trial further illustrates why an estimate and confidence interval matter alongside a p-value. The observed percentages differ, but the direct interval spans zero and a range of possible contrasts. That conveys uncertainty that a point estimate alone could obscure. The registry’s sponsor-reported test and the unadjusted recalculation also show why analysis labels and methods need to be kept distinct rather than reduced to a single significance statement.

Finally, the different denominators across endpoints and the unreported details about missing data, analysis populations and multiplicity show how registry completeness affects independent interpretation. The numerical results are available, but important context for judging the analysis is not. These issues are broadly relevant when evaluating randomized trials from registry postings: the design label and outcome values are only part of the information needed to understand what an estimate means.

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.

Several limitations specific to this trial constrain interpretation. The registry reports enrollment of 79, while the primary result is summarized using 38 participants in the no-catheter group and 36 in the catheter-targeted group. Secondary outcomes use 40 and 36 participants. The reason for these endpoint-specific denominators is not reported in the registry record. Without an account of missing observations or analysis populations, readers cannot determine why the counts differ or evaluate the effect of the difference on the results.

The primary endpoint is a binary threshold at 1 month. It does not retain the full detail of the Numeric Rating Score for Pain, show the distribution of change, or describe persistence at a later time. The registry includes secondary outcomes, but these have their own definitions and unadjusted analyses. The record does not report whether multiplicity was addressed or how outcome priorities were handled beyond identifying the primary endpoint.

Although the trial is described as randomized and single-masked, the registry does not say who was masked, how allocation was concealed or how randomization was implemented. Eligibility criteria, baseline characteristics and detailed procedures for outcome assessment are not included in the information. The original sample-size justification, full statistical analysis plan, interim analysis plan and missing-data methods are not reported in the registry record. These omissions limit assessment of analysis choices and possible sources of bias.

The confidence interval for the primary comparison is broad and includes zero, so the estimate is not precise enough to settle the direction or magnitude of the group contrast. The safety summary is also limited: it reports counts for serious and other adverse events but does not provide event definitions, detailed follow-up, or numerical death results. Finally, one-month outcomes in this enrolled sample cannot by themselves establish longer-term outcomes or generalizability to populations whose characteristics are not described in the record.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: C7-T1 Epidural Steroid Injections Versus Targeted Injection for Treatment of Cervical Radicular Pain — NCT02095197.
• Registry record last updated 2017-03-28; status last verified 2017-02.
• Results first posted 2017-03-28.
• 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 record describes a completed, randomized, single-masked, parallel-group Phase 4 trial sponsored by Northwestern University. It compares cervical epidural steroid injection without catheter delivery with catheter-targeted delivery, using the same listed triamcinolone and lidocaine regimen in both arms. Enrollment is 79, and the primary outcome is the percentage meeting at least 50% pain reduction on the Numeric Rating Score for Pain at 1 month.

The primary arm summaries are 60.0% and 72.0%, with a recalculated risk difference of 0.117 and a 95% confidence interval from -0.097 to 0.330. The registry reports a Fisher Exact p-value of 0.23. Secondary outcomes and adverse-event entries are also posted, but denominators vary by outcome and analysis details are limited.

The results show an observed difference but leave substantial uncertainty about its size and direction. Missing-data procedures, analysis populations, multiplicity handling and the original sample-size justification are not reported in the registry record.