This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for A Study Comparing Two Methods of Placing an Interscalene Nerve Catheter for Postoperative Pain Control in Patients Who Undergo Open Shoulder Surgery. (NCT01696188), a randomized na study. The primary outcome is Visual Analog Scale Pain Scores.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01696188 |
| Phase | NA |
| Condition | Shoulder Pain |
| Allocation | Randomized |
| Design model | Single Group |
| Masking | Double |
| Enrollment | 84 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Thomas Jefferson University |
| Results posted | Yes |
2. Clinical Question
Population
Patients undergoing open shoulder surgery, with shoulder pain listed as the condition. The registry reports enrollment of 84 participants. Outcome summaries use group sizes of 40 for the in-plane group and 42 for the out-of-plane group; the reason these outcome group sizes do not account for all enrolled participants is not reported in the registry record.
Intervention
An interscalene nerve catheter placed using an out-of-plane ultrasound-guided approach. In this approach, the needle does not travel within the plane of the ultrasound beam, according to the study description.
Comparator
An interscalene nerve catheter placed using an in-plane ultrasound-guided approach. Both groups received the same general type of catheter; the comparison concerns the ultrasound-guided placement approach.
Primary question
How did 24-hour pain scores compare between the two catheter-placement approaches? Pain was rated on a scale from 0, meaning no pain, to 10, meaning worst pain imaginable. The registry reports a median and inter-quartile range for each group, but does not report a formal primary-endpoint comparison.
3. Trial Design
This was a prospective, randomized, double-blinded trial comparing in-plane with out-of-plane ultrasound-guided approaches for placing an interscalene nerve catheter after open shoulder surgery. The registry lists the study as completed, with enrollment of 84 participants. The listed study dates are 2012-07 for the start and 2014-06 for primary completion. The phase is recorded as NA.
The two listed groups are the In-plane Group and the Out-of-plane Group. The registry describes the intervention as an interscalene nerve catheter, with the placement approach differing between groups. Random allocation and double masking are recorded, but who was masked and how the allocation sequence was generated or concealed are not reported in the registry record. Further details about the conduct of randomization are also not reported.
The registry classifies the study model as single-group while also listing two groups and results for each. This is an inconsistency in the record’s design descriptors; no explanation is reported in the registry record. The outcome summaries give group sizes of 40 and 42. The reason those reported sizes do not match the total enrollment is not reported in the registry record, nor are participant flow details or reasons for any missing outcome data.
The primary outcome was Visual Analog Scale Pain Scores at 24 hours, summarized using the median and inter-quartile range. Listed secondary outcomes include catheter dislodgements, opioid consumption, and time for block placement. Results are posted for catheter dislodgements, but results for opioid consumption and time for block placement are not reported in the registry record. The record lists no reported analyses.
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
| Stage | In-plane Group | Out-of-plane Group |
|---|---|---|
| STARTED | 41 | 43 |
| COMPLETED | 40 | 42 |
| NOT COMPLETED | 1 | 1 |
Reasons for not completing this period:
| Reason | In-plane Group | Out-of-plane Group |
|---|---|---|
| Protocol Violation | 1 | 1 |
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.
| Characteristic | Unit | In-plane Group | Out-of-plane Group | Total |
|---|---|---|---|---|
| Participants analysed | 40 | 42 | 82 | |
| Age, Continuous | years | 67.1 (SD 10.7) | 63.8 (SD 12) | 65.2 (SD 11.4) |
| Sex: Female, Male: Female | Participants | 25 | 17 | 42 |
| Sex: Female, Male: Male | Participants | 15 | 25 | 40 |
| Region of Enrollment: United States | participants | 40 | 42 | 82 |
6. Primary Endpoint
The registry lists the primary outcome as Visual Analog Scale Pain Scores, measured over 24 hours.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | units on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is pain at 24 hours, measured using a visual analog scale. The scale runs from 0, defined as no pain, to 10, defined as the worst pain imaginable. A pain score is a patient-reported measure of symptom intensity at the stated assessment time. It addresses a different question from the technical placement outcomes: it reflects reported pain rather than how long placement took or whether a catheter became dislodged.
The registry summarizes pain using the median and inter-quartile range. The median is the middle value when observations are ordered; it describes the center of the observed scores without being as sensitive to extreme values as the mean. The inter-quartile range describes the middle half of the observed values, giving a sense of the spread around the median. These summaries do not, by themselves, quantify the uncertainty in a comparison between groups.
The reported median was 1.3, with an inter-quartile range from 0.0 to 3.8, in the in-plane group. In the out-of-plane group, the median was 1.5, with an inter-quartile range from 0.0 to 4.5. The registry does not report a formal statistical comparison, confidence interval, or p-value for this primary endpoint. Therefore, the posted summaries describe the observed group distributions but do not establish the precision of a between-group effect estimate.
In general, a pain scale can be useful for comparing patient experience when the timing and scale are consistently defined. Interpretation still depends on how scores were collected and which participants contributed data; these details are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary-endpoint results are descriptive. At 24 hours, the in-plane group had a median pain score of 1.3 and an inter-quartile range of 0.0 to 3.8. The out-of-plane group had a median of 1.5 and an inter-quartile range of 0.0 to 4.5. The registry does not report a formal comparison of these summaries, so it does not provide a primary-endpoint effect estimate with a confidence interval or a primary-endpoint p-value. The summaries alone cannot show how precisely the group difference is estimated.
The study description states that the investigators hypothesized that the out-of-plane approach would lead to decreased pain and fewer catheter dislodgements. The posted medians do not show a lower median pain score in the out-of-plane group. However, a comparison of medians is not a complete analysis of the score distributions, and the registry does not provide a formal inferential analysis of this endpoint. The data therefore should not be read as a definitive test of the stated pain hypothesis.
For catheter dislodgements, the posted counts were 4 participants in the in-plane group and 1 in the out-of-plane group. A simple unadjusted recalculation from those counts gives a risk difference of -0.076 for out-of-plane versus in-plane, with a 95% confidence interval from -0.18 to 0.028 and an unadjusted p-value of 0.15. Because the interval includes zero, the data are compatible with no difference as well as with effects in either direction. The point estimate alone should not be treated as conclusive evidence of a difference.
The trial enrolled 84 participants, while the endpoint summaries report 40 and 42 participants in the two groups. The reason for this difference, and whether missing outcomes could affect the comparisons, is not reported in the registry record. The size of the study and the width of the interval for catheter dislodgements matter when interpreting the results: a non-significant p-value does not prove that the approaches are equivalent, and the observed direction does not establish a reliable advantage.
No formal analysis of the primary outcome or other reported sponsor analysis is listed. The registry therefore supports a cautious reading: it records group-level pain summaries and a secondary dislodgement comparison, but does not document a complete inferential analysis of the trial’s primary question.
9. Statistical Methods Explained
The registry identifies the study as prospective, randomized, and double-blinded. These design features are intended, in general, to support a fair comparison and reduce some sources of bias. Random allocation can help balance participant characteristics between groups, while masking can reduce the influence of expectations on care or outcome assessment. The record does not describe the allocation procedure, the people who were masked, or how masking was maintained, so those details cannot be evaluated from the registry entry.
What the primary summaries describe
The primary endpoint is pain at 24 hours, reported on a scale from 0 to 10. The group results are medians with inter-quartile ranges rather than means with standard deviations. In general, the median gives the center of an ordered set of scores, and the inter-quartile range describes the span of its middle half. This summary can be useful when values are skewed or when a few extreme observations might pull the mean. It does not provide a direct estimate of the uncertainty around a difference between groups.
The registry reports a median of 1.3 and an inter-quartile range of 0.0 to 3.8 for the in-plane group, and a median of 1.5 with an inter-quartile range of 0.0 to 4.5 for the out-of-plane group. The record does not report a test or interval for the primary comparison. It also does not state whether the analysis was intended to compare medians, distributions, or another feature of the pain scores. The reported summaries should therefore be read as descriptive rather than as a complete inferential result.
How to read the dislodgement comparison
Catheter dislodgement is reported as a number of participants in each group over 24 hours. For a binary outcome, the risk is the proportion of participants who experienced the event. A risk difference expresses the absolute difference between the two group risks. The recalculated, simple unadjusted risk difference for out-of-plane versus in-plane is -0.076, with a 95% confidence interval from -0.18 to 0.028. The unadjusted p-value is 0.15.
In general, a confidence interval describes a range of values compatible with the observed data under the method used to construct it. It conveys uncertainty about an estimate; it is not a guarantee that the true effect lies within the interval. Here, the interval includes zero, the value corresponding to no risk difference. The interval also extends in both directions around zero, so the estimate is not precise enough to establish the direction of a difference. The p-value summarizes how unusual data at least as incompatible with a no-difference hypothesis would be under that hypothesis and the test’s assumptions. It is not the probability that the hypothesis is true, nor does it measure the size or clinical importance of an effect.
The registry also lists risk-ratio and odds-ratio estimates for this endpoint. These are relative measures, whereas the risk difference is an absolute measure. In general, relative measures describe how risks compare as a ratio, while absolute measures describe the difference in event frequency. The registry does not report separate adjusted analyses, and the posted analyses list is empty. These secondary comparison figures should therefore be treated as unadjusted summaries rather than as evidence of a prespecified, model-based analysis.
Planning illustrations and power
The planning illustrations use the observed effect as a starting point and show participants per arm for 80% power and participants per arm for 90% power at the stated effect fractions. The listed assumptions are a two-sided significance level of 0.05, equal allocation, and a normal approximation. For planning for 100% of the observed effect, the illustrations give 156 participants per arm for 80% power and 209 participants per arm for 90% power. For planning for 75% of the observed effect, they give 318 and 425 participants per arm, respectively. For planning for 50% of the observed effect, they give 804 and 1,076 participants per arm, respectively.
These are planning illustrations based on the observed effect, not evidence that the trial had a particular probability of detecting an effect. Smaller effects generally require larger samples to detect under a fixed design and assumptions. The registry explicitly distinguishes these illustrations from the trial’s own design; its sample-size justification and prospective power calculation are not reported in the registry record. The illustrations do not establish that any effect size is clinically important or that the trial was designed to detect it.
What is not documented
The registry lists no reported analyses. It does not report a formal primary-endpoint test, a prespecified statistical analysis plan, an approach to missing values, an analysis population, or details of any interim analysis. It also does not report whether the secondary comparisons were prespecified or adjusted for multiple testing. These omissions limit assessment of how closely the displayed results reflect the original trial plan.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary endpoint and three secondary outcomes, but reports no analyses in its analysis listing. A formal comparison for the primary pain endpoint is not reported in the registry record. The registry does report a comparison for catheter dislodgements, while results for opioid consumption and time for block placement are not reported. It is not reported whether the secondary outcomes were specified in advance, how many comparisons were planned, or whether any multiplicity adjustment was used.
In general, multiplicity matters when investigators evaluate several outcomes or conduct several comparisons. The more tests considered, the greater the chance that at least one result may appear statistically unusual even when there is no true effect. A prespecified primary endpoint can help distinguish the central trial question from exploratory secondary findings. Without a reported analysis plan or multiplicity strategy, the weight to place on the unadjusted secondary p-value is difficult to judge.
Missing-data methods and analysis populations are not reported in the registry record. The enrolled total is 84, while the primary outcome group summaries use 40 participants in the in-plane group and 42 in the out-of-plane group. The registry does not explain the difference, state how many participants were randomized to each group, or describe whether all randomized participants were included in an analysis. Reasons for missing data, if any, and the handling of missing observations are not reported.
In general, missing outcomes can affect a comparison if participants with observed results differ from those without results. Without participant flow, analysis-population definitions, and missing-data procedures, it is not possible to determine whether the posted summaries represent all randomized participants or how sensitive the results might be to unavailable observations. Interim analyses, stopping rules, and a sample-size justification are also not reported in the registry record. These gaps limit evaluation of whether the reported comparisons follow a prespecified statistical plan.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| In-plane Group | 0 | 40 | 0.0% |
| Out-of-plane Group | 0 | 42 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| In-plane Group | 0 of 40 |
| Out-of-plane Group | 0 of 42 |
The registry reports zero serious adverse events among 40 participants in the in-plane group and zero among 42 participants in the out-of-plane group. It also reports zero other adverse events among the participants at risk in each group. No serious adverse-event terms are listed. Death counts are not reported in the registry record.
These figures describe the events recorded for the listed groups; they do not demonstrate that no adverse events could occur or that the approaches have identical safety profiles. In general, when no events are observed in a study, the data still leave uncertainty about the frequency of uncommon events, particularly when the group sizes are limited. The registry does not provide event definitions, collection procedures, follow-up beyond the stated outcome period, or further safety analyses. Those details are not reported in the registry record.
The serious and other adverse-event summaries should be interpreted separately from the pain and catheter-displacement outcomes. They are registry counts, not a comparative safety analysis with an effect estimate or confidence interval. The absence of listed events is a description of the posted record and should not be extended beyond the participants and reporting captured there.
12. What the Result Does, and Does Not, Mean
The registry records a randomized, double-blinded comparison of two approaches for placing an interscalene nerve catheter after open shoulder surgery. It provides 24-hour pain summaries for both groups and a secondary comparison of catheter dislodgements. The pain summaries describe the observed medians and inter-quartile ranges, but there is no reported formal comparison for the primary endpoint. The dislodgement estimate is uncertain, with its confidence interval including no difference.
These findings do not establish that either approach produces lower pain or fewer dislodgements. The posted median pain score is not lower in the out-of-plane group, and the secondary point estimate favoring fewer dislodgements in that group is not sufficiently precise to rule out no difference. At the same time, the results do not establish that the approaches are equivalent. A non-significant p-value or an interval that includes zero does not prove that the groups have the same outcomes.
The record also cannot answer all of the study’s stated secondary questions. Results for opioid consumption and time for block placement are not reported in the registry record. Information about participant flow, missing data, the analysis population, and the statistical plan is also absent. These limitations mean the posted values should be treated as a partial record of the trial’s results, not as a complete account of every planned analysis.
In general, a trial result is most informative when the endpoint, comparison, uncertainty, analysis population, and handling of missing data are clearly reported. Here, the descriptive primary results and the single available secondary comparison offer limited evidence about the two approaches. They can be read as estimates from the participants with posted outcomes, but they do not support a definitive conclusion about comparative effects or safety.
13. Why This Trial Matters Statistically
This trial raises a useful statistical distinction between reporting group summaries and reporting a comparative analysis. Medians and inter-quartile ranges describe the observed pain scores in each group, but they do not by themselves quantify the uncertainty in the difference between groups. Without a primary-endpoint estimate and confidence interval or test, readers cannot assess the precision of the trial’s main comparison from the registry results.
The secondary dislodgement outcome illustrates why effect direction and statistical uncertainty must be considered together. Its point estimate favors one approach, but the confidence interval includes no difference and extends in either direction. A single directionally favorable estimate is not enough to establish a reliable difference, especially when the record does not describe a prespecified analysis plan or adjustment for multiple outcomes.
The record also highlights the importance of matching the enrollment total to the analysis denominators. Enrollment is 84, while the group summaries list 40 and 42 participants. Without participant flow or an explanation of the denominators, it is difficult to know whether the results represent all randomized participants or how missing outcomes were handled. These details are central to judging whether a comparison is vulnerable to bias.
Finally, the planning illustrations are not a substitute for a prospective sample-size justification. They are based on the observed effect and illustrate how sample requirements change under stated planning assumptions. The registry does not report the study’s original sample-size rationale. Keeping descriptive results, inferential comparisons, and retrospective planning illustrations distinct helps prevent stronger conclusions than the record supports.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
Several limitations specific to this record constrain interpretation. Although the study is described as randomized and double-blinded, the record does not explain sequence generation, allocation concealment, or who was masked. It also classifies the model as single-group while listing two randomized groups, with no explanation of that inconsistency. These omissions make the design difficult to reconstruct in detail from the registry entry alone.
The primary endpoint is reported only through group-level medians and inter-quartile ranges. A formal comparison, confidence interval, and p-value are not reported. The record does not describe the intended statistical method for comparing the pain scores or state how the primary analysis was defined. Thus, the registry allows a descriptive reading but not a full assessment of the primary treatment contrast.
Outcome summaries use group sizes of 40 and 42 despite total enrollment of 84. Participant flow, numbers randomized, reasons for unavailable outcomes, and analysis-population definitions are not reported. Missing-data procedures are also not reported. These gaps prevent assessment of whether the analysis denominators reflect all randomized participants or whether outcome availability could have affected the results.
Only one of the three listed secondary outcomes has posted results. The registry does not report results for opioid consumption or time for block placement, and it does not state whether secondary comparisons were prespecified or adjusted for multiplicity. The available dislodgement comparison is unadjusted. Finally, serious adverse-event counts are reported as zero in both groups, but further details of event ascertainment and safety analysis are not reported. These are limitations of the registry record and do not, by themselves, establish that the trial investigators did not collect additional information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Study Comparing Two Methods of Placing an Interscalene Nerve Catheter for Postoperative Pain Control in Patients Who Undergo Open Shoulder Surgery. — NCT01696188.
- Registry record last updated 2015-11-16; status last verified 2015-10.
- Results first posted 2015-11-16.
- 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.
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18. Record Summary
The registry record describes a completed, prospective, randomized, double-blinded trial comparing in-plane and out-of-plane ultrasound-guided approaches to interscalene nerve catheter placement for postoperative pain control after open shoulder surgery. Enrollment was 84. The primary endpoint was pain at 24 hours, measured on a scale from 0 to 10 and summarized by median and inter-quartile range.
The record reports pain summaries for both groups but no formal primary comparison. It also reports catheter dislodgement counts and an unadjusted comparison; results for opioid consumption and time for block placement are not reported in the registry record. Serious and other adverse-event counts are zero in both groups, while death counts are not reported. Analysis methods, participant flow, missing-data handling, and a sample-size justification are not reported in the registry record.