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 Vertebral Body Tethering Outcomes for Pediatric Idiopathic Scoliosis (NCT03194568), a na na study. The primary outcome is Incidence of Treatment-Emergent Adverse Events.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03194568 |
| Phase | NA |
| Condition | Idiopathic Scoliosis |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 20 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Patrick Cahill, MD |
| Results posted | Yes |
2. Clinical Question
Population
Children with idiopathic scoliosis were the study population. The registry lists an enrollment of 20. It does not report further eligibility details or describe the characteristics of participants at baseline, so the results cannot be related to particular curve patterns or other participant features.
Intervention
The intervention was anterior vertebral tethering, using an anterior vertebral tether device. The registry describes the study as assessing the safety and feasibility of an anterior approach for spinal deformity in pediatric idiopathic scoliosis. Details of the operative protocol are not reported in the registry record.
Comparator
There was no separate comparator group. The study is recorded as single-group, and the registry does not describe a randomized comparison. Pre-operative and post-operative Cobb angle and SRS 30 scores are listed as secondary outcomes, but their results are not reported in the registry record.
Primary question
The primary outcome concerns the incidence of treatment-emergent adverse events, captured from the start of the intervention through up to 2 years. The record describes collecting information about event timing, severity, outcome, and relationship to the intervention. The posted safety figures report participant counts, but the registry record does not provide a comparative estimate of risk.
3. Trial Design
This completed study enrolled 20 participants with idiopathic scoliosis and evaluated anterior vertebral tethering in a single group. The registry lists the intervention as the Anterior Vertebral Tether, a device. It does not describe a control group or randomized allocation, so the study is not a like-for-like comparison of treatments. Masking is listed as none.
The stated purpose was to assess whether anterior vertebral tethering is a safe and feasible anterior approach for spinal deformity in pediatric idiopathic scoliosis. The primary outcome was incidence of treatment-emergent adverse events, with a timeframe of up to 2 years. The record describes capturing intra-operative and post-intervention medical events, including signs and symptoms of complications arising after the study intervention began. It also says event descriptions, onset and end dates, severity, outcomes, and relationship to the intervention would be documented.
The registry lists pre-operative and post-operative Cobb angle and SRS 30 scores as secondary outcomes. Their numerical results and any analyses comparing those measurements are not reported in the registry record. The record lists the study as completed, with start and primary completion dates of 2017-07-12 and 2022-01-26, respectively. Completion status does not establish that every participant contributed observations through the full follow-up timeframe: 4 participants were withdrawn before the 2 year completion date after needing re-operation related to an anticipated device SAE. Data for those participants were obtained before withdrawal.
The registry does not report a statistical analysis plan or a sample-size justification. The posted information therefore supports a description of the design and reported safety counts, but not a claim about comparative treatment effects.
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 | Anterior Vertebral Tethering |
|---|---|
| STARTED | 20 |
| COMPLETED | 16 |
| NOT COMPLETED | 4 |
Reasons for not completing this period:
| Reason | Anterior Vertebral Tethering |
|---|---|
| Withdrawn due to need for re-operation related to an anticipated device SAE | 4 |
Analysis population for the primary outcome, as defined in the registry: Four of the subjects were withdrawn from the study prior to the 2 year completion date due to need for re-operation related to an anticipated device SAE. All data reported for these subjects were obtained prior to withdrawal.
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 | Anterior Vertebral Tethering |
|---|---|---|
| Participants analysed | 20 | |
| Age, Continuous | years | 12 (SD 1.94) |
| Age, Customized: Age at first diagnosis of Idiopathic Scoliosis | years | 9 (SD 2.38) |
| Sex: Female, Male: Female | Participants | 16 |
| Sex: Female, Male: Male | Participants | 4 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 1 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 19 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 1 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 4 |
| Race (NIH/OMB): White | Participants | 15 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | participants | 20 |
| Menarche status: Yes | Participants | 6 |
| Menarche status: No | Participants | 10 |
| Menarche status: N/A, Male | Participants | 4 |
| Height (cm) | cm | 159.4 (SD 12.43) |
| Weight (kg) | kg | 45.8 (SD 13.82) |
| Degree of thoracic rib hump | Degrees | 13 (SD 4.64) |
| Thoracic Rib Hump Side: Right | Participants | 20 |
| Thoracic Rib Hump Side: Left | Participants | 0 |
| Degree of lumbar rib hump | Degrees | 6 (SD 2.72) |
| Lumbar rib hump side: Left | Participants | 20 |
| Lumbar rib hump side: Right | Participants | 0 |
| Coronal Thoracic Cobb Angle | Degrees | 51.5 (SD 7.25) |
6. Primary Endpoint
The registry lists the primary outcome as Incidence of Treatment-Emergent Adverse Events, measured over up to 2 years.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary outcome is the incidence of treatment-emergent adverse events among participants receiving anterior vertebral tethering. The stated timeframe is up to 2 years. The registry description includes intra-operative events and medical events, signs, or symptoms of complications arising after the intervention began. It also describes recording each event’s onset, end date, severity, outcome, and relationship to the intervention, with device-related and non-device-related events distinguished.
The outcome is expressed as a count of participants with an event. That participant-based measure addresses how many people experienced an event, rather than how many event episodes occurred. A participant could experience more than one event, but the posted participant count alone does not show the number, timing, or pattern of episodes. The registry’s safety figures separately list participants with serious and other adverse events; these counts should not be treated as a complete event-by-event account.
Safety outcomes are relevant to a study whose stated aim is to assess the safety and feasibility of a procedure and device. However, a participant count by itself does not establish whether an event was caused by the intervention, how events compare with another approach, or what the risk would be in a different population. The registry description says relationship to the intervention was to be documented, but detailed event-level attribution results are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry reports 6 participants with serious adverse events among 20 at risk. It also reports 20 participants with other adverse events among 20 at risk, and 0 deaths. The most frequent serious adverse-event term listed is Grade IIIB, at 30.0%. These are descriptive safety figures from a single-group study. They do not estimate a difference between anterior vertebral tethering and another procedure or an untreated group.
The participant counts describe whether people were recorded as affected, not how many event episodes occurred. They do not show when events arose, how long they lasted, or whether multiple events occurred in the same participant. Although the registry description says event timing, severity, outcome, and relationship to the intervention were to be recorded, detailed results for those characteristics are not reported in the registry record. The listed Grade IIIB term is a category, not a substitute for the full event descriptions or clinical context.
Follow-up requires particular care in interpretation. The outcome timeframe extends up to 2 years, but 4 participants were withdrawn before the 2 year completion date because they needed re-operation related to an anticipated device SAE. The record says their data were obtained before withdrawal. It does not provide individual follow-up duration, an account of which observations contributed to each safety count, or a complete explanation of how withdrawal affected outcome ascertainment. The withdrawal information is important context, but the registry record does not establish whether those participants overlap with a particular posted event count.
No confidence intervals or inferential analyses for the primary outcome are reported in the registry record. A confidence interval would express the statistical uncertainty around an estimated quantity; without one, the posted counts do not indicate how precisely an underlying event frequency has been estimated. In general, estimates from a small group can be uncertain, and a single-group design cannot separate intervention-associated outcomes from other explanations. No unadjusted recalculation or comparison is appropriate from the posted figures alone.
The secondary outcomes are named, but their results are not reported in the registry record. Thus, the available numerical results characterize reported safety counts, not changes in Cobb angle or SRS 30 scores. The record also does not report a prespecified analysis population, adjustments for missing observations, or a statistical plan. These omissions limit what can be concluded about completeness, precision, and the intended analysis.
9. Statistical Methods Explained
What does a participant count measure?
The primary outcome is defined as a count of participants who experienced treatment-emergent adverse events. In general, a participant-level count records whether each person had an event during the specified observation period. It differs from a count of event episodes: repeated events in one person may be represented differently from events in separate people. The registry lists 6 participants with serious adverse events and 20 with other adverse events, with 20 at risk for each category. Those counts are descriptive, and the record does not give episode-level detail alongside them.
The event timeframe is up to 2 years. This defines the intended observation window, not evidence that each participant completed that duration. The record specifically notes that 4 participants were withdrawn before the 2 year completion date after needing re-operation related to an anticipated device SAE, with their data collected before withdrawal. The available record does not detail participant-specific observation time or how the safety outcome was handled after withdrawal.
Why does the single-group design matter?
In general, a comparison group helps distinguish outcomes observed after an intervention from outcomes that might also occur without it or under another approach. This study is recorded as single-group, with no randomized comparison or separate control group. Its participant counts can describe what was recorded in the enrolled group, but cannot estimate a comparative effect. A before-and-after assessment of a secondary measure can describe change within participants if results and an analysis are available; it does not by itself provide a randomized comparison. Numerical results for the listed Cobb angle and SRS 30 outcomes are not reported in the registry record.
How should uncertainty be considered?
In general, a confidence interval gives a range of values compatible with the observed data under a specified statistical method. It helps readers assess precision, rather than treating a point estimate as exact. No confidence interval for the primary safety outcome is reported in the registry record. The counts therefore do not quantify statistical uncertainty, and no interval should be inferred from them in this account.
General methods for binary outcomes often model whether each participant did or did not experience an event. Such methods rely on assumptions about the data and the analysis population. This record does not report a fitted model, a test, or an analysis plan for the primary outcome. It also does not report enough event-level information to assess whether a more detailed model would be suitable. No model-based interpretation or p-value is available from the registry record.
What do the planning illustrations represent?
Planning sample sizes are different from observed results. The record describes planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a fraction of the observed effect. For time-to-event illustrations, the stated quantity is total events; other illustrations refer to participants per arm. These are planning assumptions, not evidence that the trial was designed with those assumptions, and not observed power.
Those assumptions also describe a two-arm planning setup, whereas the registered study is single-group and has no like-for-like control comparison. They should not be read as a description of the actual study design or as a justification for its enrollment. The sample-size justification for this study is not reported in the registry record. Nor are numerical planning results or the observed effect used for any illustration reported in the registry record.
What analysis details are absent?
The registry record does not report an analysis plan, a named statistical test, a confidence interval, or a p-value for the primary outcome. It also does not report whether any adjustment was made for participant characteristics or follow-up differences. The record identifies 3 outcome measures and lists the primary and secondary outcomes, but the analysis details and numerical secondary results are not reported. Without those details, interpretation should remain descriptive: the posted counts indicate how many participants were recorded in each adverse-event category, not a tested hypothesis or a causal estimate.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary safety outcome and secondary outcomes comparing pre-operative and post-operative Cobb angle and SRS 30 scores. Considering multiple outcomes can raise multiplicity concerns: in general, when several statistical tests are performed, the chance of at least one apparently notable result can increase. Whether that issue applies to the study’s analyses depends on which tests were planned and performed. The statistical plan, testing hierarchy, and any multiplicity adjustment are not reported in the registry record. No outcome analyses are listed.
Missing data also affect interpretation. The adverse-event timeframe is up to 2 years, but 4 participants were withdrawn before the 2 year completion date after requiring re-operation related to an anticipated device SAE. The registry says data for these participants were obtained before withdrawal. It does not report how much follow-up each participant contributed, whether any observations were missing before withdrawal, or how outcomes after withdrawal were handled. The record does not describe imputation, sensitivity analyses, or another missing-data method.
The registry does not specify an analysis population, such as a population defined by treatment received or by a prespecified eligibility rule. The number enrolled is 20, but the record does not state which participants were included in each endpoint analysis. Consequently, the enrollment count should not be assumed to be the denominator for every outcome beyond the explicit at-risk counts in the safety figures. The registry’s lack of reported analyses leaves uncertainty about the handling of withdrawals, outcome availability, and the intended population for statistical inference.
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 |
|---|---|---|---|
| Anterior Vertebral Tethering | 6 | 20 | 30.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Anterior Vertebral Tethering | 0 of 20 |
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 |
|---|---|
| Anterior Vertebral Tethering | 20 of 20 |
Most frequent serious adverse event terms
| Event term | Organ system | Anterior Vertebral Tethering |
|---|---|---|
| Grade IIIB | Injury, poisoning and procedural complications | 6 of 20 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Anterior Vertebral Tethering |
|---|---|---|
| Grade I | Respiratory, thoracic and mediastinal disorders | 20 of 20 |
| Grade I | Musculoskeletal and connective tissue disorders | 16 of 20 |
| Grade I | Gastrointestinal disorders | 12 of 20 |
| Grade I | Skin and subcutaneous tissue disorders | 6 of 20 |
| Grade I | General disorders | 3 of 20 |
| Grade I | Product Issues | 3 of 20 |
| Grade II | Injury, poisoning and procedural complications | 1 of 20 |
| Grade I | Cardiac disorders | 1 of 20 |
| Grade I | Psychiatric disorders | 1 of 20 |
Serious events with the highest arm-level rate: grade iiib (30.0%).
The registry lists 6 participants with serious adverse events among 20 at risk, 20 participants with other adverse events among 20 at risk, and 0 deaths. These are participant counts in the anterior vertebral tethering group. The most frequent serious adverse-event term is Grade IIIB, reported as 30.0%. The record does not provide a full event-level breakdown or enough detail to interpret the grading category beyond its label.
These figures should not be added together: the record does not say whether participants with serious events also appear in the other adverse-event count. Nor do participant counts indicate the total number of episodes, their duration, or the extent to which events were considered related to the device. Although the outcome description says device-related and non-device-related events would be distinguished, detailed attribution results are not reported in the registry record.
The record also notes that 4 participants were withdrawn before the 2 year completion date because of re-operation related to an anticipated device SAE. Their data were collected before withdrawal. It does not state whether these participants overlap with a particular safety category, so that relationship should not be assumed. With no comparator group, the counts describe the study group and do not provide a comparative risk estimate.
12. What the Result Does, and Does Not, Mean
The posted results provide descriptive safety information for a single group of participants who received anterior vertebral tethering. They report the number of participants recorded with serious and other adverse events, as well as deaths. The stated primary outcome and event-collection description make clear that safety was a central study question. The withdrawal information is also relevant context when considering the intended follow-up of up to 2 years.
These results do not establish how the observed counts compare with outcomes under another treatment or without the intervention. There is no separate control group, and the study is not recorded as a randomized comparison. The counts alone also do not establish that the intervention caused a particular event. The registry description includes plans to record the relationship between events and the intervention, but detailed attribution findings are not reported in the registry record.
The registry lists pre-operative and post-operative Cobb angle and SRS 30 scores as secondary outcomes, but their results are not reported in the registry record. Thus, the available information does not support a numerical account of change in those measures. Nor does it include confidence intervals or other inferential analyses to quantify uncertainty in the safety counts.
The record is marked completed, but 4 participants were withdrawn before the 2 year completion date after needing re-operation related to an anticipated device SAE. Their data were collected before withdrawal. The registry does not report the completeness of follow-up for the remaining participants or the post-withdrawal outcome handling. The findings should therefore be read as the safety information recorded in this study, with these limits, rather than as a complete comparative evaluation or a result applicable to every patient group.
13. Why This Trial Matters Statistically
This study illustrates a basic distinction in clinical trial interpretation: a count observed in a treated group is not the same as an estimate of what the treatment changed. The registry reports participant counts for adverse-event categories, but the single-group design supplies no concurrent control for comparison. Statistical description can summarize observed outcomes, while causal or comparative questions require design and analysis features that support those inferences.
It also demonstrates why outcome definitions and denominators matter. The primary outcome is a participant count, and the registry gives at-risk counts for the serious and other adverse-event categories. These counts are not episode totals, and the record does not provide event-level detail alongside them. The stated timeframe is up to 2 years, while 4 participants were withdrawn before the 2 year completion date after needing re-operation related to an anticipated device SAE. Interpreting safety data therefore requires attention to both the outcome definition and follow-up.
Another statistical issue is the difference between study enrollment and a sample-size justification. The record lists an enrollment of 20 but does not report the rationale for that enrollment or a statistical analysis plan. Planning illustrations using two-arm assumptions are not a description of this single-group study and are not observed power. Finally, named secondary outcomes without reported numerical results show why outcome registration and outcome reporting are distinct: knowing which measures were planned does not supply their results or the uncertainty around them.
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.
The principal design limitation is the absence of a comparator group. Because the study is single-group and not a randomized comparison, its safety counts cannot estimate how outcomes differ from those under another approach. Masking is listed as none. The registry does not report a statistical analysis plan, sample-size justification, confidence intervals, or inferential analyses, which limits assessment of precision and the intended methods.
The registry lists an enrollment of 20. The safety figures are participant counts, and detailed event-level information is not reported in the registry record. The record does not provide individual event timing, duration, outcomes, or detailed relationship-to-device findings, despite describing those items as information to be captured. The listed Grade IIIB term is not accompanied by further detail in the record.
Follow-up is another limitation. The primary outcome timeframe is up to 2 years, and 4 participants were withdrawn before the 2 year completion date after needing re-operation related to an anticipated device SAE. Their data were obtained before withdrawal, but the registry does not report participant-specific observation time, subsequent event ascertainment, or how withdrawal affected each outcome analysis. It does not identify an analysis population or describe missing-data methods.
Finally, the registry names Cobb angle and SRS 30 scores as secondary outcomes but does not report their numerical results. The available record therefore cannot establish the size or precision of changes in those measures. The completed status does not resolve these reporting limitations or show that every participant completed the intended follow-up.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Vertebral Body Tethering Outcomes for Pediatric Idiopathic Scoliosis — NCT03194568.
- Registry record last updated 2024-09-23; status last verified 2024-09.
- Results first posted 2024-09-23.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
The registry describes a completed, single-group study of anterior vertebral tethering in pediatric idiopathic scoliosis, with enrollment of 20 and no masking. The primary outcome is incidence of treatment-emergent adverse events through up to 2 years. The posted safety figures list 6 participants with serious adverse events among 20 at risk, 20 with other adverse events among 20 at risk, and 0 deaths; Grade IIIB is the most frequent serious adverse-event term, at 30.0%.
Four participants were withdrawn before the 2 year completion date after needing re-operation related to an anticipated device SAE; data for them were collected before withdrawal. Pre-operative and post-operative Cobb angle and SRS 30 scores are listed as secondary outcomes, but their results are not reported in the registry record. No comparative analyses, confidence intervals, or statistical analysis plan are reported, so the posted counts should be interpreted descriptively.