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 Observational Clinical Study to Plan, Position and Check Instrument Placement for Spine Surgery Interventions (NCT03015142), a registered phase not stated study. The primary outcome is Clinical Accuracy of Pedicle Screw Placement Using New Image-guidance Software.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03015142 |
| Phase | Phase not stated |
| Condition | Spinal Diseases |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 21 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Philips Clinical & Medical Affairs Global |
| Results posted | Yes |
2. Clinical Question
Population
People undergoing spine surgery for spinal diseases. The record says 20 subjects were treated with new image-guidance software and one was treated by the conventional free-hand method. It also reports 253 screws placed with the software: 163 in thoracic, 77 in lumbar and 13 in sacral regions.
Intervention
New image-guidance software used during spine surgery, with the study focused on its use for planning, positioning and checking instrument placement.
Comparator
A conventional free-hand method is mentioned for one subject. Allocation is not stated, and the registry record does not describe a like-for-like control comparison.
Primary question
What percentage of screw placements made using the new image-guidance software were judged accurate by three independent reviewers using Gertzbein classification?
The study’s stated objective was to investigate screw-placement accuracy. The clinical concern described in the record is accurate placement relative to important structures, including the spinal cord, nerve roots and vertebral arteries. The primary outcome is expressed as a percentage of screw placements, not as a patient-level proportion. The record says grading was conducted per screw, but it does not report the numerical percentage judged accurate or its confidence interval.
3. Trial Design
This was an observational clinical study, not a randomized comparison. The registry record identifies Philips Clinical & Medical Affairs Global as the sponsor and gives the study status as completed. The listed start date is 2016-11-09, and the primary completion date is 2017-10-08. Enrollment was 21.
The study examined new image-guidance software during spine surgery. The registry describes 20 subjects treated with the software and one treated using conventional free-hand screw placement. It reports 253 screws placed with the software across thoracic, lumbar and sacral regions. The record does not state how participants were allocated to the methods, or describe a design that would make the two methods comparable. The free-hand case therefore should not be treated as a control group suitable for estimating a comparative treatment effect.
The primary outcome was clinical accuracy of pedicle-screw placement, assessed by three independent reviewers using Gertzbein classification. The stated timeframe was during surgery, with a mean of 6.71 hours. The listed secondary outcomes include procedure time, time to insert a pedicle screw, length of hospitalization, System Usability Score, patient radiation dose, operator effective radiation dose and procedure-related complications. Patient radiation dose appears twice in the registry’s outcome list.
The registry record does not report a protocol rationale for the enrollment, an allocation method, or a detailed statistical analysis plan. Although the study is marked completed, numerical primary-outcome results are not reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | New Image-guidance Software |
|---|---|
| STARTED | 21 |
| COMPLETED | 20 |
| NOT COMPLETED | 1 |
Analysis population for the primary outcome, as defined in the registry: 20 subjects were treated with the new image-guidance software. One was treated in the conventional method placing screws by free-hand method. Total of 253 screws (163 in thoracic, 77 in lumbar and 13 in sacral regions) were placed with new image-guidance software.
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 | New Image-guidance Software |
|---|---|---|
| Participants analysed | 21 | |
| Age, Categorical: <=18 years | Participants | 10 |
| Age, Categorical: Between 18 and 65 years | Participants | 9 |
| Age, Categorical: >=65 years | Participants | 2 |
| Sex: Female, Male: Female | Participants | 12 |
| Sex: Female, Male: Male | Participants | 9 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 0 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 21 |
| Region of Enrollment: Sweden | participants | 21 |
6. Primary Endpoint
The registry lists the primary outcome as Clinical Accuracy of Pedicle Screw Placement Using New Image-guidance Software, measured over During surgery, mean 6.71 hours.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | Percentage of screw placements |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the percentage of pedicle-screw placements judged accurate using the new image-guidance software. Three independent reviewers assessed placement using Gertzbein classification, which grades the degree of breach: grade 0 is breach 0 mm, grade 1 is breach < 2 mm, grade 2 is breach 2-4 mm, and grade 3 is breach > 4 mm. The record says the reported values represent the percentage of screw placements determined accurate by those reviewers, but it does not state a numerical accuracy estimate or give a numerical confidence interval.
Accuracy is a relevant procedural outcome because the study rationale identifies nearby important structures as a concern in spine surgery. A screw-level percentage describes how often placements meet the study’s accuracy assessment; it does not, by itself, describe patient-level outcomes or establish a comparison with another method. The registry does not specify which Gertzbein grades were counted as accurate, so the precise threshold used to form that percentage is not reported in the registry record.
The stated timeframe is during surgery, with a mean of 6.71 hours. This describes the recorded assessment period, not a stated long-term follow-up interval. The outcome is specified as a number with a 95% confidence interval, but neither the estimate nor interval is reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes the intended accuracy measure and the people and screws assessed, but it does not provide the numerical primary result. Consequently, the percentage judged accurate and the precision of that estimate cannot be interpreted from the registry record. A stated 95% confidence interval is a reporting format, not a result in itself; without its endpoints, it cannot show which accuracy values are compatible with the observed data.
The denominator matters for understanding the endpoint. Accuracy was assessed per screw, and the record reports 253 screws placed with the software. Those screw placements are clustered within subjects rather than being independent observations by definition. A statistical analysis that treats every screw as unrelated could understate uncertainty if placements within a subject tend to resemble one another. The registry record does not report how clustering was handled, or provide the numerical analysis needed to assess this issue.
The record also mentions one subject treated using the conventional free-hand method, but allocation is not stated and the arms are not a like-for-like control comparison. The single conventional case cannot support a reliable comparative estimate. The study therefore addresses a descriptive question about software-assisted placements, rather than providing a randomized estimate of the difference between methods.
The listed adverse-event figures are separate from the primary accuracy outcome. The record reports one serious adverse event among 20 at risk in the software group and four other adverse events among 20 at risk; it also records no deaths. These counts do not fill the gap in the accuracy results and should not be interpreted as a comparative safety analysis.
Planning calculations based on an observed effect are illustrations for future study design, not observed power and not findings from this completed study. Because the registry record does not report the primary numerical effect, those calculations cannot be independently interpreted from the registry information. Overall, the record supports a description of the study’s question and measurement approach, but not a conclusion about the measured accuracy rate or a comparative effect.
9. Statistical Methods Explained
What does a confidence interval communicate?
In general, a confidence interval expresses uncertainty around an estimated quantity. For a percentage of placements judged accurate, the interval would give a range of values compatible with the data under the method used to calculate it. A narrow interval would indicate greater statistical precision than a wide interval, but neither width nor location can be assessed without the actual estimate and interval endpoints. The registry record specifies a 95% confidence interval as the dispersion measure, but does not report its numerical limits.
Why does the unit of analysis matter?
The primary outcome is defined per screw, while treatment is described at the subject level. Screws placed in the same subject may share anatomy, surgical circumstances or operator conditions. In general, such within-subject similarity means that each screw should not automatically be treated as an independent piece of information. Methods that account for clustering can produce more appropriate uncertainty estimates when observations are grouped. The registry record does not report whether clustering was considered, what analysis was used, or how reviewer assessments were combined.
What does the Gertzbein grading contribute?
The grading system records the degree of breach for each placement: grade 0 corresponds to breach 0 mm, grade 1 to breach < 2 mm, grade 2 to breach 2-4 mm, and grade 3 to breach > 4 mm. A categorical grading scheme can make the assessment more structured than an undefined judgment of accuracy. However, translating grades into a single accuracy percentage requires a rule about which grades count as accurate. The record does not specify that rule. It says three independent reviewers assessed accuracy, but does not report their separate assessments, agreement, or the procedure used to resolve disagreement.
How should a descriptive result differ from a comparison?
A descriptive percentage would report the observed proportion of placements meeting the accuracy definition among the software-assisted placements. A comparative analysis would instead estimate how outcomes differ between methods, with uncertainty around that difference. The registry describes 20 subjects treated with software and one treated with the conventional free-hand method, and says allocation was not stated. This is not a like-for-like control comparison. A numerical difference between those groups, if one were available, could reflect differences in the subjects or circumstances as well as the method. The registry record does not report a comparative estimate or analysis.
What are recalculated and planning estimates?
In general, a recalculated estimate based on posted summary statistics is an unadjusted calculation and may not reproduce an analysis that accounts for the original design or uses additional information. If a discrepancy is identified between a sponsor analysis and a recalculation, the sponsor’s own analysis takes precedence. No numerical primary result or analysis is reported in the registry record, so an unadjusted recalculation cannot be interpreted from this information.
Planning sample sizes are hypothetical design illustrations, not observed results and not observed power. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect set to a stated fraction of the observed effect. Those assumptions do not establish that the study used that design. The registry record does not report the study’s own sample-size justification, and it does not provide the observed primary effect needed to interpret an effect-based planning illustration. For time-to-event outcomes, the stated convention is a total number of events; for other outcomes, it is participants per arm. This convention describes the planning calculation, not the enrollment or outcome findings of this study.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists multiple secondary outcomes, including procedural timing, hospitalization, usability, radiation exposure and complications. Patient radiation dose appears twice in the listed outcomes. When a study examines several outcomes, the chance of finding an apparently notable result by chance can increase if many statistical tests are conducted without an appropriate plan. In general, methods for handling multiplicity may include identifying a primary outcome in advance or adjusting how multiple comparisons are interpreted. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or numerical results for those outcomes.
The registry identifies a primary accuracy outcome and lists 10 outcome measures, but it reports zero analysis entries. The numerical primary estimate, confidence interval and analysis details are not reported in the registry record. The record also does not state how missing observations, incomplete reviewer assessments or unavailable outcome measurements were handled. Missing-data methods can affect estimates when the availability of data is related to the outcome; without a description of missingness or analysis, that possibility cannot be evaluated.
The analysis population is not defined in detail. The record gives the number of subjects treated with the software and the screw placements made with it, but does not state whether every treated subject or every placement was included in each analysis. It also does not report how the conventional free-hand case was handled analytically. These omissions limit assessment of the analysis population and of whether the reported outcome, if available, would correspond to all eligible placements or a subset.
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 |
|---|---|---|---|
| New Image-guidance Software | 1 | 20 | 5.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| New Image-guidance Software | 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 |
|---|---|
| New Image-guidance Software | 4 of 20 |
Most frequent serious adverse event terms
| Event term | Organ system | New Image-guidance Software |
|---|---|---|
| Pain right leg due to foramina stenosis by L5 screw. Screw was placed by free-hand. | Surgical and medical procedures | 1 of 20 |
Most frequent non-serious adverse event terms
| Event term | Organ system | New Image-guidance Software |
|---|---|---|
| Horner's syndrome | Surgical and medical procedures | 1 of 20 |
| Postoperative pain | Surgical and medical procedures | 1 of 20 |
| Repeated Xper-CT | Surgical and medical procedures | 1 of 20 |
| Urticaria | Surgical and medical procedures | 1 of 20 |
Serious events with the highest arm-level rate: pain right leg due to foramina stenosis by l5 screw. screw was placed by free-hand. (5.0%).
For the New Image-guidance Software group, the registry reports one serious adverse event among 20 at risk and four other adverse events among 20 at risk. It reports no deaths. The listed serious-event term is “Pain right leg due to foramina stenosis by L5 screw. Screw was placed by free-hand.” The record gives 5.0% for this serious-event term.
That event description specifically says the screw was placed by the free-hand method, even though the figures appear under the software group. This makes the event’s relationship to the software group unclear in the registry record. The figures should therefore be read as registry-reported counts, not as evidence that the software caused or prevented an event. The record does not provide a comparison suitable for estimating relative safety, nor does it report enough detail about event timing, severity beyond the serious-event classification, or causal assessment to resolve the discrepancy.
Adverse-event counts are distinct from the primary accuracy outcome. They do not establish the rate of accurate placement or explain whether a particular placement was clinically consequential.
12. What the Result Does, and Does Not, Mean
The study asks a clinically relevant procedural question: how accurately were pedicle screws placed when new image-guidance software was used? Its primary outcome was designed to describe the percentage of placements judged accurate by independent reviewers using a graded classification. The record also identifies the number of software-treated subjects and screw placements and the anatomical regions in which screws were placed.
However, the registry record does not report the numerical accuracy percentage or its 95% confidence interval. It therefore cannot establish the observed accuracy rate or how precisely that rate was estimated. The missing result is not evidence of a high or low accuracy rate; it means the registry record does not report the value needed to answer that descriptive question.
The study also does not establish that the software is more accurate than free-hand placement. The record describes one conventional free-hand case, does not state allocation, and does not describe a like-for-like control comparison. A comparison would require an appropriate design and analysis to separate a method effect from differences in subjects or surgical circumstances.
Nor does the record establish broader patient benefit, long-term outcomes, or comparative safety. Although secondary outcomes and adverse events are listed, numerical results for most outcomes are not reported. The serious-event description itself refers to a free-hand screw while appearing under the software group, so its group attribution is unclear.
The appropriate interpretation is limited to the study’s stated aim, measurement approach and reported descriptive details. Numerical conclusions about accuracy, comparative effectiveness or safety are not reported in the registry record.
13. Why This Trial Matters Statistically
This study illustrates an important statistical distinction: an outcome can be defined in detail even when its numerical result is unavailable. The registry specifies a screw-level accuracy measure, a grading system and independent reviewers. Those details help explain what the investigators intended to assess, but they cannot substitute for the estimate and its uncertainty.
It also highlights the difference between the number of placements and the number of subjects. Multiple screws were placed within subjects, so statistical precision depends not only on the count of screws but also on how observations within a subject are related and how that relationship was handled in analysis. The registry record does not report that analytic detail. Without it, readers cannot assess whether the uncertainty calculation appropriately reflects the study structure.
Finally, the record shows why design matters when interpreting comparisons. A conventional free-hand case is mentioned, but allocation is not stated and the comparison is not like-for-like. Descriptive data from software-assisted placements may address what was observed in those cases, but they do not by themselves estimate what would have happened under another method.
For clinical researchers, these distinctions separate a clearly posed measurement question from a supported statistical conclusion. The registry record provides useful context about the endpoint and study conduct, while the absent result and analysis details prevent an assessment of the primary estimate, its precision, and any comparative effect.
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 primary limitation for interpreting this record is that the numerical accuracy result is not reported. Although the outcome is specified as a percentage with a 95% confidence interval, neither the percentage nor interval endpoints are available in the registry record. The definition of which Gertzbein grades count as accurate is also not stated.
The study is observational, allocation is not stated, and the one conventional free-hand case does not provide a like-for-like control comparison. The record does not describe adjustment for differences between subjects or surgical circumstances. It also does not report the method used to account for multiple screws within subjects, how three reviewers’ assessments were combined, or whether reviewer agreement was examined.
The registry does not report missing-data procedures, analysis populations, or a detailed statistical plan. Although secondary outcomes are listed, their numerical results and any strategy for interpreting multiple outcomes are not reported. The adverse-event listing contains a group-attribution ambiguity: the serious-event term describes a screw placed by free-hand while appearing under the software group.
These limitations concern what can be concluded from the registry record; they do not establish that a particular analysis or procedure was absent from the study itself. The registry record does not report whether additional analyses or documentation exist elsewhere.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Observational Clinical Study to Plan, Position and Check Instrument Placement for Spine Surgery Interventions — NCT03015142.
- Registry record last updated 2022-03-08; status last verified 2022-03.
- Results first posted 2019-09-30.
- 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
NCT03015142 is a completed observational study sponsored by Philips Clinical & Medical Affairs Global. It examined new image-guidance software for spine surgery, with clinical accuracy of pedicle-screw placement as the primary outcome. The registry reports enrollment of 21, including 20 subjects treated with the software and one treated by the conventional free-hand method. It records 253 software-assisted screw placements across thoracic, lumbar and sacral regions.
Three independent reviewers assessed screw placement using Gertzbein classification. The primary outcome was specified as a percentage with a 95% confidence interval, but the numerical result is not reported in the registry record. The record also lists procedural, hospitalization, usability, radiation and complication outcomes. It reports adverse-event counts for the software group, while the serious-event description refers to a free-hand screw, leaving its group attribution unclear.
The study’s descriptive aim and measurement approach are identifiable, but its numerical accuracy result, analysis details and a suitable comparative estimate are not reported in the registry record.