Driving After Cervical Spine Surgery: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Driving After Cervical Spine Surgery (NCT02782923), a non-randomized na study. The primary outcome is Change in Number of Total Collisions (TC).

2. Clinical Question

In practical terms, the study asks whether driving-simulator performance, represented by collisions, differs between the baseline assessment and the follow-up assessment after cervical spine procedures. The record describes the aim as delineating the effect of cervical spine procedures on driving performance during the peri-operative period. It does not establish that every listed procedure group is compared directly with every other group, or that the control group provides a randomized counterfactual. The non-randomized allocation and the registry’s own warning about the arms matter when interpreting any between-group display.

The record identifies the outcome and its intended time points, but does not give a directional hypothesis, a clinically important threshold, or a definition of what size of change would be meaningful. Those details are not reported in the registry record. The clinical question can therefore be described, but the registry entry alone cannot answer whether performance changed, how large any change was, or whether a change should be considered important.

3. Trial Design

This is a prospective, single-center simulation study concerning driving performance around cervical spine surgery. The registry lists a single-group model, non-randomized allocation, and no masking. Although the study summary describes a controlled simulation study, the record cautions that the listed arms are not a like-for-like control comparison. The labels include single-level anterior cervical discectomy fusion, multi-level anterior cervical discectomy and fusion, cervical disc replacement, posterior laminectomy and fusion, posterior cervical decompression, and a control group. The description of the control group is not reported in the registry record.

The registry lists the STISIM driving simulator as the device used in the study. Its summary describes the simulator as validated and says the study was designed to compare and evaluate driving performance among people who had cervical spine surgery. The stated enrollment is 19. The listed primary outcome is measured at baseline and 3 months, and the record marks the study as completed. The study start is recorded as 2016-12, with primary completion on 2018-07-17.

The surgeries were to take place at New York University Langone Medical Center - Hospital for Joint Diseases, with follow-up visits at the NYU Center for Musculoskeletal Care. The sponsor is NYU Langone Health. These details locate the study but do not resolve how people were assigned to the procedure groups, whether the control group was recruited in the same way, or whether participants completed both assessments. Those details are not reported in the registry record.

Because assignment was non-randomized, procedure-group differences may reflect differences in participant characteristics or clinical circumstances as well as differences associated with the procedures. The record does not describe an adjustment strategy to address such differences. The listed single-group model also advises caution about treating the arm labels as a conventional randomized trial comparison. The registry entry does not provide a protocol or a detailed account of the study procedures beyond the summary and outcome description.

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 Change in Number of Total Collisions (TC), measured over Baseline, 3 months.

The primary endpoint is change in the number of total collisions in the driving simulator from baseline to 3 months. Total collisions include both off-road and on-road collisions. The record specifies the summary measure as a median and the dispersion as a full range. The outcome is expressed in collisions/crashes.

A collision count gives a direct measure of errors or incidents recorded during a simulated drive. Combining off-road and on-road collisions creates an overall collision measure, rather than restricting the outcome to one type of event. A baseline-to-follow-up comparison can describe how the recorded collision count changes over the observation period. The registry labels the change as “BL-3mo”; it does not provide a separate explanation of the calculation convention.

Using the median is a way to describe the center of a distribution without having extreme observations exert as much influence as they can on an arithmetic mean. Reporting the full range conveys the lowest and highest observed values, although it does not describe how observations are distributed between those extremes. These are general statistical properties, not evidence about the actual distribution in this study.

The registry record identifies the endpoint and time points but does not report a median change, full-range values, or an estimate of uncertainty. It also does not describe a threshold for a clinically important change. As a result, the endpoint’s definition is clear at a broad level, but the registry entry does not show what the observed data indicate.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a median and full range for the primary outcome, but does not report the analysis used to estimate change or compare time points. It lists 3 outcome measures and 0 analyses. The descriptions below explain general statistical concepts; they should not be read as a claim that a particular method was applied in this study.

What does a median describe?

The median is the middle value after observations are ordered. It is often useful for outcomes whose distributions are skewed or include unusually large values, because a small number of extreme observations has less influence on the median than on an arithmetic mean. For collision counts, the median can describe a typical observation in the sample without implying that every participant had a value close to it. A median alone does not show the shape of the distribution or how variable individual observations are.

The registry also specifies the full range. A range reports the lowest and highest values, so it shows the span of the data. It does not show whether most observations cluster near the middle, whether values are concentrated near one end, or whether the extremes are unusual. Together, a median and range offer a compact description, but they do not replace participant-level data or a fuller account of uncertainty.

How should a change outcome be understood?

A change outcome is based on measurements at different time points. The registry names baseline and 3 months and describes the endpoint as change from baseline in overall collisions, with “BL-3mo” in the description. It does not report the numerical change or separately explain the calculation convention. Repeated measurements from the same participant are generally related, so a method that treats each time point as unrelated could fail to account for that dependence. This is a general consideration; the registry record does not say which method was used.

Analysts may summarize change for each participant and then describe the distribution of those changes, or they may model measurements across time. The choice depends on the study design, outcome distribution, missingness, and analysis objective. For count outcomes, the distribution may be asymmetric, and counts may vary more than a simple statistical model expects. The registry does not report whether a count model, a nonparametric method, a paired comparison, or another approach was used.

Why can count data need special care?

Collision counts are non-negative counts, rather than continuous measurements. A common count-model assumption is that the variability follows a specified relationship to the average count. Over-dispersion occurs when the data vary more than that model expects. If over-dispersion is present and not accommodated, standard errors can be too small and statistical evidence can appear more precise than it is. This is a general explanation, not a finding about the collision data in this study. The registry record does not report a distributional assessment, model choice, or method for handling over-dispersion.

Counts can also include many zeros or be affected by differences in simulator exposure, if participants have different opportunities to experience a collision. An exposure adjustment can be relevant when observation time or driving distance varies, but the record does not describe such an adjustment or report exposure details. It would be inappropriate to assume that exposure was identical or that an offset was used.

What do uncertainty estimates add?

A confidence interval is a range of values compatible with the data and the model under stated assumptions. It helps convey precision: a narrow interval indicates more precise estimation than a wide interval, while neither width nor statistical significance alone establishes clinical importance. The registry record does not report a confidence interval for the primary outcome. No interval can therefore be used to assess the precision of the change estimate.

A p-value, when reported, describes how unusual data at least as extreme as those observed would be under a specified null model. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The registry record does not report a primary-outcome p-value or describe a test. No claim about statistical significance is supported by the entry.

How do the planning calculations relate to the study?

The record describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the target effect is a stated fraction of the observed effect. These are assumptions for an illustration, not evidence of the trial’s original design plan. The record does not report a sample-size justification for the study, and the illustrative calculations should not be called observed power. A sample-size calculation can describe the number of participants per arm for a chosen power under specified assumptions, but it cannot make an unavailable outcome result more conclusive.

The record also cautions that the study is non-randomized and that the arms are not a like-for-like control comparison. A simple unadjusted recalculation from posted summary statistics, if available, would not replace a sponsor’s own analysis. The registry’s discrepancy guidance says that when a discrepancy is identified, the sponsor’s own analysis takes precedence. No sponsor analysis is posted in the registry record, so there is no reported analysis to compare with a recalculation.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 3 outcome measures, but does not report an analysis for any of them. It does not describe a prespecified testing hierarchy, a primary family of hypotheses, or an adjustment for multiple comparisons. With multiple outcomes or group comparisons, repeated testing can increase the chance of apparently notable findings arising by chance. This is a general concern; the registry record does not report whether multiplicity was addressed in the study’s analysis plan.

The record names one primary outcome, change in total collisions from baseline to 3 months, but gives no numerical results or statistical test for it. It does not provide a statistical analysis plan, explain whether additional time points or subgroup comparisons were tested, or report interim analyses. Those details are not reported in the registry record. The record’s sample-size illustration is not evidence of a multiplicity plan or of the study’s original sample-size justification.

Missing-data handling is also not described. The registry does not report the number of primary-outcome observations available at baseline or 3 months, reasons for missing assessments, or whether an analysis included only participants with both measurements. It does not state whether imputation, a model using incomplete records, or another approach was used. Without that information, the possible influence of missing observations on the reported outcome cannot be assessed.

The analysis population is not described. The registry does not say whether the primary analysis included all enrolled participants, only those who completed simulator assessments, or another defined group. It lists enrollment of 19, while the adverse-event summaries list 17 at risk; the record does not explain the relationship between these counts. They should not be treated as evidence of the primary-outcome analysis population.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry’s adverse-event summary lists the group as “Cervical Surgical Patients.” It reports 17 at risk for serious adverse events and 0 affected, and 17 at risk for other adverse events and 0 affected. It also reports 0 deaths. These are the safety figures recorded in the registry entry; they are not a substitute for a detailed account of event definitions, collection procedures, or follow-up duration.

A count of 0 affected means that no events are recorded in that summary for the stated category and group. It does not establish that the possibility of an event is absent, and it does not show how complete event ascertainment was. The record does not report the specific serious-event terms, and no top serious-event terms are listed.

The registry lists enrollment of 19, whereas the adverse-event summaries list 17 at risk. The reason for this difference is not reported in the registry record. The safety denominators should be read as recorded, without inferring why they differ from enrollment or assuming they represent the population analyzed for the driving outcome. The entry does not give additional details that would support a more extensive safety interpretation.

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

The registry record establishes that a completed, prospective, single-center simulation study was conducted around cervical spine surgery, and it identifies change in total simulator collisions from baseline to 3 months as the primary endpoint. It also describes the outcome as including both on-road and off-road collisions and specifies a median with a full range. These details define what the study intended to measure.

The record does not provide numerical results for that endpoint. It therefore does not show whether the median collision count changed, in which direction it changed, how large any change was, or how precisely it was estimated. It does not report a test result or confidence interval. The study’s completion status and enrollment count do not answer the primary statistical question.

Even with results, a simulator measure would need to be interpreted as performance under the simulator assessment, not automatically as a direct measure of everyday driving. The record describes a validated simulator, but does not report details about simulator scenarios, exposure, or how closely the assessment represents real-world driving. A change over time could also be influenced by factors beyond the surgical procedure; the registry entry does not report methods for separating those influences.

The non-randomized design and the registry’s caution that the arms are not a like-for-like control comparison limit conclusions from comparisons among the listed groups. The entry does not describe random assignment or an adjusted analysis. It cannot establish from its design description alone that differences between groups were caused by procedure type.

The serious and other adverse-event summaries record 0 affected among 17 at risk in each category and 0 deaths. These entries describe what the registry reports, but do not establish that no adverse events could occur or clarify the relationship between those denominators and the stated enrollment of 19. Overall, the registry provides useful details about the study question and design, but not the results needed to answer the question about observed driving performance.

13. Why This Trial Matters Statistically

This study illustrates why a statistical interpretation begins with the design and endpoint, not just with a numerical summary. Driving performance is represented by a simulator-based collision count, measured at baseline and 3 months. Understanding that measure requires attention to the outcome’s count nature, the repeated assessments, and the fact that a median and full range do not provide the same information as an estimate with an uncertainty interval.

The registry also illustrates the importance of distinguishing group labels from valid comparison groups. Several procedure groups and a control group are listed, but allocation is non-randomized, the model is described as single group, and the record warns that the arms are not a like-for-like control comparison. Those features affect what can be inferred from any observed differences. A label alone does not establish comparability.

Another statistical lesson is that a completed study is not necessarily a results-complete registry entry. The record identifies the primary outcome and reports adverse-event counts, but provides no numerical primary-outcome results and lists 0 analyses. Without an estimate and an account of its precision, readers cannot evaluate the magnitude or uncertainty of the central finding.

Finally, planning illustrations must be kept separate from observed evidence. The registry describes an illustrative sample-size approach based on an observed effect and specified assumptions, while noting that it is not the trial’s own design. Such calculations are useful only as planning exercises under their assumptions; they are not observed power and cannot compensate for absent outcome results. These distinctions help keep conclusions proportional to what the registry actually records.

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 registry entry does not report numerical results for the primary endpoint, including its median change, full range, confidence interval, or test result. It lists 0 analyses. This is the most direct limitation for interpreting the study question: the record defines the outcome but does not show the observed outcome data.

The design is described as non-randomized, with no masking and a single-group model. The record itself cautions that the arms are not a like-for-like control comparison. It does not explain how participants entered the procedure groups or describe adjustment for differences between groups. These omissions limit assessment of whether comparisons can be interpreted as effects attributable to the procedure.

The control group’s description is blank, and its composition, recruitment, and relationship to the surgical groups are not reported in the registry record. The record does not describe simulator assessment details or report how much exposure participants had during simulator sessions. It therefore does not allow a detailed assessment of what contributed to a collision count or how comparable assessments were across participants.

Missing-data procedures and analysis populations are not reported. The record does not show how many participants had outcome data at each time point, whether all participants completed follow-up, or how incomplete observations were handled. The stated enrollment is 19, while the adverse-event summaries list 17 at risk; the reason for that difference is not reported.

The record lists 3 outcome measures but does not describe multiplicity control, a statistical analysis plan, interim analyses, or a sample-size justification for the trial. The planning illustration is explicitly separate from the trial’s own design. These reporting gaps make it difficult to assess prespecification, precision, and the role of analyses beyond the primary endpoint.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Driving After Cervical Spine Surgery — NCT02782923.
• Registry record last updated 2020-04-30; status last verified 2020-04.
• Results first posted 2020-04-30.
• 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.

18. Record Summary

The registry identifies NCT02782923, “Driving After Cervical Spine Surgery,” as a completed, prospective, single-center simulation study sponsored by NYU Langone Health. Enrollment is listed as 19. The study start is recorded as 2016-12, and primary completion as 2018-07-17.

The study concerns cervical spine surgery and uses the STISIM driving simulator. The primary endpoint is change in total collisions, including on-road and off-road collisions, from baseline to 3 months. The stated summary is a median with a full range.

Allocation is non-randomized, masking is none, and the model is single group. The registry cautions that the listed arms are not a like-for-like control comparison. It lists 3 outcome measures and 0 analyses, and does not report numerical primary-outcome results. The safety summary records 0 serious adverse events, 0 other adverse events, and 0 deaths among the listed group at risk.