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 Understanding Non-Response in Spine Fusion Surgery (NCT02611479), a registered phase not stated study. The primary outcome is Oswestry Disability Index.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02611479 |
| Phase | Phase not stated |
| Condition | Spine Fusion |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 184 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Washington |
| Results posted | Yes |
2. Clinical Question
Population
People undergoing spine fusion surgery for degenerative disc disease. The registry lists an enrollment of 184; the primary outcome description says 149 participants were in the baseline population and 140 were analyzed.
Intervention
Spine fusion surgery. The registry describes the study as seeking patient characteristics associated with non-response after surgery; it does not report a treatment assignment protocol.
Comparator
No like-for-like control comparison is described. The registry does not state an allocation method, and the listed comparison is not a randomized comparison.
Primary question
How does pain and function, measured with the Oswestry Disability Index, change from baseline through 60 day and 1 year assessments, and which patient characteristics are associated with non-response?
The clinical aim was to identify patient characteristics associated with non-response following spine fusion for degenerative disc disease. The registry’s primary outcome is change in pain and function, assessed using the Oswestry Disability Index (ODI). The measure is listed at baseline, 60 day, and 1 year. Its scores range from 0 to 100, with higher scores indicating worse outcomes and lower scores indicating better outcomes.
The registered outcome measure does not itself define which patients count as non-responders or state how that classification would be made. A threshold, rule, or other operational definition of non-response is not reported in the registry record. The record also does not identify the patient characteristics to be tested or state how their association with outcome would be assessed. Consequently, the stated aim can be described, but the precise statistical question linking patient characteristics to non-response cannot be reconstructed from the registry entry.
3. Trial Design
The study is titled Understanding Non-Response in Spine Fusion Surgery and is sponsored by the University of Washington. The registry lists the condition as spine fusion and describes the clinical context as surgery for degenerative disc disease. Its brief summary states that the purpose was to identify patient characteristics associated with non-response after surgery. The listed status is completed.
The registry lists an enrollment of 184. The primary outcome description reports a baseline participant population of 149 and says that 140 participants were analyzed for the ODI because 9 participants were excluded due to incomplete ODI data. These figures describe different populations in the record; the reason for the difference between the listed enrollment and baseline population is not reported in the registry record.
The registered outcome is continuous and reported as a mean with standard deviation. Its timeframe is baseline, 60 day, and 1 year. The record does not describe a randomized comparison, and allocation is not stated. The registry’s note says that the arms are not a like-for-like control comparison. This means that a randomized treatment-versus-control interpretation is not supported by the record. Details about any groups, how participants entered them, or how comparisons between groups were planned are not reported in the registry record.
The recorded study dates are 2015-04 for start and 2017-08 for primary completion. The registry lists one outcome measure and no analyses. A protocol-level statistical analysis plan, sample-size justification, interim analysis plan, and detailed recruitment or follow-up procedures are not reported in the registry record. The posted information therefore establishes the study’s stated objective, outcome measure, timing, and recorded participant counts, but not the full design or analysis approach.
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.
Before assignment: If participants did not complete a baseline survey before their lumbar spine fusion surgery or were found to be ineligible they were excluded from the study before completing follow-up surveys.
Baseline Enrollment
| Stage | Spine Fusion Participants |
|---|---|
| STARTED | 184 |
| COMPLETED | 171 |
| NOT COMPLETED | 13 |
Reasons for not completing this period:
| Reason | Spine Fusion Participants |
|---|---|
| Exited study | 13 |
Post-Surgery Follow-up at 30-90 Days
| Stage | Spine Fusion Participants |
|---|---|
| STARTED | 171 |
| COMPLETED | 169 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | Spine Fusion Participants |
|---|---|
| No surgery reported | 2 |
Post-Surgery Follow-up at 1-Year
| Stage | Spine Fusion Participants |
|---|---|
| STARTED | 169 |
| COMPLETED | 151 |
| NOT COMPLETED | 18 |
Reasons for not completing this period:
| Reason | Spine Fusion Participants |
|---|---|
| Lost to Follow-up | 18 |
Data Cleaning
| Stage | Spine Fusion Participants |
|---|---|
| STARTED | 151 |
| COMPLETED | 149 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | Spine Fusion Participants |
|---|---|
| No baseline function or pain metrics | 2 |
Analysis population for the primary outcome, as defined in the registry: 140 participants out of the 149 baseline participant population were analyzed since 9 participants were excluded due to incomplete Oswestry Disability Index data.
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 | Spine Fusion Participants |
|---|---|---|
| Participants analysed | 149 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 71 |
| Age, Categorical: >=65 years | Participants | 78 |
| Sex: Female, Male: Female | Participants | 83 |
| Sex: Female, Male: Male | Participants | 65 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 5 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 144 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 2 |
| Race (NIH/OMB): Asian | Participants | 5 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 140 |
| Race (NIH/OMB): More than one race | Participants | 2 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | participants | 149 |
| Functional Limitations from back pain (ODI) | units on a scale | 41.3 (SD 15.4) |
| Anxiety | T-scores | 55.0 (SD 9.2) |
| Depression | T-scores | 52.5 (SD 9.6) |
| Sleep | T-scores | 55.4 (SD 7.4) |
| Pain chronicity: 1-3 months | Participants | 1 |
| Pain chronicity: 3-6 months | Participants | 4 |
| Pain chronicity: 6 months-1 year | Participants | 19 |
| Pain chronicity: 1-5 years | Participants | 39 |
| Pain chronicity: More than 5 years | Participants | 51 |
| Pain chronicity: Missing | Participants | 35 |
| Pain interference | T-scores | 67.1 (SD 5.5) |
| Pain catastrophizing (fear avoidance): Not at all | Participants | 30 |
| Pain catastrophizing (fear avoidance): To a slight degree | Participants | 38 |
| Pain catastrophizing (fear avoidance): To a moderate degree | Participants | 38 |
| Pain catastrophizing (fear avoidance): To a great degree | Participants | 28 |
| Pain catastrophizing (fear avoidance): All the time | Participants | 11 |
| Alcohol, Marijuana Use: Alcohol | Participants | 42 |
| Alcohol, Marijuana Use: Cannabis Use: Score Recoded | Participants | 27 |
| Alcohol, Marijuana Use: Missing | Participants | 80 |
| Asthma: No | Participants | 106 |
| Asthma: Yes | Participants | 37 |
| Asthma: Missing | Participants | 6 |
6. Primary Endpoint
The registry lists the primary outcome as Oswestry Disability Index, measured over Baseline, 60 day, 1 year.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | score on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the Oswestry Disability Index, a questionnaire-based measure of pain-related disability and function. The registry describes 10 questions covering pain intensity and activities including personal care, lifting, walking, sitting, standing, sleeping, sex, social life, and travelling. Each question has 6 response options describing levels of disability. The item scores run from 0 to 5, where 0 indicates the least disability and 5 the most severe disability.
The combined score ranges from 0 to 100. Higher scores indicate worse outcomes, while lower scores indicate better outcomes. The registry describes the outcome as change in pain and function after surgery, with assessments at baseline, 60 day, and 1 year. It lists the summary measure as a mean and the accompanying variability measure as a standard deviation.
As a general measurement principle, a questionnaire such as the ODI offers a structured way to summarize a person’s reported limitations across several daily activities. Repeated measurements can describe how scores change over time. However, the registry record does not report the observed ODI means, standard deviations, changes, or a threshold defining a clinically meaningful change. It also does not give a rule for classifying non-response. The listed measure and its timing therefore explain what was intended to be assessed, but do not establish the magnitude or precision of any observed change.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies a clear descriptive objective: to study patient characteristics associated with non-response after spine fusion surgery for degenerative disc disease. It also identifies the ODI as the primary outcome measure and gives its assessment times. However, the posted information does not include numerical ODI results, estimates of change, standard deviations, confidence intervals, or association estimates. The registry lists no analyses. Therefore, the statistical findings for the stated objective cannot be interpreted from the registry record.
The participant figures need to be read in their stated contexts. The registry lists enrollment of 184, while the outcome description refers to 149 participants in the baseline population and says 140 were analyzed because 9 were excluded for incomplete ODI data. The record does not explain the difference between enrollment and the baseline population. Nor does it describe whether the analyzed participants differed from those not included in that analysis. Without such information, the potential effect of the exclusions on the reported outcome cannot be assessed.
The outcome is recorded at baseline, 60 day, and 1 year. These timepoints indicate an intended longitudinal description, but the registry does not provide values at any of them or explain how measurements across time were analyzed. A mean and standard deviation are named as the summary format; those labels alone do not reveal the size, direction, or precision of a change. The record also does not define non-response, so it is not possible to determine how the stated aim would be translated into an outcome category or analytic contrast.
The registry does not describe a randomized comparison and states that the arms are not a like-for-like control comparison. Accordingly, the entry does not support attributing any change to a contrast between randomized treatments. It also does not state allocation, group definitions, or adjustment for patient characteristics. The study’s stated purpose is to identify associations, but specific associations and their estimates are not reported in the registry record.
The adverse-event entry lists zero participants at risk and zero affected for the recorded serious and other event fields. Because the entry also has no participants at risk recorded, these values do not provide a usable event rate or a basis for comparing safety between groups. The registry record does not provide further adverse-event context.
Overall, the record documents the question, outcome instrument, assessment schedule, and participant counts associated with the outcome description. It does not report the numerical outcome findings or analysis needed to establish what the data showed about change or patient characteristics. Any conclusion about the size, precision, or direction of an effect would go beyond what is reported.
9. Statistical Methods Explained
The registered outcome is continuous, with the mean as its summary measure and standard deviation as its stated measure of dispersion. The record gives the ODI score range and assessment timing, but does not report outcome values or an analysis method. The explanations below describe general statistical concepts; they do not establish which methods were used in this study.
What does a mean describe?
General: A mean summarizes the central level of a numeric measure across the observations included in a calculation. For repeated measurements, means at different timepoints can describe the group’s average score at each assessment. A difference between timepoint means can describe average change, but an analysis of within-person change may use the paired measurements directly. The registry does not report which form of change calculation or comparison was used.
A mean can conceal variation among individuals. People with similar average scores may have different patterns of improvement, worsening, or stable scores. This is especially relevant to a study whose aim concerns non-response: the average score alone does not identify which individuals were considered responders or non-responders. The registry record does not report such a classification rule.
What does the standard deviation describe?
General: A standard deviation describes how dispersed individual observations are around their mean. Greater spread indicates that individual scores vary more widely around the group average; smaller spread indicates that scores are more clustered. It is not the same as the uncertainty in the estimated mean. The uncertainty of an estimate is commonly conveyed with a confidence interval, but no confidence interval is reported for the registered outcome.
For the ODI, variation may reflect differences in reported disability across participants. A group mean and standard deviation would describe the distribution in a compact way, but they would not show the full distribution or establish why participants differ. The registry labels these summary statistics but does not provide their numerical values.
How should repeated assessments be understood?
General: Measurements from the same participant over time are related, rather than independent observations. Analyses that account for this relationship can distinguish within-person change from differences between participants. The choice of approach depends on the design, missingness, and the specific question. The registry lists baseline, 60 day, and 1 year as outcome timepoints, but does not report whether measurements were analyzed with a repeated-measures model, change scores, separate timepoint summaries, or another method.
The timing also matters when interpreting change. A score at a later assessment is meaningful in relation to the baseline score and to the definition of the target outcome. Without the observed values and analysis details, the time course of ODI scores cannot be described from the registry record.
What can an association analysis establish?
General: An association analysis asks whether an observed characteristic varies with an outcome. Its interpretation depends on how characteristics and outcomes are defined, which participants are included, and whether relevant factors are accounted for. An association does not by itself establish that a characteristic caused an outcome. The record states an aim to identify characteristics associated with non-response, but does not list the characteristics, define non-response, or report association estimates or adjustment methods.
The registry does not describe a randomized comparison, and allocation is not stated. The entry also notes that arms are not a like-for-like control comparison. This limits any interpretation based on treatment-group contrasts: the record does not establish that groups were formed in a way that makes them comparable. It does not report the comparison structure or specify how differences among participants were handled.
What does a planning calculation mean?
General: A sample-size planning illustration estimates the number of participants that might be needed under stated assumptions to detect a target effect with a chosen statistical framework. It is not a measure of what the study observed, nor is it observed power. The planning assumptions associated with the posted illustrations are a two-sided significance level of 0.05, equal allocation between two hypothetical arms, and a normal approximation; the target effect is defined as a stated fraction of the observed effect. For time-to-event illustrations, the stated quantity is a total number of events, while other illustrations are expressed as participants per arm. These are planning conventions, not evidence that the study used that design or met those targets. No sample-size justification for the trial is reported in the registry record.
The registry does not state an inferential model, hypothesis-testing procedure, confidence-interval method, covariate adjustment, handling of repeated measurements, or approach to multiplicity. Since the record lists no analyses and provides no numerical outcome findings, no recalculated estimate or precision assessment can be derived from the stated information. Any statistical interpretation should remain at the level of the registered measurement and its documented participant counts.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure, the ODI, assessed at baseline, 60 day, and 1 year. Multiple assessment times can raise questions about which timepoint or contrast is primary for inference, and about how repeated testing is handled. The record does not state a multiplicity strategy or identify a specific timepoint as the sole inferential comparison. It also does not report whether the timepoints were analyzed jointly or separately.
The outcome description states that 9 participants were excluded from the analysis because of incomplete ODI data. It reports 149 participants in the baseline participant population and 140 analyzed. The record does not explain how incomplete data arose, whether missingness occurred at particular timepoints, or whether included and excluded participants differed. It does not describe imputation, a complete-case rationale, sensitivity analyses, or another missing-data method. The reason for the difference between the listed enrollment of 184 and the stated baseline population of 149 is not reported in the registry record.
These details matter because missing outcome data can affect both the composition of the analyzed population and the interpretation of change over time. As a general principle, the consequences depend on the pattern and reasons for missingness and on the analysis used. In this record, those features are not described, so the direction or extent of any potential bias cannot be assessed.
The registry lists no analyses. It does not report an analysis population definition beyond the ODI participant counts, a protocol for covariate adjustment, or a plan for handling multiple comparisons. These omissions prevent assessment of whether the analysis followed a prespecified plan or how robust its conclusions would be to alternative assumptions.
11. What the Result Does, and Does Not, Mean
The registry record establishes that the study aimed to identify patient characteristics associated with non-response after spine fusion surgery for degenerative disc disease. It identifies the ODI as the primary measure, describes its scoring direction and content, and gives baseline, 60 day, and 1 year as assessment times. It also reports enrollment of 184 and, in the outcome description, a baseline population of 149 with 140 analyzed after 9 participants were excluded for incomplete ODI data.
Those details do not show whether ODI scores improved, worsened, or remained stable. Numerical means, standard deviations, changes, and confidence intervals are not reported in the registry record. No analyses are listed, and no estimates relating patient characteristics to non-response are reported. The record also does not define non-response. Therefore, it cannot establish which participants met that outcome or which characteristics were associated with it.
The registry does not describe a randomized comparison, and allocation is not stated. It notes that arms are not a like-for-like control comparison. The record therefore cannot support a randomized treatment-effect interpretation. More broadly, an association between a patient characteristic and an outcome would not, by itself, establish causation; the study’s specific analysis and adjustment approach are not reported.
The adverse-event fields list zero participants at risk and zero affected for the recorded event categories. Those entries do not establish the absence of adverse events in a population with a documented risk denominator, because the record does not give participants at risk for those fields. No comparative safety conclusion can be drawn from the entry.
In short, the registry supports a description of the study’s aim, measure, timing, and stated participant counts. It does not provide the numerical findings needed to judge the observed outcome or the precision of any estimate. Conclusions beyond those documented elements are not reported in the registry record.
12. Why This Trial Matters Statistically
This study is statistically notable for the difference between its stated research aim and the information available in the registry entry. The aim concerns characteristics associated with non-response, which requires a clear definition of non-response and an analysis connecting participant characteristics with that outcome. Neither the definition nor the analysis results are reported. This prevents readers from assessing the central association question from the registry record.
The outcome is measured repeatedly using a patient-reported scale, with assessments at baseline, 60 day, and 1 year. Repeated measurements can describe both average levels and change over time, but the analysis needs to account for the relationship between observations from the same participant. The record gives the measure and schedule without describing that analysis. It also gives a participant count for the ODI analysis and documents exclusions for incomplete data, making the handling and pattern of missing measurements important to interpretation.
The entry’s note that the arms are not a like-for-like control comparison is also statistically consequential. A reader should not interpret the study as a randomized comparison based on this record. The absence of allocation details and numerical results further limits what can be inferred about group contrasts or patient-level associations.
Finally, a registered outcome measure is not a reported result. Naming the ODI and its summary format does not show the observed score distribution, the size of any change, or how precise an estimate may be. Distinguishing the study’s objective and planned measurements from its reported findings is essential for a calibrated reading of the evidence. In this case, the registry documents the measurement framework, but the statistical results needed to answer the study’s stated question are not reported in the registry record.
13. 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.
A central limitation of the available record is that it does not report numerical results for the primary outcome. Although the ODI, its summary format, and its assessment times are identified, means, standard deviations, changes, and uncertainty estimates are absent. The registry also lists no analyses. Consequently, the magnitude and precision of any observed outcome cannot be evaluated.
The study’s stated aim refers to non-response, but the registry does not define that outcome. It does not report a cutoff, classification procedure, or analysis linking such a classification to patient characteristics. The characteristics of interest and their association estimates are also not reported in the registry record. This makes the central question difficult to assess even apart from the missing numerical ODI results.
The participant counts require caution. Enrollment is listed as 184, while the outcome description gives a baseline population of 149 and an analyzed population of 140 after excluding 9 participants for incomplete ODI data. The difference between enrollment and baseline population is not explained. Details about the timing and pattern of missing data, and the handling of incomplete observations beyond the stated exclusions, are not reported.
The registry does not describe a randomized comparison, states that allocation is not stated, and notes that arms are not a like-for-like control comparison. Group definitions and comparison procedures are not reported. Thus, the record does not support a controlled treatment-effect interpretation. It also does not report adjustment methods or a detailed statistical plan for assessing patient characteristics.
Finally, the adverse-event fields list zero at risk and zero affected. With no participants at risk recorded in those fields, they cannot establish an event rate or support a comparative safety assessment. These limitations concern what the registry reports; they do not establish what may have been analyzed or documented elsewhere.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Understanding Non-Response in Spine Fusion Surgery — NCT02611479.
- Registry record last updated 2019-05-30; status last verified 2019-05.
- Results first posted 2019-05-30.
- 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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17. Record Summary
The completed study Understanding Non-Response in Spine Fusion Surgery, sponsored by the University of Washington, aimed to identify patient characteristics associated with non-response after spine fusion surgery for degenerative disc disease. The registry lists enrollment of 184 and records the study start as 2015-04 and primary completion as 2017-08.
The primary outcome is the ODI, a continuous score summarized as a mean with standard deviation and assessed at baseline, 60 day, and 1 year. The outcome description reports a baseline participant population of 149 and an analysis population of 140, with 9 participants excluded for incomplete ODI data. Numerical outcome results and analyses are not reported in the registry record. Non-response is not defined there, and the record does not describe a randomized comparison or state an allocation method. The posted information documents the objective and measurement plan, but does not provide the findings needed to assess the stated association question.