The Degen Study: Post-market Clinical Follow-up on the PASS LP, PASS Degen and PASS Tulip Systems (PASS DEGEN): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Degen Study: Post-market Clinical Follow-up on the PASS LP, PASS Degen and PASS Tulip Systems (PASS DEGEN) (NCT04670536), a registered phase not stated study. The primary outcome is Number of Participant Who Achieved Their Fusion at 24 Months.

2. Clinical Question

The Degen Study concerns people with spinal degenerative disease who underwent surgery using one of three implant systems: PASS LP, PASS DEGEN, or PASS Tulip PRIME. The registry lists thoracolumbar disc degeneration, thoracolumbar spondylolisthesis, spinal deformity, and spinal degeneration among the conditions. It does not report a fuller eligibility definition, so those condition labels should not be treated as a complete description of who could participate.

The primary question is whether participants had achieved fusion at the 24-month postoperative visit, assessed by the investigator using standard-of-care imaging and clinical examination. The registry record names this endpoint but does not report the number of participants who achieved fusion or a comparison of fusion outcomes between the device groups. It also lists pain, quality of life, satisfaction, and fusion status at other visits as secondary outcome areas.

The study is post-market clinical follow-up, not a randomized comparison. The registry does not state how participants were allocated among the device groups, and it explicitly cautions that the arms are not a like-for-like control comparison. Accordingly, differences between groups cannot by themselves establish that one system caused a different outcome.

3. Trial Design

The Degen Study is a post-market clinical follow-up study sponsored by Medicrea International. Its stated purpose is to evaluate the long-term safety and efficacy of the PASS LP, PASS DEGEN, and PASS Tulip PRIME systems for degenerative disease and to support a clinical evaluation report. The registry describes an expected focus extending from intra- and peri-operative experience to medium-term postoperative follow-up. The study is marked completed.

The registry lists enrollment of 77 participants. It gives a study start date of 2018-05-17 and a primary completion date of 2024-05-22. These dates describe the registered study timeline; they do not supply a separate date for final completion. The registry describes three device groups: participants with spinal degenerative disease operated on with PASS LP, PASS DEGEN, or PASS Tulip PRIME.

This is not a randomized comparison, and group allocation is not stated. The registry cautions that the arms are not a like-for-like control comparison. Consequently, the groups should be read as device cohorts in a post-market follow-up study, not as treatment groups created to support a controlled causal comparison. Baseline comparability, adjustment for differences between groups, and the process used to assign devices are not reported in the registry record.

The primary endpoint is fusion status at the 24-month postoperative visit. Secondary outcomes include change in pain measured by VAS; quality of life measured by ODI and SF-12; surgeon satisfaction with the implants and instruments; fusion status at the 1/6 Month and 12-month visits; and patient satisfaction at available postoperative timepoints. The registry lists 7 outcome measures, but does not report numerical results for these secondary outcomes or describe the timing and completeness of all follow-up assessments.

The registry record does not report a detailed protocol, analysis plan, or participant flow. In particular, the reasons for group allocation, the analysis populations, and the handling of incomplete follow-up are not described.

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: Only subjects implanted with one of 3 products listed in the protocol can included and considered as participant. Knowing that 1 investigational site corresponds to only one type of products used.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Difference between number of participants is due to some missing 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.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participant Who Achieved Their Fusion at 24 Months, measured over At 24months.

The primary endpoint is the number of participants who achieved fusion at the 24-month postoperative visit. Fusion is a clinically relevant structural outcome after spinal surgery: it records whether the intended fusion status was achieved at the specified follow-up point. The registry says the investigator assesses fusion using standard-of-care imaging, including CT-scan, X-rays, and/or MRI, together with clinical examination.

This endpoint is expressed as a participant count, rather than as a continuous measurement. The count is meaningful only alongside the number of participants assessed and the definition used to classify fusion. The registry record does not report the achieved-fusion count, the number assessed at the visit, or more detailed classification criteria. It notes that a difference between participant numbers is due to some missing data, but does not give the amount of missingness or explain how it was handled.

The timing matters to interpretation: the endpoint concerns the 24-month postoperative visit, not an immediate operative result or a result at every follow-up timepoint. The listed secondary outcome of fusion status at the 1/6 Month and 12-month Visit concerns other follow-up assessments; numerical results for those assessments are not reported in the registry record.

A count alone does not establish that one device performs differently from another. Such an interpretation would require appropriate group definitions, denominators, and an analysis that addresses relevant differences between cohorts. The registry does not report those comparative results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation depends on the outcome type, the amount of observed data, and the design that generated the observations. The primary outcome in this study is a participant count for fusion achievement at a specified postoperative visit. Counts are descriptive until they are related to the number assessed and analyzed with an appropriate method. The registry record does not report a fusion count, denominator, estimate, confidence interval, or test result, so no inferential conclusion about the primary endpoint can be drawn from the posted results.

What does a count describe?

A count states how many participants met a defined outcome. To interpret it, readers ordinarily need the number eligible for assessment, the number actually assessed, and a clear outcome definition. These details help distinguish the frequency of an outcome among those observed from the number originally enrolled. For this study, the registry identifies the 24-month fusion endpoint and describes the investigator’s imaging and clinical assessment, but does not report the outcome count or denominator. It notes some missing data and does not describe how missing outcomes were treated.

Counts may be presented separately for different groups, but group counts alone do not isolate a device effect. The groups may differ in ways related to both device selection and outcome. In a randomized study, random allocation is intended to balance such factors on average; that design is not described. The registry explicitly says this is not a randomized comparison, says allocation is not stated, and cautions that the arms are not a like-for-like control comparison. Statistical adjustment can sometimes address measured differences, but an adjustment plan or adjusted comparison is not reported.

What would an estimate and confidence interval add?

In general, an estimate describes the size and direction of an observed association or difference. A confidence interval describes the uncertainty around that estimate under the model and assumptions used. A narrower interval indicates greater precision under those assumptions; a wider interval indicates less precision. Neither an estimate nor its interval resolves design limitations such as non-random allocation, missing outcomes, or unmeasured differences between groups. No confidence interval for the primary outcome or a group comparison is reported in the registry record.

A p-value, when reported, measures how compatible the observed data are with a specified statistical model and null hypothesis. It does not measure the probability that a treatment works, nor does it establish clinical importance. Its interpretation relies on the analysis being appropriate and on its assumptions. The registry record reports no p-value or inferential analysis for the primary endpoint. It also does not report an analysis plan defining a null hypothesis or a primary group comparison.

Why does allocation matter?

Comparing outcomes from device cohorts is not equivalent to comparing outcomes from randomly assigned groups. In a post-market setting, device choice may be related to patient, surgeon, or clinical factors. This is a general source of confounding: an observed group difference may reflect those factors, the device, or both. The registry does not describe how devices were selected or whether an analysis attempted to account for differences. Therefore, comparisons among the listed groups should remain descriptive rather than causal.

Multiple outcome measures also raise a general multiplicity issue. When many outcomes or comparisons are examined, the chance of at least one apparently unusual result can increase if no plan addresses the number of tests. A prespecified analysis strategy can clarify which result is primary and how secondary results are interpreted. The registry lists the primary endpoint and secondary outcome areas, but does not report a multiplicity strategy or a full statistical analysis plan.

How should planning illustrations be read?

General sample-size planning asks how many participants would be needed to detect an effect under specified assumptions. The planning illustration associated with this study is described as using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. These are planning assumptions, not evidence that the trial used that allocation or analysis. The record describes three device groups and does not state an allocation method. Sample-size illustrations are not observed power and do not show what the study found. A sample-size justification for the study itself is not reported in the registry record.

For binary outcomes, such as whether fusion was achieved, the underlying data can be represented as participants with an event and participants without it. The interpretation still depends on clearly defined denominators and complete outcome ascertainment. The registry’s primary endpoint is a count, but the posted result does not include the data needed to derive an estimate or precision measure. Statistical methods can describe uncertainty in reported data; they cannot replace outcomes that are not reported.

Finally, the registry reports 0 analyses. This means inferential analysis results are not available in the record; it does not mean that no analyses were performed outside the registry. Whether analyses were conducted elsewhere is not reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("PASS DEGEN", "PASS LP", "PASS Tulip")
n      <- c(18, 25, 14)
events <- c(16, 24, 14)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  PASS DEGEN  18  16  88.9  65.3  98.6  67.2  96.9  66.9  96.6
ARM  PASS LP  25  24  96.0  79.6  99.9  80.5  99.3  80.4  99.1
ARM  PASS Tulip  14  14  100.0  76.8  100.0  78.5  100.0  78.2  99.8

11. Multiplicity, Missing Data and Analysis Populations

The registry names one primary endpoint, fusion status at the 24-month postoperative visit, and several secondary outcome areas: pain measured by VAS, quality of life measured by ODI and SF-12, surgeon satisfaction, fusion at other listed visits, and patient satisfaction at available postoperative timepoints. It lists 7 outcome measures. The registry record does not report a statistical analysis plan specifying how multiple outcomes or multiple group comparisons were handled. In general, examining many outcomes can increase the chance of apparently notable results arising by chance; a prespecified strategy helps readers distinguish the main confirmatory question from exploratory findings.

Missing data are directly relevant to the primary endpoint. The record states that a difference between participant numbers is due to some missing data, but does not state how many observations are missing, which groups or visits they concern, why data are missing, or whether missingness was handled through imputation, exclusion, or another method. The primary fusion count and the number assessed are not reported. Without those details, outcome completeness and the potential influence of missing data cannot be assessed.

The registry does not describe analysis populations, such as whether all enrolled participants or only those with an available 24-month assessment were included in an analysis. It also does not report interim analyses, stopping rules, or a missing-data sensitivity analysis. These details are not reported in the registry record. The absence of these details does not establish that such procedures were not used; it limits what can be evaluated from the posted record.

12. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: adjacent segment degeneration (8.7%), spinal osteoarthritis (6.9%), postoperative wound infections (4.3%), cerebrovascular accident (4.3%), intestinal ischemia (4.0%).

The registry lists participants at risk, participants affected by serious events, participants affected by other events, and deaths for each device group. PASS DEGEN has 23 at risk, 4 affected by serious events, 5 affected by other events, and 0 deaths. PASS LP has 29 at risk, 5 affected by serious events, 0 affected by other events, and 1 death. PASS Tulip has 25 at risk, 7 affected by serious events, 0 affected by other events, and 0 deaths. These are the posted counts; they should not be converted into comparative conclusions without an appropriate analysis and fuller information about ascertainment and follow-up.

The serious-event terms with the largest listed percentages are Adjacent Segment Degeneration (8.7%), Spinal Osteoarthritis (6.9%), Postoperative Wound infections (4.3%), Cerebrovascular accident (4.3%), Intestinal Ischemia (4.0%), and Intervertebral discitis (4.0%). The registry record does not explain the denominator for each listed percentage or how event terms relate to individual participants. A participant may potentially be represented in more than one event category, but that detail is not reported in the registry record.

These figures describe recorded safety events; they do not establish that a device caused an event. The study is not a randomized comparison, allocation is not stated, and the arms are not a like-for-like control comparison. Event definitions, severity grading beyond the serious/other categories, and comparative safety analyses are not reported in the registry record.

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

The registry record establishes that The Degen Study was a completed post-market clinical follow-up study of PASS LP, PASS DEGEN, and PASS Tulip PRIME, with registered enrollment of 77 participants. It identifies fusion at the 24-month postoperative visit as the primary endpoint and describes investigator assessment using standard-of-care imaging and clinical examination. It also identifies secondary outcome areas and posts descriptive adverse-event counts for the device groups.

Those details do not provide the numerical result for the primary fusion endpoint. The number of participants achieving fusion, the number assessed, and any estimated group differences or precision intervals are not reported in the registry record. As a result, the record does not support a quantitative statement about the primary outcome or its uncertainty. A result not reported is not the same as a result showing no difference.

The adverse-event counts and listed event-term percentages provide a description of what is recorded in the registry, but do not establish whether event frequency differs between devices or whether a device caused an event. The study is not a randomized comparison; allocation is not stated, and the registry cautions that the arms are not a like-for-like control comparison. Differences between the groups may therefore reflect factors other than the devices, and no adjusted analysis is reported.

The study’s stated post-market purpose is relevant to describing clinical follow-up and safety experience. However, the registry entry alone does not provide the analysis detail, outcome completeness, or comparative results needed to determine the size or precision of a device-associated effect. The listed secondary outcome domains likewise do not amount to evidence of a specific outcome unless their numerical results are reported.

The most defensible reading is descriptive: the record documents the study design context, endpoint definitions, and some safety counts, while leaving the primary endpoint result and inferential interpretation unavailable. It should not be used to claim that a system is superior, equivalent, or ineffective.

14. Why This Trial Matters Statistically

Post-market follow-up studies address outcomes after medical devices are in use in clinical practice. Their statistical interpretation depends on more than the number enrolled: readers need clear outcome definitions, denominators at each assessment, follow-up completeness, and a design or analysis that supports the intended comparison. The Degen Study makes the 24-month fusion endpoint explicit and identifies the investigator’s imaging and clinical assessment, which clarifies what the primary outcome was intended to measure.

The registry also illustrates why a named endpoint is not the same as a reported result. Although the primary question is identifiable, the fusion count, denominator, uncertainty estimate, and inferential comparison are not reported. Without these, readers cannot assess the magnitude or precision of the primary outcome from the registry record. The note that participant numbers differ because of some missing data makes completeness especially important, but the amount and handling of missingness are not described.

Three device groups can invite side-by-side reading, but the registry explicitly cautions that the arms are not a like-for-like control comparison and does not state allocation. This matters because a numerical difference between observational cohorts is not automatically attributable to the device. Statistical methods can account for some measured factors when properly planned and reported, but the registry does not describe such an analysis.

The listed safety counts are also useful to distinguish descriptive surveillance from comparative evidence. Counts identify recorded events in each group, but denominators, follow-up, event definitions, and potential overlap between event terms all affect interpretation. The registry’s limited reporting leaves those aspects uncertain.

For biostatisticians and clinical researchers, the record therefore highlights a reporting principle: endpoint definitions and study context are essential, but interpretable conclusions also require the observed outcome data and transparent methods. The absence of those details is itself important when judging how much the registry can establish.

15. 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 record does not report the numerical result for the primary endpoint, the number of participants assessed at 24 months, or a confidence interval or test result. It therefore does not permit an assessment of the observed fusion outcome or its precision. Although the record notes some missing data, the amount, timing, reasons, and treatment of missingness are not described.

The study is not a randomized comparison, and the registry does not state how participants were allocated among PASS LP, PASS DEGEN, and PASS Tulip PRIME. It explicitly cautions that the arms are not a like-for-like control comparison. Baseline characteristics, methods for controlling confounding, and adjusted comparative results are not reported in the registry record. Thus, the listed group counts cannot establish a causal device effect.

The record lists secondary outcomes but does not report their numerical results or explain how multiple outcomes and comparisons were handled. It does not report the detailed statistical analysis plan, analysis populations, interim analyses, or sensitivity analyses. The outcome descriptions identify broad measures, but fuller operational definitions and assessment procedures are not reported in the registry record.

Safety reporting is limited to counts and selected event-term percentages. Detailed definitions, event-level follow-up, denominators for the listed percentages, and comparative safety analyses are not reported. The registry record also does not report a sample-size justification for the study itself. These limitations concern what can be interpreted from the registry entry; they do not establish what analyses or procedures may have been conducted elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The Degen Study: Post-market Clinical Follow-up on the PASS LP, PASS Degen and PASS Tulip Systems (PASS DEGEN) — NCT04670536.
• Registry record last updated 2026-05-01; status last verified 2026-04.
• Results first posted 2026-05-01.
• 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.

19. Record Summary

The Degen Study is a completed post-market clinical follow-up study sponsored by Medicrea International, with registered enrollment of 77 participants. The registry lists a start date of 2018-05-17 and a primary completion date of 2024-05-22. It concerns PASS LP, PASS DEGEN, and PASS Tulip PRIME for spinal degenerative disease.

The primary endpoint is the number of participants achieving fusion at the 24-month postoperative visit, assessed by investigator review of standard-of-care imaging and clinical examination. Secondary outcome areas include pain, quality of life, satisfaction, and fusion at other visits. The primary numerical result and inferential analyses are not reported in the registry record.

Descriptive safety counts are posted for each device group. The record states that participant-number differences are due to some missing data, but does not report the amount or handling of missingness. It cautions that the study is not a randomized comparison, allocation is not stated, and the arms are not a like-for-like control comparison.