Percutaneous Diskectomy SpineJet x Open Microdiskectomy in Treatment of Lumbar Radiculopathy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Percutaneous Diskectomy SpineJet x Open Microdiskectomy in Treatment of Lumbar Radiculopathy (NCT01367860), a randomized na study. The primary outcome is VAS for Lumbar Pain in 3 Months.

2. Clinical Question

The registry record describes a randomized clinical trial and identifies the primary analysis population as intention to treat. The clinical question is therefore about the comparative mean pain scores among participants assigned to the procedures, rather than only among participants who completed treatment as planned. That distinction matters because an intention-to-treat analysis generally keeps participants in their randomized groups, although the handling of missing measurements is not reported in the registry record.

The trial enrolled 40 participants, with 20 in each group in the posted primary outcome summaries. At three months, the mean score was 2.63 in the open microdiscectomy group and 4.53 in the SpineJet group. Since a higher score means worse pain, the observed group means were numerically higher in the SpineJet group. The uncertainty around the estimated difference is substantial, so the observed direction and size should be read together with the interval estimates and the sponsor's reported analysis.

3. Trial Design

The registry describes a randomized, parallel-group trial with single masking. It lists open microdiscectomy and Percutaneous Diskectomy SpineJet as the two procedures. The record does not say who was masked, so it is not possible to determine from the registry whether masking applied to participants, outcome assessors, or another group. The trial is marked completed. Enrollment was 40, and the recorded start and primary completion dates are 2011-06 and 2012-04.

The primary endpoint was lumbar pain at three months, assessed using a Visual Analog Scale. The primary analysis population is identified as intention to treat. The posted group summaries show 20 participants in each arm for this outcome. The registry lists 17 outcome measures and 16 analyses, and identifies 15 secondary outcomes as posted. It includes assessments of pain and disability at different time points, although numerical results are not available for every outcome named in the record.

The registry does not report the trial's original sample-size justification, its design assumptions, or whether interim analyses were planned or conducted. The masking details, method of sequence generation, allocation concealment, and handling of deviations from assigned procedures are not reported in the registry record. These omissions limit how fully the design can be evaluated from the record alone.

The study was sponsored by the University of Sao Paulo. The registry identifies the trial phase as NA. The study description frames the comparison as a test of a percutaneous technique against open microdiscectomy among people with radiculopathy and disc herniation. The posted primary outcome focuses on pain at three months; this result does not, by itself, describe later pain, disability, imaging changes, or other outcomes.

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: Exclusion criteria were: neurological changes during conservative treatment, pregnancy, clinical status not adequate for surgical procedures, non-adherence to informed consent form. After inclusion in the study, patients were evaluated for pain and function and then randomly allocated in two groups

Overall Study

Analysis population for the primary outcome, as defined in the registry: intention to treat

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 VAS for Lumbar Pain in 3 Months, measured over VAS for Lumbar Pain at 3 Months.

The primary endpoint is mean lumbar pain at three months, measured using a Visual Analog Scale with values from 0 to 10. The registry states that higher values indicate a worse outcome and zero is better. A mean summarizes the average score in a group, while the standard deviation describes the spread of individual scores around that group mean. Both are useful for comparing groups, but a difference in means does not show how every participant experienced pain.

Pain is a direct patient-reported symptom and is relevant to a trial comparing procedures intended to treat symptoms associated with lumbar radiculopathy. Measuring it at a specified follow-up time makes the comparison interpretable at that time point. The registry identifies the three-month pain score as the primary endpoint, so it is the main result for assessing the trial's stated comparative question. It does not capture all aspects of the condition or procedure, and it should not be treated as a substitute for the disability, safety, or longer-term outcomes also named in the record.

The posted means were 2.63 for open microdiscectomy and 4.53 for SpineJet. The posted standard deviations were 2.9 and 3.47, respectively. These group summaries indicate the scores varied among participants. Because the endpoint is a continuous scale, the analysis compares average scores; interpretation should account for the estimated difference and its uncertainty, not only the direction of the means.

7. Results Posted in the Registry

• SJet: mean 4.53 versus 2.63 on control; difference 1.90 (95% CI -0.08 to 3.88), standardized effect d = 0.59; z-test p = 0.060.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

VAS for Lumbar - 1st Week

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • SJet: mean 4.10 versus 3.71 on control; difference 0.39 (95% CI -1.37 to 2.15), standardized effect d = 0.14; z-test p = 0.665.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between SJet and the control. The interval gives the range of effects that remain compatible with the data.

VAS for Lumbar 1st Month

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • SJet: mean 4.06 versus 3.34 on control; difference 0.72 (95% CI -7.93 to 9.37), standardized effect d = 0.05; z-test p = 0.870.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between SJet and the control. The interval gives the range of effects that remain compatible with the data.

VAS for Lumbar Pain - 3rd Month

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • SJet: mean 4.53 versus 2.63 on control; difference 1.90 (95% CI -0.08 to 3.88), standardized effect d = 0.59; z-test p = 0.060.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between SJet and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary numerical summaries include lumbar pain at the first week, first month, and third month. In those summaries, the SpineJet group has a numerically higher mean pain score than the open microdiscectomy group. Since higher scores indicate worse pain, the direction is consistent with the primary outcome's group means. The third-month secondary result repeats the primary endpoint comparison rather than adding an independent time point.

The recalculated unadjusted comparisons for the first week and first month are uncertain: their intervals include zero, and their recalculated p-values are 0.665 and 0.87. The registry's reported analysis entries for those time points display p < 0.05. The record does not explain this difference between the reported entries and the simple recalculations, so the values should not be treated as interchangeable. Numerical summaries for the other named secondary outcomes are not reported in the registry record.

Secondary outcomes can add context about whether the primary pattern is accompanied by changes in related measures or at other time points. They generally carry less weight than the prespecified primary endpoint when many outcomes or time points are examined, especially if no multiplicity adjustment or hierarchy is reported. Testing many outcomes increases the chance of finding an apparently noteworthy result by chance. The registry lists 15 secondary outcomes as posted, but a multiplicity strategy is not reported in the registry record. The overall secondary evidence is therefore limited and should be interpreted alongside, rather than in place of, the primary result.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Clinical Evaluation
• VAS for Lumbar - 1st Week
• VAS for Lumbar 1st Month
• VAS for Lumbar Pain - 3rd Month
• VAS for Lumbar Pain - 6th Month
• VAS for Lumbar Pain - 12th Month
• Oswestry Disability Index (ODI) - 1st Week
• Oswestry Disability Index (ODI) - 1st Month

9. Statistical Interpretation

10. Statistical Methods Explained

For a continuous outcome such as a pain score, a common summary is the mean in each randomized group. The mean gives the average observed score, while the standard deviation describes how dispersed participant scores are within that group. In the primary results, the mean was 2.63 with standard deviation 2.9 for open microdiscectomy, and 4.53 with standard deviation 3.47 for SpineJet. The comparison uses the difference between the group means, rather than comparing the two means as unrelated descriptions.

What does the mean difference express?

The recalculated contrast is defined as SpineJet minus open microdiscectomy, giving 1.9 units on the pain scale. With the registry's scoring direction, a positive contrast corresponds to a higher average pain score in the SpineJet group. Reversing the order of the groups reverses the sign but not the underlying comparison. This is why the sponsor's reported mean difference of -1.89 can be read in the opposite direction from the recalculation; the sign convention must be considered before interpreting direction.

What does a confidence interval add?

A confidence interval describes uncertainty around an estimated effect under the assumptions of the analysis. It gives a range of values compatible with the observed data and the statistical procedure; it is not a range containing a known fraction of individual participants' scores. The recalculated interval extends from -0.082 to 3.882. Since the interval includes zero, the summaries do not sharply distinguish a positive average difference from no difference or a small difference in the opposite direction. The sponsor's reported 95% interval is -4.05 to 0.26 and also includes zero.

What is the role of the p-value?

A p-value describes how unusual the observed test statistic would be under a specified null hypothesis and model. It is not the probability that the null hypothesis is true, nor is it a measure of clinical importance. The recalculated unadjusted p-value is 0.06. The sponsor reports p = 0.05 for its two-sided t-test. These values are close to a conventional threshold sometimes used in statistical testing, but the registry does not report a decision threshold for the trial's own analysis plan. A borderline value should not be treated as a sharp dividing line between important and unimportant evidence.

Why can a small trial have uncertain estimates?

Estimates from a limited number of participants are often sensitive to variation among individual observations. Standard errors quantify uncertainty in an estimate, and confidence intervals reflect that uncertainty. The posted standard deviations show meaningful variation in pain scores within both groups. With 20 participants per group, the interval remains broad. A non-significant or borderline result in such a setting does not establish equivalence; demonstrating that effects are sufficiently similar requires a design and analysis intended to assess equivalence or non-inferiority, and such a plan is not reported in the registry record.

Why might over-dispersion matter?

General statistical principle: over-dispersion occurs when observed variability is greater than a model assumes. If an analysis understates variability, standard errors may be too small and intervals too narrow. The primary endpoint is continuous, and the record reports standard deviations rather than a count model, so over-dispersion is not identified as an issue in the posted primary analysis. In general, matching the analysis model to the outcome's distribution and variability matters for valid uncertainty estimates.

How does randomization fit the interpretation?

Random allocation is intended to make treatment groups comparable on average at assignment, including characteristics that may not be measured. It supports an interpretation based on assigned groups, provided allocation and analysis are carried out appropriately. The registry identifies the trial as randomized and labels the primary population intention to treat, but sequence generation, concealment, and the handling of missing outcomes are not reported in the registry record. The record therefore supports describing the randomized comparison, while leaving some implementation details unknown.

The recalculation is an unadjusted comparison from the posted group summaries. It does not account for covariates, repeated measurements, or any other model features unless those are reflected in the reported summary statistics. The registry names a two-sided t-test for its reported primary analysis. No fuller statistical analysis plan, adjustment strategy, or interim-analysis information is reported in the registry record. These distinctions matter: an unadjusted recalculation is useful for checking the basic scale and direction of the comparison, but it is not a replacement for the trial's full analysis.

11. Confidence Intervals and Precision

Precision concerns how tightly an estimate is determined by the data. For the three-month primary outcome, the recalculated mean difference is 1.9, with an interval from -0.082 to 3.882. The interval is wide enough to include zero and values on both sides of zero. Thus the posted summaries do not precisely determine the direction or size of the group difference.

The sponsor's reported estimate is -1.89, with a 95% confidence interval from -4.05 to 0.26. This interval also includes zero. The sponsor's contrast uses the reverse sign direction from the recalculated SpineJet-minus-open comparison. Although the point estimates describe similar directions when that sign convention is taken into account, the intervals differ in their width and limits. The registry does not explain the analytical details behind that difference.

A confidence interval is not a guarantee that the true effect lies within its endpoints. General statistical interpretation treats it as a range produced by a method that, over repeated use under its assumptions, has a stated coverage property. The reported interval should be read as a description of uncertainty, not as evidence that all effects inside it are equally plausible or as a prediction interval for individual outcomes.

The small number of participants in each group contributes to uncertainty, while variation in the scores also affects precision. The estimates do not establish that the groups are the same, and they do not establish a precise clinically meaningful advantage for either procedure. The registry does not report a threshold for a clinically important difference, which further limits interpretation of the interval in clinical terms.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm because these calculations concern a continuous outcome and assume equal allocation between the two groups. They are not total event counts. The planning illustration uses a two-sided significance level of 0.05, equal allocation, and a normal approximation. The effect to detect is defined as a stated fraction of the observed effect. The original trial's own sample-size assumptions and justification are not reported in the registry record.

For the primary outcome, planning for 100% of the observed effect gives 45 participants per arm for 80% power and 60 participants per arm for 90% power. Planning for 75% of the observed effect gives 80 participants per arm for 80% power and 106 participants per arm for 90% power. Planning for 50% of the observed effect gives 178 participants per arm for 80% power and 239 participants per arm for 90% power.

In plain language, 80% power describes the chance that a study would detect an effect of the specified size using the stated analysis assumptions if that effect were truly present. The 90% column uses a higher target chance of detection and therefore calls for more participants under the same assumptions. These values are planning illustrations based on the observed effect; they are not observed power.

The pattern across the planning rows is important: smaller effects require more participants to detect with the same target power. Because the observed effect itself is uncertain, these estimates should not be treated as definitive requirements for a future study. They illustrate how the participant count changes with the assumed effect size and power target, rather than documenting how the completed trial was designed.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 1.900; pooled standard deviation σ = 3.198.
2. n = 2 × (1.96 + 0.842)² × 3.198² / 1.900² = 44.5, rounded up to 45 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 1.9                      # observed difference in means
sigma <- 3.1977257543448                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1367860)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 45 (80% power), 60 (90% power)
 75% of observed effect: n per arm = 80 (80% power), 106 (90% power)
 50% of observed effect: n per arm = 178 (80% power), 239 (90% power)
power.t.test: 45.4 
Simulated power at n = 45 per arm: 0.790 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The sponsor's primary analysis is listed as a two-sided t-test comparing final values. It reports a mean difference of -1.89, a 95% confidence interval from -4.05 to 0.26, and p = 0.05. The recalculation from the posted means and standard deviations expresses the contrast as SpineJet minus open microdiscectomy, giving 1.9 with an interval from -0.082 to 3.882 and an unadjusted p-value of 0.06. The sign changes when the group order is reversed.

The two estimates are close in magnitude, but their confidence intervals and p-values are not identical. Both intervals include zero, and the record does not provide enough detail to determine why the interval limits differ. The recalculation is a simple, unadjusted analysis of the posted summary statistics; the sponsor's result is the analysis reported by the trial record. Neither should be silently substituted for the other. The sponsor's test should be interpreted using its stated contrast direction and test description, while the recalculation offers a transparent comparison based on the group summaries.

The registry does not report further details about the sponsor's analysis, such as any adjustment or missing-data procedure. The record also does not explain whether the reported test reflects the full analysis plan. Accordingly, these results support a careful description of uncertainty, not a definitive conclusion based on the p-value alone.

15. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary endpoint and lists multiple secondary outcomes, including pain and disability measures at different follow-up times. It also reports 17 outcome measures, 16 analyses, and 15 secondary outcomes as posted. With several outcomes or time points, the chance of at least one apparently unusual result can rise if each is tested separately. Statistical methods that address multiplicity can control or describe this issue, but the registry record does not report whether an adjustment, outcome hierarchy, or other multiplicity strategy was planned or used.

The record does not report a complete statistical analysis plan, the original sample-size justification, or whether interim analyses occurred. It also does not provide enough detail about missing outcome data, exclusions, protocol deviations, or the handling of participants who did not complete follow-up. Although the primary population is labeled intention to treat, that label alone does not explain how missing measurements were handled or how the analysis retained participants in their randomized groups.

These omissions are relevant to interpretation. Missingness can affect a comparison if the probability of having an observed score is related to group assignment or outcome. An analysis restricted to observed outcomes can differ from an analysis using an imputation or model-based approach, but the registry does not describe which procedures, if any, were used. Similarly, the reported primary test is named as a two-sided t-test, but details about assumptions, adjustments, and analysis populations beyond the intention-to-treat label are not reported in the registry record.

The absence of these details does not establish that the analyses were inappropriate. It means the registry record does not allow readers to evaluate those choices fully. The primary result is best read as the posted comparison with the stated uncertainties, while recognizing that multiplicity and missing-data handling remain unresolved reporting limitations.

16. Safety Results

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

Other (non-serious) adverse events

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

The posted adverse-event figures list 20 participants at risk in each group. For both open microdiscectomy and SpineJet, the record reports zero serious adverse events and zero other adverse events in those groups. The serious adverse event terms list is empty.

These counts describe what was posted for the groups and should not be interpreted as proof that no adverse events occurred outside the reporting categories or follow-up captured in the record. The registry does not report deaths for either group; the death entries are not populated, so they are not equivalent to reported zero deaths. The duration and completeness of adverse-event ascertainment are not reported in the registry record.

With 20 participants per group, the event counts are limited in their ability to characterize uncommon harms. Safety interpretation also depends on how events were defined, collected, and monitored, details that are not reported in the registry record. The posted zero counts are a description of the registry entries, not a comprehensive estimate of comparative safety.

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

The primary result describes mean lumbar pain scores at three months among randomized groups. The open microdiscectomy mean was 2.63 and the SpineJet mean was 4.53 on a scale where higher scores indicate worse pain. The recalculated mean difference is 1.9 in the SpineJet-minus-open direction, but its interval includes zero and the sponsor's reported interval also includes zero. The estimates are therefore uncertain about the size and direction of an average difference.

The result does not establish that the procedures are equivalent. A study that does not demonstrate a clear difference is not automatically a study demonstrating that two treatments have sufficiently similar effects. Equivalence or non-inferiority requires a specific design and decision margin, neither of which is reported in the registry record. The result also does not establish a clinically important difference, because the registry does not report a threshold for clinical importance on this scale.

The primary endpoint is one measure at one follow-up time. It does not, by itself, establish what happened to disability, later pain, imaging changes, or other outcomes named in the record. Nor do the posted zero adverse-event counts establish that either procedure has no risk. The registry's incomplete reporting of missing-data handling, multiplicity, and analysis details also limits how comprehensively the results can be assessed.

The most defensible reading is descriptive: the posted mean pain score was numerically higher in the SpineJet group at three months, but the estimated difference is imprecise. The data do not provide a precise basis for concluding that the underlying groups differ by a particular amount. This statistical interpretation is not medical advice and does not determine which procedure is appropriate for an individual.

18. Why This Trial Matters Statistically

This trial illustrates why a group mean and a p-value are not enough to understand a clinical comparison. The direction of the mean scores can be described, but uncertainty intervals show that a wide range of underlying differences remains compatible with the posted data. In a trial with 20 participants per group, interpreting the point estimate without its interval would overstate how precisely the comparison has been determined.

It also illustrates the importance of specifying contrast direction. The recalculation expresses SpineJet minus open microdiscectomy, while the sponsor reports a negative mean difference consistent with the reverse group order. Stating the group order and the scale's scoring direction prevents a sign from being mistaken for a treatment effect in the opposite direction.

The record also demonstrates the distinction between a trial's reported analysis and a simple recalculation from summary statistics. The recalculation makes the arithmetic comparison transparent, while the sponsor's reported test reflects the result recorded for the trial. Their differences, especially in the reported intervals and p-values, should be visible rather than hidden by selecting only one value. Missing details about the analysis plan, missing outcomes, and multiplicity further show why registry summaries support careful interpretation but may not answer every methodological question.

19. 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 trial enrolled 40 participants, with 20 in each group in the primary outcome summaries. The resulting primary estimate is imprecise, and the confidence intervals include zero. The registry does not report a clinically important threshold for the pain scale, so the meaning of the estimated size cannot be judged against a stated threshold.

The registry identifies single masking but does not state who was masked. It does not report the randomization sequence method or allocation concealment. These omissions prevent a full assessment of how randomization and masking were implemented. The primary population is labeled intention to treat, but missing-data methods, exclusions, and deviations from assigned procedures are not reported in the registry record.

The primary endpoint is pain at three months. Although the record names later pain and disability assessments, numerical summaries are not reported for every listed outcome. The record also does not report a multiplicity strategy, the original sample-size justification, or interim-analysis information. These gaps limit interpretation of secondary findings and prevent assessment of the trial's original planning assumptions.

The registry's description of the target population is not fully aligned in wording: the official title emphasizes contained disc herniation, while the brief description refers to contained or extruded herniation. The record does not give further detail about participant characteristics or eligibility in the results presented. This limits assessment of how broadly the findings apply beyond the enrolled group.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Percutaneous Diskectomy SpineJet x Open Microdiskectomy in Treatment of Lumbar Radiculopathy — NCT01367860.
• Registry record last updated 2014-06-04; status last verified 2014-05.
• Results first posted 2014-06-04.
• 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.

23. Record Summary

The completed randomized, parallel-group trial compared open microdiscectomy with Percutaneous Diskectomy SpineJet for lumbar radiculopathy associated with disc herniation. Enrollment was 40, and the sponsor was the University of Sao Paulo. The primary endpoint was mean lumbar pain at three months on a 0-to-10 Visual Analog Scale, with higher scores indicating worse pain.

Mean scores were 2.63 for open microdiscectomy and 4.53 for SpineJet. The recalculated unadjusted mean difference was 1.9 in the SpineJet-minus-open direction, with an interval from -0.082 to 3.882 and p = 0.06. The sponsor reported a mean difference of -1.89, a 95% confidence interval from -4.05 to 0.26, and p = 0.05. Both intervals include zero. The result is uncertain, and key details on missing data, multiplicity, and the original design assumptions are not reported in the registry record.