Procedures 10 years ago performed included intradiscal nucleoplasty (ACUTHERM) and intradiscal electrothermal therapy (IDET). At follow up MRI scans evaluated by two blinded specialists for disc degeneration were carried out. Intra- and interrater variability were accounted for. Baseline and 10-year post-procedure clinical parameters were compared.

This retrospective observational cohort study was conducted at a single urban spine department. After obtaining IRB approval from the state medical board (Landesärztekammer Stuttgart, Germany, F-2020-177), all consecutive patients from the outpatient clinic between 2010 and 2013 who underwent intradiscal procedures-such as discography, intradiscal electrothermal therapy (IDET) for discogenic pain, or intradiscal nucleoplasty for radicular pain-were contacted and invited to participate in the study. Participants were asked to undergo a current MRI and complete the patient-reported outcome measures (PROMs) listed below. The study was conducted between 2022 and 2024.

Inclusion Criteria Patients eligible for early intradiscal procedures included those with low back pain (NRS > 5) caused by discogenic pain due to disc degeneration or radicular pain due to disc protrusion and subsequent nerve root compression. All patients were required to have been resistant to conservative therapy. Diagnoses were based on patient history, physical examination, imaging studies, and, in some cases, provocative discography if discogenic pain could not otherwise be clearly identified.

Enrollment Criteria To be included in the retrospective study, patients must have undergone one of the specified intradiscal procedures, successfully established contact, voluntarily agreed to participate, and demonstrated sufficient language proficiency to complete study assessments.

Exclusion Criteria

Patients were excluded if they met any of the following conditions:

• Perioperative complications.
• Post-interventional lumbar spine surgery in the region to be examined.
• Contraindications for a repeated MRI.
• Metastases or infection of the spine since surgery.
• Spinal canal stenosis.
• A diagnosis of anxiety disorder, depression, or somatoform disorder since surgery, based on their medical history.

Intradiscal Procedures Patients with specific low back pain in this study were treated with minimally invasive techniques prior to considering open surgeries, such as spinal fusion or sequestrectomy. All procedures were performed between 2010 and 2013 by a single spine surgeon experienced in intradiscal interventions. Patients with discogenic pain due to disc degeneration were treated with intradiscal electrothermal therapy (IDET) or nucleoplasty (ACUTHERM) for radicular pain using the NT2000iX generator (Abbott, USA) protocol as described previously (10).

Primary Outcomes The primary outcome of the study was to assess the degeneration of intervertebral discs using the Pfirrmann classification, comparing pre- and postoperative MRI images of punctured and non-punctured discs. Some preoperative MRI images were available from internal archives, while missing images were obtained directly from patients (on DVD) or requested from external radiology centers. Postoperative MRI images were performed in-house and were T2-weighted to ensure consistency and cost efficiency. The Pfirrmann classification, as described by Pfirrmann et al. (11), was used to evaluate intervertebral disc degeneration. This classification involves ordinally scaled stages based on disc structure, nucleus-annulus distinction, signal intensity, and disc height. To improve accuracy, each disc was classified four times in a blinded manner (twice by experienced radiologists and twice by the spinal surgeon). Intra- and interrater reliability was validated using Cohen's kappa and Fleiss' kappa tests, and the mean values of all four assessments were used for analysis.

Comparisons of Pfirrmann values included:

1. The overall difference in disc degeneration (pre- vs. post-procedure).
2. Intra-individual comparisons between punctured and adjacent non-punctured discs.
3. Differences across surgical procedures (discography, IDET, ACUTHERM). To evaluate the impact of varying needle diameters (22-gauge for discography and 17-gauge for IDET/ACUTHERM), discs subjected to both discography and IDET were analyzed within the IDET group.

While the study lacked a true control group, adjacent intervertebral discs in the same patient were used as controls to reduce bias. Randomization was not possible due to limitations in surgical reports, recruitment, and allocation. Therefore, precise intra-individual comparisons were prioritized.

Secondary Outcomes Secondary outcomes included the percentage improvement in Numeric Rating Scale (NRS), Oswestry Disability Index (ODI), and SF-36 Index scores, measured approximately 9.1 years after surgery compared to preoperative values. The NRS asked patients to rate their average pain intensity (back or leg pain) over the previous two weeks on a scale from 0 to 10. The ODI is a self-administered questionnaire measuring "back-specific disability" across 10 items with six response categories each. SF-36 assessed health-related quality of life in areas such as physical functioning, social functioning, and mental health.

To exclude severe changes in biometric data after 10 years we also assessed possible the biometric data at follow up.

Statistical Analysis Data were expressed as mean ± standard deviation (SD) or median with confidence interval (CI). Statistical significance was determined using the Wilcoxon signed-rank test or Mann-Whitney U test, depending on the data distribution and whether samples were paired or independent. Differences between groups were analyzed with the Mann-Whitney U test, with p-values < 0.05 considered significant. Spearman's correlation test assessed relationships between independent variables.

Intra- and interrater reliability for Pfirrmann classifications was evaluated using Cohen's kappa and Fleiss' kappa. The results were interpreted according to Landis and Koch (1977). All statistical analyses were performed using SPSS software (version XX; SPSS Inc., Chicago, IL, USA).

Inclusion Criteria:

• Patients eligible for early intradiscal procedures included those with low back pain (NRS > 5) caused by discogenic pain due to disc degeneration or radicular pain due to disc protrusion and subsequent nerve root compression. All patients were required to have been resistant to conservative therapy. Diagnoses were based on patient history, physical examination, imaging studies, and, in some cases, provocative discography if discogenic pain could not otherwise be clearly identified.

Exclusion Criteria:

• • Perioperative complications.

  • Post-interventional lumbar spine surgery in the region to be examined.
  • Contraindications for a repeated MRI.
  • Metastases or infection of the spine since surgery.
  • Spinal canal stenosis.
  • A diagnosis of anxiety disorder, depression, or somatoform disorder since surgery, based on their medical history.

To be included in the retrospective study, patients must have undergone one of the specified intradiscal procedures, successfully established contact, voluntarily agreed to participate, and demonstrated sufficient language proficiency to complete study assessments.

All data can be shared if necessary