Diagnostic Selective Nerve Root Block (SNRB) in Lumbar Nerve Root Compression

Background and Aim Selective nerve root blocks (SNRBs) are widely used in spine surgery for diagnostic clarification in patients with radicular pain, particularly when imaging (MRI) and clinical findings are inconclusive regarding the symptomatic nerve root or the expected benefit of surgical decompression. The purpose of the block is to clarify the diagnosis and prognosis of radiating lower limb pain, thereby supporting decision-making regarding surgical versus non-surgical treatment. The primary aim of this study is to investigate the prognostic value of selective nerve root blocks in lumbar nerve root compression. Objectives and Hypotheses Primary objective: To assess whether patients undergoing surgery after a diagnostic block with good effect demonstrate different postoperative outcomes, measured by the Oswestry Disability Index (ODI) at 12 months, compared with patients undergoing surgery without a prior block, adjusted for relevant confounders. Hypothesis: Patients with a positive diagnostic block who subsequently undergo surgery experience less postoperative improvement, measured by ODI, compared with patients undergoing surgery without prior diagnostic uncertainty. Study Design Retrospective cohort study based on registry data and medical records. Population and Eligibility Criteria Inclusion criteria: - Patients aged >18 years - Underwent diagnostic selective lumbar nerve root block (BAFA7) between January 1, 2018 and May 31, 2024 at Zealand University Hospital, Køge Exclusion criteria: - Therapeutic (non-diagnostic) blocks - Missing data regarding block level, side, effect, or subsequent surgery - Missing 12‑month follow-up in DaneSpine - Surgery performed at a different spinal level than the block Data Sources and Variables Primary data sources include the Health Platform, private hospital records, and DaneSpine. Collected variables include demographics, block characteristics, surgical details, and PROM data (ODI, VAS, EQ‑5D). Outcome Measures Primary outcome: - ODI at 12 months postoperatively Secondary outcomes: - Patient satisfaction - Likelihood ratios and predictive values - Avoided surgery following negative block - Re-referral to the spine clinic at any time during follow-up Statistical Analysis Mixed-effects linear regression models will be applied. Fixed effects include block status and relevant covariates, while patient ID is included as a random effect. Ethical Considerations This retrospective registry study involves no patient contact and has been approved in accordance with the Danish Health Act §46.2 and 5, EMN-2025-04765. Data handling complies with GDPR regulations and the project is registered at the institutional registry for research projects, p-2025-19418 Timeline Protocol and approvals: March–August 2025 Data extraction: September–January 2026 Analysis: February 2026 Manuscript preparation: February - June 2026 Publication Plan Results will be published open access. Authorship follows ICMJE guidelines.