Percutaneous Endoscopic Interlaminar Discectomy via a Modified Inferolateral Margin of the L5 Pedicle Projection for L5/S1 Central Disc Herniation: A Retrospective Study

Objective: To evaluate the feasibility and short-term outcomes of a modified percutaneous endoscopic interlaminar discectomy (PEID) trajectory via the inferolateral margin of the L5 pedicle projection for central disc herniation at L5/S1. Methods: From June 2023 to July 2025, a consecutive cohort of 70 patients diagnosed with L5/S1 lumbar disc herniation (LDH) undergoing modified projection PEID was enrolled. Based on preoperative MRI (magnetic resonance imaging) evaluation of herniation types, they were divided into a central herniation group (n = 32) and a non-central herniation group (n = 38). Clinical outcomes and radiographic parameters were subsequently compared between the groups. Results: Seventy patients were included (38 non-central and 32 central). Baseline characteristics were comparable between the two groups except for a higher prevalence of bilateral symptoms in the central herniation group (p = 0.036). The central herniation group exhibited significantly shorter operative time (p = 0.027), reduced intraoperative blood loss (p = 0.047), and lower haemoglobin drop (p = 0.033). Multivariable linear regression confirmed that central herniation was independently associated with improved surgical efficiency. Both groups demonstrated significant postoperative improvements in VAS (Visual Analogue Scale) and JOA (Japanese Orthopaedic Association) scores. Although the non-central herniation group showed a higher JOA score on postoperative day 1 (p = 0.047), no significant differences were observed at 3 months or the final follow-up. The modified MacNab satisfaction rates were comparable (p = 0.411), with a similarly low complication rate in both groups. Conclusions: The modified PEID trajectory via the inferolateral margin of the L5 pedicle projection is feasible for central L5/S1 disc herniation and is associated with reduced operative time and decreased intraoperative blood loss.