Clinical and Surgical Predictors of Recurrent L5–S1 Disc Herniation Following Microdiscectomy: A Retrospective Survival Analysis

Recurrent lumbar disc herniation remains a prominent clinical challenge following microdiscectomy, particularly at the L5–S1 level, which has distinct biomechanical characteristics. While various radiological and clinical predictors have been proposed, the influence of surgical laterality has not been adequately explored. This study aimed to identify independent predictors of recurrence following L5–S1 microdiscectomy, with a specific focus on surgical laterality. This retrospective cohort study included patients who underwent primary L5–S1 microdiscectomy at a single center with a minimum follow-up of 12 months. Recurrence was defined as same-level, same-side herniation confirmed by imaging and clinical findings. Demographic, clinical, and radiological parameters—including facet tropism, disc height index, Modic changes, and multifidus morphology—were analyzed. Recurrence-free survival was assessed using Kaplan–Meier analysis, and independent predictors were identified through Cox proportional hazards regression. Patients with recurrence were significantly older and had higher rates of preoperative neurological deficits and systemic comorbidities. Radiological parameters showed no significant association with recurrence. In multivariable Cox regression analysis, left-sided surgery emerged as the strongest independent predictor, associated with a 3.5-fold increased hazard of recurrence (aHR: 3.506; 95% CI: 1.537–7.999; p = 0.003). Systemic comorbidities also independently increased recurrence risk (aHR: 2.051; 95% CI: 1.000–4.208; p = 0.050). Kaplan–Meier analysis demonstrated significantly shorter recurrence-free survival in patients undergoing left-sided procedures. Recurrence after L5–S1 microdiscectomy appears to be driven more by surgical and systemic factors than by conventional radiological parameters. Surgical laterality, particularly left-sided procedures, represents a novel and significant predictor of recurrence. These findings highlight the potential role of technical and patient-related factors in surgical outcomes.