Biportal endoscopic revision discectomy versus open microdiscectomy for recurrent lumbar disc herniation without instability: a systematic review and meta-analysis.

BACKGROUND: Revision surgery for recurrent lumbar disc herniation (RLDH) without instability is technically demanding because epidural scarring alters tissue planes. Biportal endoscopic revision discectomy may reduce access-related morbidity, but comparative evidence remains limited. OBJECTIVE: To compare biportal endoscopic revision discectomy with open microdiscectomy for RLDH without instability. METHODS: PubMed, Scopus, and ScienceDirect were searched from inception to 21 June 2026. Comparative adult studies were eligible. Random-effects meta-analyses calculated mean differences (MDs) and risk ratios (RRs) with 95% confidence intervals (CIs). Risk of bias was assessed using the seven-domain ROBINS-I tool. Exploratory trial sequential analysis (TSA) was performed for conventionally significant outcomes. The protocol was registered in PROSPERO (CRD420261429196). RESULTS: Three retrospective studies including 208 patients were analyzed: 91 underwent biportal surgery and 117 underwent open microdiscectomy. Biportal surgery was associated with shorter hospital stay (MD, -1.54 days; 95% CI, -2.73 to -0.36; I2 = 83%) and slightly lower long-term back-pain scores (MD, -0.37 points; 95% CI, -0.66 to -0.07; I2 = 0%). TSA did not confirm firm evidence for hospital stay (DARIS = 503; final Z = 2.56; boundary not crossed), whereas the long-term back-pain Z-curve crossed the monitoring boundary (DARIS = 28; final Z = 2.46). No significant differences were found in operative time, long-term leg pain, MacNab outcome, recurrence, durotomy, or overall complications. All studies had serious overall risk of bias. CONCLUSIONS: Biportal endoscopic revision discectomy may offer recovery-related advantages, but current evidence remains preliminary and does not establish superiority, equivalence, or noninferiority.