A four-type index-surgery-based scar pattern framework and layered surgical strategy for unilateral biportal endoscopic lumbar revision surgery: an 87-patient series

To evaluate the feasibility and safety of unilateral biportal endoscopy (UBE) across diverse lumbar revision scenarios and to propose an index-surgery-based four-type scar pattern framework with corresponding stratified surgical strategies. A single-center retrospective descriptive case series of 87 consecutive patients undergoing UBE lumbar revision surgery was conducted. Patients were classified into five clinical subtypes: Type A (revision decompression after decompression, n = 28), Type B (revision decompression after fusion, n = 21), Type C (revision fusion after decompression, n = 14), Type D (failed fusion revision, n = 9), and Type E (revision fusion for adjacent segment disease with instability, n = 15). An index-surgery-based four-type scar pattern framework (Types I–IV) was preliminarily developed. Interobserver and intraobserver reliability were assessed using Cohen’s kappa. All patients completed at least 8 months of follow-up (range, 8–14 months), with 35 of 38 fusion subtypes completing at least 12 months of CT follow-up. All procedures were completed without open conversion. The overall dural tear rate was 4.6% (4/87), all in Type IV scar pattern cases. Additional complications included transient nerve root traction injury ( n = 2), symptomatic epidural hematoma ( n = 1), transient dysesthesia ( n = 3), and superficial wound dehiscence ( n = 1), all resolving without permanent sequelae. Interobserver and intraobserver kappa values were 0.81 and 0.88, respectively. All subtypes showed improvement in pain and functional scores at final follow-up (uncorrected P < 0.05 for all three outcomes within each subtype). After Bonferroni correction for multiple comparisons within each subtype, improvements in most outcomes remained significant in Types A, B, C, and E; no outcome in Type D retained significance after correction. UBE is a feasible technique for selected lumbar revision pathologies when performed by an experienced team. The proposed scar pattern framework demonstrates substantial agreement within its intended clinical workflow and provides a preliminary structured framework for surgical planning. These frameworks remain hypothesis-generating and require multicenter validation.