Biomechanical Comparison of Unilateral Biportal Endoscopy and Percutaneous Endoscopic Lumbar Discectomy Using a Finite Element Model

Background: Lumbar disc herniation (LDH) remains a significant cause of back and leg pain and disability worldwide, necessitating effective surgical intervention when conservative treatments fail. Objective: This study aims to compare the biomechanical properties of unilateral biportal endoscopy (UBE) discectomy and percutaneous endoscopic lumbar discectomy (PELD) with those of open microscopic discectomy (OD) for treating LDH. Methods: Finite element analysis (FEA) was used to evaluate and compare postoperative biomechanical outcomes, focusing on stress distribution, spinal segment flexibility, and postoperative structural integrity. A single patient-specific L4-L5 finite element model was constructed from a high-resolution CT dataset and modified to simulate intact, OD, UBE, and PELD conditions. Results: All three surgical models showed increased range of motion relative to the intact model, with the largest changes in the OD model. The greatest increase occurred in extension (OD, +12.4%; UBE, +4.6%; PELD, +3.5%). Peak von Mises stress in the nucleus pulposus and annulus fibrosus increased across all models, with the greatest increases in OD and the least in PELD. During extension, facet stress increased by 60.0% in the OD model and 14.4% in the UBE model, whereas the PELD model remained essentially unchanged (-1.6%). Conclusion: Within this single patient-specific model, models with less posterior osteoligamentous resection showed smaller deviations in range of motion and lower peak stresses. These findings suggest an association between the extent of structural resection and immediate postoperative biomechanical changes, rather than an inherent superiority of any particular technique. The results are model-specific and hypothesis-generating, and require validation across multiple patient-specific models and clinical studies.