More Pronounced Effects of Discectomy over Laminectomy on Postoperative Biomechanics and Clinical Outcomes in UBE for Lumbar Disc Herniation

Background Context: Unilateral biportal endoscopy (UBE) can be performed to treat lumbar disc herniation (LDH). Previous research has suggested that partial laminectomy and facetectomy procedures during spinal surgery may compromise segmental biomechanical stability, potentially triggering postoperative facet joint degeneration with progression to facet arthropathy. Nevertheless, the postoperative clinical outcomes and spinal biomechanical implications following partial discectomy, laminectomy, and facetectomy, which are inherent to UBE techniques for lumbar disc herniation, lack robust documentation in the existing literature. Purpose This study aimed to evaluate the clinical outcomes following varying degrees of discectomy and laminectomy. Furthermore, finite element (FE) biomechanical analyses were employed to investigate potential biomechanical mechanisms underlying the observed clinical results. Study Design/Setting: Retrospective study and biomechanical FE analysis / Single academic medical center. Patient Sample: A total of 132 patients underwent UBE surgery for LDH at the L4–L5 segment. Outcome Measures: The Visual Analog Scale (VAS) for back and leg pain, Oswestry Disability Index (ODI), and maximum von Mises stresses in the intervertebral discs and articular cartilage via finite element analysis. Methods Based on intraoperative determinations, cases were classified as conservative discectomy (CD) or aggressive discectomy (AD) depending on the extent of nucleus pulposus removal. Postoperative three-dimensional computed tomography (CT) was used to categorize laminectomy extent into the following groups: one-third laminectomy (LC ^1/3 ) to half laminectomy (LC ^1/2 ) (LC ^1/3 ∽LC ^1/2 ), LC ^1/2 to two-thirds laminectomy (LC ^2/3 ) (LC ^1/2 ∽LC ^2/3 ), and greater than LC ^2/3 . Clinical evaluations (VAS, ODI) were conducted at specified intervals. A biomechanical finite element analysis assessed stresses for six surgical approach scenarios. Results Statistically significant differences in VAS scores for back pain were observed between the CD + (LC ^1/3 ∽LC ^1/2 ) group and the AD + (LC ^1/3 ∽LC ^1/2 ) group at 3 days, 1 month, and 3 months postoperatively. Statistically significant differences in both VAS and ODI scores were found between the CD + (LC ^1/2 ∽LC ^2/3 ) group and the AD + (LC ^1/2 ∽LC ^2/3 ) group at 3 months. Statistically significant differences in VAS scores were also observed between the CD + (LC ^1/3 ∽LC ^1/2 ) group and the CD + (LC ^1/2 ∽LC ^2/3 ) group at 3 days and 1 month. No statistically significant differences were identified between the AD + (LC ^1/3 ∽LC ^1/2 ) and AD + (LC ^1/2 ∽LC ^2/3 ) groups throughout follow-up. The maximum von Mises stresses at L4–5 were greater in AD groups than CD groups for equivalent laminectomy sizes. Laminectomy size variations caused non-significant stress differences within CD and AD groups. Conclusions Early postoperative dissatisfaction after UBE may be correlated with overly extensive discectomy and excessive laminar/facet joint resection. During UBE, the magnitude of discectomy exerts a greater impact on both clinical outcomes and segmental biomechanics than the extent of laminectomy.