More pronounced effects of the extent of discectomy over the extent of laminectomy on postoperative biomechanics and clinical outcomes in unilateral biportal endoscopy for lumbar disc herniation.

Abstract

Unilateral biportal endoscopy (UBE) can be performed to treat lumbar disc herniation (LDH). Nevertheless, the postoperative clinical outcomes and spinal biomechanical implications following partial discectomy and laminectomy, which are inherent to UBE techniques for treating LDH, lack robust documentation in the literature. A total of 132 patients underwent UBE surgery for LDH at the L4-L5 segment. On the basis of intraoperative determinations, cases were classified as conservative discectomy (CD) or aggressive discectomy (AD) depending on the extent of discectomy. Postoperative three-dimensional computed tomography (CT) was used to categorize the extent of laminectomy 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. The visual analog scale (VAS) and Oswestry Disability Index (ODI) were used for the clinical evaluation. A biomechanical finite element method analysis was performed to assess the maximum von Mises stresses in the intervertebral discs and articular cartilage for six different surgical approaches. Statistically significant differences in both VAS scores for back pain and ODI scores were observed between the CD + (LC^1/3-LC^1/2) and AD + (LC^1/3-LC^1/2) groups within 3 months after surgery. Moreover, statistically significant differences in both the VAS scores for back pain and the ODI scores were observed between the CD + (LC^1/2-LC^2/3) and AD + (LC^1/2-LC^2/3) groups at 3 months after surgery. Statistically significant differences in both the VAS scores for back pain and ODI scores were also observed between the CD + (LC^1/3-LC^1/2) and CD + (LC^1/2-LC^2/3) groups within 1 month after surgery. No statistically significant differences were observed in the VAS or ODI scores between the AD + (LC^1/3-LC^1/2) and AD + (LC^1/2-LC^2/3) groups throughout the postoperative follow-up period. The maximum von Mises stresses of the L4‒L5 intervertebral disc and articular cartilage were greater in the AD group than in the CD group when the same-sized vertebral plate was removed. Although variations in the laminectomy size led to differential stresses on the intervertebral discs in both the CD and AD groups, the observed differences were not statistically significant. Early postoperative dissatisfaction after UBE may be correlated with excessive disc resection and excessive laminectomy. During UBE procedures, the degree of disc resection has a greater effect on both clinical outcomes and segmental biomechanics than the extent of laminectomy.