Objective To investigate the correlation between cervical sagittal imbalance, disc morphology, and localized ossification of the posterior longitudinal ligament (LOP) in patients with single-level cervical disc herniation. Methods A cross-sectional study was conducted on 150 patients with single-level cervical disc herniation and complete imaging data (including standard X-ray film, CT, and MRI). Patients were divided into the LOP(+) group (n=76, with LOP at the herniated segment) and the LOP (?) group (n=74, without LOP) based on the presence of LOP. Univariate and logistic regression analyses were performed to identify factors associated with LOP, including gender, age, body mass index, C-reactive protein, fasting blood glucose, serum uric acid, maximum diameter of herniated disc, the maximum base width of herniated disc, spinal canal occupancy rate, height of intervertebral space, Pfirrmann grade of disc degeneration, C2-7 Cobb angle, T1 slope, cervical sagittal vertical axis (cSVA), C2-7 Cobb angle in extension/flexion, global cervical range of motion (ROM), and extension/flexion angle and ROM at the index level. Pearson or Spearman correlation was used to analyze the correlation of the main imaging parameters between the two groups. Results Univariate analysis showed that Pfirrmann grade, maximum base width of herniated disc, spinal canal occupancy rate, height of intervertebral space, C2-7 Cobb angle, extension angle and ROM at the index level were the influencing factors of LOP (P<0.05). Further logistic regression analysis revealed that the increase of the maximum base width of the herniated disc and the decrease of the spinal canal occupancy rate were the independent influencing factors of LOP (P<0.05). Correlation analysis showed that the correlation patterns among the main radiological parameters were not identical between the LOP (?) and LOP (+) groups. In both groups, the C2-7 Cobb angle was positively correlated with T1 slope (P<0.05), and some segmental motion parameters were correlated with global cervical ROM and dynamic C2-7 Cobb parameters (P<0.05). In the LOP (+) group, spinal canal occupancy rate, cSVA, OPLL thickness, and disc morphological parameters also showed certain correlations (P<0.05). Conclusion Cervical sagittal imbalance (characterized by reduced lordosis and segmental mobility) and disc base expansion are significantly associated with LOP coexistence in single-level cervical disc herniation patients. These imaging markers may aid early identification of high-risk populations in clinical settings.
Objective To explore the impact of different lamina formation ranges on the biomechanical stability of L5, S1 in spine surgery with unilateral biportal endoscopy (UBE), providing a theoretical basis for optimizing clinical surgical plans. Methods A complete lumbar finite element model (M0) was constructed based on CT data of L3-S1 from a healthy male volunteer. Four different UBE surgical models with varying lamina formation ranges (M1-M4) were simulated. M1 model involved initial laminectomy with essentially intact facets; M2 model involved minor facet resection (5-10 mm from the inferior facet joint surface); M3 model involved greater facet resection with partial laminectomy depth >10 mm; M4 model involved complete facet resection to simulate extreme decompression. Finite element analysis was performed to assess the range of motion (ROM), maximum displacement, and maximum von Mises stress of the vertebrae under different physiological activities (flexion, extension, left/right bending, and left/right rotation), as well as the maximum displacement and maximum von Mises stress of the intervertebral disc, and the maximum von Mises stress of right facet joints under left rotation and right bending. Results With increasing forming range, the ROM of the vertebrae in flexion showed a slight increase (0.32° higher in M4 model than in M0 model), and the maximum displacement generally increased in all motion states. For the intervertebral disc, the maximum von Mises stress and displacement increased mildly in flexion and left rotation, which were approximately 17% and 12% higher in M3 and M4 models than in M0 model, respectively. And the biomechanical parameters changed little among different models under extension, right rotation, and left bending. The von Mises stress of the right facet joint increased stepwise with forming range during left rotation (about 57% higher in M3 model than in M0 model) and was higher in all surgical models than in M0 model during right bending. ConclusionExpanding the lamina formation range in UBE spine surgery can lead to reduced stability in flexion and left rotation activities at L5, S1, increasing the mechanical load on the intervertebral disc and facet joints. Clinically, under the premise of achieving adequate decompression, prioritizing a forming range corresponding to the lower transverse width partition (25%-50%) may better balance decompression efficacy with biomechanical stability of the L5, S1 segment, thereby reducing the potential risk of long-term degeneration caused by excessive bony resection.