A novel pedicle-PMMA-augmented screw resists reverse windshield-wiper failure in osteoporotic spine fixation: parameter optimization by finite element analysis

作者：Dongsheng Wang, Jian Zhang, Bo Huang, Li Zhang, Jiming Liu, Baiyi Liu, P Liu, Yaoyao Liu · 发表于：BMC Musculoskeletal Disorders · 年份：2026 · DOI：10.1186/s12891-026-10242-z · 研究领域：Spinal Fractures and Fixation Techniques、Spine and Intervertebral Disc Pathology、Cervical and Thoracic Myelopathy

BACKGROUND: Conventional PMMA-augmented pedicle screws (CPPS) remain susceptible to "reverse windshield-wiper" failure in severe osteoporosis. This study aimed to elucidate this failure mechanism and develop a novel pedicle-PMMA-augmented screw (PPAS) with enhanced biomechanical stability under FE analysis. METHODS: An L4 vertebral finite element (FE) model incorporating threaded hollow-core CPPS with anterior injection holes was established, followed by simulation of PMMA diffusion characteristics. Under 100 N craniocaudal cyclic loading, screw stress distribution and displacement were recorded, with the stress concentration point (designated as Point P) identified. Additional injection holes were defined at Point P to determine the maximum PMMA volume (0.3 mL). Subsequently, 30 PMMA-augmented FE models with additional variable injection locations (P-2 to P + 3 screw pitches) and volumes (0.06-0.30 mL in 0.06 mL increments) were established to analyze screw stress distribution and displacement under craniocaudal loads for optimization of parameters and screw design. RESULTS: Under 100 N craniocaudal cyclic loading, FE analysis demonstrated that threaded CPPS with 1.5 mL PMMA reduced screw-tip stress, shifted the primary stress concentration from the screw tip to the narrowest pedicle notch region (Point P), and decreased screw-tail displacement. Augmentation with 0.3 mL PMMA at Point P achieved PMMA-cortex contact. FE analysis indicated that additional augmentation at this p...