Yang Jie-Xiang, Luo Lin, Liu Jin-Hui, Wang Nan, Xi Zhi-Peng, Li Jing-Chi
Department of Orthopedics, The Affiliated Traditional Chinese Medicine Hospital, Southwest Medical University, Luzhou, China.
Luzhou Key Laboratory of Orthopedic Disorders, Southwest Medical University, Luzhou, Sichuan, China.
Front Bioeng Biotechnol. 2024 Jan 8;11:1282512. doi: 10.3389/fbioe.2023.1282512. eCollection 2023.
Screw loosening is a widely reported issue after spinal screw fixation and triggers several complications. Biomechanical deterioration initially causes screw loosening. Studies have shown that incomplete insertion of pedicle screws increases the risk of screw breakage by deteriorating the local mechanical environment. However, whether this change has a biomechanical effect on the risk of screw loosening has not been determined. This study conducted comprehensive biomechanical research using polyurethane foam mechanical tests and corresponding numerical simulations to verify this topic. Pedicle screw-fixed polyurethane foam models with screws with four different insertion depths were constructed, and the screw anchoring ability of different models was verified by toggle tests with alternating and constant loads. Moreover, the stress distribution of screw and bone-screw interfaces in different models was computed in corresponding numerical mechanical models. Mechanical tests presented better screw anchoring ability with deeper screw insertion, but parameters presented no significant difference between groups with complete thread insertion. Correspondingly, higher stress values can be recorded in the model without complete thread insertion; the difference in stress values between models with complete thread insertion was relatively slight. Therefore, incomplete thread insertion triggers local stress concentration and the corresponding risk of screw loosening; completely inserting threads could effectively alleviate local stress concentration and result in the prevention of screw loosening.
螺钉松动是脊柱螺钉固定术后一个被广泛报道的问题，并引发多种并发症。生物力学退变最初会导致螺钉松动。研究表明，椎弓根螺钉植入不完全会使局部力学环境恶化，从而增加螺钉断裂的风险。然而，这种变化对螺钉松动风险是否具有生物力学影响尚未确定。本研究采用聚氨酯泡沫力学试验及相应的数值模拟进行了全面的生物力学研究，以验证这一课题。构建了具有四种不同植入深度螺钉的椎弓根螺钉固定聚氨酯泡沫模型，并通过交变和恒定载荷的翻转试验验证了不同模型的螺钉锚固能力。此外，在相应的数值力学模型中计算了不同模型中螺钉及骨-螺钉界面的应力分布。力学试验表明，螺钉植入越深，锚固能力越好，但在螺纹完全植入的组之间参数无显著差异。相应地，在螺纹未完全植入的模型中可记录到更高的应力值；螺纹完全植入的模型之间应力值差异相对较小。因此，螺纹未完全植入会引发局部应力集中及相应的螺钉松动风险；完全植入螺纹可有效缓解局部应力集中并预防螺钉松动。
