Zigong Fourth People's Hospital, Zigong, China.
Hospital of Chengdu Office of People's Government of Tibetan Autonomous Region (Hospital. C. T), Chengdu, China.
BMC Musculoskelet Disord. 2024 Nov 20;25(1):931. doi: 10.1186/s12891-024-08047-z.
This study aims to conduct a finite element analysis (FEA) to assess the bio-mechanical properties of C2 sagittal-parallel pedicle screw (PPS) in fixation for atlantoaxial instability, thereby providing a theoretical foundation for its clinical application.
A total of 5 intact C1-2 finite element models were established. Based on this, instability models were developed and two different fixation methods were applied for each model: C1 lateral mass screw (LMS) combined with C2 sagittal-parallel pedicle screw (C1LMS + C2PPS), and C1 lateral mass screw combined with C2 traditional pedicle screw (C1LMS + C2PS). Under a physiological load of 40 N, a pure moment of 1.5 Nm was used to simulate movements of the cervical spine in flexion, extension, lateral bending, and axial rotation. The von Mises stress of implants and the segment range of motion (ROM) were analyzed and compared statistically.
The intact model was validated and showed good consistency with other studies in terms of range of motion (ROM). In flexion and extension, the C1LMS + C2PPS resulted in lower segment ROM (12.4% and 6.3% decrease) and stress concentration (15.9% decrease in flexion) compared to C1LMS + C2PS. However, in lateral bending and axial rotation, the C1LMS + C2PPS exhibited higher segment ROM (42.9% and 5.9% increase) and stress concentration (8.7% and 21.4% increase) compared to C1LMS + C2PS.
Both methods were safe and stable for the fixation of atlantoaxial instability. Compared to C1LMS + C2PS, the use of C1LMS + C2PPS may provide better stability and a lower risk of implant failure in flexion and extension. Clinically, it is feasible to utilize the C2 sagittal-parallel pedicle screw in fixing atlantoaxial instability.
本研究旨在通过有限元分析（FEA）评估 C2 矢状平行椎弓根螺钉（PPS）固定寰枢椎不稳的生物力学特性，为其临床应用提供理论基础。
共建立 5 个完整的 C1-2 有限元模型。在此基础上，建立不稳模型，并对每个模型采用两种不同的固定方法：C1 侧块螺钉（LMS）联合 C2 矢状平行椎弓根螺钉（C1LMS+C2PPS）和 C1 侧块螺钉联合 C2 传统椎弓根螺钉（C1LMS+C2PS）。在 40N 的生理负荷下，使用 1.5Nm 的纯力矩模拟颈椎屈伸、侧屈和旋转运动。分析和比较了植入物的 von Mises 应力和节段活动范围（ROM）。
完整模型得到验证，在活动范围（ROM）方面与其他研究具有良好的一致性。在屈伸运动中，与 C1LMS+C2PS 相比，C1LMS+C2PPS 导致节段 ROM 降低（12.4%和 6.3%）和应力集中减少（屈伸时减少 15.9%）。然而，在侧屈和轴向旋转运动中，与 C1LMS+C2PS 相比，C1LMS+C2PPS 表现出节段 ROM 增加（42.9%和 5.9%）和应力集中增加（8.7%和 21.4%）。
两种方法均安全稳定地固定寰枢椎不稳。与 C1LMS+C2PS 相比，使用 C1LMS+C2PPS 在屈伸运动中可能具有更好的稳定性和降低植入物失效的风险。临床上，使用 C2 矢状平行椎弓根螺钉固定寰枢椎不稳是可行的。
