Background: There are a few biomechanical studies that describe posterior fixation methods with pedicle screws (PS) and lateral mass screws (LMS); the combination of both screw types and their effect on an allograft spacer in a surgically treated cervical segment is unknown. Methods: Finite element model (FEM) analyses were used to investigate the effects of a hybrid technique using posterior PS and LMS. Stress distribution and subsidence risk from a combination of screws under hybrid motion control conditions, including flexion, extension, axial rotation, and lateral bending, were investigated to evaluate the biomechanical characteristics of different six-screw combinations. Findings: The load sharing on the allograft spacer in flexion mode was highest in the LMS model (74.6%) and lowest in the PS model (35.1%). The likelihood of subsidence of allograft spacer on C6 was highest in the screws from the distal LMS (type 5) model during flexion and extension (4.902 MPa, 30.1% and 2.189 MPa, 13.4%). In lateral bending, the left unilateral LMS (type 4) model screws on C5 (3.726 MPa, 22.9%) and C6 (2.994 MPa, 18.4%) yielded the greatest subsidence risks, because the lateral bending forces were supported by the LMS. In counterclockwise axial rotation, the left unilateral LMS (type 4) model screws on C5 (3.092 MPa, 19.0%) and C6 (3.076 MPa, 18.9%) demonstrated the highest subsidence risks. Conclusion: The asymmetrical ipsilateral use of LMS and posterior PS in lateral bending and axial rotation demonstrated the lowest stability and greatest subsidence risk. We recommend bilateral symmetrical insertion of LMS or posterior PS and posterior PS on distal vertebrae for increased stability and reduced risk of allograft spacer subsidence.

中文翻译：

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外侧块和椎弓根螺钉之间使用同种异体间隔物的后路固定组合的生物力学比较

背景：有一些生物力学研究描述了椎弓根螺钉 (PS) 和侧块螺钉 (LMS) 的后路固定方法；两种螺钉类型的组合及其对经手术治疗的颈椎节段的同种异体移植物间隔器的影响尚不清楚。方法：有限元模型 (FEM) 分析用于研究使用后验 PS 和 LMS 的混合技术的效果。研究了在混合运动控制条件下（包括弯曲、伸展、轴向旋转和横向弯曲）螺钉组合的应力分布和下沉风险，以评估不同六螺钉组合的生物力学特性。结果：在屈曲模式下，同种异体移植垫上的负荷分担在 LMS 模型中最高 (74.6%)，在 PS 模型中最低 (35.1%)。在屈伸过程中，来自远端 LMS（5 型）模型的螺钉在 C6 上的同种异体垫片下沉的可能性最高（4.902 MPa，30.1% 和 2.189 MPa，13.4%）。在横向弯曲中，C5（3.726 MPa，22.9%）和 C6（2.994 MPa，18.4%）上的左侧单边 LMS（4 型）模型螺钉产生最大的下沉风险，因为横向弯曲力由 LMS 支撑。在逆时针轴向旋转时，C5 (3.092 MPa, 19.0%) 和 C6 (3.076 MPa, 18.9%) 上的左侧单侧 LMS（4 型）模型螺钉显示出最高的下沉风险。结论：在侧弯和轴向旋转中不对称地使用 LMS 和后侧 PS 表现出最低的稳定性和最大的下沉风险。