Finite element method (FEM) was used to investigate the biomechanical properties of three types of surgical fixations of U-shaped sacral fractures. Based on a previously established and validated complete lumbar-pelvic model, three models of surgical fixations of U-shaped sacral fractures were established: ① S1S2 passed through screw (S1S2), ② L4-L5 pedicle screw + screw for wing of ilium (L4L5 + IS), and ③ L4-L5 pedicle screw + S1 passed through screw + screw for wing of ilium (L4L5 + S1 + IS). A 400 N force acting vertically downward, along with torque of 7.5 N·m in different directions (anterior flexion, posterior extension, axial rotation, and axial lateral bending), was exerted on the upper surface of L4. Comparisons were made on differences in separation of the fracture gap and maximum stress in sitting and standing positions among three fixation methods. This study showed that: for values of separation of the fracture gap produced by different operation groups in different positions, L4L5 + S1 + IS was far less than L4L5 + IS and S1S2. For internal fixators, the maximum stress value produced was: L4L5 + IS > L4L5 + S1 + IS > S1S2. For the intervertebral disc, the maximum stress value produced by S1S2 is much larger than that of L4L5 + S1 + IS and L4L5 + IS. In a comprehensive consideration, L4L5 + S1 + IS could be prioritized for fixation of U-shaped sacral fractures. The objective of this research is to compare the biomechanical differences of three different internal fixation methods for U-shaped sacral fractures, for the reference of clinical operation.
采用有限元法对三种 U 型骶骨骨折后手术固定模型的生物力学特性进行了研究。在之前建立并验证有效的完整腰椎—骨盆模型的基础上，建立了三种 U 型骶骨骨折手术固定模型：① S1S2 贯穿螺钉（S1S2），② L4–L5 椎弓根螺钉 + 髂骨翼螺钉（L4L5 + IS），③ L4–L5 椎弓根螺钉 + S1 贯穿螺钉 + 髂骨翼螺钉（L4L5 + S1 + IS）。然后，通过对 L4 上表面施加 400 N 竖直向下的力以及 7.5 N·m 不同方向的扭矩（前屈、后伸、轴向旋转、轴向侧弯），对比三种固定方式在坐姿和站姿下产生的骨折缝隙分离值和最大应力的差异。研究结果表明，在不同姿态下，不同手术组产生的骨缝隙分离值为：L4L5 + S1 + IS 远小于 L4L5 + IS 和 S1S2。对于内植入物而言，上述三种固定方式产生的最大应力值为 L4L5 + IS > L4L5 + S1 + IS > S1S2；对于椎间盘而言，上述三种固定方式产生的最大应力值为 S1S2 远大于 L4L5 + S1 + IS 和 L4L5 + IS。综合考虑，对于 U 型骶骨骨折而言，可以优先考虑 L4L5 + S1 + IS 固定方式进行固定。本文研究的目的在于通过比较采用三种不同的内固定方式固定 U 型骶骨骨折后的生物力学的差异，进而为临床手术提供有效的参考。.
Keywords: L4–L5 pedicle screw; S1S2 passed through screw; U-shaped sacral fractures; screw for wing of ilium; value of separation of the fracture gap.