Zhao Peishuai, Li Renjie, Chen Jiaqiang, Wang Yongsheng, Guan Jianzhong, Wu Min
Department of Orthopaedics, The First Affiliated Hospital of Bengbu Medical College, Bengbu, China.
Front Bioeng Biotechnol. 2025 Aug 25;13:1631457. doi: 10.3389/fbioe.2025.1631457. eCollection 2025.
Due to its inherent high instability, the selection of fixation strategies for unilateral Denis type II sacral fractures remains a controversial challenge in the field of traumatic orthopedics. This study focuses on unilateral Denis type II sacral fractures. By applying three different fixation methods, it aims to explore their biomechanical properties and provide a theoretical basis for optimizing clinical fixation protocols.
A ligament-intact three-dimensional finite-element model of a right-sided Denis type II sacral fracture, including ipsilateral superior and inferior pubic rami fractures, was generated. Three fixation models were simulated: (1) S1/S2 transiliac-transsacral screw fixation (S1/S2-TTS); (2) unilateral L4/5 triangular osteosynthesis (UTOS); and (3) bilateral S2-alar-iliac screws combined with an iliosacral screw (BS2AI-ISS). Appropriate material properties, boundary conditions, and loading protocols were assigned. A 500 N axial compressive load superimposed with a 7.5 Nm torque was applied to simulate standing position and multiplanar spinal motion. Biomechanical parameters evaluated included vertical sacral stiffness, maximum von Mises stress within implants, and relative interfragmentary displacement (RID) at the fracture site.
Sacrum vertical stiffness: All constructs significantly increased sacrum vertical stiffness compared with the intact model. Normalised stiffness values were 443.18% (S1/S2-TTS), 228.38% (UTOS) and 397.26% (BS2AI-ISS). Maximum implant von Mises stress: Under every loading mode, S1/S2-TTS exhibited the lowest and most evenly distributed stress (range 30.30-49.23 MPa). Maximum stresses ranked from lowest to highest: S1/S2-TTS < BS2AI-ISS < UTOS. Relative interfragmentary displacement: In standing position, mean RID were 0.0313 ± 0.0148 mm (S1/S2-TTS), 0.0736 ± 0.0314 mm (UTOS) and 0.0539 ± 0.0163 mm (BS2AI-ISS). Only the difference between S1/S2-TTS and UTOS reached statistical significance (p = 0.047). Similar patterns were observed in extension, left flexion and left rotation; no significant differences were found in right flexion or right rotation.
The present study demonstrates that BS2AI-ISS provides biomechanical stability comparable to both S1/S2-TTS and UTOS for unilateral Denis type II sacral fractures. Notably, BS2AI-ISS achieves this stability without compromising lumbar motion and irrespective of sacral morphologic variations. These findings suggest that BS2AI-ISS may serve as an effective alternative for managing unilateral Denis type II sacral fractures.
由于其固有的高度不稳定性，单侧Denis II型骶骨骨折固定策略的选择在创伤骨科领域仍然是一个有争议的挑战。本研究聚焦于单侧Denis II型骶骨骨折。通过应用三种不同的固定方法，旨在探索它们的生物力学特性，并为优化临床固定方案提供理论依据。
建立了一个右侧Denis II型骶骨骨折的韧带完整三维有限元模型，包括同侧耻骨上下支骨折。模拟了三种固定模型：（1）S1/S2经髂-经骶螺钉固定（S1/S2-TTS）；（2）单侧L4/5三角骨固定术（UTOS）；（3）双侧S2-翼-髂螺钉联合髂骶螺钉（BS2AI-ISS）。赋予了适当的材料特性、边界条件和加载方案。施加500 N轴向压缩载荷并叠加7.5 Nm扭矩以模拟站立位和多平面脊柱运动。评估的生物力学参数包括骶骨垂直刚度、植入物内的最大von Mises应力以及骨折部位的相对骨折块间位移（RID）。
骶骨垂直刚度：与完整模型相比，所有结构均显著增加了骶骨垂直刚度。标准化刚度值分别为443.18%（S1/S2-TTS）、228.38%（UTOS）和397.26%（BS2AI-ISS）。植入物最大von Mises应力：在每种加载模式下，S1/S2-TTS表现出最低且分布最均匀的应力（范围为30.30 - 49.23 MPa）。最大应力从低到高排序为：S1/S2-TTS < BS2AI-ISS < UTOS。相对骨折块间位移：在站立位时，平均RID分别为0.0313±0.0148 mm（S1/S2-TTS）、0.0736±0.0314 mm（UTOS）和0.0539±0.0163 mm（BS2AI-ISS）。仅S1/S2-TTS与UTOS之间的差异具有统计学意义（p = 0.047）。在伸展、左侧屈曲和左侧旋转时观察到类似模式；在右侧屈曲或右侧旋转时未发现显著差异。
本研究表明，对于单侧Denis II型骶骨骨折，BS2AI-ISS提供的生物力学稳定性与S1/S2-TTS和UTOS相当。值得注意的是，BS2AI-ISS在不影响腰椎运动且不受骶骨形态变异影响的情况下实现了这种稳定性。这些发现表明，BS2AI-ISS可能是治疗单侧Denis II型骶骨骨折的一种有效替代方法。
