Department of Orthopaedics, Zhangzhou Affiliated Hospital of Fujian Medical University, No. 59, Sheng Li Road West, Xiangcheng District, Zhangzhou, 363000, Fujian, China.
Department of Nursing, Zhangzhou Health Vocational College, Zhangzhou, China.
J Orthop Surg Res. 2022 Mar 28;17(1):189. doi: 10.1186/s13018-022-03078-5.
Pubic symphysis diastasis (PSD) hinders the connection between bilateral ischia and pubic bones, resulting in instability of the anterior pelvic ring. PSD exceeding 25 mm is considered disruptions of the symphyseal and unilateral/bilateral anterior sacroiliac ligaments and require surgical intervention. The correct choice of fixation devices is of great significance to treat PSD. This study aimed to evaluate the construct stability and implant performance of seven fixation methods to treat PSD using finite element analysis.
The intact skeleton-ligament pelvic models were set as the control group. PSD models were simulated by removing relevant ligaments. To enhance the stability of the posterior pelvic ring, a cannulated screw was applied in the PSD models. Next, seven anterior fixation devices were installed on the PSD models according to standard surgical procedures, including single plates (single-Plate group), single plates with trans-symphyseal cross-screws (single-crsPlate group), dual plates (dual-Plate group), single cannulated screws, dual crossed cannulated screws (dual-canScrew group), subcutaneous plates (sub-Plate group), and subcutaneous pedicle screw-rod devices (sub-PedRod group). Compression and torsion were applied to all models. The construct stiffness, symphyseal relative micromotions, and von Mises stress performance were recorded and analyzed.
The construct stiffness decreased dramatically under PSD conditions. The dual-canScrew (154.3 ± 9.3 N/mm), sub-Plate (147.1 ± 10.2 N/mm), and sub-PedRod (133.8 ± 8.0 N/mm) groups showed better ability to restore intact stability than the other groups (p < 0.05). Regarding regional stability, only single-plate fixation provided unexpected regional stability with a diastasis of 2.1 ± 0.2 mm (p < 0.001) under a compressive load. Under a rotational load, the single-crsPlate group provided better regional angular stability (0.31° ± 0.03°, p < 0.001). Stress concentrations occurred in the single-Plate, sub-Plate, and sub-PedRod groups. The maximum von Mises stress was observed in the single-plate group (1112.1 ± 112.7 MPa, p < 0.001).
The dual-canScrew fixation device offers ideal outcomes to maintain stability and prevent failure biomechanically. The single-crsPlate and dual-Plate methods effectively improved single-Plate device to enhance regional stability and disperse stresses. The subcutaneous fixation devices provided both anterior pelvic ring stability and pubic symphysis strength.
耻骨联合分离（PSD）会阻碍双侧坐骨和耻骨之间的连接，导致前骨盆环不稳定。PSD 超过 25mm 被认为是耻骨联合和单侧/双侧前骶髂韧带的中断，需要手术干预。正确选择固定装置对于治疗 PSD 非常重要。本研究旨在通过有限元分析评估七种固定方法治疗 PSD 的结构稳定性和植入物性能。
完整的骨骼-韧带骨盆模型被设为对照组。通过去除相关的韧带来模拟 PSD 模型。为了增强后骨盆环的稳定性，在 PSD 模型中应用了空心螺钉。接下来，根据标准手术程序，在 PSD 模型上安装了七种前固定装置，包括单钢板（单钢板组）、带跨耻骨交叉螺钉的单钢板（单-crsPlate 组）、双钢板（双钢板组）、单空心螺钉、双交叉空心螺钉（双-canScrew 组）、皮下钢板（皮下钢板组）和皮下椎弓根螺钉-棒装置（皮下 PedRod 组）。对所有模型施加压缩和扭转。记录和分析了结构刚度、耻骨联合相对微运动和 von Mises 应力性能。
PSD 状态下结构刚度显著下降。双-canScrew（154.3±9.3N/mm）、皮下钢板（147.1±10.2N/mm）和皮下椎弓根螺钉-棒装置（133.8±8.0N/mm）组的恢复完整稳定性的能力明显优于其他组（p<0.05）。在区域稳定性方面，只有单钢板固定在压缩载荷下提供了意想不到的区域稳定性，分离度为 2.1±0.2mm（p<0.001）。在扭转载荷下，单-crsPlate 组提供了更好的区域角度稳定性（0.31°±0.03°，p<0.001）。单钢板、皮下钢板和皮下椎弓根螺钉-棒装置组出现了应力集中。单钢板组的最大 von Mises 应力为 1112.1±112.7MPa（p<0.001）。
双-canScrew 固定装置在维持稳定性和防止生物力学失效方面提供了理想的结果。单-crsPlate 和双钢板方法有效地改进了单钢板装置，以提高区域稳定性和分散应力。皮下固定装置提供了前骨盆环稳定性和耻骨联合强度。
