踝关节融合术两种固定方式的三维有限元分析

Finite element modeling of ankle arthrodesis with two fixation techniques

[目的]通过三维有限元方法对踝关节融合的两种固定方式进行对比评价,并对其固定生物力学机制进行初步分析,为其临床应用提供理论依据。[方法]以正常人体踝关节CT扫描断层数据为基础,建立踝关节三维模型,模拟进行3螺钉固定和腓骨支撑固定手术,对模型中立、背屈、内旋和外旋4种载荷进行加载,分别进行有限元求解。[结果]3螺钉固定与腓骨支撑固定在抗旋转载荷上无明显差别,而在对抗背屈载荷作用优于腓骨支撑固定;在融合加压效果方面,3螺钉固定优于腓骨支撑固定,而腓骨支撑固定在移除外侧支撑腓骨后,加压作用有所下降;与腓骨支撑固定相比,3螺钉固定后的胫骨应力峰值更高且分布更集中,术后发生应力性骨折风险较高。[结论]在正常骨质条件下,3螺钉固定的生物力学稳定性以及融合加压效果均优于腓骨支撑固定,临床上建议首选3螺钉固定;而腓骨支撑固定的安全性较高,更适用于骨质条件较差的患者。

[ Objective] To qualitatively compare stability provided by two fixation techniques in ankle arthrodesis and study the biomechanical characteristics, using the finite element method. [ Method ] A three-dimensional model of a healthy ankle was developed from computed tomography images. Ankle arthrodesis fixed either by 3 screws or 4 screws with fibular strut graft was simulated by Abaqus 6.9 software. Then the model was submitted to mechanical analysis under four load patterns simulating postoperative activity of the ankle joint. [ Result] Three screws fixation had a comparable anti-rotation effect on fusion site to fib- ular strut fixation. Under the dorsiflexion load, a better stability was provided by 3 screws fixation rather than fibular strut fixa- tion. Three screws fixation also yielded greater compression at fusion site than fibular strut fixation. Once the fibular strut was re- moved, compression effect was lower than before. In the safety evaluation, higher stress peak and stress concentration on distal tibia were found in 3 screws fixation rather than fibular strut fixation. [ Conclusion ] In the condition of bone quality, 3 screws fixation showed better biomechanical stability and compression at fusion site when compared to fibular strut fixation. However, fibular strut fixation tended to lower the risk of stress fracture of distal tibia, especially in patients with low bone quality.