肱骨外侧髁骨折的伸肌腱作用机制探讨

Analysis of the Mechanism of Extensor Tractive Force on Humeral Ectocondylar Fracture

目的 采用光学弹性实验及三维有限元计算分析法 ,研究伸肌腱在不同体位加载下对肱骨外侧髁的应力作用规律 ,探讨肱骨外侧踝骨折的发生机制及治疗方案。方法 分别制造儿童肱骨三维光学弹性及有限元模型 ,模拟伸屈肘及前臂旋前、中立、旋后和内外翻等多种体位加载 ,观察和计算分析相应部位的应力分布状况。结果 各种体位肱骨外侧髁区平均应力值均最大 ;半屈肘时应力值远大于相应伸肘时 ,而伸肘时的伸肌腱作用节点应力值却大于外侧髁区 ;伸肘内翻位有伸肌腱作用力的加载下 ,肱骨外髁上部为拉应力条纹 ,内髁上部为压应力条纹。结论 儿童半屈肘位时易发生肱骨外侧髁骨折 ,而在伸肘内翻位时 ,以伸肌腱牵拉为主的弯力偶矩可拉脱外侧髁形成骨折 ;肱骨外侧髁骨折的复位可利用伸肌腱的牵拉作用 ,而固定则尽量避免伸肌腱的牵拉。

Objective To analyze the stress distribution on the humeral ectocondyle in the different posture with photo elastic experiment and three dimensional finite element method (3D-FEM). Methods Six kinds of loading posture were simulated to add on the child humeral model of 3D-FEM in order to file out the stress state on every node and unit in SUPER-SAP software;in photoelastic experiment,loading conditions of introversion,neutrality or extroversion of elbow were simulated to add on photo-elastic humeral model in order to observe the stress stripe of interference in the polarized light field. Results In all kinds of loading postures,the average Mises Stress of lateral condylar area was the largest.The stress at flection posture of elbow far exceeded that at extension posture of elbow,and at extension posture the stress of nodes affected by extensor tendon were larger than that of lateral condyle.At introversion postrure with extensor tendon tractive force,the upper area of medial condyle displayed pressure stress stripe while the upper area of lateral condyle displayed pulling stress stripe. Conclusion The fracture of lateral condyle of humerus occurrs easily at the flection posture of elbow in childhood,but at extension and introversion posture of elbow extensor tractive force could powerfully pull lateral condyle out of humerus and form fracture.We can use extersor tractive force to reduct the fracture of lateral condyle,and avoid extensor tractive force to fix it.