Experimental Studies Of Biomechanics On Humeral Ectocondyle

Fracture of humeral ectocondyle is one of the most prevalent disorder of cubital articulation . In this subject, three-dimensional finite element method (3D-FEM) ,3D-photoelastic experiment and electric measure were used to study the practical state of suffered force of lateral condyle in elbow and the distributive principle of stress or strain.And then, through point of view of relations of stress and strain, We probed into the biomechanics mechanism of fracture of humeral ectocondyle under various kinds of postures between cubital articulation and forearm,and raised a better therapy of reduction and fixation. in 3D-FEM , according to the 3D-finite division regular we artificially divided the middle and lower part of humerus into 561 units (including 799 nodes) ,and used computer software to establish a 3D coordinate system of all the nodes in humerus model . Then ,we imitated the conditions of 6 kinds of postures,such as elbow extension or flection ,forearm pronation ,neutrality or supination ,adding the relative loads on the model under the relative boundary conditions of 6 kinds of postures. Through the calculation of SAP program, the computer can file out the stress. state of every node and unit. In 3D-photoelastic experiment , we made some 3D-humerus models with transparent material ?Eposy Resin by ways of founding technology .Imitating the loading conditions of introvesion ,neutrality orextroversion of elbow , we added loads to models in the oven at the temperature of 115 0C. Then, declined the temperature to congeal the state of stress of models ,made the section preparation in the cross-section,and put them in the polarized light field to observe the stress stripe of interference which were caused by double refraction .Thus, we can comprehand the stress state of Iatera] condyle. In electric measure ,we pasted resistance-strain flats on the front and rear area of humeral lateral condyle ,then linked them to resistance-strain surveying instrument to survey strain fluctuation which changed with loads fluctuation. So the strain state of lateral condyle could be showed. The results of experiments showed: (1) In child group, at no matter which postures,the average Mises Stress of lateral condylar area was largest,that of the radial area of trochlea of humerus seconded,and the ulnar area of trochlea of humerus was smallest ;17Jowever ,in the adult control group ,among lateral condylar area ,the radial area of trochlea of humerus and the ulnar area trochlea of humerus ,the differenciation of the average Mises Stress was not distinctive. (2) At flection posture of elbow, whether forearm at pronation, or neutrality or supination ,the average Mises Stress far exceeded those at extension posture of elbow , and at all kinds of postures, the average Mises Stress of front area of lateral condyle were larger than those of rear area of lateral condyle. (3) Whether forearm at pronation,neutratity or supination ,the average Mises Stess of nodes affected by extensor tendon were all larger than those of lateral condyle of humerus at extension posture of elbow,at the same time the average Mises Stress of nodes affected by extensor tendon were obviously less than those of lateral condyle at flection posture of elbow. (4)Whether elbow at introversion,neutral ity or extroversion, whether extensor tendon affected or not,viewed on coronal section,Iateral condylar area and radial area of...