Experimental Study Of Biomechanics On The Treatment Of The Shaft Fractures Of The Radius And Ulna With Multilayer Splint

A method of 2-D and 3-D finite element analysis (FEA) was used to study the biomechanical mechanism of the treatment of the shaft fractures of the radius and ulna with the multilayer-splint, and at the same time, to compare the difference among the multilayer splint(M-S), the traditional splint(T-S), and the double splint(D-S).CT technique was used to get transects of the forearm at the normal position. According to the division principle of FEA, we used the software of FEA(SAP-93) to set up forty-five 2-D models of forearm fixed by M-S^ T-S and D-S separately and then imitated the condition of three kinds of fixation, to add the relative load on the models and calculate the stress of the nodes and units in 2-D models. The 3-D models of the radius and ulna were divided into 414 units (including 780 nodes). Through changing the Young's modulus of some units , three kinds of fracture models caused by the direct force > the indirect force and the rotating force separately were set up. We added the load according the fixation ofM-S, T-S and D-S, and then calculated the displacement of the bottoms of the fractures.The results indicate: in 2-D models, the dividing-stress on D-S and M-S is larger than that on T-S (P0.01,P<0.05), but there is no difference between M-S and D-S(P>0.1). In 3-D models of the fractures, The displacement of the bottoms of the fractures on M-S caused by the exercise-load is the least than that on T-S and D-S, the largest is D-S, but among the direct-force fractures, the indirect-force fractures and the rotating-force fractures , the direct-force fractures is the least.The results of the experiment demonstrated the principle of the M-S maybe: 1) Through refining T-S, the fixation of M-S not only solves the correspondence between the splint and the forearm , but also increases the dividing-stress between the radius and ulna, and so it could keep stabilization of the shaft fractures of the radius and ulna. 2) The fixation of M-S compared with the others could decrease the displacement of the fracture bottoms and provide a steady mechanical condition for exercise. 3) The M-S which is made of the firry cortices corresponds with the elastic principle; it is a suitable external fixation for the forearm fractures.