The Experimental Study Of Orthopedic Shoes On Calcaneal Fractures By Electric Measure And Finite Element Analysis

Objective: According to the theory of association of activity and inertia of traditional Chinese medicine for fractures, and the theory of modern biomechanics, material engineering, the orthopedic shoes were designed on calcaneal fractures which accord with the biomechanical principle. And biomechanical experiments had been done in order to offer the theoretical foundation for the further clinical experiment.Methods Electric measure and two-dimensional (2-D) finite element analysis(FEA) were adopted to biomechanical test to the feet and orthopedic shoes. 1 Electric measure: choosing 5 at random from 10 (5 pairs) adult's male corpse shanks, making Fracture models, another 5 are normal, load and electric measure them fixed with orthopedic shoes after them had been load and measured unfixed. 2 FEA: 2.1 Establishing the 2-D finite element models. A set of Computed Radiography(CR) film was selected, which included heel-strike(HS) phase, mid-stance(MS) phase and pull-off(PO) phase of the right lateral foot of a normal male volunteer and right foot fixed by orthopedic shoes. Six 2-D finite element models were development by the Super-sap software including HS, MS and PO phase of normal foot and foot fixed by orthopedic shoes. Twelve fracture models of these phases were also established by changing the material parameters, Young's modulus, Poisson's ratio in the fracture area. Eight static mid-stance phase models were established by change the loads. Twenty six FA models were established in this experiment 2.2grouping: group A(no fracture and unfixed), group B(no fracture and fixed), group C(fractured but unfixed) and group D(fractured and fixed) were divided according to whether fracture or not and fixed by orthopedic shoes or not. The latter 2 groups both were divided into two groups, group C1, group C2, group D1 and group D2 according to the type of fracture corresponding to tongue form fracture and joint compressing type fracture separately. Tongue form fracture was considered only in thestatic FEA, and through change loads simulation the situation of one foot stand and two feetstand.Results: 1 Electricity examine result show the stress value in the resistance slices area, the fracture area, have significance reduction than unfixed situation. 2 It is found that the highest von Mises stress (VMS) of the calcaneus during HS phase when unfixed occurs at the posterior of the calcaneus(PC), the lesser at the inferior of calcaneus(IC), the posterior subtalar facets(PSF). And it is calcaneal-cuboid facets (CCF) facets, mid-subtalar facets (MSF), posterior subtalar facets (PSF) after fixed. The VMS of IC, PC, the dorsal posterior tubercle (DPT), fracture area (FA) obviously reduced, and CCF increased obviously than unfixed. 3 The highest VMS of the calcaneus during MS phase when unfixed occurs at IC, the lesser at the 3rd FA, PSF. And it is CCF, MSF, DPT after fixed. The VMS of IC, PC, DPT, PSF, FA obviously reduced, and CCF, MSF increased obviously than unfixed. 4 The highest VMS of the calcaneus during PO phase when unfixed occurs at CCF, the lesser at MSF, DPT. And it is CCF, MSF, DPT after fixed. The VMS of IC, PC, DPT, PSF, FA obviously reduced, and CCF, MSF increased obviously than unfixed. 5 The highest VMS of the calcaneus during stand situation by one or two feet when unfixed occurs at IC, the lesser at the 3rd FA, CCF. And it is CCF, MSF after fixed. The VMS of IC, PC, DPT, PSF, PSF, FA obviously reduced, and CCF increased obviously than unfixed.Conclusions: 1 The unanimous laws about the stress distributed were drawn from electric measure and FEA in this thesis. It means that the models have the characters of stability, reliability and reproducibility. 2 The VMS of IC, PC, DPT, PSF, FA obviously reduced, before unfixed with orthopedics shoes. It indicated that the orthopedic shoes correspond with the principle of fixation for calcaneal fractures. 3 The orthopedic shoes after improve properly can be used in the clinical experiment of the calcaneal fractures which are not involved calcaneal-cuboid joint, and the displacements are less than 2mm, and can be or nearly to anatomical reduction.