3-DIMENSIONAL FINITE-ELEMENT STRESS-ANALYSIS OF THE POLYPROPYLENE, ANKLE-FOOT ORTHOSIS - STATIC ANALYSIS

An asymmetric 3-dimensional finite element model (FEM) of the ankle-fo ot orthosis (AFO) together with the ankle-foot complex was developed u sing the computer aided design (CAD) program PATRAN. Static analysis o f normal and pathological motions of the ankle-foot complex such as th e ''drop/bet'' problem were conducted using the FEM program ADINA. A t otal of 313 three dimensional solid elements and 10 truss elements wer e used. Heel strike and toe-off condition were simulated. Results reve aled that the peak compressive stress (1.6 MPa) in the AFO model occur red in the heel regions of the AFO and the maximum tensile stress (0.8 MPa) occurred in, the neck region of the AFO during toe-off Parametri c analyses revealed that the model was sensitive to the elastic moduli of the AFO and of the soft tissue, but was relatively insensitive to the ligament stiffness. The results confirmed the hypothesis that peak stresses in, the orthosis occur in the heal and neck regions of the o rthosis.