Significance of cancellous bone orthotropy and non-homogeneity in femoral head

conference paper

English

The influence of cancellous bone orthotropy and non-homogeneity on the stress-strain states in a femoral head and on the contact pressure distribution between the head and acetabulum is investigated. The FE model created in program system ANSYS is based on an idealized 3D geometry of the femoral head and acetabulum under axial load (in the axis of the femoral neck). The cancellous bone inside the femoral head is divided into several (15-22) regions in which local orthotropic or isotropic linear elastic properties are prescribed. The values of moduli of elasticity in tension in all the three perpendicular directions were taken from literature. However, no more elastic constants have been found there. Therefore the other six elastic constants necessary for the orthotropic material (three Poisson's ratios and three shear moduli) have been calculated from the known values valid for isotropic constitutive model of cancellous bone using formulas based on some reasonable simplifications, and they have been checked to meet all the limitations valid for orthotropic elastic parameters. Cortical bone and cartilage in the hip joint have been modelled as linear elastic isotropic materials. It was not verified whether or not the directions in which the elastic moduli had been measured (anterior-posterior, medial-lateral, proximal-distal) on the bones of large dogs are really their principal material directions. The results show that the stress state in the cancellous bone itself depends strongly on its orthotropy and even more on its non-homogeneity. Their influence on the stress distribution in the cortical bone is much lower, and there is nearly no influence on the contact pressure distribution between the head and acetabulum. It can be stated that for computational modelling of contact pressure distribution the non-homogeneity and orthotropy of the cancellous bone are not significant.

Cancellous bone, femoral head, orthotropy, non-homogeneity

BURŠA, J.; KUŽELA, P.

2006

29. 7. 2006

European Society of Biomechanics

Munich, Germany

CD

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