The effect of soft tissues on dynamical behavior of bovine tibia using modal analysis

The dynamical behavior and vibrational characteristics of bone and the attached soft tissues, such as natural frequencies are widely used in therapeutic vibrations including the detection of the pain threshold and tissue damage, fracture healing and bone remodeling, and design of implants. Most of studies, have focused on either bone or the soft tissues to investigate the final effects of these treatments. In the present research the vibrational characteristics of combined bone-soft tissues are studied. For this purpose, the bovine tibia and its attached muscles and tendons have been targeted. The experimental results of modal tests were collected and compared with a three-dimensional finite element analysis. Bone was modeled as an inhomogeneous isotropic material. The model includes bone marrow as an isotropic homogeneous material and the attached soft tissues as an incompressible hyperelastic isotropic material. It was found that the inhomogeneity bone and considering bone marrow does not enhance much the model results. The effect of soft tissues on the natural frequencies has shown a reduction of 12% in the first two transverse modes and up to 70% in higher modes. The stiffening effect of soft tissue (due to large deformation) on the as natural frequencies was also investigated. An increase of up to 70% (at some frequencies) was observed in larger deformations.