(7) It is assumed that the bone exhibits an idealized stress–strain curve consisting of a linearly elastic phase followed by a plastic phase where the stress in the plastic phase is constant. It is further assumed that the displacement of the implant surface in relation to the interface bone is so big at fracture that the deformation of the bone, immediately adjacent to the
implant surface, lies in the plastic region of the stress–strain curve irrespective of slope angle a. The deformation of the rest of the bone is assumed to lie in the linearly elastic region.