Material Removal of Hip Stem Prosthesis Using Bio-Inspiration from Trabecular Bone

Abstract

In the hip stem prostheses domain, stress shielding represents a major issue due to its potential implant loosening effect. This phenomenon occurs when the implant is much stiffer than the bone itself. A way to reduce this stiffness difference is to remove material from the implant. In addition, this solution leads to mass reduction of the implant, improving the patient quality of life. To insure the implant will withstand the loading, material must be distributed in a specific way. Bones use the same objectives of lightness and mechanical efficiency while using a minimal amount of material. In addition, these biological structures are well spread and reliable in living beings, especially in mammals and avian species. In this paper, a method bio-inspired by trabecular bone structure is proposed to remove material from parts considering their mechanical stress field. In Nature, trabecular bone is defined as a graded porous material with bone material locally oriented along the local stresses’ direction. To mimic this natural behavior, the proposed method generates local porosities bio-inspired in position, shape, size and orientation. To evaluate the proposed method performance, experimental tests were carried out on a hip prosthesis stem. Test results demonstrated that the method can be used to reduce the stiffness of the prosthesis while withstanding the applied constrains.