title: Three-dimensional shape optimization of a cemented hip stem and experimental validations.
abstract: This study proposes novel optimized stem geometry with low stress values in the cement using a finite element (FE) analysis combined with an optimization procedure and experimental measurements of cement stress in vitro. We first optimized an existing stem geometry using a three-dimensional FE analysis combined with a shape optimization technique. One of the most important factors in the cemented stem design is to reduce stress in the cement. Hence, in the optimization study, we minimized the largest tensile principal stress in the cement mantle under a physiological loading condition by changing the stem geometry. As the next step, the optimized stem and the existing stem were manufactured to validate the usefulness of the numerical models and the results of the optimization in vitro. In the experimental study, strain gauges were embedded in the cement mantle to measure the strain in the cement mantle adjacent to the stems. The overall trend of the experimental study was in good agreement with the results of the numerical study, and we were able to reduce the largest stress by more than 50% in both shape optimization and strain gauge measurements. Thus, we could validate the usefulness of the numerical models and the results of the optimization using the experimental models. The optimization employed in this study is a useful approach for developing new stem designs.
authors.affiliation: Mechanical Engineering, University of Hyogo, Shosha 21267, Himeji, Hyogo, 671-2280, Japan, higa@eng.u-hyogo.ac.jp.
authors.forename: Masaru
authors.initials: M
authors.lastname: Higa
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Tanino
authors.forename: Ikuya
authors.initials: I
authors.lastname: Nishimura
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Mitamura
authors.forename: Takeo
authors.initials: T
authors.lastname: Matsuno
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ito
mesh_terms: D001843:Bone Cements; D003198:Computer Simulation; D006622:Hip Prosthesis; D006801:Humans; D008422:Materials Testing; D008953:Models, Anatomic; D008962:Models, Theoretical; D011474:Prosthesis Design; D013314:Stress, Mechanical
chemical_list: D001843:Bone Cements