Design of a biomimetic polymer‐composite hip prosthesis

Abstract

A new biomimetic composite hip prosthesis (stem) was designed to obtain properties similar to those of the contiguous bone, in particular stiffness, to allow normal loading of the surrounding femoral bone. This normal loading would reduce excessive stress shielding, known to result in bone loss, and micromotions at the bone-implant interface, leading to aseptic prosthetic loosening. The design proposed is based on a hollow substructure made of hydroxyapatite-coated, continuous carbon fiber (CF) reinforced polyamide 12 (PA12) composite with an internal soft polymer-based core. Different composite configurations were studied to match the properties of host tissue. Nonlinear three-dimensional analysis of the hip prosthesis was carried out using a three-dimensional finite element bone model based on the composite femur. The performance of composite-based hip and titanium alloybased (Ti-6Al-4V) stems embedded into femoral bone was compared. The effect of core stiffness and ply configuration was also analyzed. Results show that stresses in composite stem are lower than those in Ti stem, and that the femoral bone implanted with composite structure sustains more load than the one implanted with Ti stem. Micromotions in the composite stem are significantly smaller than those in Ti stem over the entire bone-implant surface because of the favorable interfacial stress distribution.

Numerical modeling of acetabular reconstruction cages made of composite material and estimation of mechanical behavior for bone and cage

“…股関節は人体において体重を支える役割を有し，歩行時などにおいて体内の関節に作用する荷重による負担の 最も大きい部位である．したがって，股関節疾患は社会活動や日常生活に深刻な問題を及ぼす．近年の高齢化の 進行に伴い，骨や股関節における疾患は増加が予想されており，1990 年には 150 万人程度であった股関節疾患患 者数は，2025 年までに 300 万人を超えると予想されている (Cooper, et al, 1992) (Delaunay, et al, 2010) )．また，X 線を散乱するために画像診断が困難で あることに加え (Cutler, et al, 2007)， CF/PEEK についての生 体適合性 に関する 障害は なく，耐 腐食性や耐薬品 性にも優 れている ) (Fujihara, et al, 2004)．さらに，CFRP の有する様々な設計パラメータを用いることで，患者に最適なテー ラーメード人工股関節の開発が可能となる．したがって，寛骨臼サポートコンポーネントの形状，積層構成等の 設計パラメータが股関節における力学的挙動に及ぼす影響を数値解析により評価することは，寛骨臼サポートコ ンポーネントの設計に非常に有用であると考える．ステムやカップについては，数値解析を用いた研究成果が多 数報告されている (Bougherara, et al, 2007)(Dopico-González, et al,2010) (Hedia, et al, 2005) ) Okazaki, Kurashiki, Hanaki, Mukoyama, Li, Sugano, Uemura and Bandoh, Transactions of the JSME (in Japanese), Vol.81, No.826 (2015) (a) x-y plane (b) x-z plane -isotropic), the cortical bone restrained deformation of the flange. But, in case of Ti-6Al-4V, the flange deformed the cortical bone.…”

Performance of CF/PA12 composite femoral stems

“…The THP stem is typical of modular designs that are implanted by press-fitting into the contiguous bone without the use of an acrylic bone cement anchor. The stem is straight, follows the natural curve of the femoral bone, has an oval crosssection, and a shaft angle of 135° [3]. A PA12/CF reinforced composite in the form of braided sleeves of commingled fibers of PA12 and carbon was used in this study.…”

“…This phenomenon is known as ''stress shielding'' and is frequently seen with metallic implants. In addition, this stress shielding might contribute to the stress concentration at the bone-implant interface that lead to micromotions, as recently indicated by a finite element simulation study of total hip prosthesis (THP) stems [3]. To date, it has not been demonstrated that stress shielding is not a factor in the prevalence of bone-implant interface weakening.…”

Comparison of Mechanical Properties between Carbon/PEEK Composites and Ti Stem for Optimal Design

“…Therefore, the development of a patient-customized artificial hip joint is urgently required in order to improve its useful life. [7,8] International Journal of Ocean System Engineering 3 (3) (2013) [152][153][154][155][156][157] In this study, carbon/PEEK composites are designed to prevent stress concentration from the difference in rigidity and to improve mechanical properties. Two types of patient-customized artificial hip joint stems are designed using a 3D design program.…”