Three-dimensional printing and porous metallic surfaces: A new orthopedic application

Abstract

As-cast, porous surfaced CoCr implants were tested for bone interfacial shear strength in a canine transcortical model. Three-dimensional printing (3DP) was used to create complex molds with a dimensional resolution of 175 microm. 3DP is a solid freeform fabrication technique that can generate ceramic pieces by printing binder onto a bed of ceramic powder. A printhead is rastered across the powder, building a monolithic mold, layer by layer. Using these 3DP molds, surfaces can be textured "as-cast," eliminating the need for additional processing as with commercially available sintered beads or wire mesh surfaces. Three experimental textures were fabricated, each consisting of a surface layer and deep layer with distinct individual porosities. The surface layer ranged from a porosity of 38% (Surface Y) to 67% (Surface Z), whereas the deep layer ranged from 39% (Surface Z) to 63% (Surface Y). An intermediate texture was fabricated that consisted of 43% porosity in both surface and deep layers (Surface X). Control surfaces were commercial sintered beaded coatings with a nominal porosity of 37%. A well-documented canine transcortical implant model was utilized to evaluate these experimental surfaces. In this model, five cylindrical implants were placed in transverse bicortical defects in each femur of purpose bred coonhounds. A Latin Square technique was used to randomize the experimental implants left to right and proximal to distal within a given animal and among animals. Each experimental site was paired with a porous coated control site located at the same level in the contralateral limb. Thus, for each of the three time periods (6, 12, and 26 weeks) five dogs were utilized, yielding a total of 24 experimental sites and 24 matched pair control sites. At each time period, mechanical push-out tests were used to evaluate interfacial shear strength. Other specimens were subjected to histomorphometric analysis. Macrotexture Z, with the highest surface porosity, failed at a significantly higher shear stress (p = 0.05) than the porous coated controls at 26 weeks. It is postulated that an increased volume of ingrown bone, resulting from a combination of high surface porosity and a high percentage of ingrowth, was responsible for the observed improvement in strength. Macrotextures X and Y also had significantly greater bone ingrowth than the controls (p = 0.05 at 26 weeks), and displayed, on average, greater interfacial shear strengths than controls, although they were not statistically significant.

Three-dimensional growth of differentiating MC3T3-E1 pre-osteoblasts on porous titanium scaffolds

“…Fabrication technologies include chemical vapour infiltration to deposit tantalum onto vitreous carbon foams [7,8], solid freeform fabrication [9], self-propagating hightemperature synthesis [10], and powder metallurgy [2]. While these porous metals have been successful at encouraging bone ingrowth both in vivo and in clinical trials, the range of materials and microstructures available is still rather limited.…”

Developing an Integrated Computational Environment for the Detailed Design of a Mixing Impeller

“…11 But as the quality that these machines produced improved and the products are no longer limited to rough prototypes but now include finished products. One area that has seen rapid expansion in the use of digital manufacturing has been the medical community producing customized devices such as dental implants, 12 orthopedic limbs 13 and hearing aids 10 that fit each patients physiology. Furthering this digital manufacturing has been used to produce biological products such as ears 14 or skin.…”

Formation of New Bone with Preferentially Oriented Biological Apatite Crystals Using a Novel Cylindrical Implant Containing Anisotropic Open Pores Fabricated by the Electron Beam Melting (EBM) Method

“…Takayoshi NAKANO, 1) Wataru FUJITANI, 1) Takuya ISHIMOTO, 1) Jee-Wook LEE, 1) Naoko IKEO, 2) Hidetsugu FUKUDA 3) and Kouichi KURAMOTO 3) 1) Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 Japan. E-mail: nakano@mat.eng.osaka-u.ac.jp 2) Graduate Student, Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871 Japan.…”

“…Materials are produced in crosssectional layers using a three-dimensional (3D) computer model. 1,2) Even when metal powder is utilized as a starting material, the use of an electron beam as a heat source for melting the powder facilitates rapid fabrication of laminated structures layer by layer. The use of an electron beam also facilitates control of the pore size, shape, distribution, and porosity during the fabrication of porous materials.…”