Design and Additive Manufacturing of Acetabular Implant with Continuously Graded Porosity

Abstract

Porous structured metallic implants are preferable as bone graft substitutes due to their faster tissue integration mediated by bone in-growth and vascularization. The porous scaffolds/implants should also mimic the graded structure of natural bone to ensure a match of mechanical properties. This article presents a method for designing a graded porous structured acetabular implant and identifies suitable parameters for manufacturing the model through additive manufacturing. The design method is based on slice-wise modification to ensure continuity of gradation. Modification of the slices was achieved through the binary image processing route. A geodesic dome-type design was adopted for developing the acetabular cup model from the graded porous structure. The model had a solid shell with the target porosity and pore size gradually changing from 65% and 950 µm, respectively, in the inner side to 75% and 650 µm, respectively, towards the periphery. The required dimensions of the unit structures and the combinations of pore structure and strut diameter necessary to obtain the target porosity and pore size were determined analytically. Suitable process parameters were identified to manufacture the model by Direct Metal Laser Sintering (DMLS) using Ti6Al4V powder after carrying out a detailed experimental study to minimize the variation of surface roughness and warping over different build angles of the strut structures. Dual-contour scanning was implemented to simplify the scan strategy. The minimum diameter of struts that could be manufactured using the selected scanning strategy and scanning parameters was found to be 375 µm. Finally, the model was built and from the micro-CT data, the porosities and pore sizes were found to be closely conforming to the designed values. The stiffness of the structures, as found from compression testing, was also found to match with that of human trabecular bone well. Further, the structure exhibited compliant bending-dominated behaviour under compressive loading.

Resorbable GBR Scaffolds in Oral and Maxillofacial Tissue Engineering: Design, Fabrication, and Applications

“…In addition to TPMS, a number of additional cutting-edge design methods for scaffolds have surfaced. The solid isotropic material with penalization (SIMP) approach, the Voronoi method, machine learning (ML), genetic algorithm (GA), and AM method (e.g., direct metal laser sintering) are a few of these techniques [157][158][159].…”

“…However, more study is required to determine its effect on clinical applications [159]. A method for designing graded porous structured acetabular implants was presented by Mukherjee et al [158] along with parameters that could be used to create models using AM (direct metal laser sintering). In order to maintain gradation continuity, this design method relied on slice-wise modifications, and it used a geodesic dome-type design to create the acetabular cup model.…”

“…Additionally, the stiffness, compression testing, and compliant bending-dominated behaviour of the structures closely matched the characteristics of human trabecular bone. Finally, the authors suggested that the best implant design may require site-specific bone in-growth studies [158].…”

Titanium Alloy Implants with Lattice Structures for Mandibular Reconstruction

“…In topology-optimized FGP designs, the density of the lattice structure is set to match spatial variation in the mechanical properties of bone [ 143 , 146 ]. In both cases, the gradient within FGP designs is ideally continuous to simulate the complex features of bone structure and its mechanical properties [ 147 ].…”

The Porosity Design and Deformation Behavior Analysis of Additively Manufactured Bone Scaffolds through Finite Element Modelling and Mechanical Property Investigations

“…These scaffolds leverage TPMS designs, known for their exceptional surface area and customizable porosities. This geometric complexity influences the scaffold's mechanical behavior, making TPMS-based constructs highly promising for applications where specific mechanical responses, such as flexibility or compressibility, play a crucial role in advancing bone tissue engineering [4]. Conventional manufacturing techniques, including electrospinning, particle leaching, freeze drying, solvent casting, and gas foaming, can be employed to develop synthetic bone scaffolds.…”