3D-Printed Metallic Lattice Scaffolds for Orthopedic Bone Reconstruction

Reconstruction of large or load-bearing bone defects is a longstanding clinical challenge due to complications such as bone resorption and aseptic loosening. Those complications accrue due to “stress shielding” phenomena (the implant is stiffer than the natural bone, and bone cells that do not have adequate stress stimulation will die). Designing lattice structure scaffolds using additive manufacturing (AM) technology may provide new solutions to this tremendous clinical challenge. Lattice structure is a porous structure composed of periodical 3D cellular units that can be optimized for specific functional requirements with a larger degree of control over certain characteristics. Since AM has given lattice structures new levels of accessibility, we can design scaffolds with complex lattice structures according to patient-specific anatomy (taken from CT and/or MRI imaging). Lattice structures are able to offer an increased potential of osseointegration by enhancing cell ongrowth and ingrowth into the pore spaces, which is vital for an efficient long-term biological fixation. Additionally, for biocompatible metals implants, such as titanium and stainless steel, those structures reduce the stiffness of the scaffolds to a better match of the surrounding bone tissue and lower the prevalence of stress shielding. In an attempt to determine the lattice structure optimized for osseointegration, many studies have examined how those structures influence osseointegration with varying results. Nevertheless, further research is required to determine the optimal lattice shape, size, and porosity for osseointegration and implant performance. This study aims to develop functional bone scaffolds with an optimal combination of high strength and osteointegration capability for adequate healing in load-bearing bone defects. The scaffolds based on 316L stainless steel with different lattice structures were fabricated and characterized to locally mimic bone tissue properties using additive manufacturing technology. A wide range of biomechanical and osteointegration tests were conducted on the different lattice scaffolds, such as tensile, compression, and fatigue tests, as well as in vitro analysis.