Mechanical and in vitro biological properties of uniform and graded Cobalt‐chrome lattice structures in orthopedic implants

Abstract

Human bones are biological examples of functionally graded lattice capable to withstand large in vivo loading and allowing optimal stress distribution. Disruption of bone integrity may require biocompatible implants capable to restore the original bone structure and properties. This study aimed at comparing mechanical properties and biological behavior in vitro of uniform (POR-FIX) and graded (POR-VAR) Cobaltchrome alloy lattice structures manufactured via Selective Laser Melting. In compression, the POR-VAR equivalent maximum stress was about 2.5 times lower than that of the POR-FIX. According to the DIC analysis, the graded lattice structures showed a stratified deformation associated to unit cells variation. At each timepoint, osteoblast cells were observed to colonize the surface and the first layer of both scaffolds.Cell activity was always significantly higher in the POR-VAR (p < 0.0005). In terms of gene expression, the OPG/RANKL ratio increased significantly over time (p < 0.0005) whereas IL1β and COX2 significantly decreased (7 day vs 1 day; p < 0.0005) in both scaffolds. Both uniform-and graded-porosity scaffolds provided a suitable environment for osteoblasts colonization and proliferation, but graded structures seem to represent a better solution to improve stress distribution between implant and bone of orthopedic implants.

Active Materials for 3D Printing in Small Animals: Current Modalities and Future Directions for Orthopedic Applications

“…The material of cobalt alloys is tough, and the surface chromium oxide layer provides corrosion resistance. Nevertheless, because of its hardness, creating complex shapes and its machining are challenging [21,22]. Commercial titanium is highly biocompatible and corrosion resistant; however, it lacks sufficient mechanical strength.…”

“…Various in vitro studies have shown the potential application of 3D-printed scaffolds in BTE [6,22,27,33]. CaP ceramics and bioactive glasses are introduced as promising osteoinductive and osteoconductive substitutes for large orthopedic defect remolding or regeneration [4,6,69,70].…”

Selective laser melting: lessons from medical devices industry and other applications

“…Cobalt-based alloys Some Co-Cr based alloys are the most preferred metallic biomaterials in orthopedic applications, especially in hip prostheses and dental applications (e.g. CoCrMo, CoCr, CoCrCu and CoCrW), for that reason, all the improvements on its mechanical performance are justified (AlMangour et al, 2020;Dobrza nski et al, 2020;Lu, 2017;Pagani et al, 2021;Uzun, 2019). A personalized femoral component of CoCrMo (CCM) with good exterior quality, mechanical property and biological corrosion resistance, obtained by the SLM process, was the achievement of the work proposed by Song (2016).…”

Stiffness prediction and deformation analysis of Cobalt-Chromium lattice structures: From periodic to functionally graded structures produced by additive manufacturing

“…No attempt was made to explore the effects of varying process parameters beyond those described in a previous work [15], summarized in Table 1. A 3 × 3 mm chessboard scanning strategy was used for hatching.…”

“…Lattice structures have also been successfully applied to the fabrication of biomedical devices to enhance osseointegration and/or to reduce stress shielding phenomena [14][15][16][17].…”