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fibrous capsules , osteolysis or barely detectable traces of wear debris on or around interbody implants instead of integrating with the surrounding bone .
In addition to using osteoconductive or inductive bone void fills , the other early strategies were to coat or bind thin layers of various metals or osteoinductive ceramics such as hydroxyapatite , titanium , gold , titanium dioxide , diamond-like carbon , or even tert-butoxides to the implant ’ s surface . And those strategies worked to a certain extent .
The most common of these bioactive coatings was hydroxyapatite — which is well known and well characterized .
The other strategy was to create a rough nanometer surface which , again , was able to demonstrate improved bony fusion . Titanium and gold coatings were also able to promote osteoblast adhesion on the implant .
But , as studies have demonstrated , these coatings have trade-offs — their modulus of elasticity , for example , can range from 10 GPa to 100 GPa ( compared to 1.0 – 2.4 GPa in cortical bone ), depending on the density of the coat .
Better Osseointegration ( Fusion ) Through Structure ?
3D printing has unleashed a flood of creative implant design energy — struts , curves , arches — and opened the implant real estate for more bone graft material . As 3D printing changed the geometries of each implant , they also altered the implant ’ s biomechanics . Change biomechanics , change osseointegration ?
If you ’ re a fan of chemistry over structure and your tools of the trade include , for example , hydroxyapatite , surface modification or other chemical interface , you may think all these new designs are fine , but they ’ re just suspenders , while you still rely on chemistry to be your “ belt ” in this analogy .
In a 2022 review and analysis of spinal implant osseointegration and the role of 3D printing which was published in the Journal of Bioengineering by authors Kia , Antonacci , Wellington , Makanji , and Esmende wrote : “ 3D printed implants have come into the market , providing mechanical stability with increased surface design for bony ingrowth . While clinical outcomes studies are limited ,
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