The “Snowshoe” Effect
4WEB’s Jessee Hunt also mentioned something to us that kind stuck. And that is this idea of a “snowshoe” effect their 3D printed implants have.
“If you think about the top and bottom web structure of the 4WEB implant we have a web structure that spans across the entire bone interface in contrast to ring-shaped implants that have concentrated amounts of material around the rim. Our bone interface web structure distributes load over a larger surface area and essentially behaves like a snowshoe. This helps to prevent the implant from sinking into the adjacent bone and reduces the chance of subsidence.”
“It’s really exciting that we can engineer an implant that can withstand the significant strain that the human body can have on an implant, have that implant participate and accelerate the healing process, knowing that these implants mostly of air. The truss design allows for a minimal amount of structural material with an optimal amount of strength. In some designs only 25% of the implant volume is titanium and the rest is open space for graft material and bone to grow.”
How well do 3D implants handle the loads in the spine?
According to Hunt, the Truss Implant TechnologyTM, which is the foundation of the 4WEB family of implants, is “based on a triangular unit cell that is not susceptible to shear failure. When you load a triangle-based space truss the geometry resists that load no matter what direction the load is coming from. If you look at the more generic micro lattice structures that are in the market, they’re mostly rectangular or square based unit cells. If you have a square and you apply load to one of its corners, the square will collapse. It’s about the efficiency of the geometric unit cell.”
“Truss structures and truss technology are at the core of almost every building, bridge and highway that exists. When done right structures designed with these well-established engineering principles are extremely reliable and efficient. Due to advances in additive manufacturing we can now apply structural engineering principles such as truss design to the human body for the first time.”
Bottom Line
Five years ago, perhaps longer, the conventional wisdom among orthopedic spine surgeons and neurosurgeons was that advanced biologics, living cell implants for example, would be the next generation of osteoinductive implants.
And several of those did, indeed, come to market.
Today however, focus appears to be less on biologics and more on creating novel, open architecture implants with surface features that create a bioactive response which can be amplified through a mechanobiologic mechanism … essentially putting Wolff’s Law to work.
This, ultimately, may well prove to be a more cost effective, simpler strategy that drives the healing process towards successful fusion surgeries.
