A tibial tray is part of an implant used for Total Knee Arthroplasty. The part above is attached to the shinbone and supports the upper part of the implant.
Typically, tibial trays are made from solid titanium, which exhibits higher tensile strength than the surrounding tibia bone. This is known to cause stress shielding and results in a decrease in bone density which is detrimental to the fit of the implant and to long-term knee replacement success.
Stress shielding can be prevented by encouraging bone intergrowth, which is known as osseointegration - the ‘direct structural and functional connection between living bone and the surface of a load-bearing artificial implant’.
This tibial tray implant has been created using Autodesk Within Medical and is an example of how simple the software has made the process of developing medical-grade Titanium implants featuring trabecular lattice that may aid osseointegration.
A wide distribution of pore sizes is thought to encourage a more secure fit, with larger pores favourable for stress transfer and smaller pores beneficial for initial fixation. Autodesk Within Medical gives designers the power to choose the pore size of the trabecular lattice and even vary the porosity throughout the implant.
A stable initial fixation of an implant secures the implant and allows for bony ingrowth. This is aided by a good “scratch fit” – a rough surface increases the cortical bone contact with the implant, scraping the walls of the tibial canal and filling the lattice pores with bone material. Autodesk Within Medical gives designers the power to choose from different levels of surface roughness.
As the implant was manufactured in a single phase using Direct Metal Laser Sintering there is structural continuity between solid and porous sections. The implant features modular stem extensions to optimise fixation and the entire contact surface is formed from trabecular lattice. Once removed from the build plate and cleaned, the part can be coated with a hydroxylapatite bioabsorbable filler to further stimulate bony ingrowth.