Optimization of 3D-titanium interbody cage design. Part 1: in vitro biomechanical study of subsidence

• Published in: The spine journal 2024-12
• Main Authors: Farber, S Harrison, Oldham, Alton J, O'Neill, Luke K, Sawa, Anna G U, Ratliff, Alexis C, Doomi, Ahmed, Pereira, Bernardo de Andrada, Uribe, Juan S, Kelly, Brian P, Turner, Jay D
• Format: Article
• Language: English
• ISSN: 1878-1632; 1878-1632
• DOI: 10.1016/j.spinee.2024.12.002

Cage subsidence is a complication of interbody fusion associated with poor clinical outcomes. 3D-printed titanium interbody cages allow for the alteration of features such as stiffness and porosity. However, the influence of these features on subsidence and their biological effects on fusion have not been rigorously evaluated. This 2-part study sought to determine how changes in 3D-printed titanium cage parameters affect subsidence using an in vitro bone model (Part 1) and biological fusion using an in vivo sheep model (Part 2). Biomechanical foam block model. In Part 1 of this study, 9 implant types were tested (8 per implant type). The implant types included 7 3D-printed titanium interbody cages with various surface areas, porosities, and surface topographies, along with 1 standard polyetherether ketone (PEEK) cage and 1 solid titanium cage. Subsidence testing was performed in a standardized foam block model using 2 different densities of foam. Digital imaging correlation was used to determine the relative vertical displacement of the interbody cage-foam block construct. Subsidence decreased as the surface contact area with the bone model increased (all p≤0.01). Increased porous surface topography increased subsidence, while a nonporous surface significantly decreased subsidence (all p