Comparison of 3D-printed titanium-alloy, standard titanium-alloy, and PEEK interbody spacers in an ovine model

Osseointegration is a pivotal process in achieving a rigid fusion and ultimately a successful clinical outcome following interbody fusion surgery. Advancements in 3D printing technology permit commonly used titanium interbody spacers to be designed with unique architectures, such as a highly interconnected and specific porous structure that mimics the architecture of trabecular bone. Interbody implants with a microscale surface roughness and biomimetic porosity may improve bony ongrowth and ingrowth compared to traditional materials.The purpose of this study was to compare the osseointegration of lumbar interbody fusion devices composed of surgical-grade polyetheretherketone (PEEK), titanium-alloy (TAV), and 3D-printed porous, biomimetic TAV (3DP) using an in vivo ovine model.In Vivo Preclinical Animal Study METHODS: Eighteen sheep underwent two-level lateral lumbar interbody fusion randomized with either 3DP, PEEK, or TAV interbody spacers (n=6 levels for each spacer per time point). Postoperative time points were 6 and 12 weeks. Microcomputed tomography and histomorphometry were used to quantify bone volume (BV) within the spacers (ingrowth) and the surface bone apposition ratio (BAR) (ongrowth), respectively.The 3DP-treatment group demonstrated significantly higher BV than the PEEK and TAV groups at 6 weeks (77.3±44.1 mm3, 116.9±43.0 mm3, and 108.7±15.2 mm3, respectively) (p<.05). At 12 weeks, there were no BV differences between groups (p>.05). BV increased in all groups from the 6- to 12-week time points (p<.05). At both time points, the 3DP-treated group (6w: 23.6±10.9%; 12w: 36.5±10.9%) had significantly greater BAR than the PEEK (6w: 8.6±2.1%; 12w: 14.0±5.0%) and TAV (6w: 6.0±5.7%; 12w: 4.1±3.3%) groups (p<.05).3DP interbody spacers facilitated greater total bony ingrowth at 6 weeks, and greater bony ongrowth postoperatively at both 6 and 12 weeks, in comparison to solid PEEK and TAV implants.Based on these findings, the 3DP spacers may be a reasonable alternative to traditional PEEK and TAV spacers in various clinical applications of interbody fusion.