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

BACKGROUND CONTEXT: 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. PURPOSE: 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. STUDY DESIGN: 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). Post-operative 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. RESULTS: The 3DP-treatment group demonstrated significantly higher BV than the PEEK and TAV groups at 6 weeks (77.3 +/- 44.1 mm(3), 116.9 +/- 43.0 mm(3), and 108.7 +/- 15.2 mm(3), 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). CONCLUSIONS: 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. CLINICAL SIGNIFICANCE: 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. (C) 2021 Published by Elsevier Inc.