Bony ingrowth potential of 3D printed porous titanium alloy: a direct comparison of interbody cage materials in an in vivo ovine lumbar fusion model

Publication date: Available online 26 February 2018
Source:The Spine Journal
Author(s): Kirk McGilvray, Jeremiah Easley, Howard B. Seim, Daniel Regan, Sigurd H. Berven, Wellington K. Hsu, Thomas E. Mroz, Christian M. Puttlitz
Background ContextThere is significant variability in the materials commonly used for interbody cages in spine surgery. It is theorized that 3-D printed interbody cages utilizing porous titanium material can provide more consistent bone ingrowth and biological fixation.PurposeThe purpose of this study was to provide an evidence-based approach to decision making regarding interbody materials for spinal fusion.Study DesignComparative animal study.MethodsA skeletally mature ovine lumbar fusion model was utilized for this study. Interbody fusions were performed at (L2-L3 and L4-L5) in 27 mature sheep using three different interbody cages (i.e., polyetheretherketone [PEEK], plasma sprayed porous titanium coated PEEK [PSP], and 3-D printed porous titanium alloy cage [PTA]). Non-destructive kinematic testing was performed in the three primary directions of motion. The specimens were then analyzed using micro-computed tomography (µCT); quantitative measures of the bony fusion were performed. Histomorphometric analyses were also performed in the sagittal plane through the interbody device. Outcome parameters were compared between cage designs and time-points.ResultsFlexion-extension range of motion (ROM) was statistically reduced for the PTA group as compared to the PEEK cages at 16 weeks (p-value = 0.02). Only the PTA cages demonstrated a statistically significant decrease in ROM and increase in stiffness across all three loading directions between the 8-week and 16-week sacrifice time-points (p-value ≤ 0.01). Micro-CT data demonstrated significantly greater total bone volume within the graft window for the PTA cages at both 8-weeks and 16-weeks compared to the PEEK cages (p-value < 0.01).ConclusionsA direct comparison of interbody implants demonstrates significant and measurable differences in biomechanical, µCT, and histologic performance in an ovine model. The 3-D printed porous titanium interbody cage resulted in statistically significant reductions in ROM, increases in the bone ingrowth profile, as well as average construct stiffness compared to PEEK and PSP.



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