70. A biologically-inspired 3D-printed titanium alloy interbody spacer promotes osseointegration in an ovine lumbar interbody fusion model

Abstract

BACKGROUND CONTEXT Osseointegration of spinal implants is crucial to achieve long-term clinical success following interbody fusion surgery. Through advancements in 3D-printing technology, commonly used titanium-alloy (TAV) interbody spacers can now be designed with unique architectures, such as a highly interconnected and specific porous structure that mimics the architecture of trabecular bone. An interbody spacer with a microscale surface roughness and biomimetic porosity may improve bony ongrowth and ingrowth compared to traditional materials. Research has shown through in vivo animal models that 3D-printed porous implants encourage osseointegration in various orthopedic applications. However, data investigating osseointegration following spine interbody fusion using a biomimetic 3DP porous titanium spacer is lacking. PURPOSE The purpose of this study was to compare osseointegration of lumbar interbody fusion devices made from polyetheretherketone (PEEK), titanium-alloy (TAV), and 3D-printed biomimetic TAV (3DP) in a preclinical ovine model. STUDY DESIGN/SETTING In vivo animal study. PATIENT SAMPLE Not applicable. OUTCOME MEASURES Microcomputed tomography (microCT) and histomorphometric analyses were performed to quantify bone volume (BV) within the spacers (ingrowth) and total bone growth onto the surface of the spacer (ongrowth), respectively. BV was measured as the sum of the volume of bone in the central and both lateral graft windows. Bone ongrowth was assessed as the bone apposition ratio (BAR), the percent of the total length of the implant with direct bony contact on the interbody surface (linear apposition). METHODS Eighteen mature female sheep underwent two-level (L2–L3 and L4–L5) lateral interbody fusion using either a 3DP, PEEK or a TAV spacer (n=6 levels for each spacer per time point). Animals were sacrificed at 6 and 12 weeks post operatively. BV and BAR were evaluated at the two postoperative time points. RESULTS The 3DP-treated group demonstrated significantly higher BV than PEEK and TAV groups at 6 weeks postoperatively (177.3±44.1 mm3, 116.9±43.0 mm3, and 108.7±15.2 mm3, respectively) (p 0.05). BV significantly increased for all groups from the 6- to 12-week time point (p CONCLUSIONS Osseointegration is a pivotal process in achieving a rigid fusion and ultimately a successful clinical outcome following interbody fusion surgery. This study demonstrated that 3DP porous, biomimetic spacers facilitated greater total bony ingrowth at 6 weeks and greater bony ongrowth at both 6 and 12 weeks postoperative compared to PEEK and TAV interbody spacers. Therefore, 3DP spacers promote robust osseointegration, as evidenced by increased bony ongrowth and equivalent bone volume compared to PEEK and TAV at 12 weeks postoperative. FDA DEVICE/DRUG STATUS HEDRON (Globus Medical) (Approved for this indication)