Friday, September 28, 2018 4:05 PM–5:05 PM abstracts: basic science of spinal fusion: 236. Composition of hyperelastic bone composite scaffolds affects de novo bone formation

Abstract

BACKGROUND CONTEXT Bone graft extenders for spine fusion include demineralized bone matrix (DBM) and ceramic-based products, but their efficacy is insufficient to qualify them as bona fide bone graft substitutes (BGS). We previously developed a unique 3D-printable scaffold composed of synthetic hydroxyapatite particles (HA) and poly lactic-co-glycolic acid (PLGA). PURPOSE The purpose of this study is to improve the efficacy of this hyperelastic “bone” composite (HBC) by incorporating osteoinductive DBM particles. We evaluated the ability of various iterations of these HA-DBM HBC scaffolds to promote bone regeneration and spine fusion in a rat posterolateral spine fusion (PLF) model. METHODS Female Sprague Dawley rats underwent L4-L5 PLF utilizing HBC scaffolds composed of 30vol.% PLGA and a 70vol.% particles. For each group, the particle components consisted of the following vol.% ratios of HA:DBM: 1:0, 3:1, 1:1, 1:3, and 0:1. Eight weeks postoperative, spine fusion was evaluated via radiography and manual palpation. Synchrotron microCT was used to qualitatively assess bone formation within the struts of the scaffolds. Histology (Hematoxylin/Orange G/Alcian Blue and Masson's Trichrome) was used to characterize the bone growing within and around the struts and the bone-scaffold interface. RESULTS 3:1 HA:DBM HBC scaffolds had the highest fusion rate (92%), although this was only significantly higher than the 0:1 group (42% fusion; p CONCLUSIONS This study evaluated the use of 3D printed HBC scaffolds containing both HA and DBM particles as a potential BGS. Varying the proportions of HA:DBM within each scaffold resulted in only slight differences in fusion scores and rates. However, microCT showed that de novo bone spicule formation was only present within scaffold struts that contained DBM particles. We hypothesize that (1) the presence of osteoinductive DBM is key to de novo bone formation, and (2) the hydroxyapatite provides the calcium and phosphate necessary to re-mineralize the DBM particles. Future studies will aim to further improve the efficacy of this HBC as a BGS for spine fusion.