Study Design. Prospective, randomized, controlled preclinical study.Objective. The objective of this study was to compare the host inflammatory response of our previously described hyperelastic, 3D-printed (3DP) hydroxyapatite (HA)-demineralized bone matrix (DBM) composite scaffold to the response elicited with the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in a preclinical rat posterolateral lumbar fusion model. Summary of Background Data. Our group previously found that this 3D-printed HA-DBM composite material shows promise as a bone graft substitute in a preclinical rodent model, but its safety profile had yet to be assessed. Methods. Sixty female Sprague-Dawley rats underwent bilateral posterolateral intertransverse lumbar spinal fusion using with the following implants: 1) type I absorbable collagen sponge (ACS) alone; 2) 10 mg rhBMP-2/ACS; or 3) the 3DP HA-DBM composite scaffold (n ¼ 20). The host inflammatory response was assessed using magnetic resonance imaging, while the local and circulating cytokine expression levels were evaluated by enzyme-linked immunosorbent assays at subsequent postoperative time points (N ¼ 5/time point). Results. At both 2 and 5 days postoperatively, treatment with the HA-DBM scaffold produced significantly less soft tissue edema at the fusion bed site relative to rhBMP-2-treated animals as quantified on magnetic resonance imaging. At every postoperative time point evaluated, the level of soft tissue edema in HA-DBM-treated animals was comparable to that of the ACS control group. At 2 days postoperatively, serum concentrations of tumor necrosis factor-a and macrophage chemoattractant protein-1 were significantly elevated in the rhBMP-2 treatment group relative to ACS controls, whereas these cytokines were not elevated in the HA-DBM-treated animals. Conclusion. The 3D-printed HA-DBM composite induces a significantly reduced host inflammatory response in a preclinical spinal fusion model relative to rhBMP-2.
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