• Ethan Cottrill, Christian J Rajkovic, Jessica Lin, Mahnoor Shafi, Jovanna A Tracz, Vaughn Hernandez, Farhad Parhami, and Timothy F Witham.
• The Spinal Fusion Laboratory, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Orthopedic Surgery, Duke University School of Medicine, Durham, North Carolina, USA. Electronic address: ethan.cottrill@duke.edu.
• World Neurosurg. 2024 Dec 7.

ObjectiveTo (1) create a novel tissue-engineered bone graft comprising the osteoinductive oxysterol Oxy133 and (2) compare the osteogenic capability of this novel bone graft with bone graft substitutes previously examined.MethodsOxy133 was homogeneously incorporated into a biomimetic bone graft substitute (BioMim) comprising extracellular matrix and calcium phosphates. Two iterations of the graft were created: one corresponding to an implant-dose of 2.0mg Oxy133 (BioMim-Oxy133-Lo) and the other corresponding to an implant-dose of 20mg Oxy133 (BioMim-Oxy133-Hi). Thirty-two male Sprague Dawley rats were allocated randomly to four equally sized groups: 1) BioMim-Oxy133-Lo, 2) BioMim-Oxy133-Hi, 3) absorbable collagen sponge (ACS) with topically applied Oxy133 dissolved in dimethyl sulfoxide (ACS-Oxy133; 20mg Oxy133/graft), and 4) ACS with topically applied rhBMP-2 dissolved in water (ACS-rhBMP-2; 5.0μg rhBMP-2/graft). All animals underwent L4-L5 posterolateral spinal fusion. Spines were harvested 8 weeks postoperatively and analyzed using micro-CT imaging.ResultsSuccessful fusion was achieved in all animals. Grafts containing Oxy133 had significantly greater bone volume, percentage bone volume (%BV), bone surface density (BSD), and trabecular number (TbN) compared to ACS-rhBMP-2 (p<0.01 for each). Animals treated with BioMim-Oxy133-Lo had the greatest %BV, BSD, and TbN (p<0.001 for each), whereas animals treated with ACS-rhBMP-2 had the lowest %BV, BSD, TbN, and trabecular thickness (p<0.001 for each).ConclusionsBioMim-Oxy133 is a novel bone graft that led to superior bone volume and quality compared to ACS-rhBMP-2 in a clinically translatable rat model of spinal fusion. Future work is needed to further evaluate this material as a safe and efficacious bone graft substitute.Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.

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