J. L. Van Eps1,4, J. S. Fernandez-Moure1,4, F. J. Cabrera4, S. J. Minardi4,5, B. Aghdasi2,4, A. Tampieri4,5, E. Tasciotti4, B. K. Weiner2,3,4 1Houston Methodist Hospital,Department Of Surgery,Houston, TX, USA 2Houston Methodist Hospital,Department Of Orthopedics & Sports Medicine,Houston, TX, USA 3Weill Cornell Medical College,New York, NY, USA 4Houston Methodist Research Institute,Department Of Nanomedicine, Surgical Advanced Technology Lab,Houston, TX, USA 5Istituto Di Scienza E Tecnologia Dei Materiali Ceramici (ISTEC),Department Of Bio-Ceramic And Bio-Hybrid Composites,Faenza, FAENZA, Italy
Introduction:
With increased implementation of spinal instrumentation and fusion, an emphasis to develop biologic alternatives to the morbidity of autografting or prosthetic implants has emerged. Additionally, existing platforms utilizing bone morphogenic proteins (BMPs) are limited by potential side effects and alternatives are needed. Autologous platelet-rich plasma (PRP) is a universally-available source of growth factors with currently untapped potential for bone regeneration.
Methods:
A proprietary magnesium-hydroxyapatite/collagen 70/30 wt% composite scaffold was implanted in sixteen New Zealand White rabbits randomly assigned to two experimental groups undergoing L5-L6 intertransverse posterior spinal fusion – scaffold alone (S1) or scaffold + PRP (S2). Autologous PRP was isolated preoperatively for S2 rabbits via double-centrifugation of whole blood (8mL), standardized platelet concentration to 5×106/mL and activation with a solution of 10%CaCl and 300U thrombin, and used to soak scaffolds pre-implantation. The left anatomic side received decortication alone, serving as an internal control (IC). DynaCT imaging and post hoc bone volume quantification was performed at 2, 4, and 6 weeks postoperatively, and differences in experimental side/IC bone volume were compared using thresholds of 200 and 500 Hounsfield units (HU) – known correlates to trabecular and cortical bone respectively. Postoperative specimens were harvested, plastic embedded and sectioned, H&E stained, and visualized under microscopy to confirm fusion of new and native bone.
Results:
Both groups displayed significantly more osteogenesis on the experimental side compared to IC (p<0.05), confirming scaffold osteoconductivity, and earlier, more robust osteogenesis was seen in S2 vs. S1 rabbits by dynaCT imaging and volumetric analysis (Figure 1). This trend for trabecular bone formation was witnessed as early as 2 weeks (p<0.05) and became more pronounced at 4-6 weeks (p<0.01). The near 2-fold greater trabecular bone formation translated into more mature bone formation at 6 weeks as well, as Group S2 rabbits displayed significantly more cortical bone at 4 and 6 weeks postoperatively (p<0.05). Histological analysis confirmed more robust fusion of native and new bone and bridging intertransverse osteogenesis in S2 rabbits.
Conclusion:
This work confirms the feasibility of bone regeneration and spinal fusion using solely biocompatible materials and autologous biologic products. Additionally, the greater overall osteogenesis and earlier mineralization afforded by PRP support its clinical utility and potential abrogation for usage of synthetic moieties such as BMPs – or at minimum offer a safer, diminished required dose – in the future.
