Abstract
Many growth factors have been studied as additives accelerating lumbar fusion rates in different animal models. However, their low hydrolytic and thermal stability both in vitro and in vivo limits their workability and use. In the proposed work, a stabilized vasculogenic and prohealing fibroblast growth factor-2 (FGF2-STAB®) exhibiting a functional half-life in vitro at 37 °C more than 20 days was applied for lumbar fusion in combination with a bioresorbable scaffold on porcine models. An experimental animal study was designed to investigate the intervertebral fusion efficiency and safety of a bioresorbable ceramic/biopolymer hybrid implant enriched with FGF2-STAB® in comparison with a tricortical bone autograft used as a gold standard. Twenty-four experimental pigs underwent L2/3 discectomy with implantation of either the tricortical iliac crest bone autograft or the bioresorbable hybrid implant (BHI) followed by lateral intervertebral fixation. The quality of spinal fusion was assessed by micro-computed tomography (micro-CT), biomechanical testing, and histological examination at both 8 and 16 weeks after the surgery. While 8 weeks after implantation, micro-CT analysis demonstrated similar fusion quality in both groups, in contrast, spines with BHI involving inorganic hydroxyapatite and tricalcium phosphate along with organic collagen, oxidized cellulose, and FGF2- STAB® showed a significant increase in a fusion quality in comparison to the autograft group 16 weeks post-surgery (p = 0.023). Biomechanical testing revealed significantly higher stiffness of spines treated with the bioresorbable hybrid implant group compared to the autograft group (p < 0.05). Whilst histomorphological evaluation showed significant progression of new bone formation in the BHI group besides non-union and fibrocartilage tissue formed in the autograft group. Significant osteoinductive effects of BHI based on bioceramics, collagen, oxidized cellulose, and FGF2-STAB® could improve outcomes in spinal fusion surgery and bone tissue regeneration.
Highlights
The use of lumbar fusion procedures in the USA and Europe has rapidly increased over the last decade, and many of these procedures involve the use of bone grafts [1]
Since we have provided specific biomechanical testing based on spine bending and torsion, we need to use some fully bioresorbable standardized materials for comparison with our bioresorbable hybrid implant (BHI) scaffold
Cell-free bioresorbable hybrid ceramic/polymer porous implant modified with collagen, oxidized cellulose and hyperstable FGF2-STAB® protein was applied as a third-generation scaffold for spine regeneration
Summary
The use of lumbar fusion procedures in the USA and Europe has rapidly increased over the last decade, and many of these procedures involve the use of bone grafts [1]. Despite the technical progress of spinal surgery and operative materials, the risk of vertebral fusion failure occurs in 5–35% of cases [2]. Successful fusion depends on several surgical and host factors including the selection of a bone graft or bone substitute with adequate osteoconductive, osteoinductive, and osteogenic properties [3]. Autografting has been considered the gold standard for bone graft procedures as it poses little risk of infection and rejection. Spinal fusion is a well-accepted surgical treatment for many spinal diseases with significant increases projected due to an ageing population. Non-unions are a notable complication of spinal fusion surgery. The limitations have resulted in the utilization of synthetic alternative materials for bone repair, replacement, and enhancement [5]
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