A Pre-Set Calcium Sulfate/Hydroxyapatite Biomaterial as an Antibiotic-Eluting Bone Extender and a Carrier for BMP-2:...

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Regenerative Medicine

Background:

• Autologous bone is the gold standard for spinal fusion but requires a second surgical site.
• Synthetic bone graft extenders (BGE) aim to supplement or replace autologous bone in spinal fusion.
• Calcium sulfate/hydroxyapatite (CaS/HA) is a potential BGE material for drug and growth factor delivery.

Purpose of the Study:

• To evaluate CaS/HA as an antibiotic-eluting BGE and a carrier for bone morphogenetic protein-2 (BMP-2).
• To assess CaS/HA combined with tobramycin (TOB) and BMP-2 in a rabbit posterolateral lumbar fusion (PLF) model.
• To determine if CaS/HA + BMP-2 can replace autologous bone grafting in spinal fusion.

Main Methods:

• In vitro testing of TOB release kinetics and antibacterial activity against Staphylococcus aureus from CaS/HA beads.
• In vivo PLF study in rabbits using CaS/HA beads with either TOB + autograft or BMP-2.
• Radiological, mechanical, micro-CT, and histological assessments of spinal fusion at 12 weeks.

Main Results:

• TOB showed rapid in vitro release, sustained antibacterial activity for 19 days, and low in vivo serum levels.
• Both CaS/HA + TOB + autograft and CaS/HA + BMP-2 groups achieved high fusion rates (100% mechanical).
• Micro-CT and histology confirmed bone bridging with no significant difference in bone volume between groups.

Conclusions:

• CaS/HA material loaded with TOB demonstrated effective in vitro antibacterial properties without compromising BGE function.
• CaS/HA combined with BMP-2 successfully induced bone formation, suggesting potential to replace autologous bone.
• This pilot study supports CaS/HA + BMP-2 as a viable alternative for spinal fusion, with TOB offering potential perioperative infection control.