Long-term comparison of two β-TCP/PLCL composite scaffolds in rabbit calvarial defects

Improving bone-graft substitutes and expanding their use in orthopedic and spinal surgery leads to shorter surgical times, fewer complications, and less pain among patients both in human and veterinary medicine. This study compared an elastic porous β-tricalcium phosphate/poly(L-lactide-co-ε-caprolactone) (β-TCP/PLCL) copolymer scaffold (composite scaffold) and a commercially available β-TCP/PLCL bone-graft substitute (chronOS Strip) in a rabbit calvarial defect. A bilateral, 12-mm circular defect was created in the parietal bones of 12 rabbits. Both graft materials were soaked in bone marrow aspirate before implantation, and the usability of the material was recorded during surgery. After a follow-up time of 24 (n = 5) and 48 (n = 7) weeks, artificial intelligence- (AI-) assisted micro-CT imaging was used to evaluate the bone formation and β-TCP distribution. Bone formation, implant material decomposition, and tissue reactions were further investigated through histopathology and AI-assisted histomorphometric analyses. Both materials supported tissue ingrowth and vascularization and modest 10%-16% new bone formation through the implant. In both materials the degradation advanced during the follow-up time, but there was implant material visible 48 weeks after implantation. Typical long term foreign body reaction with histiocytes, giant cells and lymphocytes, was seen in both materials being more pronounced in composite scaffold. The benefit of the new composite scaffold was its superior usability during surgery.