Augmentation in vivo by silk fibroin/calcium phosphate cement of defected vertebrae in a sheep model / 中华创伤骨科杂志

ABSTRACT

Objective To study the feasibility of using silk fibroin/calcium phosphate cement (SF/CPC) as an injectable bone augmentation filling material for defected vertebrae in a sheep model.Methods Bone defects were created on L3,L4 and L5 in 24 adult sheep through the lateral retroperitoneum approach.CPC,SF/CPC,and polymethylmethacrylate (PMMA) were injected into the defects of 3 vertebrae randomly.Twelve sheep were sacrificed at 1 and 6 months postoperation,respectively.Un-decalcified sections were made from the specimens from any 4 sheep and stained with Van-Gieson method.The microcosmic changes of bone-material interface were observed,and the amounts of new bone formation and cement residue were evaluated by histomorphometric analysis.Biomechanical testing was performed on the specimens from the other 8 sheep,in which the strength and stiffness were determined on the vertebrae with L6 as a control.Results Histologically,CPC and SF/CPC contacted the bone directly but the absorption and bone formation were superficial at one month postoperation.At 6 months postoperation,the absorption and bone formation were limited on the surface of CPC while the absorption and bone ingrowth were accelerated in SF/CPC group.In PMMA group where no significant changes were observed between 1 and 6 months,the material contacted the bone loosely,with membrane structure at partial interface but no new bone formation on the material.Histological quantitative analysis showed that new bone formation was significantly more and cement residue significantly less in SF/CPC group than in CPC group at 6 months (P ＜0.05).Biomechanical testing showed that the compressive strength and stiffness were significantly enhanced at 6 months compared with one month in CPC and SF/CPC groups but significantly decreased in PMMA group (P ＜ 0.05).At the 2 time points,SF/CPC,PMMA and intact groups showed equivalent compressive strength and stiffness(P ＞ 0.05).Conclusions The SF/CPC composite has advantages of satisfactory bioactivity and osteoconduction,and relatively faster cement degradation and bone formation during which biomechanical function of vertebrae can be maintained.Therefore it may become a new kind of vertebral augmentation filling material to replace PMMA.