Augmentation of bone defect healing using a new biocomposite scaffold: an in vivo study in sheep

Previous studies support resorbable biocomposites made of poly L-lactic acid (PLA) and β-tricalcium phosphate (TCP) produced by supercritical gas foaming as a suitable scaffold for tissue engineering. The present study was undertaken to demonstrate the biocompatibility and osteoconductive properties of such a scaffold in a large animal cancellous bone model. The biocomposite (PLA/TCP) was compared with a currently used β-TCP bone substitute (ChronOSTM, Dr.Robert Mathys Foundation) representing a positive control and empty defects representing a negative control. Ten defects were created in sheep cancellous bone, three in the distal femur and two in the proximal tibia of each hind limb with a diameter of 5 mm and a depth of 15 mm. New bone ingrowth (osteoconductivity) and biocompatibility were evaluated using microcomputed tomography (μCT), and histology at 2, 4, and 12 months after surgery. The in vivo study was validated by the positive control (good bone formation with ChronOSTM) and the negative control (no healing with the empty defect). A major finding of this study was the incorporation of the biocomposite in bone after 12 months. Bone ingrowth was observed in the biocomposite scaffold including its central part. Despite an initial fibrous tissue formation was observed at 2 and 4 months but not at 12 months, this initial fibrous tissue does not preclude the long-term result of the biocomposite as demonstrated by its osteointegration after 12 months as well as the absence of chronic or long-term inflammation at this time point.