Evaluation of Polylactic Acid/Beta-Tricalcium Phosphate Scaffolds as Segmental Bone Graft Substitutes

The use of processed structural allografts for treatment of massive segmental defects in long bones can be complicated by poor incorporation and remodeling of the devitalized graft, foreign-body reaction and micro-damage accumulation which often leads to catastrophic graft failure [1]. It is therefore useful to develop a bioengineered, biodegradable scaffold that is able to stimulate healing of the defect region. The use of bioengineered scaffolds has been limited due to their poor mechanical strength that does not permit withstanding large in vivo loads and due to their poor osteoinductive properties. We therefore investigated the use of rigid polylactic acid/beta-tricalcium phosphate (PLA/βTCP) composites used in conjunction with osteoinductive factors such as growth hormones (parathyroid hormone (PTH)) and growth factors (bone morphogenic protein-2 (BMP-2) & vascular endothelial growth factor (VEGF)) to stimulate bone formation and vessel ingrowth in the segmental defect region. We examined the physical characteristics of the scaffolds, and evaluated their osteoinductive potential in a clinically-relevant mouse model of a femoral segmental defect with or without PTH treatment. Finally, we used an ectopic bone formation model to assess the efficacy of the scaffold in site-specific delivery of bone anabolic factors.