Engineering bone regeneration with bioabsorbable scaffolds with novel microarchitecture

Critical-sized defects (CSDs) were introduced into rat calvaria to test the hypothesis that absorption of surrounding blood, marrow, and fluid from the osseous wound into a bioabsorbable polymer matrix with unique microarchitecture can induce bone formation via hematoma stabilization. Scaffolds with 90% porosity, specific surface areas of approximately 10 m²/g, and median pore sizes of 16 and 32 μm, respectively, were fabricated using an emulsion freeze-drying process. Contact radiography and radiomorphometry revealed the size of the initial defects (50 mm²) were reduced to 27 ± 11 mm² and 34 ± 17 mm² for CSDs treated with poly(D,L- lactide-co-glycolide). Histology and histomorphometry revealed scaffolds filled with significantly more de novo bone than negative controls (p < 0.007), more osteoid than both the negative and autograft controls (p < 0.002), and small masses of mineralized tissue (<15 μm in diameter) observed within the scaffolds. Based on these findings, we propose a change in the current paradigm regarding the microarchitecture of scaffolds for in vivo bone regeneration to include mechanisms based on hematoma stabilization.