Infill Architecture Drives Early Osteogenesis in Additively Manufactured PCL Scaffolds With Controlled Porosity

Critical sized bone defects represent a significant challenge in orthopedic and reconstructive surgery. Additively manufactured (AM) bone scaffolds may be effective tools to treat these defects; however, the influence of infill architecture on early bone formation remains poorly characterized. This study used 3D-printed biodegradable polycaprolactone (PCL) scaffolds to investigate the relationships between infill architecture, bone growth, and mechanical properties in a 4-week in vitro experiment. Scaffolds containing bovine allograft were constructed with Gyroid and Honeycomb architectures at two porosity levels (40% and 60%). It was hypothesized that Gyroid scaffolds would accelerate early bone formation compared with Honeycomb designs. Gyroid architectures generally showed greater metabolic activity at weeks 3 and 4, with significant differences varying by porosity and time point. Micro-CT analysis demonstrated significantly greater mineralized tissue volume and mineral density in Gyroid scaffolds compared with Honeycomb scaffolds at 4 weeks. Compressive mechanical testing indicated that Honeycomb structures were significantly stiffer and stronger than Gyroid scaffolds throughout the study. These results demonstrate that infill architecture significantly influences early bone formation independently of pore size and highlight a fundamental tradeoff between biological and mechanical performance in AM PCL scaffold design.