Enhanced mechanical and osteoconductive properties of custom-extruded PLA-bone powder filaments for orthopedic implants

This study presents the design and fabrication of a specialized extruder for producing polylactic acid (PLA) composite filaments reinforced with bone powder at three weight ratios (95%-5%, 90%-10%, and 85%-15%), intended for biomedical and veterinary orthopedic applications. The extruder integrates a PID temperature controller, a nozzle-integrated heater, and potentiometer-based motor speed regulation, enabling a stable extrusion process at a constant temperature of 185 °C and a motor speed of 3 Hz. The filaments were systematically evaluated for their mechanical properties through tensile testing. Commercial PLA exhibited the highest ultimate tensile strength ( \(29.15 ± 1.03\) MPa) and ductile behavior, reaching a strain of \(8.71 ± 0.72\) mm/mm before fracture. Among the composites, tensile strength decreased with increasing bone powder content, from \(20.50 ± 2.5\) MPa (95%–5%) to \(15.00 ± 2.0\) MPa (90%–10%) and \(11.25 ± 2.75\) MPa (85%–15%), accompanied by a progressive transition toward brittle fracture, with the strain at fracture dropping to \(3.90 ± 0.60\) mm/mm for the 85–15% composite. This embrittlement was further reflected in the energy absorption capacity, which declined from 6.20 MJ/m 3 for commercial PLA to 1.40, 0.98, and 0.53 MJ/m 3 for the 95%–5%, 90%–10%, and 85%–15% composites, corresponding to reductions of approximately 77%, 84%, and 91%, respectively. Although bone powder incorporation reduced both strength and toughness relative to pure PLA, it is expected to impart osteoconductive functionality, making these filaments promising candidates for orthopedic applications where bioactivity is prioritized. Overall, this work demonstrates the feasibility of fabricating PLA/bone powder composite filaments via a custom extrusion system, establishing a foundation for the development of bioabsorbable, patient-specific implants through additive manufacturing.