3D Printed Biodegradable Orthopaedic Implant Development to Control Interfragmentary Loading during Fracture Repair

Introduction: Controlled breakdown of porous, 3D printed, biodegradable trauma implants may improve and accelerate fracture healing; however, little is known about this novel approach. The purpose of this study was to determine the initial strength and degradative kinetics of test coupons at clinically relevant time points. We hypothesized that sparse lattice specimens would have significantly decreased initial mechanical properties and faster degradation kinetics than dense or solid ones.

Materials and Methods: Solid, dense, and sparse-latticed tensile test coupons were fabricated using 85:15 poly-lactic-co- glycolic (PLGA) filament. Coupons were implanted subcutaneously in Sprague-Dawley rats for 0, 4, or 8 weeks. Tensile mechanical properties were measured after retrieval.

Results: Reduction in lattice density led to decreases in mechanical properties at the 0-week time point. Dense and sparse- latticed samples experienced relative increases in mechanical properties at the 4-week time point, which were maintained through 8 weeks. There were no significant changes to mechanical properties in the solid group at 4 or 8 weeks.

Discussion/Conclusion: Results from week-0 testing confirmed our initial hypothesis: that changes to 3-D printed lattices can result in significant changes in mechanical properties. Results from the 4- and 8-week time points rejected our second hypothesis: that in vivo degradation of PLGA would lead to decreased mechanical properties. Increases in stiffness of the porous specimens were driven by infiltration of fibrous tissue into voids that were occupied by air at time zero. This study represents initial findings that will help us better understand the complicated interactions between lattice architecture, fracture reconstruction strength, and implant biodegradation.

Acknowledgement: This study was funded by NIH K25AR078383, VA RR&D I01 RX002274; student support funded by NIH T35 OD010919.

Publication History

Article published online:
26 October 2022