Stress Analysis of Bone Scaffold Designed for Segmental Bone Defects

Abstract

Segmental bone defects result in isolated bone fragments. These defects may be caused by trauma or disease and are a leading cause for orthopedic surgery. Segmental defects pose a challenge as they contain gaps between the ends of bones, which are too large for the regenerating tissue to naturally bridge and repair. A widely used clinical approach to repair such defects is the use of autografts that provide the essential bone growth features. However, autografts generate a secondary deficit in the region from which the graft was harvested. This grafting procedure may result in other complications, such as infections, inflammation, scarring, and bleeding. Synthetic bone scaffolding has been explored as a viable method of helping the body repair segmental bone defects. While synthetic bone scaffolding is a promising approach in orthopedic treatments, limitations exist. Bone is a complex organ with many cell types, emergent, anisotropic, mechanical properties and molecular interactions. Studies have shown that the inner geometries, such as pore size, play an integral role in bone regeneration, cell proliferation, differentiation and recovery. An architecturally-based approach in the design and fabrication of the scaffold may support the differentiation of complex bone tissues. This study developed and tested scaffold designs having different pore size and beam thickness. The designs were developed and simulated for compression and tension in SolidWorks. A hexagonal unit cell was the basis for scaffold design. In one experimental trial (Group 1), the offset of the layers was varied. In another experimental trial (Group 2), the ratio between pore size and beam thickness was varied while using the optimal offset from the former trial. The material for simulation was poly-L-lactic (PLA) acid. In the analysis of the simulation results, the optimal layer offset configuration of 100%,50% in the positive x-y direction showed the lowest stress distribution for both compression and tensile simulations compared to the other offset configurations analyzed. In the second trial of Group 2 models, two models with pore size to beam thickness ratios (7:1 and 8:1) demonstrated low stress distribution under the simulated physiological environments. These results suggest that both models can potentially have different applications in the repair of segmental bone defects.