A lattice topology optimization of cervical interbody fusion cage and finite element comparison with ZK60 and Ti-6Al-4V cages.

BACKGROUND: In current clinical practice, the most commonly used fusion cage materials are titanium (Ti) alloys. However, titanium alloys are non-degradable and may cause stress shielding. ZK60 is a bio-absorbable implant that can effectively avoid long-term complications, such as stress shielding effects, implant displacement, and foreign body reactions. In this study, we aimed at investigating the biomechanical behavior of the cervical spine after implanting different interbody fusion cages. METHODS: The finite element (FE) models of anterior cervical disc removal and bone graft fusion (ACDF) with a ZK60 cage and a Ti cage were constructed, respectively. Simulations were performed to evaluate their properties of flexion, extension, lateral bending, and axial rotation of the cervical spine. Moreover, a side-by-side comparison was conducted on the range of motion (ROM), the deformation of cages, the stress in the cages, bone grafts, and cage-end plate interface. Simultaneously, according to the biomechanical analysis results, the microporous structure of the ZK60 cage was improved by the lattice topology optimization technology and validation using static structure. RESULTS: The ROMs in the current study were comparable with the results reported in the literature. There was no significant difference in the deformation of the two cages under various conditions. Moreover, the maximum stress occurred at the rear of the cage in all cases. The cage's and endplate-cage interface's stress of the ZK60 group was reduced compared with the Ti cage, while the bone graft stress in the ZK60 fusion cage was significantly greater than that in the Ti fusion cage (average 27.70%). We further optimized the cage by filling it with lattice structures, the volume was decreased by 40%, and validation showed more significant biomechanical properties than ZK60 and Ti cages. CONCLUSION: The application of the ZK60 cage can significantly increase the stress stimulation to the bone graft by reducing the stress shielding effect between the two instrumented bodies. We also observed that the stress of the endplate-cage interface decreased as the reduction of the cage's stiffness, indicating that subsidence is less likely to occur in the cage with lower stiffness. Moreover, we successfully designed a porous cage based on the biomechanical load by lattice optimization.

Structural, physicochemical, and digestibility properties of starch-soybean peptide complex subjected to heat moisture treatment.

Interactions among food components during food processing play important role in starch digestibility. The objective of this study was to investigate the effects of heat moisture treatment on the structural, physicochemical, and digestibility properties of starch-soybean peptide complexes. Corn and potato starch mixed with different amounts of soybean peptide were subjected to heat moisture treatment. The addition of soybean peptide increased pasting temperature, while decreased peak viscosity and swelling power in both starch samples under heat moisture treatment. Thermal analysis showed that soybean peptide retarded starch gelatinization, and heat moisture treatment contributed to a more stable crystalline structure. Lower RDS contents and higher RS contents were associated with higher soybean peptide amounts. Potato starch was more sensitive to heat moisture treatment than corn starch. The results will enrich the interaction theory between starch and protein, and will be important for the development of carbohydrate-restricted diet and protein-based functional foods.