Influence of Wolff's law on the biomechanical and corrosion behavior of screws in femoral neck fixation

Abstract

This study evaluates the biomechanical performance of Ti6Al-4 V and 316L stainless steel (SS) screws for femoral neck fracture fixation. The microstructural analysis scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) was conducted to examine material composition. X-ray diffraction patterns of Ti6Al4 V and AISI 316L materials were added for identifying crystallographic phases. Simulation results revealed significant differences when comparing Ti6Al4V and 316L screw materials. For Ti6Al4V screws, the von Mises stress in the screw body was 204.56 MPa, and the stress above the fracture line was 124.57 MPa. In contrast, for 316L stainless steel screws, the stress within the body increased to 236.33 MPa, while the stress at the fracture line decreased to 109.65 MPa. Examining deformation-related parameters, the gap value for Ti6Al4V screws was 0.065 mm, penetration value was 0.0036 mm, sliding distance was 0.109 mm, and total deformation was 2.4625 mm. For 316L screws, these values are 0.054 mm, 0.0032 mm, 0.091 mm, and 2.4634 mm, respectively. While 316L offers better initial mechanical stability, Ti6Al4 V remains favorable for long-term use due to superior corrosion resistance and biocompatibility. Despite widespread use of Ti6Al4 V and 316L SS in femoral neck fracture fixation, comparative data on their biomechanical performance and corrosion behavior under torsional loading remain limited. This study focuses on these two clinically relevant materials, evaluating their mechanical behavior and corrosion susceptibility. Finite-element analysis was performed to simulate torsional stress, while SEM and EDS analyses examined microstructural characteristics influencing performance. The results showed nearly identical deformation for both materials, with 316L exhibiting higher screw stress but lower stress at the fracture line, leading to reduced micromotions. Ti6Al4 V offered superior corrosion resistance and long-term biocompatibility. These findings provide quantitative insights for implant selection, supporting designs that balance immediate mechanical stability with favorable long-term material performance. Further research is needed to identify the most effective implant design and material selection to balance immediate fixation and support desirable bone regeneration.