Finite element analysis of screw thread geometry and titanium plate materials in internal fixation of the human femur.

Plate and screw osteosynthesis remains essential in orthopedics especially for the fixation of femoral fracture and other long bone injury. The objective of this investigation was to analyze the behavior of a titanium-plated and screwed femur during realistic loading while analyzing stress, strain, and displacement. The square, round, trapezoidal, and triangular screw thread profiles were investigated in terms of their transmission behavior on the head, shaft, and plates. Square thread profiles distribute the stress more uniformly, which results in a reduction in both peak and global von Mises values and the potential for microfracture, loosening, and failure. The triangular and trapezoidal threads initiated the development of local stress hotspots at the plate eyelets, as well as at screw bone interface. The twisted threads demonstrated a moderate overall favorable response. Plate stress patterns were material-property dependent, and strain and deformation increased linearly with the load. Square and round threads increased construct stiffness. In general, screw geometry and plate choice have been identified as major levers for design-informed personalized osteosynthesis.