Osteosynthesis Metal Plate System for Bone Fixation Using Bicortical Screws: Numerical-Experimental Characterization

Area of Science:

• Orthopedic biomechanics
• Biomaterials science
• Computational mechanics

Background:

• Standard immobilization systems are crucial for treating bone fractures.
• Dynamic compression plates (DCP) with lag screws are commonly used for femoral diaphysis fractures.
• Understanding the mechanical behavior of these systems is vital for optimizing treatment outcomes.

Purpose of the Study:

• To numerically and experimentally characterize a standard DCP immobilization system for simple oblique femoral diaphysis fractures.
• To assess the mechanical behavior and stability of a femur stabilized with a DCP and lag screw.
• To evaluate screw-bone interface and bone fracture behavior under load.

Main Methods:

• Four-point bending tests were conducted to reveal the non-linear behavior and damage propagation in cortical bone.
• Experimental pull-out tests were performed to measure damage parameters, including screw loosening.
• A realistic numerical model of the DCP-femur construct was developed using validated damage parameters and contact mechanics.
• A mixed-mode (I+II) trapezoidal damage law was implemented to simulate bone and screw-bone interface behavior.

Main Results:

• The non-linear mechanical behavior of cortical bone, including damage initiation and propagation, was characterized.
• Screw loosening was observed experimentally, and its parameters were quantified.
• The numerical model successfully replicated the experimental global behavior, including initial stiffness and peak load prediction.
• The model accurately predicted bone crack initiation and propagation under simulated physiological loading.

Conclusions:

• The study validates the use of a DCP system with a lag screw for stabilizing femoral fractures.
• The developed numerical model provides a reliable tool for predicting the mechanical performance of orthopedic implants.
• This research contributes to a better understanding of fracture fixation mechanics and can inform future implant design and surgical techniques.