Three-dimensional finite element analysis of a simplified compression plate fixation system

Area of Science:

• Biomechanics
• Mechanical Engineering
• Materials Science

Background:

• Surgical fixation of bone fractures often involves metallic plates and screws.
• Understanding the biomechanical behavior of these fixation devices is crucial for optimizing treatment outcomes.
• Finite element analysis (FEA) offers a powerful tool for simulating complex mechanical interactions in orthopedic implants.

Purpose of the Study:

• To develop and validate a three-dimensional finite element model of a plexiglass tube with a compression plate fixation.
• To analyze the mechanical response of the fixation under various loading conditions, including axial, off-center axial, and bending forces.
• To compare FEA results with experimental strain gage data and composite beam theory.

Main Methods:

• Generation of a linear finite element model of an intact plexiglass tube with a six-hole stainless steel compression plate.
• Application of axial, off-center axial, and four-point bending loads, with superimposed plate and screw pretension.
• Conducting strain gage experiments to validate the finite element model.
• Comparing FEA results with composite beam theory predictions.

Main Results:

• Excellent agreement was found between finite element and strain gage data for key strain components.
• Composite beam theory showed a tendency to overestimate the neutral axis shift caused by plate application.
• The finite element model predicted fracture site distraction due to plate pretension.
• The model indicated a propensity for outer screw failure under combined bending and preload conditions.

Conclusions:

• The developed finite element model is a valid tool for analyzing the biomechanics of fracture fixation in a plexiglass tube model.
• FEA provides insights into load distribution and failure mechanisms not fully captured by composite beam theory.
• Plate pretension significantly influences fracture site behavior and screw stability, particularly under bending loads.