Finite Element Analysis of Dual Screw Configurations for Enhanced Stability in Scaphoid Fracture Fixation

Area of Science:

• Orthopedic surgery
• Biomechanics
• Surgical fixation

Background:

• Headless compression screws are standard for scaphoid fractures.
• Dual screw fixation offers theoretical biomechanical advantages.
• Optimal configuration for dual screw fixation requires investigation.

Purpose of the Study:

• To determine the optimal dual screw configuration for scaphoid fracture fixation.
• To evaluate the biomechanical stability of different screw distances and angulations.
• To compare interfragmentary displacement and von Mises stress for various configurations.

Main Methods:

• A finite element model of the scaphoid with a waist fracture was used.
• Two 1.7 mm cannulated compression screws were simulated.
• Screw distance (3.4-6.8 mm) and angulation (5°-20°) were systematically varied.
• Interfragmentary displacement (IFD) and von Mises stress were analyzed.

Main Results:

• Increased screw distance (up to 6.8 mm) significantly reduced IFD and von Mises stress.
• Maximum IFD decreased from 0.057 mm to 0.0227 mm with increasing distance.
• Maximum von Mises stress decreased in both proximal and distal fragments with greater screw separation.
• Screw angulation showed no significant biomechanical influence on stability.

Conclusions:

• A larger interscrew distance provides superior biomechanical stability for dual screw fixation of scaphoid fractures.
• Screw angulation does not significantly impact biomechanical stability but may aid placement.
• Findings support optimizing screw placement for enhanced fracture fixation and surgical planning.