Computational simulation of axial dynamization on long bone fractures

Area of Science:

• Orthopedics
• Biomechanical Engineering
• Computational Modeling

Background:

• Axial dynamization is known to enhance bone healing and remodeling.
• Previous research has not explored non-axial movements or uniform compression during dynamization.
• The optimal relaxation of fixator joints for dynamization remains uninvestigated.

Purpose of the Study:

• To analyze fixator joint adjustments and resulting fracture site movements during dynamization.
• To investigate the occurrence of non-axial movements during dynamization.
• To determine methods for achieving controlled axial movement or uniform compression.

Main Methods:

• Utilized computational models of two commercial unilateral external fixators (Dynafix and Orthofix).
• Analyzed fixator joint adjustments and their impact on fracture site movements.
• Simulated dynamization under various joint configurations.

Main Results:

• Significant non-axial movements occurred when fixator joints were not parallel to the bone axis.
• The Dynafix fixator's dual sliding joint design reduced non-axial movements.
• Simultaneous adjustment of all fixator joints enabled precise axial movement or uniform compression.

Conclusions:

• Non-axial movements during dynamization can be significant and are correctable by relaxing specific fixator joints.
• The modeling technique is applicable to bone lengthening to ensure limb alignment.
• Results aid in external fixator performance assessment and application for controlled axial movement.