Mechanical considerations in using tensioned wires in a transosseous external fixation system

Area of Science:

• Orthopedic biomechanics
• Biomaterials science
• Surgical instrumentation

Background:

• External fixation devices are essential for stabilizing fractures.
• Achieving and maintaining optimal wire tension is critical for device stability and patient outcomes.
• Understanding factors influencing wire tension is necessary for improving clinical practice.

Purpose of the Study:

• To investigate key factors influencing wire tension in circular external fixators.
• To identify the primary cause of wire tension loss.
• To establish guidelines for safe and effective wire tensioning.

Main Methods:

• Utilized external mechanical testing units and in-line load cells to measure wire tension.
• Examined the relationship between wire deflection and stiffness.
• Assessed the impact of fixation nut torque on wire slippage.

Main Results:

• A self-stiffening effect was observed in circular external fixators, increasing wire stiffness with deflection.
• Mechanical slippage between the wire and fixation bolt was identified as the main cause of tension loss.
• Adequate fixation nut torque (20 N.m) effectively prevented slippage.

Conclusions:

• Proper torque on fixation nuts is essential to prevent wire slippage and maintain tension.
• Guidelines for safe tensioning techniques can ensure clinically indicated tensions without breakage risk.
• Optimized wire tensioning enhances the stability and efficacy of external fixation.