A biomechanical comparison of three hybrid linear-circular external fixator constructs

Area of Science:

• Orthopedic biomechanics
• Biomaterials engineering
• Surgical implant design

Background:

• Linear-circular hybrid fixators offer versatile bone stabilization.
• Optimizing construct stiffness is crucial for effective fracture management.
• Understanding load-bearing characteristics guides clinical application.

Purpose of the Study:

• To evaluate the biomechanical performance of three linear-circular hybrid fixator configurations.
• Assess stiffness, displacement, ring deformation, and bone motion under various loading conditions.

Main Methods:

• Biomechanical evaluation of three hybrid fixator configurations (Ia, Ia(d), Ib) with 8 replicates each.
• Loading constructs in axial compression, craniocaudal bending, mediolateral bending, and torsion using a materials testing machine.
• Measuring ring deformation and calculating bone model motion at the fracture gap.

Main Results:

• Constructs Ia(d) and Ib demonstrated significantly greater stiffness than Ia under axial compression.
• Construct Ib showed significantly higher stiffness in craniocaudal bending and torsion compared to Ia and Ia(d).
• No significant differences were observed in mediolateral bending; permanent ring deformation did not occur; bone motion decreased with Ia(d) and Ib.

Conclusions:

• The addition of a secondary hybrid rod enhances construct stiffness in multiple loading modes.
• Biplanar fixation pin placement further improves stiffness and reduces bone motion.
• These modifications offer potential benefits for fracture stabilization and healing.