Structural stiffness and reducibility of external fixators placed in malalignment and malrotation

Area of Science:

• Orthopaedic biomechanics
• Trauma surgery
• Biomedical engineering

Background:

• External fixators are vital for fracture immobilization, especially in complex scenarios.
• Assessing the performance of different external fixator designs under malreduction conditions is critical.

Purpose of the Study:

• To evaluate the structural stiffness and reducibility of various external fixators when applied in malalignment and malrotation.
• To compare the effectiveness of different external fixator configurations in achieving anatomic reduction.

Main Methods:

• A biomechanical laboratory study tested thirteen external fixators in fifteen configurations.
• Fixators were applied to malreduction jigs, with attempts at anatomic reduction and subsequent stiffness testing.
• Testing included anteroposterior bending, lateral bending, axial load, and torsion.

Main Results:

• Only six of thirteen configurations allowed anatomic reduction without repositioning.
• Nine configurations failed to achieve anatomic reduction on the malreduction model.
• Structural stiffness varied significantly across all tested external fixator configurations.

Conclusions:

• External fixator design (e.g., single-pin, dual-pin, multipin bar clamps) influences structural stiffness and reducibility.
• Proper selection of external fixators is essential for effective fracture immobilization in suboptimal conditions.
• Repositioning of fixator pins may be necessary for anatomic reduction with certain external fixator types.