Biomechanical evaluation of 10 configurations of a small external fixator set

The small AO (Synthes, Paoli, Pa) external fixator is a valuable tool for the treatment of distal radius fractures. The construct has many possible bar and pin configurations. However, there are no data regarding which construct is optimal with respect to strength and versatility. We tested 10 configurations to determine bending stiffness, rotation, and axial loading. Although slight variations were found between constructs for bending and rotation forces, there were marked differences between constructs during axial loading. A frame design without bar-to-bar clamps was determined stiffest. However, this configuration may be more difficult to apply and adjust in the clinical setting. Although an "ideal" construct applicable to all fracture types does not exist, knowledge of the strengths of various configurations may allow for optimization of fixator assembly to meet specific clinical needs.