Biomechanical comparison of hybrid external fixators.
OBJECTIVE
To determine the stiffness characteristics of the hybrid ring fixator in the treatment of (OTA 41-C) proximal metaphyseal and shaft tibial fractures.


METHODS
Five identical composite tibiae were fixed with a Synthes, ACE Fischer, Howmedica Monticelli-Spinelli, or Smith & Nephew Trauma Ilizarov hybrid external fixator or with the conventional Ilizarov wire fixator. The Synthes and Monticelli-Spinelli fixators were tested twice, the first time with the connectors on the outside of the ring and the second time with the connectors on the inside of the ring.


METHODS
A materials testing machine was used to apply pure compression, anterior and posterior bending, medial and lateral bending, and torsion. Stiffness values were calculated from the load deformation and torque angle curves.


RESULTS
Overall, the Synthes and Monticelli-Spinelli fixators were the most rigid of the fixators when the wire-to-ring connectors were placed inside the ring. In general, the fixators were stiffest in axial compression and least stiff in posterior bending. Wire length had a significant effect on overall stiffness.


CONCLUSIONS
This study suggests that the four hybrid external fixators in standard configuration have stiffness characteristics similar to those of the conventional Ilizarov fixator when used to treat proximal metaphyseal and shaft fractures of the tibia.
Department of Orthopaedic Surgery, Georgia Baptist Medical Center, Atlanta, USA.
D W
DW
Lundy
M J
MJ
Albert
W C
WC
Hutton
D001696:Biomechanical Phenomena; D004867:Equipment Design; D016267:External Fixators; D006801:Humans; D008422:Materials Testing; D013978:Tibial Fractures / Q000601:surgery