Objective. The aim of this study was to determine the stiffness characteristics of the standard
and hybrid Ilizarov fixators.
Design. Five different frame models (one standard and four hybrid Ilizarov) were designed.
Four full rings were used in the standard Ilizarov frame. Two rings were placed proximal
and two rings were placed distal to the osteotomy line with two wires at 90° to each
other on each ring. The distal tibial fixation of all the hybrid configurations and
standard Ilizarov fixator were the same, and only the proximal fixations were different.
In hybrid models, different numbers of 90° femoral arches (1–3) were fixed to the
proximal segment by using the half-pins with different numbers (2–4) and different
angles to each other (45° and 90°).
Background. Numerous investigations have been performed to compare the mechanical properties
of different frames. The Ilizarov method of fracture fixation and limb lengthening
has recently gained international recognition. But its application is difficult in
some anatomic localization, so that hybrid ring fixation frames of various configurations
are gaining clinical popularity.
Methods. Five different frame models were applied to the sheep tibial bones. The midpoint
of the tibial bones was osteotomised and the osteotomy distracted for 2 cm. Four identical
samples for each model were created and each identical sample of each model (n=1) were tested four times in axial compression, antero-posterior and medio-lateral
bending, and torsion.
Results. In standard Ilizarov fixator, axial and bending stiffness was found to be more than
all hybrid Ilizarov fixator models. Between the hybrid fixators, higher axial and
bending stiffness was found when the number of femoral arches and half-pins were increased.
Different angles between the half-pins formed 67% alteration in medio-lateral bending
stiffness. No significant difference was found for torsional stiffness between the
Conclusions. For optimum fixator stiffness in hybrid fixators, at least three femoral arches and
four half-pins must be used and these half-pins should be placed at 90° angles and
at different planes to each other. However, it should be remembered that, hybrid fixator
models had less axial and bending stiffness than standard Ilizarov fixator model.Relevance
For optimum fixator stiffness in hybrid fixators, at least three femoral arches and
four half-pins must be used. However, it should be remembered that, hybrid fixator
models had less axial and bending stiffness than standard Ilizarov fixator model.