الفهرس 
ٌTitle : Two Ilizarov rings versus four Ilizarov rings in all schanz screw fixation of comminuted fracture of the tibia; an experimental mechanical testing
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Abstract
Background: External fixation is a widely used method for stabilizing bone fragments in distraction osteogenesis and fracture fixation. The Ilizarov circular external fixator has proven to be a reliable method for the treatment of complex fractures, infected non-union, correction of deformities and limb lengthening. The mechanical performance of the Ilizarov system is closely related to the biologic status of the fracture or the osteotomy line.The effect of this factor on surgical results has caused researchers to focus on this subject in recent years .The aim of this study is to compare the mechanical performances of two different Ilizarov frame configurations. Materials and methods: Two different frame models were applied to the cow tibiae bones. One with two rings only, one proximal and another distal versus conventional use of 4 rings, two proximal and two distal, all with the same number and site of schanz. The two models were applied in the two tibiae of the same animal to overcome any individual variations between the animal{u2019}s bones.The midpoint of the tibial bones was osteotomised and the osteotomy was distracted for 2 cm. Six identical samples for each model were created and each identical sample of each model was tested in axial compression. Instron mechanical testing was performed with load cell 20000 Newton and speed 2mm/min. Measurements were evaluated by load cell and goniometric grading. Load-deformation was calculated by using Load-deformation graphs. Results: A comparison between the 4 rings and 2 rings configurations demonstrated that the 4 rings frame had 37.5 % greater stiffness than did the 2 rings frame under direct loading in larger loads (p < 0.01). And a comparison between the 4 rings and 2 rings configurations demonstrated that the 4 rings frame had 7 % greater stiffness than did the 2 rings frame under direct loading in smaller loads (P > 0.05)