Two Versus Four Ilizarov Rings in All Schanz Screw Fixation for Fractures of the Tibia: Experimental Mechanical Testing

The mechanical performance of the Ilizarov system is closely related to the biologic status of the fracture or osteotomy line. The aim of this study was to compare the mechanical performance of 2 different Ilizarov frame configurations. Two different frame models were applied to cow tibiae, 1 with 2 rings only, 1 proximal and another distal, vs the conventional 4 rings, 2 proximal and 2 distal. The 2 models were applied to both tibiae of the same animal to overcome variations between the animal’s bones. The midpoint of the tibial bones was osteotomized, 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 under axial compression. Mechanical testing was performed with a load cell of 20,000 N and a speed of 2 mm/min. Measurements were evaluated using load cell and goniometric grading; load deformation was calculated using load-deformation graphs. Our comparison showed that the 4-ring frame had 37.5% greater stiffness than the 2-ring frame under direct loading under larger loads (P<.01). A comparison between the 4- and 2-ring configurations demonstrated that the 4-ring frame had 7% greater stiffness than the 2-ring frame under direct loading under smaller loads (P>.05). An excellent outcome can be achieved by using a conventional 4-ring frame, but the use of the 2-ring frame remains an available option for fixation of fractures in low-weight patients.