The stiffness characteristics of hybrid Ilizarov fixators.

The use of hybrid Ilizarov models around femoral area is gaining clinical popularity lately. Hybrid systems show different mechanical properties. The purpose of this report is to examine the stiffness characteristics of the C-arch and half-pins on the hybrid Ilizarov fixators. Eight models that included standard Ilizarov and hybrid models were applied to six femoral sawbones. The distal part of fixation was composed of a two-ring frame applied identically to all bones. The difference of the configuration was at the proximal part, where half-pins with or without C-arches were either added to the proximal two-ring frame or replaced the proximal one- or two-ring frame. Osteotomy was performed in the femoral diaphysis and the bone was distracted 2cm. The stability of the system was tested with the axial compression testing machine. Displacements between the adjacent fracture sides were measured with the video extensometer in three dimensions. We found that proximal half-pin applications alone had less stiffness, but half-pins with C-arch had more stiffness than the model including only half-pins. Additional half-pins onto one- or two-ring frames had more longitudinal stiffness, but this system showed weak resistance against transverse displacement.