STUDIES ABOUT VIRTUAL BEHAVIOR OF TIBIA FRACTURES AND NAILS DURING THE FIXATION PROCESS

Abstract

Tibia shaft fractures are the more frequent fractures of lower limb. To determine the behavior during the fixation process there was used a CAD parametric software which permits defining models with a high degree of difficulty. First, there were defined the main bone components as tibia using CT images. These images were transferred to AutoCAD where the outer and inner contours of the bone were approximate to polygonal lines composed by many segments. These contours were transferred to SolidWorks where, step by step, and section by section, was defined the virtual tibia. At the first time, the tibia was complete and, after that, it was divided in 2, 3 or more components to simulate different types of fractures. Using the direct measurement method the virtual metallic components as nail and orthopedic screws were generated. All these virtual components were combined to obtain four cases of tibia fractures studies. The idea to design a tibia nail, which eliminates the use of orthopedic screws was given by the study of surgical techniques imposed by the classical tibia nails. Classical nails had some important disadvantages, such as the difficulty of manipulation and positioning in the bone and, in the same time, the complicate orientation and displacement of the distal screws using the nail guide. Also, all these operations can give failures or/and wrong holes in the bone which can make tibia more breakable. The virtual models were exported to a software for kinematical and FEA simulation. Using similar initial parameters for each studied case (as total force and torque) there were obtained dynamic maps of stress, strain and displacement. These results were analyzed and compared and, in the final, it was extracted an important conclusion.

Keywords

• tibia fracture, virtual bones, tibia nail, biomechanics, CAD, FEA.