Spinal fixation is a widely used solution for patients who suffer from vertebral fractures, vertebrectomy, and scoliosis [1]. Although there are existing fixation techniques, frequently used method for spinal fixation is the use of pedicle screws [2]. Durability of fixation is important for life quality of patient. Biomechanical performance of fixation systems plays a major role in this manner. Pullout strength is one of the most important parameters that effect durability of fixation. It depends on several factors such as core geometry, size, bone mineral density (BMD), pitch design, etc. Conical screw cores provide higher pullout strength than cylindrical screw cores. In addition, as much as diameter of screw increases, pullout strength is also increases. BMD is another key factor in terms of pullout strength. Researches revealed that denser bone mediums maintain greater pullout strength, thus screw loose situations are mostly seen on osteoporotic patients. Since...

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