| Budget Amount *help |
¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000)
Fiscal Year 2017: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2016: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2015: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
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| Outline of Final Research Achievements |
Pedicle screw-based instrumentation is one of the most popular implants in spinal fixation. However, there are few reports regarding the appropriate screw size which maintains the biomechanical strength in the pedicle. In this study, we examined the relationship between the pedicle screw size and biomechanical stability of screw placed in the immature and mature spine. Micro CT scans of the pedicles were taken after every tapping operation and radiological findings of pedicle were examined. The pedicle screws (6.5 - 11.5 mm) were tested using pullout testing with tensile tester. In mature vertebrae, the largest diameter of the screw that did not cause pedicle failure was 10.8 ± 1.2 mm, which was 117 ± 19 % of their original pedicle diameter. Immature pedicles were more expanded by application of serial tappings without osseous branch than mature pedicles (125 ± 14 % of their original diameter). The pullout strength of the screw was maintained as long as bony branch was not observed.
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