日常活動對於脊椎造成長期負載，使椎骨產生疲勞性質改變與退化的主因之ㄧ，故學者們在過去的研究中對椎骨進行疲勞測試，如椎間盤疲勞測試，剪力疲勞測試（Fatigue test in shear loading）與軸向負載疲勞測試（Pure compressive fatigue loading）等，而本文中運用實驗設計方法與軸向負載疲勞測試，施加不同疲勞負載大小與頻率於豬隻椎骨，探討負載大小與頻率是否產生交互影響，並研究影響椎骨疲勞特性之顯著因子。
本研究以54個豬胸椎單節椎骨試樣，以20-60%、20-70%及20-80%之極限負載分別於0.5 Hz、1 Hz及2 Hz之頻率下進行全因數實驗，每組實驗參數重覆六次實驗，並量測3600次循環內之椎骨變形量，再分別以下述條件作為評估椎骨特性之依據：
1. 試樣是否破壞 (D)。
2. 實驗開始第十個循環之勁度定義為初始狀態之椎骨勁度 (Si)。
3. 達到變形量穩定時之勁度 (Sss)。
4. 最後一次循環之數量 (Nend)及最後循環進度 (Send)。
5. 總位移量 (Disp)。
6. 達到穩定時之剛性與第十次循環之剛性比值 (Rss/i)。
7. 達到穩定時之剛性與最後循環之剛性比值 (Rend/ss)。
　　實驗結果得知，負載大小僅對於變形量達到穩定狀態前之椎骨勁度有顯著性影響，變形量達到穩定狀態後並沒有顯著影響；負載頻率對於椎骨之疲勞性質並沒有顯著影響，且負載大小及頻率對於椎骨疲勞特性之影響並沒有交互關係。另外在實驗中發現負載大小及負載頻率並不會直接的影響椎骨發生破壞的機率。

Daily activities produce fatigue loading act on spine, and has been known to be one of the major causes of spinal degradation. Thus the effect of fatigue loading upon spine has been quite well studied, such as the fatigue property of disc, fatigue behavior variation due to different type of loading. However, research covering the significant factors which affect the fatigue behavior of a single vertebral body are still lacking. Therefore, this study has focused on investigating the biomechanical response due to the variation of the loading magnitude and frequency. Statistical methods have been employed to evaluate the significant factors influencing the fatigue behavior. One point of specific interest has been whether there is a significant relationship between the loading magnitude and the frequency which affects the fatigue behavior while combined under dynamic loading.
In this study, 54 porcine thoracic spine vertebrae specimens were dissected. Both of loading magnitude and frequency were tested in 3 levels. The test levels of loading magnitude are 20-60%, 20-70% and 20-80% of critical load, the frequency are 0.5 Hz, 1 Hz and 2 Hz. Load-Displacement data was collected, and the variation of the displacement-cycle, the multi-cycle stiffness and the total displacement within 3600 cycles was then calculated. Finally, the correlation between the control factors and the experimental results were investigated.
The fatigue behavior of the specimens were evaluated through the following parameters: the failure of specimen (D); the stiffness at initial state (Si); the number of cycles before reaching a steady state (Nss); the stiffness at steady state (Sss); the total number of cycles (Nend); the specimen stiffness after cyclic fatigue (Send); the total displacement (Disp); the ratio of the stiffness at steady state and that at the tenth cycle (Rss/i); and finally, the ratio of the stiffness at the end cycle and that at steady state (Rend/ss). According to the results, the stiffness before reaching steady state is significantly influenced by the loading magnitude. However, variations in frequency did not affect the stiffness of the vertebrae in this study, and furthermore there is no interaction between loading magnitude and frequency. Moreover, the risk of vertebral failure has not been found to directly relate to the loading magnitude and frequency.

1. Lindsey, D. P., Kim, M. J., Hannibal, M., & Alamin, T. F. “The Monotonic and Fatigue Properties of Osteoporotic Thoracic Vertebral Bodies”. Spine, 30, pp. 645-650. (2005)
2. Domesticus, S. S. "Comparative Human/Porcine Anatomy". In Swine (Ed.): Monty Menhusen DVM MS DO. (2002)
3. McLain, R. F., Yerby, S. A., & Moseley, T. A. "Comparative Morphology of L4 Vertebrae". Spine, 27, pp. 200-206. (2002)
4. Ng, H. W., Teo, E. C., & Lee, V. S. "Statistical Factorial Analysis on the material Property Sensitivity of the Mechanical Response of the C4-C6 Under Compression, Anterior and Posterior Shear". Journal of Biomechanics, 37, pp. 771-777. (2004)
5. Rockoff, S. D., Sweet, E., & Bluestein, J. "The Relative Contribution of Trabecular and Cortical Bone to the Strength of Human Lumbar vertebrae". Calcified Tissue Internation, 3, pp. 163-175. (2005)
6. Cowin, S. C. "Mechanical Properties of Bone ": Amer Society of Mechanical. (1981)
7. Schaffler, M. B., & Jepsen, K. J. "Fatigue and Repair in Bone". International Journal of Fatigue, 22, pp. 839-846. (2000)
8. Rockoff, S. D., Sweet, E., & Bluestein, J. "The Relative Contribution of Trabecular and Cortical Bone to the Strength of Human Lumbar vertebrae". Calcified Tissue Internation, 3, pp. 163-175. (2005)
9. Cyron, B. M., & Hutton, W. C. "The Fatigue Strength of The Lumbar Neural Arch in Spondylosis". The Journal of Bone and Joint Surgery, 60B(2), pp. 234-238. (1978)
10. McCubbrey, D. A., Cody, D. D., Peterson, E. L., Kuhn, J. L., Flynn, M. J., & Goldstein, S. A. "Static and Fatigue Failure Properties of Thoracic and Lumbar Vertebral Bodies and Their Relation to regional Density". Jouranl of Biomechanics, 28(8), pp. 297-300. .(1995)
11. Ma, A., & P., D. "Time-dependent Change in the Lumbar Spine's Resistance to Bending". Clinical Biomechanics(Bristol, Avon), 11, pp. 194-200. (1996)
12. Tsai, K. H., Lin, R. M., & Chang, G. L. "Rate-related Fatigue Injury of Vertebral Disc Under Axial Cyclic Loading in a Porcine Body-Disc-Body Unit". Clinical Biomechanics(Bristol, Avon), 13, pp. 32-39. (1998)
13. Chow, D. H., Luk, K. D., Holmes, A. D., Li, X. F., & Tam, S. C. "Multi-planar Bending Properties of Lumbar Intervertebral Joints Following cyclic Bending". Clinical Biomechanics (Bristol Avon), 19(2), pp. 99-106. (2004)
14. Wang, J. L., Parnianpour, M., Shirazi-Adl, A., & Engin, A. E. "The Dynamic Response of L2/L3 Motion Segment in Cyclic Axial Compression Loading". Clinical biomechanics, 13, pp. 16-25. (1998)
15. Moore, T. L. A., & Gobson, L. J. "Fatigue of Bovine Trabecular Bone". Journal of biomechanical Engineering, 125, pp. 761-768. (2003)
16. Chen, P.-Q., Lin, S.-J., Wu, S.-S., & So, H. "Mechanical Performance of the New Posterior Spinal Implant: Effect of Material, Connecting Plate, and pedicle Screw Design". Spine, 28, pp. 881-887. (2003)
17. Aultman, C. D., Janessa, D. M., Drake, Callaghan, J. P., & McGill, S. M. "The Effect of Static Torsion of the Compressive Strength of the Spine". Spine, 29, pp. 304-309. (2004)
18. Dieen, J. H. V., & Veen, A. V. d. "Fatigue Failure in Shear Loading of Porcine Lumbar Spine Segments". Spine, 31(15), pp. 494-498. (2006)
19. Rapillard, L."Compressive Fatigue Behavior of Human Vertebral Trabecular Bone". Jouranl of Biomechanics, 39, pp. 2133-2139. (2006)
20. Parkinson, R. J. "Estimating the Compressive Strength of the Porcine Cervical Spine: An Examination of the Utility of DXA". Spine, 30(17), pp. 492-498. (2005)
21. F.H., N. "Atlas of Human Anatomy" (2nd ed.): ICON Learning System. (2002)
22. Belkoff, S. M. "An In Vitro Biomechanical Evaluation of Bone Cements Used in Percutaneous Vertebroplasty". Bone, 25(2), pp. 23-26. (1999)
23. Ching, C. T. S. "The Effect of Cyclic Compression on The Mechanical Properties of The Intervertebral Disc: An Iin Vivo Study In a Rat tail model". Clinical biomechanics, 2002(18), pp. 182-189. (2002)
24. J.F.Lafferty. "Fatigue Characteristic of Posterior Element of Vertebrae". The journal of Bone and Joint Surgery, 59, pp. 154-158. (1997)
25. 台灣脊椎中心. "Taiwanesespinecenter.com.tw".