股骨頭缺血性壞死(Avascular necrosis，AVN)是人體髖關節常發生的病變之ㄧ，而此病變會造成股骨頭所能承受負載的能力下降，而導致塌陷(Collapse)。使用有限元素模擬(Finite Element Method，FEM)可預先評估股骨頭缺血性壞死的力學分佈情形，並提供臨床診斷治療上的參考。本研究利用三維有限元素法模擬股骨頭缺血性壞死體積大小及壞死位置，對於壞死區域、健康骨質及壞死區域與健康骨質交界面上之應力分佈，以力學觀點解釋臨床上股骨頭缺血性壞死之現象，以了解股骨頭缺血性壞死體積大小及壞死位置對於未來股骨頭塌陷的風險程度評估。本研究建立骨盆、軟骨及股骨之有限元素模型並進行收斂測試及模型驗證，證明此模型分析結果之合理性與可靠度。

在模擬股骨頭壞死組態上，利用圓錐體模擬之結果顯示，當壞死體積越大及壞死位置位於上側（Superior）時，其壞死區域內及壞死骨質與健康骨質之介面上平均von Mises stress值較大，代表壞死體積越大塌陷風險越大且壞死區域容易擴張。然而，真實的壞死形狀並非規則，利用圓錐體模擬並不能充分反應出實際情況。因此，本研究更進一步利用隨機選取方式模擬壞死區域來克服上述問題，其模擬結果發現壞死體積相同但塌陷風險差異大，若壞死體積成倍數增加，其塌陷風險也未加倍，由此可知對於塌陷風險而言，壞死位置扮演著比壞死體積更為重要的角色。

Avascular necrosis (AVN) of the femoral head is a common disease in human hip. The mechanical performance of necrotic region and the ability of load bearing of femoral head are seriously affected when AVN occurred. This may further induce the bone fracture or collapse. Even with so many researches working on this topic, the underlying biomechanical responses of AVN femoral head are still unclear due to the limitations of the many existing researches. Hence, the objective of this research was to evaluate the mechanical responses of the femoral head with avascular necrosis with various necrotic sizes and locations by emphasizing on a more realistic loading mode. The research established 3D finite element models which included not only femur but also pelvis and cartilages for loading applying. To validate the simulation model, experimental results form other study were employed for comparison.

With the necrotic region modeled as cone shape, the traditional approach, the results showed that with the increasing of necrotic size or the region is located more superior, both the average von Mises stress within the necrotic region as well as the interface stress between necrotic region and normal bone increased, which indicated higher risk of collapse and necrotic region expanding. However, when the necrotic region was modeled by random growing, the results showed that the increasing of necrotic volume dose not have significant effect on the collapse risk while the necrotic shape or location play a more important role in the biomechanical response of an AVN femoral head.

1. Kerboul M, Thomine J, Postel M, Merle D'Aubigne R. The conservative surgical treatment of idiopathic aseptic necrosis of the femoral head. J Bone Joint Surg Br 56: 291-6, 1974.

2. Mont MA, Hungerford DS. Non-traumatic avascular necrosis of the femoral head. J Bone Joint Surg Am 77: 459-74, 1995.

3. Mont MA, Jones LC, Einhorn TA, Hungerford DS, Reddi AH. Osteonecrosis of the femoral head. Potential treatment with growth and differentiation factors. Clin Orthop Relat Res 355 Suppl: S314-35, 1998.

4. Nishii T, Sugano N, Ohzono K, Sakai T, Sato Y, Yoshikawa H. Significance of lesion size and location in the prediction of collapse of osteonecrosis of the femoral head: a new three-dimensional quantification using magnetic resonance imaging. J Orthop Res 20: 130-6, 2002.

5. Imhof H, Breitenseher M, Trattnig S, Kramer J, Hofmann S, Plenk H, Schneider W, Engel A. Imaging of avascular necrosis of bone. Eur Radiol 7: 180-6, 1997.

6. Marieb , Mallatt , Wilhelm. HUMAN ANATOMY. Fourth edition

7. 沈清良著, 實用解剖學, 第3版, 華杏出版社

8. Brown TD, Way ME, Ferguson AB, Jr. Mechanical characteristics of bone in femoral capital aseptic necrosis. Clin Orthop Relat Res 156: 240-7, 1981.

9. Ueo T, Tsutsumi S, Yamamuro T, Okumura H, Shimizu A, Nakamura T. Biomechanical aspects of the development of aseptic necrosis of the femoral head. Arch Orthop Trauma Surg 104(3): 145-9, 1985.
10. Daniel M, Herman S, Dolinar D, Iglic A, Sochor M, Kralj-Iglic V. Contact stress in hips with osteonecrosis of the femoral head. Clin Orthop Relat Res 447:92-99, 2006.

11. Mont MA, Marulanda GA, Jones LC, Saleh KJ, Gordon N, Hungerford DS, Steinberg ME. Systematic analysis of classification systems for osteonecrosis of the femoral head. J Bone Joint Surg Am 88 Suppl 3:16-26, 2006.

12. Volokh KY, Yoshida H, Leali A, Fetto JF, Chao EY. Prediction of femoral head collapse in osteonecrosis. J Biomech Eng 128: 467-70, 2006.

13. Steinberg ME, Steinberg DR. Classification systems for osteonecrosis: an overview. Orthop Clin North Am 35: 273-83, 2004.

14. Steinberg ME, Hayken GD, Steinberg DR. A quantitative system for staging avascular necrosis. J Bone Joint Surg Br 77: 34-41, 1995.

15. Steinberg ME, Bands RE, Parry S, Hoffman E, Chan T, Hartman KM. Does lesion size affect the outcome in avascular necrosis? Clin Orthop Relat Res 367: 262-71, 1999.

16. Steinberg DR, Steinberg ME, Garino JP, Dalinka M, Udupa JK. Determining lesion size in osteonecrosis of the femoral head. J Bone Joint Surg Am 88 Suppl 3:27-34, 2006.

17. Koo KH, Kim R. Quantifying the extent of osteonecrosis of the femoral head. A new method using MRI. J Bone Joint Surg Br 77: 875-80, 1995.

18. Yang JW, Koo KH, Lee MC, Yang P, Noh MD, Kim SY, Kim KI, Ha YC, Joun MS. Mechanics of femoral head osteonecrosis using three-dimensional finite element method. Arch Orthop Trauma Surg 122: 88-92, 2002.

19. Lee MS, Tai CL, Senan V, Shih CH, Lo SW, Chen WP. The effect of necrotic lesion size and rotational degree on the stress reduction in transtrochanteric rotational osteotomy for femoral head osteonecrosis--a three-dimensional finite-element simulation. Clin Biomech (Bristol, Avon) 21: 969-76, 2006.

20. Malizos KN, Siafakas MS, Fotiadis DI, Karachalios TS, Soucacos PN. An MRI-based semiautomated volumetric quantification of hip osteonecrosis. Skeletal Radiol 30: 686-93, 2001.

21. Wen Xue, Wang K, Ling W. Three-dimensional finite element analysis in the treatment of adult femoral head necrosis using different graft. Journal of Nanjing Medical University 20: 55-58, 2006.

22. Ferguson SJ, Bryant JT, Ganz R, Ito K. The influence of the acetabular labrum on hip joint cartilage consolidation: a poroelastic finite element model. J Biomech 33: 953-60, 2000.

23. Hsu JT, Lai KA, Chen Q, Zobitz ME, Huang HL, An KN, Chang CH. The relation between micromotion and screw fixation in acetabular cup. Comput Methods Programs Biomed 84: 34-41, 2006.

24. 呂元喬, 逆行性骨髓內釘之生物力學分析, 國立成功大學醫學工程所碩士論文2003

25. 羅世瑋, 缺血性壞死股骨頭轉骨術之三維有限元素模擬, 私立中原大學醫學工程學系碩士論文2002

26. Wei HW, Sun SS, Jao SH, Yeh CR, Cheng CK. The influence of mechanical properties of subchondral plate, femoral head and neck on dynamic stress distribution of the articular cartilage. Med Eng Phys 27: 295-304, 2005.

27. Mann KA, Bartel DL, Wright TM, Burstein AH. Coulomb frictional interfaces in modeling cemented total hip replacements: a more realistic model. J Biomech 28: 1067-78, 1995.

28. Downey DJ, Simkin PA, Taggart R. The effect of compressive loading on intraosseous pressure in the femoral head in vitro. J Bone Joint Surg Am 70: 871-7, 1988.