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研究生:張偉龍
研究生(外文):Chang, Wei-Lung
論文名稱:椎骨融合與人工椎間盤之數值模擬
論文名稱(外文):Numerical modeling of spinal fusion and artificial disc
指導教授:楊世偉楊世偉引用關係
指導教授(外文):Yang, Sai-Wei
學位類別:碩士
校院名稱:國立陽明大學
系所名稱:醫學工程研究所
學門:工程學門
學類:生醫工程學類
論文種類:學術論文
論文出版年:1994
畢業學年度:82
語文別:中文
中文關鍵詞:醫學工程人工椎間盤
外文關鍵詞:MEDICAL-ENGINEERING
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本研究以有限元素分析軟體 ANSYS 5.0,首先以一 L4-L5脊椎單元模型,模擬在無後部元素(棘突、椎弓板)等條件下其與類似條件之實驗結果,以求得較符合人體脊椎單元之各部材料性質 ,及幾何形狀等參數。再利用這些數值分析L1-L5整體腰椎在壓力,扭力,及前後彎曲等生理負荷下運動與力學效應,並模擬髓核退化,及割除後以人工椎間盤植入及椎骨融合後對整體腰椎運動量與應力分佈的影響。
結果顯示,在軸向壓力下,關節面所分擔之負荷很小。軸向壓力大部份為椎間盤所承受,且最大等效應力集中於椎間盤後部(posterior)。除了軸向位移外,亦產生偶合運動,即向後位移及後仰(extension)。作用力的中心線、椎體之幾何中心,及脊椎之前彎角度(lordosis)與應力的分佈、運動量有很大的關係。
在整體脊椎(L1-L5)模擬中,偶合運動更加明顯。除了軸向位外,各椎節之運動以L1-L2最大,L2-L3次之,且依次遞減。在壓力一扭力負荷模式下,脊椎為螺旋運動:除軸向旋轉外亦伴隨向左側彎曲與後仰。
在軸向壓力負荷下應力集中於椎間盤後部,且靠近上端骨端板處為張力;在壓力一扭力負荷模式下應力則集中於兩後側(posto-lateral),且扭轉方向而異。
L3-L4椎間盤斬傷後,並未明顯改變整體之運動量,但在L3-L4與鄰近椎體的應力分佈則有較大的變化;而主要的運動增量為發生傷之椎間盤,但上接之椎間盤(L2-L3)運動量增加,應力亦增大;而下接椎間盤(L4-L5)之運動量相對減少,應力亦較低。
在加入不同骨植片後應力均集中於骨植片處,而整體脊椎與椎間盤的應力並無多大分別。各椎節的位移量除L4-L5外其餘均增加,且以L3-L4增加量最大。在L3-L4椎骨融合中,L4-L5椎節的軸向位移與扭轉度以中央骨融合最小,而前方植入者最大;但中央骨融合L2-L2與L2-L3之運動量則增加。這顯示中央骨融合有較佳的穩定性,但造成鄰近椎骨的應力與運動量增加。相對地,人工椎間盤則提供類似正常脊椎的應力分佈,而各椎節的運動量略大於正常者
在壓力與壓力一扭力作用下,各椎節之受力並不相同。主要為偶合作用與脊柱前彎的效應,其作用力在L-L5節最大,但L3-L4節最小;而韌帶之受力以前長軸韌帶最大,後長軸韌帶最小,且在L3-L4椎間盤傷時其韌帶受力增加;而後方骨植片植入間接減少了各組韌帶的受力,然還是以人工椎間盤較接近於正常脊椎。因此人工椎間盤似乎提供了兼顧脊柱穩定性與應力集中消除的效應。
A ligarnentous lumbar spine L1-L5 was modeled and analyzed by Finite Elementpackage ANSYS 5.0. Functional unit with and without posterior elements were analyzed first to validate the mechanical properties and geometric dimension with the experimental results. The unit model was then expended anatomically to LI-L5 portion of lumbar spine and analyzed under physiological loading condition: axial compression and compression - torsion, in five tasks named normal condition, nucleus disection, anterior bone graft fusion, interbody ftision, posterior ftision.
The results showed under axial loading, the facet joints shared only few axial load andmost of forces were carried by spinal disc. And coupling motion was detected. The action line offeree, geometric center of spin model, and degree of lordosis highly affected the stress distribution and motion of spin column. The coupling effect was more obviously in LI-L5 ligarnentous model. Under axial compression loading largest axial displacement was in L1-2 segment and decreased linearly in the down under segments. In axial compression-torsion loading a screw motion was found with a largest rotation in L1-2 and then L4-5 segment. The stresses were concentrated in posterior region of disc and tensile stresses were in postolateral side of juction of outermost area of annulus laminate and end-plate. In compression-torsion loading the stresses were concentrated in postolateral region and changed following the direction of twist.
In the case of nucleus disection simulation, the increase of motion was mainly in where the lesion was (L3-4)and the movement in L4-5 was decreased. AFter bone-grafting the stresses were concentrated in where bone grafted, the distribution of stress was similar to the normal case. The movements in L4-5 segment was decreased in all abnormal cases and increased in other segments with more motion in L3-4. Among the bone-grafting techniques the interbody fusion showed the more stable effect in L3-4 and anterior fusion was the worst. But the less motion in L3-4 resulted in increasing of stress and motion in other segments. In other hand artificial disk provided similar stress distribution as normal spine but slight increase in movements.
Due to the effect of lordosis load on the spinal disc is different segment by segment L4-5 suffered the highest resultant force while L3-4 was minimum. Ligamnet took partial of load anterior longitudinal ligament shared about 15% of applied force and posterior longitudinal ligament took less amount of force. After bone grafting the force in each ligament was decreased.
The decrease of motion resulted in increase in motion and stress in one above motion segment. The artificial disc provided a solution for similar motion and stress distribution characters as normal spine does.



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