臺灣博碩士論文加值系統

人工髓核置換為治療椎間盤退化病症中，較新的手術方式。針對罹患慢性下背痛之病患而言，人工髓核置換之目的為恢復椎間盤高度、改善椎節活動度及紓緩疼痛感。目前人工髓核廣泛的使用水凝膠作為材料，且其力學特性也是基於孔洞彈性雙相理論。雖然過去有些人工髓核相關的模擬研究是使用雙相模型，但大多數的人工髓核有限元素分析，將固相假設為線彈性，且忽略固相基質與內在流體之交互作用。這樣的假設下，難以預測潛變之特性。因此，本研究之目的為建構孔洞彈性有限元素模型，並且評估椎間盤於不同退化程度與人工髓核置換後，對於其生物力學特性的影響。此外，本研究亦會評估水凝膠式人工髓核的彈性模數與初始滲透率之材料參數變異，對於椎間盤力學特性之影響。
本研究建構正常腰椎L4-5活動元之孔洞彈性有限元素模型，其後藉由修改椎間盤材料參數，模擬三種不同椎間盤退化程度(Grade II, III and IV)，並於椎間盤退化模型中模擬人工髓核置換術。此外，本研究探討人工髓核兩種材料參數(彈性模數與初始滲透率)和兩種數值變異(高與低)。各組模型分析結果將評估於日常生活的壓縮負載中，椎間盤高度變化量、椎間盤流體損失率、髓核孔洞壓力消散率、後側環狀基質有效應力和後側環狀基質有效應力變化率等參數之變化。
研究結果顯示，椎間盤高度變化量及椎間盤流體損失率會隨著椎間盤退化程度增加而減少，而髓核孔洞壓力消散率、後側環狀基質有效應力及後側環狀基質有效應力變化則會隨著椎間盤退化程度增加而增加。此現象可能導致後側環狀基質有較高的破壞風險。相較於椎間盤退化的模型，人工髓核置換僅些微影響髓核孔洞壓力消散率、後側環狀基質有效應力及後側環狀基質有效應力變化率。人工髓核材料參數變異置換於椎間盤退化模型中，發現彈性模數對於髓核孔洞壓力消散率及後側環狀基質有效應力變化率無明顯的影響。然而，減少人工髓核初始滲透率(由2.51 E-11 m4/Ns減少至0.3 E-15 m4/Ns)，能顯著的降低髓核孔洞壓力消散率及後側環狀基質有效應力變化率，可減低椎間盤退化造成後側環狀基質破壞之風險。總結上述相關分析結果，發現於Grade II椎間盤退化模型中，使用較低彈性模數(0.45 MPa)與較低初始滲透率(0.3 E-15 m4/Ns)之人工髓核，具有與正常椎間盤相似之生物力學特性。

Nucleus pulposus (NP) replacement is a newer surgical procedure for degenerative disc disease (DDD). The goal of NP replacement is to restore disc height, improve mobility and reduce pain in patients with chronic low-back pain. Currently, the most widely used materials in NP replacement are hydrogels, and the mechanical behavior can be characterized based on biphasic poroelastic theories. However, there are few published studies on the simulation of NP replacement using the biphasic model. In most FE studies of NP replacement, the solid phase was assumed to be linear elastic, which neglected the interaction between the internal fluid and the solid matrix of the polymer network. It was noted that this assumption may result difficulties in predicting creep behavior. Therefore, the objective of this study was to create a poroelastic finite element (FE) model and to evaluate the biomechanical effects following different grades of disc degeneration as well as the effects of subsequent nucleus replacement. Furthermore, the elastic modulus and initial permeability of the hydrogel nucleus replacement device (NRD) was varied to understand the effects of NRD material parameters on the mechanical behavior of the disc.
The intact poroelastic FE model of a human L4-5 motion segment was developed and modified to simulate three different grades of disc degeneration (Grade II, III and IV) with or/and without a NRD. In addition, the study investigated two material properties (elastic modulus and initial permeability) of NRD at two levels (high and low). The daily disc height variation, the rate of fluid loss from the disc, the rate of dissipation of pore pressures in the nucleus (RDPPN), the effective stress in the posterior annulus (ESPA), the ratio of change in effective stress in the posterior annulus (RESPA) were assessed in all FE models under loading-recovery daily compression.
With increasing disc degeneration, the daily disc height variation and the rate of fluid loss from the disc decreased. In contrast, the RDPPN, ESPA, and RESPA increased with increasing disc degeneration. This change may induce a higher fracture risk in the posterior annulus matrix. Subsequently, compare to the disc degeneration models, only a slight effect of nucleus replacement on the RDPPN, ESPA, and RESPA. For the degeneration models with varied material properties of NRD, RDPPN, and RESPA were not significantly influenced by the elastic modulus. Moreover, the reductions of the RDPPN and RESPA were much more pronounced with reducing the initial permeability (form 2.51 E-11 to 0.3 E-15 m4/Ns) of the NRD, which can in turn reduce the risk of damage in the posterior annulus matrix. In conclusion, the biomechanical behavior of the Grade II disc degeneration model with the NRD (lower elastic modulus of 0.45 MPa and lower initial permeability of 0.3 E-15 m4/Ns) was similar to that of the natural disc behavior.

摘 要 i
ABSTRACT iii
誌謝 vi
目 錄 vii
表目錄 x
圖目錄 xi
第一章 緒論 1
1.1前言 1
1.2 研究背景 2
1.2.1腰椎解剖學 2
1.2.2椎間盤解剖學及力學特性 4
1.2.3椎間盤退化 5
1.2.4融合與非融合手術 6
1.3人工髓核 6
1.3.1硬植體 (Solid implant) 7
1.3.2軟植體 (Soft implant) 8
1.4文獻回顧 11
1.4.1臨床表現相關文獻 11
1.4.2體外實驗相關研究 13
1.4.3有限元素分析相關研究 15
1.5研究目的 19
第二章 材料與方法 20
2.1研究流程 20
2.2有限元素模型建構 21
2.3模型規劃 22
2.4材料參數設定 22
2.4.1腰椎活動元 22
2.4.2人工髓核植體 26
2.5邊界條件與接觸條件設定 26
2.5.1邊界條件設定 26
2.5.2接觸條件設定 27
2.6評估參數 28
2.6.1椎間盤高度變化量 28
2.6.2椎間盤流體交換率(Fluid exchange) 28
2.6.3髓核孔洞壓力消散率(Pore pressure dissipation ratio) 29
2.6.4後側環狀基質有效應力(Effective stress) 29
2.7有限元素模型收斂測試 30
第三章 結果 31
3.1有限元素模型驗證 31
3.2椎間盤退化之影響 32
3.2.1椎間盤高度變化量 32
3.2.2椎間盤流體交換率 32
3.2.3髓核孔洞壓力消散率 33
3.2.4後側環狀基質有效應力 34
3.3人工髓核置換之影響 35
3.3.1椎間盤高度變化量 35
3.3.2椎間盤流體交換率 36
3.3.3髓核內孔洞壓力 38
3.3.4後側環狀基質有效應力 39
3.4人工髓核材料參數變異之影響 40
3.4.1椎間盤高度變化量 40
3.4.2椎間盤流體交換率 42
3.4.3髓核內孔洞壓力 43
3.4.4後側環狀基質有效應力 45
第四章 討論 47
4.1椎間盤高度變化量之探討 47
4.1.1椎間盤退化之影響 47
4.1.2人工髓核置換之影響 49
4.1.3人工髓核材料參數變異之影響 49
4.2椎間盤流體交換率之探討 50
4.2.1椎間盤退化之影響 50
4.2.2人工髓核置換之影響 50
4.2.3人工髓核材料參數變異之影響 51
4.3髓核孔洞壓力之探討 51
4.3.1椎間盤退化之影響 51
4.3.2人工髓核置換之影響 52
4.3.3人工髓核材料參數變異之影響 52
4.4後側環狀基質有效應力之探討 53
4.4.1椎間盤退化之影響 53
4.4.2人工髓核置換之影響 53
4.4.3人工髓核材料參數變異之影響 54
4.5有限元素分析限制 55
第五章 結論 56
參考文獻 57

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