| 摘要: | 近年來非骨融合式的腰椎手術的發展逐漸興起，該類手術主要目的是希望在提供腰椎穩定性的同時又不失活動度，且不會如骨融合手術一樣為不可逆的。在臨床上有許多不同型式的植入物被用於治療各種腰椎的病變並評估其使用效果，目前常使用的方法可分為臨床實驗、大體試驗，還有模擬分析，而有限元素法之所以廣泛被用於評估植入物對腰椎生物力學影響是因為於臨床上難以判定其植入後的受力情況。雖然現今已有多種的後路腰椎系統發行於市面上，但這些植入物本身還是存在些缺失，可能會因患者的骨質密度或材料性質造成限制而無法達到預期的效果。因此本研究著重的椎板間穩定器以及新型椎板間穩定器之設計相較先前的後路穩定器系統不會因材料性質的剛性過高導致代償或是限制前彎後仰等活動，使在臨床上獲得最大的效益並預防鄰近節退化的發生。
植體與椎骨間所撐起的椎體距離對腰椎生物力學的初期穩定度有一定的影響，然而沒有文獻針對腰椎植體撐起所帶來的初始穩定度進行評估並提出合理的椎間距離設定方式。因此本研究透過韌帶預力的設定方式來模擬臨床上於植體安裝後椎間距離撐起的情況，並給予不同撐高距離來做比較。
本研究建立了L3-L5節段的腰椎模型來進行有限元素分析，包括健康與退化兩種情況，進行人體腰椎生物力學指標分析，以觀察植入物對於腰椎之生物力學影響。
研究結果顯示，退化的腰椎會因椎間盤脫水以及椎間盤幾何形狀之變化造成退化節活動度降低與椎間受力逐漸轉移至纖維環上；鄰近節的活動度則因代償現象提升，進而增加椎間盤的受力。在無韌帶預力的設定下，本研究兩種椎板間穩定器可在腰椎的前彎及後仰活動度有限制，使鄰近節需代償的活動度提升；在椎間盤相關之指標則與健康腰椎相似，沒有明顯的減壓效果去表明出植體的支撐性。在有韌帶預力施加的設定下，兩種椎板間穩定器除了對前彎及後仰有限制外，還觀察到因PEEK材質加入之新型椎板間穩定器，其活動度之限制更多；由椎間盤相關之指標亦可看出新型椎板間穩定器更具加支撐性。整體而言，新型椎板間穩定器雖會降低植入節活動度約10%以內，但它具有較佳的支撐性，且對於鄰近節的影響較低。有限元素分析時若不考慮韌帶預力，則椎間的穩定性會被低估。本研究的限制包括採用等向性材料性質、韌帶預力作用位置與大小、還有未考慮肌肉受力等，這些問題皆需要進一步探討。
;In recent years, there has been a growing development of non-fusion lumbar spine surgeries. The main objective of these surgeries is to provide lumbar stability without compromising mobility, and they are reversible unlike fusion surgeries. In clinical practice, various types of implants are used to treat different lumbar pathologies and evaluate their effectiveness. Commonly evaluation methods include clinical trials, cadaveric experiments, and simulation analyses. The finite element method is widely used to assess the biomechanical effects of implants on the lumbar spine because it is difficult to determine the stresses of post-implants clinically.
Although there are various posterior lumbar spine systems available on the market, these implants still have some limitations. They may not achieve the desired function due to limitations imposed by material properties or patient-specific factors such as bone density. This study focuses on the design of pedicle-based stabilizers, including a new design, which aims to avoid excessive rigidity caused by material properties, compensation, or limitations on activities such as flexion and extension. The goal is to maximize clinical benefits and prevent adjacent segment degeneration.
The intervertebral distance induced by the implant has an impact on the initial stability of lumbar spine biomechanics. However, there is no literature that evaluates the initial stability resulting from implant support and proposes a reasonable method for setting the intervertebral distance. Therefore, this study compares the effects of intervertebral distance by simulating the intervertebral distance after implant installation using ligament preloading.
This study establishes a lumbar spine model of the L3-L5 segment for finite element analysis, including both healthy and degenerated conditions, to analyze the biomechanical performance of the human lumbar spine and the implants.
The results show that degenerated lumbar spines experience reduced segmental mobility and gradually transfer stresses to the annulus fibrosus due to dehydration and changes in intervertebral disc geometry. The mobility of adjacent segment increases due to compensatory phenomena, thus increasing the stresses on the intervertebral disc. Without ligament preloading, both pedicle-based stabilizer models restrict flexion and extension of the lumbar spine, leading to increased compensatory mobility in adjacent segments. The intervertebral disc-related indicators are similar to those of a healthy spine, with no significant decompression effect to indicate implant support. With ligament preloading, both stabilizer models can limit flexion and extension, and the addition of PEEK material in the new pedicle-based stabilizer results in more restriction on mobility. The intervertebral disc-related indicators demonstrate better support with the new stabilizer. Overall, the new pedicle-based stabilizer reduced the range of motion of the implanted segment by about 10%, but it had better support and less impact on adjacent segments. Intervertebral stability may be underestimated if ligament prestress is not considered in finite element analysis. Limitations of this study include the use of isotropic material properties, the location and magnitude of ligament preloading, and the absence of muscle forces, which need further investigation. |
