脊椎是人體中最重要的構造之一，當椎體或椎間盤受到損害後，通常需進行脊椎椎體置換手術(Vertebral body replacement)，藉由手術將受損椎體或椎間盤移除，取而代之的是人工椎體支撐器(Vertebral body cage)，然而單純的植入人工椎體支撐器並無法產生足夠的穩定效果，通常需再加上脊椎內固定器(Spinal fixator)，使椎體能在穩定的狀態下產生骨融合，在內固定器裡，椎弓根骨螺絲(Pedicle screw)扮演著內固定器與椎體之間連接的橋樑，內固定器是否穩定，骨螺絲為最重要之因素，然而對於患有骨質疏鬆之病患，單純的鎖入椎弓根骨螺絲並不能提供足夠的穩定，原因來自於病患的骨密度值太低，因此，若能提高骨螺絲與椎體間介面強度，將可達到穩定椎體的效果。椎體成形術(Vertebroplasty)為在脆弱或有骨折之椎體內部注射骨水泥(Bone cement)，進而達到強化或修復椎體的一種手術，當骨螺絲植入於椎體內部時，骨螺絲與椎體間介面咬合強度亦會隨著椎體強化進而提升。
本研究將從生物力學實驗及有限元素法評估三種不同的中空椎弓根骨螺絲植入技術，第一種為單純植入椎弓根骨螺絲，且不使用骨水泥強化(Control)，第二種為先使用注射器注入PMMA骨水泥於椎體內部，隨後植入椎弓根骨螺絲(Vertebroplasty)，第三種為先植入椎弓根骨螺絲，隨後從骨螺絲頭部使用注射器注入PMMA骨水泥(Vertebroplasty)。在生物力學實驗上，本研究為了使研究結果更加接近臨床情況，因此將採用人類胸腰椎大體試片進行椎弓根骨螺絲拉出實驗。
研究結果顯示，先將骨水泥注入於椎體內部，再植入椎弓根骨螺絲之植入技術，不管在拉出強度、最大拉出強度的位移量(δps)及總吸收能量上，都擁有最佳的生物力學特性，而數值分析之結果也與實驗結果趨勢一致，因此，本研究建議在患有骨質疏鬆症且需進行椎弓根骨螺絲植入之病患，使用第二種的植入技術是為最有效穩定椎體的手術方法。

The vertebral column is one of the most important structures in the human body. When the vertebrae body or the intervertebral disc has been damaged, a vertebral body replacement surgery is usually needed. Therefore, through this kinds of surgery, the damaged vertebrae body or intervertebral disc will be removed, and replacing it with the vertebral body cage. However, simply implanting the vertebral body cage could not adjust the stability of the fusion segment, in which, the supplementary pedicle screw fixation has been widely used for increasing rigidity of spinal implant construct, in order to produce the bone fusion under the stabilized motion segment. If the vertebral bodies are affected by osteoporosis, the general pedicle screws are unable to apply enough screw-bone interface strength for osteoporotic bodies, and high risks resulted from loosening or failure of the fixation systems. In this case, if the screw-bone interface strength can be increased, thus, the effect of stability can be facilitated. The vertebroplasty, a kind of surgery which helps facilitate or repair the vertebrae body through injecting bone cement into the weaker or the fracture part of the vertebrae body, is performed. Thus the bone holding power of vertebrae body and the pedicle screw will gradually increase when the pedicle screw is implanted.
Biomechanical tests and the finite element method will be used and discussed on assessing three different types of implantation of cannulated pedicle screw in this research. The first type is simply implant the pedicle screw into the vertebrae body without using the bone cement for facilitation. In the second experiment, the syringe will be used to inject PMMA bone cement into the vertebrae body first, and then inject the cannulated pedicle screw. The cannulated pedicle screw is implanted first then the PMMA bone cement is injected from the pedicle screw in the third experiment. To make these biomechanical tests more clinical for this research, therefore, the human thoracolumbar specimens are being used to progress in the pedicle screw pull out experiment.
The result had shown that injecting the PMMA bone cement into the vertebrae body first, then implanting the cannulated pedicle screw, had the best biomechanical performance including the pull out strength, the displacement at maximal strength, and the total energy absorption. Therefore, the best implantation of the pedicle screw for osteoporosis patients will be suggested to use the second type of the implantation for stable vertebrae body surgery.

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