頸椎前位椎間盤切除與骨融合手術(ACDF)是一種常見的手術，其常用於治療人體頸椎退化或神經根減壓，但是頸椎融合手術可能會造成手術節的活動度喪失，進而造成鄰近節脊椎之退化問題。因此，為了保留頸椎的活動度，許多動態裝置不斷的被研究，例如:人工椎間盤置換手術(ADR)，其手術方式為將退化的椎間盤去除，並植入人工椎間盤作取代，此方法能有效的減輕疼痛與回復原本椎體活動度，針對以上這兩種手術方式，過去有許多學者使用有限元素模型，分析頸椎融合手術與人工椎間盤置換術之生物力學性能，但是他們的數值模型較簡化，此可能造成結果的可信度較低。因此本研究希望透過較完整且公平的數值模擬方法，評估傳統骨融合手術與人工椎間盤置換術之生物力學性能，以供臨床醫師作參考。
本研究建立三維非線性有限元素頸椎模型C1-T2，並使用有限元素分析軟體ANSYS Workbench作為評估工具，而所有模型的約束條件皆設在模型底部(T2)，並模擬頸椎C5-C6 椎間盤發生退化情形，本研究建立三種頸椎模型，包含：完整頸椎、頸椎前位椎間盤切除與骨融合手術、人工椎間盤置換術，三種模型分別施以前彎、後彎、側彎、旋轉之運動，找出手術後其手術節與鄰近節之生物力學結果，例如:頸椎整體活動度、頸椎各椎節活動度與椎間盤總應變能。
數值分析結果顯示，頸椎前位椎間盤切除與骨融合手術的活動度在手術節為減少，但在鄰近節為增加，這代表著頸椎融合手術穩定度較高，此外，手術鄰近節的椎間盤總應變能亦會增加，此會增加鄰近節退化的風險；而頸椎人工椎間盤置換術可維持手術節的活動度，且在手術鄰近節的活動度與椎間盤總應變能較接近完整頸椎，此可降低鄰近節退化的風險。因此，本研究所使用之多節段C1-T2三維非線性有限元素模型，將可有效的分析頸椎融合手術與人工椎間盤置換術之生物力學結果。

Anterior cervical discectomy and fusion is a common surgical procedure to treat spinal degeneration or nerve root compression. However, adjacent segment degeneration has been generally accepted as a long-term complication after spinal fusion surgery. Alternatively, motion preservation devices such as artificial discs can be used to restore motion and maintain mobility of the involved cervical spinal segments. In the past, researchers have tried to develop finite element models and/or biomechanical tests to compare the biomechanical performances of both anterior cervical plate and cervical artificial disc. However, their numerical models were oversimplified. Therefore, the purpose of this study was to investigate the biomechanical performances of both anterior cervical plate and cervical artificial disc for the treatment of cervical disc disease.
Three-dimensional nonlinear finite element models were developed to investigate the biomechanical performances of C1-T2 multi-level segments with either anterior cervical plate system or cervical artificial disc by using ANSYS Workbench. All numerical models were constrained at the bottom of the T2 vertebra and subjected to a body weight under physiological motions. Disc degeneration was simulated at C5-C6 level. The loading case of flexion, extension, lateral bending and axial rotation were simulated. In addition, in order to evaluate the biomechanical performances of the different surgical techniques, range of motion in cervical spine, intersegmental rotation of cervical spine, and total strain energy of intervertebral discs were calculated.
The numerical results showed that anterior cervical plate system reduced the motion at index level and increased the motion at the adjacent level. This meant that anterior cervical discectomy and fusion surgery had higher risk of developing adjacent segment degeneration. Compared with the anterior cervical discectomy and fusion surgery, cervical artificial disc replacement revealed no adjacent-level instability, but instability was found at the surgical level. The biomechanical performances of the C1-T2 multi-level spine with either anterior cervical plate system or cervical artificial disc could be effectively analyzed using three-dimensional nonlinear finite element analyses and applied to study other problems.

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