功能性活動中膝關節韌帶之三維有限元素模擬與分析

Abstract

膝關節在人體的活動中扮演重要的角色。關節周邊的肌肉、韌帶、軟組織、及關節面之間複雜的力學交互作用決定了膝關節的活動。其中，膝關節韌帶連結了股骨、脛骨、以及腓骨以維持膝關節的穩定，在膝關節活動的過程中也承受拉力。膝關節在人體運動的過程中易承受較大的力量，因此其韌帶也是傷害經常發生之處。根據過去的研究發現，膝關節的傷害中比例最高的就是韌帶的傷害，其中前十字韌帶的受傷比例高達85% 。膝關節的傷害對於生活的活動影響很大，尤其運動員和老人更是如此。因此研究人體活動時膝關節韌帶所承受的力量變一直是一項重要的課題。 過去有許多研究膝關節運動以及力學的文獻，使得人們對於其韌帶的受力情形有初步的了解。試體研究中，學者們利用膝關節的前拉測試求得膝關節在被動力量下的形變。活體研究雖然在臨床應用上極為重要，但在實際執行上有許多限制，因此學者多以電腦模型來求韌帶受力。拜電腦科技進步之賜，許多研究皆已使用有限元素法來建立三維膝關節模型，有效的計算膝關節生物力學。 以往的膝關節有限元素分析主要以膝關節的拉伸測試為主，缺乏功能性動作之分析，例如：走路、上下樓梯等。然而，這些動作卻是膝關節主要的功能以及膝關節重建手術所關注的焦點。因此本研究以三維膝關節韌帶模型，經由有限元素法來分析其韌帶在活體功能性活動中的應力分佈及受力情形。韌帶之材料特性假設橫向同性及不可壓縮的超彈性體，並使用動態X光影像比對技術來求得膝關節的運動學資訊。此非侵入式的韌帶模擬會利用試體實驗來驗證準確度，最後應用在臨床上，模擬活體膝關節韌帶在功能性動作中韌帶的受力。

Knee joints play very important roles in human activities. The muscles, ligaments, soft tissue, and joint surfaces surround knees decide the kinematics of knees. Ligaments link a femur and a tibia, limiting the motion of the knee. During human activities, knee ligaments also sustain tensile forces. The knee is commonly injured tissue while people apply improper forces to them during sport or daily activities. It is reported that the injuries in ligaments have the highest percentage of the injuries in knees. 85% percent of ligament-injury happened in anterior cruciate ligament. Therefore, people tried hardly to understand how ligaments take forces during body motions. There were many researchers related to kinematics and kinetics of knee. According cadaveric research, researchers use the anterior draw test to realize the force and deformation of knee. In vivo researches have many limits, so reconstructing a computer model is common for calculating the force of ligaments. Due to the envelopment of computer, finite element methods have been a useful method to realize the biomechanics of knee. The objective of this study was to calculate the stress distribution and the force of the in vivo knee ligaments through the use of a 3-D finite element method of the ligaments during the functional activities of knee. The ligaments of the knee were simulated as incompressible transversely isotropic hyperelastic materials. The dynamic information of the femur and tibia can be obtained through 3-D surface model to 2-D fluoroscopy image registration for the boundary condition of FEA. The finite element models of knee ligaments were validated by specimen experiments which were performed by laxity test using 6-degree robotic system.