自行車踩踏時膝關節韌帶與軟骨受力之計算:座椅高低之影響

Abstract

自行車在現代人之日常生活中佔有很大的重要性，除了具有交通運輸、休閒娛樂及運動健身等功能外，在臨床上更被廣泛運用於下肢傷害之復健工具。而在進行復健之過程中很少會有人注意到座椅高度對於膝關節的影響。膝關節是下肢運動使用率最高的關節，除了肌肉自主收縮的控制外，韌帶與軟骨在不同運動狀態中更是扮演對關節穩定性的重要角色，因此關節軟組織的傷害是相當常見的。 由於電腦技術之快速演進，早期侵入式量測有諸多限制，因此有限元素法被大量運用在非侵入式量測活體膝關節軟組織力學的研究。有限元素分析的主要架構分別由幾何模型、材料參數以及邊界條件為三大主軸。客制化活體膝關節之幾何模型主要來自電腦斷層掃描與核磁共振造影之三維影像重建，韌帶與軟骨之材料參數分別根據KT-2000膝關節鬆弛度量測儀之量測實驗與文獻結果，邊界條件則為動態X光量測之膝關節骨頭相對運動學資訊。經由改良驗證過之有限元素分析流程，運用在活體自行車運動實驗下，探討不同座椅高度下自行車踩踏時韌帶與軟骨之負荷情形，並提供未來膝關節複雜力學分析之應用。 根據本研究分析之結果，在自行車運動過程中，軟組織主要負荷為後十字韌帶與內側軟骨面。韌帶負荷的分佈在膝關節伸直期遞減，膝關節彎曲期遞增；軟骨面負荷的分佈有兩個負荷峰值發生(大致上接近曲柄角度45度和300度)，最大接觸負荷為體重的1~2倍。在進行自行車運動之復健，座椅高度對於韌帶相對之影響較有限，反而是對於軟骨面之負荷有較大之影響；對於軟骨面之負荷在高座椅自行車踩踏時，在接近上死點時有較多軟骨面之貢獻。由臨床角度來看，對於前十字韌帶受損之患者較推薦以高座椅之踩踏方式進行復健，但不建議後十字韌帶損傷之患者使用此復健方法；而對於軟骨面損傷之患者較推薦將座椅高度降低進行此復健，但需額外注意內側軟骨之受力，避免過多負載。

Cycling plays an important role in our daily life. It is also widely applied to the rehabilitation of the lower limb, but it is seldom being discussed of how the seat heights effect the knee. The knee ligaments and articular cartilages have a great influence on the knee joint stability and mobility. Knee joint is the highly used hinge joint in the human body, and its injuries to soft tissues is occurred commonly. Finite element method is widely used to study in vivo joint soft tissue mechanics in the non-invasive measurement. Geometry model, material parameters of soft tissues and boundary condition composed the whole finite element method. The geometry model comes from the three-dimensional reconstruction of the computed tomography and magnetic resonance imaging scan. Material parameters of soft tissues referred to the KT-2000 arthrometer and literature. The boundary condition is captured from the dynamic fluoroscopy system. The objective of this study was to analyze the loading of the in vivo knee ligaments and articular cartilages in different seat heights with the validated finite element analysis procedure, hoping to provide a better used of mechanical analysis of the complicated soft tissues in knee in the future. According to the finite element analysis results in cycling, the main representative of the loadings in soft tissues were PCL and the medial cartilage. The ligament loadings decrease along of the knee extension and increase along of the knee flexion. The articular cartilage loadings show two peaks among crank angle of 45° and 300° and the maximum contact load is 1-2 times of the body weight. While cycling, the effect of seat height is limited in ligament loadings but more in the cartilage loadings. In the high-seated pedaling, articular cartilages had contributed more near the top dead end of the pedaling cycle. From the clinical point of view, the patients with ACL injury are recommended to pedaling with the high seat but the patients with PCL injury are not appropriated for this rehabilitation. And the low-seated pedaling is suitable for the patients with knee osteoarthritis but be aware of the loadings of the medial cartilage.