以數位影像相關法與機械手臂系統研究距下關節固定術對踝關節面之生物力學影響

Abstract

在人體各關節中，踝關節扮演了重要的腳色，幫助人體在行走或站立時維持穩定。而踝關節關節炎是常見的足部疾病。關節炎為軟骨面因為使用過度或運動傷害等原因，造成軟骨面的破損，使得關節疼痛影響了生活。若能直接量測軟骨在受力後的變形，將更進一步地了解關節炎的發生原因。 因此，本研究的出發點為瞭解關節面的力學特性，以及為了協助傷患的復健，探討關節內軟組織，尤其是距下關節骨融合後最容易受傷的踝關節面，在不同運動情形之下的力學分佈，與韌帶變形的交互作用。本研究的研究目的在於建構一方法，以量測關節軟骨在受力時的變形量。而本研究以人體踝關節為研究對象，試著了解在受拉伸試驗下踝關節韌帶與踝關節關節面的交互作用，並進行距下關節骨融合術，以觀察手術前後對踝關節關節面的影響。 本研究成功建構一方法，結合了三維全域變形及應變量測系統、醫學影像處理，以及機械手臂系統，可計算出關節軟骨厚度分布與其覆蓋面積，並可量測關節運動時各骨頭之運動學資訊，進而算出其關節軟骨於動態過程中之全域變形分布與周遭韌帶之表面應變分布。 本研究之對象為三具踝關節試體。試體先請骨科醫師處理，並在欲量測表面鋪上黑色粉末。將處理完之試體固定於機械手臂系統上，進行不同角度之拉伸試驗，同時進行兩台相機的同步拍攝。之後請骨科醫師進行距下關節骨融合術，重複上述拉伸試驗。拉伸試驗結束後，取下距骨、脛骨，拍攝踝關節軟骨面。在後續處理部分，將量測而得之軟骨資訊與動態三維資料結合，並匯入該試體之電腦斷層掃描後重建的骨頭模型，藉此算出軟骨厚度。而脛骨端與股骨端軟骨在動態資料中的交錯區域軟即代表骨受壓縮。 利用本方法建構出之踝關節軟骨模型，其踝關節脛骨端平均軟骨厚度為0.82 mm，平均面積為1907.7 mm2；踝關節距骨端平均軟骨厚度為0.85 mm，平均面積1289.5 mm2。另本研究將此方法應用於觀察距下關節融合術對於踝關節之生物力學影響。在特定角度下，距下關節融合術將增加關節面之最大變形量與平均變形量，或是造成變形集中於特定區域之現象。而於前拉測試中，由於距下關節被限制，其前距腓韌帶與後距腓韌帶其韌帶應變大於未進行距下關節融合術者。 由本方法量測之關節面變形資訊與周遭韌帶表面應變分布，將有助於了解關節於運動過程中其軟組織之交互作用，未來可進一步驗證電腦模型，提供臨床復健與手術診察的可靠參考依據。

Ankle joint plays an important role in maintain men’s stability in walking or standing. Arthritis is a form of joint disorder that involves inflammation of one or more joints. It is an usual ankle joint disease. Arthritis is a form of joint disorder that involves inflammation of one or more joints. The common causes of disease are related age, autoimmune diseases or joint infection. The major complaint by individuals who have arthritis is joint pain. Pain is often a constant and may be localized to the joint affected. The pain from arthritis is due to inflammation that occurs around the joint, damage to the joint from disease, daily wear and tear of joint, muscle strains caused by forceful movements against stiff painful joints and fatigue. Perhaps we could reveal more fact of arthritis if we can measure the deformation of articular surface. Thus, we try to figure out the biomechanical properties of articular surface, especially in ankle joint which is the most likely to be injured after subtalar arthrodesis, a treatment of ankle arthritis. The main target of the study is to construct a method to measure the deformation of articular surface and the mechanical interaction between ligament and articular surface under external loads. The study use ankle joint cadaver to be the subject. There will also process subtalar arthrodese to observe the influence of subtalar arthrodesis in deformation of articular surface. The study has constructed a new method that combined Vic-3D system, biomedical image process, and robot system on researching the mechanical interaction between ligaments and articular surface under external loads to get more biomechanical information, which can be applied on clinical. The specimen in this study are three ankle joint cadavers. The ankle joint cadavers will remove muscle, fat and other soft tissues except ligaments and articular surface by orthopedist, and the will be coated with random speckles by customize airbrush on interested region before fix on robot system. The cameras of VIC-3D system will capture photos during different flexion angle. After draw test, orthopedist will remove ligaments and expose the articular surface. Coat random speckle on the articular surface. The photo can be reconstructed to the three-dimensional surface in region of interest, and can get the strain in dynamic process. The dynamic bone surface data will combine with articular surface data, and import the bone model from CT. The thickness of the articular surface can be revealed by the difference between CT model and the articular surface data, and the deformation of the articular surface in dynamic equals the interlaced parts. The mean thickness of the distal tibial cartilage layer for the three ankle cadavers was 0.82 mm, with the mean surface area 1907.7 mm2; the mean thickness of the proximal talar cartilage layer was 0.85 mm, with the mean surface area 1289.5 mm2. The method was also applied on measuring the influence of subtalar joint arthrodesis. After subtalar arthrodesis, the deformation of ankle joint was getting larger in some particular angle, and the strain of ATFL and the PTFL were also higher. The method in this study constructed is a helpful tool to understand the interaction between articular surface and the correlated ligaments. Furthermore, the method can be validated computer models, and can be a reference on clinical uses.