拇指外翻主要成因為大拇指底部的關節脫位，引起大拇指往外側彎造成骨頭向外突出。截骨術固定板為最常運用於拇指外翻治療的方式，目前對於固定板的主要評估方式來自於臨床結果。雖然先前研究開發的三維足踝模型提供相關生物力學參考，但它們的數值模型可能有過於簡單化、擬真度不足等問題。因此本研究的目的是建立更完整下肢骨骼肌肉模型與植入物模型，並透過有限元素法探討三維人體下肢骨骼肌肉模型於拇指外翻治療之生物力學評估。

研究使用Solidworks 2015依序完成完整下肢模型建構、截骨術固定器模型建構與不同治療下肢模型建構，接著使用ANSYS Workbench 17.0進行模擬。本研究主要使用不同類型的截骨術固定方式，包含骨板、克氏針(K-pin)與加入繃帶的克氏針(K-pin+B)，其中固定板設計包括：四孔四螺絲(4H4S)、六孔四螺絲(6H4S)、動態壓縮式六孔六螺絲(6H6S-D)、鎖定式六孔六螺絲(6H6S-L)。探討穩定度、蹠骨應力、植入物應力。

結果顯示骨板類會比K-pin具備更好的穩定度(骨變形降低)，另外，加入繃帶的K-pin穩定度有顯著提升。對於應力結果，相較於其他植入物治療，4H4S與6H6S-L植入物應力最小，6H6S-L同時具有最低的骨應力，K-PIN+B雖然可使植入物應力降低，但同時提高骨應力。這項研究可以提供外科醫師對於拇指外翻治療之生物力學結果與原理。

Hallux valgus is the commonest forefoot deformity. Different treatment methods have been applied to fix this problem including osteotomy fixation plates, Kirschner wires, and bunion splints. Past studies have investigated the biomechanics of hallux valgus with different treatments using numerical and/or experimental approaches. However, there are rare studies that evaluated each treatment method using a realistic musculoskeletal lower extremity model. Thus, the purposes of this study were to develop a more complete three-dimensional human musculoskeletal lower extremity model and to evaluate the strengths and limitations of different hallux valgus treatment techniques.

Four types of osteotomy fixation plates, a Kirschner wire (K-pin), and a Kirschner wire with a bandage (K-pin+B) were developed using SolidWorks. The osteotomy fixation plate designs included 4-hole plate with 4 screws (4H4S), 6-hole plate with 4 screws (6H4S), 6-hole plate with 6 screws and dynamic compression holes (6H6S-D), and 6-hole plate with 6 screws and locking compression holes (6H6S-L). All the fixation devices were assembled into the musculoskeletal lower extremity model. Sixteen types of the foot ligaments were considered and simulated using tension-only spring elements. The finite element models of the lower extremity with different hallux valgus treatments were developed using ANSYS Workbench. The proximal tibia was fully constrained, and an Achilles tendon was simulated by applying a tendon force. A ground reaction force was applied to a moveable ground. In post-processing, the bone fixation stability, the implant stress, and the bone stress were calculated and discussed.

All the plate fixations revealed better bone fixation stability (lower bone deformation) than the K-pin. It was surprising that the K-pin+B significantly improved the fixation stability compared to the K-pin. For the results of the implant stress and bone stress, the 4H4S and 6H6S-L had lower implant stress compared to the other treatments. The 6H6S-L showed the lowest bone stress compared to the other plate fixations and the Kirschner wire fixations. Adding the bandage to the K-pin treatment could reduce the implant stress, but the bone stress was found to be increased. This study could provide surgeons some useful information and theoretical basis in the biomechanics for the treatment of hallux valgus.

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