大趾外翻變形的三維分析

Abstract

大趾外翻為常見的足部疾病之一，但目前僅限於二維X光影像分析，無法看出足部結構在三維空間中的真實變化情形，本研究結合CT影像與機械繪圖軟體將足部結構做重組，並於程式中建立三維投影面來分析大趾外翻所造成的足部結構變化。 首先將要分析的骨頭堆疊重組後轉入機械繪圖軟體做三維角度分析，而在角度量測上使用了主軸作為骨頭在三維空間中的參考軸，藉由將骨頭的主軸投影在三維投影面的方式，分析大趾外翻造成的骨頭間角度變化，在對二維與三維的IMA及HVA等區分大趾外翻嚴重程度指標之數值做完相關性統計後，所得之結果呈高度顯著相關(r>0.9,p<0.01)，驗證了使用主軸作為骨頭間角度分析基準的可靠性。 接著討論第一蹠骨頭部的三種側邊形狀，為了驗證造成側邊形狀的改變與第一蹠骨旋轉的關聯，因此建立了一個方法分析第一蹠骨的相對旋轉角度，分析後結果得知第一蹠骨的旋轉與其三種頭部側邊形狀間具有顯著性差異(p<0.05)，因此我們利用相對旋轉角度來區分出三種不同頭部側邊形狀的區間範圍，此範圍可以提供醫師在治療大趾外翻時當作一個參考指標，由二維X光影像中的第一蹠骨頭部側邊形狀去評估該如何將第一蹠骨轉回適當的位置降低術後的再復發率。 而第一蹠骨與其近端關節面傾斜(Obliquity)角度，也在本文中被拿來討論，分析結果得知其與IMA呈正相關(r=0.579,p<0.05)，驗證了近端關節面的不正常傾斜會造成第一蹠骨的過度內翻，也從相關性統計中發現造成關節面傾斜角度變大的因素也和第一蹠骨的旋轉有關。 最後由重建之足部三維模型量測第一到第五根蹠骨頭部相對於腳踩平面之高度，結果得知頭部的高度由第一蹠骨逐漸下降至第五蹠骨，呈一斜直線排列。接著經由統計分析後發現大趾外翻越嚴重的患者其第一蹠骨頭部之高度則會明顯的下降，兩者間呈高度顯著相關(r<-0.8,p<0.01)。

Hallux valgus is one of the common foot ailment, but is currently limited to two-dimensional X-ray image analysis, cannot see a real change of its structure in three-dimensional space, this study combined with CT imaging and mechanical drawing software will reorganization the foot structure, and use this software to create three-dimensional projection plane to observe the foot structure change caused by hallux valgus. We use the principal axes as the reference axis of the bone in three-dimensional space, then to project the principal axes of the bone to three-dimensional projection plane, and measure the angle between the projection axes. To statistics correlation between 2D and 3D IMA、HVA were showing highly correlated(r>0.9,p<0.01), so validate the reliability of use the principal axes as the bone reference axis to analysis. Analysis the three types of the lateral shape of the first metatarsal head. We find it has associated with the first metatarsal rotation. In order to verify the first metatarsal rotation will cause the shape change, we develop a method to analyze the relative rotation angle of the first metatarsal, statistics results indicated that a significant difference(p<0.05)between the rotation of the first metatarsal and its three types. Therefore, we use the relative rotation angle to distinguish the three interval of the lateral metatarsal head shape. This interval can be provided as a reference for doctor in treatment of hallux valgus to reduce the recurrence rate. Discuss the first metatarsal and its proximal articular surface obliquity, statistics results indicate that a positive correlation with the IMA(r=0.579,p<0.05), verify that an abnormal obliquity of the proximal articular surface led to excessive medial inclination of the first metatarsal, and cause the abnormal obliquity is also related to the first metatarsal rotation. Finally, by the reconstruction of the foot three-dimensional model, measure the height of the first to fifth metatarsal head relative to the flat. Results indicated that the height of head decreased from the first to fifth metatarsal, was an inclined linear alignment. After through the statistical analysis found that the height of the first metatarsal head will significantly decrease when the hallux valgus was severe, showing a highly correlated(r<-0.8,p<0.01).