股骨長骨骨折回復手術過程中，醫師為了需要一再拍攝X光影像，以確保骨骼回復時的安全性與正確性，其所累積的輻射劑量，對醫護人員與病人健康皆是危害。又X光影像是二維透視影像，只能提供醫師有限的空間資訊，因此本研究針對股骨長骨骨折回復手術發展一套以C-arm影像輔助的手術導引系統，此系統除了可降低拍攝X光的次數，也能協助醫師正確將斷裂的長骨回復到應有的位置，加上股骨內外轉角度在C-arm影像上並不容易看出，因此若能提供股骨解剖幾何的角度資訊，對於提升手術品質將是有相當大的助益。 本研究所發展的手術導引系統，係基於人體左右兩側的股骨長骨是近似對稱，因此以未斷裂的長骨尺寸與方位作為斷裂長骨應回復的長度與方位。分別在C-arm影像上選取股骨特徵點座標，包括股骨球頭中心、股骨長軸軸線以及股骨後髁中心，建立出股骨近端座標系統與股骨遠端座標系統，再利用一光學式定位裝置，追蹤固定在兩節長骨上的動態參考框架(Dynamic Reference Frame)，以得到長骨的方位，藉由調整兩節長骨的動態參考框架相對座標方位與目標方位之差異，來得知回復的程度。 實驗以一斷成二節的長骨模型做測試，結果顯示回復後的股骨長度誤差為5mm，內外轉角度(Internal/External Rotation)、彎曲伸展角度(Flextion/Extension)及外展內收角度(Abduction/Adduction)的誤差也在6度左右。其誤差來源主要是在C-arm影像上選取特徵點時的人為誤差，因此提高特徵點的辨識度及穩定度，將有助於系統誤差的改善。 During operation of femur fracture reconstruction, the surgeon may take many C-arm images to obtain in-time position information of surgical tools and bones. Therefore, no matter medical persons or the patient will face the risk of receiving high dose of radiation. To solve this problem, an image-guided navigation system is developed. In this study, both femurs of the patient are assumed to have similar anatomic dimension. Therefore, the anatomic dimension of the normal femur can be used as the navigation reference to reconstruct the fractured femur so that both femurs will have similar anatomic dimension. The anatomic dimension is determined by the femoral proximal frame and the femoral distal frame, which can be determined by two C-arm images taken in different positions. An optic tracker is applied to measure the relative positions of the dynamic reference frames mounted on both sides of the fractured femur so that the relative position or the transformation matrix between the femoral proximal and distal frames can be determined in real time. An experiment to verify the performance of the navigation system using a fractured and a normal saw bones has been done. The fractured femur is restored to its original anatomic dimension by following the information displayed on the computer monitor. The results show that the error in length is 5mm and axis error is about 6°.
