由於C-arm影像的有限視野及二維影像的限制，使得醫師在手術中若需即時得知器械及骨骼之空間關係，必須拍攝大量的C-arm影像，進而使得醫師與病患皆須承受高劑量輻射線之風險。在髖關節表面重建手術(Hip Resurfacing Arthroplasty)中，最關鍵的步驟即是將Pin-centering Guide以通過股骨頭球心並沿股骨頸之方向進入股骨內，雖然廠商有提供器械輔助定位，但其過程繁複且不能保證其鑽入方向之正確性。 為改善C-arm使用上之缺點，本研究發展一套以C-arm影像為主的髖關節表面重建手術導引系統，利用股骨頭近似圓之特性經由兩張C-arm影像求解空間股骨頭球心位置，並提出以橢圓柱嵌合股骨頸之方式尋找股骨頸軸線並決定放置植入物之方位。且本系統結合光學式定位裝置能在手術中將器械與骨骼的空間關係即時顯示於電腦螢幕中，協助醫師更精確的鑽孔及後續植入物的放置動作，以期使病患獲得更好的醫療品質。 本研究提出之股骨頸外型嵌合與股骨頸軸線計算最佳化擬合方式可確實反映出股骨頸區域之真實外型，並有效達成安全引導鑽孔路徑之目的，且鑽孔位偏差可控制在4°以內。 The common used C-arm X-ray image for orthopedic surgery is a kind of cone-beam projection image, which cannot illustrate the anatomic structure of tissues clearly. During operation, the surgeon may take as many C-arm images as necessary to obtain in-time relative positions 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. The developed image-guided navigation system for hip resurfacing arthroplasty only needs two C-arm images taken at different views to guide surgical tools to the desired position and orientation. First, the center of the femoral head on each of the two C-arm images is determined by using a circle to approach the cartilage profile of the femoral head. The spatial coordinates of the femoral head center are then calculated by finding the intersection of the two projection lines connecting the femoral head center of the C-arm image and the X-ray projection center (one for each C-arm image). Then, the measured coordinates of periphery points of the femoral upper neck are used to determine an elliptic cylinder to approximate the neck profile. The axis of the elliptic cylinder must pass through the femoral head center and is the desired direction to insert the rod of the femur implant. The computer will display in real time the axial direction of the elliptic cylinder together with the direction of surgical tools on each of the two C-arm images. Therefore, under the guidance of the dynamically displayed images, the surgeon will be able to drill a hole passing through the femoral head center and along the axial direction. An experiment using saw bone to go through the operation procedure is completed. The results show that the drilled hole is within the safe zone of the femoral neck and has an approximate 4° error relative to the axis of the elliptic cylinder.
