磁力式骨髓內釘定位系統之定位磁鐵置入/取出機構的研發

Abstract

在骨髓腔中植入互鎖式骨隨內釘為目前治療長骨骨折最常用的方式，在手術過程中，由於看不見骨釘的情況，因此找到固定孔正確的位置與方向，是手術中最耗時的步驟。骨髓內釘在植入過程中可能會發生變形、扭曲，使臨床上使用之平行定位輔助機構在定位骨釘遠端固定孔時常無法正確定位，移動式Ｘ光機可直接找到固定孔的位置，但醫療人員長期暴露在輻射環境中，易對健康產生危害。文獻上，多數的無輻射定位方法只能定位固定孔的位置，而可同時定位固定孔的位置與方向的方法中，磁力定位採主動式定位系統，設計和操作較複雜，內部鑽孔系統則會有手術器械遺留人體內部的疑慮。因此本研究室提出一個兩階段（初步定位及細部定位）被動式磁力定位系統，在不使用X光機（無輻射線）的情況下，可快速且精確找到固定孔的位置與方向，且含警示功能，可即時提醒觀測者定位狀況，亦整合磁場定位裝置和鑽孔設備，定位成功即可進行鑽孔，完成骨釘固定。透過改進與鑽孔測試，已可達到目標規格：使用的工作範圍為垂直距離16mm-20mm，水平定位誤差在2.5mm以下，角度定位誤差在7°以下，搜尋到一組固定孔並完成鑽孔時間為450秒，成功縮短手術時間並驗證其三維空間定位能力。 然之前所提出的設計仍需為了在固定孔處置入定位磁鐵而對骨釘進行加工，且在定位完成並鑽孔後，定位磁鐵與骨髓內釘一起留滯於人體中。雖定位磁鐵之外層包覆材料具生物相容性，但短期之內，我們無法準確得知定位磁鐵長期置於人體中，是否會釋放威脅患者健康的有害物質，或對人體造成其他影響，故本論文的目標為配合先前提出之兩階段被動式磁力定位系統，開發不需對骨釘進行加工之設計，並配合此設計進一步改進兩階段被動式磁力定位系統的整體定位及鑽孔流程。 為達成前述目標，主要工作項目包含開發內部定位磁鐵可移出骨釘之機構及定位及鑽孔測試兩個部分。針對使用之骨釘尺寸設計並開發可將定位磁鐵移出骨釘之機構，並且確認定位磁鐵置入與移出骨釘可行性之後，再配合改進完成之兩階段被動式磁力定位系統，先測試磁力式定位系統的定位能力，再分別於泡棉骨頭及動物骨頭上進行定位和鑽孔實驗，驗證新式之內部定位磁鐵不會影響磁場式定位系統定位精準度。從實驗結果來看，定位一個骨髓內釘固定孔並完成鑽孔的時間為300秒以下，且定位完成後可順利將定位磁鐵移出骨釘。我們分別進行了5次定位測試、泡棉骨頭與豬下肢骨鑽孔測試，無論定位或鑽孔成功率皆為100%，驗證了新開發之定位磁鐵置入/取出機構可配合兩階段被動式磁力定位系統進行定位及鑽孔。希望通過改良定位磁鐵的置入/取出機構，讓此創新的兩階段被動式的磁力式定位裝置更具產品化之可能性。

Intramedullary nailing is a typical surgical operation to repair fractures of long bones. In the surgery, after the nail is inserted into a bone, the screw-holes become invisible for the surgeons. Thus, one key difficulty of the surgery is to accurately locate the invisible screw-holes in order to obtain the drilling position and direction for interlocking screws. Clinically, intramedullary nail may distort during implantation, therefore the guiding mechanism won’t be able to locate the screw-hole accurately. To address this issue, surgeons use conventional X-ray-imaging approaches to locate the drilling position and direction of the screw-holes. However, utilizing the X-ray-imaging approaches, the surgeons, medical teams, and patients are under the radiation exposure. To prevent the radiation exposure, a non-radiation approach is needed. However, most non-radiation approaches locate only the drilling position not both drilling position and direction. Here we have proposed a novel two-stage passive magnetic guiding system to fast and accurately locate the drilling position and direction. After our development of the proposed position system and improvement with drilling tests, preliminary results are shown to meet the required specifications: for a remote vertical distance ranging from 16 mm to 20 mm, the accuracy in horizontal position and angular direction are within 2.1 mm and 7 degrees, respectively. Also targeting and drilling one screw-hole can be completed within 8 minutes, which verifies the 3D targeting capability of the proposed design. However, current approach still needs to modify the intramedullary nail in order to place an internal position magnet at the screw hole, and the magnet can not be removed after operation. Therefore, the main objective of this project is to design proper mechanism which can remove the magnet from the nail without modifying the intramedullary nail, as well as the improvement on the position system for this new design. Working items include: (1) Development of a movable mechanism to insert or remove the position magnet into or from and intramedullary nail; (2) drilling tests. It is hoped that, without modifying the existed intramedullary nail, the proposed two-stage passive magnetic positioning system can be more feasible for commercial product.