磁力式骨髓內釘定位系統之研發

Abstract

本論文為針對使用骨髓互鎖式內釘時,所面對之鎖定困難而進行之多階段為期三年之研究,對鎖定螺絲之植入,以前發明之初,忽略植入螺絲時三度空間之準確性之要求,致使定位描準始終不確實,在無法透視螺孔之情況下,盲目植入螺絲,增加了手術的困難度.在臨床上，使用移動式Ｘ光機可以直接的找到固定孔的位置，但此方式使得醫療人員必須暴露在高輻射的環境中，健康產生危害。在無輻射定位的文獻中，大多數的定位方法只能定位出固定孔的位置，並無法定位出固定孔的方向，而在少數可以同時定位固定孔的位置與方向的方法中，系統較複雜。本論文研究在強調放棄使用、放射綫以避免輻射傷害,提出一項創新的骨髓內釘固定孔的定位解決方案，此方案包含兩類機制獨立卻又具備互補功能之定位方式，分別為(I)磁力式定位與(II)電磁感應式定位。其中，(I)磁力式之技術特點可分為兩個部分：第一個部分為目標磁鐵的設計與置入，藉此可達成不須取出骨釘之內埋磁鐵即可直接進行骨頭鑽孔之手術步驟。第二個部分為連結警示功能之體外瞄準裝置，藉由前述骨釘內埋磁鐵與此部分之體外瞄準裝置的機構特殊設計，可使骨釘內埋磁鐵與瞄準裝置產生一非常靈敏之磁力互動，透過分析此互動之磁力則可成功使得體外瞄準裝置能輕易地尋找到內埋骨釘之磁鐵位置進而送出警示訊號，此即達成快速準確搜尋固定孔位置與方向的目標。至於(II)電磁感應式定，則是透過三種不同設計(骨釘無內埋磁性材料搭配體外訊號發射線圈與訊號感應線圈，骨釘無內埋磁性材料搭配體外訊號發射電磁鐵與訊號感應線圈，骨釘有內埋高導磁率材料與外部訊號發射電磁鐵與訊號感應線圈)，主要是透過電磁鐵發射一準直磁力線，此磁力線會被骨釘幾何及骨釘內埋高導磁材料兩者所影響，被影響之磁力線會被感應線圈所接受進而產生不同的感應電動勢，分析此感應電動勢可判斷是否定位成功。 初期研究在於研發並設計出以磁力原理作為描準基礎之定位裝置,以不同之設計方案各自進行測試以比較其準確程度予以選擇應用上述所提出之任何一種定位方式(磁力式或電磁感應式)，皆能獨立地使醫生能快速準確地搜尋到骨頭內之骨髓內釘上之固定孔位置與方向。在手術中，針對某些特殊應用場合，則可透過磁力與電磁感應互補機制，設計製作磁力與電磁感應複合式之定位系統，藉以滿足不同應用場合之定位需求。 中期研究改進了之前提出的磁力式定位裝置，著重於定位儀之實體製造及精確度測試。並基於提升定位精度,細部定位裝置之調整方向並根據磁針偏擺方向，導引細部定位的搜尋方向, 以及紅綠雙指示燈設計顯示定位成功與否之告示.我們也利用改良後的磁力式定位裝置進行測試，分別在透明脛骨模型上配合雷射二極體進行三維定位測試，以及在豬脛骨上進行實際鑽孔測試。 於後期研究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。主要研究項目包含兩個部分：(1)開發內部定位磁鐵可移出骨釘之機構；(2)定位及鑽孔測試。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，並且於確認定位磁鐵置入與移出骨釘可行性之後，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。 研究成果摘要如下：針對外徑12mm的脛骨骨釘做定位的設計，在垂直工作距離16 – 20mm的工作範圍之下，水平定位精度在2.1 mm以內，角度定位精度7°以下。三維定位測試和鑽孔測試的實驗結果符合研究目標，在定位骨釘固定孔的時間不到4分鐘，定位連帶鑽孔的時間不到5分鐘，證實了此磁力式定位系統搜尋骨髓內釘固定孔的定位能力，並成功在豬脛骨進行骨髓內釘固定孔的定位實驗，成功率可達100%。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。

關鍵字：骨髓內釘、螺絲固定孔、定位系統、磁力式、鑽孔、磁鐵的置入/取出

For fixation of comminuted, proximal or distal end long bone fracture as well as non-union fracture,interlocking nailing is the gold standard for internal fixation.The study is a three-year study for improving the targeting procedure from the inaccuracy of present devices.Due to ignoring the important 3-D inserting concept of the screws, orthopedic surgeon always tackle the difficulty in targeting . To solve this problem, surgeons frequently make use of 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 instead of targeting both drilling position and direction. Only few of the approaches utilizing active targeting systems are capable of locating both the drilling position and direction but the systems are complicated. Hence, we propose two novel and simple approaches to locate the drilling position and direction. In 2012(Initial period) the first approach/design utilizes a magnetic-force interaction. That is, the design uses passive magnets to locate the drilling position and direction. This simplifies the distal locking process in intramedullary nailing operation in a more intuitive way. According to the design, the device consists of three magnetic pins and an electrical conductive board. The three symmetrically placed magnetic pins can rotate freely and point to the permanent magnet inside the nail. The drilling position and direction can be obtained by moving the device with those magnetic pins to align with the magnet in the nail. The alignment can be detected through the contact between magnetic pins and upper conductive board. When the device is not aligned with the magnet in the nail properly, either in position or direction, the pins will contact with the board to trigger a light-emitting diode for alarming. The second approach is an electromagnetic-induction based approach. The approach utilizes electromagnets, inductors, and/or coils in order to target the screw-holes. According to the approach, the targeting system we fabricated consists of a c-shaped electromagnet or an inductor, pick-up coil, high-permeable curved silicon-steel strip embedded on the nail (optional), guiding mechanism, and measuring electronics. An alternative current is applied to the electromagnet or inductor to generate a uniform magnetic field/flux. When the electromagnet or inductor scans through a nail inside a bone, the magnetic flux is influenced by the screw-holes (and by the optional high-permeable silicon-steel strip embedded on the nail). The variation of the magnetic flux subsequently induces a voltage response in the pick-up coil. Through analyzing the patterns of the voltage response, a criterion is established for screw-hole targeting. In 2013 (middle period) the prototype of the proposed magnetic targeting device was designed and tested to verify feasibility. This year, the device is further improved to enhance positioning accuracy by reducing diameter of conducting hole; while make the adjustment of targeting device easier by using transparent plates; In addition two alarming LEDs to determine the positioning condition withred and green indicating illumination. Positioning tests and drilling tests are performed. In final stage of the study, we modify the intramedullary nail in order to place an internal position magnet at the screw hole, and the magnet could 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. For 2014 (final period) research 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. The summarized results as following: The results shows the accuracy in position and direction targeting is 3 mm and 10 degrees, respectively, with a remote vertical distance ranging from 15 mm to 20 mm which takes less than 4 minutes to complete the targeting and 5 minutes to fix the screw This verifies the feasibility of the proposed approach/design. By the criterion, the experimental result shows the maximum targeting error for targeting the drilling location and orientation of a screw-hole with a diameter of 5 mm is less than 1 mm and 5 degree, respectively. It is shown that it takes less than 5 minutes to target a screw hole with the accuracies in position and direction of 2.1 mm and 7 degrees, respectively, at remote vertical working range of 16mm-20mm. Furthermore, it takes less than 10 minutes to target and drill a screw hole with 100% successful rate. Keywords: Intramedullary nail, interlocking-nail surgery, magnetic, electromagnetic, positioning system