骨髓內釘固定孔之磁力式定位裝置改進與鑽孔測試

Abstract

骨髓內釘為目前治療長骨骨折的主要的方式。在手術的過程中，必須將固定螺絲通過固定孔並鎖在硬質骨上，如何在看不見骨釘的的情況下，正確的找到固定孔的位置與方向，是手術中最棘手的步驟。 本研究使用兩階段式的被動式磁力式定位系統，除了三維定位測試之外，也進行豬脛骨鑽孔測試。首先將目標磁鐵放置在固定孔的位置，與之同軸，接著將含有目標磁鐵的骨髓內釘打入骨髓腔中，接著進行初步定位、細部定位與鑽孔步驟，初步定位使用兩個磁鐵快速定位目標磁鐵所在的區域，而細部定位裝置為透明板材，包含三組對稱的磁針和導電板，當磁針受到目標磁鐵吸引時，磁針可以自由轉動並指向目標磁鐵找到骨髓內釘固定孔的位置與方向，根據磁針與對齊線的交疊情形與指示器的燈號確認定位狀況，成功定位到骨釘固定孔後，即可以電鑽上的鑽頭沿著細部定位裝置上的圓心孔洞鑽孔，直鑽到骨頭的另一側。 本研究改進本實驗室已開發之磁力式定位裝置，著重在(1)提升定位精度：透過導電板孔洞直徑的設計，縮小磁針可動範圍，減少定位誤差;(2)可判斷細部定位裝置之調整方向：細部定位裝置透明板材的設計，可清楚看見磁針的偏擺情況，根據磁針偏擺方向，導引細部定位的搜尋方向;(3)雙指示燈設計：指示器的燈號由一個改為兩個，紅燈亮起時代表細部定位裝置所連接的迴路順暢無故障，綠燈亮起時代表定位成功。除了裝置本身的改進，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。 以上為本研究改進特點，不僅能精準定位到骨髓內釘固定孔的位置與方向，定位過程也很迅速，研究成果如下：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5分鐘，定位連帶鑽孔的時間不到10分鐘，證實此磁力式定位系統搜尋骨髓內釘固定孔的定位能力，並驗證在豬脛骨搜尋骨髓內釘固定孔的可行性。

Intramedullary nailing is a common surgical operation to repair fractures of long bones. One difficult part of the surgery is to locate the accurate drilling position and direction for interlocking screws, which is invisible to the naked eyes. Here a novel and simple design using passive magnets is proposed to locate drilling position and direction to simplify the distal locking process in intramedullary nailing operation in a more intuitive way. By using the magnetic targeting devices, we test on transparent bone with a laser LED and swine tibia with drilling. First of all, we place intramedullary nail including a positioning magnet into tibia medullary cavity. 1st-stage targeting device targets approximate area of the positioning magnet with two responding magnets quickly. 2nd-stage targeting device is component of transparent material, consisting of three magnetic pins and an electrical conductive board. The three symmetrically placed magnetic pins can rotate freely and point to the positioning 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 observed by the overlap of magnetic pins and aligning line and detected through the contact between magnetic pins and upper conductive board. When the device is not aligned with the positioning magnet in the nail properly, either in position or direction, the magnetic pins then will contact with the board to trigger a system of two light-emitting diodes for indicating And when the device is right aligned with the positioning magnet in the nail, we can drill the location where we target by a screwdriver. We modify the magnetic targeting device that our lab developed. The primary emphasis of our research is (1) Promoted accuracy: The design of the diameter of the hole on the 2nd –stage targeting device decreases the movable space and reduces targeting error. (2) Indicated direction of 2nd –stage targeting device: Transparent material constitutes 2nd –stage targeting device, and it provide a function that the state of the magnetic pins are visible. With the function, we can target screw hole effectively. (3) Indicator with two light-emitting diodes: We can confirm that the electric loop is not breakdown when the light was red. The targeting is finished when the light was green. After we improved the magnetic targeting device, we verify the feasibility of the proposed design and applying on swine tibia. The improvement of the magnetic targeting devices provides accurate targeting in position and direction quickly. It is shown that the accuracies in position and direction are 2.1 mm and 7 degrees, respectively, with remote vertical distance of 16mm-20mm, which takes less than 5 minutes to target and a screw hole, less than 10 minutes to target and drill a screw hole.