Novel Passive Two-Stage Magnetic Target Devices for Distal Locking of Interlocking Nails

• Main Authors: Wong, Tze-Hong, 王子康
• Other Authors: Hsu, Wensyang
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/d64syg

博士 === 國立交通大學 === 生物科技學系 === 106 === 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