医疗级MEMS实现膝关节置换手术精确定位

目前，大约有30%的膝关节置换手术，会因为难以对骨骼内部进行精确定位而产生错位问题。不过，现在已经能在手术前，透过亚德诺(ADI)公司的高精度微机电系统(MEMS)传感器，迅速追踪病人的膝关节定位(alignment)和运动状况。一家位于加州的 OrthAllign 公司，正在努力将膝关节定位的成功率提高到100%。 “ADI的高精度惯性测量单元(IMU)，让我们的Knee Align系统可执行平均要价40万美元甚至更高价光学系统的功能，”OrthAlign公司企业发展副总裁Darius Kharabi说。“现在，外科医生能运用成本更低廉、更易于使用的设备，在手术中达到近乎完美的定位效果。” 这个市场非常大，因为仅在美国，每年施行的膝关节置换手术便高达67.5万例，而据美国医疗照护研究及品质机构(Agency for Healthcare Research and Quality, AHRQ)预估，到2030年，全美国将有超过350万人可能要施行膝关节置换手术。 不幸的是，Arthroplasty期刊资料显示，今天大多数的膝关节置换手术都使用老旧的机械式定位工具，由于这些工具的精确度不高，因此定位成功率平均在70%以下。目前部份医院采购了光学式定位系统来增加定位成功率。然而这种仪器非常庞大，难以使用而且昂贵，因而仅有不到5%的外科医生在实施膝关节置换手术时会使用到它。

OrthAlign的医疗仪器使用了ADI包含三轴陀螺仪和加速器的惯性测量单元(IMU)，
能在膝关节置换手术中引导外科医生的手术刀。ZcFesmc

另一方面，采用MEMS技术的全新OthAllign设备，其尺寸精巧到足以用手握住，而且便宜到能够一次性使用后便丢弃，使用它的时间只需要几秒钟，但其精确度却足以媲美高达数十万美元甚至更高价的光学设备，OthAllign公司表示。 OthAllign成立于2008年，已开发并展示一套基于MEMS的膝关节手后定位系统，用于全膝关节置关手术(total knee arthroplasty, TKA)之中。该公司表示，其第二代KneeAlign仪器已获得美国FDA核准，在TKA手术中，当必须对膝关节的上下部位进行切除以置换成新的人工关节时，这套仪器可更良好地引导外科医生。 OrthAllign表示，选择ADI IMU是由于该组件内含高精度的三轴陀螺仪及加速器，能实时追踪膝盖的定位情况。在将一个IMU-bearing模块附加在膝关节上之后，外科医生只需要在一般的移动范围内移动膝盖──过程不用到一分钟──在这个MEMS传感器使用精确运动追踪资料的算法计算后，便可精确得知必须从骨头的何处下刀。该公司的KneeAlign仪器前端附有一个显示器，可为外科医生显示如何精确调整其切割仪器，以确保要换上的人造关节能精确定位。 OrthAllign基于MEMS的KneeAlign仪器已经被用在纽约的Hospital for Special Surgery，以及圣地亚哥的Scripps Green Hospital之中，预计2012年第一季能广泛供应给全美各地的医院。 编译： Joy Teng 本文授权编译自EE Times，版权所有，谢绝转载 参考英文原文：：Medical MEMS tackles knee replacement，by R. Colin Johnson

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{pagination} Medical MEMS tackles knee replacement R. Colin Johnson PORTLAND, Ore.—Currently, more than 30 percent of knee replacement surgeries suffer from misalignment problems caused by the "fog of surgery"–where the precise orientation of internal bones is difficult to determine. By adding a complement of Analog Device Inc.'s high-precision MEMS sensors to track the alignment and motion of a patient's knee during the surgery, OrthAlign Inc. (Aliso Viejo,Calif.) aims to dramatically increase precision. "The high-precision of Analog Devices' IMU enables our KneeAlign system to perform as well as optical systems that cost $400,000 or more," said Darius Kharabi, OrthAlign’s vice president of corporate development. "Now surgeons can now get a much higher degree of precision with an easy-to-use device that costs a fraction of the price." The stakes are huge, since more than 675,000 knee replacements are performed every year in the U.S. alone, with trends indicating that as many as 3.5 million Americans will have the procedure performed by 2030, according to the Agency for Healthcare Research and Quality (Rockville, Md.). Unfortunately, today most knee replacements are performed using antiquated mechanical alignment tools which are imprecise, resulting in a success rate of less than 70 percent, according to according to studies in the Journal of Arthroplasty (Mason, 2007) . Until now, the only alternative was purchasing an optical alignment system to increase success rates. But the instruments are bulky, hard-to-use and expensive, resulting in less than 5 percent of knee procedures performed using them. The new OthAllign MEMS-based instrument, on the other hand, is small enough to hand hold, cheap enough to throw away after a single use, works in just a few seconds, and is as precise as the optical systems costing hundreds of thousands of dollars more, according to OrthAlign. OrthAlign was founded in 2008 and has already demonstrated a MEMS-based knee-surgery alignment tool for performing one part of the total knee arthroplasty (TKA) procedure. The company received Food and Drug Administration clearance earlier this year for its second-generation KneeAlign instrument, which guides the surgeon when making both the top and bottom severances necessary to remove the natural knee and insert the mechanical one during TKA. The IMU from Analog Devices was chosen for its high-precision use of three-axis gyroscopes and accelerometers to track knee orientation in real time, according to OrthAlign. After attaching the IMU-bearing module to the natural knee, the surgeon merely moves the natural knee threw its normal range of motion—a procedure that takes less than 30 seconds—after which algorithms uses the precision motion tracking data from the MEMS sensors to calculate the positioning of the cutting instrumentation on the knee. A display on the front panel of the KneeAlign instrument shows surgeons the real-time positioning of their cutting instrument to help ensure precise alignment for the artificial knee. OrthAlign's MEMS-based KneeAlign instrument is currently being used by the Hospital for Special Surgery (New York) and the Scripps Green Hospital (San Diego), but will be available to hospitals in select geographies in the first quarter of 2012.