van Duren B H, Sugand K, Wescott R, Carrington R, Hart A
Institute of Orthopaedics & Musculoskeletal Sciences, University College London, London, UK.
MSk Lab, Imperial College London, Charing Cross Hospital, London, UK.
Med Eng Phys. 2018 May;55:52-59. doi: 10.1016/j.medengphy.2018.02.007. Epub 2018 Mar 30.
Hip fractures contribute to a significant clinical burden globally with over 1.6 million cases per annum and up to 30% mortality rate within the first year. Insertion of a dynamic hip screw (DHS) is a frequently performed procedure to treat extracapsular neck of femur fractures. Poorly performed DHS fixation of extracapsular neck of femur fractures can result in poor mobilisation, chronic pain, and increased cut-out rate requiring revision surgery. A realistic, affordable, and portable fluoroscopic simulation system can improve performance metrics in trainees, including the tip-apex distance (the only clinically validated outcome), and improve outcomes.
We developed a digital fluoroscopic imaging simulator using orthogonal cameras to track coloured markers attached to the guide-wire which created a virtual overlay on fluoroscopic images of the hip. To test the accuracy with which the augmented reality system could track a guide-wire, a standard workshop femur was used to calibrate the system with a positional marker fixed to indicate the apex; this allowed for comparison between guide-wire tip-apex distance (TAD) calculated by the system to be compared to that physically measured. Tests were undertaken to determine: (1) how well the apex could be targeted; (2) the accuracy of the calculated TAD. (3) The number of iterations through the algorithm giving the optimal accuracy-time relationship.
The calculated TAD was found to have an average root mean square error of 4.2 mm. The accuracy of the algorithm was shown to increase with the number of iterations up to 20 beyond which the error asymptotically converged to an error of 2 mm.
This work demonstrates a novel augmented reality simulation of guide-wire insertion in DHS surgery. To our knowledge this has not been previously achieved. In contrast to virtual reality, augmented reality is able to simulate fluoroscopy while allowing the trainee to interact with real instrumentation and performing the procedure on workshop bone models.
髋部骨折在全球造成了巨大的临床负担，每年有超过160万例病例，且第一年死亡率高达30%。动力髋螺钉（DHS）置入是治疗股骨颈囊外骨折的常用手术。股骨颈囊外骨折的DHS固定操作不当会导致活动不佳、慢性疼痛以及切出率增加，从而需要进行翻修手术。一个逼真、经济且便携的透视模拟系统可以改善学员的操作指标，包括尖顶距（唯一经过临床验证的结果），并改善治疗效果。
我们开发了一种数字透视成像模拟器，使用正交相机跟踪附着在导丝上的彩色标记，这些标记在髋部透视图像上创建了虚拟叠加层。为了测试增强现实系统跟踪导丝的准确性，使用标准的模拟股骨来校准系统，固定一个位置标记以指示顶点；这使得系统计算的导丝尖顶距（TAD）能够与实际测量值进行比较。进行测试以确定：（1）顶点的定位精度；（2）计算得到的TAD的准确性。（3）通过算法实现最佳准确性与时间关系的迭代次数。
计算得到的TAD平均均方根误差为4.2毫米。算法的准确性随着迭代次数的增加而提高，直至20次迭代，之后误差渐近收敛至2毫米。
这项工作展示了一种在DHS手术中模拟导丝插入的新型增强现实技术。据我们所知，此前尚未实现这一点。与虚拟现实不同，增强现实能够模拟透视，同时允许学员与真实器械进行交互，并在模拟骨模型上进行操作。
