Augmented reality (AR) has the potential to improve the immersion and efficiency of computer-assisted orthopaedic surgery (CAOS) by allowing surgeons to maintain focus on the operating site rather than external displays in the operating theatre. Successful deployment of AR to CAOS requires a calibration that can accurately calculate the spatial relationship between real and holographic objects. Several studies attempt this calibration through manual alignment or with additional fiducial markers in the surgical scene. We propose a calibration system that offers a direct method for the calibration of AR head-mounted displays (HMDs) with CAOS systems, by using infrared-reflective marker-arrays widely used in CAOS. In our fast, user-agnostic setup, a HoloLens 2 detected the pose of marker arrays using infrared response and time-of-flight depth obtained through sensors onboard the HMD. Registration with a commercially available CAOS system was achieved when an IR marker-array was visible to both devices. Study tests found relative-tracking mean errors of 2.03 mm and 1.12{\deg} when calculating the relative pose between two static marker-arrays at short ranges. When using the calibration result to provide in-situ holographic guidance for a simulated wire-insertion task, a pre-clinical test reported mean errors of 2.07 mm and 1.54{\deg} when compared to a pre-planned trajectory.

翻译：增强现实（AR）有潜力通过使外科医生专注于手术部位而非手术室中的外部显示器，来提升计算机辅助骨科手术（CAOS）的沉浸感和效率。将AR成功应用于CAOS需要一种能够精确计算真实物体与全息物体之间空间关系的校准方法。一些研究尝试通过手动对准或借助手术场景中的附加基准标记实现这种校准。我们提出了一种校准系统，通过利用CAOS中广泛使用的红外反射标记阵列，为AR头戴式显示器（HMD）与CAOS系统的校准提供直接方法。在我们快速且用户无关的设置中，HoloLens 2利用HMD内置传感器获取的红外响应和飞行时间深度数据来检测标记阵列的姿态。当红外标记阵列对两个设备均可见时，即可实现与商用CAOS系统的配准。研究测试发现，在短距离下计算两个静态标记阵列之间的相对姿态时，相对跟踪的平均误差为2.03 mm和1.12{\deg}。使用校准结果为模拟导线插入任务提供原位全息引导时，一项临床前测试报告与预规划轨迹相比的平均误差为2.07 mm和1.54{\deg}。