Plug-and-Play IMU-based Gait Measurement: Towards 3D Foot Angle Estimation

Knee osteoarthritis (KOA) is a common joint disease, causing pain, stiffness and other motor disorders. Gait analysis is an important basis for understanding the causes and formulating personalized rehabilitation plans. Although optical motion capture is regarded as the gold standard for measurement, it has drawbacks such as high cost and being limited to laboratories. Inertial measurement units (IMUs) offer an out-of-lab gait measurement method, but the accuracy of the measurements relies heavily on the participants’ performance of the calibration movement, posing challenges for patients with gait abnormalities. Although in previous studies, this had little effect on the measurement of sagittal angle, it has a significant impact on the measurement internal and external rotation. The range of internal and external rotation of the ankle joint is very small. Excessive external rotation of foot may indicate excessive external rotation of the knee joint. Therefore, accurate measurement of 3D foot angles, especially internal and external rotation, is important for KOA. We proposed a gait measurement method, the calibration process will be non-sensory for the user. We recruited 20 healthy subjects 8 KOA patients. The root mean square errors of foot angles range from 3.0° to 6.6° in three directions. We investigated the influence of abnormal gait on calibration and determined that our calibration method is less affected by gait abnormalities. Therefore, this method is also expected to be applied to other patients with abnormal gait.

膝骨关节炎（KOA）是一种常见的关节疾病，其特征为疼痛、僵硬及其他运动功能障碍。步态分析是理解病因及制定个性化康复方案的重要依据。尽管光学动作捕捉被视为测量的黄金标准，但其存在成本高昂且局限于实验室的不足。惯性测量单元（IMUs）提供了一种实验室外的步态测量方法，然而，测量的准确性高度依赖于参与者对校准动作的执行，这对步态异常的病患构成了挑战。尽管在以往的研究中，这对接地角测量影响甚微，但对接地内外翻的测量却产生了显著影响。踝关节的内翻与外翻范围极为有限。足部外翻过度可能预示着膝关节外翻过度。因此，准确测量三维足部角度，尤其是内翻与外翻，对于膝骨关节炎至关重要。本研究提出了一种步态测量方法，其校准过程对用户而言将不涉及感官刺激。我们招募了20名健康受试者和8名膝骨关节炎患者。在三个方向上，足部角度的均方根误差范围在3.0°至6.6°之间。我们研究了异常步态对校准的影响，并确定我们的校准方法受步态异常的影响较小。因此，该方法有望应用于其他步态异常的患者。