Measurement and evaluation of crutch walk motions by Kinect sensor

Currently, we cannot afford to spend much time for instructing usages of crutches for crutch users. However, we should carefully observe the methods of the patients' using crutches whether the methods are appropriate or not because inappropriate methods can raise a secondary accident such as falling. Therefore, it is desirable that patients are instructed readily on the proper method of using crutches when they start to use crutches. When considering the way of crutch walks, we took notice of the before/after body acceleration ratio, that is, the ratio between the accelerations before and after the gait mode-change as an important measure: from previous researches, it was found that there is a relationship between the body parts motions and the before/after body acceleration ratio of crutch users. Furthermore, it is desirable to get the before/after body acceleration ratio, without attaching any sensing devices onto the crutch user's body because the attached sensing devices may disturb a smooth walk. In order to meet the need, the authors proposed an estimation model of the before/after body acceleration ratio from the thigh motions without using any accelerometers. In this paper, as a measuring device, Kinect sensor was employed: although Kinect sensor is easy-to-use of, its measuring accuracy is not as precise as that of standard motion capturing systems. Firstly, the measuring accuracy of Kinect sensor was confirmed. Secondly, participants' crutch walk motions were practically measured by Kinect sensor. Then, the proposed estimation model was applied to the measured motions, and the effectiveness of the estimation model of the before/after body acceleration ratio was discussed. As a result, it was found that there was a high correlation between the estimated before/after body acceleration ratio and the measured one, and the before/after body acceleration ratio of a crutch user was successfully estimated by using the proposed method without an accelerometer nor a motion capturing system.