Real-time gait event detection for lower limb amputees using a single wearable sensor

This paper presents a rule-based real-time gait event/phase detection system (R-GEDS) using a shank mounted inertial measurement unit (IMU) for lower limb amputees during the level ground walking. Development of the algorithm is based on the shank angular velocity in the sagittal plane and linear acceleration signal in the shank longitudinal direction. System performance was evaluated with four control subjects (CS) and one transfemoral amputee (TFA) and the results were validated with four FlexiForce footswitches (FSW). The results showed a data latency for initial contact (IC) and toe off (TO) within a range of +/- 40 ms for both CS and TFA. A delay of about 3.7 +/- 62 ms for a foot-flat start (FFS) and an early detection of -9.4 +/- 66 ms for heel-off (HO) was found for CS. Prosthetic side showed an early detection of -105 +/- 95 ms for FFS whereas intact side showed a delay of 141 +/- 73 ms for HO. The difference in the kinematics of the TFA and CS is one of the potential reasons for high variations in the time difference. Overall, detection accuracy was 99.78% for all the events in both groups. Based on the validated results, the proposed system can be used to accurately detect the temporal gait events in real-time that leads to the detection of gait phase system and therefore, can be utilized in gait analysis applications and the control of lower limb prostheses.