Inertial Sensor-Based Lower Limb Joint Kinematics: A Methodological Systematic Review

Abstract

The use of inertial measurement units (IMUs) has gained popularity for the estimation of lower limb kinematics. However, implementations in clinical practice are still lacking. The aim of this review is twofold—to evaluate the methodological requirements for IMU-based joint kinematic estimation to be applicable in a clinical setting, and to suggest future research directions. Studies within the PubMed, Web Of Science and EMBASE databases were screened for eligibility, based on the following inclusion criteria: (1) studies must include a methodological description of how kinematic variables were obtained for the lower limb, (2) kinematic data must have been acquired by means of IMUs, (3) studies must have validated the implemented method against a golden standard reference system. Information on study characteristics, signal processing characteristics and study results was assessed and discussed. This review shows that methods for lower limb joint kinematics are inherently application dependent. Sensor restrictions are generally compensated with biomechanically inspired assumptions and prior information. Awareness of the possible adaptations in the IMU-based kinematic estimates by incorporating such prior information and assumptions is necessary, before drawing clinical decisions. Future research should focus on alternative validation methods, subject-specific IMU-based biomechanical joint models and disturbed movement patterns in real-world settings.

How We Found Our IMU: Guidelines to IMU Selection and a Comparison of Seven IMUs for Pervasive Healthcare Applications

“…By fusing information from these sensors, the orientation of the IMU can be estimated [1]. IMUs have been gaining popularity in the past years as a research tool for pervasive healthcare [2,3]. On the other hand, the selection of an IMU suitable for the research topic is also increasingly challenging due to the large variety of options.…”

A Novel Method to Estimate the Full Knee Joint Kinematics Using Low Cost IMU Sensors for Easy to Implement Low Cost Diagnostics

“…Despite the excellent possibilities for the use of IMUs in motion analysis, some crucial concerns and methodological problems need to be tackled especially to use them for estimation of joint kinematics. As stated in a review by Weygers et al [4], IMUs can be used to evaluate joint kinematics of the lower limb, but combined efforts of engineers and movement experts are still necessary to develop scripts to calculate joint angles based on gyroscope and accelerometer data, which is still a big challenge. Moreover, developed scripts need to be validated with a golden standard for motion analysis before implementation in clinical setting (e.g., patients, sportsmen, etc.…”

Gait Analysis in a Box: A System Based on Magnetometer-Free IMUs or Clusters of Optical Markers with Automatic Event Detection

“…However, in the MH-IMU configuration, the magnetometers can be disabled as the Fitbody process infers the heading of the IMUs, thus avoiding the adverse effects that disturbances in the magnetic field may cause. In addition, as Lebleu et al [38] explained, only a short time is required to capture the gait, and it is possible to repeat the Fitbody process before each capture, which is a sufficient procedure to overcome drift errors [33,53]. Figure 4 shows the Fitbody's effect on the human model.…”

“…In addition, recent research has revealed that the exploitation of kinematic constraints (such as boundary conditions in the degrees of freedom or the range of motion of the joints) can improve the heading calculation [45,46,[49][50][51][52]. The second drawback is that, when the magnetometer information is omitted, the cumulative gyro integration errors are not corrected, which results in drift errors that increase with the capture time [33,53]. The most straightforward approach for resolving the drift errors is to limit the capture time, which is appropriate when only a short period is required to execute the movements being investigated [38].…”