Ambulatory Assessment of Ankle and Foot Dynamics

Abstract

Ground reaction force (GRF) measurement is important in the analysis of human body movements. The main drawback of the existing measurement systems is the restriction to a laboratory environment. This paper proposes an ambulatory system for assessing the dynamics of ankle and foot, which integrates the measurement of the GRF with the measurement of human body movement. The GRF and the center of pressure (CoP) are measured using two six-degrees-of-freedom force sensors mounted beneath the shoe. The movement of foot and lower leg is measured using three miniature inertial sensors, two rigidly attached to the shoe and one on the lower leg. The proposed system is validated using a force plate and an optical position measurement system as a reference. The results show good correspondence between both measurement systems, except for the ankle power estimation. The root mean square (RMS) difference of the magnitude of the GRF over 10 evaluated trials was (0.012 0.001) N/N (mean standard deviation), being (1.1 0.1)% of the maximal GRF magnitude. It should be noted that the forces, moments, and powers are normalized with respect to body weight. The CoP estimation using both methods shows good correspondence, as indicated by the RMS difference of (5.1 0.7) mm, corresponding to (1.7 0.3)% of the length of the shoe. The RMS difference between the magnitudes of the heel position estimates was calculated as (18 6) mm, being (1.4 0.5)% of the maximal magnitude. The ankle moment RMS difference was (0.004 0.001) Nm/N, being (2.3 0.5)% of the maximal magnitude. Finally, the RMS difference of the estimated power at the ankle was (0.02 0.005) W/N, being (14 5)% of the maximal power. This power difference is caused by an inaccurate estimation of the angular velocities using the optical reference measurement system, which is due to considering the foot as a single segment. The ambulatory system considers separate heel and forefoot segments, thus allowing an additional foot moment and power to be estimated. Based on the results of this research, it is concluded that the combination of the instrumented shoe and inertial sensing is a promising tool for the assessment of the dynamics of foot and ankle in an ambulatory setting.

Influence of the instrumented force shoe on gait pattern in patients with osteoarthritis of the knee

“…However, the need for a special gait laboratory, the line of sight problems of optical markers, the restricted measurement volume, and high costs limit the clinical use of such lab-based systems. Furthermore, the need for (multiple) constrained foot placements on the force plates to measure the GRF could introduce adaptation of the gait pattern, which compromises the validity of the measurements [22,36,46].…”

“…However, for an accurate measurement of kinetics such as the KAdM, or other lower extremity net joint moments, it is necessary to also measure the GRF and centre of pressure (CoP). For ambulatory assessment of GRF, an instrumented force shoe (IFS) has recently been developed [36]. The IFS is an orthopaedic sandal, equipped with two 6-degrees-of-freedom force/moment sensors under the heel and forefoot, respectively, which a sensor unit of the IMMS attached to each force sensor, at the lateral side of the sandal.…”

Relationship between sagittal plane kinematics, foot morphology and vertical forces applied to three regions of the foot

“…These include a combined force platform and pressure mat (Abuzzahab et al 1997;Boyd et al 1997;MacWilliams et al 2003;Sawacha et al 2012), a piezo-dynamometric integrated platform (Giacomozzi et al 2000) and an array of fibreoptic sensors (Wang et al 2005). Instrumented footwear capable of measuring footwear sub-area loading has also been described (Schepers et al 2007;Liu et al 2014). Whilst promising results have been reported for each of these methods, all require a pressure mat or alternative custom-made device not typically employed as part of a standard gait analysis protocol (Simon 2004).…”

Mobile Sensors for Robotics Research

“…Liedtke et al proposed a combination sensor system including six degrees of freedom force and moment sensors and miniature inertial sensors (provided by Xsens Motion Technologies) to estimate the joint moments and powers of the ankle (Liedtke et al, 2007). If 3D orientations of the foot are obtained and integrated with measured triaxial GRF during gait, an inverse dynamic method can be used to implement joint dynamics analysis of the lower limb (Schepers et al, 2007). We are presently concentrating on the development of some wearable sensors to measure human GRF and segment orientations during gait.…”