Effect of an ankle–foot orthosis on gait kinematics and kinetics: case study of post-stroke gait using a musculoskeletal model and an orthosis model

Abstract

One of the recommended post-stroke gait rehabilitation treatments is the use of an ankle-foot orthosis. In clinical practice, it is important to adjust the torque of the ankle-foot orthosis assistance to suit each patient's body function and gait ability. The present study aimed to investigate the effect of changing the plantar flexion resistance of the ankle-foot orthosis on the post-stroke gait kinematics and kinetics during the early stance phase using a musculoskeletal model and an ankle-foot orthosis model. The subject was a male with post-stroke left hemiplegia who could walk independently without an ankle-foot orthosis and/or cane. The subject walked at a self-selected speed under the no ankle-foot orthosis condition and three ankle-foot orthosis conditions, each with a different plantar flexion resistive torque. A motion analysis system was used to measure the following spatiotemporal parameters: gait speed, step length, cadence, and step length ratio. In addition, the ankle angle of the paretic side, ankle torque of the paretic side, and plantar flexion resistance torque of the ankle-foot orthosis were calculated using a musculoskeletal model and an ankle-foot orthosis model. The results showed that the gait speed and step length ratio of all ankle-foot orthosis conditions were improved compared with the no ankle-foot orthosis condition. In particular, the condition with the smallest torque was the most symmetric of the four walking conditions. The condition with the smallest torque also resulted in the greatest increase in the dorsiflexion angle of the paretic side at heel contact. The internal dorsiflexion torque was most increased in the ankle-foot orthosis condition with the smallest torque for this subject. The simulation of the post-stroke gait in the present study contributes to the development of more effective gait rehabilitation treatment methods using an ankle-foot orthosis.

Modelling the interaction between wearable assistive devices and digital human models—A systematic review

“…The interaction of the WAD and the DHM is realized by a rigid connection (Imamura et al, 2011;Ferrati et al, 2013;Lancini et al, 2016) resulting in no possible shift or rotation between the two partners. This connection is done by fixing one point of the device to one point of the model's corresponding bone (e.g., in the MHM simulation software OpenSim (Delp et al, 2007;Seth et al, 2011;Seth et al, 2018) this is done by a weldJoint (Yamamoto et al, 2021) or via a constraint (Ferrati et al, 2013)) and thereby matching the device to the human's anatomy (see Figure 3.2) (Ferrati et al, 2013;Michaud et al, 2019;Yamamoto et al, 2021). Kruif et al (2017) even align the WAD to the model's bones, in other words assumes the device to be integrated into the human kinematical system.…”

“…Kruif et al (2017) even align the WAD to the model's bones, in other words assumes the device to be integrated into the human kinematical system. In this classification the effect of the inserted WAD is either determined by the set stiffness of the device resulting in a force being applied to the fixation points of device and model (Ferrati et al, 2013;Tröster et al, 2020;Yamamoto et al, 2021) or by applying an external force or torque equally to group 1 (Kruif et al, 2017;Yin et al, 2019;Gordon et al, 2022).…”

“…For example, trying to model the shown example of the orthosis (Figure 3-interaction type 2) in OpenSim by applying a weldJoint between both orthosis parts and the corresponding bone (shank and foot) and a rotational joint between both orthosis parts results in a non-viable kinematic chain. A solution could be the use of a constraint as replacement for one weldJoint as done by Kruif et al (2017) or by combining both parts with other modelling solutions than a joint (Yamamoto et al, 2021). The suitable workaround depends essentially on the use case and WAD that should be modelled.…”

Machine learning analysis to predict the need for ankle foot orthosis in patients with stroke

“…Weakness on ankle dorsiflexion is one of the major causes of gait disturbance after stroke, which results in instability of the ankle during the stance phase and reduced clearance during the swing phase 4 , 5 . For patients with weakness on ankle dorsiflexion, an ankle–foot orthosis (AFO) is commonly applied, which can provide medial–lateral stability at the ankle during the stance phase, and improve clearance during the swing phase 4 , 6 .…”

Development and Preliminary Evaluation of a Lower Body Exosuit to Support Ankle Dorsiflexion

“…Many studies examined the influence of AFOs on post-stroke hemiparetic gait with drop foot. Studies found improved toe clearance [7], balance [8][9][10] and gait velocity [11], which was associated with a more self-confident gait [12], lower fear [13] and lower risk of falling.…”