A cost-effective gait analysis system without attachments and specialized large environments can provide useful information to determine effective treatment in clinical sites. This study investigates the capability of a single camera-based pose estimation system using OpenPose (OP) to measure the temporo-spatial and joint kinematics parameters during gait with orthosis. Eleven healthy adult males walked under different conditions of speed and foot progression angle (FPA). Temporo-spatial and joint kinematics parameters were measured using a single camera-based system with OP and a three-dimensional motion capture system. The limit of agreement, mean absolute error, absolute agreement (ICC _{2, 1} ), and relative consistency (ICC _{3, 1} ) between the systems under each condition were assessed for reliability and validity. The results demonstrated that most of the ICC for temporo-spatial parameters and hip and knee kinematics parameters were good to excellent (0.60 - 0.98). Conversely, most of the ICC for ankle kinematics in all conditions were poor to fair (< 0.60). Thus, the gait analysis using OP can be used as a clinical assessment tool for determining the temporo-spatial, hip, and knee sagittal plane angles during gait.

A markerless gait analysis system can measure useful gait metrics to determine effective clinical treatment. Although this gait analysis system does not require a large space, several markers, or time constraints, it inaccurately measure lower limb joint kinematics during gait. In particular, it has a substantial ankle joint angle error. In this study, we investigated the markerless gait analysis method capability using single RGB camera-based pose estimation by OpenPose (OP) and an inertial measurement unit (IMU) sensor on the foot segment to measure ankle joint kinematics under various gait conditions. Sixteen healthy young adult males participated in the study. We compared temporo-spatial parameters and lower limb joint angles during four gait conditions with varying gait speeds and foot progression angles. These were measured by optoelectronic motion capture, markerless gait analysis method using OP, and proposed method using OP and IMU. We found that the proposed method using OP and an IMU significantly decreased the mean absolute errors of peak ankle joint angles compared with OP in the four gait conditions. The proposed method has the potential to measure temporo-spatial gait parameters and lower limb joint angles, including ankle angles, in various gait conditions as a clinical settings gait assessment tool.

An ankle-foot orthosis (AFO) with a plantarflexion resistance function, improves post-stroke gait. An AFO with a plantarflexion resistance function not only affects the first rocker function and the weight acceptance but also the late stance phase. Achilles tendon extension is important for ankle joint function and for forward propulsion during the late stance phase; however, the effect of an AFO with a plantarflexion resistance function on the Achilles tendon is unclear. The purpose of this study was to investigate the effect of plantarflexion resistance on the extension of the Achilles tendon and the forward-propulsive force. Herein, 10 healthy adult males participated who walked under three different conditions: a no-AFO condition and two AFO conditions that had different levels of plantarflexion resistance (P1 and P2). The stiffness value of the P1 and P2 conditions was 0.56 and 1.47 Nm/°, respectively. A three-dimensional (3D) motion analysis system and a musculoskeletal model were used to assess the tendon-length change, the ground reaction force, kinematics, and kinetics data. The change in Achilles tendon length was significantly lower in the P1 and P2 conditions than the no-AFO condition. Furthermore, changes in the length of the Achilles tendon significantly decreased in the P2 condition when compared with that in the P1 condition. The peak anterior ground reaction force was significantly lower in the P2 condition than the no-AFO condition. These results suggest that excessive assist provided by an AFO prevents efficient gait by decreasing both the forward-propulsive force and tendon function.

Mechanical testing and gait measurement for ankle-foot orthosis (AFO) are crucial for determining the AFO stiffness magnitude in an individual. However, information on the effect of the stiffness magnitude on the muscle force during gait is limited. This study aimed to investigate the relationship between the AFO stiffness and ankle muscle force during gait. The AFO stiffness was mechanically tested using a six-axis robot arm. The stiffness magnitude was adjusted using different spring constants. Five stiffness conditions were set for each plantarflexion resistive (PFR) and dorsiflexion resistive (DFR) function. The effect of the PFR and DFR on the ankle muscle force during gait were determined using musculoskeletal and AFO models. Tibialis anterior (TA) and triceps surae (TS) muscle forces were calculated through gait simulation. The angle-moment relationships display hysteresis loops for each condition. One of the PFR and DFR conditions differed significantly from the others (for all, p < 0.05). In order of lower stiffness, the each PFR contribution ratio to the peak TA muscle force normalized in the no-stiffness condition was 8.4%, 10.8%, 11.3%, 13.5%, and 15.3%; while the each DFR contribution ratio to the peak TS muscle force was 16.2%, 20.9%, 25.3%, 29.8%, and 30.5%, respectively. Through mechanical testing as well as gait simulation, it was demonstrated that the magnitude of the AFO stiffness decreased the required ankle muscle force during gait. This study can contribute to more effective gait rehabilitation using AFO as well as AFO fabrication with customized stiffness for individual gait function.