Kinematic Analysis of Plastic Ankle-Foot Orthosis Using Force Sensors

In this study, we aimed to understand the dynamics of a lower limb plastic ankle-foot orthosis (PAFO) during walking in terms of the extent to which it assists or restricts the user’s gait. For this propose, we developed a load measurement system that can directly measure the loading on the PAFO. The system is worn by the user and incorporates four sensors: six-axis force sensors at three points (two in the shoe sole and one in the orthosis) and a single-axis force sensor at the ankle. The top section of a PAFO was divided into upper and lower sections at the back, essentially eliminating its deformation during walking, and a six-axis force sensor was incorporated at this point. The two six-axis force sensors were placed between the orthosis and the shoe (one at the tip of the toes and one at the heel). These sensors allowed for measuring all external forces applied to the orthosis during walking. By using a PAFO incorporating the developed measurement system, in this study we investigated the behavior of the forces applied to the orthosis with respect to variations in walking conditions, namely cadence (gait speed) and stride length.