A new method of characterising gait using a portable, real-time, ultrasound ranging device

Abstract

A portable gait analysis system is presented. The device uses direct ultrasound ranging to measure the distance between a base unit and a transponder worn by the subject at the approximate body center of mass. As the subject progresses away from the base unit distance samples are saved and displayed in real time on a computer screen. Immediately following a walking trial these saved distance samples are used to calculate the instantaneous horizontal velocity or the gait velocigram (GVG). The GVG can be considered to be a pictorial representation of that person's gait. Gait parameters such as average walking speed, cadence, stride time, stride length, the step lengths and times for each leg and the peak-to-peak fluctuation of the instantaneous velocity can all be readily calculated from the GVG. The power of this device is that it provides gait data in real-time, enabling a clinician to implement ideas or changes and then to immediately see effect of those ideas or changes on that person's gait. Our direct ultrasound ranging system (DURS) has application in the area of outcome measures for implant or corrective gait surgery as well as in the area of lower limb prosthetic alignment.