Validation of Centre of Pressure Trajectory from a Portable Gait System

Abstract

In New Brunswick, an average of eight seniors are admit-ted to hospital each day for a fall-related injury, costing the New Brunswick health care system almost $250M per year and representing the largest single contributor to injury-related health care costs in the province. Although interna-tional fall-risk assessment guidelines exist for identifying seniors at risk of falls, they are subjective and rarely employ technology. StepScan™ (Charlottetown PE) pressure sensi-tive tiles offer a potential solution for integrating portable technology into routine falls-risk assessment that can be performed in community clinics or the home; however, have not yet been subjected to head-to-head comparison with an accepted “gold standard” measurement system, for suitable tests of mobility and balance. The aims of this study were to fill this gap in knowledge. Fifteen healthy participants per-formed quiet standing, 5-times sit-to-stand task, and a sur-rogate test for walking – the step-up/step/down task, on the StepScan™ pressure tiles mounted on top of in-floor, rail mounted AMTI (Amherst MA) force plates in a motion analysis laboratory. Simultaneous registered trajectories of the centre of pressure (CoP) during standing and stepping tasks were compared for accuracy in global position (ran-dom error + bias) and relative position (random error only). Slow tasks such as standing had high bias (>20mm) but very good accuracy (1-2mm). Moderate speed tasks such as the 5-times sit-to-stand also had high bias (>20mm) but did not have acceptable accuracy (>15mm). Rapid stepping tasks had very low bias (<2mm) and acceptable accuracy (4-7mm). We conclude that StepScan™ CoP measurements have excel-lent precision for static balance assessment, and acceptable precision and trueness during a rapid stepping task, but limitations may exist for motor tasks such as the sit-to-stand. The variable bias observed for the different standing and stepping tasks is highly curious and requires more study.