Clinical Assessment of Postural Stability

One of the most important applications of postural sway analysis is the detection of such impairments to the motor system that would allow us to predict risk of falling. Force plate posturography is a commonly used clinical method for the evaluation of postural instability. The diagnostic value of postural sway represented here by oscillations of the center-of-foot pressure (COFP) is being questioned very often. These diagnostic problems result from the lack of an adequate and reliable method of sway analysis — a method that would present a clear connection between stability and quality of postural control. To gain better insight into this problem, the following experiments were done and some effective methods of sway analysis typically applied in conventional mechanics and electrical engineering are presented here. Quality of the postural stability was assessed using, in addition to standard parameters, spatial histograms, body transfer function, contour plots as well as the COFP fractal dimension. Such complex analysis allowed us to extract significant sway parameters that are relevant to postural instability. Analysis of the data revealed that spatial histogram has clear peak which maximum was sensitive to sensory conditions. Changes in the postural sway distributions have been confirmed by the increase of the COFP fractal dimension.