Measures of postural stability.

Dynamic posturography has become an important tool for understanding standing balance in clinical settings. A key test in the NeuroCom International (Clackamas, Oregon) dynamic posturography system, the Sensory Organization Test (SOT), provides information about the integration of multiple components of balance. The SOT test leads to an outcome measure called the "equilibrium score" (ES), which reflects the overall coordination of the visual, proprioceptive, and vestibular systems for maintaining standing posture. Researchers, therapists, and physicians often use the ES from the SOT as a clinically relevant measure of standing balance. We discuss here the formula used for evaluating the ES and propose an additional measure of postural stability, called the Postural Stability Index (PSI), that accounts for shear force and individual anthropomorphic measures. We propose that this new measure provides a clinically important adjunct to the current SOT and can be calculated from data already collected by the NeuroCom forceplate during the SOT.