Biomedical subjects

Zhiming Ji

Publications and source records attributed to Zhiming Ji.

3 recordsLinked to original sources

PubMed2004

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.

Adult↗

PubMed2004

Computational method to evaluate ankle postural stiffness with ground reaction forces.

We examined an existing method for evaluating postural sway based on force-plate technology. Through an improved mathematical model of postural dynamics, we propose a new method, which better evaluated postural sway and, in addition, computed ankle moment and ankle postural stiffness directly from the measured ground reaction forces. An example is detailed that demonstrates the utility of this approach. The proposed method does not involve filtering or numerical integration and considers the platform inclination. Results from normal subjects show a linear relation between the ankle moment and the sway angle during quiet standing.

Adult↗

PubMedDate not supplied

Postural stability index is a more valid measure of stability than equilibrium score.

Researchers, therapists, and physicians often use equilibrium score (ES) from the Sensory Organization Test, a key test in the NeuroCom EquiTest System (a dynamic posturography system) to assess stability. ES reflects the overall coordination of the visual, proprioceptive, and vestibular systems for maintaining standing posture. In our earlier article, we proposed a new measure of anterior-posterior (A-P) postural stability called the Postural Stability Index (PSI), which accounts for more biomechanical aspects than ES. This article showed that PSI provides a clinically important adjunct to ES. In the present article, we show that PSI can provide an acceptable index even if a person falls during the trial, whereas ES assigns a zero score for any fall. We also show that PSI decreases as ankle stiffness increases, which is intuitive, while ES exhibits the opposite behavior. Ankle stiffness is generally recognized as an indicator of postural stability. These results suggest that PSI is a more valid measure of A-P stability than ES.

Adult↗