Dynamic gait stability index based on plantar pressures and fuzzy logic

Stability during locomotion, or dynamic stability, is critical to ensure safe locomotion and a high quality of life. A dynamic stability measure should be easily applied in a clinical setting and must provide a quantitative index that can be used for comparisons over a range of tasks and environments. Plantar foot pressure data acquired by shoe-insole sensors have potential to provide such a measure. To generate a quantitative dynamic gait stability index, six gait parameters were extracted from a commercial plantar pressure measurement system (F-Scan): anterior-posterior (A/P) center of force (CoF) motion, medial-lateral (M/L) CoF motion, maximum lateral position, cell triggering, stride time (ST), and double support time (DST). A fuzzy logic controller combined these six parameters and generated the index. To validate the stability index, 15 healthy subjects performed four tasks intended to induce increasing levels of instability. Fifty-seven gait parameter combinations were assessed to determine the most effective index. A combination of A/P motion, M/L motion, maximum lateral position, and cell triggering parameters was the most consistently effective index across all subjects. However, small changes in ST and DST for able-bodied subjects may have reduced the effectiveness of these measures in the index calculation. The index combining all six parameters should be investigated further with populations with disabilities or pathological gait.