Measurement of asymmetric sitting posture using unstable board with accelerometer

Postural balance has a significant effect on activities in daily life continuously. The objective of this study was to evaluate the effect of pelvic asymmetry on postural balance during sitting. For accurate analysis, we developed sitting posture measurement system using unstable board with accelerometer. 5 pelvis asymmetry patients and 5 control subjects were participated in this study. Subjects were instructed to perform static and dynamic sitting. Angle variation in the frontal and sagittal plane as well as body pressure distribution of left and right side including maximum force, peak pressure, mean pressure, and area were assessed while sitting. Also, intra class correlation coefficient was used to evaluate the reliability of the system. In comparison with mean angular variation and pressure distribution between two groups, all parameters were more tilted to left side than right side in pelvic asymmetry group. And, the reliability of the measurement system was excellent in both static and dynamic sitting. From these results, we observed negative effect of pelvic asymmetry on postural balance and it can cause asymmetric sitting posture. This paper suggested that measuring method using unstable board with accelerometer may be suitable for evaluation of postural asymmetry, and this system can be utilized to provide useful information about patients with pelvic asymmetry in clinical medicine.