| Objective: The assessment of postural control using the displacement of the center of pressure (COP) is incapable when subjects are requested to stand on an inclined board. The aim of present study is to establish a CCD video camera system that record subjects' postural sway directly, with an analyzing software to figure out postural sway locus. By normalizing and comparing the locus with COP results, we make effort to evaluate human postural stability by trunk sway speed (TSS) or trunk sway angle (TSA), both of them can be acquired by analyzing the locus. Methods and materials: The system is composed of a CCD video camera, a video image capture board and analysis software. In practice, a black circular mark (32mm in diameter) is pasted on subjects' upper back using for record. The CCD video camera is set up on subject's back directory in the same high level with the mark and leaving it about 150cm. The video camera system records 35 seconds AVI format image acquired consecutive 349 frames (320 X 240 pixel, lOframe/sec). The system computespostural sway locus by tracing movements of the black mark and the locus represented subjects' left-right direction postural stray. For inter-individual comparability, the acquired postural sway locus is normalized as swaying at a high of 1 meter from the ground. Two indexes, TSS and TSA were used to describe postural stability. TSS represents trunk sway speed at the point of 1 meter high, and TSA represents angle scope of postural away. 22 healthy subjects (all were well informed and consented) took part in the examination, 11 females aged 42.8 years, and 11 males aged 39.1 years. Each subject was conducted 10 times 35Recond-period exams with eye-open alternated with eye-closed. During the examination, subjects stand on a COP measurement platform, relaxing their hands on both lateral sides of thighs, staring at a point 1 meter in front of them in the same high level. At last, the results of postural sway are compared with the results from COP examination and their correlation coefficient was calculated. Results: The averaged TSS of 22 subjects is 3.40 + 0.98mm/s in eyes open and 4. 70+1. 47mm/s in eyes closed. The averaged TSA is 1.05+0.29?in eyes open and 1.41+0.44?in eyes closed. The TSS increased 1. 30+ 0. 69mm/s (P<0. 01) and the TAS is 0.36 ?0. 23 " (P<0.01) when eyes closed. Romberg's rate (cyc-closcd /cyc-opcn) is 1. 39 + 0. 19 in TSS, 1. 35?. 21 in TSA. For COP examination, linear length of locus (LNG) is 12.57?3. 39mm/s in eyes open, 20. 50?5. 88mm/s in eyes closed. Romberg's rate is 1.64 + 0.25. in each case of examination, the value ofSD/AVG was also calculated in TSS, ISA and LNG, in order to compare the stability of each index in the same subject. More stable the value of SD/AVG is more suitable to reflex the equilibrium of body. The value of SD/AVG is 0.11+0.05 in TSS, 0.19 + 0.09 in TSA and 0.15 + 0.08 in LNG when eyes open; 0.14 + 0.08 in TSS, 0. 20 + 0. 08 in TSA and 0. 14 + 0. 06 in LNG when eyes closed. The value of SD/AVG in TSS is smallest, however have no significant difference with LNG, and the value of SD/AVG in TSA is largest. The correlation coefficient between TSS and LNG is 0.6321 in eyes open, 0.6841 in eyes closed; the correlation coefficient between TSA and LNG is 0.5382 in eyes open, 0.5053 in eyes closed. TSS shows moderate correlated with LNG larger than TSA. Conclusion: The CCD video camera system is suitable for postural stability measurement especially used the index of TSS and may become a prospective method for human beings balance ability evaluation. |
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