Table II.
Parameters, explanation, graphic representation of the posturographic test and the normal values supplied by the instrument.
| Parameter | Explanation | OE (Normal Value) | CE (Normal Value) | CER (Normal Value) | |
|---|---|---|---|---|---|
| X min, max, mean, SD (mm) | Measurement of centre of gravity shift on the frontal plane (right-left) and the relative standard deviation (SD)) | Xmin Xmax Xmean |
From -19.1 to 5.9 From -5.4 to 20.2 From -11.9 to 12.5 |
From -22.3 to 5.9 From -8.1 to 24.6 From -11.3 to 12.7 |
From -23.8 to 6.2 From -6.2 to 25.4 From -12.6 to 13.9 |
| Y min, max, mean, SD (mm) | Measurement of centre of gravity shift on the sagittal plane (back/forth) and the relative standard deviation (SD) | Ymin Ymax Ymean |
From -74.0 to -13.2 From -55.0 to 2.6 From -64.0 to -6.4 |
From -76.2 to -15.2 From -51.2 to 2.8 From -62.4 to -6.8 |
From -53.8 to -32.6 From -48.1 to -9.5 From -59.6 to -2.8 |
| S: surface of the ellipse with 90% (mm2) | Surface of the ellipse containing 90% of the sampled points; expresses postural system precision | S | From 0 to 280.0 | From 0 to 426.0 | From 0 to 560.2 |
| L: total length of the recording (mm) | Length of the connecting subsequent positions of the centre of gravity. | L | From 148.8 to 531.2 | From 120.3 to 832.7 | From 113.6 to 940.9 |
| V and SD: mean velocity and SD (mm/sec) | Velocity of the shift from the centre of gravity and the relative standard deviation (SD) | SD | From 1.4 to 7.4 | From 1.0 to 11.5 | From 1.4 to 12.6 |
| LFS: length in function of S | Value expressing the energy spent in relation to the precision of the postural system | - | - | - | - |
| RI: Romberg Index | Quotient between the previous 6 values measured with eyes closed and the corresponding values with eyes open | - | - | - | - |
| Stabilogram (mm) | Graphic representation of the shifts from the centre of gravity on the two axes in relation to time | - | - | - | - |
| Statokinesigram (mm) | Graphic representation of the projection of the postural oscillations on the support polygon. | - | - | - | - |
| FFT: Fast Fourier Transform (Hz)* | Transformation of the oscillation signal on the two axes (X – Y) in the frequency dominion | - | - | - | - |
*
The FFT demonstrates the spectre of oscillations, where the amplitude is proportional to the degree of energy in that particular frequency. The oscillation in the pressure centre, detected by means of Stabilometry, can be considered an f(t) function that is non-periodic but one that is limited to the t time and which, consequently, can be an analysed by Fourier's integral. The oscillations on the two axes are evaluated separately and the highest frequency found is attributed 100 while the others are expressed in percentages.