This paper tackles the problem of analysing the variability of the experimental data provided by the AUSCAN System, an opto-electronic measurement device for the detection of the 3-D spinal geometry during static and dynamic posture. Various sources of data variability, ranging from pure errors of detection up to physiological variations of the spinal morphology due the control mechanism of posture, have been considered. The final results of this study show that the dynamic component of posture, associating with the motor-posture control system, causes the largest variability in the measure of the spinal morphology.