The use of rubber foam pads and "sensory ratios" to reduce variability in static posturography assessment

Despite the numerous works published, static posturography has still a limited clinical use due to its intrinsic inter-individual high variability. For this reason, foam pads have been introduced but their use is still not standardized. Aim of the study was to define the variability of static posturography parameters in standard and foam standing. Methods: 50 healthy subjects were studied with static posturography in four standing conditions: eyes open (EO) and eyes closed (EC), with and without foam pads. Unstable tests have been performed with two different types of rubber foam pads placed on the force platform. ‘‘Sensory ratios’’ have been calculated by the ratio of sway length among the four different conditions, adapted from dynamic posturography, in order to measure the relative contributions of vestibular, visual and somatosensory inputs. Results: Static posturography in standard conditions showed unacceptable coefficients of variation (>than 15%) for all the parameters. The use of foam pads reduced the high intrinsic variability, in particular for LFS (12.6–15.4%). The use of ‘‘sensory ratios’’ led to decrease the inter-subject coefficient of variation of this measurement to about 9.47–14.42% using the bilayer foam pads. Conclusions: Further studies are needed to confirm these data by applying the ratio formulas in clinical practice.