Stability Analysis in Individuals with Complete and Incomplete Spinal cord Injury: Linear Versus Non-Linear Methods

Abstract

Background: Individuals with spinal cord injury (SCI) lose their abilities tostand. The effectiveness of compensating strategies such as the use of variousorthosis is studied by stability analysis. These kind of analyses are usuallystudied by linear method. In this study, the standing stability of complete andincomplete SCI individuals is evaluated by linear versus non-linear methods.Methods: Study groups consisted of 10 normal, 5 incomplete and 5 complete SCIindividuals. SCI participants stood with crutch and/or orthosis on a Kistler forceplate. The excursions of center of pressure (COP), velocity of COP, correlationdimension, and approximate entropy in the anteroposterior and mediolateralplanes were calculated in this study. Statistical analysis was done by one-wayANOVA and Post-hoc calculations by Tukey HSD.Results: Linear method revealed that the difference in “the mediolateral COP sway”and “anteroposterior COP velocity” was insignificant among the groups, whilstthe difference in “anteroposterior COP sway”, “mediolateral COP velocity” and“total velocity” was significant. In contrast, non-linear method revealed that thedifference in “mediolateral embedding diversion”, “anteroposterior embeddingdiversion”, “mediolateral correlationdimension” and “anteroposterior ApEn”was insignificant among the groups, whilst the difference in “anteroposteriorcorrelation dimension” and “mediolateral ApEn” was significant.Conclusion: Based on linear method, the stability of SCI subjects seems to belike normal subjects. However, non-linear analysis revealed that although SCIpatients knew how to put their body in a good posture to have a stable position,they had no abilities to control their posture.