Standing margin of stability as a measure of balance for people with multiple sclerosis.

Abstract

Multiple Sclerosis (MS) is an autoimmune disease of the central nervous system, which can impact postural control. The Margin of Stability (MoS) is a biomechanical measure of how close someone is to falling without corrective action. Walking MoS has been extensively studied in people with MS (PwMS), while standing MoS is less studied. This work explores the relationship between the standing MoS and clinical measures, identifying a standing MoS summary feature that quantifies the level of balance impairment due to MS, across a range of stances. In an observational study, participants stood in five stances, with different bases of support, each for 30 s. Standing MoS was calculated using motion capture data and compared with established clinical scales. Ninety-six PwMS (EDSS: 1.5-6.5) completed at least one stance. The range and standard deviation of the Global (two-dimensional) standing MoS were significantly correlated (p < 0.05) with MS-related impairment (EDSS) in all but one stance. Correlations were also found between the Standing MoS and patient-reported outcomes: ABC and MSWS-12. The range of Global MoS demonstrated strong known-group validity (p < 0.001), distinguishing mild from moderate and severe MS across all stances. There are strong correlations between the standing MoS and established clinical scales. MSWS-12 has the weakest correlations as it is designed to capture information relevant to walking, not standing. The range of the Global MoS should be used for standing MoS studies involving PwMS. The standing MoS could be explored for use as a trial outcome measure or clinical scale.