The effect of post-stroke lower-limb spasticity on the control of standing balance: Inter-limb spatial and temporal synchronisation of centres of pressure

Abstract

Background: Challenges in stability control are common post-stroke. Although lower-limb spasticity is a common sensorimotor consequence post-stroke, its potential to further complicate stability control among stroke-survivors remains largely unknown. Advancing such understanding can help inform strategies to reduce fall risk and increase independence among these individuals. The purpose of this study was to characterise the extent of limb-specific dyscontrol among individuals with spasticity.

Methods: A retrospective analysis of 131 patients assessed for spasticity was performed. Patients selected for inclusion were categorised into two groups, with (n=19) or without (n=63) unilateral lower-limb spasticity. Two force platforms were used to determine the individual-limb and net centres of pressure in both anteroposterior and mediolateral directions during 30s of quiet standing. Limb-specific dyscontrol was assessed by calculating weight-bearing symmetry ratios, cross-correlation coefficients at zero phase-shift (temporal synchrony) and ratios of individual-limb root-mean-square displacements (spatial symmetry). Total body postural control was assessed by examining the root-mean-square of the net centre of pressure displacement.

Findings: The group with spasticity bore less weight on the affected limb and exhibited reduced temporal synchrony of centre of pressure displacements. There were no differences in inter-limb root-mean-square centre of pressure ratios or in the root-mean-square of the net centre of pressure displacement.

Interpretation: Individuals with lower-limb spasticity may have additional challenges with stability control, specifically linked to the ability to modify the location of the centre of pressure beneath the affected limb, in a time-sensitive manner so as to contribute beneficially to the control of whole body stability.

Keywords: Lower extremity; Muscle spasticity; Postural balance; Rehabilitation; Stroke.