Isometric Force Pillow: Using Air Pressure to Quantify Involuntary Finger Flexion in the Presence of Hypertonia

Abstract

Survivors of central nervous system injury commonly present with spastic hypertonia. The affected muscles are hyperexcitable and can display involuntary static muscle tone and an exaggerated stretch reflex. These symptoms affect posture and disrupt activities of daily living. Symptoms are typically measured using subjective manual tests such as the Modified Ashworth Scale; however, more quantitative measures are necessary to evaluate potential treatments. The hands are one of the most common targets for intervention, but few investigators attempt to quantify symptoms of spastic hypertonia affecting the fingers. We present the isometric force pillow (IFP) to quantify involuntary grip force. This lightweight, computerized tool provides a holistic measure of finger flexion force and can be used in various orientations for clinical testing and to measure the impact of assistive devices.

Relief of post-stroke spasticity with acute vibrotactile stimulation: controlled crossover study of muscle and skin stimulus methods

“…A digital goniometer was used to measure joint angles. The Isometric Force Pillow (IFP) (Seim et al, 2020) is an experimental tool used to measure involuntary grip force from the fingers. Flexor spastic hypertonia causes the fingers to squeeze and bend.…”