An accelerometer-based objective assessment of spasticity: A simple pendulum model to evaluate outcome measures

Spasticity is one of the common motor disorders that occurs due to upper motor neuron defects in patients such as stroke, spinal cord injury, cerebral palsy, and multiple sclerosis. Its measurement is often done using standardized clinical scales. One of the salient problems associated with this symptom is poor objectivity in its assessment. Several methods have been proposed in the past two decades from which passive joint movement and the Wartenberg pendulum test are the most practical, promising, and sensitive to changes. The purpose of this study was to investigate the capability of accelerometer-based outcome measures in assessment of spasticity through pendulum test. We also aimed at evaluation of sensitivity to choice of sensor on outcome measures' strength in discriminating levels of spasticity. In this study we have simulated oscillating movement of dropped limb in various levels of spasticity by a simple pendulum and adjustable friction level. Our results show that acceleration-based outcome measures are as strong as angle-based counterparts and can reliably discriminate levels of spasticity in the whole range of severity (87% discrimination index). We also found that choice of accelerometer does not have noticeable effect on the performance of this objective method of spasticity assessment.