Lower limb spasticity assessment using an inertial sensor: a reliability study

Spasticity is a common motor impairment in patients with neurological disorders that can prevent functional recovery after rehabilitation. In the clinical setting, its assessment is carried out using standardized clinical scales. The aim of this study was to verify the applicability of inertial sensors for an objective measurement of quadriceps spasticity and evaluate its test-retest and inter-rater reliability during the implementation of the Wartenberg pendulum test. Ten healthy subjects and 11 patients in vegetative state with severe brain damage were enrolled in this study. Subjects were evaluated three times on three consecutive days. The test-retest reliability of measurement was assessed in the first two days. The third day was devoted to inter-rater reliability assessment. In addition, the lower limb muscle tone was bilaterally evaluated at the knee joint by the modified Ashworth scale. The factorial ANOVA analysis showed that the implemented method allowed us to discriminate between healthy and pathological conditions. The fairly low SEM and high ICC values obtained for the pendulum parameters indicated a good test-retest and inter-rater reliability of measurement. This study shows that an inertial sensor can be reliably used to characterize leg kinematics during the Wartenberg pendulum test and provide quantitative evaluation of quadriceps spasticity.