VALIDITY, INTRA-RATER RELIABILITY AND NORMATIVE DATA OF THE NEUROFLEXORTM DEVICE TO MEASURE SPASTICITY OF THE ANKLE PLANTAR FLEXORS AFTER STROKE

Objective: Quantification of lower limb spasticity after stroke and the differentiation of neural from passive muscle resistance remain key clinical chal-lenges. The aim of this study was to validate the novel NeuroFlexor foot module, to assess the intra-rater reliability of measurements and to identify normative cut-off values.Methods: Fifteen patients with chronic stroke with clinical history of spasticity and 18 healthy subjects were examined with the NeuroFlexor foot module at controlled velocities. Elastic, viscous and neural components of passive dorsiflexion resistance were quantified (in Newton, N). The neural component, reflecting stretch reflex mediated resistance, was validated against electromyography activity. A test-retest design with a 2-way random effects model permitted study of intra-rater reliability. Finally, data from 73 healthy subjects were used to establish cut -off values according to mean + 3 standard deviations and receiver operating characteristic curve analysis.Results: The neural component was higher in stroke patients, increased with stretch velocity and corre-lated with electromyography amplitude. Reliability was high for the neural component (intraclass cor-relation coefficient model 2.1 (ICC2,1) >= 0.903) and good for the elastic component (ICC2,1 >= 0.898). Cut -off values were identified, and all patients with neu-ral component above the limit presented pathological electromyography amplitude (area under the curve (AUC) = 1.00, sensitivity = 100%, specificity = 100%).Conclusion: The NeuroFlexor may offer a clini-cally feasible and non-invasive way to objectively quantify lower limb spasticity.

Automated summary

The study aimed to validate the NeuroFlexor foot module and assess its intra-rater reliability, as well as establish normative cut-off values. Patients with chronic stroke and healthy subjects were examined using the NeuroFlexor at controlled velocities. Results showed that the neural component was higher in stroke patients, increased with stretch velocity, and correlated with electromyography amplitude. Cut-off values were established based on data from healthy subjects. Overall, the NeuroFlexor may provide a feasible and non-invasive method for quantifying lower limb spasticity.