Upper limb stiffness assessment using REAplan in stroke patients

1. OBJECTIVE: To quantify upper limb stiffness in spastic patients using REAplan, a robotic device used in rehabilitation that can mobilize the patient's upper limb in a horizontal plane. 2. PATIENTS: Twelve chronic stroke patients with hemiplegia were recruited. Elbow flexor muscles spasticity was assessed with Modified Ashworth Scale (MAS), with a score greater than 1. 3. METHODS: Patients received an anaesthetic block of the musculo-cutaneous nerve, to reduce elbow flexor muscles spasticity. Each patient was assessed before and after the injection of the anaesthetic block and also the next day. Each time, stiffness was measured with the REAplan. The robot passively mobilized the patient’s upper limb at various speeds (10, 20, 30, 40 and 50 cm/s) in a back-and-forth trajectory (30 cm). For each speed condition, ten movements were performed. We recorded the force required to passively mobilize the patient’s upper limb. For the ten extension movements, stiffness were analyzed and averaged. 4. RESULTS: The results showed that the stiffness increased proportionally with the speed condition (p<0,001). For the anaesthetic effect, the results showed that the stiffness decreased just after the injection at 40 and 50 cm/s and increased until the initial values the next day (p<0,05). Finally, the stiffness results showed a good correlation with the MAS, for each speed condition greater than 20 cm/s (r>0,6). 5. CONCLUSION: This study develops and validates a protocol to quantify the upper limb stiffness, using the robot REAplan. This protocol, must be compared to other quantitative measures of spasticity in the future, and could be used to assess the effect of spasticity treatments (e.g. botulinum toxin).