Accuracy and reliability of haptic spasticity assessment using HESS (Haptic Elbow Spasticity Simulator)

Clinical assessment of spasticity tends to be subjective because of the nature of the in-person assessment; severity of spasticity is judged based on the muscle tone felt by a clinician during manual manipulation of a patient's limb. As an attempt to standardize the clinical assessment of spasticity, we developed HESS (Haptic Elbow Spasticity Simulator), a programmable robotic system that can provide accurate and consistent haptic responses of spasticity and thus can be used as a training tool for clinicians. The aim of this study is to evaluate the accuracy and reliability of the recreated haptic responses. Based on clinical data collected from children with cerebral palsy, four levels of elbow spasticity (1, 1+, 2, and 3 in the Modified Ashworth Scale [MAS]) were recreated by HESS. Seven experienced clinicians manipulated HESS to score the recreated haptic responses. The accuracy of the recreation was assessed by the percent agreement between intended and determined MAS scores. The inter-rater reliability among the clinicians was analyzed by using Fleiss's kappa. In addition, the level of realism with the recreation was evaluated by a questionnaire on “how realistic” this felt in a qualitative way. The percent agreement was high (85.7±11.7%), and for inter-rater reliability, there was substantial agreement (κ=0.646) among the seven clinicians. The level of realism was 7.71±0.95 out of 10. These results show that the haptic recreation of spasticity by HESS has the potential to be used as a training tool for standardizing and enhancing reliability of clinical assessment.