Portable measurement system for the objective evaluation of the spasticity of hemiplegic patients based on the tonic stretch reflex threshold

The clinical scales used for the evaluation of the spasticity have some drawbacks, in spite of their simplicity and ease of assessment, and their inter- and intra-rater reliability remains controversial. The aim of this study is to develop a portable system for the objective and reliable evaluation of the spasticity based on the K-means clustering of the tonic stretch reflex threshold (TSRT) and to compare the discrimination performance of the level of spasticity determined by our method with that by the conventional modified Ashworth scale (MAS). Fifteen hemiplegic patients (7 males and 8 females, age: 63.5 ± 15.6) participated in the study. The average and standard deviation values of the TSRTs were 127.9 ± 1.6, 121.8 ± 1.5 and 117.9 ± 1.3 in groups G1, G2 and G3, respectively, and there were significant differences between the TSRTs of each group (p < 0.05). Also, our groups classified by the criteria of the TSRT had a strong negative correlation (r = −0.95, r2 = 0.90, p < 0.05) between the level of spasticity and TSRTs. These results demonstrated that our system could be clinically more useful for the quantitative and reliable discrimination of the spasticity than the conventional MAS.