Isokinetic Robotic Device to Improve Test-Retest and Inter-Rater Reliability for Stretch Reflex Measurements in Stroke Patients with Spasticity

Summary

Using a robotic isokinetic device with electromyography (EMG) measurements, this protocol illustrates that isokinetic motion itself can improve inter-rater reliability for the angle of catch measurements in stroke patients with mild elbow flexor spasticity.

Abstract

Measuring spasticity is important in treatment planning and determining efficacy after treatment. However, the current tool used in clinical settings has been shown to be limited in inter-rater reliability. One factor in this poor inter-rater reliability is the variability of passive motion while measuring the angle of catch (AoC) measurements. Therefore, an isokinetic device has been proposed to standardize the manual joint motion; however, the benefits of isokinetic motion for AoC measurements has not been tested in a standardized manner. This protocol investigates whether isokinetic motion itself can improve inter-rater reliability for AoC measurements. For this purpose, a robotic isokinetic device was developed that is combined with surface electromyography (EMG). Two conditions, manual and isokinetic motions, are compared with the standardized method to measure the angle and subjective feeling of catch. It is shown that in 17 stroke patients with mild elbow flexor spasticity, isokinetic motion improved the intraclass correlation coefficient (ICC) for inter-rater reliability of AoC measurements to 0.890 [95% confidence interval (CI): 0.685–0.961] by the EMG criteria, and 0.931 (95% CI: 0.791–0.978) by the torque criteria, from 0.788 (95% CI: 0.493–0.920) by manual motion. In conclusion, isokinetic motion itself can improve inter-rater reliability of AoC measurements in stroke patients with mild spasticity. Given that this system may provide greater standardized angle measurements and catch of feeling, it may be a good option for the evaluation of spasticity in a clinical setting.

Introduction

Spasticity after stroke is common and has been shown to induce complications, including pain and contractures, resulting in reduced quality of life^1,2,3. Measurement of spasticity is important to properly plan the course of treatment and determine the efficacy of treatment. Commonly used tools in the clinical setting are the Modified Ashworth scale (MAS)⁴, which is a nominal measurement system for resistance to passive movement, and the modified Tardieu scale (MTS), which measures the angle of catch (AoC), representing the velocity-dependent characteri....

Protocol

1. Experimental set-up

1. Patient recruitment
   NOTE: All procedures were reviewed and approved by the Seoul National University Bundang Hospital Institutional Review Board. These subjects were inpatients or outpatients with stroke diagnoses from four rehabilitation hospitals in the region.
   1. Perform the screening process using the following inclusion criteria: (1) upper extremity hemiparesis due to stroke; (2) over the age of 20 years; (3) mild elbow joint spasticity of MAS 1-2; (4) no previous disease affecting function of the hemiparetic arm, except for stroke; (5) free from hemodynamic instability; (6) no severe elbow contr....

Results

The reliability is divided into four grades according to the ICC value: extremely excellent (>0.90), excellent (0.75 < ICC ≤ 0.90), fair to good (0.40 < ICC ≤ 0.75), and poor (<0.40). The standard error of measurements (SEM) was calculated to determine the error component of the variance. The smallest detectable difference (SDD) was calculated from the SEM of test-retest data.

Normalized assessment motion index (NAMI): the NAMI score during an isokinetic motion was .......

Discussion

This study attempted to standardize the MTS measurement using a robotic isokinetic device. It was investigated how the consistency of assessment motion affects the results of MTS measurement.

The NAMI value was proposed to represent the degree of variability in assessment motion. As expected, unlike the isokinetic motion method with no variability, the manual method showed variability between tests and between raters, resulting in poor reliability, which is consistent with results from previou.......

Materials

Name	Company	Catalog Number	Comments
3D printer	Lokit	3Dison+	FDA type 3D printer
Ball sprine shaft	Misumi	LBF15
Bridge Analog Input module	National Instruments	NI 9237
CAN communication module	National Instruments	NI 9853
Caster	Misumi	AC-50F
Electromyography (EMG) device	Laxtha	WEMG-8
EMG electrode	Bioprotech		1.8x1.2 mm Ag–AgCl
Encoder	Maxon	HEDL 9140	500 CPT
Gearbox	Maxon	GP 81	51:1 ratio
Lab jack	Misumi	99-1620-20
Linear slider	Misumi	KSRLC16
Motor	Maxon	EC-60	brushless EC motor
Motor driver	Elmo	DC Whistle
PLA	Lokit		3D printer material
Real-time processor	National Instruments	sbRIO-9632
Torque sensor	Transducer Techniques	TRS-1K