A New Toolkit For Measuring Spasticity: A Pilot Study Investigating The Validity And Reliability Of The Biotone System For Patients Post-Stroke
Aloraini, Saleh M.
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Purpose: This pilot study assessed the concurrent and construct validity and test-retest reliability of the BioTone system as a tool to quantify spasticity in patients following stroke. Methods: 15 adults post-stroke (65±11 years, 11 males) with spasticity in upper and/or lower limb muscles participated. The BioTone system was used to measure spasticity elicited during fast (120-140 deg/sec) passive stretching of bilateral elbow flexors, elbow extensors and knee extensors. Spastic reaction onset time, angular velocity at onset (ΔV) and acceleration at onset (ΔA) were determined by analyzing, using MATLAB, departures of electrogoniometric data from a theoretical kinematic model based on a constant jerk profile. In addition, the root mean square departure for angular velocity (εV) and acceleration (εA) were calculated. EMG recordings were also analyzed to identify spastic reaction onset time, discrete change in EMG intensity and EMG amplitude density of the stretched muscle (ΔStr, εStr) and its antagonist (ΔNStr, εNStr). Other variables from the theoretical curve, which were the maximum velocity and absolute maximum acceleration of the theoretical model (MAX-V and MAX-A) and the root mean square of the theoretical model angular velocity and acceleration (V and A), were derived to determine the construct validity by comparing them to the corresponding variables obtained from the movement curve of the non-hemiparetic side. For knee extensor muscles, the relaxation index (RI) was calculated using the pendulum test. Relationships between the biometric results and the Modified Ashworth Scale (MAS) and Tardieu scale (TS) were explored. Test-retest reliability of all measurements was conducted with six participants, using an inter-test interval of <1 week. Results: Most participants displayed mild spasticity. Significant correlations were found in MAX-A and V of elbow flexors calculated using the theoretical profile and the non-hemiparetic side as references (rho=0.66, p=0.003; rho=0.56, p=0.015). No significant differences were revealed between spastic onset time predicted from kinematic data and EMG data. Significant correlations were found between Elbow flexor MAS and ΔV and εV (rho=0.49, p=0.03; rho=0.47, p=0.04), and between TS of elbow extensors and ΔNStr (rho=0.46, p=0.04). For the knee extensor muscles, the RI index was significantly correlated with the MAS (rho=–0.54, p=0.023) and with TS (rho=–0.65, p=0.006). Significant correlations of certain variables were demonstrated on repeat testing — ΔA and εA during stretch of elbow flexors (p=0.012, p=0.017) and εStr during stretch of elbow extensors (p=0.018) and RI during pendulum test (p=0.002). Conclusion: These findings provide preliminary information of aspects of validity and reliability of the BioTone system. The results showed that the BioTone measures have low to moderate concurrent validity, and low construct validity, whereas test-retest reliability was moderate for some of the variables. Further investigation of this device as a clinical tool to objectively measure spasticity in patients post-stroke is warranted. Impact of the study: To reduce functional, emotional, and financial burdens of a common aftermath of stroke — spasticity— a valid, reliable and user-friendly tool of objectively measuring its clinical presentation is needed. This study provides preliminary evidence to support further development of the BioTone system as a potential device to fill this void.