Design of a Portable Position, Velocity, and Resistance Meter (PVRM) for Convenient Clinical Evaluation of Spasticity or Rigidity

Abstract

Spasticity is a common consequence of the upper motor neuron syndrome and usually associated with brain lesion, stroke, cerebral palsy, spinal cord injury, and etc. On the other hand, rigidity is a neuromuscular disorder often found in Parkinson’s disease patients. Both of spasticity and rigidity are characterized by abnormal hypertonic muscle behaviors that will cause discomfort and hinder daily activities. Worldwide, the estimated affected population of spasticity is around 12 million [1], and rigidity affects more than 10 million people [2]. Clinical evaluation of spasticity or rigidity involves personal assessment using qualitative scales, such as the Modified Ashworth Scale (MAS) or Modified Tardieu Scale (MTS) for spasticity and Unified Parkinson’s Disease Rating Scale (UPDRS) for rigidity. However, this evaluation method heavily relies on the rater’s personal experience/interpretation and usually results in poor consistency and low reliability. The goal of this design was to develop a quantitative measurement device that can be used to assist clinical evaluation of spasticity or rigidity. This portable device, the Position, Velocity, and Resistance Meter (PVRM), can be strapped around a patient’s limb to measure angular position, angular velocity and muscle resistance of a given joint while the patient’s limb is passively stretched by the clinician. Acquiring this quantitative data from patients will not only allow clinicians to make more reliable assessments but also help researchers gain additional insights into the quantification of spasticity and rigidity.

Modeling, Control, and Clinical Validation of an Upper-limb Medical Education Task Trainer for Elbow Spasticity and Rigidity Assessment

“…"#$%& will approach to the desired value of 𝜏 '() , which was set to be 66 °/s [17]. To extract 𝜏 '() for each UPDRS score, we initially referred to the clinical data from [22] in the design phase [17] and the magnitudes of 𝜏 '() were further iterated during a clinical validation study with a group of 11 experienced clinicians [23]. Since gravity assists the stretch motion in extension, but resists it in flexion, the values were adjusted to be higher for extension to partially offset the effect of gravity ( 𝜏 '() = 1.2, 2.0, 2.6 Nm for flexion and 𝜏 '() = 2.0, 2.5, 3.2 Nm for extension for UPDRS 1 to 3, respectively).…”

“…𝜃 ! "#!$ and H was extracted from two clinical datasets [22], [24]. Q, 𝜃 %&' , and 𝑘 ()*# were tuned by clinicians.…”

“…For each MAS level, Park et al identified the spasticity parameters based on clinical data collected from four child spasticity subjects. However, due to the relatively small sample size and their age, we estimated spasticity parameters from two clinical studies datasets of adults collected by our research group [22], [24]. In parallel, two experienced clinicians (both with 20+ years of experience) were invited and asked to perform extension trials at their preferred speed to provide expert tuning on SP parameters for each MAS score.…”

Estimating Relative Angles Using Two Inertial Measurement Units Without Magnetometers

“…Thus, two IMUs can be used to measure the relative joint angle between two adjacent body segments by placing the IMUs on the body segments. This approach can be used for computing joint kinematics in biomechanical (e.g., knee flexion/extension angle during slow gait) [1], [2], [4], [7] and clinical applications (e.g., quantifying elbow joint kinematics during a clinical assessment of abnormal muscle behavior) [5], [6].…”

Validation of a Wearable Position, Velocity, and Resistance Meter for Assessing Spasticity and Rigidity

“…The PVRM measures angular position (θ), angular velocity ( ), and muscle resistance (τ) of a given joint while the patient's limb is passively stretched by a clinician. We previously presented the design of the PVRM [12], which consisted of a moving module (placed on the user's wrist), main module (placed on the user's upper arm), two EMG sensors (placed over the biceps and triceps) and a reference EMG electrode (placed over the olecranon) ( Fig 1). The two modules each contained an inertial measurement unit (IMU) (MPU9250, InvenSense; San Jose, CA), for measuring θ and ω, and the moving module also contained an inline load cell (LCM202, OMEGA Engineering; Norwalk, CT) to measure the applied load on the wrist.…”