Even if this would work for stroke, it won't do a damn bit of good since there IS NOTHING OUT THERE TO CURE SPASTICITY!
A portable system to measure knee extensor spasticity after spinal cord injury
Journal of NeuroEngineering and Rehabilitation volume 21, Article number: 50 (2024)
Abstract
Background
The pendulum test is a quantitative method used to assess knee extensor spasticity in humans with spinal cord injury (SCI). Yet, the clinical implementation of this method remains limited. The goal of our study was to develop an objective and portable system to assess knee extensor spasticity during the pendulum test using inertial measurement units (IMU).
Methods
Spasticity was quantified by measuring the first swing angle (FSA) using a 3-dimensional optical tracking system (with external markers over the iliotibial band, lateral knee epicondyle, and lateral malleolus) and two wireless IMUs (positioned over the iliotibial band and mid-part of the lower leg) as well as a clinical exam (Modified Ashworth Scale, MAS).
Results
Measurements were taken on separate days to assess test–retest reliability and device agreement in humans with and without SCI. We found no differences between FSA values obtained with the optical tracking system and the IMU-based system in control subjects and individuals with SCI. FSA values from the IMU-based system showed excellent agreement with the optical tracking system in individuals with SCI (ICC > 0.98) and good agreement in controls (ICC > 0.82), excellent test–retest reliability across days in SCI (ICC = 0.93) and good in controls (ICC = 0.87). Notably, FSA values measured by both systems showed a strong association with MAS scores (
~ −0.8) being decreased in individuals with SCI with higher MAS scores, reflecting the presence of spasticity.
Conclusions
These findings suggest that our new portable IMU-based system provides a robust and flexible alternative to a camera-based optical tracking system to quantify knee extensor spasticity following SCI.
Introduction
Spasticity is a common symptom present in a large number of individuals with spinal cord injury (SCI) [1, 2]. Despite having a considerable impact on independence and quality of life after SCI [3, 4], its quantification remains limited. Clinical exams, such as the Modified Ashworth Scale (MAS) [5] and the Tardieu scale [6], use nominal scales for the quantifications of spasticity and have limited validity and reliability [7,8,9,10,11].
Mechanical devices used to quantify resistance to a passive stretch at
controlled amplitudes and velocities need expensive and bulky equipment
and therefore are less suitable for routine use in clinical environments
[12]. Thus, there is a pressing need for developing objective and portable systems to measure spasticity [13,14,15, 2, 16].(I see measuring spasticity as completely useless until interventions that cure spasticity work!)
The goal of our study was to develop a system to assess knee extensor spasticity, which is commonly observed in individuals with SCI [1, 4]. At present, the pendulum test is a widely used biomechanical test for evaluating knee extensor spasticity using kinematic analysis [17]. The test quantifies the effect of a gravity-induced stretch of the knee extensor muscle on the leg kinematics and is performed with the participant sitting or supine with the legs hanging over the edge of a table. The operator first brings the leg to full extension and then suddenly releases it letting the limb swing under the action of gravity. A reduction of the first swing motion of the leg (first swing angle, FSA) has been associated with increased stretch reflex activity [18,19,20,21]. The pendulum test has been validated in controls [22] and has a high test–retest reliability and sensitivity to detect variations in spasticity in humans with SCI [20, 23,24,25], correlating with clinical scores [26,27,28]. Although, the pendulum test has been widely used alongside clinical scales barriers remain to implementing this exam in the clinic [13, 16, 29, 30]. Over the years, the pendulum test has been instrumented using video recordings [22], electrogoniometers [31, 32], gyroscopes [28], and accelerometers [33] making comparisons and standardization across outcomes difficult. Video recordings and systems based on optical markers are considered the gold standard for administering the pendulum test in laboratory environments but the need for markers to be visible at all times complicates physical examinations and measurements are sensitive to soft tissue artifacts and errors in markers positioning [34]. Electrogoniometers require positioning on two segments of a joint and are sensitive to improper alignment with the joint axes [35]. Gyroscopes can lead to overestimation of joint angles at higher angular speeds and accuracy degrades with time, while estimations from accelerometers are affected by measurement noise and integration drift [36]. Inertial measurements units (IMUs) have been extensively adopted as a reliable and inexpensive alternative to video recordings and systems based on optical markers for estimating lower limb kinematics [37,38,39,40,41]. We hypothesized that a portable system using two wireless IMUs would have good reliability in assessing knee extensor spasticity during the pendulum test as a 3-dimensional optical tracking system.
To address this question, we evaluated FSA values obtained with an optical tracking system and an IMU-based system in individuals with and without SCI on two different days. FSA values were compared with the MAS in individuals with SCI.
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