Predictive value of the pendulum test for assessing knee extensor spasticity

Abstract

BackgroundThe pendulum test is commonly used to quantify knee extensor spasticity, but it is currently unknown to what extent common pendulum test metrics can detect spasticity in patients with neurological injury or disease, and if the presence of flexor spasticity influences the test outcomes.MethodsA retrospective analysis was conducted on 131 knees, from 93 patients, across four different patient cohorts. Clinical data included Modified Ashworth Scale (MAS) scores for knee extensors and flexors, and years since diagnosis. BioTone™ measures included extensor strength, passive and active range of motion, and pendulum tests of most affected or both knees. Pendulum test metrics included the relaxation index (RI), 1st flexion amplitude (F1amp) and plateau angle (Plat), where RI=F1amp/Plat. Two-way ANOVA tests were used to determine if pendulum test metrics were influenced by the degree of knee flexor spasticity graded by the MAS, and ANCOVA was used to test for confounding effects of age, years since injury, strength and range of motion (ROM). In order to identify the best pendulum test metrics, Receiver Operator Characteristic analysis and logistic regression (LR) analysis were used to classify knees by spasticity status (none or any) and severity (low/moderate or high/severe).ResultsPendulum test metrics for knee extensors were not influenced by degree of flexor spasticity, age, years since injury, strength or ROM of the limb. RI, F1amp and Plat were > 70% accurate in classifying knees by presence of clinical spasticity (from the MAS), but were less accurate (< 70%) for grading spasticity level. The best classification accuracy was obtained using F1amp and Plat independently in the model rather than using RI alone.ConclusionsWe conclude that the pendulum test has good predictive value for detecting the presence of extensor spasticity, independent of the existence of flexor spasticity. However, the ability to grade spasticity level as measured by MAS using the RI and/or F1amp may be limited. Further study is warranted to explore if the pendulum test is suitable for quantifying more severe spasticity.

Residual descending motor pathways influence spasticity after spinal cord injury

“…21 In our study, MAS and pendulum test scores were negatively correlated, supporting the view that the pendulum test has good predictive value for detecting the presence of extensor spasticity detected by the MAS. 32 These clinical findings together support the existence of 2 subgroups among participants with motor complete SCI: those without spasticity and those with marked spasticity. The lack of a relationship between the degree of spasticity and time postinjury, level of injury, and intake of spasticity medication suggests that other factors contributed to our results.…”

Objective Assessment of Spasticity by Pendulum Test: A Systematic Review on Methods of Implementation and Outcome Measures

“…This systematic review aimed at analyzing the state of the art in implementation of Pendulum test and the outcome measures of this method of evaluation of spasticity. This test is agreed to be repeatable and a valid method of identifying presence of spasticity [27,39], though it may not be successful in discriminating between close levels of spasticity [49]. Since lower leg weight is suitable to create enough speed through free fall in the pendulum test, which is crucial for this speed dependent symptom, most of this test's applications is on the knee joint.…”

“…Since the method of assessment of spasticity through pendulum test, and the processing steps to reach to the outcome measures are fully dependent on the implemented technology, this aspect is separately assessed in the literature. As Table 3 shows, variety of technologies, from ultrasound sensors [36] to camera-based [27,50]or ber-optic goniometers [49], have been used in the devices that implemented the test. However, some of these technologies are used more frequently whose advantages and disadvantages are compared in Table 4.…”

“…Table 6 is the list of the main studies on the outcome measures of pendulum test that is used in this review. [49] In the literature of the pendulum test for spasticity, there is no standard agreement between the researchers particularly in de nition of the outcome measures. One main reason for this ambiguity is the different references used for measuring the knee angle.…”

“…The second most popular frame of reference for angular movement is rest angle or the nal position of the knee in the pendulum test [27,33,35,36,43,50]. Some of the researchers have used the initial angle of the shank as their reference instead of horizontal plane [39,45,49]. No researcher has used vertical plane as their reference in knee angle measurement.…”