A normative torque-profile approach for quantifying elbow and wrist flexor hyper-resistance after stroke: a proof-of-principle study
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Background
Post-stroke spasticity is commonly assessed using the Modified Ashworth Scale (MAS), despite its limited objectivity and variable reliability. This study introduces Score E , a novel isokinetic dynamometry-derived metric designed to quantify elbow and wrist flexor hyper-resistance by comparing patients’ torque-angle profiles with a healthy reference corridor.
Methods
Thirty-five post-stroke patients and twenty-one healthy controls were included. Elbow and wrist hyper-resistance was assessed using the MAS and an isokinetic dynamometer in two testing conditions: seated on the dynamometer chair (ergo chair) and seated in the patient’s wheelchair. Two dynamometer-derived metrics were analyzed: Score E and peak torque (Peakτ). Feasibility, inter-rater and test-retest reliability, and associations with MAS grades were assessed. Exploratory PRE-POST changes following a 10-min local vibration session were also described.
Results
Score E showed good to excellent inter-rater and test-retest reliability across joints and testing conditions. Inter-rater ICCs ranged from 0.81 to 0.89, and test-retest ICCs from 0.76 to 0.93. Peakτ showed moderate to good reliability. In contrast, MAS agreement was lower and more variable. Score E showed moderate associations with MAS grades, particularly at the elbow, with weaker and less consistent associations at the wrist. MAS assessment was faster, but all assessments were well tolerated, with median pain ratings of 0/10 in all testing conditions. PRE-POST vibration changes were small and heterogeneous, preventing formal assessment of responsiveness.
Conclusion
Score E provides a reliable, objective, and visually interpretable quantification of post-stroke elbow and wrist flexor hyper-resistance. By comparing the full torque-angle profile with normative data, this approach preserves information on both the magnitude and angular span of abnormal resistance, supporting its potential for targeted longitudinal monitoring.
