Assessment in the title immediately tells me this does nothing to get survivors recovered! I'd fire anyone doing 'assessment' research!
Development of a quantitative assessment for abnormal flexor synergy index in patients with stroke: a validity and responsiveness study
Journal of NeuroEngineering and Rehabilitation volume 21, Article number: 229 (2024)
Abstract
Background
Arm-lifting movements (shoulder flexion) are essential for upper extremity rehabilitation after a stroke. Abnormal flexor synergy (elbow flexion) is frequently observed during shoulder flexion, impeding functional improvement. However, no quantitative method exists for assessing abnormal flexor synergy. This study investigated the validity and responsiveness of a newly developed index to quantitatively evaluate abnormal flexor synergy.
Methods
Participants included 103 patients (mean age: 58.0 ± 10.1 years; 64 men, 39 women) with stroke. Using three-dimensional coordinate data during shoulder flexion obtained from a depth sensor camera, we calculated the abnormal flexor synergy based on our developed index. The abnormal flexor synergy index decreases with increasing flexion of the elbow joint during shoulder flexion (the maximum value is 100% without abnormal flexor synergy). The validity of the abnormal flexor synergy index was assessed by analyzing the correlation between the index and both the Fugl–Meyer Assessment of the Upper Extremity (FMA-UE) four-category scores and the Modified Ashworth Scale (MAS) scores for elbow, wrist, and finger flexors, using Pearson’s and Spearman’s correlation coefficients. Responsiveness was studied in 17 inpatients (mean age: 59.5 ± 8.1 years; 7 men, 10 women) who underwent proximal upper extremity intervention for approximately 3 weeks, evaluating change from admission to discharge using the standardized response mean (SRM).
Results
Significant correlations were observed between the abnormal flexor synergy index and FMA-UE scores: A (r = 0.625, p < 0.001), B (r = 0.433, p < 0.001), C (r = 0.418, p < 0.001), and D (r = 0.411, p < 0.001), as well as MAS scores for elbow flexors (r = -0.283, p = 0.004) and proximal interphalangeal flexors (r = -0.201, p = 0.042). The highest responsiveness was observed in the FMA-UE A score (SRM = 0.81), followed by the abnormal flexor synergy index (SRM = 0.79).
Conclusions
The newly developed index for assessing abnormal flexor synergy demonstrated superior validity and high responsiveness. These results suggest the potential for using this index to evaluate upper extremity function in patients with stroke.
Background
Stroke is a leading cause of physical disability [1, 2], with upper extremity dysfunction being a primary symptom affecting approximately 70% of patients with stroke [3, 4]. This dysfunction adversely affects daily activities [5] and diminishes health-related quality of life [6]. Stroke survivors often report that the loss of upper extremity function is one of the most distressing long-term outcomes [7]. Consequently, improving upper extremity function is important for stroke survivors and their caregivers.
Rehabilitation of the upper extremity post-stroke requires using the paralyzed limb for training and daily tasks, with functional improvement dependent on the amount of use [8]. Arm-lifting movements (shoulder flexion) are essential for positioning and orienting the hand in the environment [9]. However, after a stroke, pathological co-activation or reciprocal inhibitory changes arise due to central lesions impairing the corticospinal tracts [10]. Specifically, during voluntary single joint movements, excessive and unintended motion occurs in adjacent joints [11, 12]. This stroke-specific abnormal movement is referred to as abnormal synergy. Two main synergies have been identified in the post-stroke upper limb: the flexor synergy, in which shoulder, elbow, and wrist flexion are obligatorily linked, and the opposite extensor synergies [13, 14]. The most common abnormal flexor synergy is elbow flexion during shoulder flexion [15, 16], which is the leading cause of reaching dysfunction [17, 18]. Moreover, this abnormal flexor synergy can lead to long-term issues such as reduced joint mobility and pain, fostering a learned non-use pattern that limits improvement potential in the hemiplegic upper extremity [19]. Therefore, abnormal flexor synergy should be assessed appropriately to safely and effectively rehabilitate the hemiplegic upper extremities.
However, no established method exists for the quantitative assessment of abnormal flexor synergy. The Fugl–Meyer Assessment of the Upper Extremity (FMA-UE), considered the gold standard for evaluating upper extremity motor paralysis, is commonly used to assess abnormal synergistic movements [20], although it is not quantitative. Recently, various quantitative assessment methods for abnormal synergy in the hemiplegic upper limb have emerged. Previous studies have quantified abnormal synergy using different methods. Some used robotic devices to measure elbow torque and stiffness to assess motor impairments, such as spasticity and joint viscoelasticity [21, 22]. Others utilized electromyography to assess abnormal synergy, revealing impaired coordinated movement and muscle activity patterns during upper limb work impairment and dysfunction [23,24,25]. Further, three-dimensional movement analysis has been used to investigate joint inflexibility and joint connectivity changes [26]. However, these methods typically do not specifically target flexor synergy during shoulder flexion. Furthermore, these methods require extensive preparation, measurement, and analysis time, making them less practical for clinical settings. To eliminate these issues, we developed a specific quantitative assessment method for abnormal flexor synergy during shoulder flexion, which has not been extensively explored in stroke rehabilitation. Moreover, to enhance the clinical feasibility of our study, we used markerless motion capture technology, reducing the complexity and time required for traditional assessments. This offers a more practical and efficient method for routine clinical use. We hypothesized that the developed index would adequately assess abnormal flexor synergy. This study aimed to investigate the validity and responsiveness of a newly developed quantitative assessment method for abnormal flexor synergy in patients with stroke.
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