Abstract
BackgroundThe aim of this study is to investigate quantitative outcome measurements of hand motor performance for subjects after mild to moderate stroke using grip control tasks and characterize abnormal flexion synergy of upper extremities after stroke.MethodsA customized dynamometer with force sensors was used to measure grip force and calculate rotation torque during the sub-maximal grip control tasks. The paretic and nonpartic sides of eleven subjects after stroke and the dominant sides of ten healthy persons were tested. Their maximal voluntary grip force was measured and used to set sub-maximal grip control tasks at three different target force levels. Force control ability was characterized by the maximal grip force, mean force percentage, coefficient of variation (CV), target deviation ratio (TDR), and rotation torque ratio (RTR). The motor impairments of subjects after stroke were also evaluated using the Fugl-Meyer assessment for upper extremity (FMA-UE) and Wolf Motor Function Test (WMFT).ResultsMaximal grip force of the paretic side was significantly reduced as compared to the nonparetic side and the healthy group, while the difference of maximal grip force between the nonparetic side and the healthy group was not significant. TDR and RTR increased for all three groups with increasing target force level. There were significant differences of CV, TDR and RTR between the paretic side and the healthy group at all the force levels. CV, TDR and RTR showed significant negative correlations with FMA-UE and WMFT at 50% of maximum grip force.ConclusionsThis study designed a customized dynamometer together with an innovative measurement, RTR, to investigate the hand motor performance of subjects after mild to moderate stroke during force control tasks. And stroke-induced abnormal flexion synergy of wrist and finger muscles could be characterized by RTR. This study also identified a set of kinetic parameters which can be applied to quantitatively assess the hand motor function of subjects after mild to moderate stroke.
Highlights
The aim of this study is to investigate quantitative outcome measurements of hand motor performance for subjects after mild to moderate stroke using grip control tasks and characterize abnormal flexion synergy of upper extremities after stroke
Stroke survivors usually have a lower quality of life due to such functional limitations [3]
The subject selection criteria included: (1) hemiparesis resulting from a single unilateral lesion of the brain with onset at least one month prior to data collection; (2) able to generate voluntary contractions of the both hands; (3) moderate and mild stroke scoring more than 33 on FuglMeyer assessment for upper extremity (FMA-UE) [25]; (4) no visual, cognitive or attention defect which prevented following the experimental procedures as indicated by a score of 23 or more on the mini mental state examination (MMSE) [26]
Summary
The aim of this study is to investigate quantitative outcome measurements of hand motor performance for subjects after mild to moderate stroke using grip control tasks and characterize abnormal flexion synergy of upper extremities after stroke. Dynamic gripping movements [16,17,18] are commonly used to estimate upper extremity motor function after stroke. Power grip reflects force generating capacity, and is often tested before other grip control tasks are assessed. Previous studies stated that power grip force reflected the force generation capacity, and required careful control when sustaining force at a certain level [19,20,21]. Abnormal muscle synergies are often found in patients after stroke, which seriously influences motor function of paretic upper extremities [15,24], while flexion synergy of the upper extremity muscles has seldom been investigated
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