Effects of Hand Configuration on the Grasping, Holding, and Placement of an Instrumented Object in Patients With Hemiparesis

Abstract

Objective: Limitations with manual dexterity are an important problem for patients suffering from hemiparesis post stroke. Sensorimotor deficits, compensatory strategies and the use of alternative grasping configurations may influence the efficiency of prehensile motor behavior. The aim of the present study is to examine how different grasp configurations affect patient ability to regulate both grip forces and object orientation when lifting, holding and placing an object. Methods: Twelve stroke patients with mild to moderate hemiparesis were recruited. Each was required to lift, hold and replace an instrumented object. Four different grasp configurations were tested on both the hemiparetic and less affected arms. Load cells from each of the 6 faces of the instrumented object and an integrated inertial measurement unit were used to extract data regarding the timing of unloading/loading phases, regulation of grip forces, and object orientation throughout the task. Results: Grip forces were greatest when using a palmar-digital grasp and lowest when using a top grasp. The time delay between peak acceleration and maximum grip force was also greatest for palmar-digital grasp and lowest for the top grasp. Use of the hemiparetic arm was associated with increased duration of the unloading phase and greater difficulty with maintaining the vertical orientation of the object at the transitions to object lifting and object placement. The occurrence of touch and push errors at the onset of grasp varied according to both grasp configuration and use of the hemiparetic arm. Conclusion: Stroke patients exhibit impairments in the scale and temporal precision of grip force adjustments and reduced ability to maintain object orientation with various grasp configurations using the hemiparetic arm. Nonetheless, the timing and magnitude of grip force adjustments may be facilitated using a top grasp configuration. Conversely, whole hand prehension strategies compound difficulties with grip force scaling and inhibit the synchrony of grasp onset and object release.

Keywords: assessment; grasp; hand function; instrumented objects for rehabilitation; stroke.

Figure 1

Illustration of the iBox device and the experimental setup. (A) The iBox instrumented object. (B) Setup for the experimental procedure. Initial positions of the iBox and hand start area are indicated by the dotted lines. The gray shaded rectangle indicates the deposit area for the top grasp task.

Figure 2

Grasp configurations used during the iBox protocol. (A) Precision grip. (B) Top grasp. (C) Pinch grip. (D) Palmar-digital grasp. Image adapted from Martin-Brevet et al. (57).

Figure 3

Examples of recording of a lifting task carried out with the hemiparetic arm using the pinch grip in two patients with contrasting functional abilities (P1, FME 66 and P7 FME 37; see Table 1 for details). From top to bottom: (A1,2) angle measuring the deviation of the iBox from the vertical (B1,2) vertical acceleration of the iBox (C1,2) force signals: grasping force is indicated with plain (thumb) and dashed lines (digits), the unloading of the bottom face of the object is indicated with (dotted lines); inset in (C1) shows a larger scale. Vertical lines indicate the times of transitions between phases tg = onset of grip; tl = onset of lifting; ho = hold onset; he = hold end; tp = placement time; tr = release time. Time = 0 s at tg. In (C2), arrows indicate touch and push errors upon establishing and releasing grasp.

Figure 4

Grip forces for the hemiparetic (red symbols) and less affected arms (black symbols) for the different grasp configurations (in abscissa). (A) Grip force at the time of lifting (tl). (B) Maximum grip force during the lifting phase (C) Average force during the holding phase (D) Grip force at the time of release.*Dunn's post-hoc p < 0.05; **Dunn's post-hoc p < 0.01.

Figure 5

Temporal data for unloading and lifting phases in the hemiparetic (red symbols) and less affected arms (black symbols) using different grasp configurations (in abscissa). (A) Duration of the unloading phase. (B) Time difference between maximal grip force and peak acceleration during the lifting phase. (C) Rate of grip force change during the unloading phase. *Dunn's post-hoc p < 0.05.

Figure 6

Object orientation for the hemiparetic (red symbols) and less affected arms (black symbols) at: (A) Time of lift and, (B) Time of placement. *Dunn's post-hoc p < 0.05; ***Dunn's post-hoc p < 0.001.

Figure 7

Frequency of touch and push errors. (A) Frequency of touch and push errors made at grasp onset by the hemiparetic (red) and less affected (black) arms. (B) Same data distributed according to the different types of grasps used. (C) Frequency of touch and push errors made at grasp release by the hemiparetic (red) and less affected (black) arms. (D) Same data distributed according to the different types of grasps used. ***Chi-squared test p < 0.001.

Figure 8

Examples of individual differences during pinch grasp with hemiparetic (red) and less affected arms (black). (A) Grip force during holding. Each bar represents median grip force recorded for each patient. (B) Time delay from peak acceleration to maximum grip force. Each bar represents mean of time delay over three trials.

Figure 9

Correlation between clinical data and behavioral variables for the different grasp types. Lines represent significant Spearman correlations (positive in black, negative in red) between clinical measures and iBox variables. FAT, Frenchay arm test; FME, Fugl Meyer Evaluation; DGS, dynamometer grip strength; Touches on, frequency of touches before tg; GF, grip force at different time points; D, phase duration; Time lag, time difference between maximal grip force and peak acceleration during lifting; Alpha, deviation of the iBox from the vertical at the different time points; Alpha var, variability of alpha angle during holding.