Altered digit force direction during pinch grip following stroke

Abstract

This study examined grip force development in individuals with hemiparesis following unilateral stroke. Eleven patients with chronic stroke with severe hand impairment and five age-matched neurologically intact subjects grasped an instrumented object between the index finger and thumb while fingertip forces, digit posture, and muscle electromyographic activity were recorded. We tested a range of different grip conditions with varying grip sizes, object stability, and grip force level. We found that fingertip force direction in the paretic digits deviated from the direction normal to the grip surface by more than twice as much as for asymptomatic digits. Additionally, the paretic thumb had, on average, 18% greater deviation of grip force direction than the paretic index finger. This large deviation of finger force direction for the paretic digits was consistently observed regardless of grip size, grip force level, and object stability. Due to the large deviation of the force direction from the normal direction, the paretic digits slipped and moved more than 1 cm during 55% of all grasping trials. A regression analysis suggests that this altered grip force direction was associated with altered hand muscle activation patterns, but not with the posture at which the digit made contact with the object. Therapies to redirect the force direction at the digits may improve stroke survivors' ability to stably grip an object.

Human hand modelling: kinematics, dynamics, applications

“…Valero-Cuevas provides a tool for measuring and quantifying anatomical structures which are crucial for grasp abilities of patients who have to undergo surgery (Valero-Cuevas and Laboratory 2000). Kamper is investigating human hands of healthy subjects and stroke patients for rehabilitation (Seo et al 2010). The ACT hand (Despande 2013) targets various issues, serving as a realistic model for surgeons to drypractice reconstructive surgery, but also to investigate neural control as well as for high-precision teleoperation and prosthetics.…”

Force requirements in topical medicine use—the squeezability factor

“…Rheumatoid arthritis, 8 osteoarthritis, 9 carpal tunnel disease 10 and stroke 11 have all been reported as having lower finger strengths. In addition to neurological disease causing lower strengths these can also cause deficits in control and direction of force application, 11 which are also required to co-ordinate functional tasks such as squeezing a bottle.…”

Diminished capacity to modulate motor activation patterns according to task contributes to thumb deficits following stroke

“…Deficits in voluntary thumb extension (Lang et al 2009), grasp timing and production (Nowak and Hermsdorfer 2003;Raghavan et al 2006a), thumb grasp-force direction (Seo et al 2010), and thumb individuation (Raghavan et al 2006b) have been reported, but the exact causes of these impairments remain unclear. A number of studies have examined impairment mechanisms in the fingers (Cruz et al 2005;Kamper and Rymer 2001), but the issues for the thumb may differ.…”