The extent of altered digit force direction correlates with clinical upper extremity impairment in chronic stroke survivors

Abstract

Many stroke survivors suffer from impaired hand function. Biomechanics of hand grip suggests that abnormally directed grip force can hamper gripping abilities and hand function. This study examined the relation between the ability to precisely direct fingertip force and clinical hand function scores among individuals affected by stroke. Specifically, clinical hand function tests of the Fugl-Meyer, Chedoke McMaster, and Box and Block Test were used, since they involve various hand movements required for activities of daily living. Digit force direction during static grip was recorded using multiaxial load cells. Data for 59 chronic stroke survivors were analyzed. We found that larger angular deviation of digit force from the normal direction was significantly associated with lower hand functional levels (p<.001 for all three clinical tests). Particularly, stroke survivors whose digit force deviated more than 21° from the normal direction could not achieve the normal level of Fugl-Meyer or Chedoke or move more than 4 blocks in a minute. The biomechanics of the way digit force direction affects hand grip function is described. In addition, underlying mechanisms for altered digit force direction post stroke are postulated, including impaired somatosensation and abnormal neural input to muscles. In summary, this study identifies a new biomechanical marker for hand functional level and recovery. Future interventions may focus on correcting digit force direction to improve hand functional outcome.

Wireless Isometric Force Sensor Platform for Bedside Automated Evaluation and Therapeutics of Orofacial and Hand Muscle Systems Across the Lifespan

“…A small database of orofacial and thumb-index force dynamics has also been collected in patients who have sustained unilateral middle cerebral artery infarcts resulting from ischemic stroke with promising results. Improved portability and operational ease of biomechanical assessment instruments will result in broader clinical use in patients with movement disorders [3,15,[17][18][19][20]. The inclusion of such biomechanical measures is expected to promote individualized treatment programs to support the rehabilitation of orofacial and hand-digit motor skills which are often impaired in neuromotor disease and injury.…”

“…A common visuomotor tracking paradigm, known as a ramp-and-hold isometric contraction task, is illustrated in this report and consists of a static target force level (e.g. 2 N) which the subject attempts to attain as rapidly and accurately as possible [3,[15][16][17]. The subject's force "ramps" from baseline to the target and then "holds" at the target until the end of the trial (typically 5 seconds).…”

Concomitant sensory stimulation during therapy to enhance hand functional recovery post stroke

“…The patient-centered outcome measures of the Stroke Impact Scale, perceived meaningfulness of the intervention [ 115 ], and usability feedback on TheraBracelet will also be obtained. Other outcome measures will include sensorimotor grip control and neural communication for hand grip, quantified as the digit force directional control [ 116 , 117 ] and EEG connectivity in the cortical sensorimotor network [ 118 ].…”

Wireless Sensing of Lower Lip and Thumb-Index Finger ‘Ramp-and-Hold’ Isometric Force Dynamics in a Small Cohort of Unilateral MCA Stroke: Discussion of Preliminary Findings

“…Ischemic brain lesions can adversely affect hand and digits during precision grip or pinch force stability, and movement accuracy during object manipulation and reach [11][12][13]. Following an infarct in the territory of the middle cerebral arteries (MCA) which feed the elaborated sensorimotor cortical representations of the hand and fingers, a loss of higher-order motor planning and sensorimotor integration greatly disrupts fine force production, particularly during individuation of the digits and strength.…”