title: 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.
authors.affiliation: Department of Industrial & Manufacturing Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI, USA; Department of Occupational Science and Technology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA; Department of Electrical Engineering and Computer Science, University of Wisconsin-Milwaukee, Milwaukee, WI, USA. Electronic address: najinseo@uwm.edu.
authors.forename: Na Jin
authors.initials: NJ
authors.lastname: Seo
authors.affiliation: Department of Industrial & Manufacturing Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI, USA.
authors.forename: Leah R
authors.initials: LR
authors.lastname: Enders
authors.affiliation: Department of Occupational Science and Technology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA.
authors.forename: Binal
authors.initials: B
authors.lastname: Motawar
authors.affiliation: Department of Kinesiology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA.
authors.forename: Marcella L
authors.initials: ML
authors.lastname: Kosmopoulos
authors.affiliation: Department of Industrial & Manufacturing Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI, USA.
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Fathi-Firoozabad
mesh_terms: D000203:Activities of Daily Living; D001696:Biomechanical Phenomena; D002908:Chronic Disease; D005260:Female; D005385:Fingers / Q000503:physiopathology*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D055595:Mechanical Phenomena; D008875:Middle Aged; D020521:Stroke / Q000503:physiopathology*; D017741:Survivors
keywords: Control; Digit; Direction; Finger; Hand grip; Rehabilitation; Stroke