Biomedical Engineering Reference
In-Depth Information
also be compact, safe when used by the patient alone, “plug and play” on a
personal computer, simple to use, adaptable to the user, and relatively inexpensive
for patients or rehabilitation centers to buy or rent.
This chapter gives an overview of the challenges of robot-assisted rehabili-
tation of hand function after stroke. Two robotic devices we have designed for
rehabilitation of hand function, the HapticKnob and the HandCARE, are then
presented, and strategies for hand rehabilitation using such devices are discussed.
Finally, the principal findings of clinical studies with the two systems are presented
to illustrate the potential and future challenges of robot-assisted rehabilitation of
hand function after stroke.
4.2 HAND FUNCTION AFTER STROKE
The hand is a fascinating neuromechanical system and a defining characteristic
of humans. The ability to position the thumb in opposition to the other fingers
in order to grasp objects is a unique characteristic of the human species, which is
believed to have played a decisive role in our evolution.
Precision grip
, employed
where fine motion and force are required, and
power grip
, employed to generate
high force, provide the basis for almost all prehensile tasks used in ADL, such
as eating, manipulating tools or enabling communication with each other, for
example through gestures and writing. In addition to its motor function, the
human hand acts as a sensory organ during tactile exploration of the environment,
which is possible because of the high density of cutaneous sensory receptors in
the fingertips. Tactile sensation is capable of replacing vision when this sense is
impaired or unreliable. The hand is central to human psychology, as it is used in
executive, perceptual and expressive activities (Valero-Cuevas (2009)).
Because of its direct control by the motor cortex, the hand is usually impaired
after a stroke. Different dysfunctions such as muscle weakness, spasticity and
compulsory co-activation of anatomical muscles at multiple joints contribute to
impairment of finger and hand function after stroke (Fugl-Meyer
et al.
(1975)).
Extension, abduction, and adduction of the fingers are particularly impaired,
leaving the fingers in a flexed finger posture (Hunter and Crome (2002)).
In terms of function, damage to the sensorimotor system leads to specific
impairments of the hand that include (i) limited ability to open the hand or position
the thumb in opposition to the other fingers, which is the basis for all types of
grasp (Kamper
et al.
(2006), Cruz
et al.
(2005), Dovat
et al.
(2007)), (ii) loss of finger
independence, limiting the ability to move and generate force independently with
individual fingers (Lang and Schieber (2004), Raghavan
et al.
(2006), Schieber
et al.
(2009)) and (iii) inability to control finger force and explore the environment,
due to insufficient tactile sensation and impaired sensorimotor translation. These
impairments result in difficulties in grasping and manipulating objects, leading to
slow and uncoordinated movements.
