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1) The clinical need: There is dire need for effective means to promote the retention or restoration of dexterous manipulation with the fingertips in aging, and especially in aging with a disability. Holding and manipulating objects with the fingertips is essential to the activities of daily living. The retention and restoration of hand function in aging, injury, and disease is the subject of an entire medical field. Dexterous finger force tasks are ubiquitous in our daily life (e.g., writing, sorting coins, or buttoning a shirt) and differ greatly from static pinch tasks (e.g., holding a key or pressing a button) in that the magnitude and direction of fingertip forces need to be carefully controlled to fulfill the task. Dynamic manipulation with the fingertips, in particular, is a type of hand function that is essential to the activities of daily living. Dexterous manipulation with the fingertips is disproportionately impaired by orthopedic/neurological diseases and natural aging because it requires a complex balance and interactions among all neuro-musculo-skeletal elements of the body: from cortical and spinal sensorimotor systems, through musculotendon integrity, to joint and ligament flexibility and stability. From the engineering standpoint, the effectiveness of dexterous manipulation with the fingertips depends on restoring the ability of the brain-hand system to produce forces with both sufficient magnitude and directional control. If fingertip forces are too weak, the objects grasped may not be lifted; if the forces are not well directed, small and slippery objects will fall out of the grasp.
This complex balance and interactions make dexterous manipulation with the fingertips particularly vulnerable to orthopedic/neurological disease and the aging process. There is much interest and need in the study of impairment of dexterous manipulation with the fingertips in aging. In spite of these efforts, the legendary musculoskeletal complexity of the hand has delayed a rigorous understanding of how we produce dexterous manipulation with the fingertips, how to evaluate it, how to retain it in aging, and how to optimize its clinical rehabilitation.
The absence of objective and sensitive outcome measures of dexterous manipulation with the fingertips precludes informative clinical studies to optimize the choice and timing of treatment for each patient. Similarly, the lack engineering paradigms and technologies that focus on engaging dexterous manipulation with the fingertips robs clinicians of the ability to systematically promote the retention or restoration of dexterous manipulation in the clinic or at home.
2) The core technology: We have designed, patented and begun the development of a novel system to quantify the greatest dexterity a person can achieve at different levels of submaximal strength. The strength-dexterity (S-D) test is based on the principle of buckling of slender springs, and its current prototypes consists of asking a person to attempt to compress a variety of compression springs having different combinations of strength (stiffness) and dexterity (propensity to buckling) requirements. The S-D Test is a mechanically rigorous and informative measure of dynamic dexterous manipulation because it quantifies its functional cornerstone: the ability to simultaneously and dynamically regulate the magnitude and direction of fingertip force vectors.
3) The population to be served: Dexterous manipulation with the fingertips is degraded by the natural aging process, and practically every orthopedic (e.g., thumb osteoarthritis) and neurological (e.g., stroke, CP, Parkinson’s disease, traumatic brain injury, spinal cord injury) condition affecting the hand. This is because, as mentioned above, dexterous manipulation with the fingertips is disproportionately impaired by orthopedic/neurological diseases and natural aging because it requires a complex balance and interactions among all neuro-musculo-skeletal elements of the body. It is no overstatement that maintaining and restoring finger dexterity when aging with these target populations is a gateway to a productive and entertaining lifestyle: from feeding and dressing oneself to using a cell phone and computer.
4) The development and evaluation methods: Extend the S-D Test, via interactions with the sister projects in this proposal, into a clinically useful metric and rehabilitation strategy for dynamic multifinger dexterity:
Aim 1: Optimize and simplify current prototypes. We will miniaturize the sensors that are currently mounted on compression springs, as well as add accelerometers and streamline the analytical techniques to extract metrics of dynamical performance. A computer-controlled system will also be built to, on command, adopt different strength and dexterity levels. Digital signal processing of fingertip kinematics and sensors embedded in this spring will fully characterize dynamic neuro-musculo-skeletal function at each condition.
Aim 2: Validate the S-D Test against established measures of hand function. We will deploy the clinical versions of the S-D Test in control and clinical populations to test the following hypotheses:
Primary Hypothesis: The S-D Test correlates with available measures of hand function.
Secondary Hypothesis: The S-D Test predicts patient satisfaction after treatment for stroke better than available measures of hand function.
Aim 3: Extend the S-D Test into a home-use S-D System to promote the retention or improvement of dexterous manipulation via immersion technologies.
5) The expected outcomes. (a) An assessment tool that is both simple and expeditious to administer, and provides a comprehensive, reliable and quantifiable measure of dexterous manipulation with the fingertips. (b) A reliable and effective home-use system where clients improve or retain their dexterous manipulation abilities by using entertaining immersion environments.
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