How a diverse research ecosystem has generated new rehabilitation technologies: Review of NIDILRR's Rehabilitation Engineering Research Centers.

Over 50 million United States citizens (1 in 6 people in the US) have a developmental, acquired, or degenerative disability. The average US citizen can expect to live 20% of his or her life with a disability. Rehabilitation technologies play a major role in improving the quality of life for people with a disability, yet widespread and highly challenging needs remain. Within the US, a major effort aimed at the creation and evaluation of rehabilitation technology has been the Rehabilitation Engineering Research Centers (RERCs) sponsored by the National Institute on Disability, Independent Living, and Rehabilitation Research. As envisioned at their conception by a panel of the National Academy of Science in 1970, these centers were intended to take a "total approach to rehabilitation", combining medicine, engineering, and related science, to improve the quality of life of individuals with a disability. Here, we review the scope, achievements, and ongoing projects of an unbiased sample of 19 currently active or recently terminated RERCs. Specifically, for each center, we briefly explain the needs it targets, summarize key historical advances, identify emerging innovations, and consider future directions. Our assessment from this review is that the RERC program indeed involves a multidisciplinary approach, with 36 professional fields involved, although 70% of research and development staff are in engineering fields, 23% in clinical fields, and only 7% in basic science fields; significantly, 11% of the professional staff have a disability related to their research. We observe that the RERC program has substantially diversified the scope of its work since the 1970's, addressing more types of disabilities using more technologies, and, in particular, often now focusing on information technologies. RERC work also now often views users as integrated into an interdependent society through technologies that both people with and without disabilities co-use (such as the internet, wireless communication, and architecture). In addition, RERC research has evolved to view users as able at improving outcomes through learning, exercise, and plasticity (rather than being static), which can be optimally timed. We provide examples of rehabilitation technology innovation produced by the RERCs that illustrate this increasingly diversifying scope and evolving perspective. We conclude by discussing growth opportunities and possible future directions of the RERC program.

Effects of geometric joint constraints on the selection of final arm posture during reaching: a simulation study.

Significant debate exists regarding the neural strategies underlying the positioning and orienting of the hand during voluntary reaching movements of the human upper extremity. Some authors have suggested that positioning and orienting are controlled independently, while others have argued that a strong interdependence exists. In an effort to address this uncertainty, our study employed computer simulations to examine the impact of physiological limitations of joint rotation on the proposed independence of hand position and orientation. Specifically, we analyzed the effects of geometric constraints on final arm postures using a 7 degree-of-freedom model of the human arm. For 20 different hand configurations within the attainable workspace, we computed sets of achievable joint angles by applying inverse kinematics. From each set, we then calculated the locus of possible elbow positions for the particular final hand posture. When the joints were allowed 360 degrees of rotation, the loci formed complete circles; however, when joint ranges were limited to physiological values, the extent of the loci decreased to an average arc angle of 54.6 degrees (+/-27.9 degrees). Imposition of joint limits also led to practically linear relationships between joint angles within a solution set. These theoretical results suggest a requirement for coordinated interaction between control of the joints associated with hand position and those involved with hand orientation in order to ensure attainable joint trajectories. Furthermore, it is conceivable that some of the correlations observed between joint angles in the course of natural reaching movements result from geometric constraints.

Estimation of muscle forces about the wrist joint during isometric tasks using an EMG coefficient method.

A technique for estimating isometric muscle forces based on EMGs and anatomical parameters is presented. In the present study, we record EMGs from five muscles acting at the wrist, during a series of isometric contractions in flexion, extension, ulnar deviation and radial deviation. The method then uses these EMG signals and the necessary anatomical data to estimate individual muscle forces. For one subject, complete anatomical parameters were estimated by MRI reconstruction of muscle moment arms and lines of muscle action. In all subjects, the errors associated with variability in the EMG signals were reduced through the use of signal processing techniques and intensive subject training. These EMG-based force estimates were then validated by evaluations at torque directions in which no mechanical redundancy existed. The stability of the solution space was examined using Monte Carlo simulations. The results of our study show that individual muscle forces at the wrist can be estimated with considerable accuracy, without assuming any control strategy (as is done with optimization theories). However, due to the limited mechanical redundancy of the wrist, it is uncertain whether the method can be used to estimate muscle forces in more highly redundant systems.