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Objectives: The sense of balance declines with age, resulting in impaired mobility and increased risk of falls. We are developing an instrument that is clinically useful for quantifying hitherto qualitative measures of balance, for feedback during therapy and home care, and for preventing injurious falls - a balance orthosis for fall-prone elderly individuals.
Clinical Relevance: As veterans age, they become increasingly at risk for injurious falls; hence the need for a balance orthosis to help maintain independence. If therapist time with each patient is limited, the motion analysis system can act as a surrogate therapist, monitoring a patient's performance and compliance with a course of therapy. Local clinical collaborators have used the method for diagnosis of veterans with peripheral neuropathy, and non-local researchers have studied fatigue in walking by the elderly and standing balance in a variety of subjects, including children with cerebral palsy. A number of clinicians are interested in real-time analysis of Parkinson's disease patients' acceleration patterns so as to generate cues to promote successful activities of daily living. Other collaborators are measuring effects of yoga training on balance, and combined head- and eye-tracking for vestibular research.
Methods: We have designed and built several versions of a computerized wearable accelerometric motion analysis system (WAMAS) consisting of two small 3-axis sensors attached to both corners of eyeglass frames to measure head motion, and two sensors above each hip on a belt at the waist, along with a self-contained data acquisition package. A remote control is used to command the wearable unit, so the wearer is unencumbered by cables.
Results / Conclusions: This paper presents brief summaries of four project components: 1. Reliability & Validity of Accelerometric Gait & Balance Diagnosis - We are establishing statistical reliability and validity by comparison of accelerometry with laboratory gait and balance measures (force platform, joint angle goniometry and video imaging) of elderly subjects having well-defined mobility status, using a test-retest protocol. A total of 84 subjects have been tested at least twice. 2. Analysis of Head & Waist Motion During Falls From a Tilting Platform - In preliminary studies to prevent fractures from falling onto the hip, we examined forward, backward and lateral falls by 12 young able-bodied subjects standing on a platform held level by an electromagnet until released at a random time. Falls in any direction were identifiable, and lateral falls could be distinguished from backward falls by greater horizontal acceleration at either left or right sensor site. 3. Pressure & Motion Feedback to Prevent Skin Breakdown in the Sensorimotor Impaired - We are testing the hypothesis that a wearable motion and pressure sensing system will help prevent skin breakdown. This system will wirelessly interact with skin interface pressure sensors, provide real-time visual, tactile and/or auditory feedback to the user, communicate patient status to a remote clinician, and recognize that it is unused or incorrectly used if a patient is not complying with a therapeutic pressure-relief regimen. 4. Multi-Link Human Body Motion Simulator - Since it is difficult for a human to exactly reproduce a motion trajectory, we plan to test accelerometers using a multi-link model having joints equipped with angle encoders and magnetic brakes; motive power is provided by a 6-axis robot arm. The model permits tests with sensors correctly oriented or misaligned, and with simulated soft tissue interposed between sensors and linkage.
Acknowledgments: VA Rehabilitation R&D pilot project E972-PA, Merit Review projects E601-RA, -2RA, -3RA, design/development project E2182-DA; Maven Technologies donation to PAIRE #SAB0025; PAIRE "flex- fund" grant for student support #SAB0020.