Hello! This presentation will discuss the Wearable Wireless Auditory Feedback System developed for Gait Rehabilitation by the BioInstrumentation Lab at the University of Utah
There are many people living with lower-limb amputations, and the majority of these develop an asymmetric walking pattern. This has social consequences, appearing as a limp, which may be troublesome to the person with the amputation. There are also important medical consequences such as increased metabolic costs, which is especially pertinent to those who have lost a limb due to diabetic complications, as well as increased incidence of knee osteoarthritis in the intact limb. Asymmetry can be evaluated by dividing the stance time on the affected limb by the stance time on the normal limb to determine the stance time ratio.
We have created a lower extremity auditory feedback system called “LEAFS”. LEAFS is a pair of insoles that are inserted into a patient’s shoes allowing force data to be recorded. Each insole is embedded with 10 force-sensing resistors (or FSRs), 9 of which are recorded (depending on the characteristics of the users foot). A 1x2x3 inch box is attached to the ankle containing circuitry for transmitting the data to a computer. The system collects all force data at over 100Hz from each foot and runs continuously for over 10hrs on one AA battery, and the system costs under $250 per pair of insoles.
A laptop computer receives the wireless data, which is analyzed using a matlab GUI. The GUI calculates initial contact and final contact in real-time, to determine the stance time symmetry ratio. The parameters are modified as necessary by the physical therapist during training.
We have studied one subject with a trans-tibial amputation on the left side. The subject received six sessions of 30 minutes of auditory feedback training, using “negative feedback” where the system emitted a loud beep if the stance time symmetry ratio was below the threshold set by the physical therapist. This slide shows data from the middle of the subject’s third training session. Each block of data represents 1 minute of training (the subject rested after each block), and the ratios throughout each block are shown in blue. The red lines indicate the thresholds, and the black lines indicate the means and standard deviations. This data suggests the importance of choosing a reasonable threshold when using negative feedback, although the results are not statistically significant. In A , the threshold is too high, and the minor adjustments made by the subject do not result in improvement. In B and C , the threshold is within an attainable range, and the mean symmetry increases as the subject works to improve her gait.
This slide shows the data from the subject’s sixth and final training session. Although the results again are not statistically significant, the first half of the steps shown show overall improvement, while the second half of the steps generally plateau. This suggests that there may be a daily motor learning limit that we need to explore further.
We are currently conducting a prospective study of 10 subjects using positive feedback. Future work will include biomechanical modeling of the muscular changes in persons with asymmetric gait and the use of force asymmetry feedback. We would like to acknowledge our sponsors for supporting this research, and thank you for your time.
A Wearable Wireless Auditory Feedback System for Gait Rehabilitation Linfang Yang Philip S Dyer K Bo Foreman Stacy J Morris Bamberg BioInstrumentation Lab
Motivation <ul><li>Lower-limb amputations </li></ul><ul><ul><li>Prevalence: 1.6 million persons with lower-limb amputations </li></ul></ul><ul><ul><li>Incidence: 156,000 individuals in the USA lose a limb, and about half have a lower-limb amputation </li></ul></ul><ul><li>Many develop an asymmetric walking pattern </li></ul><ul><ul><li>Social consequence: altered appearance of walking </li></ul></ul><ul><ul><li>Medical consequences: increased metabolic costs, increased incidence of knee osteoarthritis </li></ul></ul><ul><ul><li>Stance time ratio can be used to evaluate asymmetry </li></ul></ul><ul><ul><ul><li>Stance time ratio is the stance time of the affected limb divided by that of the normal limb </li></ul></ul></ul><ul><ul><ul><li>Healthy adults have a typical stance time ratio of 1.02±0.02 </li></ul></ul></ul>
Lower Extremity Auditory Feedback System (LEAFS) <ul><li>Software interface: </li></ul><ul><ul><li>MATLAB® GUI </li></ul></ul><ul><ul><li>Modified by the physical therapist during training </li></ul></ul><ul><ul><li>Calculates initial contact and final contact in real time </li></ul></ul>
Current and Future work <ul><li>Prospective study of 10 subjects using positive feedback </li></ul><ul><ul><li>Pre-test, post-test, +6 week post-test in motion lab </li></ul></ul><ul><li>Biomechanical modeling of muscular changes </li></ul><ul><li>Force asymmetry feedback for improving adherence to weight-bearing regimens </li></ul>Acknowledgements <ul><li>NSF IGERT in Biocentric Robotics, </li></ul><ul><li>University of Utah: CMMR Grant, TCP Grant </li></ul>