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School of Biological Sciences

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College of Sciences

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Center for the Study of Systems Biology

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Publication Search Results

Now showing 1 - 9 of 9

A Method of Prototype Evaluation for Assistive Mobility in Animals: Intervention for a Congenitally Malformed Dog – a Case Study

(Georgia Institute of Technology, 2007-04-25) Forest, Tiffany

Several studies report successful fittings of tripedal quadruped animals with prosthetic devices, but very few report fittings of bipedal quadrupeds. None of these studies report how the animals were trained to use their assistive devices or how the device was developed. The research focus of this project was to develop a method to train animals to use assistive devices and measure their mobility in order to determine the success or failure of prototype design. The overall goal of the assistive devices for a bilateral front limb deficient dog was to increase the animal’s mobility. After eight prototype designs over the course of 10 weeks, a design suitable for a timed up and go test was achieved. The test revealed an increase in mobility.
The Effect of Surface Curvature and a Gel Liner Interface on Performance Properties of the Tekscan Socket System

(Georgia Institute of Technology, 2007-04-25) Schrock, Lara

The presence of mechanical loads at the limb socket interface is considered an initiating cause of tissue breakdown and ulceration. Historically, prosthetists have relied on past experience, patient feedback, and indirect indications of load to gauge socket fit. The clinical measurement of interface pressures has the potential to provide quantitative, objective information to help in the evaluation of prosthetic fit. Tests of the Tekscan F-Socket system have been performed over flat and curved surfaces, but not using axial load and the presence of a gel liner to more closely simulate a clinical setting. This study investigates how drift and cyclic drift errors of the F-Socket system are affected by surface curvature and the presence of a gel liner interface. For drift, a known constant axial load was applied by a servo-hydraulic testing machine for 20 minutes. Samples were taken at 1, 5, 10, 15, and 20 minutes. For cyclic drift, load was alternated in a known range at 0.5Hz for 10 minutes. Samples were taken at 1, 5, and 10 minutes. These tests were performed under four conditions: flat rigid, flat with liner, round rigid, and round with liner. It was found that drift error was significantly affected by the curvature of the model, but not by the presence of a gel liner. It was also found that cyclic drift was not affected by the curvature of the model, but was by the presence of a gel liner. Further study should be done with other curvatures, other liners, and other sensor properties such as hysteresis and accuracy.
Upper Extremity Robotic Therapy for Individuals with Spinal Cord Injury

(Georgia Institute of Technology, 2007-04-25) Bui, Tina

Cervical injury causes tetraplegia in about half of spinal cord injury (SCI) cases and results in impaired hand function. Despite their different etiologies, both SCI and stroke subjects have demonstrated recovery by similar mechanisms of cortical reorganization. This suggests that interventions used after stroke may also be effective after SCI. With the current technology available, robotic devices are being used to provide safe and intensive rehabilitation to people with motor impairment after stroke. The main objective of this study is to assess the safety, comfort, ease of use, fit and therapeutic value of robotic therapy in a SCI clinic. This study investigates the hypothesis that a robotic device used to deliver elbow flexion and extension exercises will be accepted by the subject and lead to improved strength in the treated limb of SCI subjects.
Stiffness properties of prosthetic feet under cross-slope conditions

(Georgia Institute of Technology, 2007-04-18) Zeller, Sean

As an integral component after lower extremity amputation, prosthetic feet assist the body in forward progression, weight bearing stability and shock absorption. A Key element of weight bearing stability is the foot’s interaction with non-flat surfaces. Cross-slopes are encountered in daily activities from wheelchair ramps, to crossing uneven streets. Some prosthetic feet have been designed to accommodate such terrain. The objective of this study is to evaluate the stiffness of a representative sample of prosthetic feet when placed on a cross slope and use these results to discuss their potential as a classification tool. 15 prosthetic feet were acquired representing all available types of prosthetic feet. A servo-hydraulic testing machine was used for quasi-static loading of prosthetic feet under various conditions; Flat surface, medial slopes 7.5 deg., 15 deg., and lateral slopes 7.5 deg., 15 deg. Feet were cyclically loaded on two separate days to evaluate repeatability. 400 N was selected as a reference point for today’s discussion; it represents 50% of our hypothetical user’s body weight and coincides with the force applied to the foot during quiet standing. A one way ANOVA test was used in addition to correlation data to assess variance across two separate test dates. A significant difference was not noted between trial days. It was observed that for nearly all feet, the lateral border experienced greater changes in stiffness compared to the medial border when encountering a cross-slope. Feet showed a range of stiffness; at 400 N, the stiffness observed in the feet ranged from 54.6 N/mm to 236.2 N/mm. Feet also showed a significant range in the magnitude of change from stiffness on flat surfaces’ the change in stiffness ranged from 158 N/mm to 122 N/mm. While prosthetic feet designed and marketed to accommodate uneven terrain tended to have a significant reduction in stiffness compared to other feet, this did not necessarily produce a less overall stiffness. High variation was seen between feet of the same family in their interaction with cross-slopes. Laboratory tests can be used to classify prosthetic feet and clarify differences between feet. These results have implications for prosthetic foot prescription, reimbursement, research and development, although should be interpreted alongside clinical research to fully understand their implications.
The Capacity of the Prosthetic Profession to Provide Lower Extremity Prosthetic Limbs within the State of Georgia

(Georgia Institute of Technology, 2007-04-18) Curran, Andrew

Due to an aging population and a rise in conditions known to increase the risk of amputation, demand for prosthetic services is thought to be increasing nation wide. 20% of certified practitioners will reach retirement age within the next ten years. A recent National Commission on Orthotic and Prosthetic Education (NCOPE) study highlights the need to substantially increase the number of educational programs and the number of graduates becoming certified to meet the demand for services. The purpose of this study was to investigate the current capacity of the prosthetic profession in the state of Georgia to provide services. Palmetto GBA ,the Durable Medical Equipment Regional Carrier (DMERC) for Medicare Region C. was asked to identify the number of times the "Base" L-Codes for lower limb prostheses were submitted for billing in the years 2000 and 2004. Total sales was then estimated by extrapolating the Medicare information assuming Medicare sales represent 58% of total sales. The number of Georgia based American Board for Certification (ABC) and Board for Orthotist / Prosthetist Certification (BOC) certified prosthetists was solicited from their respective certifying agencies. The data collected represents the only estimate of lower limb prostheses fabricated in GA in 2000 and 2004. The data also represents the only estimate of prostheses fabricated per practitioner, and the only study to capture services rendered beyond Medicare beneficiaries.
Asymmetric Stability Margin of Postural Response to Perturbation in Unilateral Transtibial Amputees

(Georgia Institute of Technology, 2007-04-18) Tsai, Yi-Ying

Falling is an important clinical problem in amputee population. In unilateral transtibial amputees, increased postural sway in quiet standing and asymmetric EMG reactions in anticipatory postural adjustments to rapid arm raises have been done previously. The goal of this study is to quantify directional deficits in postural control in individuals with unilateral transtibial amputation. We used the concept of stability margin, which is the difference of peak center of pressure (COP) and center of mass (COM) displacement, to characterize direction stability in response to multiple directions of support-surface perturbations in the horizontal plane. METHODS: Three subjects with unilateral, traumatic, transtibial amputation and three able-bodied subjects as a control group were recruited. Subjects were instructed to stand quietly with their arms crossed on the perturbation platform and were presented with a randomized set of support surface perturbation in the horizontal plane. We collected five replicates of each of the 8 perturbation direction (0º, 45º, 90º, 135º, 180º, 225º, 270º, 315º). Kinematic, kinetic and EMG data were recorded. RESULTS: Surprisingly, the stability margin in anterioposterior and mediolateral directions in amputee group was not significantly different from controls. However, stability margin was significantly reduced in the diagonal directions when the amputated side was loaded (45° and 315° perturbations, p <0.05). CONCLUSIONS: Our results show that the stability margin in amputees is reduced in diagonal directions where the amputated side in loaded and the intact side is unloaded.
The Effect of Model Design, Cushion Construction, and Thin Pressure Mats on Pressure Measurement

(Georgia Institute of Technology, 2007-04-11) Pipkin, Leigh

Wheelchair cushions are designed to protect skin by reducing and distributing pressure. Pressure sensors and buttock models are used in standardized testing of wheelchair cushions. The purpose of this study was to explore how the presence of a thin pressure measurement mat, cushion construction, and buttock model design affect interface pressure (IP), envelopment, and immersion. Aspects reported here are the effect of model design on IP and envelopment and the interaction between model design and cushion construction. Testing was performed with two indenters and seven cushions. Conclusion: Wheelchair cushions deform in response to a loaded indenter. The result is a change in the shape of the indenter-cushion interface, which may not be consistent across loading trials. This is influenced by cushion stiffness and the unloaded shape of the cushion. The data suggests that model design influences the pressure redistribution properties of cushions. Therefore, development of standardized tests should consider the interaction between models and cushions.
Neuromechanical adaptations in joint stiffness when hopping with a SL-AFO

(Georgia Institute of Technology, 2007-04-11) Roiz, Ronald A.

Humans hopping on different elastic surfaces in series adjust leg stiffness to maintain system stiffness primarily by modulating ankle joint stiffness. When a parallel elastic element is applied at the ankle to assist plantar flexion, leg stiffness and total ankle joint stiffness is conserved. Moreover, biological ankle joint stiffness decreases to offset the added stiffness of the spring. We studied the effects of adding a resistive plantarflexion torque in parallel with the ankle. We hypothesized leg stiffness and total ankle joint stiffness would remain invariant and that biological ankle joint stiffness would increase to compensate. We ran a repeated measures study on 10 subjects hopping in place under three conditions: AFO (control), Plantarflexion Assist Spring-Loaded AFO (PA-SLAFO), and Plantarflexion Resist Spring-Loaded AFO (PR-SLAFO). We collected kinematic, kinetic, and EMG data at each condition for three frequencies. We analyzed statistics using a Three-Way ANOVA (subject, condition, frequency) with a Bonferroni Post-Hoc test. Different AFO conditions had no effect on leg stiffness. Total ankle joint stiffness was maintained for PA-SLAFO, with biological ankle joint stiffness decreasing to perfectly compensate. In the PR-SLAFO condition, total ankle joint stiffness was greater than expected. Biological ankle joint stiffness increased with PR SL-AFO, but was unable to completely compensate for the added resistance. This implies that despite adequate global compensation to maintain leg stiffness, subjects could not completely compensate for added resistive torque solely at the ankle and had to enlist a multi-joint compensation strategy. We are currently investigating these multi-joint compensation strategies.
Pedaling Asymmetry in Unilateral Transtibial Amputee Cyclists and the Effect of Prosthetic Foot Stiffness

(Georgia Institute of Technology, 2007-04-11) Childers, W. Lee

In addition to its rehabilitation potential, a prosthetic designed for cycling will enable amputees to have the benefits of cardiovascular exercise and participation in sports. A prosthetic design for cycling can be aided by an understanding of the forces involved. Amputees have significantly more pedaling asymmetry than the intact population. Factors creating pedaling asymmetry are: strength imbalance between limbs, difficulty in directing forces effectively with prosthesis, and sound side overcompensation at the top and bottom of the pedal stroke. The stiffness of the prosthetic foot was found to have no effect on asymmetry.