Studying Human Locomotion of Amputees Using Prostheses with NI Multisim

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"In the past, College Park Industries would have needed an entire department to design the iPecs. Multisim and Ultiboard gave the company access to a level of technology that was not previously available to small enterprises."

- MaryAnn Labant, College Park Industries

The Challenge:
Creating a portable, wearable device to conduct gait analysis and study human locomotion of amputees using prostheses.

The Solution:
Using NI Multisim and Ultiboard software to design the Intelligent Prosthetic Endoskeletal Component System (iPecs).

Author(s):
MaryAnn Labant - College Park Industries
Michael Leydet - College Park Industries

A leader in the prosthetic industry, College Park Industries provides the most anatomically correct prosthetic feet available. The company uses biomechanical design principles to mimic the human foot and has focused, for decades, on incorporating high-tech composite materials into its products to enhance function and durability.

Over the years, the R&D emphasis at College Park Industries has expanded from a focus on dynamic mechanical products that react to the body during human locomotion to a focus on “intelligent” embedded microelectronic systems. Microelectronic systems can function as stand-alone monitoring devices or can be incorporated into active, “bionic” prosthetic foot and ankle systems.

Industry Trends and Challenges

One of the challenges in the prosthetic industry is designing products that meet the functional needs of the amputee as well as the profitability needs of the prosthetist, the practitioner who prescribes, manufactures, and fits the final device. Prosthetists get paid for their services by private and public insurance organizations. Lately, the insurance industry is trending toward evidence-based practice, for which the industry uses a combination of scientific research and clinical judgment to justify prosthetic prescriptions and subsequent reimbursement.

Evidence-based practice is not currently widespread, partly due to the fact that only a few hundred gait analysis laboratories exist worldwide that have the capabilities to perform biomechanical testing on amputees. These multimillion dollar facilities are typically housed at universities such as the Prosthetics Research Laboratory and Rehabilitation Engineering Research Program at Northwestern University. Furthermore, gait analysis is expensive, and because of the dispersed geographic locations of these laboratories, it is largely unavailable to the general prosthetic practitioner.

The design challenge at College Park Industries was to provide a portable device that could offer the critical data acquisition functions of a gait analysis laboratory and that amputees could wear while performing normal daily activities or while being fitted for their prostheses. The device needed to be unobtrusive to the wearer in terms of weight and size to eliminate any biasing effect on the test results.

The iPecs

The College Park Industries iPecs is a measurement tool designed to support researchers and clinicians in their optimization of patient care. Specifically, the iPecs provides personalized, objective information on the effects of prosthetic component selection and alignment. With it, any prosthetist (not just researchers in a gait analysis laboratory) is able to not only visualize but also directly measure and interpret the effects of prosthetic component selection and alignment. In effect, it allows measurement and documentation of much of what the amputee is feeling – forces and moments transmitted from the floor through the prostheses to their residual limbs. The goal is to improve prosthesis selection and alignment and, ultimately, provide a positive contribution to amputees’ overall health and well-being.

The iPecs, a virtual “miniature gait lab” that is incorporated into the prosthesis that the amputee uses, is designed to provide real-time feedback relative to three force and three moment magnitudes and directions transmitted from the ground surface to the distal socket of a below knee amputee. It is an investigational tool that offers objective measurements designed to supplement or even replace some aspects of gait analysis. Although some real-world functional prosthetic component testing equipment currently exists, it is not designed for biomechanical applications. Techniques and tools such as the iPecs (which measures impact transients, residual-limb torque, forces, and activity) are needed to more comprehensively evaluate prosthetic functions in a real-world setting.

The iPecs, universally adaptable with standard mounting components used in a prosthetic limb, is designed to collect data and transmit it wirelessly, without interfering with the normal function of the prosthesis. This freedom from constraints provides a more accurate picture of how the prosthesis user functions in normal daily activities. This level of information is not currently available, but it is critical to improve the prosthetic industry’s understanding of the interactions between the amputee and the prosthesis.

Development Tools

College Park chose NI Multisim and Ultiboard software to design the iPecs circuitry in order to take advantage of the cross compatibility of the two packages. By using the two packages in concert, the R&D team could work through the initial design and simulation of the circuit board, all the way to the final layout. The team used these dynamic tools to design, simulate, and visualize the circuitry through multiple iterations. This resulted in a major size reduction of the device and increased package-size efficiency.

In the past, College Park Industries would have needed an entire department to design the iPecs. Multisim and Ultiboard gave the company access to a level of technology that was not previously available to small enterprises. The products have a good price capability ratio and are backed by NI electronic design and software customer support.

The R&D team is currently evaluating software to be used for top-level GUI design. The design of this GUI will be a challenge, as the iPecs must effectively display mechanical information (forces, moments, and position data) in a way that is intuitive to clinicians who are more familiar with anatomic terminology than engineering terms. Human and prosthesis interfaces must be illustrated as well as the effects of adjustments to the prostheses and how the adjustments affect the human-prosthesis interfaces. The R&D team is considering NI LabVIEW software for this task.

Preliminary presentation of the iPecs to the orthotic and prosthetic industry sparked a large amount of interest. Several gait analysis laboratories contacted College Park Industries to learn more about participation in field-testing efforts. The iPecs began beta testing in late 2008.

Author Information:
MaryAnn Labant
College Park Industries
17505 Helro Dr.
Fraser, MI 48026
Tel: (586) 354-2524
mlabant@college-park.com

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