This report originally appeared in the September 2009 issue of DOTmed Business News

Modern technology has greatly advanced the manufacturing and usefulness of prosthetics. Researchers and inventors are designing prosthetics that closely mimic natural joints and limbs. Even though there have been substantial strides made in the field, the improvements are still significant year after year.

With prosthetics more lifelike than ever, individuals fitted for them are more willing to accept them; because what can be done with a prosthetic arm, leg, knee, hip, finger or eye could never be done before.

What makes this possible is the research and inventions from great minds working independently or for research institutions, hospitals, companies and government agencies with the main purpose of creating prosthetic applications for virtually every part of the human body.




Over the past five to ten years, by far the greatest advancement in the field of prosthetics has been the use of microprocessor technology to operate the major joints of the prosthesis (knees, hands and elbows). These days, it is not uncommon for a prosthetic component to require a laptop computer for programming the device to the wearer's needs. Nor is it uncommon for a user to have to plug-in their prosthesis at night so that an internal battery can charge while they sleep.

"Microprocessor technology provides a more sophisticated means of prosthetics operation and allows wearers to achieve better function, mobility and confidence," says Mark Maguire, CPO Clinical Director, Advanced Prosthetics Center, LLC, Omaha, NE.

Maguire says that the terms "bionics" or "robotics," have not been widely accepted within the prosthetic industry, instead, "we typically use the term microprocessor technology". This terminology indicates that the prosthesis has a computer processor on board, similar to a personal computer, that reads inputs from sensors and then calculates adjustments to the prosthesis to accommodate the wearer's activities. The Advanced Prosthetics Center has a unique business model in which the company utilizes the latest in both prosthetic technology and fitting techniques and places a strong emphasis on specialized physical therapy. "We have learned that it is more difficult for a patient to benefit from advanced technology until they receive physical therapy from a gait and mobility specialist," says Maguire.

Ohio Willow Wood Fusion Foot

Advanced Prosthetics recently integrated the Ohio Willow Wood OMEGA Tracer CAD-CAM system. The system features a one-of-a-kind "Alpha Design Liner" program. The new imaging system is more accurate than traditional plaster impression techniques and simplifies the initial process of prosthetic fabrication. It allows the company to capture a digital image of the limb, and manipulate the model as a 3-D image on a computer screen.




Most prosthetic feet are designed to provide specific characteristics, like vertical shock or inversion and eversion, but few prosthetic feet actually provide several characteristics in one package. Ohio Willow Wood has broken the mold with the development of their Fusion Foot, a prosthetic foot which provides a spectrum of key traits for maximum user comfort and performance. The Fusion Foot's design allows the carbon fiber shank, heel and foot plate to work together through each step rather than independently, as is the case with traditional designs.

Bob Arbogast, Ohio Willow Wood's president, says, "Our thrust of new product development is to create products that improve the functionality and quality of life for amputees. Our research and development team studied the top-selling prosthetic feet to identify the core characteristics clinicians and amputees want in a prosthetic foot. Our team then designed a foot that delivers several of those core characteristics such as inversion/eversion, smooth heel-to-toe transition, and vertical shock absorption, rather than only one or two."

"While there are many other feet available on the market that provide multi-axial articulation and shock absorption, some are bulky, heavy and expensive," said Jim Colvin, Ohio Willow Wood's director of engineering. "It was our goal to develop a prosthetic foot that featured multi-axial articulation and shock absorption in a lightweight, compact, customizable and affordable design. Clinical and laboratory results have shown that we were able to achieve this goal with our unique carbon composite and bumper design. Key elements of the patent pending design are the toe and heel bumper assemblies, which suspend the carbon composite foot shank above the foot plate, allowing for controlled articulation and shock absorption of the foot shank and a very natural gait."

X-System - Finger Device

The X-System is a series of stainless steel components that can be assembled into several hundred configurations of artificial hands.

"When I first started this project, I developed a single finger device, which I called the X-Finger," said Daniel Dean Didrick, Inventor and Designer, Didrick Medical Inc., Naples, FL. Each X-Finger is comprised of several components that are fastened together. Each component is attached to its corresponding components, creating a reciprocally and transversely interconnected configuration of parts when complete. This crisscross pattern of parts resembles X-s repeating; thereby, receiving the name X-Finger.

Didrick then went on to develop a series of components that can be assembled to stabilize from one to ten fingers depending on the user's needs.

Whether someone is missing one finger or all ten fingers, an assembly can be created to accommodate their needs. "What makes the configurations of parts unique is that when applied, the user is able to control the movement of each replaced finger by simply moving their remnant finger," said Didrick. "If an entire finger is missing, an opposing finger is able to control the device's movement. If all of the fingers are missing the replaced digits can be connected to the palm. In these cases the movement of the palm in relation to the wrist controls the flexion and extension movements of each replaced finger."

Because there are no expensive electronics, the devices can be produced in mass quantity at a low cost. This will allow individuals from any economic background to benefit from the advancement. "Many of us have seen robot-like fingers moving on prosthetic hands. However, these devices were only available when someone had lost their entire hand," said Didrick. There are many robotic prosthetic hands and arms available, but finger amputees had no functional prosthetic options available to them. When someone lost one through ten fingers, the only prosthetic option was to wear a silicone, non-bending glove that resembles the appearance of the prior hand. These gloves or finger covers do not restore function, but rather mask the condition from others. While masking the condition may be a benefit offering an aesthetic gain, the X-System offers what the prosthetic industry terms active-function.

Didrick Medical Inc. was contracted by the United States Department of Defense to develop the X-Thumb to complement the company's other devices. Today, every major insurance carrier in the U.S. has approved Didrick's devices for their patients. For the past several years, he has been developing this technology to help a variety of patients. Now, the company is shifting gears and moving into mass-production enabling a larger patient body to use them. The X-Finger has been showcased in numerous museums including the United States Patent and Trademark Museum.

SynTouch Technology

Gerald E. Loeb, M.D., Professor of Biomedical Engineering, University of Southern California and Chief Executive Officer, SynTouch, LCC, is head of a research team at USC that has developed a mechatronic fingertip that provides a sense of touch similar to that of a human fingertip. It employs novel "biomimetic" design principles to achieve robustness, as well as high-sensitivity and dynamic range. The technology is being developed by a spin-off company, SynTouch LCC, for a wide range of applications, including, in addition to prosthetic hands, industrial robots and fruit-harvesting machines.

Syntouch recently received Small Business Innovative Research (SBIR) grants from the United States National Institutes of Health, National Science Foundation and Department of Agriculture.

Dr. Loeb noted that Syntouch is working only on the sensors themselves and their integration into the control of prosthetic and robotic hands. "We are working with various industrial partners who build the mechatronic hands and arms."

The DigiTAC fingertip has a rigid core, elastic skin and even a fingernail, similar to a human finger. The skin is inflated with a small amount of conductive fluid. Electrodes distributed over the surface of the core detect changes in electrical resistance resulting from distortions of the skin upon contact with objects and surfaces. A pressure sensor inside the core detects micro vibrations in the skin and fluid associated with slip over surfaces. A thermistor detects the temperature and heat flows associated with contacting objects made of various materials. All signal processing is done by electronic circuitry molded into the rigid core, where it is protected from the hostile environments in which hands are often used. The skin is molded from silicone rubber and is easily replaced when worn or damaged.

Dr. Loeb explained, "The next challenge is to integrate this sensory information with the commands from the operator. In some cases, this will require "haptic displays" that recreate the sensations of touch as now employed in advanced virtual reality systems. In other situations, the tactile information will be used automatically to adjust the grip, similar to the reflexes upon which humans rely to prevent slip." Eventually, it should be possible for autonomous robots to identify and handle common tools and objects. At present, robots can handle objects only if they are well known and marked with visual identifiers of highly engineered attachment points.

DARPA

Defense Advanced Research Projects Agency (DARPA) is part of the Federal Government that falls under the Department of Defense. The DARPA prosthetics program is an ambitious effort to provide the most advanced medical and rehabilitative technologies for military personnel injured in the line of duty. DARPA is currently working on two different upper extremity prosethetic devices. Their research team has recently developed a prosthetic arm that is undergoing trials with the Department of Veterans Affairs. (See CBS 60 Minutes coverage at www.cbsnews.com/video/watch/?id=5318065n.




The Johns Hopkins University Applied Physics Laboratory is working with DARPA, developing a different arm, which will be the first fully integrated prosthetic arm that can be controlled naturally, provide sensory feedback and allow for eight degrees of freedom - a level of control far beyond the current state of the art for prosthetic. (Each degree of freedom represents an independent field of motion such as up/down, left/right, forward/back, etc.)

A spokesman for DARPA indicated that while there are many details left to coordinate, "participants in the Revolutionizing Prosthetics program along with several others throughout the prosthetics community appear to be working toward a major event early next year to detail successes in prosthetics across the board, as well major advancements in prosthetic arms resulting from clinical and home trials from a DARPA/Veterans Affairs collaborative effort."

This is certainly a situation where the lines blur between science and medicine to the advantage of everyone.