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O & P Technology: Soaring into the New Millennium

December 31, 1999

By Judith Otto
Reprinted with permission - O & P Business News
The world is full of wonder and delight—and if you doubt that, you need only to step into the realm of O & P research and development, where you'll see mind-boggling marvels of science and bioengineering—futuristic, other-worldly—yet only a breath away from commonplace reality and everyday use.

The speed at which progress is being made is breathtaking and seems to be gaining momentum. Sophisticated computers are nearly as common as TV sets in the average American household; the Internet puts a whole world full of information at our fingertips—what was impossible only yesterday is now easily within our grasp.

The speed at which progress is being made is breathtaking and seems to be gaining momentum. Sophisticated computers are nearly as common as TV sets in the average American household; the Internet puts a whole world full of information at our fingertips—what was impossible only yesterday is now easily within our grasp.

Is it any wonder if our outlooks are jaded, and we're not easily impressed by the latest new "miracles" of technology?

But somehow, in the world of O & P, the futuristic technology of the new millennium still has the power to genuinely awe us with its ability to empower and enable the physically challenged, restoring independence and self-confidence in an ever-increasing variety of innovative and imaginative new ways.

Lower Limb Advances

On the face of it, it seems an unlikely partnership—prosthetic researchers and nuclear weapons technicians. But as Morton Lieberman, Ph.D., of the Department of Energy's Sandia National Laboratories in New Mexico explains it, it was the perfect resolution to several problems at once.

With the cold war officially over and the weapons race ended, what was to become of all those unemployed Russian nuclear weapons experts? Fearful lest they peddle their formidable expertise at producing atomic weapons to unfriendly third world countries, the DOE crafted a plan that benefited the U.S. commercially, served the very real needs of prosthetic patients, and kept the bomb builders off the streets and out of trouble.

By serendipitous coincidence, the workers in a weapons lab must demonstrate expertise in the same fields that prosthetic designers study: mechanical design; mechanical testing; stress analysis; developing durability; smart systems; microprocessor controls/sensors.

Under the DOE's Initiatives for Proliferation Prevention Program and in collaboration with NIH's National Center for Medical Rehabilitation Research, funding to develop the Rolling Joint Prosthetic Foot and Ankle for commercial sale was awarded to Sandia, which partnered with the inventor, Mark Pitkin of the Tufts School of Medicine; Ohio Willow Wood, to whom the product is licensed; and Chelyabinsk-70, a facility in one of Russia's closed cities where product development was undertaken.

The successful project resulted in a new product for Ohio Willow Wood, says Lieberman. Russian experience and ingenuity in creating the needed spring mechanism and their willingness to pursue testing in their own country, using a Russian prosthetist and Russian medical personnel, may yield more advanced products.

"Relations are good, but communications are difficult," Lieberman reports, "the result not so much of a language barrier as a cultural barrier, with different approaches to bureaucracy, export licenses, etc."

Despite the difficulties, the collaboration was a historically documented success. So successful was the venture that other joint projects are being undertaken: notably an advanced electronic knee, a stumble-resistant knee and a variable geometry socket.

The Russian Nuclear Center now houses the world's largest research center on lower limb prosthetics, where more than 77 people are currently employed. Lieberman, who identifies himself modestly as "a chemist, not a prosthetist," has clearly made the quantum leap to full comprehension and appreciation of the value of a nonexplosive product, explaining knowledgeably how the Rolling Foot simulates the natural movement of a human foot through better dorsiflexion.

He discusses, too, the goals for the current Stumble-Avoidance Knee project, identifying the need to increase functional outcomes, create more choices for how it can be used, decrease maintenance requirements, and lower costs—all while the Sandia Lab pursues their own solution to the same problem Russian technicians have been working on concurrently.

Lieberman points with justifiable pride to this epic success story which has turned swords into plowshares; yet (the temptation is irresistible!) I can't help but observe that our former arms race with the Russians has now become a foot race...one where everybody wins.

What's Next?

Lots of people are working on a better knee—one that will be much lighter, one that can control stumbling as a result of catching your toe on the curb or similar accident, says Robert C. Dean, Jr., ScD. from MIT and founder and President of Synergy Innovations, Lebanon, Pennsylvania. Within about five years, there should be some good electro-mechanical knees on the market," he predicts.

Among the difficulties: "The industry is very fragmented, with 15 different knee manufacturers. All of them say they do research and development, but it is not high-tech stuff."

The other need Sandia noted was for a better cosmesis. "They have excellent simulations now," Dean observes, "but they're very fragile. Bump into a chair and they tear. A good above-knee cosmesis costs from $2,000 to $3,000 and only lasts a year, if you're careful," he warns.

Bringing down costs will be an important influence in the next few years, Dean predicts. "A modern above-knee costs around $16,000; a below-knee prosthesis can cost from $6,000 to $8,000. Most of the cost is in the prosthetist's time, trying to make the socket fit comfortably and properly. Sometimes he or she has to make four or five check sockets and just has to hope that their variable will cover it."

Also on Dean's prediction list is a powered ankle. "Sixty per cent of forward propulsion comes from the calf muscle, as you push off with your toes. Amputees don't have that capability. Even energy-storing feet don't make a difference—except to athletes."

The powered ankle Dean is working on wasn't possible in the past, he explains, when power supplies were too heavy. "Now batteries are getting much more efficient, lighter weight, more compact. Soon they'll be at one-tenth the weight of today's batteries."

Meanwhile, Dean is considering an alternate power source—a combustion engine being developed for battle use by the government. Smaller than a beer can, you can wear it on your belt, Dean claims. "It's fueled by 'whiskey'—the only fuel source you can carry on a plane," Dean explains.

Construction materials for O & P use have come nearly as far as they can, he believes. "There's not much room left for improvement, with such dramatic strides as we have already made recently with space age materials and titanium—the stuff fighter planes are made of."

Dean foresees a trend toward what he calls "the K-Mart leg," which allows the amputee to choose the components the prosthetist will put together with a socket that already automatically fits—no costly and time-intensive hand crafting or customizing is needed. The prosthetist's professional tasks will consist of giving advice, assembly, alignment, training, and long-term service.

Within the next ten or 15 years, a major and welcome change Dean sees is in the price. "Cost and utility will both be greatly improved," he predicts.

The Variable Geometry Socket

Robert C. Dean, Jr., Sc.D. from MIT and founder and President of Synergy Innovations, a Lebanon, New Hampshire-based company, remembers the conclusions of the 1995 Conference on Lower Limb Prostheses that the National Institutes of Health hosted with Sandia National Laboratory.

"They determined that there were three important needs that should be addressed in the development of lower limb prostheses: a better knee, a better socket, and better cosmesis," Dean recalls.

Dean, a transfemoral amputee since 1942, speaks from personal experience when he describes the need for the better socket his company is working on with support from the National Science Foundation/Small Business Innovations Research (NSF/SBIR) and the NIH/SBIR.

In addition to the socket, Synergy Innovations is dedicated to prevention of and rehabilitation from trauma; to developing products, processes, and materials for aiding the physically challenged; for biomedical, biotechnology and diagnostic instruments; and for working with difficult materials and advanced materials fabrication.

His variable geometry socket is designed to answer the needs of most patients who complain that sockets simply don't fit—they hurt. "The Veterans Administration has been pushing improvements, but nothing has really helped, according to their report," Dean notes. "The CNC carvers don't really make a difference," he says. "A stump or residual limb changes volume daily and monthly, too, if you're a woman. Dialysis, sickness—a lot of things—can affect tissue volume, and make a difference in volume of 6% to 7% in above-knee amputees."

This is particularly significant in the light of his assertion that amputees can detect a volume change of a little as 1%. With a change as comparatively dramatic as 6%, the fit is so adversely affected that it is possible to actually lose the leg, if you use a suction socket, as most TFAs do, says Dean.

Dean's variable geometry socket solves the problem by "automatically fitting the stump without the patient doing anything—it's activated by walking on it," Dean explained. "The average prosthetist can fit it on a patient in his shop today with existing tools he has on hand," Dean claims.

The socket will soon progress into extensive clinical trials under NIH support and should be on the market within the next three to four years, he believes.

Sensitve Skin

Vladimir Lumelsky, Ph.D., Professor at the University of Wisconsin and Cochair of the National Science Foundation/Defense Advanced Research Projects Agency (NSF/DARPA) Sensitive Skin Workshop held in October 1999, points out that their development is in the preliminary stages. The purpose of the workshop was to determine needs and direction and develop principles for future work in the area, he explains.

If your goal is to develop "a sensing skin-like device that houses, on a bendable and stretchable skin substrate, millions of sensors " where do you begin? If your intention is that "A machine or a human wearing such skin will receive detailed information about surrounding objects..." what type of sensor do you choose to collect such information—visual, audio, pressure-sensitive? And how fast must it relay that information?

"If you put your finger on a hot stove and it takes your nervous system two seconds to respond and remove your finger, it's too long," says Lumelsky. Similarly, if this reactive skin is wrapped on a prosthetic arm, "a faster, almost instantaneous reaction is desirable to prevent further damage to your singed prosthetic investment.

"Necessary speeds have been achieved already," says Lumelsky. "So for biomedical applications, speed is no longer a research issue." The workshop did not address the type of sensors (tactile, proximity, force, heat, etc.) that would be built into the skin. Once a generic architecture for the skin is figured out, Lumelsky says, it will be easy to build in specific sensor modalities. The choice of sensors is thus relatively insignificant in the overall scheme of things. "They may even add infrared capability to allow you to sense items at ten to 15 inches away in pitch darkness, like a bat's radar," he adds. "More difficult issues are massive electronics embedded in large patches of skin, the skin substrate, and related signal processing." A simpler prototype was demonstrated at the workshop, one that could be applied to prostheses today. "It works in principle," says Lumelsky, "but it lacks certain properties and certainly is not ready for mass production.

"Another problem for biomedical applications is the human interface. The difficulty lies in getting information from the skin sensors to the brain and back to the muscle to create a reflexive response," he explains.

This is not unlike research issues encountered in working with the artificial eye retina, Lumelsky points out, where researchers are trying to get information from the retina to the vision nerve and to the brain. "People ARE working on this," Lumelsky says, "but it's not an easy problem to solve." The prototype "skin" is made of a plastic Dupont polymer called Kapton, and although Kapton bends, it lacks the ability to stretch, Lumelsky reports. Needed resilience may perhaps be obtained by replacing Kapton with silicon polymers, says Lumelsky.

"Besides, compared to this prototype," he says, "the skin envisioned by the workshop participants will have a much higher density of sensors."

At the moment, components necessary for progress in this area—the proper electronics, skin materials, necessary signal processing techniques—are beyond the state of the art," Lumelsky observes. "But workshop participants indicated that first versions of the skin could be obtained fairly fast. The purpose of meetings such as this sensitive skin workshop is to try to create a road map of research that would include payoffs both in the short term and in the long run."

The workshop determined that some products of this research had the potential for being commercialized very soon.

Extraordinary Orthotics

The same technological developments that have enabled prosthetic science to make such exciting strides—and to plan even more dramatic progress in the future—have birthed thrilling possibilities in the field of orthotics as well.

Jacqueline Wertsch, M.D., a rehabilitation physician at the Medical College of Wisconsin, speaks with energy and conviction when discussing orthotic directions for the future.

"We can look forward to constant improvement in the materials used to fabricate orthoses, certainly—and also to the increasing use of sensors that create 'smart' orthoses that are more than just reactive in nature and design.

"Even the perception of what orthotics are can change dramatically and very quickly," she predicts.

Orthotics have traditionally served as substitutes for physical deficiencies and lost function, Wertsch points out, but now the orthotic interface between a human body and its environment is providing more than just a brace. Orthoses are on the brink of providing their wearers with strength and capabilities far beyond normal human limitations, Wertsch claims.

"They're not just replacing lost function; they're dramatically exceeding normal human function," she explains.

A pedorthic specialist, Wertsch is intrigued by the potential of sensors and is doing research based on their use in the insoles of her patients' shoes.

"The sensors allow us to record what goes on underfoot with every step, all day long. An incredible amount of invaluable information can be derived from sensor use," she notes, "and can be used in a variety of possible ways, including outcomes measurement."

Measurement of pressure readings could assist in telling pedorthists which rocker sole shoe is best for each different diabetic patient. Feedback from the diabetic's on-board insole sensors array can also alert him/her to potential problems from a minor foot injury and correct matters before the situation worsens.

Sensors are also capable of detecting minute temperature changes inside the footwear, which might be an early warning of ulceration or infection.

Shoes that measure foot pressure can likewise be used to provide immediate feedback to the wearer or his/her rehab "coach." More complete and detailed feedback from a runner or elite athlete can be input to others to help them learn and duplicate successful patterns.

Conceivably, the sensory input from the feet can be even greater and more valuable in terms of sending such feedback directly up to the knee brace, with instructions to "tighten up," as appropriate.

Sensor science is growing hugely in the orthotic field, says Wertsch, but in most cases, fine tuning needs to be applied. All the above possibilities are theoretically possible now, since the technology exists to do them, Wertsch points out—but "the problem is setting aside the time it takes to finalize research and implement the necessary testing," she explains, "as well as in pulling together a qualified and talented team to tackle the project.

"Researchers are already creating micro-machines that could function inside human cells," she continues, "but we are just touching the surface of how to develop health-care related applications utilizing the micro-machines' impressive capabilities as an invaluable diagnostic tool," she cautions.

Michael Mueller, Ph.D., P.T., an Associate Professor at the Washington University School of Medicine in St. Louis, has been involved in similar sensory feedback work, focusing on the needs of diabetic subjects.

"Technology is advancing so quickly in both software and hardware, that more and more potential orthotic applications continue to present themselves," says Mueller.

His sensory research plan provides feedback to his subjects in the form of "very concrete directions." His research group plans to use a simple and understandable signal, such as an LCD device that flashes a signal or commands at a specified point—perhaps when their feet have exceeded allowable stress limits, and they need to stop walking. Or perhaps the warning flashes to alert subjects who haven't walked enough, reminding them to increase their activity.

The commands on the device might also remind subjects not to take long strides or push off as hard, Mueller amplifies, depending on the particular subject's special needs.

Mueller's study has just completed its first two-year phase; hardware and software are in place, he says, and the means to analyze results. The limiting factor is the relative fragility of the sensors, which tend to break down quickly in the "hostile environment" inside a shoe, where they are subjected to extremes of temperature and pressure.

"Such a study is not as easy in practice as it sounds in theory," Mueller points out wryly.

Other exciting areas where new orthotic ground is being pioneered include the creation of virtual pedorthic models based on mathematical input, CAT scan data, and pressure readings from the sole of the foot. Models for knee and hip orthoses could also be created in the same way, but the first applications will be tested using the foot area.

Mueller's project, working with radiologists and engineers, has reached the stage where they are verifying the anatomical accuracy of the virtual models. He anticipates completion of this stage of research within the next two years.

Paul Bach-y-Rita, M.D., pursues his research at the Center for Neuroscience and Department of Rehabilitation Medicine at the University of Wisconsin-Madison Medical School.

The implications of Bach-y-Rita's multiple studies in sensory substitution are astonishingly far-reaching. He explores the potential applications of sensory substitution systems for functions such as sex sensation, sensation from feet, and sensation from robotic hands. He also examines aspects of the neural mechanisms of recovery following spinal cord injuries.

As Bach-y-Rita points out, "Spinal cord patients not only can't move but can't feel. Therefore, any motorized orthosis would not be useful unless it also included sensory feedback from the device."

Potential future studies may well include a motorized external artificial arm in the form of an exoskeleton surrounding the nonfunctional human arm, he notes.

Studies in the sensory substitution area appear more complex, due to the unfamiliar nature of the concept to most readers. As Bach-y-Rita explains it, the brain is where all perception takes place. The brain processes sensory input from tactile, temperature, auditory and taste cells and interprets them as familiar and recognizable images. The brain can learn to interpret virtually any such sensory stimulus, which is where the concept of sensory substitution enters the picture.

Since sensory stimuli reach the brain in the form of patterns of pulses that arrive along the nerves—whether they come from the retina, the fingertips, the tongue, or elsewhere in the body—in theory (and now in practice), the brain could learn to reinterpret those pulses as visual, auditory, or tactile, messages or images.

Bach-y-Rita reminds us that a blind person with a cane doesn't "feel" with the hand; he/she feels what the cane contacts when that tentative sensory impression is conveyed to the brain for recognition, using the hand as a simple relay station.

Since Bach-y-Rita has determined that the human tongue is extraordinarily sensitive to tactile stimuli as well as taste and requires only 3% of the level of electrical stimulus needed to achieve the same results from our fingertips, his studies utilize the tongue as a superefficient relay station for his tactile vision substitution system (TVSS).

The system uses optical images picked up by a TV camera and transduces them into a form of energy that can be mediated by the skin (or tongue) receptors. The visual information reaches the perceptual levels for analysis and interpretation via somatosensory pathways and structures, Bach-y-Rita explains. In addition, the oral cavity affords convenient space to accommodate orthodontic retainers containing the FM receiver, electrotactile display, microelectrics package, and the battery.

After training with the TVSS, blind subjects reported experiencing the images in space, instead of on the skin.

Even with low-level TVSS systems at work, studies with fingertip "vision" have been successful, allowing blind subjects to perform complex perception and "eye"-hand coordination tasks such as facial recognition and accurate judgment of speed and direction of a rolling ball.

"The goal," says Bach-y-Rita, "is to develop man-machine interface systems that are practical and cosmetically acceptable."

He notes that in related studies, "Persons who had lost hand sensation due to leprosy have been able, with the use of an instrumented glove with the sensory information delivered to a sensate area (the forehead), to 'feel' objects that they touched. This is relevant to the development of robotic hands for persons with high quadriplegia, as well as to the development of gloves for astronauts. Sensors were placed in the fingertips of the gloves in order to compensate for the loss of tactile sensation that causes a decrease in manual performance."

Similarly, Bach-y-Rita says, sensor-loaded insoles for diabetics, such as Dr. Wertsch's study described above, could lead to a system allowing sensory information from the feet to be delivered to a tongue display for persons with low level paraplegia. "Such information would be helpful in ambulation on uneven terrain, and could also signal weight shifts."

Bach-y-Rita's studies in the area of sensory orthoses emphasize not only improved capabilities for the physically challenged, but improved quality of life through restored enjoyment of sensation as well. His colleagues note that Bach-y-Rita's 30 years of research in this area have made him a potential Nobel Prize candidate.

We've Come a Long Way

Dudley Childress, Ph.D. and Professor of Biomedical Engineering at Northwestern University, surveys O & P technology from a different perspective, judging the whole and the sum of its parts rather than its individual products—then turning his focus to the future.

"We've come a long way," Childress reflects, "and we will advance still further. This is the time for us to start looking at improving the communications interface between prostheses and humans and to consider how we might alter the types of interfaces we're using."

One option he suggests is surgical alteration, e.g., the transfer of toes to an arm when the hand is lost.

Or perhaps using the arm muscle in a tunnel cineplasty. He defines this as bringing muscle forces outside of the body. New surgical and engineering techniques make this possible.

Another option involves developing a direct skeletal attachment, so the prosthesis is attached to the bone for stability, and forces are transferred to the bone instead of the muscle.

New surgical techniques also have advanced to allow these things to happen, Childress says. "We're maybe ten years away from accepted use of these procedures—it takes a while for change to evolve in any field."

He believes best practice unites surgical, prosthetics, and engineering skills.

It's an age of wonder—an age of miracles. Every age has had its prophets and pioneers—those who believed that what one man could dream, others could do. Every generation has its visionaries—from Leonardo da Vinci to Jules Verne to today's Superheroes of Silicon Valley. We can be proud that our own field of O & P imagineers takes a back seat to none. What will they think of next? We'll know tomorrow, and I can hardly wait.

Editor's Note: Watch for more information on advances in upper-extremity prosthetic technology in our next issue.

Judith Otto is a freelance writer based in Holly Springs, Mississippi. She is also a copywriter and Project Coordinator for Strategic Marketing, Memphis, Tennessee, a firm which specializes in marketing communications for the O & P field.

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