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As the readers of this column ponder their day-to-day challenges relating to the rapid development of medical technology, it is fascinating to wonder what people from the past, let’s say the 16th century, would have said about these new inventions.
About 2 million people in the United States use a wheelchair, about half over 65. In fact, about 2.9 percent of the population over 65 use a wheelchair, and 5 percent of people over 70. The manual wheelchair accounts for about 85 percent of all wheelchairs.
Although the basic design of the wheelchair has changed little over centuries, the wheelchair operator has changed substantially. The modern wheelchair operator is no longer simply a passenger in a wheeled chair. The average operator is a much more independent user whose demands for mobility are not only unprecedented but also accompanied by a desire for maximum cardiovascular fitness, as well safety, convenience, and light weight.
Wheelchairs can be divided into four major types: manual general purpose wheelchairs, power wheelchairs, manual sports wheelchairs, and power mobility alternatives — basically, a motorized vehicle that is not shaped like a chair.
Manual wheelchairs are by far the most common for a variety of reasons: simple design, reliability, no requirement for expensive, heavy batteries, small relative size, ease of transport, low weight and, of course, low price when compared to the alternatives. But because of the need for manual propulsion, injuries are common.
The propulsion of a manual wheelchair involves unnatural motions. If these movements are repeated thousands of times per day, especially in difficult terrain or up a hill, the stress leads to several mechanical overuse syndromes, including shoulder, wrist, forearm, and hand, as well as carpal tunnel syndrome in numbers ranging up to 3 out of 4 long-term users of a manual wheel chair. Obviously switching to a powered wheelchair would solve many of these problems, but would also remove the main source of aerobic exercise and calorie use that wheelchair-bound people have, which can result in worsening of a variety of metabolic conditions, a decreased level of cardiovascular fitness, and an increase in obesity.
All this is about to change. A small start-up company named LeverDrive, in Tucson, Ariz., has recently patented a design so simple that it leaves the reader wondering why this was not developed years (or centuries!) ago. The design incorporates a simple modification that uses a lever to propel the wheelchair. Virtually any existing chair can be modified using an Allen wrench (included in the package) and standard open-end wrenches in just a few minutes to replace the existing wheels with a wheel/lever system. The lever extends upward from the hub, which contains a one-way bearing.
The result is a wheelchair with an aluminum lever with a contoured handle grip located just above the armrests in an ergonomically correct position. To move forward, the occupant moves both levers forward, applying the force. The mechanism freewheels backward, which returns the levers to the original position in a smooth push-up or reverse rowing motion, to propel the chair forward. The lever has a braking mechanism, similar to the brakes on a bicycle, that works by simply pulling the levers toward the occupant. The brake shoe is mounted on the lever so that it contacts the chrome propulsion ring, which has been attached directly to the spokes of the wheel to minimize the width of the mechanism. Pulling a lever inward with one hand while pushing the second lever forward with the other hand, one can move a wheelchair in a tight circle. You steer it by braking one wheel or the other.
A major functional issue with traditional manual wheelchairs is holding the wheelchair steady while maneuvering up a hill. In a traditional wheelchair, the hands must be removed or slid from the wheel backward for the next forward motion. This gives a standard wheelchair the tendency to roll backward. The technique to propel a traditional manual wheelchair up a slope results in a rather complex and potentially dangerous motion.
With the LeverDrive, the user can easily negotiate ramps, propelling the user up the ramp or applying the brakes for a smooth descent. The mechanism in the hub prevents the chair from rolling backward. By combining the braking mechanism and the propulsion in the same levers, the occupant can apply the brakes in one smooth motion that is safer, more comfortable, and uses less effort.
Lifting the lever disconnects the drive rod from the axle, shifting the chair into neutral for standard manual operation.
Across carpeting, grass, soft dirt, gravel, and sand, the LeverDrive wheelchair moves with less effort than a standard wheelchair. The simple drive mechanism also can be disengaged with a simple stroke for freewheeling and moving in reverse. All motions are intuitive and require little if any training. In an article in the Tucson Citizen, one 25-year-old who had suffered a spinal injury in a ski accident said that she could get around in rough terrain better with a normal wheelchair outfitted with the LeverDrive than in her $2,500, 12-pound titanium wheelchair.
LeverDrive costs about $1,000 and is available through www.leverdrive.com, the company’s Web site.
From a medical director’s perspective, a major goal for patients confined to a wheelchair is to maintain cardiovascular fitness. However, the limitations of manual wheelchairs with their overuse injuries soon led many patients to request a powered wheelchair. The very size and weight of these produce freedom and add significant maintenance costs. Managed care companies (as well as CMS) have long had strict criteria for approving powered chairs.
The development of the LeverDrive now opens up an interim step at an affordable price that might quickly become a stepped-care policy for companies wise enough to recognize the advantages of this new device. The LeverDrive again proves that Tomorrow’s Medicine will indeed lead to a healthier, more productive life for all of us facing medical challenges in our older years!
The author is a director in the value-based health department at Genentech Inc. Before taking the Genentech position, he received honoraria or other financial benefits from: Amgen, Amylin Pharmaceuticals, AstraZeneca, Biogen Idec, Centocor, Galderma, GlaxoSmithKline, Johnson & Johnson, Merck, Novartis, Novo Nordisk, Pfizer, Procter & Gamble, Q-Med, Sanofi-Aventis, Teva Pharmaceuticals Industries, UCB, and Wyeth. The views expressed in Tomorrow’s Medicine are the author’s alone.