Oct 31 2012
It appears that we are near the beginning of a new modality in medicine – the use of computer controlled and powered robotics for therapeutic purposes. At present such technology is in its infancy, but is giving us a glimpse of what it will become.
Recently Vanderbilt University announced that its team at the Center for Intelligent Mechatronics has developed an exoskeleton that paraplegics can wear on their legs to allow them to sit, stand, and walk. This is essentially a mechanized orthotic that paraplegics can wear on their legs. The researchers describe it as a “Segway with legs” – referring to the computer technology that controls the exoskeleton, which responds to the user’s movement. If the user leans forward, then the legs will walk. If they lean back, then they will sit.
Like any technology, you can take either a glass half-full or half-empty view of this device. I will cover both – first the good.
Their system has some advantages over previous systems. It is about half the weight, coming in at 27 pounds while other lower extremity exoskeletons weigh 45 pounds. The exoskeleton is also small enough to fit in a standard wheelchair while being worn, and can be put on and taken off by the user alone. As described above, this system also incorporates intelligent control technology. Users with partial paralysis can have their own movements augmented, while for those with complete plegia the exoskeleton can do all the work.
The exoskeleton allows for a significant increase in independent mobility for the user. This can be significantly helpful in getting paraplegics mobile, which would be advantageous to overall health and reduce the risk of certain complications, like bed sores.
Now for the limitations: The system does not allow for sufficient balance to be used without crutches. This means that users require significant upper body strength and control in order to walks with the legs. There is also a weight limit, so overweight paraplegics, those over 220 pounds, cannot use the device. In short, users need to be fairly physically fit.
The technical specifications indicate that the onboard lithium polymer battery can last for about 1 hour of use between recharges. It does not indicate how long it takes to recharge, but I would guess several hours. It also indicates that the sound generated by the device is 55 dBA, with ambient noise being 38 dBA.
If we consider the various components of these types of systems, it appears that the engineering is fairly solid. The devices are well-engineered, reasonably powerful (although this is still a limitation) and increasingly light and portable. Battery technology to power the device is a limiting factor (as it is with many applications). There is a great deal of research into building a better battery, as so many technologies depend on battery technology (like electric cars, for example). The powered exoskeleton is one more technology that will benefit from general improvements in battery technology.
The computer control seems to be the most advanced aspect of this device. Computers themselves are light and powerful with little energy consumption, and the software to provide intelligent control is already fairly advanced. I’m not sure how close this technology is to providing independent balance (without the need for crutches for stability). Balancing algorithms already exist, such as with the powered wheelchairs that can balance on one set of wheels and climb stairs. There are already robots that can balance and walk on two legs, but nothing small enough to function as an exoskeleton.
There is also the question of how users will adapt to robotics, whether as an exoskeleton (orthotic) or as a replacement for lost limbs (prosthetic). So far the research here is very encouraging. Virtual reality testing indicates that the brain is highly plastic in this regard, and can potentially adapt to new parts so that they feel natural, as if they are part of the body. In other words, it appears to be theoretically possible to neurologically close the loop on orthotics and prosthetics, so that they feel and function like a natural part of the body.
One interesting aspect of this is user control of robotic devices. This exoskeleton uses muscle and movement control – it responds to the user’s own movements. However, other researchers are working methods of more direct brain control. These approaches involve internal or external electrodes that read brain activity and software that can learn to translate the activity into the desired action. There is a learning curve for the user as well, but eventually the user and computer can learn to communicate and robotic limbs may be able to respond naturally to the desires of the user.
Current use of powered limbs is highly limited, but there is a steady stream of incremental advances in every aspect of the devices. What I think we have now is mainly a glimpse of the future. We are nowhere near the Bionic Man level of technology, but we are inching closer to the day when such devices will essentially restore function and mobility to the paralyzed.
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