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The Deka Arm – The Real Bionic Limb

By: Zack Duncan

Ever since movies like “Star Wars” and “The Terminator”, people have wondered about having body parts like the ones seen in these films. And thanks to the efforts of Dean Kamen, we are closer than ever to that reality.

For as long as anyone can remember there have been wars. Some are fought nobly and some for other reasons. Since the beginning of the most recent war in Iraq, Americans have been coming back home bearing the scars and wounds they gave in defense of our great nation. The army has spared no expense to save the lives of these brave soldiers when overseas. If they suffer a serious injury that causes loss of a limb, more than likely they will have to wear a prosthetic when they come home that hasn’t been updated much since World War II. Even though the technology of our world is growing by the day, constructing a robotic arm with a fully functional hand has been no where near possible, until now. The DEKA arm is the latest breakthrough in a $100 million Pentagon program known as “Revolutionizing Prosthetics.”

Fred Downs is the head of prosthetics for the Veteran’s Health Administration and has been wearing a prosthetic arm after he stepped on a landmine in Vietnam in 1968. According to Downs, the arm he wears is “a basic hook. I can rotate the hook and lock it. In those days [1968] they didn’t have a lot of sophistication about it. They fit you and say ‘This is your arm, this is your leg.’ And it was the best technology in those days. You just had to make yourself learn how to use it, and I did.”

Leading the “Revolutionizing Prosthetics” project is Dr. Geoffrey Ling, a neurologist and U.S. Army Colonel. “There is a hook, like something out of Peter Pan, and that is just unacceptable.” When touring around the Walter Reed Medical Army Center and meeting the troops he is working for, Ling states, “We have a saying in the military, ‘Leave no one behind.’ We are very serious about that. And that doesn’t mean just on the battlefield but back home as well.” And because this is such a big project, Dr. Ling has enlisted the help of Dean Kamen, who is widely considered a “rock star” in the world of inventors.

This new prosthetic, comically named “the Luke arm”, after the neat prosthetic worn by Luke Skywalker in the movie Star Wars, is funded by DARPA, the Defense Advanced Research Project Agency. Kamen’s New Hampshire-based medical products company known as The Deka Research and Development Corp. is the head of the project of the Deka arm.

A 650 square-meter space on the second floor of Kamen’s building is solely dedicated to the advancement of the Deka arm. In the entrance is a life size Terminator statue that is missing it’s left arm, which has been replaced by the harness of the Deka arm. Volunteers, like Chuck Hindreth, come to Deka to help engineers prepare for clinical trials. Hindreth lost both of his arms after suffering electrocution while painting a power substation over 26 years ago. Since then, Hindreth has had two prosthetic arms since that accident, although he never wears them. After the initial shock of having a limb amputated wears off, patients generally discontinue wearing their prosthetic. This is because the discomfort of wearing the artificial limbs are not worht the small amount of assistance provided by them. Most get hot, sweaty, slippery, and generally uncomfortable.

When approached by Ling and DARPA director Tony Tether in 2005, Kamen thought they were crazy, but in the “good kind of way” according to Kamen. The creation of a next-generation prosthetic arm had absolutely no financial incentive. Due to the enormous development and research costs, no private company would take the risk in the decently small market, unless DARPA funded it. Only about 6,000 Americans require arm prosthetics each year. After going around the country and viewing different prosthetics, Kamen was swayed to take on the project when he noticed the large technological differences in prosthetic arms compared to prosthetic legs. According to Kamen, “Prosthetic legs are in the 21st Century and prostetic arms are in the Flinstones.” Until the Deka arm, the “state-of-the-art” prosthetic arm has consisted of three powered joints but doesn’t provide much functionality. For this reason, most users still use the old fashioned hook-and-cable device. Despite which one they use, the user will experience three degrees of freedom: movement of the elbow, movement of the wrist, and the open and close ability of some type of hook.

The goal of Kamen and “Revolutionizing Prosthetics” was to create a device that represents a real arm as accurately as possible. They are able to do this because of the advancement in recent technology. Power consumption had become efficient enough and microprocessors had gotten small enough to make it possible to stuff motors, lithium batteries, control electronics, an wiring into a realistic arm-sized device. The process was still difficult according to Ling.”You are asking an engineer to build an arm that can everything your arm can do and confine it to a package the size of – an arm. In addition to that, it has to look and feel like an actual arm!” What was wrong with the previous arms was a lack of agility. The old arms had three degrees of freedom where the actual human arm has 22 degrees of freedom. The fine motor control imparted by the huge amount of circuitry inside the arm gives the Deka arm amazing agility with an incredible 18 degrees of freedom. Engineers fought for space in the arm. The created workarounds when they ran out of space. For example, they used rigid-to-flex circuit boards which were then folded into the spaces condensed by a dense array of wires.

The movement of the Deka arm is incredible. The motor control is so precise taht it allows users to do things like pluck grapes off the vine, unlock a door, pick up a power tool, or even shake someone’s hand. This is possible because of the six different preconfigured grips. These grips include the Chuck Grip, Key Grip, and Power Grip. These different grips are simply shortcuts for the main daily operations of every human. A big thing with the Deka arm was that it be usable to anyone, despite their level of amputation. Every part of the arm has a set of electronics. The hand contains separate electronics and so does the forearm. The elbow is also powered with the electronics contained in the upper arm and the shoulder is also powered. The shoulder’s power can accomplish a feat currently unperformable by the prosthetics of today. The shoulder has the ability to reach up as if to pick something off of a tree.

In order for the arm to work, it must weigh less than the actual weight of a human arm. This is because an amputee’s skeleton can no longer be used as a means of attachment. For an amputation above the elbow, a harness is attached to the user. Engineers at DEKA modeled the arm after the statistically average weight of the female arm which is only about 3.6 kilograms. This weight includes all of the electronics and the lithium batteries! Surprisingly enough, the arm is not made out of titanium, which is the popular light metal. Titanium is too heavy for the requirements and can not be made thin enough without breaking. So, the Deka arm is made mostly of aluminum.

But the main problem with prosthetic arms is discomfort. Like I mentioned before, prostetics can become very uncomfortable, which is why people tend not to use them. Previous arms are designed to connect with the greatest surface area from the prosthetic to the limb. The amputee’s residuum, or stump, is crammed into the prosthetic. The strain of normal use causes discomfort and even pain to the user. The design of Deka’s new socket can be used with the Deka arm or even be applied to traditional arms for improved use. But how does a person move the Deka arm? There are two ways, in fact. The first is through an optional surgical procedure. Todd Kuiken, a neuroscientist with the Rehabilitation Institute of Chicago, has had recent success with rerouting the residual nerves of amputees. The nerves connect the some 70,000 nerves in the arm to the upper spinal cord. In a normal body, the nerves travel from the upper spinal cord, across the shoulders, down into the armpit and finally down into the arm. Kuiken took these nerves out of the armpit and moved them under the clavicle and then connected them to the pectoral muscles. When the user thinks about moving their arm, the signals travel down the nerves now connected to the chest. The chest muscles then contract. The contractions are sensed by electrodes on the chest which then sends signals to the prosthetic arm, moving the arm. This procedure enables the user to use the arm with his/her own muscles making the arm like a part of the users flesh and blood.

The second way of controlling the arm is by way of tractors. A tractor is a small motor that vibrates which is secured against the user’s skin. A sensor on the hand is connected to a microprocessor that sends a signal to the tractor which changes the grip strength of the hand. This allows a user to know how tightly they are gripping something. The softer the vibration, the lighter the grip and vice versa. When Hindreth tried out the arm, he said “I can do things I haven’t one in 26 years. I can peel a banana without squishing it.” The arm is maneuvered by joystick-like controllers placed within the soles of Hinreth’s shoes. When Hindreth pushes down with his left big toe, the arm moves out and when he pushes own with his right big toe, the arm moves back in. These foot switches, which are completely customizable, are connected by long, flat wires, however, like everything else in the world, there is a wireless version already in the making.

When the Deka arm came out to the press, Dr. Ling was very sanguine in regards to it’s future. According to Ling, “We are trying to get a transition partner so it can go into clinical use as well as a commercial partner to get the arm out to patients. This is no longer a science fair project. Since the research and development of the Deka arm has been costly, any company can now take over the Deka arm and look for cost-efficient ways to manufacture it. A state-of-the-art prosthetic arm these days, depending on the degree of amputation, can cost in upwards of $100,000. Rick Needham, project managaer on the Deka arm, says the goal is to keep the price of the product as close to this price as possible. However, before the arm can even be commercialized, it needs to get approval from the FDA. The only way the FDA will approve the Deka arm is through clinical trials. However, it is thus far unclear who will pay for these clinical trials needed for approval. Funding from DARPA usually ends as soon as a project is picked up by another organization willing to fund the project. However, Deka currently does not have any transition partner like this yet.

According to DARPA spokesperson Jan Walker, “Clinical trials certainly have a price. If no one funds the cost, then trials obviously can’t happen.” But according to Walker, the DARPA procedures for funding is not set in stone. Sometimes DARPA continues a low-level of funding until the organization is able to increase its own fundings and other times DARPA’s funding just ends completely. Although specific plans on funding for the Deka arm are unknown. Should funding from DARPA continue with the Deka arm, Kamen and his group of engineers and scientists would like to begin take-home clinical trials sometime this year. Certainly within the next two years we would like to submit to the FDA for approval to sell the arm.” states Needham. Kamen may be talking to the Walter Reed Army Medical Center based in Washington, D.C. as well as various other Veterans Affairs hospitals. According to Hindreth, he absolutely can not wait to take home his very own Deak arm. “My wife can’t either. She says ‘Oh yeah, I got lots of stuff for you to do around the house.'”

The advancement in technology truly is amazing. It is absolutely a wonderful site to see people, some, like Hindreth and Downs, who have spent a vast majority of their lives without the use of their arms, being able to once again hold things, touch things, and use what basically is functional arm. It gives a brand new hope to U.S. soldiers who are overseas risking everything to keep us safe. They can now, at least, have a little bit of humanity restored to them after making such an honorable sacrifice.

April 17, 2009 Posted by | Technology News | 3 Comments