The State of The Art-ificial Hands | Orthopedics This Week
Large Joints and Extremities

The State of The Art-ificial Hands

Can you Guess Which Hand is Prosthesis? Source: RRY Publications LLC

The official launch of the Michelangelo Hand, the first hand prosthetic with an opposable thumb, will not take place until May 2012 in Leipzig, Germany. But Dale Feste, of Minnetonka, Minnesota, has been wearing the revolutionary new hand since December 16, 2011. According to his wife, “he was like a little kid with a new toy.” Feste, a retired teacher and public school board member, is the first civilian in the United States to have been fitted with the Michelangelo Hand. His wife credits that fact to “his inquisitiveness which takes away the fear of wanting to try. That is his personality; he likes to know how things work.”

The hand is perhaps the most individual and personal part of a person. However, research on upper limb amputations has been overshadowed by the enormous increase in lower limp amputations because of vascular disease. One in approximately 190 Americans are living with the loss of a limb and from 15% to 25% of those losses are of upper limbs. (Estimates are imprecise because in National Health Interview Survey-Disability data-collection studies, upper and lower limb amputations were not distinguished from one another.)

With the lack of documentation of upper limb loss, essential research also lagged on upper limb prosthesis development. That began to change only when the prosthetic and rehabilitation needs of injured service members from conflicts in Iraq and Afghanistan brought upper limb amputation to the forefront of debate and attention. That also changed when Otto Bock of Duderstadt, Germany, a manufacturer of prosthetics since 1919, assigned an engineer in Vienna, Austria to develop a new, improved artificial hand.

It was both the loss of his hand and his physical proximity to the company that brought Feste and Otto Bock together. Fifty years ago Bock’s son-in-law, Max Nader, had established a branch of the company in Minneapolis, Minnesota. When a rare cancer required the amputation of Feste’s right arm between the wrist and elbow he learned about the new hand under development by Otto Bock through the Prosthetics Laboratory firm that worked with Feste’s Mayo Clinic doctors.

Rightly figuring that the company might need testers for the new device, and living in the same neighborhood as the company, Feste introduced himself to Otto Bock and was promptly taken on.

Few parts of the body are as complex as the hand whose functionality is based on the perfect interplay among 27 bones, 39 muscles and 36 joints—along with nerves and tendons. The Michelangelo Hand replaces that complex natural system with two motors housed in the palm of the prosthesis. One controls the first two fingers and the other moves the thumb which can be repositioned. The system is myoelectrically controlled via two electrodes embedded in the socket of the prosthesis that fits over the end of the arm. The electrodes are located over opposing muscles—the triceps and biceps—and when the wearer tightens his muscles, the electrodes pick up the signal and the hand responds.

When Feste moves the muscle in his arm that corresponds to raising his wrist, the Michelangelo Hand opens. When he thinks, “lower my wrist”, the hand closes. “It is a very natural thing, ” Feste said. “I learned it very quickly. I still have the muscles and nerves in my arm and I do it normally.” He estimates that he became proficient operating his Michelangelo Hand within two or three weeks. “I would spend evenings picking up popcorn kernels, ” he said, “It was not a huge challenge.”

Feste said that there are basically two positions for the hand. One is called the “lateral pitch” where the thumb and fingers come together. “The first two fingers are the only ones powered, ” he said. “Otto Bock found in its research that we don’t use the other fingers so much—they are floaters. The first two are the power fingers and they come together.”

Feste demonstrated the “lateral pitch” position in which the first two fingers met to hold a piece of paper with a tight grip. “I find that to be my default position, ” he said. “I use that the most.” He said the grip is useful to hand a ticket to a ticket-taker or a bill to a cashier.

The second position, the “opposition position” is one in which the thumb moves to a position opposite the first or the middle finger. “This is the position that allows me to pick up small objects or something round – such as a can of soda—or carry a saucer with a cup of coffee on it, ” he said.

When he demonstrated holding the can, Feste explained that he had no sense that he was holding something or how hard he was squeezing it. His prosthesis could hold it for the entire day without any effort on his part. ”Everything is proportional, ” he said. “I have to apply my muscle slowly so that I can pick up an egg and not crush it. It is all visual as I do not feel anything. I do a lot of practicing with paper cups half full of water. I have to see when I squish it. It has to be visual.”

The hand mimics the natural hand in that, when the hand is opened, the fingers angle apart, away from each other. But when the hand is closed, the fingers all come together to meet in the palm. With a weight of 21 grams, the finger mechanism can take loads of up to 30 kilograms. Gloves come in six different skin tones and colored fibers inside imitate the natural vein structure of the hand. Feste wears a ring, given to him by his grandfather in Norway, on the ring finger of his Michelangelo Hand.

The hand also has a flexible wrist that can be set at seven different stops. Feste bent it up so he could rest his hand on his knee in a realistic pose. “If I want this to be rigid, I can lock it in, ” he said.

Feste is a patient model at Century College, White Bear Lake, Minnesota, one of seven schools in the United States that trains students to work in the field of prosthetics. He is the only patient at the college who is equipped with the myoelectric system.

Feste has found that wearing the Michelangelo Hand has proven to be unexpectedly psychological beneficial. Prior to receiving the new hand he wore a terminal device called the “greifer” which bore a strong resemblance to a metal hook. While he did not consider himself to be self-conscious wearing his powered hook, he experienced what he called a “personal revelation” when he put on the Michelangelo Hand.

As he explained it, “When I was wearing my greifer device and would walk into a room people would look me in the face and then immediately shift their gaze to my arm—because in their peripheral vision they were seeing something different. They had to look at it. I got used to that but I knew that they at once identified me as “the amputee.”

When I got my Michaelangelo Hand, which are cosmetically very good, people would meet me and not know that I was an amputee. They would look me in the eye and not look down because there was no reason for them to do so. Wearing the Michaelangelo Hand I can go into a public gathering and be defined first as a person and only second as an amputee. This way I remain me—like everyone else in the room—sort of incognito. This was a revelation to me.”

Dale Feste now looks on his amputation and his last years, not as a disaster, as a new adventure. “It is a problem-solving kind of adventure. I have learned, ” he says, “to marvel at the engineering of the human hand.” After wearing the Otto Bock test hand for months, Feste applied to his insurance company, Medica, for a Michelangelo Hand of his own. The request was approved in the fall of 2011 and he had his own hand before Christmas.


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