New Prosthetic Hand Technologies Combine Cosmesis with Function

Miki Fairley

Form, Function Combine in New Hand Prosthesis

For years, conventional wisdom said that passive hand prostheses were non-functional; their only value was cosmetic. This was the assumption prosthetists, occupational therapists, and physicians, and others were taught in school. However, the real world of unilateral arm amputees and their daily activities reveals that passive cosmetic hands are anything but "passive."

A study done in England and the experiences of noted upper-limb prosthetics specialists in the US shows that "passive" prostheses are very much used for the many non-manipulative functions involved in everyday life, such as supporting, stabilizing, pushing, and balancing.

The study by C.M. Fraser, published by the Occupational Therapy Services, Aldenbrooke's NHS Trust, Cambridge, didn't rely on amputees' self-reporting alone. Researchers went to the homes of amputees and videotaped them performing prescribed everyday tasks, such as making and serving a hot beverage, buttering and slicing a piece of toast, writing on a piece of paper, sealing it into an envelope, and then removing it from the envelope.

Fraser's paper states, "Using video analysis, the study demonstrates that for non-manipulative actions, cosmetic prostheses are actively used in the performance of everyday tasks as frequently as functional prostheses. The study provides evidence for a cosmetic prosthesis to be presented to an amputee as a realistic initial prosthesis and not as the option of last resort if a functional prosthesis is rejected."

In his study, Fraser gave a heads-up for occupational therapists to not only train prosthetic users to grasp and manipulate objects such as small blocks on a table, but also to help prosthetic users to master the large number of real-world non-manipulative tasks they do each day. Fraser said, "It is also recommended that training is provided in the use of cosmetic prostheses in twohanded tasks."

"Facility with the prosthesis was mostly about manipulation and grasping, when in reality they often don't use it for that-they use it for other things," said Tom Passero, CP, president and clinical director, Aesthetics Concerns Prosthetics Inc., Middletown, New York, makers of Livingskin ® silicone prosthetic products. "That was a revolutionary thing for me to learn, and it verified my experience in trying to make a usable tool, which is what a prosthesis is. It's put on to perform certain activities or, in the case of Livingskin, to blend into certain activities, so that other people aren't focusing on the amputee's prosthesis, but rather on the person's eyes, words, or the presentation they're making during a meeting."

New Knowledge Sparks Innovation

This revelation is sparking an innovative revolution in cosmetic hand design at Aesthetic Concerns/Livingskin.

The new hand being developed at Livingskin combines both function and appearance, flying in the face of the traditional view of cosmetic prostheses, said Passero.

Information from the Fraser study, experiences and observations of upper-limb prosthetic specialists, and amputees themselves "made it very clear that new assumptions need to be generated about prosthetic restoration for unilateral arm amputees and innovation in the thinking of prosthetists who fit them-and that there needed to be development in the design of terminal devices that really reflect people's use patterns," Passero said. The innovative hand is currently being used by a select number of patients "who understand the developmental nature of the device," Passero explained. Current plans are for the hand to be commercially available early in 2006.

Figure 2

New Armature

"One of the demands by unilateral arm amputees we have seen in the last ten years is for an armature mechanism inside the silicone to make the prosthesis look more real and that would duplicate the function of the bones, so that people can do various activities," Passero continued. He noted that unilateral amputees comprise by far the largest number of arm and hand amputees, and that the prosthetic needs of bilateral amputees are much different. Although all Livingskin hand prostheses currently use an armature, the armature puts the fingers in a curve shape. "However, our natural fingers don't bend in a curve; they bend at the joints," Passero commented. The new hand uses an armature which bends fingers at the joint, thus more accurately reproducing the anatomical shape of the hand. The joints are able to lock and unlock. The joints of the fingers and thumb are pre-positioned, that is, placed in the desired position by the amputee's other hand in order to perform certain tasks, thus increasing the functionality of the device.

Patients contributed to the design of the new hand by discussing the tasks they wanted to be able to do. For instance, one patient said, "I want to do push-ups, and I want to be able to lift a curling bar."

"We had to be innovative," said Passero, "so she could flatten her hand out completely to do push-ups, then stand up and bend her fingers back to lock around a curling bar and lift weights." He added, "Nothing we had at the time or that was commercially available was able to do this."

Current Livingskin hand prostheses use a strong braided stainless steel for the armature. The new hand's various armature parts are machined from a lightweight stainless steel and aluminum, Passero said. "We're also experimenting with plastics that can be machined, to make a very light and durable prosthesis."

"So the combination of function and form evolved into this particular development for partial and full hand amputees," Passero summed up. "It's been both fun and complicated, like all breakthroughs are."

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This article has been reprinted with permission from the O&P Edge November2005 Vol.4 No.11