American Academy of Orthotists & Prosthetists
Professionals Advancing Care Through Knowledge
Care Through Knowledge
New Possibilities for Upper-Extremity Prosthetics
Karl Lindborg, CPO
Not since the Cold War has there been such focused attention on the topic of an "arms race." I am of course referring to the recent military research focus on the race for upper-limb prosthetic arms—not the nuclear arms race of the 1970s and early 80s. Both private companies like Touch Bionics and military research organizations like the Defence Advanced Research Projects Agency (DARPA) have been working to develop revolutionary prosthetic solutions for both military and civilian patients.
 |
What is remarkable amid all the attention that has been focused on research-stage projects like DARPA's Revolutionizing Prosthetics Project is the recent commercial introduction in the summer of 2007 of the i-LIMB™ Hand, the world's first commercially available bionic hand. It has been welcomed as an exciting technology by patients with upper-limb amputations and deficiencies and O&P professionals alike. When Touch Bionics developed the i-LIMB Hand, there were five important areas to address: mechanics, software and controls, cosmesis, patient selection, and reimbursement challenges.
Mechanics
Current electromechanical hands used in conjunction with myoelectric signals, touch pads, or linear transducers have typically been hands functionally using a "3-jaw chuck" grip.
This is where the thumb is fixed in direct opposition to the first and second fingers resulting in these electromechanical hand's inability to utilize the six primary hand grips used to manipulate different objects.
In order to understand the benefits of the i-LIMB Hand one should envision the hand effectively as a chassis for four articulating powered prosthetic digits, or ProDigits, and a powered ProDigit thumb.
 |
The compliance of the i-LIMB Hand grip creates a new paradigm for how grip force and power are applied to the activities of daily living (ADLs). There is no longer a need for inhuman levels of pinch force to be applied to a terminal device. The i-LIMB Hand can support 45 pounds of weight and yet the articulating fingers produce realistic and dexterous hand movements that appeal to the full spectrum of male and female patients.
Simply put, the grasp of the i-LIMB Hand functions more like that of a human hand, with the articulating fingers able to close tightly around objects. Built-in stall detection tells each individual finger when it has sufficient grip on an object and, therefore, when to stop powering. Individual fingers lock into position until the patient triggers an open signal through a muscle signal.
Similar to the human thumb, the i-LIMB Hand's thumb can be manually rotated 110 degrees into different positions. This is a revolutionary step forward for electromechanical prosthetic hands. With the inclusion of a manually positioned opposable thumb and the individually motor-driven digits, a prosthetist has the capability of providing a cosmetic electromechnical hand that can recreate fine tip pinch grip with fingers opposing the thumb. Positioning of the thumb also enables the user the advantage of multiple grip configurations, many of which have not been previously available to patients, including those shown in figures 3 through 6.
 |
Because each of the five fingers are driven by separate motors, the pinch force required to grasp an object with the i-LIMB Hand is spread out to all five fingers as opposed to the three primary fingers used with the "3-jaw chuck grip" of current electromechanical hands.
Software and Controls
With the microprocessor-controlled i-LIMB Hand, Touch Bionics is utilizing the myo-electric principles used in existing devices while taking advantage of the mechanical advancement offered by five individually powered digits. The articulating finger, the key point of innovation from Touch Bionics, provides the biggest benefit to the patient or user.
Because easy adaptability is a critical goal for an upper-limb amputee, Touch Bionics adopted a traditional myoelectric control strategy to operate the i-LIMB Hand. As a result, existing myoelectric users can easily adapt and operate the hand immediately. This is of great benefit to both the patient and the clinician.
Cosmesis
Some patients, predominantly military personnel, particularly love the robotic nature of the uncovered i-LIMB Hand and prefer not to wear it with a cosmetic glove. However, because of the need to provide a grip surface and to protect the hand from dust and moisture, Touch Bionics developed the i-LIMB Skin, a thin layer of semi-transparent material that has been computer-modeled to accurately wrap to every contour of the hand.
 |
For the end user, the i-LIMB Hand has the advantage of being more anatomically correct than any other electromechanical hand available on the market. This not only allows for increased functionality but also a vastly improved cosmetic appearance. The challenge to develop and improve on a high-definition cosmesis of superior quality is a challenge experienced by everyone supplying cosmetically pleasing prosthetic hands. Touch Bionics continues to develop custom and high-definition cosmetic products from its cosmesis partners, including its first off-the-shelf version from LIVINGSKIN.
Patient Selection
As prosthetists, we realize that many patients simply want to have the latest, greatest device available. Sometimes this is not the most appropriate clinical decision. In some cases, it is recommendations from others that results in inquiries regarding the i-LIMB Hand. To date, only one patient has returned the hand because the patient felt it was a little too complicated. It is important to note that this user was also unsuccessful with other myoelectric devices.
As clinicians we must also realize that patients may prefer the anatomical accuracy, while others prefer the new levels of function, but it is always important to assess the viability of the new patient in advance of the clinical and commercial commitment. Consider a heavy user, such as a farmer, who would be better off using a more rugged terminal device. The ideal candidate for an i-LIMB Hand is an average-sized user, performing the average ADLs.
Reimbursement Challenges
 |
The financial consideration of adopting a new terminal device is of additional concern to Touch Bionics' U.S. patients. About one-third of patient cases have been approved for reimbursement on first presentation. Successful claims have been processed by many mainstream insurance providers, and, of course, the i-LIMB Hand has proven very popular with military users—both active and veterans.
The Next Step
There are many unknown factors that became clear once the i-LIMB Hand was released and patient and clinician feedback was received. While the i-LIMB Hand is now considered by Touch Bionics to be completely market ready, continual improvement underpins everything that Touch Bionics does.
Touch Bionics is currently undertaking a ten-patient independent outcome study in Sweden. The company expects to have the results by summer 2008 and will present comparative data between the i-LIMB Hand and other terminal devices.
 |
As the recent focus on upper-limb prosthetic technology emerges, it is evident that the world of prosthetics has entered into a new sort of "arms race." The resulting success of developments that come out of this push for new technology will be directly related to how prosthetists and users apply this technology. The i-LIMB Hand has opened the door to new possibilities to upper-limb prosthetics.
Karl Lindborg, CPO, recently joined Touch Bionics as the head of clinical advocacy. He has more than a decade of clinical experience, his most recent position having been with the Department of Veterans Affairs (VA). He can be reached at
Earn PCE Credits from this article
Take the quiz at the Academy's Online Learning Center.
Members Only
