Upper Limb: Kudos and Caveats
October 2009 Issue
As major breakthroughs in upper-limb prosthetic technology continue to roll out in today's clinical practice, two specialists in upper-limb prosthetics describe what has most impressed them—and what challenges remain.
"The first multi-articulated object-compliant hand [the i-LIMB™] is an astounding advance," says Carl Brenner, CPO, FAAOP, director of prosthetic research for the Michigan Institute for Electronic Limb Development, Livonia.
The Otto Bock DynamicArm® elbow and microprocessor control system for transhumeral or higher limb loss/deficiency is the top choice for John Billock, CPO, CPO/L, FAAOP, executive/clinical director, Orthotics & Prosthetics Rehabilitation Engineering Centre Inc., Warren, Ohio. Billock says that before development of the DynamicArm with its multiple control options, he "was not a strong advocate for electric-powered elbows for persons with amputation or limb absence in the mid to distal one-third area of the upper arm." Although he would like it to have more than two myoelectric controls—which he believes would provide more natural movements in a total-arm prosthesis than do two-site controls—he is impressed with the DynamicArm's speed and lift—two features long desired by amputees.
Billock also likes the device's software, which he describes as being user-friendly despite the complexity of its multiple control options.
"Regardless of this," he adds, "I believe there is still a place for the simplicity of a hybrid Bowden-cable control and myoelectric two-site EMG muscle-control system. It still represents, in my opinion, the most effective way to achieve simultaneous control of a transhumeral prosthesis with a mechanical elbow and myoelectrically controlled hand."
Billock notes another challenge in optimal functional design for transhumeral or higher-level amputations—the continuing absence of a "truly acceptable electric-powered wrist that provides at least 50 percent of the torque that is comparable to that of an electric-powered screw driver. The technology is there," he says, "but just hasn't yet made the priority list or drawing board of the manufacturers and developers." However, he hopes future developments will address this deficiency.
Billock says he is excited about the technology being developed by the U.S. Department of Defense and the Defense Advanced Research Projects Agency (DARPA). He notes the pioneering work in targeted muscle reinnervation (TMR) surgery pioneered by Todd Kuiken, MD, of the Rehabilitation Institute of Chicago (RIC), Illinois, which complements various prosthetic technologies for high-level amputees. Billock agrees with Brenner that the i-LIMB Hand is another major advance, as is some emerging technology from Otto Bock HealthCare, Duderstadt, Germany.
The number of new upper-limb amputees, apart from military casualties, has significantly dropped, Brenner points out.
"There are about 2,000 new patients per year with amputations at wrist level or higher, not including the approximately 300 children born with limb deficiencies each year, compared to about 65,000 new lower-limb amputees annually—a ratio of about 30 to 1." The number could drop even more, he says, due to better limb-salvage techniques; fewer manufacturing jobs, along with better industrial-safety standards; and far fewer farmers, and thus farming accidents, than in the past. Plus, there appears to be about a 3-percent increase annually in lower-limb amputation due to vascular issues and an aging population, which could soon increase the ratio to about 40 to 1.
Despite these dazzling technological advances, another concern brings upper-limb issues back to earth with a thud—how to pay for these devices.
The devices are costly, due to research and development costs and the lack of economies of scale due to a relatively small pool of users.
Research for evidence-based practice (EBP) to justify the use of high-tech devices to payers is underway but will take time to fill the current gap. Meanwhile, both Brenner and Mike Allen, CPO, FAAOP, clinical director of Allen Orthotics & Prosthetics, Midland, Texas, and a past president of the American Board for Certification in Orthotics, Prosthetics and Pedorthics (ABC), have some creative, and related, ideas on how to bridge the gap to document the benefits of a treatment plan.
Allen would like to see manufacturers loan out componentry for integration into prototype prostheses that patients could use in videos and with other documentation tools to demonstrate the vocational and avocational benefits of the components in activity-specific functions.
Brenner advocates the use of a preparatory/evaluation/training (P/E/T) prosthesis. In such a prosthesis, after diagnostic test sockets have been evaluated and one or more are selected, various components can be added and evaluated by the clinic team and patient and documented for functional benefits. P/E/T prostheses also serve valuable preparatory and training functions before a definitive prosthesis is made. [For more information, see "The Use of Preparatory/Evaluation/Training Prostheses in Developing Evidence-Based Practice in Upper Limb Prosthetics," by Carl D. Brenner, CPO, and Joseph K. Brenner, CP, JPO: Journal of Prosthetics and Orthotics, July 2008.]
Allen adds that if manufacturers provided more online training for practitioners and technicians, it would help these professionals stay up to date with emerging technologies, optimize the devices for their patients, and avoid problems, thus enhancing patient satisfaction and manufacturers' bottom lines.
Despite rocks in the road, Billock sums, "Having been involved in upper-limb prosthetic research and clinical practice since its introduction in the United States in the late 1960s, these are without a doubt the most ambitiously exciting and promising times in the history of upper-limb prosthetics development."