Prosthetic science – long a rather docile entity characterized by periodic improvements making momentary headlines – has suddenly discovered steroids.
Generated by new applications of space-age materials and digital technology, fresh thinking about how to enhance prosthetic outcomes, and America’s experience in rehabilitating its amputee casualties in Iraq and Afghanistan, prosthetics in the 21st century has become downright exciting, and a bright future of continuing innovation awaits.
This momentum swing might well be traced to the introduction of the C-Leg® microprocessor-controlled knee-shin component for transfemoral prostheses in 1997. The C-Leg has become the poster child for adaptation of computer technology to limb prostheses, having now been fitted on more than 13,000 people worldwide.
But fame is fleeting: The C-Leg has been eased off the front page by some remarkable new upper-extremity components, the first powered lower-limb prostheses to reach the market, and the promise of a whole new way of attaching prosthetic limbs to the body. We’re not yet to the time of Steve Austin, TV’s Six Million Dollar Man, but led by some inspiring research initiatives we’re getting there.
Otto Bock’s C-Leg and its recently introduced competitor, the Össur Rheo Knee™, use an on-board microprocessor to adjust prosthetic leg swing in real time in response to the wearer’s cadence, toe and heel loading, and other gait variables. As a result, the leg is ready for heel strike at just the right instant, providing above-knee amputees with unprecedented security, gait flexibility, greater freedom of movement, natural swing motion and reduced walking fatigue.
Microprocessor-controlled knee systems enable wearers to change walking speed, negotiate uneven terrain, walk up and down slopes, and descend stairs step-over-step.
The C-Leg now incorporates several new enhancements that improve its performance even further, including:
• A new standing mode, which stabilizes the knee, taking weight off the sound limb and allowing the user to relax while standing;
• A wireless remote control, which enables users to switch easily between modes as well as fine tune swing phase dynamics for different activities; and
• A widened scope of application that now includes transfemoral, knee-disarticulation, hip-disarticulation, and hemipelvectomy amputees.
Sockets and a New Attachment Method
Technologically advanced distal componentry demands comparable improvement at the crucial point of integration between prosthesis and biological limb. Typically this connection is achieved by a socket suspended from the residual limb.
Among the advances in socket design and fabrication are new and improved CAD-CAM systems, through which more precise, more functional and more comfortable sockets can be provided than ever before in substantially less time.
CAD-CAM systems include a measurement device, or digitizer, to input the residual limb topography; design software on which to create the unique socket shape that will address the patient’s physical capabilities, residual limb anomalies and functional desires as closely as possible; and a carving machine to render the finished socket from the finished digital design.
Recent improvements in prosthetic-orthotic CAD-CAM systems have made the limb measurement process considerably easier and faster for patients. With one of the new non-contact optical devices, such as BioSculptor’s hand-held BioScanner™, a test socket for an amputee patient can be fabricated in less than an hour, shortening the pre-prosthetic period by days and giving prosthetists more time to spend with their patients.
Among emerging socket designs, the Marlo Anatomical Socket (MAS) stands out for its innovation and potential benefits to appropriate above-knee amputees. This socket features a markedly lower posterior brim than other A/K designs and a pronounced medial alignment, which facilitates a more normal and more energy-efficient gait than provided by other ischial containment or quadrilateral sockets.
MAS users generally demonstrate an increased range of hip motion and report the socket is more comfortable to wear, whether standing, walking, or sitting down.
Perhaps the greatest potential development in prosthetic attachment does away with the socket altogether, instead anchoring the prosthesis to the residual limb by a titanium bolt surgically implanted directly into the distal residual bone. Though not yet approved by the Food and Drug Administration for use in the United States, this process of osseointegration has been used successfully with more than 100 lower-limb and more than 30 upper-limb patients in Europe.
Osseointegration shows the potential to eliminate most if not all of the problems inherent in prosthetic socket attachment for appropriate patients:
• End weight-bearing is restored
• Prosthetic limb control is greatly enhanced while energy expenditure is substantially reduced
• Risk of sudden prosthesis detachment from the body is minimized
• User perception of the limb’s place in space is much improved; and residual limb pain and skin breakdown caused by constant contact with the socket environment are virtually eliminated.
Osseointegration, already approved for dental and maxillofacial applications, is expected to be approved for orthopedic use in the United States.
For several decades, upper-extremity prosthetics has led the way in high-tech prosthetic applications with myoelectric control of battery-powered hand, elbow and wrist actuators. Leading systems such as Motion Control’s Utah Arm series continue to improve through upgraded components, while new offerings, such as the Otto Bock Dynamic Arm, help to raise the performance bar.
Like many newly introduced products, the Dynamic Arm offers certain advantages over the field, including faster elbow actuation, greater lifting capacity (13 pounds) and a more natural swing motion.
An intriguing new entry into upper-limb componentry is a new terminal device developed in Scotland that features five distinct fingers, each powered by separated motors. The i-LIMB Hand is still in its infancy – however, individual finger actuation is anticipated in the next few years with the development of improved control systems.
Powered Lower Limbs
Until now, powered components have been limited to upper-extremity applications. That all changed with the recent introduction by Össur of its Power Knee and Proprio Foot prostheses. These components, and others like them that will undoubtedly follow, promise to significantly reduce the effort and energy expenditure of walking while enabling appropriate amputees to ambulate confidently over uneven terrain and on stairs and providing a major assist for sitting and rising.
The good news is that the innovation we’re seeing today will become the reality of tomorrow. Prospects for improved prosthetic capabilities have never been brighter. Please call us to day for your free consultation. Our offices are located in Beaumont, Nederland and Jasper, Texas.