When the first computer was created more than 60 years ago, it weighed more than 60,000 pounds and required close to 2,000 square feet of floor space. The advent of the microprocessor in the 1970s revolutionized the computer industry and led to the development of the personal computer. Further refinements to microprocessors, which are now small enough to fit through the eye of a needle, have enabled the use of this technology to permeate virtually every industry, including the orthotic and prosthetic field.
Other technological advancements such as the introduction of composites, urethanes and polymers as well as improvements in suspension systems and hydraulics, together with the integration of electronics and microprocessors, have resulted in O&P devices that are more responsive and reactive to patients. In addition, as devices have moved away from exoskeletal to alignable endoskeletal devices, patients are able to do more, further driving advancements in componentry.
“When we give patients those products, they find that they can increase their functionality and mobility, and then they are asking for more and more,” said Bill Clover, vice president of research and development – Americas for Otto Bock HealthCare. “So a lot of the demand is coming from the increased activities and usage by the amputee.”
As a result of the advancements in technology, combined with the increased expectations of patients, the use of microprocessors in O&P devices today is widespread and can be found in upper and lower extremity prostheses as well as in a few orthoses.
Lower extremity prostheses
Microprocessors have been used in knee prostheses for more than a decade. The benefits of microprocessor-controlled knee prostheses for patients include increased stability, decreased energy expenditure and a more normal gait.
Microprocessor prosthetic knees available commercially in the United States include the following:
- C-Leg and Compact knees, manufactured by Otto Bock HealthCare
- Adaptive 2 and Smart IP knees, manufactured by Endolite North America
- Rheo and Power knees, manufactured by Ossur North America
- Agility MPC Knee, manufactured by Freedom Innovations (currently in limited release)
C-Leg and Compact knees
Otto Bock HealthCare’s C-Leg, which offers microprocessor-controlled hydraulic swing and stance phase, is targeted for higher activity level (K3 and K4) amputees. A similar version, the Compact, is also available but offers only microprocessor-controlled hydraulic stance and is targeted for lower activity level (K2 and K3) patients. Both prostheses use C-Soft software that allows prosthetists to make adjustments to the program using a computer.
The latest version of the C-Leg was launched in 2006. The stability and function of the new version of the C-Leg is essentially the same as earlier versions but includes some added features based on patient feedback, said Kristen Knox, MBA, market manager for Otto Bock HealthCare.
One feature added to the new version of the C-Leg is a standing mode that allows users to lock the knee quickly and easily between 7° and 70° so they can bear weight on their prosthetic side. The second new feature is a handheld remote control that allows users to automatically change the mode of the knee with a switch.
“Through the remote control, a patient can adjust swing phase for higher or lower dynamics. This option gives independence to the user without compromising the stability,” Knox said. “This does not affect a lot of the settings that the practitioner has spent the time optimizing but it does help in the fine tuning process. Patients can play around with just that one setting to help determine what their optimized settings should be.”
Knox noted no new features have been added to the Compact since its 2004 release.
Adaptive 2 and Smart IP knees
The Adaptive 2 was released in 2006 by Endolite North America, and is the second-generation of the Adaptive microprocessor-controlled knee prosthesis. Like its predecessor, the Adaptive 2 features hydraulic stance control and pneumatic swing control, and is targeted for higher activity level (upper K3 and K4) patients.
The Adaptive 2 features easier programming than the first-generation Adaptive prosthesis through the addition of a Wizard software program. The Wizard software allows practitioners to program the knee in approximately 15 or 20 minutes after patients walk for 200 to 250 steps, said Alan Kercher, education manager for Endolite North America.
The practitioner inputs the patient’s height and weight as well as the type of prosthesis the patient previously used into the Wizard program, which then automatically loads in resistances. A remote control enables practitioners to program the prosthesis in any environment without the need for patients to be “hard wired” to a computer.
The other feature added to the Adaptive 2 is a support mode that has increased the high level of resistance for stability at the heel strike, which releases at approximately 75% of the rollover allowing unrestricted knee flexion to happen, “so therefore the prosthesis is not dictating how they walk – patients are actually dictating to the prosthesis how they would like to walk and the prosthesis is giving them the resistances when required,” Kercher said.
A second microprocessor prosthetic knee released by Endolite which is the fourth generation over 14 years in 2006, the Smart IP, targets slightly lower activity level (K3) patients and features a mechanical stance control and pneumatic swing control. The Smart IP offers what Kercher refers to as a “plug and play” feature in which the prosthesis programs itself as the patient walks when opened by the initiation of three extension-to-flexion movements. Once the program feels comfortable to the patient, after approximately 150 steps, the patient sits or squats to flex the knee, waits 4 seconds and then stands up, at which time the programming stops, locking in that particular window of speed movement.
Kercher noted patients can repeat this process several times if needed as they go about activities in their own environment when they feel a need to “fine tune” the prosthesis by updating the program without removing any of the initial programming and without having to return to the practitioner. Battery power in the Smart IP can last up to a year without charging and is easily replaced by the user.
Rheo Knees and Power Knees
The Rheo Knee, which was released in 2005 by Ossur Americas, features microprocessor-controlled swing and stance phase coupled with a magnetorheologic actuator. The prosthesis is targeted for unlimited community ambulators (K3) who have the ability to walk at a varying cadence.
Unlike the other microprocessor knee prostheses, the Rheo Knee uses a magnetorheologic fluid instead of a hydraulic control mechanism to regulate resistance, which offers patients proportional resistance to the load they put on the knee itself. The knee’s Artificial Intelligence software features a dynamic learning matrix algorithm that “learns” the patient’s gait during a setup mode, said Duane Romo, CPO, internal education manager for Ossur Americas.
“It is literally learning the patient’s gait while he or she is walking and determining how much resistance is required, the loads being placed on the knee, the timing, etc., so it builds this profile and learns the patient’s gait basically,” Romo said. “The practitioner can then go back in and tailor certain aspects of different areas of gait; they can change resistances and all sorts of things if necessary, but essentially in only a matter of minutes, the knee mechanism has literally programmed itself right up front for the patient.”
Romo noted the Rheo Knee is inert with all of the sensors built into the unit itself. In addition, practitioners have the ability to put virtually any foot underneath the prosthesis.
Ossur’s most advanced component and the first powered prosthesis for transfermoral amputees, the Power Knee, was launched in 2006. The Power Knee replaces lost muscle function and provides powered extension and powered flexion, said Romo. In addition, the actual motions that are being accomplished under power also are coordinated with the patient’s gait patterns.
“The Power Knee will forcibly drive itself into extension or forcibly drive itself into flexion,” Romo said. “The knee mechanism will functionally stand patients up out of a chair, and it will allow them to walk up stairs foot over foot, so what we are seeing is a diminished amount of effort that the patient has to put into ambulation while they are utilizing the Power Knee. They are not just swinging forward and having it advance as a pendulum – the leg drives itself forward.”
Like the Rheo Knee, the Power Knee targets unlimited community ambulators (K3). Both the Rheo and Power Knees are part of what Ossur is calling its Bionic Technology line. A third lower extremity prosthesis, the Proprio Foot, completes the Bionic Technology line.
Agility MPC Knee
Freedom Innovations recently moved its Agility MPC Knee into a limited release in preparation for the commercial launch scheduled for early 2008. The device reportedly pairs microprocessor-controlled stance stability with next-generation hydraulic swing characteristics to provide a more natural, comfortable gait. Patented Accel Control Technology measures inputs 1,000 times a second and reacts within 10 milliseconds. According to Meghan Eilbeck, marketing manger for Freedom Innovations, the result is a highly responsive prosthetic knee that requires less cognitive effort from its user.
The Agility MPC Knee has a lightweight (2.4 pounds) and low-profile (9.25 inches) design, and is water resistant. It also features user-adjustable stance stability and a removable battery pack.
The Proprio Foot, launched in 2006 by Ossur Americas, represents the first microprocessor-controlled ankle and foot prosthesis. The prosthesis basically “reads” the terrain and positions itself so that the shin becomes vertical as patients walk, which Romo noted effectually smoothes out patients’ gait, making it more normal. He added that patients report “feeling much more comfortable in the socket.”
The Proprio Foot also is targeted for unlimited community ambulators (K3). The prosthesis currently is recommended only for unilateral transtibial amputees. However, use of the Proprio Foot for bilateral transfemoral amputees and also transfemoral amputees currently is being researched.
The Proprio Foot uses Artificial Intelligence software to help restore function and eliminate inappropriate forces on the knee joint while patients are walking. The Proprio Foot creates more toe clearance in the middle of swing phase, which enables patients to walk more normally and provides increased traction. In addition, the prosthesis offers a chair exit mode that dorsiflexes the foot approximately 5°, which allows patients to shift their body weight forward over the foot more so they can more evenly bear weight as they stand up out of a chair.
Upper extremity prostheses
In 1999, the first upper extremity prosthesis with elbows to incorporate the use of a microprocessor was the Utah ProControl 2 manufactured by Motion Control Inc. Since then, the use of microprocessors in upper extremity prostheses has expanded considerably.
Among the upper extremity prostheses with elbows available in the United States that feature microprocessors are the:
- Utah Arm 3, manufactured by Motion Control
- DynamicArm, manufactured by Otto Bock HealthCare
Utah Arm 3
The Utah Arm 3, the newest version of the arm released by Motion Control in 2004, incorporates two separate microprocessors in the hand and elbow. The microprocessors operate in parallel and simultaneously so the wearer can operate each one with a separate input, said Harold H. Sears, PhD, president of Motion Control Inc.
“The microprocessor has done four really neat things in the Utah Arm,” Sears said. “One, it introduces simultaneous control of elbow and hand, and two, it allows us to use a well-proven (in the ProControl) and easily understood interface program for the prosthetist. Third, it lets us change things really quickly so we can put new features into the arm as time goes on, and lastly, we can give the wears AutoCal, a unique way for the wearer to automatically readjust the hand sensitivity whenever they get tired.”
The Utah Arm 3 uses four different varieties of sensors or inputs to allow prosthetists to fit the prosthesis to a variety of different patients. The sensors plug into the arm, and the prosthetist can set up the software using an interactive Wizard program. Using their laptop typically, prosthetists can make each adjustment to the arm on an individual screen that also will show patient feedback, such as EMG signals and the amount of power the prosthesis is drawing.
“The future is brighter because of microprocessors – not just that you can write new programs but you can think of all kinds of different ways to evolve your products,” Sears said. “The microprocessor makes fast progress possible because it is more powerful and smaller, and another plus is that it is a lot cheaper than building a custom-made circuit board.”
The DynamicArm, released in 2006 by Otto Bock HealthCare, is an electronic elbow prosthesis featuring microprocessor control. One of the unique features of the DynamicArm is that it can be moved without sending a separate unlock signal to the elbow, said Byron Backus, CP, a prosthetist for Otto Bock HealthCare.
“It automatically unlocks and locks when you send a signal to move it, so it takes a less mental energy to use the arm than other electronic arms on the market,” Backus said.
The DynamicArm has a dead lift capacity up to 50 pounds and an active lifting capacity of approximately 10 to 12 pounds depending on the length of the forearm and the terminal device being used. The prosthesis is powered with a lithium ion battery, which Backus noted is different from the nickel cadmium or nickel metal batteries used in most of the electronic arms currently available on the market.
The DynamicArm is programmed with a computer using software. The computer communicates with the prosthesis using Bluetooth wireless technology, enabling the practitioner to program the elbow as well as the wrist rotator and the terminal device at the same time.
“The advantage of the DynamicArm is that we can customize it during the fitting process so if someone finds optimal electrode sites, we can use those electrode sites,” Backus said. “We can control maybe the hand and the wrist with electrodes and control the elbow with a linear transducer, for example. In a case like that, we can have simultaneous control where the patient could feasibly be operating the elbow and the terminal device or the wrist rotator at the same time.”
Upper limb nerve reinnervation
One revolutionary area in upper limb prosthetics under development is the Bionic Arm technology being researched by the Neural Engineering Center for Artificial Limbs at the Rehabilitation Institute of Chicago (RIC). After undergoing a nerve reinnervation procedure pioneered at RIC by Todd Kuiken, MD, PhD, a small number of patients have been fitted with six-motor, microprocessor-controlled upper limb prostheses which are experimental. Those that we refer to as “take home prostheses” incorporate commercially available elbows, wrist rotators and terminal devices, said Robert Lipschutz, CP, a prosthetist with the Neural Engineering Center for Artificial Limbs at RIC.
Patients who undergo the surgery and are fitted with the prosthesis are able to perform two or even three functions simultaneously because they have new muscle sites in the arm itself. The first patient to undergo the procedure, Jessie Sullivan, has even reported being able to sense touch.
“We are starting down the avenue of trying to incorporate something that we refer to as a pattern recognition type control. Instead of using conventional myoelectric control of the past where a single muscle fed a signal to a prosthesis for a particular control motion, we may have 15 or 16 different electrodes on the person’s arm, which gives us much more information to discern for articular controls. This enables us to control multiple limb functions in a virtual environment and, hopefully soon with advanced prosthetic components, in an individual’s prosthesis,” Lipschutz said.
The RIC team is involved with two Defense Advanced Research Projects Agency Revolutionizing Prosthetics Program (DARPA) grants. The team is subcontracted to take some of the information given to it regarding design parameters and provide feedback as clinicians fitting a prosthetic system. For instance, the RIC team provided feedback for the Proto 1 prosthesis being developed by the Johns Hopkins University Applied Physics Laboratory.
In addition, Lipschutz noted the teams involved with the DARPA grants are experimenting with designs of different prosthetic prototypes “fingers have multiple digits to move somewhat independently in order to give different hand grasps; to have different motions at the wrist, not just pronation-supination but also flexion-extension and radial and ulnar deviation; and then as far as the shoulder functions are concerned, to have the ability to have a powered shoulder that will flex and extend, abduct and adduct, and also a humeral rotator that will internally and externally rotate.”
Although only a handful of patients have undergone the nerve reinnervation procedure to date, Lipschutz said the RIC team hopes that by publicizing their success, other patients who are candidates for nerve reinnervation will get involved in similar protocols. The RIC team was hoping to work in conjunction with prosthetists out in the field to have appropriate patients undergo the surgery at RIC, and then help and support a local team in developing and fitting patients with the prosthetic device.
“Unfortunately, between the time that we initially proposed it to now, the funding for the surgery and the prostheses themselves has halted,” Lipschutz told O&P Business News. “We are trying to pursue this on a third-party payer basis to see if the individual’s insurance carrier would be responsible for covering the surgery and the prosthetic devices.”
Electronic stance control orthoses
Although the use of microprocessors in prosthetic devices has become widespread in the past decade, the use of microprocessors in orthotic devices has evolved at a much slower pace. In fact, two versions of electronic stance control orthoses (SCOs) that incorporate microprocessors have virtually come to a standstill – primarily from a lack of reimbursement.
The first electronic SCO, the E-Knee, was launched in January 2003 by Becker Orthopedic. Nearly 5 years after the technology became available, there still are no L-codes to support electronic or microprocessor-controlled SCOs, said Gary Bedard, CO, FAAOP, clinical marketing manager for Becker Orthopedic.
“On the orthotic side, at this point in time, both in the clinical application and manufacturing side, we seem to be at a stalemate,” Bedard said. “Unfortunately, it is frustrating for us because we really hate to use that old cliche catch-22, but we certainly are [in a catch-22 situation].”
Bedard refers to the situation as being catch-22 because the Centers for Medicare and Medicaid Services denied the L-code application for electronic SCOs, citing low numbers as the reason. However, the lack of reimbursement has virtually limited any subsequent sales volume for electronic SCOs. He also noted the lack of L-codes has reduced sales of the E-Knee.
The lack of reimbursement serves as “a detriment to practitioners,” Bedard said. “As soon as they hear that, it is ‘No, I do not have the time to do that. I am not going to go in that direction, and my patient cannot pay for it in cash.’”
Similarly, the lack of reimbursement has prevented a second electronic SCO, the Smart Knee developed by Horton Technology Inc, from progressing beyond a limited clinical trial.
“I think the sad thing is that SCOs have been developed but there is really no incentive to go any further because we cannot get reimbursed,” said Gary Horton, CO, FAAOP, of Horton Technology Inc. “We do prosthetics also here and it is great that the amputees have access to that technology but it is sad that the orthotic patients do not.”
Horton noted the Smart Knee had been perfected but never went into production because of the lack of an L-code. He described the situation as being “the old story of you cannot get credit because you do not have credit.” He added that the interest is there and that he gets asked about the Smart Knee on a weekly basis by practitioners.
“At this point, we have pretty well just stopped,” Horton said. “It is just not financially feasible for us to continue until there is reimbursement available.”
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Mary L. Jerrell, ELS, is a correspondent for O&P Business News.
This story includes a small representative sample of individual companies and products. O&P Business News does not intend to promote individual companies or their products, nor to achieve an industry-wide consensus on the issue. Companies contacted in developing this story were randomly selected. Additional companies were contacted for information but had not responded prior to press time.