O&P technology has become more global in scope, with many design and fabrication innovations coming from abroad. Different approaches to regulation, funding and health care can help push new devices and clinical advancements through the pipeline more quickly than in the United States. O&P Business News looks at just a few of these fast-growing innovations from both industry and academia, and their potential paths to US shores.

Aqualeg

Frederic Rauch, inventor of the Aqualeg, is a transfemoral amputee. He told O&P Business News that, although he has first-hand experience with the technological evolution in O&P, he “always wondered why, 40 years after walking on the moon, it was still impossible for me to walk with my everyday prosthesis along a beach with feet in the water.”

He got the idea for a water-friendly, everyday prosthesis while working as a business manager at an automotive company in France. With input from some engineering coworkers, Rauch created a silicone fabrication process by which he crafted a realistic-looking, durable, hollow prosthetic cover, suitable for swimming and for everyday use.

 

In 2011, his design was awarded with the National Innovation Prize from the French Ministry of Research and Sciences “despite the fact that I was not a scientist and that the concept seemed completely opposite of all other companies’ strategies,” Rauch said. “When I got it, they asked me to create a company and they said the government would support the company. A lot of big industries in France wanted to help us.”

The prosthetic cover, which accommodates non-electronic components, has a simple appearance but is technologically advanced, Rauch said. A patient’s prosthetist takes photos of the patient’s leg and prosthesis. Three-dimensional computer fabrication methods create a customized silicone cover, which the prosthetist fits over the prosthesis; the end result looks like one product.

“The process allows us, in an almost industrial way, to fabricate silicone, which has a very realistic appearance,” Rauch said.

The foamless cover is supportive and keeps its shape, Rauch said, and was designed with function in mind, rather than appearance.

“We just wanted to make it discreet for the amputee, nothing more,” he said.

 

 

But it has turned into something more for Rauch and his company; in fact, the prosthetic cover opened the door to the idea of making an everyday hybrid prosthesis able to go everywhere, including water. As opposed to a water-resistant design or a swim leg, the prosthesis allows water to run through it via an outlet in the foot.

“This is what is new. I had to convince some manufacturers to guarantee some of their components for saltwater. Otto Bock and Freedom Innovations actually guarantee some of their products for this,” he said. “This realistic and customized product …is now accepted and on the way to being considered as a potential standard.”

Rauch’s company holds workshops for prosthetists and makes recommendations on ways to fabricate a prosthesis for both walking and swimming, even if they do not purchase the Aqualeg. Rauch said several patients who have been some of the first to wear the Aqualeg prosthesis have offered to actively participate in the development of the company, gratis. For some, that may mean relocating to the United States: Aqualeg has opened a brand new facility in Rock Hill, S.C. The primary product provided there will be the Aqualeg cover, but the French facility, located in Nantes, is focusing more on developing the Aqualeg prosthesis and making recommendations to prosthetists regarding which components to use.

“We need to tell them which kind of foot, which kind of adapter, which kind of accessories. They ask us to help them choose the best one, so that’s why we’re going to sell more complete prostheses.”

 

He expects up to five employees will work at the facility stateside; currently, the French company has seven employees but Rauch is expecting that number to double next year.

Robotic hands

As the demand for the incorporation of robotic technology into prosthetic devices continues to rise, cost and usability are important factors to consider. Researchers at the Research Center “E. Piaggio” at the University of Pisa and the Italian Institute of Technology in Genoa have created a robotic hand using durable plastic and minimal electromechanic hardware.

“The Pisa-IIT SoftHand was built with a different design philosophy than most other robotic hands,” Antonio Bicchi, PhD, a professor at the University of Pisa and senior scientist at the Italian Institute of Technology, told O&P Business News. “While many hands add more actuators, or motors, to add function and more closely approximate the functions and capabilities of the human hand, the SoftHand exploits the principles of underactuation.”

According to Bicchi, the number of degrees of freedom in a robotic hand is typically equal to the degrees of actuation. However, the SoftHand uses fewer actuators than degrees of freedom.

 

“The number of actuators is smaller than the number of degrees of freedom, providing cost savings and allowing certain freedoms,” Bicchi said. “We combine this technique with the concept of synergies from human hand movement science to simplify the complexity of hand movements.”

The concept of synergies is grounded in neuroscience. The brain is thought to simplify the coordination of a large number of joints into distinct movement patterns, and all of the joint movements in the hand can be condensed to essential components. According to Bicchi, the first synergy comprises more than half of the variability in typical hand movements used for grasping common objects, and a single motor can be used to reproduce the necessary grasp patterns.

“When this is combined with the built-in flexibility of the movements of the SoftHand, we can approximate a large number of grasps with the thumb in palmar abduction or opposition,” Bicchi said.

The SoftHand utilizes a tendon-driven design. The tendon is made from a high-strength, durable polyethylene fiber (Dyneema, DSM), and is run through the joints of the fingers by a pulley system. As the motor is activated, the tendon is pulled and the fingers first adduct and then flex in one fluid motion. In preliminary laboratory tests, the SoftHand was used by subjects to successfully pick up 107 different objects, including a screwdriver, AA battery, credit card and eyeglasses.

“Because the hand incorporates synergies, the joints move following the pattern of the first synergy,” Bicchi said. “The key innovation is a built-in flexibility to the grasp pattern allowing the hand to mold around grasped objects instead of providing a rigid grasp.”

Most of the joints in the fingers are rolling contact joints, which are made of two cylinders that roll against each other as the finger bends.

“The two cylinders are held together by the tendon and elastic bands, thus when they collide with something, they can bend in virtually any direction to ‘get out of the way’ and then snap back to their original position,” Bicchi said. “We’ve also incorporated a few teeth, like on a gear, to increase stability.”

 

The design, material and fabrication of the SoftHand all enable its affordable cost.

“The current SoftHand is predominantly made of plastic, which saves money, as well as on weight,” Bicchi said. “The parts also lend themselves to 3-D printing technology, at least at the small scale of manufacturing prototypes, and to very economic large-scale production by injection.”

The current SoftHand prototype was designed for application in robotics, but Bicchi has plans to adapt this technology for use by upper extremity amputees.

“We are currently in the preliminary stages and are exploring several avenues to move forward,” Bicchi said. “We have established myoelectric control of the hand using two electromyography signals that are driving both the position of the hand and the stiffness to produce more stable and flexible grasps.”

 

Bicchi is currently working with Sasha Blue Godfrey, PhD, who is supervising the prosthetic applications of the SoftHand, and Marco Santello, PhD, a professor at Arizona State University, to test the myoelectric control of the SoftHand and bring this technology to the United States. They hope to begin clinical testing with amputees in the near future.

Osseointegration

Direct fixation of a prosthetic device via osseointegration is considered to be a viable and effective solution for transfemoral amputees who cannot use traditional sockets because of skin infections, a short residual limb, soft tissue scarring and volume fluctuation in the residual limb, among others. Osseointegration also can alleviate common complications caused by sockets, such as muscle atrophy, pressure sores, skin breakdown and residual limb pain, as well as improve limb control and mobility.

Research groups in Sweden, Germany and the United Kingdom have performed osseointegration procedures on more than 100 patients, including a transhumeral amputee in the United Kingdom, and have experienced success with the process. Osseointegration also can increase the risk for infection, stress shielding and bone loss or fracture, which could lead to revisionary surgeries in severe cases, but researchers in The Netherlands are currently examining how to mitigate these risks.

“The currently used first generation of osseointegrated implants for direct fixation of external leg prostheses is based on a stiff metallic intramedullary implant and presents limitations in terms of minimum implant length, which excludes implantations in patients with short residual stumps. This group of patients has also severe difficulties in using conventional socket prosthesis due to a short stump,” Pawel Tomaszewski, PhD, from the Orthopaedic Research Laboratory in the Department of Orthopaedics at Radboud University Nijmegen Medical, the Netherlands, told O&P Business News. “Additionally, stiff metal implants induce stress shielding leading to periprosthetic bone loss and compromised bone stock in the case of revision surgery.”

To mitigate these risks, Tomaszewski and his colleagues have been working with researchers at the University Medical Center Groningen in the Netherlands to improve the metal implants used in osseointegration procedures.

“The new implant is composed of a collared metal pin sliding in an elastic cylinder fixed inside the bone by means of osseointegration,” Tomaszewski said. “This allows physiological load transfer from the external prosthesis to the skeletal system and considerably reduces risk of bone overload and damage.”

 

A standard titanium implant and the new direct fixation implant were tested experimentally and with finite element (FE) simulation on seven cadaver femur bones aged 70 years to 96 years. Finite Element models of an intact femoral bone and amputated bones fitted with both implants were also created.

The researchers found there was a reduction in stress shielding especially for heel strike at the distal and middle level and for one-leg stance at the middle level. The FE predictions also demonstrated similar patterns as those recorded in the experiment.

“In this study, we showed both in experiments and numerical simulations that the new implant considerably reduces stress shielding in the bone,” Tomaszewski said. “And this will prevent adverse bone remodeling and bone loss in the long term.”

The researchers also found the new implant could be used on shorter residual limbs than typically recommended.

“According to our results, it is possible to use implants of 8 cm without generation of high stress peaks in the bone which is the case with metal implants,” Tomaszewski said. “The new type of implant can be used for intramedullary fixation of amputation prostheses, as well as for fixation of other types of implants, such as tumor prostheses or hip and knee joint replacements.”

The implant is still in the early stages of development, and Tomaszewski and his colleagues are currently looking for commercial partners to continue their research.

Although osseointegrated implants have not yet been used on human patients in the United States, the Food and Drug Administration has approved a feasibility trial that will be conducted by researchers at the University of Utah and is expected to begin this summer.

Suspension systems

Over the past several years researchers have been looking to improve suspension systems for amputees. Össur has attempted to address daily volume fluctuations of the residual limb, skin sensitivity and enhanced flexibility for range of motion and comfort with the Iceross Seal-In V liner for transtibial amputees. Otto Bock also introduced the Anatomic 3D PUR Liner in an attempt to solve liner slippage due to increased skin moisture, as well as a new Shuttle Lock that will help amputees with dexterity or vision problems.

Arezoo Eshraghi, MSc, a PhD research fellow and part-time lecturer at the Center for Applied Biomechanics, department of biomedical engineering at the University of Malaya, Malaysia, and colleagues developed a magnetic prosthetic suspension system (MPSS), a mechanical system for lower limb prostheses, and compared it with a pin/lock and suction suspension systems in two studies. The researchers also analyzed the interface pressure and vertical movement between the socket and liner.

According to Eshraghi, with acceptable pistoning and interface pressure distribution, the MPSS system proved to successfully suspend lower limb prostheses, while higher interface pressure with the suction suspension systems was associated with less pistoning and improved suspension. However, for amputees to accept the suspension system as a long-term option, the qualities of interface pressure and suspension should be to the user’s satisfaction, Eshraghi told O&P Business News. The MPSS achieved higher satisfaction rates among amputees in donning and doffing, walking, uneven walking, stair negotiation and overall satisfaction.

“The current suspension systems have some pros and cons,” Eshraghi said. “Our quantitative and qualitative studies show that there should be a balance between the suspension quality and user satisfaction; otherwise the prosthetic users would be skeptical over the system. The perspiration problem within the prosthetic socket and at the skin-liner interface has yet to be fully addressed.”

Magnus Lilja, CPO, PhD, director of Össur Academy and Clinical Specialists at Össur Nordic, said more studies should focus on the impact of different vacuum systems and hypobaric seals on circulation and on wound healing.

“Some studies have been published, but I think we need more, because this can show that prosthetic fitting and mobilization can be a big part of the wound healing and early rehab even with delayed healing,” Lilja told O&P Business News.

He also said manufacturers can improve suspension systems by making donning and doffing easier, as well as giving the user a more secure feeling that the prosthesis will not fall off.

“I’m glad to see that during the last 20 years we have seen a major improvement in suspension. Today the skeletal movements inside the prosthetic sockets have been reduced to a minimum when using the hypobaric seal or good cushion systems,” Lilja said. “However, I have big concerns that there are still some prosthetists using the old PTB system with a supracondylar strap. This is not a modern system and should only be in old textbooks. Several studies show that this is a terrible suspension technique with severe skeletal movements inside the socket and we as prosthetists should find other suspension systems 
instead.” — by Carey Cowles, Megan Gilbride and Casey Murphy

 

Disclosure: Bicci’s research was funded by grants FP7- ICT-2009-4-2-1-248587 and ERC-291166 from the European Union. Eshraghi and colleagues received the Malaysia UM/MOHE HIR grant (no. D000014-16001). Lilja has no relevant financial disclosures. Rauch is the developer and owner of Aqualeg. Tomaszewski’s research was supported by a grant from Fonds NutsOhra.