Innovations in Prosthesis

Every year, approximately 185,000 amputations are performed in the United States because of vascular diseases (induced by diabetes or peripheral artery diseases), cancer, or traumatic injuries. Frost & Sullivan has studied the prosthetics market, and presents a snapshot of innovations in the prosthesis space. 

The Amputee Coalition, a U.S. nonprofit organization dedicated to education, support and advocacy of issues related to amputation, estimates that more than 2 million Americans are living with limb loss. Every year, approximately 185,000 amputations are performed in the United States because of vascular diseases (induced by diabetes or peripheral artery diseases), cancer, or traumatic injuries. Of these, traumatic injuries stand out not just because of their prevalence (45% of all amputations are due to traumatic injuries) but also because they happen without warning. 

The term “prosthesis” conjures up images of orthopedic fixtures—artificial hands, metallic joints, or even blades popularized by Paralympic sprinters. While this is accurate, innovations in this space have shifted the reality considerably and have relegated these products to the category of “first-generation.” Frost & Sullivan has studied the prosthetics market, and presents a snapshot of innovations in the prosthesis space. 

Composite Materials: The Need for Lightweighting, Aesthetics and Stability

Prosthetics manufacturers constantly wrestle with keeping devices light and aesthetically appealing without compromising tensile and yield strength, fatigue and corrosion resistance, elastic modulus and overall mechanical stability. Lightweight metals such as titanium and aluminum have replaced much of the steel in pylons, which form the skeleton of a prosthetic device. In-demand carbon-fiber composites have made their impact in this industry as well. 

Carbon fiber is gaining prominence with the increasing demand for flexibility and agility in prosthetic feet. The material was popularized in the Flex-Foot Cheetah design, invented by bioengineer Van Philips. Philips, himself a below-the-knee amputee, tested hundreds of models and materials before settling on using carbon graphite in a design inspired by the hind legs of a cheetah. When the wearer applies weight to the heel of this L-shaped prosthetic foot, the design effectively converts the weight into energy, giving rise to a spring-like action. This design was sold to Össur, a global prosthetics company based in Reykjavik, Iceland, and now forms the platform on which several of its products are built. 

Some of the latest design innovations in the market involve encasing pylons with a special foam-like material to give the prosthesis a skin-like appearance, with the option to color-match it to the wearer’s skin tone.

Impact of 3-D Printing: Fits Like a Glove

Humanitarian aid organizations estimate that more than 80,000 people are in the need of prosthetic and orthotic devices in war-affected Syria. It is easy to understand that one size and one design will not fit all adult and child amputees. Additive manufacturing, popularly known as 3-D printing, can produce computer-modeled devices and parts with minimal defects and in configurations and dimensions that are difficult to achieve through conventional manufacturing practices. Custom-designed airway stents, artificial skin grafts and even blood vessels have been 3-D printed, improving the lives of thousands. In the prosthesis space, 3-D printing is expected to be an important tool to address unique patient needs and unpredictable demand. A custom-fit prosthetic device offers myriad benefits, not the least of which is patient comfort and improved functionality. 

In March 2017, the BBC carried a remarkable story of a Welsh engineer who designed a functional arm for his infant son. The baby’s arm had to be amputated because of a blood clot just days after birth. The man, unwilling to wait several months for a prosthetic arm that would be purely cosmetic rather than functional, teamed up with an open innovation lab at Bangor University to design a hydraulic arm for the young patient based on 3-D scans from an Xbox. This quick-fix, do-it-yourself action resulted in a model that was printed using a state-of-the-art printer from Stratasys (Eden Prairie, Minn.). With this, a new company was born: Ambionics is dedicated to providing functional prostheses for children and understands that a device needs to change as a child grows.

Myoelectric Prostheses: More Sensitivity, Better Functionality

Although they provide mobility and physical support, conventional orthopedic prostheses do not restore full limb functionality and cannot sense or communicate heat, pressure or other stimuli. Several companies are trying to change this.

Myoelectric prostheses have sensors that are placed along the surface of the device to act as sensory interfaces. The sensors pick up electrical signals from the body’s neuromuscular system and translate them into active movement of an electric-powered prosthetic hand, wrist or elbow, allowing an amputee to perform nimble functions such as tying shoelaces or gripping a glass. Touch Bionics’ (Livingston, United Kingdom) i-limb ultra offers a wide selection of automated grips and gestures to complete daily tasks, such as index point for typing and precision pinch mode for gripping small objects. Ottobock (‎Duderstadt, Germany) has included myoelectric capabilities in its Michelangelo, MyoFacil, SensorHand Speed and VariPlus Speed hand prostheses so they can flex, grip and perform delicate motor functions.

The Road Ahead

The barrier between patients and their prostheses continues to be dismantled because of advances that are increasing the integration of devices into the neurological system. The ultimate prosthetic limb would be mind-controlled and perhaps even able to subconsciously twitch. 

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