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High-Fidelity Interface touted as the closest thing to osseointergration without the surgery.
THOUSAND OAKS, Calif. - biodesigns inc., a company specializing in the most biomechanically advanced upper and lower limb prosthetic systems, is introducing a revolutionary socket - the High-Fidelity Interface - to improve the comfort and functionality for persons with limb loss. The patent-pending design was developed by biodesigns' CEO and chief prosthetist, Randall Alley.
Alley explains that the High-Fidelity Interface was developed in response to patients' complaints that their socket is not fitting snugly or comfortably, resulting in poor positional, operational, and functional control. "A person can have the most technologically advanced prosthetic foot, knee, hand, or arm, but if it doesn't connect to or 'interface with' the body properly, it won't deliver the performance it should and the individual is less likely to wear it and enjoy all the benefits it is intended to deliver," he said.
The High-Fidelity Interface for both upper and lower limb applications offers a radical departure from the traditional model in that it imparts a high level of intrinsic bone control. "The term High-Fidelity refers to the precision with which the interface captures and reproduces skeletal motion," Alley said.
"The High-Fidelity Interface addresses wearers' desire to have a more efficient, better performing and more comfortable socket. In fact, we don't even consider it a socket. The technique mimics many of the benefits of osseointegration (where the connector to the prosthesis is embedded in the bone) - without the surgery," he said. "In our patients' own words, the design not only makes it seem that it feels more like a part of their body, but the perceived weight of the prosthesis is also significantly less."
Feedback
"I've been an amputee for 35 years, and I am very, very particular about the fit and finish of the socket. In fact, when I was asked to try Randy's new interface socket, I thought, okay, I'll agree to have him mold his new and improved, whiz-bang socket?and then I will show him why it won't work on a VERY active amputee. Now when I see Randy, I can hardly talk to him because my mouth is so full of black feathers from eating crow," said Ron Currier, a retired chief of prosthetics at the Manchester, N.H., Department of Veterans Affairs (VA) Medical Center.
"In this new technology, there's no more slushy skin. I have more freedom of movement and more stability and better control of the arm," said Chuck Hildreth, Gifford, N. H. who has a left short humeral and right interscapulothoracic amputation.
Both Currier and Hildreth are participating in a clinical study involving the "Luke Arm" developed by famed inventor Dean Kamen's DEKA Research and Development, Manchester, N. H., and the High-Fidelity Interface with DEKA enhancements, as part of the Defense Advanced Research Projects Agency (DARPA) Revolutionizing Prosthetics program.
High-Fidelity Interface vs. traditional socket design
Alley explains that in traditional socket designs, a patient's soft tissue is simply encapsulated or surrounded by the socket, restricting the amount of control the socket can impart upon the bone buried beneath the soft tissue. He compared it to trying to control the motion of a metal cylinder (the intrinsic bone) within a fluid-filled balloon (soft tissue and associated fluids) by merely wrapping your arms around it.
"This soft tissue 'barrier' allows significant skeletal motion within the interface prior to the interface responding, and hence the prosthesis partially absorbs rather than captures and efficiently transferring this motion. This inner skeletal motion decreases prosthesis stability, the wearer's positional precision, functional range of motion and overall efficiency of movement, thus increasing energy expenditure while concurrently increasing the perceived weight of the prosthesis," he said.
An alternating combination of precise compression coupled with release of tissue is design key
In contrast, the High-Fidelity Interface provides a high level of bone control by optimizing soft tissue flow and applying local and focused compression on the soft tissue overlying the intrinsic bone.
This skeletal stabilization is accomplished by using a series of alternating soft tissue compression and release areas oriented carefully along the long axis of the intrinsic or target bone. A specialized sensor can be used to ensure adequate blood flow at the interfacial boundary where compression occurs.
"In between these longitudinal areas of compression that travel nearly the entire length of the bone are areas or windows - depending on whether the interface is a solid body or an open cage-style interface - where soft tissue can flow out of the way or out of the interface entirely. This allows increased compression on the intrinsic bone, far greater than can be achieved in a traditional hydrostatic (uniform pressure distribution) socket," he said.
He emphasized the compression must be very precise. "That is why I have applied for a patent and why I often employ a blood perfusion sensor to ensure a safe compression level," he said. "Above a certain level, you lose adequate blood flow; below a certain level, you minimize the benefits."
The chief benefits to the patients are increased prosthesis stability and more energy efficiency as the interface preserves motion rather than absorbing it so that more of the wearer's input is converted to prosthetic output. In its most radical version, the exposed skin also eliminates the problem of heat and moisture dissipation, a problem with encapsulated sockets when over the course of a day trapped moisture and heat causes the socket to get hot, sweaty, and slippery.
The High-Fidelity Interface can be used for prostheses in upper and lower limb applications alike, with any control system including myoelectric, body-powered, or hybrid, and with any type of suspension system, from self-suspending to auxiliary suspension to negative pressure and elevated vacuum.
High-Fidelity Interface utilized in advanced research projects
Alley is working closely with Matt Albuquerque, Vice President of Next Step O&P, Manchester, N.H., on the DEKA/DARPA project. "Matt instantly recognized the benefits of the High-Fidelity Interface and it has been a real joy to work beside him refining this design for our DEKA test pilots and mutual patients we have consulted together on" Alley said. Albuquerque noticed the immense change this design had on Hildreth: "It was heartwarming to see a patient go from rarely wearing a prosthesis because it was uncomfortable and didn't give him the functionality he desired to now not wanting to leave home without it and wearing it all day. The High-Fidelity Interface is going to have an incredible impact on the way we fit prosthetics from now on," he said.
Currently biodesigns is licensing this technology to a select number of prosthetic offices. "I will be holding certification courses for the High-Fidelity Interface in the near future and we are currently collecting names of those prosthetists and therapists who are interested in learning this design," Alley said.
Alley is also working with T. Walley Williams of Liberating Technologies, Inc. and Matt Garibaldi of UCSF (University of California San Francisco) on a jig for lower limb applications that will assist in ensuring a more standardized approach and hence quality control for creating an interface in the weight-bearing environment, which has its own requirements and challenges. "We are very pleased with the initial prototype casting jig and will soon be instrumenting it for interfacing with a computer. In this way we will be able to discern more information during the initial impression taking about the limb under weight-bearing and compression that will help us refine the design even further," states Alley. "It is our hope that we gain IRB (Institutional Review Board) approval to initiate a formal clinical study at UCSF that will undertake analysis of energy efficiency, gait quality, including stride length, speed and positional control, perceived prosthesis weight and other factors that will provide some additional answers regarding the benefits of the High-Fidelity Interface."
About Randall Alley
Randall Alley, CP, LP is the creator of the High-Fidelity Interface, the XFrame and ACCI (Anatomically Contoured and Controlled Interface), three prosthetic interface designs that brought superior biomechanical principles to the O&P field. Alley has contributed to five prosthetic textbooks, is a clinical columnist, international speaker, and received a Certificate of Appreciation from the Department of the Army for his upper limb training of military personnel. Alley received both his bachelor of science in kinesiology and his prosthetic certificate from UCLA, and is a licensed and board certified prosthetist.
About biodesigns inc.
Southern California-based biodesigns inc. is a technology-driven prosthetics company specializing in the most advanced upper and lower limb prosthetic solutions.. The company's proprietary approach utilizes high tech laser scanners, innovative clinical techniques, and the most biomechanically advanced prosthetic interfaces (sockets) available.. biodesigns works with all levels of upper and lower limb patients, but especially caters to highly active individuals who demand more from their prostheses. For more information, visit www.biodesigns.com.
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