When a person with an upper limb amputation uses a prosthesis; there are typically three styles of prostheses to choose from: passive, body-powered, or myoelectric. The goals and abilities of a person with an upper limb amputation will help to determine the style of prosthesis that they receive.
A passive prosthesis has a lower level of function but a high level of cosmesis as it can have a skin-like prosthetic cover and hand to visually simulate the absent limb. A body-powered prosthesis includes a harness over one or both shoulders, attached to cables and requires manual body power to open or close the terminal device of the prosthesis.
The level of functionality, durability and cosmesis will determine the style of the terminal device that the user receives (hand or hook). Prosthetic hooks are less natural looking than a prosthetic hand but can be more durable and have more functionality, with various styles of hooks available.
Lastly, a myoelectric prosthesis “is an externally powered artificial limb that is controlled with the electrical signals generated naturally by your own muscles.” Traditionally this involved one or two muscle sites, located on the residual limb and built into the prosthesis, that are used to control the movement of the terminal device to open, close, or rotate an electric wrist.
Recently, a new myoelectric design called COAPT has become a popular choice allowing for “advanced pattern recognition control technology for powered upper limb prostheses.” “COAPT’s Complete Control pattern recognition technology is a myoelectric control system that gets built into the prosthesis that enables more natural, intuitive control of the arm. It uses modern machine learning techniques to learn your personal muscle patterns and will translates those into prosthesis movements, just the way you intent.”
Multiple electrodes (up to 16) are placed within the socket, which must be calibrated to learn the global movements of the limb. When an individual is first learning the COAPT system, a program displays different grip patterns which are to be replicated by the user. Once the system is calibrated and muscle movements learned; activity within the socket is translated to the terminal device.
The major difference between traditional myoelectric technology, which was first developed in the 1960’s and not adopted until the 1980’s, and the newer COAPT pattern recognition system is how the user thinks when controlling the prosthesis. With the traditional system the user thinks about flexing and relaxing certain muscles (contacting the one or two electrode(s) within the prosthesis) to provide control of a hand and wrist. Whereas with COAPT the user primarily thinks about using their hand and wrist naturally as most people with amputations still experience the sensation of their amputated limb.
Those using COAPT technology have reported that it is a more natural and intuitive way to use their prosthesis compared to the older/traditional myoelectric prostheses. Due to the more natural feeling most also say that less mental effort is required to control the prosthesis.
Although the concept of pattern recognition has been around for many years, this technology has recently become more desired due to the technological advancements of the hardware that it is able to control. There are Myoelectric hands (to be discussed at more length in future blogs) now available that have multiple grips/grasp styles. Those using a multi grip hand with the COAPT pattern recognition control system can physically/mentally change the grip of the hand, providing much more function.
We would like to introduce you to Heather!
Heather was the first Manitoban and only fourth in Canada to incorporate the COAPT control system into her prosthesis. When initially talking with Heather and while testing the system, she immediately thought “Wow. I need this!”
“[COAPT] is a life-changer. I knew this system would change my life and make my life easier. The sensors in the COAPT system has made the difference for me on what worked and what did not (Traditional two site electrodes). I put my arm on and everything was easier to move. Tasks that are important to me are easier: putting on makeup, tying my shoes, and cooking. A simple thing like holding onto a hand rail now becomes easy and second nature. I love it.”
At WinPO, we work together to plan and determine an individualized treatment plan that is unique to each person. Do not hesitate to reach out to us if you have any questions about your current or future prosthetic needs.