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Dynamic Prosthetic Socket Sensor Detects Limb Changes for Best Fit

As an amputee walks on a prosthetic leg during the day, the natural fluid in the leg shifts and the muscles shrink slightly, which poses a problem for the fit of the prosthesis. Sandia National Laboratories researcher Jason Wheeler is working to develop a sensor to tell how a limb changes, along with a system that automatically accommodates those changes. The interface, or socket, between a prosthesis and a limb is custom-made, starting with a cast of the area. The socket follows that contour, and a clinician adjusts it for the best fit. The Sandia researchers invented a three-axis pressure sensor that is incorporated into a liner that slips into the socket of a prosthesis. The sensor can be distributed to measure normal pressure, like pushing a finger on the thigh, and shear pressure in two directions on the skin, like sliding a finger down and across the thigh. Shear forces are important because they cause such problems as rubbing, blisters and abrasions. Other designers have placed pressure sensors in sockets, but those measured only normal pressure.

Topics:
Detectors Implants & Prosthetics Medical Sensors

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    Transcript

    00:00:00 you I've worked on prosthetic devices for many years and we were working on very cool robotic limbs and joints and this technology is very exciting we took it out of the laboratory and took it into the clinic and show amputees and showed prosthetists and they looked at it and they said well this is really cool but my limb really hurts and this was when

    00:00:29 we realized that no matter how cool the device and the technology were if it wasn't comfortable to the person they wouldn't use it when a person has a leg amputated we can replace a lot of that functionality with the prosthetic device and the technology is very good but it still doesn't replicate fully the function of the intact limb and so there's several problems that people

    00:00:48 experienced with the prosthesis the one that we see most commonly is that instead of now the person walking on the bottom of their foot they're putting their weight on tissues that are higher up on their leg and those tissues are not adapted to the kind of loads that they typically experienced like this the sole of the foot would be over time as they walk on the limb the shape of the

    00:01:10 limb and the volume of the limb are not constant and so this is a constant challenge that many amputees deal with is how to manage these shape and volume changes so to address this problem of the changing limb shape and volume that occurs as with most amputees we've developed technology that can monitor the fit of the prosthetic socket over time and in addition to that we've

    00:01:29 placed bladders and other things inside the liner that will allow if we detect a shape change or a fit change we can make accommodations for those changes by filling up these bladders with liquid this is an example of a conventional prosthetic socket it's custom fit to the anatomy of the amputees residual limb typically an amputee would wear a gel liner like this one inside of the socket

    00:01:54 to provide some cushioning this is the conventional technology that's used to improve upon this we've decided instead of integrating our technologies into the socket itself we've integrated it directly into the liner in this case we've integrated sensors at several different locations inside the liner this allows us to monitor the fit to see if it's deviated from what the

    00:02:13 prosthetist intended additionally we've also been able to integrate bladders directly into the liners and this allows us to add fluid in those areas where volumes been lost if we've detected a change in fit what we'd like to go in the future is to partner with companies to produce this technology and larger quantities tests on a broader pool of amputees and

    00:02:35 ultimately to make it accessible as a product in the clinic to amputees into clinicians ultimately we want the dynamic socket to improve the comfort and quality of life of amputees you