I agree with your assertions. I got the price target from talking to a couple of prosthetists. They work independently as contractors to hospitals/healthcare provider groups, rather than being part of a hospital/or healthcare organization. I'd guess a real prototype will cost on the order of $75k U.S. but I don't see a way to push the price down to where I was told a fellow might actually afford such a device. After all, it's only applicable to subset of the cases that the prosthetist has to handle, and, in fact, only to a subset of those. As a result, the apparatus must not only be reasonably priced, but also reasonable in size.



Well, this is just another proof-of-concept challenge, though it's mostly mechanical rather than being mostly electronic. The problem that I'm addressing at the moment is the definition of the problem, as nobody seems to know what the relative importance of such things as tissue density and distance to the bony structures is. They do agree that they are important, though. In the past, the problem was addressed as a whole, simply by taking a cast of the amputation stump and noting the location of the bony protuberances and major structures. In this approach, some importance has to be assigned to the relative locations of hard vs. soft tissue.

Over time, the technology associated with fitting prosthetic devices of the type that specifically interests me has been focused on fir, suspension, and alignment of the prosthetic limb. Much effort and technology has been devoted to the development of energy-storing types of feet. Collaboration between surgeons and prosthetists has reduced the business of fitting below-knee prostheses to a process of assembling off-the-shelf components, together with casting and applying an individualized socket, in which most of the weight is borne on the amputee's patellar tendon, much as it is on a normal leg. Most often, a somewhat flexible liner, somewhat reminiscent of a condom, is rolled onto the stump. This liner has a step-pilot on it, one that fits into a socket built into the portion just below the socket for the stump, and that aids in holding the stump in position, therefore suspending the prosthesis from that liner. Additionally, an external sleeve is applied to the entire assembly, restricting the airflow between the socket and the liner, which then forms a pneumatic suspension. Unfortunately, the most popular form of liner allows the suspension to yield in the vertical plane, thereby allowing a bit of "pistoning" which, in those cases, such as my own, where there may be one or more bony protuberances, tjat cam caise problems as the upper and lower surfaces corresponding with those protuberances alternative take pressure.

The fit is VERY critical, and, with current technology, is possible to accommodate thanks to cooperation between surgeon and prosthetist. However, in cases, such as my own, a traumatic amputation, the surgery was done with an emphasis on restoring the knee to full operation at the expense of neat and clean arrangement of the bones. The fit of my prostheses has been complicated by the resulting protuberance, and by the rather odd swelling that I still experience.

Prosthetists keep quite an array of components in stock, which means they have to invest a considerable amount in those components, hence, as individual businessmen, they are unable to invest many thousands of dollars in equipment that is applicable to only one type of prosthetic application. Oddly enough, the problem of fit is much better addressed today than it was ~30 years ago when I had my second amputation. The problem I'm trying to address is the fit, which is probably the most straightforward portion of the problem. This is the most costly portion, too, because it requires considerable labor and all the involved components are lost if the fit is unsuccessful. The suspension is the aspect of the task that is most critical to my own comfort, but there's a simple solution to that, and it's also bsed on fit, as the off-the-shelf liners popular today don't work on many traumatic amputation patients, such as I am.

I've spent lots of money on prostheses, as has the Veterans' Administration, yet I've had few really successfully fitted limbs, due to the way in which the job is done. I'm thinking that automating the fit of stump and socket will reduce the labor cost and material waste that often occurs in this process. Unfortunately, it has to be done inexpensively, because the individual prosthetist won't be able to invest a large amount in an apparatus that deals with something in which he's already invested a considerable amount.

The technology now exists by which, under computer control, a positive model of the stump with computer-edited modifications to accommodate differences in tissue texture, both the socket and the liner can be made with great precision and without ad-hoc application of experienc/black-magic. This has never been done, so far. With 3-D printers capable of producing a positive model without the error inherent in making a negative model (cast) and transferring/altering it in order to make a positive model on which the socket and liner can be based, I'm convinced that the process can be vastly refined.

RE