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From ActiveLivingMagazine.com From the Field
What are we to believe? “It’s all a matter of fit,” says prosthetic wizard Dieter Bochmann, director of the Canadian Center for Prosthetics. An artisan who has been custom-fitting prostheses for more than forty years, Bochmann is a great believer in the importance of ‘feel’ – the amputee’s and his own. “Getting the right fit, the perfect fit, it is all about feel,” he explains. “To make a socket, of course, you first have to make the model. I use plaster to create a negative impression of the residual limb and then create a positive plaster model that exactly matches it. From that, I make the socket mold. Some people use a computer to create the negative and positive molds – I don’t think it really matters. It’s the fitting process that I think really needs to be done by hand.” It’s a time-consuming, exacting pro-cess. “At the very first fitting, I ask the amputee to tell me exactly how the socket model feels on their limb. Is it too tight anywhere? Is it too loose? Then I adjust to make sure that the fit is just right.” Sometimes, if there seems to be too many adjustments required, Bochmann will simply start again with an entirely new model. “You don’t want something that re-quires too many adjustments in order to make it comfortable – that’s just not a good fit.” When Bochmann first began fitting prostheses in Germany in the late 1950s, the materials used were either wood or metal or a combination of the two. One of the greatest changes he’s witnessed over his more than four decades in the business is the improvement in materials available. “In those early days, we used wood and metal – they were heavy and much bulkier than the prostheses we make today. We could achieve a nice smooth surface that was as comfortable as any of the modern materials, but we just didn’t have the electronic componentry, the carbon fiber feet, the knee modules and the interface materials such as resins and silicones that make modern prostheses so great.” A good prosthesis should be able to handle all the stress and strain that an amputee cares to give it. A person who was a competitive athlete before an amputation should be able to be as aggressive with his prosthesis as he was without it. An amputee who operates a hobby farm should be able to count on his prosthetic arms to allow him to do the barn chores he’s always done – without the discomfort of shearing or chafing from a poorly fitted prosthesis. Comfort depends on a number of factors, as does the length of time a new amputee can expect to pass be-fore he or she feels physically at home with the prosthesis. The most important factors affecting the settling-in period are the age of the wearer, that person’s overall health, the level of the amputation (whether or not a joint is involved), and the individual’s personality before and after the surgery. Generally speaking, the younger you are, the more quickly you will adjust to your prosthesis. To facilitate the adjustment process, the emphasis is on early involvement with the prosthetist. Clients meet with Bochmann at all stages of the process and he works with their doctors and physiotherapists to ensure that the amputee is progressing as he or she should. Jeff Green, Manager of Technology Services and Training for Southern Prosthetic Supply, a division of Hang-er Prosthetics, is also a believer in the importance of early and on-going amputee care and prosthetist involvement, but unlike Bochmann, he is a great proponent of CAD technology for prosthetic design. “As with any prosthetic design process, you have to begin by creating a plaster mold. What makes CAD design different is what happens to that mold next. The mold is placed in a machine which holds it in place by means of small ‘arms’ on a large turn-table. As the mold rotates, a tiny, highly sensitive wheel moves down into the center of the plaster cast and traces the inner surface. The information the wheel gathers is transmitted to a computer screen where an exact reproduction of that inner surface is created. Next, a computer-aided carving tool shapes a large piece of dense foam into a positive image of the amputee’s residual limb. That positive mold is then used to create a ‘test socket’.” The wearer is fitted with the test socket and any necessary modifications are made to ensure a comfortable fit – modifications that are done by hand using the same techniques used by the non-computer aided prosthetists. “The great advantage of the CAD process,” explains Green, “is the time saved. Creating the negative mold using the computer takes a matter of 45 minutes, whereas making one by hand could take three to three and a half hours.” Most clients can expect the process of being fitted with a final prosthesis, custom designed to fit the demands of their particular residual limb, to take approximately four to five weeks, whether they choose to go the craft or computer route. And will the fit be absolutely perfect in either case? Probably not – at least not every day, says long-time prostheses wearer, Jeff Tiessen. “The thing you have to remember is that your residual limb will change its shape from day to day and season to season depending on the temperature. When the weather’s hot, your limb will swell. When it’s cold, it will shrink and that will change the way your prosthesis fits. And you’ll find that your level of activity will also have a bearing on the way your socket feels. If you’ve been particularly active, you may find that things rub a bit. That’s where silicon gel-filled socks come in handy. They cushion the friction areas.” So what’s the answer? Does CAD design create the better socket or should we stick with the good old-fashioned hand-crafted approach? We can’t say, but we can offer this important piece of advice: whatever technology your prosthetist chooses, the most important aspect of the process is his or her dedication to your comfort. Find the professional who will put your comfort first. © Copyright 2004 Active Living Magazine |
