The first step in getting a new leg is to be evaluated by your doctor, given a prescription for a prosthesis, then make an appointment with a Prosthetist.
Your prosthetist will need to provide you with a temporary socket to go over your limb. This is used to give your new leg a "test run" so to speak.
Your Prosthetist will first take a cast of your residual limb and hand it off to his or her technician, we technicians fill it with plaster to form a "positive" mold. From that a diagnostic socket (or check socket) is formed from a clear PETG plastic that we bake in an infra-red oven. In the industry this plastic is also commonly called Vivak.
Your practitioner can then use this to test fit a socket to your residual limb. They can also attach components to allow you to stand and walk in it, the plastic's clarity and low melting point allow your practitioner to see where you're feeling pressure and use a torch or heat gun (not while you're wearing it of course) to gently soften the plastic and relieve the areas of pressure. Foam padding can also be added to the interior of this socket if needed.
At the time you have your residual limb cast the practitioner will discuss with you what methods to use in holding you in your new leg.
These methods are typically:
Suction: A one way expulsion valve installed into your socket allows air to be pushed out when inserting your limb, but does not let air back in and holds you in place.
Vacuum: Similar to suction but a pump of some sort sucks air out while you wear your leg creating a negative atmosphere holding you in your socket. This pump can be a piston style device that continuously draws atmosphere as you walk/step and substitutes your pylon (the pipe that makes your leg longer). The vacuum can also be provided by an electronic, removable pump if so desired.
Pin System: You wear a silicone liner over your residual limb which has a serrated pin at the distal (bottom) end that clicks into a lock bolted into the bottom of your socket.
The method chosen will decide what, if any, modifications will need to be made to your positive mold prior to pulling plastic, to make your diagnostic socket. Once the best fit is attained, the socket returns to the lab to begin making your definitive!
After the socket is finished your prosthetist or their technicians will attach the necessary components to complete your leg. These components will be pyramids and various adapters for those pyramids, pylons (pipes made of titanium or aluminum) to make your leg long enough, any vacuum or pin systems to hold you in your leg, a foot that suits your activity level to afford you the best quality of life, and a foot shell for cosmetic aesthetics and to fill the inner space of a shoe.
The following pictures show a rough breakdown of the assembly including a foot shell.
There are many components available, much more than I'm showing. Each selection is chosen on a case by case basis, this field is truly all about custom work. Good O&P practitioners really try to go above and beyond to help their patients and don't quit until you are comfortable. Amputees and their practitioners should form a good working relationship, we strive to earn patients for life and we technicians see work for the same patients cross our paths constantly. This is great because while we techs don't always get introduced to the patients, we get the satisfaction of knowing our patients trust us to return for care and they're satisfied with the work that we do.
Being a patient loyal to a practitioner is vastly different from being a patient of a family doctor. Amputees will see their prosthetist twice a year at the least. Some patients see their prostheitst a few times a week if they are a new amputee, or if their bodies change in a way that doesn't allow them to fit into their socket (think weight gain, loss, or discomfort), and of course malfunctions.
It's a lot like having a mechanic you keep going back to because you really like them and you know does good honest work.
A prosthetic leg contains three basic components: the socket (the interface between the limb and the rest of the prosthesis), the pylon, and an artificial foot. The most important part is the socket, which needs to be fit individually to each patient. If the socket is not fitted properly, it is uncomfortable and causes sores and inflammation at the points of contact. Over time, residual limbs change in shape and volume due to swelling and atrophy, which is usually a natural processes like healing or a child’s growth. It is expected that one person could need 15 to 20 devices in his or her lifetime (5).
Zettl JH, Van Zandt ML, Gardner J: The immediate postsurgical adjustable pylon prosthesis for the hip-disarticulation and short-above-knee amputee.
We have developed the RightFit prosthesis, a low-cost, modular, and easily adjustable prosthetic device. The prosthesis consists of three components – the foot, the pylon, and a thermoplastic socket – which can be molded directly over the patient’s limb. Its unique design and assembly utilizes locally available materials, making it ideal for use in regional hospitals in low resource settings. The RightFit prosthesis does not require specialized tools; it can be fit by an ISPO Category II ortopedic technician at a local clinic, which substantially decreases the distance a patient must travel to obtain prosthetic care.
The socket-pylon adapter, an off-the-shelf reducer bushing for PVC piping, distributes the compressive loads that are applied to the device. This generic component can be easily produced in developing countries at local plastics manufacturing companies or purchased at hardware depots. The pylon-foot (ankle) adapter is comprised of a reducer bushing and a PVC cap with a bolt to secure the prosthetic foot to the assembly. These two adapters provide rotational and translational adjustability so that the technician can properly align the prosthesis.
Using bench alignment, the technician will attach the socket-pylon adapter and make angular, rotational, and translational adjustments according to standard prosthetic manuals. After assembly of the prosthesis, the alignment can be further adjusted by locally heating the thermoplastic at the upper adapter with a heat gun, hair dryer, or hot water.
Recently, we contemplated switching from PVC to aluminum, aware of the concomitant increase in cost. Standard prosthetic pylons and adapters (aluminum) collectively cost $75 USD, whereas our current adapters only cost a few dollars at most, especially at wholesale prices. We have chosen to stick with PVC for our device because even the 1.5” diameter tubing can sufficiently withstand up to 10X body weight.