AK Foam Covers
May 2007 Issue
There sure are a lot of ways to cover limbs today. With all of the choices we have to make-hose or skins, one-piece or two-piece AK, permanent or removable BK-how can you make sure your choice will result in the intended outcome?
While the practitioner and the patient will make the decision, it's the technician who gets the job done. The tools the technician needs to do his or her job correctly start in the fitting room. Just as a practitioner needs measurements, information, and possibly a cast, so a technician needs a tracing, circumferences, height from floor, M/L and A/P measurements, and photos. Without these tools, technicians cannot possibly be expected to hand back a beautiful job.
Let's talk about one-piece AKs. The single most important part of this job is PREPARATION. I cannot stress this enough. If you don't prepare the cover properly, it will fail.
When hollowing out for the socket, the bottom two thirds of the area should have the same circumference as your socket. The top third can be a little snug. What most people don't understand is that if you stretch the cover to fit over a socket, you eliminate the length stretch. You may even need to hollow for the shin components to allow for movement.
After you think you have hollowed it all out correctly, perform a couple of tests. Make a small mark at the center of the knee. Then make two more marks on the knee-one 4 in. above the center mark and another 4 in. below the center mark. Bend the prosthesis 90 degrees, making sure not to apply any downward weight on the foot to keep it on the floor. If the foot will not stay flat, you need to hollow out more to allow for stretch. Measure the distance from the knee center to the marks placed above and below the knee while the leg is bent 90 degrees. Shoot for 2 in. of stretch both above and below the knee mark. Your 4-in. mark should now be 6 in. This guarantees that there will be enough stretch to allow the foam cover to move instead of tear. One of the worst things you can do is shape a beautiful foam cover only to see it come back one week later torn above, below, or through the knee.
After the measurements are correct, lay your hand very lightly on top of the shin and the distal thigh and bend the prosthesis 90 degrees again. You're feeling for foam travel. You want to make sure that the foam moves equally over the socket and the components. If you feel it bunching or grabbing, you have a problem.
Once the foam is hollowed out correctly, take the bag the cover came in and cover the components and socket with one wrap. Cut off the excess and tape it together in a few places. This will act as the separator so the adhesive doesn't stick to the socket or components. If you forget this part, it will take you forever to separate the foam from the inside. Pull a snug nylon stockinette over the components and socket and tie a knot above the proximal socket. Cut the distal end so you can stretch it, and tie a knot that will still fit through the hole in the foam. I use the E-Z Endo glue first to paint the inside upper third of my foam, and then the stockinette area at the top third of the socket. You may have to go farther down the socket if you are going to have thin foam distally.
Pull the foam cover over the stockinette to the top of the socket area, and make sure the knee is where you want it. Wrap the outside of the foam with an Ace® wrap and allow it to sit overnight undisturbed. In the morning, remove the Ace wrap, pull the cover off of the limb, and pull the plastic out of the inside. Pull the distal stockinette up through the top, and cut off the excess. If you cannot trim it close enough, add some glue to the edge so all of the stockinette edge is glued down. This eliminates it from interfering with the knee.
Apply a thin coat of Vaseline® to your components and to the area on the inside of the foam where the components go. Use only a small amount of Vaseline-just enough to take away all of those annoying squeaks. Too much will make a mess. Pull the cover back on the limb and cut it distally so the foot will go back on. You can leave enough of the foam distally so that you add compression to the shin section, but be careful not to create wrinkles when doing so. Put the foot back on. I apply a thin layer of glue to the foot so my foam cover will stick to the top of the foot. Even when I want it to be removable, I just cut it afterward.
All of the preparation is done. The shaping is the fun part, so go have fun putting the final touches to your job.
Ronnie Graves, CO, RTP, is the president of Prosthetics Research Specialists Inc., Bushnell, Florida.