Fabricating a Crow Boot With a Toe Filler

A patient who has a transmetatarsal amputation and severe inversion supination on the affected foot came into the office for a CROW boot (Figure 1). He was wearing a soft dressing and it looked as though he was walking on a softball. We determined it would be best to fabricate a CROW boot with a toe filler to give him a good toe lever for extra balance and gait stability. While there are commercially available devices, I prefer to make devices in-house. This article describes the process I used to fabricate the CROW boot with a toe filler for that patient, and explains how you can reproduce the orthosis should you have a similar patient. You can cast the patient right over the soft dressing, since he or she may have ongoing hyperbaric treatments. Padding can be added later to tighten the fit when necessary. After the modifications are finished and the cast is smoothed, pull a few nylons over it. For the laminate, I use ½ -inch pink/white Plastazote bilaminate foam to pull the first layer of the toe filler. You can pull it with an elastic wrap or a plastic bag, or just staple it in place. If you use staples, smooth the staple holes once you remove them to prevent the holes from showing on the AliPlast. After trimming the edges, bevel the sides slightly and put the insert back on the cast. Put a nylon over the insert to hold it in place (Figure 2). Use a shoe insert of the patient's shoe size or a tracing of the sound foot for length, and then precut enough pieces of ½ -inch Plastazote to make the toe filler section (it is a good idea to make the toe filler section about ½- ¾ inch shorter than the shoe so that the extra layers of plastic and foam don't make the CROW boot too long.) You can glue all the pieces on one side and put four of them in the oven at one time. Put glue on the insert and use a heat gun to dry the glue. Pull the first piece of Plastazote out of the oven when it is flexible enough to pull over the insert. You can then put another piece of Plastazote into the oven and take the next piece of heated Plastazote out and layer it over the first one. Repeat this process until all the pieces are pulled over the cast. Make sure all the edges are pressed down, and that there are no bubbles when pulling pieces over the cast. Also, consider the direction you will lay them. You don't want the filler to be too dorsiflexed or too plantarflexed. You also want to maintain a good line of progression for foot shape (Figure 3). Remove the insert from the cast and cut away the excess nylon. Use a band saw or bread knife to cut the plantar flat side, and then use the shoe insert to trace on the bottom of the foot shape. Then begin shaping the insert to reflect the inside of a shoe. Put the insert back on the cast when the shaping is done, and pull two nylons over the insert and cast to keep the insert in place. Put baby powder on the toe filler to prevent the AliPlast from sticking to it. Proceed to fabricate as you would a standard CROW boot. Pull a layer of ¼-inch AliPlast over the cast/filler assembly, taking care not to bump the filler alignment. Pull it with the seam down the anterior side and up the plantar surface. After the AliPlast is sealed, pull it under vacuum. Use a heat gun on the outer surface until the AliPlast changes texture slightly. This helps seal any air leaks and helps the foam maintain its new shape. You can now cut off the seam with a two-inch flap on the anterior side and flush on the plantar surface and the front of the toe. Smooth the plantar seam with a fresh piece of sand screen. Use a staple gun to put a row of staples up and down both sides of the anterior seam, stopping at the toe filler. Using a scalpel, cut the anterior seam away so the stapled sides remain, and you can see the nylons on the cast between the two rows of staples. Cut the cap off the AliPlast just around the edge. Pull a nylon over the foam and tuck it under the cap. Tape the cap to the pipe and staple it around the edges (Figure 4). At this point you can pull it like an AFO. After the plastic has cooled on the surface to the point that is not tacky, wrap it in a thermal covering to hold the heat in, which will prevent the plastic from warping as it cools. I used Reflectix insulation (Figure 5). After it has cooled, which usually takes about an hour, it can be cut off and buffed out. Be careful not to cut into the toe filler section as you cut around. If you do nick it, sand off the cut, reduce the outer edge, and recover it with P-Cell foam to hide the mistake. Once the AFO edges are finished, replace the toe filler and AFO section onto the cast. Pull a nylon tightly over it to hold it in place. Flip the cast over so the toe is pointing up. Pull another layer of AliPlast over the cast with the seam running down the plantar surface and the posterior side. Pull it under vacuum and heat the foam with the heat gun. You should be able to easily see the edges of the plastic under the foam. The hardest part of doing a CROW boot is being able to cut the foam down the edge of the AFO section. Use a fresh number 11 scalpel blade and start at the top edge of the AFO. Cut into the foam near the top of the cast and feel for the edge of the plastic. You should be cutting with the side of the blade against the plastic (under the Aliplast). The blade should be at an angle so that you can feel it lightly touch the plaster and you can utilize as much of the blade edge as possible to cut with. You can then gently pull the blade around the trim lines. Do not cut all the way around the proximal sides. You can cut about 1½ inches from the anterior trim lines. Use scissors to cut a 1 ½ -inch slot out of the AliPlast so that when the anterior plastic is pulled, the foam section ends at the AFO trim line and the anterior plastic overlaps the AFO plastic. This gap will taper down to a width of about ½ inch at the toe. After the foam is cut, pull out the cut nylon from underneath the AliPlast and pull a fresh nylon. Rub baby powder on the toe filler again to prevent sticking. Pull a nylon tightly over the anterior pad, making sure that the knot is at the plantar toe. Use electrical tape to hold the nylon superior to where the anterior shell trim line will be to prevent the foam from pulling away because of too many layers under it. Stick the posterior seam to the bottom of the toe of the AFO using glue a nd cover the knot (Figure 6). You may now pull the anterior plastic. You do not have to wrap the plastic all the way around as it will seal to the AliPlast posterior seam. The less plastic that sticks to the AliPlast seam, the easier it will be to remove the front shell once it has cooled. When the plastic has cooled on the surface enough to not be tacky, pull the Reflectix cover back over the cast to hold in the heat. When the plastic is cool, cut the AliPlast and nylons down the posterior sides. Be careful not to scratch the plastic. You should be able to easily push the front shell off. Mark the shell and trim it. Place the front shell onto the AFO section to ensure a good fit that is easy to close. If it is difficult to close the pieces together, you may need to heat and flare out the edges of the front shell to make it easier for the patient to don the orthosis. Use whatever strapping methods you prefer, and assemble the orthosis to add the sole. Use soft, ¼ -inch crepe as the base layer. Heat it in the oven and pull it over the bottom using an elastic wrap to hold it while it cools. After it is cool, trim the sides at a horizontal angle and then glue the sole in place. To reduce grinding time on the sole, cut a long strip of 24 iron crepe 1½ inches wide. Bevel one end and glue the beveled end and the other side of the strip, as well as the bottom of the sole. Put it in the oven and then pull it around the edge of the sole and over the beveled end, then wrap it with the elastic bandage. Once it is cool, grind the edges until they are level and pull your 3/8-inch heel wedge piece (Figure 7). Finish building your sole and grind in the rocker sole. I usually wait to put the sole on until the fitting in case a sole adjustment is needed. Travis Petersen, BOCP, COA, works at A.O.P. Orthotics and Prosthetics, Fayetteville, North Carolina, as a practitioner and clinic manager. He has also worked as a practitioner and technician for companies in Missouri. He can be contacted at travispetersen@hotmail.com .

Fabricating a Crow Boot With a Toe Filler

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