AFO Design Process – How An AFO Is Made

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The video above will address the following questions :

1.) How does an AFO get its shape?

2.) What are the different designs of an AFO?

3.) What is a flexible AFO?

4.) What is a semi-rigid AFO?

5.) What is a rigid AFO?

6.) What is a Solid AFO?

7.) Why does the height of an AFO matter?

8.) Why do you use a cast saw on an AFO mold?

9.) How does an AFO help to control varus or valgus?

10.) How does the knee help to stop knee hyperextension and knee buckling?

It is best to learn from the video portion above, but if you would like you can read below for a transcription of the video.

Design choice matters with AFO

Today we are going talk about taking the next step on our AFO fabrication. I have an AFO here in its basic shape. Meaning we still need to take it from where it is now and we need to carve it out of this mold that you see here there is a plaster underneath this plastic and so now we have to create this. I am going to go over just  a few of the things an orthotist actually  thinks about when creating an AFO and we are going to show you how we take after our lines drawn, we are going to cut this.Then show you the sanding process. It is just a very general, in a very general way just to give you an idea what it really takes to make these AFOs.

Here we go. I have a height set right here, this is for our patient and as an orthotist, we will begin with the height in mind. Technically speaking, many people agree that the height of an AFO needs to be 20 millimeters. 20 millimeters distal to the neck of the fibula. That is one way to look at it.Usually, if you see it, it is right around the widest part of the calf or we will say the fibular head was right here something around an inch downward from the fibular head. That is an approximation but technically speaking,  20 millimeters distal to the neck of the fibular head. So here is our height and I am just going through the process now. As an orthotist, we are going to draw our kind. You will see what this turns into in a minute. There are different kinds of AFOs of we have kind of touched on here in these videos. I am going to show you what we mean by different styles. If I have more plastic here, the brace gets stronger at the ankle. If I have less plastic, meaning I trim the brace back here, the brace is going to be a whole very different kind of brace and the effect will be different.  So I am going to start from the back. What we are going to do is I am going to show you will say this is the ankle the apex of the ankle right there and I want to create the brace called a flexible AFO. The brace itself is not necessarily flexible but you can compare it to a solid  ankle one and  in a  relative sense, I suppose it would be more flexible. But once when an orthotist, our brace person talks about flexible AFO for foot drop, this is what they do. They trim back behind the ankle bone and we will just say it is in this general vicinity right here. We are trimming behind that because we do not want to rub on a bone that would not be fun for the patient or the orthotist. This is what it turns out to be. Everyone is slightly different in their connection between this point and the top part of the AFO. But the basics of this is that it comes behind the  ankle bone for a flexible AFO and we would draw our lines up like this. I am just going to cover some other ones before I start drawing too much and confuse anybody. A semi-rigid AFO by many peoples’ accounts will come up more toward the ankle  but stay behind it. So we will be much closer here that would be semi-rigid. Here is our flexible back here,  our trim line back here. So flexible semi-rigid. If we bisect the ankle, many people agree  that is what is termed rigid and a solid would come in front of the ankle bone, something like this. So solid is very different from the amount of plastic here. I mean that is very different than the amount of plastic here. That is approximately two and a half three inches of difference. A flexible AFO if we are coming back to this trim line and we will just bring it on up here, a flexible AFO is for someone that has basically a foot drop. If someone’s knee is more involved, what we try to do is get more involved at the ankle, because the two are connected via bones and ligaments. If someone’s knee buckles when they walk or hyperextends, you may think to go to solid AFO and have more effect in that knee in a good way. You can always trim back to a flexible after the patient has what we call return on their function. This would be here the solid AFO, this would be a trim line for the flexible and we will turn this around here, so you can get an idea of what the solid would look like. So right here is in front of the ankle bone.We are going to continue over our heights here for  the patient. Here is a solid AFO.

Okay, so here is solid AFO.  So this person probably has a foot drop and we also have to think about indirectly supporting the knee. So we need more control of the ankle. I am going to draw now the trim lines for this solid. It comes up like this, very different in its approach and usually a little bit of flare here like this. Okay, you can see the difference. It is in front of the ankle bone here, whereas back here this would be flexible, so more or less foot drop. Oftentimes,  we can include a joint in a brace and it begins in what we call the pre-articulated stage and I am going to show you one of these real quick.

Here is another AFO right here and you can see this particular joint is in there and that would be a pre-articulated and this is the plantar flexion stop before we cut it if we did cut it.

There are bones all throughout the foot, it is kind of amazing how many bones are there. So what an orthotist will typically do is there is a big bone right here, your first metatarsal phalangeal joint. An orthotist does not want to rub on that joint, no one is going to like that. So we stay behind that and we start connecting our lines here. So this would be how solid ankle AFO turns more into now we are going into the foot portion. We have our height comes all the way down here, stays behind the first metatarsal phalangeal joint in most cases and now we have our foot plate. We are going to make it full length at first and then review the process of trimming it back as we fit the patient.  There are times that we do want to come in front of that bone, the first metatarsal phalangeal  joint. So we are going to come up like this and the reason why is if a person intoes, they might have foot drop but they might also bring their foot in and it hits the other foot when they walk. So we need to stop it from coming in and if you can imagine my hands are trying to stop at every step the person takes. So if I was going to do that, I would need something here to stop the intoeing because this is the left foot we do not want to toe going in and then we would need it something in the other side to help keep it straight.  Two opposing forces right there would help to do that for patient and then there can be another three-point pressure system up here. But these 2 points right here are very important, this is medial forefoot extension when it comes past the first metatarsal phalangeal joint. We are in front of the ankle bone here. This is the solid ankle again, so we are going to come up like this and then we are slowly connecting our lines. Now, this is just a straight solid AFO. If there is going to be a lateral tab here, if you can remember my hand being a portion that is trying to steady the leg here and then this right here is something holding the leg straight. We would add on that lateral tab. Some people call it by other names but we will call it a lateral tab and that would just be and that would just be something extra that we’re doing a control varus and valgus alignment,  so that would be the add-on that we would do. And we’ll show you that more on the patient. So now we’re just going to continue on, we’re bringing the lateral side of the trim lines down here and we’re coming behind this bone right here on the lateral side of the foot, and we’ll make this again full foot as needed. The height of an AFO is very important there’s a couple reasons for that. If a person snaps their knee back, if you can imagine a lever arm coming all the way up here trying to do what it can to hold the leg straight so the knee would be right here doesn’t snap back so we’re trying to hold on to the bone like that. Another reason why is we need all of this to offset what’s going to be happening here. It’s kind of like a lever in a sense and we’re trying to offset, so this from dragging down, this foot from dragging down so if we have a longer lever arm here we can spread out the pressure on the leg. You could bring these AFOs way down here and we’ll say just for this for argument’s sake that we made this AFO that height right there. You can imagine this distance right here trying to hold up this whole foot that would hurt, that would press into that leg so much that a person would immediately stop wearing their AFO. So that’s one of the other reasons why we don’t make AFOs that high. So we’re going to trim this out now and we’re going to probably trim out the audio as well later on, but this is how we kind of draw our trim lines. So remember this is a solid ankle in front of the ankle bone right here, flexible is back here and that’s more for patients with foot drop. Now I’m going to start trimming this out, this would be the trimming out process. Now we just drew our lines on this before to kind of get it a feel of the shape that we want. You never want to just cut on it and I suppose just start cutting on this, even after you know the years that I’ve been doing this I still like to draw them so I’m going to tighten up here and get started.



2020-10-21T01:07:27+00:00By |Categories: AFO Braces / Foot Drop|