Some things to consider:
If you notice that the arches on your devices are coming out higher than the arch on the cast, it could be an indication that the core shells are not cooling down on the vacuum press.
The plastic should be left on the press until completely cooled. If if is taken off too soon, the material will curl up and the arches will seem higher.
Flexibility & Width.
The plastic has to be heated at the correct temperature and taken out of the oven at the right time.
If it is heated at too high of a temperature and/or left in the oven too long, the plastic could shrink up and thin out. This will make the shell seem more flexible than it should.
If it is heated at too low of a temperature or taken out of the oven too soon, it will not wrap around the perimeter of the cast completely and the heel will be wider than it should be.
How Arch Height Effects Flexibility.
Keep in mind that the higher arches will make the shell feel stiffer than the lower arches.
For example, you could have two patients, one with a Pes Cavus foot and one with a Pes Planus foot. They could be the same shoe size and same weight and you could use the same plastic thickness for both of them.
The higher arched Pes Cavus shell will feel stiffer than the low arch Pes Planus shell.
So just remember…. the more acute the curvatures are that the plastic is being formed to….the stiffer the shell will feel. By the same token, the milder the curvatures are that the plastic is molded to, the more flexible the shell will feel.
Stay tuned! We will be looking at frontal plane posting soon!
What do you think? Have you considered the variables at this step in the process?
I am thinking…
of contours and shapes here, as in the previous step. I want to remove any abrupt curvature that could be uncomfortable.
I can add…
an increase to the anterior metatarsal arch (AMA) to support the metatarsals. Think of this as a met pad built into the shape of the shell.
Also, I can increase calcaneal angle (ICA) to raise the distal aspect of the calcaneous and lock it up into the cuboid better. This looks like a cuboid pad built into the shell shape. This results in a stable lateral arch if the calcaneal/cuboid joint is loose.
Both of these additions would take shape in the core shell material once it is molded to the cast. Modifications of this type are referred to as “intrinsic” to the shell. I will be addressing both of these additions more specifically down the line here on the blog.
The benefits of intrinsic additions is that they take up less room in the shoe. Be aware that they are more permanent than adding a pad on top of the shell. To make changes, we would have to remake the devices as opposed to removing pads.
In the next video, we will take a look at molding the core shell material to the casts…
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- Concentrating on “feel” during this step. Trying to follow the general topography of the foot.
- Here we are also trying to create good shapes and contours, especially transitions from one area to another. For instance, the transition from the distal medial calcaneous into the proximal arch is an area that I don’t want to be abrupt.
- At this step as well as the next, some of the added plaster comes off. If it looked like a lot of plaster was added in the previous video, here is where some of it comes off.
- The next step will be filing the cast after it dries for about thirty minutes. In the filing process, the shapes and contours are fine tuned even more.
- More videos in the future! Be sure to subscribe here to receive these articles in your email inbox…
Any questions about this step? Have you seen this done before?
Great question. So many variables at play here. One question that you can ask your patient is this: How long do your shoes usually last? If they wear through a pair of shoes each year, they will probably wear their orthotics out sooner than most people do. Serious runners, high impact athletes and children may fall into this […]
This was the first of two days of shooting video with an unfamiliar camera. There is a bit of focusing and refocusing going on in the middle of the video. Please take your motion sickness pills before viewing! Just kidding, its not too bad, but I thought that was good enough to give you a picture of how plaster additions are done…
The hard part is that the plaster is drying as I am working with it. I want it to dry a little before I smooth it out more with my hands, but I don’t want it to dry so much that it is too hard to work with in my hands. Always a delicate procedure for me!
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I am a Certified Pedorthist and custom orthotic craftsman at Pedologic Orthotics. I started Pedologic Orthotics in 2008 with a desire to deliver premium custom devices with a goal of helping practitioners learn to use orthotics to serve their patients. This is my personal blog. Here I will focus on bringing the orthotic lab to […]