The video below explains how orthotic prescriptions should be written in order to make orthotics that are most effective at treating posterior tibialis dysfunction and other types of severe flat feet.
This video was made as part of a series of training videos to teach podiatrists how to make better orthotics, so you may find it somewhat technical. But many patients in our Seattle foot and ankle clinic have requested more detailed information on how orthotics work to treat plantar fasciitis, so we thought some people would find it valuable.
More information on severe flat feet can be found on these pages:
Today, we are going to be looking at another one of our pathology specific orthoses. As we have mentioned earlier these pathology specific orthoses are based on the best evidence in the literature and trying to come up with the orthotic prescription for any particular pathology.
Today, we are going to look at a device for posterior tibial dysfunction. These are severe flatfeet also known as the adult acquired flatfoot. We are going to be looking primarily at orthoses for the flexible type of adult acquired flatfoot. Our goal here is to try and offer some sort of support for this foot. These are very difficult feet to control with an orthotic device.
A couple of things to keep in mind is that as that foot pronates excessively we are going to have to find methods to apply force medial to the subtalar joint axis in order to try and re-supinate that foot or at least try and prevent it from pronating excessively. So on the orthotic prescription we are going to do several things.
First, we are going to use quite a deep heel cup. We would recommend at least an 18-mm heel cup and it is not uncommon to use up to a 20 or 22 mm heel cup. On our pathology specific device for this pathology we are using a 20-mm heel cup. In addition, we are using a very wide orthosis.
You can see that we have actually incorporated a medial flange that comes up around the medial arch of the foot. You want to make sure you have surface area of the orthosis under the entire foot. We are incorporating a minimum cast fill so that the orthosis conforms very tightly to the arch of the foot to prevent collapse of the arch.
We are also going to incorporate a medial heel skive within the heel cup. This is a varus wedge that is added into the anterior of the heel cup. That varus wedge acts to shift the center force of that orthosis further medial to the subtalar joint axis and applies a supinatory torque around that axis.
Many patients with posterior tibial dysfunction and adult-acquired flatfoot will have a very prominent medial navicular, which can be irritated by the medial flange, so we will incorporate a sweet spot essentially a pocket within the plastic of the orthoses to accommodate that prominent navicular and then finally we put a cover on there for cushion and a rearfoot post to prevent the device from rocking in the frontal plane.
So that is the pathology specific orthoses for treatment of posterior tibial dysfunction and other severe flat foot deformities.