I spoke with a ProLab client recently who said he had a patient who presented with plantar fasciitis symptoms for which he made her a pair of posted orthoses with a minimum cast fill. The devices worked extremely well at relieving her symptoms. The only problem is now she is feeling like she is somewhat laterally unstable on the left side only. She states that she “wishes she had something to push her inward a little bit.”
I explained that this is a fairly common problem with patients who receive an orthosis that conforms extremely close to the arch of the foot. This type of orthosis tends to work the best at relieving tension on the plantar fascia and thus relieving plantar fascial symptoms but because it conforms so closely to the arch of the foot, there is a potential that the patient can feel it to be somewhat over aggressive in pushing them laterally.
There are couple easy ways to address this problem. The first one is to add a valgus extension to the orthosis to actually apply somewhat of a pronatory force to the foot and the second is to make the orthosis more flexible so that it does not apply as much of supinatory torque to the foot.
Because this patient requested “something to push her the other direction.” We are going to start by adding a valgus extension. However, rather than add the permanent valgus extension immediately, I recommended that he start by simply adding a temporary valgus extension using self adhesive felt. He can fabricate a valgus extension from 3 mm felt and apply that to the orthosis just distal to the anterior edge of the device. He can then give the patient a couple of more pieces of felt so after a week or so she can add another layer and a week after that an another layer and find out how much she really needs to feel most comfortable and supported. Once we determined what works best for the patient we can add a permanent valgus extension.
Another option would have been to simply take the orthosis to a grinder and, from the bottom of the device, grind the arch somewhat thinner to increase the flex. This would decrease the supinatory force being applied to the foot. This is what I do in my office most of the time and, in fact, is the most common modification we do to orthosis in our clinic.