A fellow podiatrist called me recently, stating that she wanted to make a soft orthotic for a patient who had a significant pes planus foot type and was suffering from plantar fasciitis. She wanted to make a soft device because she said the patient had “hard orthotics” in the past and did not tolerate them.
The first thing that we need to think about when deciding on an orthotic prescription is the goal of therapy. Since this patient’s primary complaint is arch pain due to plantar fasciitis, our goal with the orthotic device should be to reduce tension on the plantar fascia. To accomplish this, we need a device that is going to decrease arch collapse in order to decrease lengthening of the arch and increased tension on the plantar fascia. In general, such an orthosis should conform very closely to the arch of the foot and incorporate valgus forefoot correction. This was well described in two articles by Kogler.1,2
Given that this patient also had pes planus, the patient was much more likely to feel the medial edge of the orthosis and perceive the orthosis as too hard if the device was not made with a medial phalange. The medial phalange will increase the width of the orthotic in the mid-arch, spreading the force over a larger surface area and preventing the patient from coming down on the medial edge of the orthosis.
In most cases, it is not the specific material or the rigidity of the material that causes the patient to think that the orthosis feels too hard but rather the fact that the medial edge of the orthosis is irritating the plantar foot and there is excessive local pressure. By prescribing a wider orthosis, force is spread over a larger surface area and localized pressure is decreased.
I advised the podiatrist that she would likely find that the softer orthosis will deform so much under the foot that it is not likely to effectively reduce tension on the plantar fascia and her chances of achieving optimum clinical outcomes are much reduced. I would recommend a more rigid orthosis with the medial phalange and a deep heel cup so one can not only reduce tension on the plantar fascia effectively but also make a device that the patient will find comfortable.
Editor’s note: This blog was originally published at http://www.prolaborthotics.com/Blog/tabid/90/EntryID/459/Default.aspx  and has been adapted with permission from Lawrence Huppin, DPM, and ProLab Orthotics. For more information, visit www.prolaborthotics.com  .
1. Kogler GF, Solomonidis SE, Paul JP. Biomechanics of longitudinal arch support mechanisms in foot orthoses and their effect on plantar aponeurosis strain. Clin Biomech (Bristol, Avon). 1996 Jul;11(5):243-252.
2. Kogler GF, Veer FB, Solomonidis SE, Paul JP. The influence of medial and lateral placement of orthotic wedges on loading of the plantar aponeurosis. J Bone Joint Surg Am. 1999 Oct;81(10):1403-13.