A colleague recently asked me the following question: In patients with a pediatric flatfoot or a young adult with flatfoot deformity with the subtalar joint in neutral upon standing and the first ray doesn't touch the ground, do you add a forefoot extension, first ray cutout or get the forefoot on the ground?
If it is a rigid varus — meaning you cannot push the first metatarsal head to touch the ground when the subtalar joint is in neutral calcaneal stance position — I will usually add a Morton's extension to bring the ground up to meet the first metatarsal head. I like to prescribe the orthosis with the cover glued on the posterior half only and then add a temporary Morton's extension using 1/8" felt in the office. I bevel it onto the orthosis. I then increase the thickness of the Morton’s extension by 3 mm each week, up to about 12 mm. We find out what thickness feels best to the patient and then replace the temporary Morton’s extension with a permanent one made of Korex.
If you are able to plantarflex the first ray so the first metatarsal head touches the ground, I would not add a Morton’s extension but rather, just make sure you are plantarflexing the first ray to the end of the range of motion during casting. Also, one may add a first metatarsal cutout later if necessary.
Editor’s note: This blog was originally published at http://prolaborthotics.com/Default.aspx?tabid=90&EntryID=460  and has been adapted with permission from Lawrence Huppin, DPM, and ProLab Orthotics. For more information, visit www.prolaborthotics.com  .