I was recently asked “should prefabricated orthoses have top covers?”
The answer depends on the pathology. Whether you are providing a prefabricated or custom orthosis, your treatment goal should be to reduce stress on tissue that being overstressed. For plantar fasciitis, your goal is to decrease tension on the plantar fascia. If you are treating metatarsalgia, your goal should be to transfer pressure off of the metatarsal heads and provide cushion under the forefoot.
When treating plantar fasciitis, the top cover is usually not necessary. What is necessary is that the orthosis decreases tension on the plantar fascia. The ProLab P3 prefabricated orthosis is designed to decrease tension on the plantar fascia by incorporating valgus correction into the forefoot and incorporating a medial heel skive to limit heel eversion. In this situation, a top cover does not play a clinical role. However, you may want to include one for shoe fit purposes. But, clinically it is not necessary.
On the other hand, if you are treating metatarsalgia the top cover is necessary. The top cover can be used to apply extra layers of cushion under the metatarsal heads or to cover a metatarsal pad or metatarsal bar that you may want to add. In this situation, you would want to use a prefab such as the P3 Sport. This has a cushioned EVA top cover with suede-like top layer.
I keep both uncovered and the covered orthosis in my office and usually use covered devices for pathology such as metatarsalgia or when the devices are going into a lace-up athletic shoe. I use the uncovered devices for pathologies where the covers are not clinically necessary and I want more freedom in shoe fit.