A colleague recently asked me which orthotic type would be best for a runner/cyclist who has chronic sub-2nd MPJ capsulitis, which he felt was due to a relatively short first ray. The goal with any capsulitis is to reduce weightbearing on the painful metatarsal head so one should look at the orthotic prescription rather than a specific type of orthotic.
Orthotic shell material. The material of the orthotic shell should be rigid enough to transfer weight off of the metatarsal heads onto the arch of the foot. For example, a semi-rigid polypropylene would work well. The ProAerobic would also work.
Whichever one you choose, include the following in your orthotic prescription:
Orthotic control and cast work. Use a deep heel cup depth (18 mm) if the heel is everted in stance. Use a standard heel cup depth (14 mm) if the heel is rectus or inverted.
Width. Prescribe a wide orthosis. The wider the device, the more surface area there will be under the arch and the more effective the device will be at transferring weight off of the ball of the foot onto the arch.
Cast fill. In this situation, you want the arch of the orthotic to hug the arch of the foot very closely so it is more effective at transferring force off of the metatarsal heads onto the arch of the foot. Accordingly, one should order a minimum cast fill.
Medial heel skive. If the heel is everted in stance, then use a medial skive to help prevent rearfoot eversion.
Inversion. Inverting the cast will result in a higher medial arch. This is beneficial in this situation as it will again transfer force from the metatarsal heads to the mid-arch area. The appropriate amount of inversion will vary depending on how much fill your orthotic lab standardly uses in the medial arch. If your lab manufactures orthoses where the orthoses tend to match the arch close, then about 2 degrees of inversion should be adequate. If your lab uses a lot of medial arch fill, then you will need to invert the device more to achieve a very close contour to the arch.
Cover. Use a cover to the sulcus or toes to provide cushion under the metatarsal heads. I like the 3mm EVA covers. Ask for the cover to be glued “posterior half only” in order to make adjustments easier. The cover can be glued completely after any needed adjustments are complete.
Extensions. Prescribe a 1.5mm Poron extension to the sulcus to provide cushion under the metatarsal heads. Also, prescribe an accommodation for the 2nd metatarsal head. (The lab will put 3mm Korex under metatarsal heads 1 and 3-5.)
Special additions. Prescribe a Poron metatarsal pad or metatarsal bar. These will transfer weight off of the metatarsal head area back to the metatarsal neck and shaft area. With the cover glued only on the back half of the orthosis, it is easy to adjust these additions.
Posts. You can prescribe a rearfoot post to help stabilize the orthosis in the shoe. For bike shoes, a strip post (which is essentially the anterior portion of the post only) often fits better.
Finally, keep in mind that cycling shoes tend to run very small. You may not be able to fit a full width or depth orthosis into these shoes. Since there is far more force on the forefoot during running, I would start with the pair for running shoes and worry about the cycling shoes later. We can easily fit orthoses into cycling shoes but if you start with these, they will not provide optimum pressure reduction in running shoes.
Editor’s note: This blog was originally published at http://www.prolaborthotics.com/Blog/tabid/90/EntryID/475/Default.aspx  and has been adapted with permission from Lawrence Huppin, DPM, and ProLab Orthotics. For more information, visit www.prolaborthotics.com  .