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Sep 12

Written by: Larry Huppin, DPM
9/12/2013 5:33 PM

 We had a question from a ProLab client today:   

QUESTION:
I would like your opinion on which one of your orthotic types would be best for a runner/cyclist who has chronic sub 2nd MPJ capsulitis, which I feel, is due to a relatively short first ray. I was thinking the ProAerobic with a Mortons extension. Any input would be appreciated.

ANSWER:
The goal with any capsulitis is to reduce weightbearing on the painful metatarsal head, so we will 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 met heads onto the arch of the foot. So, 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.
HEEL CUP DEPTH: Deep (18mm) if the heel is everted in stance. Standard(14mm) 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 that it is more effective at transferring force off of the met heads onto the arch of the foot. So 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 met heads to the mid-arch area. Try 3 degrees inverted. 

ADDITIONS AND MODIFICATIONS 
COVER: Use a cover to the sulcus or toes to provide cushion under the met heads. I like the 1/8 EVA covers. Ask for the cover to be glued “posterior half only”

EXTENSIONS: Prescribe a 1/16 Poron Extension to the sulcus to provide cushion under the met heads. Also, prescribe an accommodation for the 2nd met head (the lab will put 1/8 Korex under met 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. Because the cover is 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. 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.

 ProLab takes a scientific approach with our orthoses by integrating evidence-based medicine into orthotic therapy. Our team of Medical Consultants regularly evaluates the medical literature pertaining to orthotic therapy and biomechanics. ProLab clients are encouraged to contact a medical consultant whenever they have questions about an orthotic prescription.

For an easy way to stay up-to-date on evidence-based orthotic therapy, subscribe to our free E-Journal. Your will receive a monthly email synopsis of the research that impacts your practice.   
 

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