I had a consult call from a ProLab client this afternoon. He has a patient who suffered a midfoot fracture at the base of the fourth and fifth metatarsal shafts. He had no treatment at the time of the injury and he has healed with a large bone callus on the plantar surface of the metatarsals. They create a large prominence on the plantar foot. This area is taking excessive pressure leading to pain, keratoma formation, and occasional skin breakdown. Our client was looking for suggestions on an orthotic prescription for this foot.
Our primary orthotic goal is to transfer pressure off of the plantar prominence. We have a second goal of reducing friction in the area, which will help prevent callus formation and skin breakdown.
A semirigid vacuum formed polypropylene orthosis was recommended. Vacuum formed rather than direct milled polypropylene was chosen because we planned to use a sweet spot in the orthotic shell to accommodate for the plantar prominence.
It was recommended that a standard heel cup and a wide width be prescribed. The wide width will help to transfer pressure from the lateral foot to the medial foot. A standard heel cup was recommended because the heel is not everted. If the heel was everted, we could use a deep heel cup to reduce excessive eversion.
A sweet spot accommodation was prescribed. The location of the sweet spot is based on the outline on the negative cast of the plantar prominence. If you are taking the images of the foot with a ProLab laser scanner then instead of marking the plaster negative cast, you could place felt on the foot at the site of the prominence, which would show up on the laser scan and mark the area of the prominence.
A cushioned top cover was recommended. In this situation, a diabetic top cover was prescribed. The patient is not diabetic but the diabetic top cover has both a layer of Poron for cushion and a layer of Plastazote for accommodation. This should help both cushion and accommodate the plantar prominence. The top cover was prescribed to be glued on the heel only. This means that the cover was glued only in the heel cup area of the orthosis leaving the anterior two thirds of the cover unglued. This allows access to the sweet spot, so additional accommodation can easily be added if necessary. Once we are sure that the patient is comfortable, the cover can be glued down to the rest of the orthosis.
The contralateral foot orthosis was essentially the same prescription but without the sweet spot and there is no need to glue the cover heel only. The cover on the contralateral foot could be glued all the way down.
Finally, after the patient has worn the orthosis for couple of weeks, we will be able to see on the cover where the most wear is occurring. This will be indicative of increased pressure and friction in this area. At this point, I would suggest adding a PTFE Patch on the dorsum of the top cover to reduce the localized friction.
ProLab clients are encouraged to contact one of our medical consultants if they have questions on any patients.