For a plantar ulcer on the second metatarsal head, Dr. Kirby suggests modifying the orthosis to accommodate the second metatarsal head in the forefoot extension area of the orthosis, which will place greater pressures on the first, third, fourth and fifth metatarsal heads. In addition, he says one may also modify the orthosis to have a metatarsal pad proximal to the second metatarsal head to increase the plantar pressure on the distal second metatarsal shaft and off the second metatarsal head.
Dr. Kirby says another possible modification would be adding a bar forefoot post or "dropoff" across all the metatarsal necks to increase the plantar pressures across all the distal metatarsal shafts. This should reduce the plantar pressures across all the metatarsal heads, according to Dr. Kirby.
Dr. Kirby says the sum total of ground reaction force acting on the plantar foot does not decrease with foot orthoses. However, he notes foot orthoses do have the potential to effectively redistribute ground reaction force to different areas of the plantar foot and hopefully away from the high pressure at-risk areas of the plantar skin.
“Once the biomechanics of plantar pressure reduction is understood, then the only limitation to foot orthosis therapy for patients with diabetes is the imagination and skills of the prescribing podiatrist,” says Dr. Kirby.