Heel spurs are caused by tension on the plantar fascia. This tension causes new bone to grow along the same plane as the plantar fascia itself. If we alter the weight bearing characteristics of the foot, we can often take the pressure off of the plantar fascia. Will this cause the new bone growth to retard ? No not really, but it will not only slow down the process, it will provide improved comfort.
If the re-positioning of the foot, thereby altering the weight bearing characteristics doesn't cause some relief, we can actually remove some material form the bottom of the orthotic, which will reduce pressure on the immediate area again providing some relief.