Another option is a substitute bone graft, fashioned with help from nonhuman substances. It derives from marine coral, whose spongy calcium structure resembles human cancellous bone. When these substitute grafts are placed next to healthy bone, the body remodels them in the same way it remodels human grafts. A bone filler paste now under investigation, however, is as strong as bone within 12 hours, according to a report of a study of patients whose wrist fractures were injected with the paste. Also under investigation are injections of growth factor proteins, such as morphogenic protein and transforming growth factor-beta, found naturally in the body in very small amounts.
Animal studies show growth with injections similar to that with autologous grafts.
The hope, he says, is that injected fractures, even with large areas of missing bone, will heal faster and be stronger, without grafts. Although exactly how the stimulators heal is unknown, manufacturers' studies showed the devices did in fact affect cellular processes. For direct stimulation, an electrode is implanted at the fracture, linked through the skin to a generator. For indirect stimulation, electric coils outside the limb on the non-fracture side induce an electrical field at the fracture side. In 1994, FDA approved the first ultrasound bone growth stimulator.