Bone morphogenetic proteins (BMPs) are a group of growth factors and proteins known for their ability to start the formation of bone and cartilage. Demineralized bone with BMPs are commonly used to augment available bone graft in spinal fusion procedures.
Surgeons can choose from several commercially available human demineralized bone matrix product formulations. But studies show there can be quite a range of variability in these commercially available bone matrices products.
They don’t all have the same ability to stimulate the formation of new bone cells. Differences in constancy and potency have been shown from one product to another. In fact, different batches of the same formulation can have significant differences.
That would suggest that patients could respond differently depending on what batch of bone graft substitute they received. But there’s another variable to consider here and that’s the immune system response to an exogenous (laboratory-produced and externally delivered) graft material. The formation of antibodies to what the body considers a foreign invader could cause the body to reject the bone graft. Or at least create an allergic reaction to it.
But this hasn’t really happened that we can see. Scientists think that’s because these therapeutic proteins aren’t ingested orally or injected intravenously. They are implanted locally — right at the area of bone in the spine where the fusion must take place. By the time the body has mounted a defense, new bone has grown in the fusion site and the spine is well on its way to recovery and healing.
There may be a local inflammatory response but no systemic toxic effects have been reported. Animal studies show that by the time the immune system responds to the presence of bone morphogenetic proteins, the body has used them and already cleared them from the system. No clinically detectable allergic reactions or adverse effects have been reported. It’s not clear yet if repeated exposure to these therapeutic proteins might not have some long-term effects.