Spinal fusion is usually done with metal plates, screws, and rods. Implant failure can occur but the cause is not always known. In this study, scientists look for corrosion currents around the implants. They suspect these electric currents result in bone loss and loosening of the implant.
Past studies have shown that corrosion and wear of metal implants does release metal ions into the area. The cells of the body react to these degradation products. The immune system forms complexes to destroy this debris. The result is inflammation and scarring.
When two metals are in the same area, they can generate electric currents. The electric current has a biologic effect on the bone. Bone-building cells called osteoblasts are destroyed when exposed to this electromagnetic field (EMF).
Without enough bone build-up around the implant, the device can come loose. Bone loss is a common cause of implant and fusion failure. The authors examined implants that had been removed early due to wear and corrosion.
Tests performed on the implants showed scratches and corrosion on the surface of the devices. There was a continuous electrochemical current around the metal. Constant EMF stimulation resulted in a lower number of osteoblasts.
Implant loosening from this sequence of events is called periprosthetic aseptic osteolysis. Periprosthetic means around the prosthesis or implant. Aseptic tells us that there was no infection. Osteolysis is the loss of bone.
This is the first study to show that metal implants can generate electric and electromagnetic energy. The effect on bone leads to bone loss and implant failure. The next step is to find out how this kind of EMF affects osteoblasts and stop it from altering bone growth.