Osseointegration of graphene coated implants

Osseointegration (OI) is the direct anchorage of a metal implant into bone, allowing for the connection of a prosthesis to the skeleton. This is better researched in oral and craniofacial surgery than orthopaedic surgery. The successful process of metal integration into host bone demands synergy between the host bone, the metal implant, and the bone-implant interface. Bridging of gaps between the bone and implant by nascent bone, is dependent on the surface coating of the implant. Metals and metal alloys are primarily used to manufacture OI implants due to their strength and toughness. Hydroxyapatite (HA) coatings have been shown to be superior to titanium alloy coating for stimulating implant bone ingrowth from the native bone. However, loosening of intramedullary implants over time remains a problem for both intramedullary fracture fixation and cementless arthroplasty particularly with osteoporotic bone. Also, HA is not routinely used for OI because the highly osteophilic surface created by HA can result in a stronger bone-HA layer and this layer separates from the titanium surface over time. Graphene oxide (GO) and reduced graphene oxide (RGO) has been investigated for its OI potential in implantology. In a recent animal model study by Li et al, implantation of a graphene coated titanium alloy scaffold in bone demonstrated an improved osteogenic rate and volumetric growth of new bone tissue compared to the uncoated implant. We believe that GO may be a far superior substrate for cell attachment, proliferation, and differentiation on orthopaedic implants than conventional surface coatings.