Bone graft substitutes are used instead of a patient's own bone or donor bone in surgery to replace damaged or diseased bone. A good bone graft substitute needs to have certain properties to support bone cell growth around the graft site. No bone graft substitutes currently exist that fully replace real bone, but research is being done to develop better materials for bone grafts.
The majority of bone grafts are done using either autograft bone, bone harvested from another place on the patient's own skeleton and transplanted into the damaged site, or allograft bone, which is bone from donor cadavers. The main problem with autografting is that it necessitates another surgical site, causing more pain and a longer recovery time for the patient as well as weakening the bone at the donor site. Allografting requires a donor, and the process used to clean and disinfect the allograft bone reduces its effectiveness as a bone graft. Bone graft substitutes that can replace both autografting and allografting would be a great benefit to patients and doctors.
Most bone grafts are made of a combination of a number of different materials, sometimes including allograft or autograft bone as a component. Factor-based bone substitutes are growth factors derived from bone or blood components which induce bone growth. Cells, usually stem cells, are used in cellular-based grafts to generate new tissues. Ceramic-based bone graft substitutes are utilized to fill in the holes or defects left in the bone after surgery. Bone graft substitutes that are polymer-based perform the same function as ceramics, but are often more suitable for load-bearing areas, such as the knees, and can often be absorbed by the body after healing is complete.
For bone grafting to be most effective, bone graft substitutes should ideally have three important properties. They should physically scaffold and support the growth of new bone cells, which is called osteoconduction. Osteogenecity is the second property that an effective bone graft substitute should have, which refers to the capability of the graft to allow new bone cells to calcify into bone effectively. Bone grafts should also perform a function called osteoinduction, which means inducing a patient's stem cells to form bone cells.
The surgeon responsible for a particular patient's surgery is the best source of information about the different types of bone graft substitutes that might be appropriate for the patient. Different surgeries and diseases will require different things from a bone graft. The options for bone grafts are increasing as more research is done, and there are a number of promising future directions that may greatly benefit bone graft patients, such as tissue engineering and gene therapy.
