Use of Factors in Spinal Fusion

What are Growth Factors?

Growth factors are polypeptides (proteins), which occur naturally in the body in small quantities. Growth factors regulate cell functions, inter-cell communication and cell proliferation. Growth factors play a significant role in bony metabolism as they can alter the rates of bone formation and bone resorption.

What kinds of bone growth factors are there?

There are a lot of growth factors which affect bone development as e.g. BMPs, GDFs, IGFs, TGFs, and also the growth hormone GH. BMPs (Bone Morphogenetic Proteins) form the most important group of bone growth factors, with BMP-2 and BMP-7 (OP1) representing the most important growth factors in this group. BMP-2 and BMP-7 can be produced synthetically and are approved for the treatment of patients.

How do growth factors work?

Bone growth factors induce osteoneogenesis and bone healing by stimulating the cells to begin new bone formation. This is important in fusion surgeries, which are performed to connect two motion segments and to achieve a solid bone formation.

How are growth factors applied?

Bone growth factors as BMP-2 and BMP-7 are delivered as liquid and will be applied on an absorbable collagen fleece in the operating theatre. Afterwards, the collagen will be attached to the spinal fusion area.

When are growth factors used?

Traditionally, bone graft from the patient is taken to obtain a successful fusion of the motion segments. The harvesting of this bone graft is a separate surgical procedure. This procedure can be avoided by the use of bone growth factors.
Therefore, growth factors can be used during fusion surgeries instead of autologous bone graft or if bone reserves are depleted due to previous bone harvesting surgery. Growth factors can also have side effects as e.g. allergies, hyperostosis etc.
This is the reason why growth factors are used only in case of difficult revision surgery.