Bone Substitution in Spine Fusion: The Past, the Present, and the Future

The problem of bone fusion is of long duration, and the ideal solution has not yet been found, in particular, in pathological conditions (nonunion, osteomyelitis, critical size defects) in which the biological responses are lower than normal. This is why recently basic research has been focused on this field and new and innovative products have been introduced into clinical practice. Spinal fusion can be defined as the bony union between two vertebral bodies after surgical treatment. Bone fusion is the main indication for spinal pathologies such as scoliosis, kyphosis, fractures, dislocations, spondylolisthesis, and intervertebral discs disease. Each year in the USA, more than 200,000 spine fusions are performed. From 1993 to 2001, the rate of cervical spine fusion increased to 433 %, while the rate of thoracolumbar fusion increased from 52 to 352 %. Despite the advances in surgical techniques and the increasing use of stabilization systems, the incidence of nonunion for lumbar fusions remains high (10– 40 %) [1, 2].