ABSTRACT
The normal human spine is made up of multiple, independent motion segments (vertebrae), which articulate via a three-joint complex (the disc and two facet joints). Although preservation of motion is physiologic and ideal, certain disease states of the spine require immobilization of these independent motion segments through a process known as spinal fusion. Approximately 200,000 spinal fusions are performed each year in the United States. Typically, indications for fusion include instability (e.g., spondylolisthesis, trauma), iatrogenically created instability (e.g., after laminectomy), correction of spinal deformity (e.g., scoliosis or kyphosis), reconstruction of spinal segments after the removal of tumors or infections, and pain due to arthritic conditions of the spine.
