Spinal fusion surgery stabilizes the spine by joining or fusing two or more vertebrae together so there is no longer movement between the two bones. Bone is taken from the pelvic area or from a bone bank and placed to help form new bone growth between the vertebrae. Metal implants are used to secure the vertebrae while the new bone grows between.
This type of surgery was first performed on people with traumatic injuries to the spine such as a fracture. It was also done on people who had deformities of the spine caused by tumors or by infections. Now, it is also done to help relieve painful symptoms that are caused by deformities of the spine in conditions such as spondylolisthesis, spinal stenosis, or herniated discs. It is often done in conjunction with other procedures such as decompression and debridement.
In spondylolisthesis one vertebrae slips forward over another causing a misalignment in the spine. This can cause compression on the spinal cord or nerve causing pain, weakness, numbness in the legs, or pain in the lower back. Certain athletes, such as football players or weight lifters are at risk for this. If bracing, exercise and stretching do not relieve the symptoms, then surgery is considered as treatment.
With spinal stenosis, a narrowing of the spinal canal occurs. It can happen because of excessive bone growth, thickening of the tissues in the canal, or a herniated disc. But the main cause is the breakdown of tissue caused by the normal aging process. Most people who present with symptoms of spinal stenosis are over the age of 50.
Most often, spinal stenosis occurs in the lower back, but can also present in the neck. Symptoms include weakness, pain and numbness in the buttocks, legs and feet. Conservative treatment is tried first, such as physical therapy, corticosteroid injections, and pain management, but if there is no relief, or if symptoms are severe or continue to worsen, then surgery is done.
With a herniated disc, the disc that cushions the bones in the spinal column have ruptured either through injury or just over time and age. The jelly-like substance that fills the discs squeezes into the spaces that surround the nerve root or the spinal column causing pain, numbness and weakness in the legs or arms. Most herniated discs are treated conservatively with nonsurgical treatments and with time, the symptoms will go away on their own, but in a few cases, surgical treatment is necessary for relief from the symptoms.
http://www.webmd.com/back-pain/spinal-fusion-arthrodesis