Long term pain in the low back when not due to pressure on a nerve root, may require lumbar spinal fusion. This refers to a procedure that results in the permanent loss of movement between any two or more adjacent lumbar vertebrae (spine bone segments in the low back), thereby reducing back pain. There are several procedures that may accomplish a fusion.

• Posterior fusion: When the procedure is carried out through an incision in the back.
• Anterior fusion: When carried out from the front of the patient.
• Interbody fusion: First the disk between two vertebrae is removed and then bone is laid down in the space created between the two vertebral bodies (the interspace).
• Instrumented fusion: A fusion is referred to being instrumented when an appliance is used to accomplish or support the fusion

Anatomy  

• The lumbar spine and pelvis, the low back, supports your entire body. The lumbar spine allows you to bend forward and backward and to twist at the waist. The normal lumbar spine is composed of five building blocks called vertebrae that sit on the sacrum, which is the back part of the pelvic bone (Fig. 1a). Each vertebra is constructed of a body, lamina, and pedicles, which surround an opening, the spinal canal. (Fig. 1b)

Figure 1a	Figure 1b