Question: North Carolina Subscriber Answer: The descriptors for 22600-22614 can be confusing because they refer to spinal "levels" rather than spinal "interspaces." Arthrodesis implies a fusion of a motion segment, however, and a motion segment refers to two adjacent vertebrae and the intercalary disc (that is, two vertebral segments and the interspace between them). In this case, your surgeon fuses segment L2 to segment L3 (22612) and segment L3 to segment L4 (+22614).Although the procedure involves three vertebrae, the surgeon performs only two fusions.