Adjacent segment degeneration

Adjacent segment degeneration is a common complication of spinal fusion occurring at the adjacent unfused level above or below the fused segment. It is usually encountered in the cervical spine or lumbar spine and occurs with an incidence of roughly between 2% and 4% per year .

The underlying etiology is multifactorial and likely represents the progression of pre-existing degenerative disease accelerated by changes in biomechanical forces due to fusion at the adjacent level.

Adjacent segment degeneration can co-exist with adjacent level ossification but is believed to be distinct from it.