Adjacent segment degeneration (ASD) is not a rare condition
nowadays due to the fact that spinal surgery is more widely
performed. This condition is defined as the recurrence of
symptoms associated with the degeneration at the free segment
above a fusion after symptom-free period. The incidence
of symptomatic ASD is reported to be up to 30% [1]. In
all ASD patients, herniated disc was the most common cause
of repeated surgery.