Fig. 1

A 41-year-old woman developed two-level ASD with radicular symptoms at the 5th year after the primary surgery and underwent ACDF with two Zero-P cages as a revision surgery. a Lateral radiograph after the primary surgery showing that ACDF was performed at C4–C5. b MRI before revision surgery showing new degenerative changes at C3–C4 and C5–C6 causing stubborn upper limb pain and numbness. c Lateral radiograph after revision surgery showing that ACDF was performed at both the cranial and caudal levels. d MRI at 2 years postoperatively showing adequate decompression at the C3–C6 levels but new posterior disc herniation at C6–C7 (arrows). e Axial MRI at C6–C7 before and after the revision surgery showing aggravated disc herniation (arrows). The patient suffered from intermittent radiating pain in the right arm that was remediated by conservative treatment.