Fig. 1

The primary outcomes before and after C5–6 TDR on a 54-year-old female. C4–5 is UAS and C6–7 is LAS. a C5-6 CDDD on the T2-weighted image of MRI before TDR; b–d Neutral lateral X-ray and flexion-extension X-ray before TDR. ROM, LOR, and IDH of C5–6 are 8.6°, − 2.3° and 3.76 mm, respectively; The primary outcomes of C4–5 and C6–7 are 9.7°, 8.5°, 4.41 mm and 5.7°, − 3.6°, 3.37 mm, respectively. e–g Neutral lateral X-ray and flexion-extension X-ray 1 week after TDR. ROM, LOR, and IDH of C5–6 are 7.3°, − 3.5°, and 6.85 mm, respectively; the primary outcomes of C4–5 and C6–7 are 6.3°, 4.8°, 4.19 mm and 4.8°, − 2.6°, 3.85 mm, respectively. h–j Neutral lateral X-ray and flexion-extension X-ray 10 years after TDR. ROM, LOR, and IDH of C5–6 are 9.0°, − 2.7°, and 6.55 mm, respectively; The primary outcomes of C4–5 and C6–7 are 8.1°, 7.0°, 4.61 mm and 6.5°, − 4.1°, 3.84 mm, respectively. There is no statistical change on primary outcomes of C4–5 and C6–7 although a higher IDH of C5–6 after TDR.