Table 3.

Overall results of preoperative parameters of disc degeneration

Histological evaluation (Histological Degeneration Score, HDS) [57, 58]
Nucleus pulposus (n = 44)	11.4 Range 7–14 SD ± 2.0
Annulus fibrosus (n = 45)	7.6 Range 4–12 SD ± 2.2
X-ray investigation (n = 35)
Disc space heightanterior	8.6 mm Range 5.9–13.1 mm SD ± 2.1
Disc space heightposterior	5.0 mm Range 2.3–7.4 mm SD ± 1.2
Disc space heightmean	6.8 mm Range 4.1–9.7 mm SD ± 1.5
MRI investigation (n = 30)
Disc degeneration (Pfirrmann classification) [56]	0 to <3rd degree DDD n = 0/30 (0 %) 3rd degree DDD n = 2/30 (6.7 %) 4th degree DDD n = 9/30 (30.0 %) 4th–5th degree n = 3/30 (10.0 %) 5th degree DDD n = 16/30 (53.3 %)