TABLE 2.

Distribution of Preoperative MRI Phenotypes

MRI Phenotype	Non-ASD n=54, n (%)	ASD n=31, n (%)	P
Disk degeneration	13 (24)	16 (51)	0.002
Disk bulge/protrusion	6 (11)	11 (35)	0.007
Endplate damage	43 (80)	26 (84)	0.630
Annular fissure	1 (2)	1 (3)	0.116
Modic change	22 (41)	18 (58)	0.124
Major degenerative sign	16 (30)	20 (64)	0.002

Bold values represent significant P values <0.05. Pfirrmann grade III or higher disk degeneration and/or presence of disk bulge/protrusion or herniation were considered as major degenerative sign.

ASD indicates adjacent segment degeneration; MRI, magnetic resonance imaging.