Table 4.

The adjacent segment degeneration of cephalad spinal disc (L3/4)

	PS Group	CBT Group		p Value
Pre-operative (I:II:III:IV:V)	45:39:27:3:0	26:30:12:6:0	Fisher	0.2
Last FU (I:II:III:IV:V)	9:12:33:48:12	18:22:16:12:6		0.02
		Fisher	/	/
p Value	0.00	0.02	/	/

I: the number of patients of Pfirrmann classification Grade I; II: the number of patients of Pfirrmann classification Grade II; III: the number of patients of Pfirrmann classification Grade III; IV: the number of patients of Pfirrmann classification Grade IV; V: the number of patients of Pfirrmann classification Grade V