Effect of Percutaneous Kyphoplasty on the progression of intervertebral disc degeneration: a retrospective cohort study

Table 3 Comparison of pre- and post-operative Modified Pfirrmann Grading System (MPGS) grades between the experimental and control groups

Groups			Modified Pfirrmann Grading System (%)								Total	Mean Ridit	p
Groups			1	2	3	4	5	6	7	8	Total	Mean Ridit	p
KVG	Upper disc	Pre	0	2(3)	20(20.3)	38(57.6)	6(9.1)	0	0	0	66	0.413	< 0.001
	Upper disc	Post	0	0	11(16.7)	27(40.9)	24(36.4)	4(6.1)	0	0	66	0.587	< 0.001
	Lower disc	Pre	0	1(1.5)	25(37.9)	34(51.5)	6(9.1)	0	0	0	66	0.404	< 0.001
	Lower disc	Post	0	0	0	12(18.2)	26(39.4)	24(36.4)	4(6.1)	0	66	0.596	< 0.001
NTVG	Upper disc	Pre	0	0	20(30.3)	30(45.5)	15(22.7)	1(1.5)	0	0	66	0.475	0.165
	Upper disc	Post	0	0	16(24.2)	27(40.9)	20(30.3)	3(4.5)	0	0	66	0.525	0.165
	Lower disc	Pre	0	0	26(39.4)	26(39.4)	14(0.2)	0	0	0	66	0.463	0.073
	Lower disc	Post	0	0	20(30.3)	22(33.3)	22(33.3)	1(1.5)	1(1.5)	0	66	0.537	0.073

On comparing the MPGS grades, no statistically significant difference was noted in disc height in either the experimental or control group pre- and post-operatively. Pre Preoperative, Post Post-operative, KVG Kyphoplasty vertebral group. NTVG Non-traumatized vertebral group. p: p-value of Ridit analysis

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