Adjacent segment disease following Dynesys stabilization for lumbar disorders: A case series of mid- and long-term follow-ups

Table 3 Cox model measuring the hazard ratios of reoperation associated with adjacent discs in patients with Dynesys surgery

Variables	Reoperation after Dynesys surgery				Crude HR (95%CI)	Adjusted HR (95%CI)
	n/patients	Event/patients	PY	IR
Upper adjacent modified Pfirrmann grade	12/206
≤ 3		8/123	734.36	10.89	1 (reference)	1 (reference)
≥ 4		4/83	539.21	7.42	0.64 (0.19-2.13)	0.93 (0.22-3.92)
Upper adjacent modified Pfirrmann grade	12/206
≤ 4		11/177	1081.26	10.17	1 (reference)	1 (reference)
≥ 5		1/129	192.31	5.20	0.49 (0.06-3.87)	0.46 (0.05-4.66)
Upper UCLA classification	13/212
1, 2		8/117	737.28	10.85	1 (reference)	1 (reference)
3, 4		5/95	569.17	8.78	0.77 (0.25-2.37)	1.18 (0.31-4.47)
Dynesys level	13/212
2		6/83	468.05	12.82	1 (reference)	1 (reference)
3		7/104	695.30	10.07	0.51 (0.11-2.43)	0.72 (0.19-2.67)
4		0/25	143.10	0.00	--	--
Age, yr	13/212
< 60		7/92	642.72	10.89	1 (reference)	1 (reference)
≥ 60		6/120	663.73	9.04	0.94 (0.31-2.82)	0.69 (0.21-2.24)
Sex	13/212
Male		4/76	456.05	8.77	1 (reference)	1 (reference)
Female		9/136	850.41	10.58	1.15 (0.35-3.76)	0.92 (0.27-3.10)
BMI	13/212
< 25		3/80	460.16	6.52	1 (reference)	1 (reference)
≥ 25		10/132	846.29	11.82	2.01 (0.55-7.36)	3.90 (0.74-16.95)

Hazard ratio adjusted for age, sex, visual analog scale scores for the back and legs, body mass index, medical comorbidities, and preoperative ODI. BMI: Body mass index; CI: Confidence interval; HR: Hazard ratio; IR: Incidence rate per 1000 person-years; PY: Person-years; UCLA: University of California-Los Angeles; VAS: Visual analog scale.