Annular closure device lowers reoperation risk 4 years after lumbar discectomy

Figures & data

Figure 1 Enrollment and randomization of patients.

Notes: Among 554 randomized patients, 276 were allocated to ACD and 278 to Control. Owing to 4 patients in whom ACD implant was not attempted, the modified intent-to-treat population consisted of 272 patients with attempted ACD implant and 278 patients assigned to Control. Compliance with clinical follow-up at 4 years was 76% with ACD and 72% with Controls.
Abbreviation: ACD, annular closure device.

Figure 2 Cumulative risk of reoperation over 4 years of follow-up.

Notes: Risk of reoperation was 14.4% (standard error 2.2%) with ACD and 21.1% (standard error 2.5%) with Controls. Log-rank P-value =0.03.
Abbreviation: ACD, annular closure device.

Figure 3 Hazard ratio for reoperation by baseline patient characteristics.

Notes: Plotted values are hazard ratio and 95% confidence interval. Hazard ratio <1 indicates lower risk with ACD; >1 indicates higher risk with ACD. Continuous variables are categorized by the median value.
Abbreviations: ACD, annular closure device; BMI, body mass index; ODI, Oswestry Disability Index.

Table 1 Predictors of reoperation through 4 years by treatment group

Characteristic	Unit	ACD		Control
		HR (95% CI)	P	HR (95% CI)	P
Univariate
Current smoker	Yes vs no	1.86 (0.95, 3.67)	0.07	2.13 (1.21, 3.72)	<0.01
Sex	Female vs male	1.42 (0.73, 2.77)	0.30	2.09 (1.18, 3.69)	0.01
ODI	Per 10-mm increase	1.02 (0.73, 1.41)	0.91	0.86 (0.67, 1.10)	0.22
Leg pain	Per 10-mm increase	1.01 (0.79, 1.29)	0.94	1.14 (0.92, 1.42)	0.23
Age	Per 10-yr decrease	1.24 (0.92, 1.68)	0.16	0.89 (0.66, 1.19)	0.42
Index level	L5-S1 vs lumbar	1.62 (0.82, 3.20)	0.17	0.88 (0.50, 1.56)	0.67
BMI	Per 5-kg/m^2 increase	1.18 (0.81, 1.73)	0.40	1.03 (0.73, 1.39)	0.95
Multivariate
Sex	Female vs male	—	—	2.38 (1.39, 4.06)	<0.01
Current smoker	Yes vs no	—	—	2.24 (1.30, 3.85)	<0.01

Note: Results derived from Cox proportional hazards model.

Abbreviations: ACD indicates annular closure device; BMI, body mass index; CI, confidence interval; HR, hazard ratio; ODI, Oswestry Disability Index.

Figure 4 Change in leg pain severity over 4 years of follow-up.

Note: Plotted values are mean and 95% confidence interval.
Abbreviation: ACD, annular closure device.

Figure 5 Change in Oswestry Disability Index over 4 years of follow-up.

Notes: Plotted values are mean and 95% confidence interval.
Abbreviation: ACD, annular closure device.

Figure 6 Change in Physical Component Summary score from SF-36 questionnaire over 4 years of follow-up.

Note: Plotted values are mean and 95% confidence interval.
Abbreviations: ACD, annular closure device; SF-36, 36-Item Short Form Health Survey.

Figure 7 Change in Mental Component Summary score from SF-36 questionnaire over 4 years of follow-up.

Note: Plotted values are mean and 95% confidence interval.
Abbreviations: ACD, annular closure device; SF-36, 36-Item Short Form Health Survey.

Figure 8 Percentage of patients achieving the minimal clinically important difference in patient-reported outcomes over 4 years of follow-up.

Notes: Minimal clinically important difference defined as reoperation-free improvement from baseline of at least 20 points for leg pain, 15 points for ODI, 5.7 points for PCS, and 6.3 points for MCS (all reported on 0–100 scale).
Abbreviations: ACD, annular closure device; MCS, Mental Component Score; ODI, Oswestry Disability Index; PCS, Physical Component Score.