. Author manuscript; available in PMC: 2014 May 1.

Published in final edited form as: Spine (Phila Pa 1976). 2013 May 1;38(10):10.1097/BRS.0b013e31828631b8. doi: 10.1097/BRS.0b013e31828631b8

Table 3. Reoperations according to type of index operation.

		Interspinous process spacer only	Spacer plus decompression	Decompression alone	Fusion
Number of reoperations (%)	At 1 year	383/3,318 (11.5%)	124/1,230 (10.1%)	3,100/59,892 (5.2%)	747/12,528 (6.0%)
Number of reoperations (%)	At 2 years	397/2,372 (16.7%)^‡	91/619 (14.7%)^‡	3,575/41,969 (8.5%)^‡	823/8,392 (9.8%)
Odds ratio (95% CI) for reoperation^*	At 1 year	2.45 (2.2, 2.7)	2.09 (1.7, 2.5)	1.00 (ref)	1.14 (1.05, 1.23)
Odds ratio (95% CI) for reoperation^*	At 2 years	2.25 (2.0, 2.5)	1.93 (1.5, 2.4)	1.00 (ref)	1.13 (1.04, 1.22)
Hazard ratio^† (95% CI) for reoperation, using all available follow-up	t < 1 year	2.36 (2.1,2.6)	2.00 (1.7, 2.4)	1.00 (ref)	1.14 (1.06, 1.22)
	1<t<2	1.77 (1.5,2.1)	1.40 (1.0, 1.9)	1.0 (ref)	1.14 (1.02, 1.27)
	t>2	1.70 (1.3,2.2)	1.84 (1.1, 3.0)	1.00 (ref)	1.54 (1.35, 1.76)

Logistic regression adjusting for age, sex, comorbidity score, and previous hospitalization

^†

Proportional Hazards model, adjusting for age, sex, comorbidity score, and previous hospitalization

^‡

Note that 2 year reoperation rates are based on smaller patient numbers than 1 year rates, because of available time of follow-up.