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Table 2. Primary and secondary outcomes*
Variable
Primary outcome
Baseline (n=159)
2 weeks (n=129) BD
8 weeks (n=142) BD
26 weeks (n=141) IPD BD
52 weeks (n=144)
% (95% CI) success ZCQ
NA
NA
67 (55 to 77)
57 (45 to 69)
1.64 (0.18)
63 (51 to 73)
72 (60 to 81)
0.73 (0.44)
64 (53 to 74)
63 (50 to 74)
1.20 (0.64)
66 (54 to 74)
69 (57 to 78)
0.90 (0.77)
Secondary outcomes
MD
MD
MD
MD
Mean (95% CI) MRDQ (23 points) score
13.0 (11.7 to 14.2)
14.4 (13.3 to 15.5)
10.4 (9.2 to 11.8)
10.6 (9.3 to 12.0)
0.1
7.5 (6.1 to 9.0)
6.5 (5.3 to 7.8)
1.0
NA
NA
NA
6.9 (5.4 to 8.5)
8.1 (6.6 to 9.7)
1.2 (0.28)†
Mean (95% CI) VAS back pain (0-100 mm)
60 (37 to 83)
49 (44 to56)
32 (27 to38)
33 (28 to39)
1 3
24 (19 to 30)
23 (17 to 28)
1NA
NA NA
NA NA
23 (17 to 29)
31 (24 to 37)
8 (0.09)†
Mean (95% CI) VAS leg pain (0-100 mm)
52 (47 to 59)
58 (52 to 64)
23 (18 to 28)
26 (20 to 32)
26 (20 to 32)
22 (18 to 27)
4NA
23 (17 to 30)
26 (20 to 33)
3 (0.54)†
Mean (95% CI) Likert % perceived success‡
NA
NA
NA
NA
NA
51 (40 to 63)
53 (41 to 64)
0.94 NA (0.85)
NA
NA
56 (45 to 67)
49 (38 to 60)
1.37 (0.37)
IPD
BD
IPD
IPD
IPD
BD
OR
(P value)
OR
(P value)
OR
(P value)
OR
(P value)
BD=bony decompression; IPD=interspinous process device; MD=mean difference; MRDQ=modified Roland Disability
ratio; VAS=visual analogue scale; ZCQ=Zurich Claudication Questionnaire.
*Outcomes were analyzed with generalized estimating equations (GEE). Outcome was reported as odds ratio for better success rate when treated with IPD versus bony decompression and overall P value (based on GEE) of interaction between two groups based on continuous outcome scales with mean differences (MRDQ and VAS). †Overall score in continuous outcome scales were not significant (MRDQ and VAS).
‡Likert global perceived recovery defined by 7 point scale from “worse” to “complete” recovery; score was dichotomized between good recovery (1-2) and bad recovery (3-7).
OR (P value)
OR (P value)
Questionnaire; NA=test not administered; OR=odds
