Prognostic factors in lumbar spinal stenosis surgery

Figures & data

Table 1a. Patient demographics

Men / women	56 / 53
Mean age	71 (10)
Age groups (years)
30–50	2
50–60	14
60–70	21
70–80	53
> 80	19
Mean dural sac area (mm^2) (SD)	43 (17)
Multilevel stenosis	54
Spondylolisthesis, all grade I	35
Smokers	9

Table 1b. Patient demographics

Outcome assessment parameters, mean (SD)	Preoperatively	At 1-year follow-up	p-value	Pre- and postoperative data available for number of patients
Leg pain (VAS)	68 (24)	37 (32)	< 0.001	76
Back pain (VAS)	54 (28)	36 (30)	< 0.001	77
EuroQol-5D	0.41 (0.29)	0.60 (0.26)	< 0.001	74
Oswestry disability index	46 (15)	31 (20)	< 0.001	57
Self-estimated walking distance				103
< 100 m	51	30	< 0.001
≥ 100 m	54	76	0.001

Paired t-test was used.

Table 2. MRI characteristics, HRLQoL, and functional status in patients with and without spondylolisthesis at 1-year follow-up

	Age	Dural sac area (mm^2)	Multilevel stenosis	EuroQol-5D	Oswestry disability index	Estimated walking distance ^a	Leg pain, VAS ^b	Back pain, VAS ^b
With olisthesis	75 (7)	38 (16)	1.8 (0.8)	0.62 (0.23)	29 (15)	2.3 (1.1)	29 (26)	33 (30)
n =	35	35	35	30	21	35	31	32
Without olisthesis	69 (10)	45 (17)	1.5 (0.8)	0.59 (0.27)	31 (22)	2.5 (1.2)	41.1 (35)	37 (30)
n =	74	74	74	58	43	71	67	68
p-value	0.004	0.04	0.6	0.6	1.0	0.5	0.1	0.6
95% CI for difference in medians ^c	–9 to –1	1 to 19	–1 to 1	–0.11 to 0.04	–12 to 10.1	–1 to 1	–17 to 44	–22 to 29

Mann-Whitney test. Standard deviations in parentheses.

^a Estimated walking distance: 1 = < 100 m, 2 = 101–499 m, 3 = 500–1,000 m, and 4 = > 1,000 m.

^b VAS: visual analog scale.

^c Stratified bootstrap test for difference in medians.

Table 3. Patient satisfaction (global assessment) at 1-year follow-up in relation to pre-and postoperative HRLQoL, functional status, and pain

	EuroQol-5D (SD)			Oswestry disability index (SD)			Leg pain VAS (SD)			Back pain VAS (SD)			Estimated walking distance (SD)
	PO	FU	p-value	PO	FU	p-value	PO	FU	p-value	PO	FU	p-value	PO	FU	p-value
Satisfied	0.44	0.66	< 0.001	45	22	< 0.001	68	26	< 0.001	54	24	< 0.001	1.8	2.8	< 0.001
n 67 (65%)	(0.30)	(0.24)		(15)	(14)		(24)	(28)		(28)	(24)		(0.8)	(1.1)
n =	49	58		36	40		51	61		50	62		65	67
Undecided
n 25 (24%)	0.33	0.49	0.007	50	43	0.2	70	58	0.08	57	53	0.6	1.5	2.0	0.005
	(0.28)	(0.25)		(17)	(21)		(21)	(30)		(28)	(30)		(0.8)	(1.1)
n =	20	21		14	17		21	23		22	24		24	25
Dissatisfied
n 11 (11%)	0.52	0.43	0.3	40	50	0.1	52	55	0.9	53	64	0.1	1.5	1.5	1.0
	(0.25)	(0.27)		(11)	(21)		(26)	(32)		(25)	(25)		(0.5)	(0.9)
n =	7	7		7	6		8	11		8	11		10	11
p ^a	0.2	< 0.001		0.5	< 0.001	0.2	< 0.001		0.9	< 0.001		0.2	< 0.001
p ^b	0.75	< 0.001		0.45	< 0.001	0.15	< 0.001		0.93	< 0.001		0.10	< 0.001

PO: preoperative; FU: 1-year follow-up; ODI: ; VAS: visual analog scale; SD: standard deviation.

p ^a: Kruskall Wallis equality of populations rank test; p ^b: test for trend across ordered groups.

Paired t-test was used to compare outcome measures within global assessment for change in Oswestry disability index, leg and back pain, and estimated walking distance. Wilcoxon matched-pairs signed rank test was used for change in EQ-5D, as this variable did not have a normal distribution according to the Shapiro-Wilk test.

Table 4. Duration of leg pain and outcome measures at 1-year follow-up

Duration of pain pre-operatively	EuroQol-5D	Oswestry disability index	Leg pain	Back pain	Walking distance
Up to 2 years	0.65 (0.24)	25 (17)	31 (29)	31 (30)	2.8 (1.2)
n =	52	36	57	58	62
Over 2 years	0.52 (0.51)	38 (22)	47 (35)	43 (29)	1.1 (1.1)
n =	36	28	41	42	44
p-value	0.01	0.02	0.03	0.05	0.002
95% CI for difference in medians ^a	–0.04 to 0.34	–24 to 2	–52 to –3	–41 to –0.5	–1 to 1

Two-sample Wilcoxon rank-sum test.

Standard deviation in parentheses.

^a Stratified bootstrap test for difference in medians.

Table 5. Duration of back pain and outcome measures at 1-year follow-up

Duration of pain pre-operatively	EuroQol-5D	Oswestry disability index	Leg pain	Back pain	Walking distance
Up to 2 years	0.64 (0.27)	28 (20)	33 (31)	32 (31)	2.6 (1.1)
n =	43	27	48	49	52
Over 2 years	0.54 (0.25)	35 (19)	44 (33)	40 (30)	2.2 (1.2)
n =	42	34	46	47	50
p-value	0.04	0.09	0.1	0.1	0.06
95% CI for differenc in medians ^a	–0.03 to 0.1	–22 to 6	–41 to 14	–37 to 9	0 to 1.5

Two-sample Wilcoxon rank-sum test.

Standard deviation in parentheses.

^a Stratified bootstrap test for difference in medians.

Figure 3. Individual change in leg pain at follow-up.