Outcome assessment in lumbar spine surgery

Figures & data

Table

Question	Method	Answer (paper)
Has there been a uniform method of evaluating results of spine surgery over the past 30 years?	Websearch and systematic review of the literature	NO (I)
Is the protocol of patient-centered evaluation of the Swedish Lumbar Spine Register reliable?	Test-retest design with ICC and kappa statistics	YES (II)
Is VAS useful in describing different diagnostic profiles in persons operated on for lumbar spine disorders?	Mean-plots with 95% CI	YES (III)
Are prospective and retrospective pain assessments comparable?	Correlation with patient satisfaction	NO (III, V)
Is SF-36 useful in describing different diagnostic profiles in persons operated on for lumbar spine disorders?	Mean-plots with 95% CI	YES (IV)
Is SF-36 responsive to change in persons operated on for lumbar spine disorders?	Standardised Response Mean, Standardised Effect Size, paired T Statistics, Responsive-ness Statistics	YES (V)
Is it possible to identify separate subgroups among persons operated on for lumbar spine disorders?	k-cluster analysis	YES (V)
Are Preoperative clusters predictive of 12 months improvement?	Mann-Whitney of prospective and retrospective items	NO (V)
Is SF-36 useful in comparing outcome of spine surgery across nations?	Norm-based scoring	YES (VI)

Table 1.  General objective criteria for the five diagnostic groups

Diagnosis	Criteria for surgical indication
Lumbar disc herniation	Radiating pain in a single dermatome and/or neuromuscular deficits at the same level. MRI or CT confirmation.
Central stenosis	Neurogenic claudication relieved in flexion. MRI or CT confirmation.
Degenerative/segmental pathology	Chronic mechanical LBP resistant to conservative treatment, with or without radiating pain. One of the two should last at least 6 months. MRI or CT confirmation.
Spondylolisthesis	Radiating pain in a single dermatome and/or neuromuscular deficits at the same level. Radiography and MRI or CT confirmation.
Lateral stenosis	Radiating pain in a single dermatome and/or neuromuscular deficits at the same level and/or mechanical LBP. MRI or CT confirmation.

Table 2.  Elective surgical procedures performed

Surgical procedure	Specification
Conventional diskectomy
Microscopic diskectomy
Percutaneus diskectomy	Onik
Decompression
Instrumented anterior fusion	Bak
Uninstrumented posterior fusion
Instrumented posterior fusion	VSP, CCD, Diapason,….
Decompression + uninstrumented posterior fusion
Decompression + instrumented posterior fusion	VSP, CCD, Diapason,….

Figure 1. Computer application. Starting page with flip-top head.

Figure 2. Overview of timeframe of studies, 1993–2003

Figure 3. Preoperative pain graded on the VAS scale regarding back pain (means and 95% CI) related to diagnosis. Abbreviations: See page 3.

Figure 4. Preoperative pain graded on the VAS scale regarding leg pain (means and 95% CI) related to diagnosis.

Table 3.  Patient satisfaction vs. other pain outcomes. The self graded patient satisfaction 12 months after surgery has been tested regarding correlation to other types of pain outcomes

	Patient satisfaction at follow-up
Perceived change (direct question)
Back	0.60
Leg	0.60
VAS (absolute)
Back	0.57
Leg	0.51
VAS (differential)
Back	0.35
Leg	0.35
Use of pain killers
(Absolute)	0.45
(Differential)	0.29

The correlation (Spearman's rho) was significant with p < 0.01 in all instances. Differential value = postoperative value minus preoperative value on the VAS scale. The patient satisfaction at 12 months postoperatively correlated best to the direct question on perceived change both regarding back and leg pain

Table 4.  Characteristics of study population

		Total (n = 477)	Responders (n = 451)	Nonresponders (n = 26)	Asymp. Sig. (2 tailed)^a
Sex^b	Male	240 (50.3)	224 (49.7)	16 (61.5)	0.240
	Female	237 (49.7)	227 (50.3)	10 (38.5)
Age^c		52 (50–55)	52 (50–54)	55 (47–71)	0.211
Duration (months) of
back pain^c		17 (15–19)	18 (15–19)	15 (7–53)	0.664
leg pain^c		15 (14–18)	15 (13–18)	17 (7–40)	0.561
Smoking^b	Yes	122 (25.6)	119 (26.4)	3 (11.5)
	No	347 (72.7)	329 (72.9)	18 (69.2)	0.211
	Missing	8 (1.7)	3 (0.7)	5 (19.2)
Diagnosis^b, d	HD	150 (31.4)	144 (31.9)	6 (23.1)
	CS	130 (27.3)	121 (26.8)	9 (34.6)
	DDD	63 (13.2)	57 (12.6)	6 (23.1)	0.531
	SO	54 (11.3)	52 (11.5)	2 (7.7)
	LS	57 (11.9)	55 (12.2)	2 (7.7)
	Other	23 (4.8)	22 (4.9)	1 (3.8)

^aMann-Whitney; ^bValues are n (%); ^cValues are median (95% CI);

^dAbbreviations, see page 3 and Other: Miscellaneous and combined diagnoses.

Figure 5. SF-36 profiles for the 5 diagnostic categories (bars) compared with normative values for the Swedish normal and sciatica population (lines). Abbreviations, see page 3.

Figure 6. Mean deviations from the norms of the Swedish general population on the eight SF-36 scales for the five diagnostic subgroups, Preoperatively.

Figure 7. Mean values (with 95% CI) of the PF, BP, SF domain and median age for the 5 diagnostic categories.

Figure 8. Mean deviations from the norms of the Swedish general population on the eight SF-36 scales for the five diagnostic subgroups, postoperatively. Abbreviations, see page 3.

Figure 9. Mean deviations from the norms of the Swedish general population on the 8 SF-36 scales for the two identified clusters, Preoperatively. * indicates a significant (Mann-Whitney, p<0.01) difference between the two clusters.

Figure 10. Mean deviations from the norms of the Swedish general population on the 8 SF-36 scales for the two identified clusters, postoperatively. * indicates a significant (Mann-Whitney, p<0.01) difference between the two clusters.

Figure 11. Preoperative SF-36 profiles (mean and 95% CI) for the D- and the X-group compared with normative values for the Swedish and US population. * indicates a significant (Mann-Whitney, p < 0.01) difference between Dand X-group.

Figure 12. Postoperative SF-36 profiles (mean and 95% CI) for the D- and the X-group compared with normative values for the Swedish and US population. * indicates a significant (Mann-Whitney, p<0.01) difference between D- and X-group.

Table 5.  Distribution of patients in the five diagnostic groups in percentage

Diagnosis	Total	1993–1997	1998–2003
Lumbar disc herniation	42.6	50.6	33.4
Central stenosis	21.6	16.9	26.9
Degenerative/segmental pathology	6.8	3.4	10.7
Spondylolisthesis	9.4	8.1	11.0
Lateral stenosis	14.1	14.0	14.3

Table 6.  Elective surgical procedures performed in percentage

Diagnosis	Total	1993–1997	1998–2003
Conventional diskectomy	17.0	20.0	13.7
Microscopic diskectomy	12.7	13.0	12.3
Percutaneus diskectomy	11.4	15.9	6.2
Decompression	35.6	30.3	41.7
Instrumented anterior fusion	1.8	1.4	2.2
Uninstrumented posterior fusion	5.0	4.7	5.3
Instrumented posterior fusion	5.7	5.4	6.2
Decompression +
uninstrumented posterior fusion	0.6	0.8	0.5
instrumented posterior fusion	8.4	7.0	10.1

Table 7.  Mean SF-36 scores for the whole sample

WHOLE SAMPLE	n (%)	Age	Males (%)	PF	RP	BP	GH	VT	SF	RE	MH
Preoperative scores	451 (100)	52 (50–55)	49.7
Mean score				37.27	10.44	25.81	60.93	38.74	55.40	35.88	62.25
SD				20.64	24.48	15.89	24.04	22.46	27.62	43.59	22.58
95% CL, lower				35.36	8.18	24.34	58.70	36.67	52.85	31.85	60.15
95% CL, upper				39.18	12.71	27.28	63.15	40.82	57.96	39.92	64.34
Postoperative scores	351 (100)	52 (50–55)	49.6
Mean score				57.83	36.23	50.14	60.40	52.32	69.59	54.89	71.05
SD				27.22	42.34	27.73	25.33	26.74	30.09	45.85	24.03
95% CL, lower				54.97	31.77	47.22	57.74	49.50	66.43	50.08	68.52
95% CL, upper				60.69	40.69	53.06	63.06	55.13	72.75	59.70	73.58
Preoperative differences from norm	451 (100)	52 (50–55)	49.7
Mean score				−45.76	−67.41	−46.20	−11.30	−28.86	−31.89	−47.21	−18.71
SD				20.33	26.46	16.53	23.58	22.46	27.91	43.25	22.85
95% CL, lower				−47.65	−69.86	−47.73	−13.48	−30.94	−34.47	−51.22	−20.82
95% CL, upper				−43.88	−64.96	−44.67	−9.11	−26.78	−29.31	−43.21	−16.60
Postoperative differences from norm	351 (100)	52 (50–55)	49.6
Mean score				−25.19	−41.88	−22.06	−11.74	−15.61	−17.73	−28.27	−9.91
SD				25.97	41.99	27.79	25.41	27.03	30.30	44.34	24.63
95% CL, lower				−27.91	−46.29	−24.97	−14.41	−18.44	−20.91	−32.92	−12.50
95% CL, upper				−22.46	−37.47	−19.14	−9.08	−12.77	−14.55	−23.61	−7.33

Age is median and 95% CI, Mean score is the group mean, SD the standard deviation. 95% CL is the 95% confidence limits.

Table 8.  Mean SF-36 scores for persons who underwent elective lumbar spine surgery for lumbar disc herniation

HD	n (%)	Age	Males (%)	PF	RP	BP	GH	VT	SF	RE	MH
Preoperative scores	144 (32)	41 (39–45)	55
Mean score				43.77	12.67	25.17	65.87	39.14	53.21	36.11	62.06
SD				20.36	27.26	16.45	23.45	21.52	26.84	43.45	21.88
95% CL, lower				40.42	8.18	22.46	62	35.6	48.79	28.95	58.46
95% CL, upper				47.12	17.16	27.88	69.73	42.69	57.63	43.27	65.67
Postoperative scores	102 (29)	42 (39–45)	52
Mean score				71.13	50.25	58.08	66.44	57.79	75.25	66.67	74.23
SD				23.22	43.59	28.72	25.42	26.71	27.92	42.73	23.26
95% CL, lower				66.57	41.68	52.44	61.45	52.55	69.76	58.27	69.66
95% CL, upper				75.69	58.81	63.72	71.44	63.04	80.73	75.06	78.79
Preoperative differences from norm	144 (32)	41 (39–45)	55
Mean score				−46.24	−73.25	−50.28	−10.70	−30.27	−35.50	−51.03	−19.04
SD				19.80	27.39	16.68	23.43	21.20	26.93	43.49	21.86
95% CL, lower				−49.50	−77.76	−53.02	−14.56	−33.76	−39.94	−58.20	−22.64
95% CL, upper				−42.98	−68.74	−47.53	−6.84	−26.78	−31.07	−43.87	−15.44
Postoperative differences from norm	102 (100)	42 (39–45)	52
Mean score				−18.62	−35.41	−17.06	−9.94	−11.51	−13.38	−20.37	−6.87
SD				23.17	43.75	28.27	25.07	26.24	27.71	42.45	22.96
95% CL, lower				−23.17	−44.01	−22.61	−14.87	−16.66	−18.82	−28.71	−11.38
95% CL, upper				−14.07	−26.82	−11.51	−5.02	−6.36	−7.93	−12.03	−2.36

Age is median and 95% CI, Mean score is the group mean, SD the standard deviation. 95% CL is the 95% confidence limits.

Table 9.  Mean SF-36 scores for persons who underwent elective lumbar spine surgery for central stenosis

CS	n (%)	Age	Males (%)	PF	RP	BP	GH	VT	SF	RE	MH
Preoperative scores	121 (27)	70 (67–71)	42
Mean score				29.68	8.13	26.56	58.71	40.50	57.54	32.92	63.43
SD				20.37	21.04	15.58	23.06	22.50	27.12	44.54	23.50
95% CL, lower				26.01	4.34	23.76	54.56	36.45	52.66	24.9	59.19
95% CL, upper				33.35	11.91	29.37	62.86	44.55	62.42	40.94	67.68
Postoperative scores	97 (28)	69 (67–71)	41
Mean score				43.03	21.01	45.39	57.82	48.30	67.27	37.46	66.57
SD				25.98	34.35	25.81	25.03	27.73	30.21	44.94	24.94
95% CL, lower				37.79	14.05	40.19	52.77	42.71	61.18	28.40	61.55
95% CL, upper				48.27	27.97	50.59	62.86	53.89	73.36	46.52	71.60
Preoperative differences from norm	121 (27)	70 (67–71)	42
Mean score				−42.42	−57.22	−40.79	−6.97	−23.90	−27.26	−43.27	−16.48
SD				21.72	24.84	15.77	23.03	22.87	27.81	43.30	23.70
95% CL, lower				−46.33	−61.69	−43.63	−11.11	−28.01	−32.26	−51.07	−20.74
95% CL, upper				−38.51	−52.75	−37.96	−2.82	−19.78	−22.25	−35.48	−12.21
Postoperative differences from norm	97 (28)	69 (67–71)	41
Mean score				−29.42	−44.96	−22.01	−8.02	−16.19	−17.65	−38.99	−12.80
SD				27.63	37.99	26.59	26.74	29.16	31.10	44.27	25.69
95% CL, lower				−34.99	−52.62	−27.37	−13.40	−22.07	−23.92	−47.92	−17.98
95% CL, upper				−23.85	−37.30	−16.66	−2.63	−10.31	−11.39	−30.07	−7.63

Age is median and 95% CI, Mean score is the group mean, SD the standard deviation. 95% CL is the 95% confidence limits.

Table 10.  Mean SF-36 scores for persons who underwent elective lumbar spine surgery for degenerative disc disease

DDD	n (%)	Age	Males (%)	PF	RP	BP	GH	VT	SF	RE	MH
Preoperative scores	57 (13)	49 (45–56)	51
Mean score				30.02	4.32	18.39	56.29	30.44	42.98	28.07	56.73
SD				15.87	13.67	11.98	26.18	20.66	26.73	41.69	19.87
95% CL, lower				25.81	0.65	15.21	49.34	24.96	35.89	17.01	51.36
95% CL, upper				34.23	7.98	21.56	63.24	35.92	50.07	39.13	62.10
Postoperative scores	44 (13)	47 (43–53)	55
Mean score				53.57	31.40	49.70	56.66	53.37	62.78	59.09	70.14
SD				25.90	40.86	31.75	28.78	24.85	33.62	43.65	25.75
95% CL, lower				45.69	18.82	39.93	47.91	45.72	52.56	45.82	62.21
95% CL, upper				61.44	43.97	59.47	65.41	61.02	73.00	72.36	78.06
Preoperative differences from norm	57 (13)	49 (45–56)	51
Mean score				−54.67	−75.32	−53.97	−16.94	−37.66	−44.64	−56.15	−26.27
SD				16.47	16.43	12.81	24.97	20.69	26.80	41.23	22.34
95% CL, lower				−59.04	−79.68	−57.37	−23.56	−43.15	−51.75	−67.09	−32.20
95% CL, upper				−50.30	−70.96	−50.57	−10.31	−32.18	−37.53	−45.22	−20.35
Postoperative differences from norm	44 (13)	47 (43–53)	55
Mean score				−33.51	−51.61	−24.73	−17.72	−16.72	−25.47	−26.84	−12.76
SD				25.29	39.18	32.30	28.20	26.41	33.75	42.69	27.81
95% CL, lower				−41.20	−63.52	−34.56	−26.29	−24.75	−35.73	−39.82	−21.22
95% CL, upper				−25.82	−39.70	−14.91	−9.14	−8.69	−15.21	−13.86	−4.31

Age is median and 95% CI, Mean score is the group mean, SD the standard deviation. 95% CL is the 95% confidence limits.

Table 11.  Mean SF-36 scores for persons who underwent elective lumbar spine surgery for spondylolisthesis

SO	n (%)	Age	Males (%)	PF	RP	BP	GH	VT	SF	RE	MH
Preoperative scores	52 (12)	46 (41–53)	35
Mean score				43.39	16.35	30.13	64.00	45.00	69.71	53.85	68.15
SD				19.56	32.04	18.03	25.28	24.71	28.48	44.85	20.99
95% CL, lower				37.95	7.43	25.12	56.96	38.12	61.78	41.36	62.31
95% CL, upper				48.84	25.27	35.15	71.03	51.88	77.64	66.33	74.00
Postoperative scores	40 (11)	46 (41–53)	33
Mean score				64.66	43.96	51.20	65.34	54.92	75.00	66.67	78.43
SD				22.71	46.61	26.62	20.86	24.36	25.63	44.66	15.83
95% CL, lower				57.40	29.05	42.69	58.67	47.13	66.80	52.38	73.36
95% CL, upper				71.93	58.86	59.71	72.02	62.71	83.20	80.95	83.49
Preoperative differences from norm	52 (12)	46 (41–53)	35
Mean score				−43.57	−65.84	−42.83	−10.55	−23.45	−18.51	−31.83	−12.47
SD				20.19	31.67	16.65	23.83	24.53	28.24	44.32	20.79
95% CL, lower				−49.20	−74.66	−47.47	−17.18	−30.27	−26.37	−44.16	−18.26
95% CL, upper				−37.95	−57.03	−38.20	−3.91	−16.62	−10.64	−19.49	−6.68
Postoperative differences from norm	40 (11)	46 (41–53)	33
Mean score				−22.06	−38.03	−21.50	−9.06	−13.44	−13.19	−18.94	−2.21
SD				23.53	46.99	26.84	19.40	24.24	25.52	44.91	15.96
95% CL, lower				−29.59	−53.06	−30.08	−15.26	−21.20	−21.35	−33.31	−7.32
95% CL, upper				−14.54	−23.00	−12.91	−2.85	−5.69	−5.02	−4.58	2.89

Age is median and 95% CI, Mean score is the group mean, SD the standard deviation. 95% CL is the 95% confidence limits.

Table 12.  Mean SF-36 scores for persons who underwent elective lumbar spine surgery for lateral stenosis

LS	n (%)	Age	Males (%)	PF	RP	BP	GH	VT	SF	RE	MH
Preoperative scores	55 (12)	53 (51–60)	64
Mean score				38.82	10.91	29.45	56.84	37.12	57.05	35.76	61.25
SD				19.08	22.96	14.19	20.59	20.03	25.66	41.99	24.00
95% CL, lower				33.66	4.7	25.62	51.28	31.71	50.11	24.4	54.77
95% CL, upper				43.98	17.11	33.29	62.41	42.54	63.98	47.11	67.74
Postoperative scores	48 (14)	53 (51–60)	67
Mean score				55.14	33.51	41.35	52.54	44.62	63.28	52.08	67.65
SD				25.83	40.70	24.93	23.42	27.38	30.45	47.59	27.48
95% CL, lower				47.64	21.69	34.12	45.74	36.67	54.44	38.26	59.67
95% CL, upper				62.65	45.32	48.59	59.34	52.57	72.12	65.90	75.63
Preoperative differences from norm	55 (12)	53 (51–60)	64
Mean score				−44.58	−67.19	−42.70	−15.05	−31.22	−30.61	−48.12	−19.67
SD				20.12	24.55	15.63	21.39	19.87	26.05	43.30	23.65
95% CL, lower				−50.02	−73.82	−46.63	−20.83	−36.59	−37.66	−59.83	−26.06
95% CL, upper				−39.14	−60.55	−38.17	−9.27	−25.85	−23.57	−36.42	−13.28
Postoperative differences from norm	48 (14)	53 (51–60)	67
Mean score				−28.06	−44.24	−30.58	−19.24	−23.72	−24.30	−31.59	−13.21
SD				24.97	41.12	24.71	22.79	26.91	30.85	46.25	27.33
95% CL, lower				−35.31	−56.18	−37.75	−25.86	−31.53	−33.26	−45.02	−21.15
95% CL, upper				−20.81	−32.30	−23.40	−12.62	−15.91	−15.34	−18.16	−5.28

Age is median and 95% CI, Mean score is the group mean, SD the standard deviation. 95% CL is the 95% confidence limits.

Table 13.  Responsiveness statistics. their formulas. and relevant differential values and measures of variability used in the calculation of pain and functional outcomes

			SF-36 domains
	VAS back	VAS leg	PF	RP	BP
A. Mean of the individual differential values^a	23.98	29.16	21.09	26.02	24.10
B. Standard deviation of the differential values	36.05	35.52	26.36	44.02	29.34
C. Standard deviation of the preoperative values	27.97	27.61	20.64	24.48	15.89
D. Standard error of the differential values	1.32	1.39	1.41	2.35	1.57
E. Standard deviation of the postoperative values	30.26	31.47	27.36	42.34	27.73
F. Standard deviation of the differential values in patients who considered themselves stable	25.80	28.86	20.13	42.98	10.27
G. Standardised response mean (A/B)	0.67	0.82	0.80	0.59	0.82
H. Standardised effect size (A/C)	0.86	1.06	1.02	1.06	1.52
I. Paired T statistics (A/D)	18.21	20.91	14.99	11.07	15.39
J. Responsiveness statistics (A/F)	0.93	1.01	1.05	0.61	2.35

^abetween postoperative and preoperative values

Table 14.  Intra–class Correlation Coefficients for the outcome variables in the two samples

	Preoperative sample			Postoperative sample
Variable	n	ICC^a	95% CI	n	ICC^a	95% CI
Preoperative duration (months)
Back pain	60	0.85	0.77–0.91
Leg pain	60	0.84	0.75–0.90
Preoperative VAS for pain intensity
Back pain	60	0.78	0.66–0.87	55	0.89	0.82–0.93
Leg pain	60	0.88	0.81–0.93	55	0.85	0.75–0.91
Preoperative SF-36 domain
PF	60	0.82	0.72–0.89	59	0.86	0.78–0.92
RP	60	0.85	0.76–0.91	59	0.71	0.56–0.82
BP	60	0.69	0.51–0.80	59	0.86	0.78–0.92
GH	60	0.86	0.77–0.92	59	0.80	0.68–0.88
VT	60	0.67	0.46–0.80	59	0.87	0.79–0.92
SF	60	0.77	0.65–0.86	59	0.65	0.48–0.78
RE	60	0.67	0.51–0.79	59	0.62	0.43–0.76
MH	57	0.89	0.83–0.94	59	0.83	0.73–0.89

^aTwo-way random model Intraclass Correlation Coefficient

Table 15.  Agreement (weighted kappa) for the outcome variables in the two samples

	Preoperative sample			Postoperative sample
Variables at 12 months	n	K^a	SE^b	n	K^a	SE^b
Back pain improvement^c				54	0.74	0.06
Leg pain improvement^c				53	0.85	0.04
Work situation	57	0.91	0.04	55	0.91	0.04
Use of pain-killers	59	0.85	0.06	53	0.87	0.05
Walking distance	58	0.81	0.05	55	0.77	0.07
Patient's satisfaction				51	0.83	0.09
SF-36 domain
RP	60	0.76	0.08	59	0.64	0.08
RE	60	0.64	0.10	59	0.53	0.09

^aWeighted kappa;^b Standard error); ^cself-rated

Table 16.  Differential values for several pain outcomes categorised by patients' rating of postoperative pain improvement. Values are mean (95% CI)

	Patient self-reported separate outcome in the protocol
	12-month back pain improvement		12-month leg pain improvement
Postoperative minus preoperative rating	Somewhat better	Much better	Somewhat better	Much better
Change in VAS for intensity of back pain	8 (1 – 14)	34 (29–40)	–	–
Change in VAS for intensity of leg pain	–	–	19 (12–27)	39 (33–45)
Change in SF-36 Bodily Pain subscale	10 (7–14)	34 (30–37)	16 (12–22)	29 (24–34)

Table 17.  Differential values for several pain and functional outcomes categorised by patients' rating of postoperative improvement. Values are mean (95% CI)

	Patient self-reported separate outcome in the protocol
Postoperative minus preoperative rating	Much better	Somewhat better	Unchanged	Somewhat worse	Much worse
Change in VAS for intensity of back pain	42 (38 – 47)	14 (6 – 21)	2 (−5 – 8)	−5 (−8 – 17)	−9 (−32 – 14)
Change in VAS for intensity of leg pain	46 (42 – 51)	19 (11 – 26)	9 (2 – 17)	3 (−5 – 12)	−7 (−26 – 12)
Change in SF-36 subscale
Physical Function	36 (32 – 40)	18 (13 – 23)	9 (3 – 13)	3 (−5 – 10)	2 (−8 – 12)
Role Physical	48 (41 – 55)	14 (6 – 22)	16 (6 – 25)	0 (−11 – 11)	−10 (−26 – 6)
Bodily Pain	45 (40 – 49)	16 (12 – 21)	10 (5 – 13)	−2 (−11 – 6)	−4 (−12 – 3)

Table 18.  Crosstabulation between pain outcomes categorised by patients' rating of postoperative improvement and mean score improvement across the five main diagnostic subgroups. Values are median

	Patient self-reported separate outcome in the protocol
Diagnosis		Back pain		Leg pain
	Postoperative minus preoperative rating	Somewhat better	Much better	Somewhat better	Much better
HD	Change in VAS for intensity of back pain	4	23	–	–
	Change in VAS for intensity of leg pain	–	–	9	58
	Change in SF-36 Bodily Pain subscale	10	41	19	40
CS	Change in VAS for intensity of back pain	8	38	–	–
	Change in VAS for intensity of leg pain	–	–	32	47
	Change in SF-36 Bodily Pain subscale	9	31	10	19
DDD	Change in VAS for intensity of back pain	21	49	–	–
	Change in VAS for intensity of leg pain	–	–	19	24
	Change in SF-36 Bodily Pain subscale	10	34	15	18
SO	Change in VAS for intensity of back pain	15	43	–	–
	Change in VAS for intensity of leg pain	–	–	7	43
	Change in SF-36 Bodily Pain subscale	10	41	19	40
LS	Change in VAS for intensity of back pain	14	38	–	–
	Change in VAS for intensity of leg pain	–	–	15	27
	Change in SF-36 Bodily Pain subscale	10	31	10	32

Figure 13. Girolamo Fabritio d'Aqvapendente (1533–1619) L'opere cirughiche. Padua 1671 Second part: On surgical operations, Prologue p. 189

Figure 14. Pierre Bonnard (1867–1947), Le Jardin dans le Var (Garden in Southern France, Var) 1914, oil on canvas 51.0 (h) x 57.0 (w) cm. Villa Flora, Winterthur.

Figure 15. Renè Magritte (1898–1967), Les deux mystéres (The two mysteries) 1966, oil on canvas, 60 × 80 cm, private collection, London.

Figure 16. Paul Klee (1878–1940), Erinnerung an einen Garten (Remembrance of a Garden), 1914, watercolor on linen paper mounted on cardboard, 25.2 × 21.5 cm. Kunstsammlung Nordrhein-Westfalen, Dusseldorf.