Table 4.

Factors predicting walking ability 6 weeks, 6 and 12 months following surgery – univariate analysis

Pre-operative factors	6 week following surgery			6 months following surgery			12 months following surgery
	Coefficient	95% CI of the coefficient	P-value	Coefficient	95% CI of the coefficient	P-value	Coefficient	95% CI of the coefficient	P-value
Age categories
< 60	Ref			Ref			Ref
60–64.5	0.02	(− 0.01, 0.05)	0.222	0.006	(− 0.05, 0.06)	0.803	− 0.007	(− 0.07, 0.06)	0.786
65–69.5	0.03	(− 0.03, 0.10)	0.272	− 0.01	(− 0.06, 0.04)	0.592	− 0.03	(− 0.12, 0.06)	0.489
70–74.5	0.03	(− 0.03, 0.09)	0.287	− 0.02	(− 0.09, 0.04)	0.372	− 0.05	(− 0.19, 0.08)	0.343
≥ 75	0.05	(− 0.04, 0.14)	0.195	− 0.006	(− 0.07, 0.06)	0.830	− 0.04	(− 0.22, 0.13)	0.527
Gender
Female	Ref			Ref			Ref
Male	− 0.02	(− 0.05, 0.01)	0.165	− 0.03	(− 0.09, 0.02)	0.177	0.01	(− 0.05, 0.08)	0.609
BMI Categories (kg/m2)
< 20	Ref			Ref			Ref
20–24.9	− 0.01	(− 0.12, 0.08)	0.744	− 0.02	(− 0.09, 0.05)	0.564	0.01	(− 0.07, 0.09)	0.792
25–29.9	− 0.001	(− 0.09, 0.09)	0.994	− 0.01	(− 0.09, 0.07)	0.783	0.02	(− 0.06, 0.10)	0.621
30–34.9	0.03	(− 0.06, 0.13)	0.508	0.02	(− 0.05, 0.10)	0.534	0.05	(− 0.03, 0.12)	0.209
35–39.9	0.07	(− 0.03, 0.18)	0.155	0.06	(− 0.008, 0.14)	0.084	0.09	(− 0.01, 0.19)	0.079
≥ 40	0.11	(− 0.01, 0.23)	0.123	0.07	(− 0,04, 0.18)	0.204	0.06	(− 0.05, 0.19)	0.253
Maximum walking distance (meters)	− 0.0001	(− 0.0002, 0.0001)	0.230	0.00003	(− 0.0003, 0.003)	0.807	0.0008	(− 0.003, 0.004)	0.626
Time stood (minutes)	0.001	(− 0.006, 0.009)	0.716	0.005	(− 0.001, 0.01)	0.086	0.003	(− 0.009, 0.01)	0.522
Neurological deficit  No
Yes	0.02	(− 0.04, 0.03)	0.852	0.003	(− 0.02, 0.03)	0.775	0.02	(− 0.03, 0.07)	0.446
Presence of comorbidity
No	Ref			Ref			Ref
Yes	− 0.07	(− 0.09, − 0.05)	0.020	0.07	(0.03, 0.10)	0.007	0.07	(0.02, 0.11)	0.011
Work status
No	Ref			Ref			Ref
Yes	− 0.07	(− 0.09, − 0.05)	0.020	0.08	(− 0.05, 0.21)	0.150	0.13	(− 0.05, 0.20)	0.126
Education
Up to & including secondary	Ref			Ref			Ref
Higher education	0.003	(− 0.03, 0.03)	0.818	0.005	(− 0.04, 0.21)	0.150	− 0.04	(− 0.01, 0.12)	0.231
Use of analgesia
No	Ref			Ref			Ref
Yes	− 0.009	(− 0.13, 0.11)	0.847	0.008	(− 0.17, 0.19)	0.907	− 0.13	(− 0.23, 0.09)	0.628
Surgery type
No discectomy	Ref			Ref			Ref
Discectomy	0.06	(0.01, 0.10)	0.019	0.12	(0.07, 0.17)	< 0.001	0.10	(0.06, 0.15)	< 0.001
Duration of symptoms (years)	0.003	(− 0.002, 0.009)	0.166	0.003	(− 0.001, 0.007)	0.121	0.004	(− 0.004, 0.007)	0.243
Zung depression score	0.006	(− 0.003, 0.003)	0.424	0.0007	(− 0.008, 0.009)	0.826	0.004	(− 0.01, 0.02)	0.561
Fear avoidance (work)	− 0.001	(− 0.006, 0.003)	0.434	− 0.002	(− 0.009, 0.004)	0.298	− 0.002	(− 0.01, 0.009)	0.638
Fear avoidance (pain)	− 0.0.006	(− 0.006, 0.005)	0.766	0.003	(− 0.002, 0.008)	0.186	0.002	(− 0.006, 0.01)	0.521
Back pain (NRS)	0.004	(− 0.0003, 0.009)	0.065	0.006	(− 0.004, 0.02)	0.172	0.005	(− 0.01, 0.02)	0.488
Leg pain (NRS)	− 0.01	(− 0.02, − 0.009)	< 0.001	− 0.01	(− 0.02, − 0.003)	0.015	− 0.009	(− 0.002, − 0.01)	0.020
Quality of life (EQ- 5D− 5L Health VAS)	0.00002	(− 0.001, 0.001)	0.953	− 0.0001	(− 0.0005, 0.0002)	0.343	0.0002	(− 0.0008, 0.001)	0.594
Quality of life (EQ-5D-5L)	− 0.07	(− 0.16, − 0.20)	0.008	− 0.09	(− 0.17, − 0.009)	0.034	− 0.05	(− 0.01, − 0.08)	0.038
Disability (ODI)	0.006	(0.005, 0.007)	< 0.001	0.008	(0.005, 0.01)	0.003	0.007	(0.003, 0.01)	0.006

Abbreviations: BMI: body mass index; CI: confidence interval; NRS: numerical rating scale; ODI: Oswestry Disability Index; VAS: visual analogue scale

Bold values represent p < 0.05