Table 1. Detailed data on operated levels and outcome measures.

Case number	Gender	Age	Operated levels	Baseline ZCQ score	Early ZCQ score	Late ZCQ score	Early ZCQ relative change scale	Late ZCQ relative change scale	Normalized tcMEP change
1	M	84	L12	37	38	52	0.285	−0.045	0.310
2	F	79	L12, 45	26	35	48	0.063	−0.285	1.040
3	F	56	L34	40	35	41	0.391	0.286	1.000
4	F	67	L34	43	19	46	0.692	0.255	4.450
5	M	51	L23, 34, 45	45	51	71	0.211	−0.098	0.977
6	F	71	L23, 34	43	54	63	0.126	−0.020	1.200
7	F	81	L34	34	22	26	0.525	0.468	1.550
8	M	57	L34	34	22	21	0.550	0.570	7.000
9	F	82	L23, 34	47	33	50	0.511	0.259	1.225
10	M	64	L34	44	26	34	0.589	0.462	0.830
11	M	60	L34	44	39	32	0.383	0.494	0.880
12	F	81	L45, L5S1	35	14	31	0.511	0.383	2.360
13	M	58	L12, 23, 34, 45	46	59	70	0.107	−0.059	3.230
14	F	80	L23	39	38	36	0.322	0.357	0.640
15	F	64	L34, 45	38	35	40	0.359	0.267	0.830
16	M	51	L12, 23, 34, 45	35	22	39	0.539	0.224	1.728
17	M	80	L45	45	62	65	0.041	−0.006	1.080
18	F	79	L45	41	41	40	0.304	0.321	0.720

ZCQ score, maximum achievable points at baseline are 55 and after surgery 79 (the lower the score, the better the result); ZCQ relative change scale, relative change divided by baseline score (values over 0.5 are considered significant); normalized tcMEP change, improvement if value ≥1.2. ZCQ, Zurich Claudication Questionnaire; tcMEP, trans-cranial motor evoked potential; M, male; F, female.