Table 1.
Characteristics of patients at baseline. Values are numbers (percentages) unless stated otherwise
| Characteristic | IPD group (n=80) | Decompression group (n=79) |
|---|---|---|
| Median (range) age (years) | 66 (45-83) | 64 (47-83) |
| Male sex | 49 (61) | 37 (47) |
| Median (range) duration of intermittent neurogenic claudication (months) | 12 (2-120) | 22 (1-204) |
| Median (range) body mass index* | 27 (20-48) | 28 (20-37) |
| Duration of back pain (categorized) | 1-3 years | 1-3 years |
| IPD patient’s preferred treatment† | 39 (49) | 36 (46) |
| Bony decompression patient’s preferred treatment† | 0 (0) | 3 (4) |
| No preference for specific treatment† | 41 (51) | 40 (50) |
| Mild paresis or sensory loss | 54 (67) | 56 (71) |
| Localization of stenosis: | ||
| L2-L3 | 2 (3) | 3 (4) |
| L3-L4 | 25 (31) | 22 (28) |
| L4-L5 | 53 (66) | 54 (68) |
| Operated at two levels: | 21 (26) | 16 (20) |
| L2-L3-L4 | 2 (3) | 3 (4) |
| L2-L3 and L4-L5 | 1 (1) | 0 (0) |
| L3-L4-L5 | 17 (21) | 13 (16) |
| Zurich Claudication Questionnaire‡: | ||
| Mean (SD) subscale symptom severity 0-5 scale‡ | 3.1 (0.5) | 3.2 (0.5) |
| Mean (SD) subscale physical function 0-4 scale‡ | 2.6 (0.5) | 2.6 (0.5) |
| Mean (SD) Roland Disability Questionnaire 23 points | 13.0 (5.2) | 14.4 (4.5) |
| Mean (SD) VAS leg pain (mm)§ | 52 (24) | 58 (24) |
| Mean (SD) VAS back pain (mm)§ | 60 (44) | 49 (25) |
| Median (range) SWT (m)¶ | 180 (20-1260) (n=70) | 140 (10-1220) (n=70) |
| Completed SWT¶ | 8 (10) | 13 (16) |
IPD=interspinous process device; SWT=shuttle walking distance; VAS=visual analogue scale.
*Weight in kilograms divided by square of height in meters.
†Patients were asked if they had any treatment preference (no preference, IPD, or bony decompression).
‡Disease specific outcome score; at baseline, score was reported in two subdomains—symptom severity (range 0-5) and physical function (range 0-4).
§Intensity of pain was measured by horizontal 100 mm VAS, with 0 representing no pain and 100 worst pain ever.
¶Obtained before operation; patients were asked to walk until they got symptoms; test was scored “complete” when patients walked 1200 m in 15 min without stopping.