Patient characteristics at baseline
| Surgical (n=297) | Conservative (n=73) | p Value | Adjusted p Value* | |
|---|---|---|---|---|
| Age (years, mean±SD) | 50.4±13.5 | 49.8±12.7 | 0.66 | 0.69 |
| BMI (kg/m2, mean±SD) | 26.7±4.5 | 27.3±4.4 | 0.27 | 0.79 |
| Male gender, n (%) | 168 (56.6) | 43 (58.9) | 0.72 | 0.74 |
| Social class, n (%) | 0.065 | 0.96 | ||
| Blue collar | 132 (44.4) | 38 (52.1) | ||
| White collar | 74 (24.9) | 12 (16.4) | ||
| Not working | 33 (11.1) | 14 (19.2) | ||
| Retired | 58 (19.5) | 9 (12.3) | ||
| Country of origin, n (%) | ≤0.001 | 0.94 | ||
| Switzerland | 255 (85.9) | 46 (63.0) | ||
| Foreign | 42 (14.1) | 27 (37.0) | ||
| Social, n (%) | 0.84 | 0.92 | ||
| Family | 247 (83.2) | 60 (82.2) | ||
| Single | 50 (16.8) | 13 (17.8) | ||
| NASS, mean±SD | ||||
| Pain† | 7.8±2.2 | 7.7±2.7 | 0.64 | 0.88 |
| Neurogenic symptoms‡ | 18.8±6.7 | 17.3±8.3 | 0.098 | 0.84 |
| Function§ | 24.7±8.4 | 25.8±9.3 | 0.32 | 0.72 |
| SF-36, mean±SD | ||||
| Physical¶ | 26.5±7.0 | 27.3±6.8 | 0.39 | 1.00 |
| Mental¶ | 48.7±12.5 | 46.8±14.5 | 0.26 | 0.93 |
*p Value after adjustment with inverse probability weighting.
Possible NASS subscale scores range from †0 to 10, ‡0 to 30 and §0 to 45; lower scores indicate lower severity of symptoms.
¶Possible score range for both SF-36 subscales is 0 to 100; higher scores indicate lower severity of symptoms.
BMI, body mass index; NASS, North American Spine Society lumbar spine outcome assessment instrument; SF-36, 36-Item Short-Form Health Survey.