Table 3.
Time-weighted average of Oswestry Disability Index at 8 years (area under the curve) from adjusted* as-treated analysis according to subgroup
| Subgroup | Number | Mean change in score compared with baseline (SE) | Treatment effect† (95% CI) | |
|---|---|---|---|---|
| Surgical | Nonoperative | |||
| Female | 507 | −35.7 (0.8) | −24.1 (1) | −11.6 (−13.6 to −9.6) |
| Male | 688 | −36.3 (0.7) | −25.8 (0.8) | −10.5 (−12.3 to −8.8) |
| p value | 0.56 | 0.18 | 0.4 | |
| Smoker | 283 | −32.3 (1) | −21 (1.3) | −11.3 (−14.1 to −8.6) |
| Nonsmoker | 907 | −37 (0.6) | −26.1 (0.7) | −10.9 (−12.4 to −9.4) |
| p value | < 0.001 | < 0.001 | 0.78 | |
| No joint problem | 965 | −37.3 (0.6) | −26 (0.7) | −11.3 (−12.8 to −9.8) |
| Joint problem | 222 | −30.5 (1.2) | −21 (1.3) | −9.4 (−12.1 to −6.7) |
| p value | < 0.001 | < 0.001 | 0.22 | |
| Not depressed | 1047 | −36.5 (0.5) | −25.4 (0.7) | −11.1 (−12.5 to −9.6) |
| Depressed | 141 | −32.6 (1.5) | −21.6 (1.8) | −11 (−14.5 to −7.4) |
| p value | 0.013 | 0.045 | 0.97 | |
| Baseline LBP ≤ 4 | 663 | −36.8 (0.7) | −27.6 (0.8) | −9.2 (−10.9 to −7.5) |
| Baseline LBP ≥ 5 | 525 | −34.6 (0.8) | −21.8 (1) | −12.8 (−14.9 to −10.8) |
| p value | 0.04 | < 0.001 | 0.005 | |
| Motor deficit | 502 | −35.8 (0.8) | −24.2 (1) | −11.6 (−13.7 to −9.5) |
| Motor intact | 692 | −36.3 (0.7) | −25.6 (0.8) | −10.7 (−12.4 to −9) |
| p value | 0.59 | 0.25 | 0.49 | |
| Posterolateral herniation | 921 | −36.7 (0.6) | −25.9 (0.7) | −10.8 (−12.3 to −9.3) |
| Other herniation location | 273 | −33.8 (1.1) | −22.2 (1.2) | −11.6 (−14.3 to −9) |
| p value | 0.017 | 0.008 | 0.59 | |
| Working | 749 | −37.5 (0.6) | −27.7 (0.8) | −9.8 (−11.4 to −8.2) |
| Disabled | 158 | −26.6 (1.5) | −16.2 (2.1) | −10.4 (−14.5 to −6.4) |
| Other | 288 | −36.3 (1) | −21 (1.3) | −15.2 (−18 to −12.4) |
| p value | < 0.001 | < 0.001 | 0.003 | |
| L2–L3/L3–L4 herniation | 88 | −35.7 (2.2) | −23.5 (2.1) | −12.3 (−17.5 to −7.1) |
| L4–L5 herniation | 457 | −37.2 (0.8) | −25.9 (1) | −11.3 (−13.3 to −9.3) |
| L5 S1 herniation | 649 | −35.2 (0.7) | −25 (0.9) | −10.2 (−12.1 to −8.4) |
| p value | 0.16 | 0.54 | 0.61 | |
| Extruded | 786 | −34.9 (0.6) | −26.2 (0.8) | −8.7 (−10.3 to −7) |
| Protruding | 322 | −35 (1) | −23.8 (1.1) | −11.2 (−13.4 to −9) |
| Sequestered | 86 | −41 (1.9) | −27.4 (2.3) | −13.6 (−18.2 to −9) |
| p value | 0.01 | 0.15 | 0.05 | |
| Duration of symptoms ≤ 6 months | 930 | −37.1 (0.6) | −26.7 (0.7) | −10.4 (−12 to −8.9) |
| Duration of symptoms > 6 months | 265 | −31.7 (1.1) | −18.2 (1.3) | −13.5 (−16.2 to −10.8) |
| p value | < 0.001 | < 0.001 | 0.043 | |
*Adjusted for age, sex, race, marital status, compensation, smoking status, herniation location, stomach comorbidity, depression, diabetes, other§ comorbidity, self-rated health trend, duration of most recent episode, treatment preference, baseline score (for SF-36, Oswestry Disability Index‡, and Sciatica Bothersomeness Index), and center unless the variable itself defined the subgroup; †treatment effect is the difference between the surgical and nonoperative mean change from baseline; ǂthe Oswestry Disability Index ranges from 0 to 100 with lower scores indicating less severe symptoms; §other comorbidities include stroke, diabetes, osteoporosis, cancer, fibromyalgia, CFS, posttraumatic stress disorder, alcohol, drug dependency, heart, lung, liver, kidney, blood vessel, nervous system, hypertension, migraine, anxiety, stomach, bowel; CI = confidence interval; LBP = low back pain; CFS = chronic fatigue syndrome.