Table 5.
Planned analysis of secondary outcomes in patients with low back pain and degenerative disc randomised to disc prosthesis surgery or rehabilitation. Mean (SD) values at 12 and 24 months (unless stated otherwise) and treatment effect
| Variable | Mean outcome | Treatment effect (95% CI)* | P value† | |
|---|---|---|---|---|
| Surgery | Rehabilitation | |||
| Back pain score‡: | ||||
| Baseline | 64.9 (15.3) | 73.6 (13.9) | ||
| 1 year | 35.6 (28.6) | 53.2 (28.4) | −14.0 (−23.0 to −5.0) | 0.003 |
| 2 years | 35.4 (29.1) | 49.7 (28.4) | −12.2 (−21.3 to −3.1) | 0.009 |
| SF-36 physical component summary: | ||||
| Baseline | 30.5 (7.1) | 30.8 (6.5) | ||
| 1 year | 42.8 (12.2) | 37.3 (11.0) | 5.5 (1.9 to 9.1) | 0.003 |
| 2 years | 43.3 (11.7) | 37.7 (10.1) | 5.8 (2.5 to 9.1) | 0.001 |
| SF-36 mental component summary‡: | ||||
| Baseline | 47.7 (13.0) | 45.2 (13.2) | ||
| 1 year | 50.2 (12.0) | 49.2 (13.2) | 0.2 (−3.5 to 3.8) | 0.90 |
| 2 years | 50.7 (11.6) | 48.6 (12.8) | 1.0 (−2.4 to 4.4) | 0.50 |
| EQ-5D: | ||||
| Baseline | 0.30 (0.27) | 0.27 (0.31) | ||
| 1 year | 0.68 (0.34) | 0.55 (0.32) | 0.13 (0.01 to 0.25) | 0.04 |
| 2 years | 0.69 (0.33) | 0.63 (0.28) | 0.06 (−0.05 to 0.18) | 0.26 |
| HSCL-25 | ||||
| Baseline | 1.81 (0.50) | 1.88 (0.51) | ||
| 1 year | 1.51 (0.49) | 1.67 (0.52) | −0.12 (−0.26 to 0.02) | 0.10 |
| 2 years | 1.50 (0.44) | 1.63 (0.52) | −0.10 (−0.23 to 0.04) | 0.20 |
| FABQ work: | ||||
| Baseline | 25.8 (11.2) | 27.4 (27.4) | ||
| 1 year | 19.2 (14.2) | 23.1 (13.0) | −2.7 (−6.5 to 1.1) | 0.20 |
| 2 years | 18.1 (13.9) | 21.2 (12.8) | −2.1 (−6.0 to 1.7) | 0.30 |
| FABQ physical: | ||||
| Baseline | 14.0 (5.8) | 12.5 (5.6) | ||
| 1 year | 8.8 (6.7) | 9.7 (5.8) | −1.3 (−3.2 to 0.6) | 0.20 |
| 2 years | 9.0 (6.8) | 9.9 (6.0) | −1.5 (−3.4 to 0.5) | 0.10 |
| Self efficacy: | ||||
| Baseline | 3.4 (1.5) | 3.6 (1.6) | ||
| 1 year | 6.3 (3.3) | 5.2 (2.4) | 1.2 (0.3 to 2.1) | 0.01 |
| 2 years | 6.1 (2.9) | 5.3 (2.5) | 1.0 (0.2 to 1.9) | 0.02 |
| No (%) returned to work at 2 years§: | 21 (31) | 15 (23) | — | 0.31 |
| No (%) satisfied with outcome at 2 years¶ | 46 (63) | 26 (39) | — | 0.005 |
| No (%) satisfied with care at 1 year** | 66 (90) | 48 (73) | — | 0.011 |
| No (%) with drug consumption at 2 years†† | 16 (22) | 14 (18) | — | 0.30 |
| Back performance scale at 2 years‡‡ | 3.2 (3.0) | 4.0 (3.0) | −0.8 (−1.8 to 0.2) | 0.10 |
| Prolo scale at 2 years§§ | 7.0 (2.3) | 6.1 (1.9) | 0.9 (0.1 to 1.6) | 0.019 |
ED-5Q score ranges from −0.59 to 1 (1 equals perfect health); self efficacy beliefs for pain scores ranges from 1 to 10 and are summarised and divided by 5. Lower scores indicate that he/she is very uncertain if he/she is able to manage pain. For other scores see footnote to table 1.
*Treatment effect is difference between groups in mean change from baseline. Positive value in SF-36, EQ-5D, self efficacy for pain, and Prolo scale and negative values in remaining variables indicate larger improvement in outcome with surgery.
†Two sided t test for continuous variables and Pearson’s χ2 test for categorical variables.
‡Values not adjusted for significantly different baseline scores.
§Net back to work rate calculated by subtracting patients who went back to work from patients who stopped working.
¶7 point Likert scale (1=completely recovered, 2=much recovered to 7=vastly worsened); slightly improved not included as satisfied with outcome.
**4 point global rating scale, not including slightly satisfied as satisfied with care.
††Use of drugs daily or not.
‡‡Scale comprises five tests with score ranging from 0 to 15 (worst possible).
§§Scale comprises functional and economic parts, summed to give worst score of 2 and best score of 10.