Response to treatment
Overall, the treatment was considered to be worthwhile by the patients, with 26 (74% of the valid 35) responding that it was very worthwhile, 5 (14%) responding that it was quite worthwhile, 3 (9%) responding that it was adequate and only 1 (3%) responding that it was not worthwhile. The LBP group were on the lower side of these scores with 7 (64% of the valid 11) responding that it was very worthwhile, 2 (19%) responding that it was quite worthwhile, 1 (9%) responding that it was adequate and this group included the 1 (9%) who responded that it was not worthwhile.
Analyses of the Spearman's correlations of all pain and psychosocial questionnaire items across both the FBS and LBP groups indicate that on average they were only moderately related (within the same time of reference), with a mean of 0.38 (equivalent to P < 0.05), from a range of 0.00 (NS) - 0.86 (P < 0.001). However, as these variables were considered to be conceptually independent, further analyses were carried out on the individual items, rather than bluntly grouping all scores.
Across all analyses of pre- and post-treatment scores, beneficial change was seen in the majority of cases on most variables: the median number of detrimental changes per variable was 2, with a range of 1–5. Tied scores were only moderately common, with a median number of 5 per variable, from a range of 0–19. For the FBS group, the median number of detrimental changes per variable was 1, with a range of 0–4. The median number of ties was 4 per variable, from a range of 0–14. For the LBP group, the median number of detrimental changes per variable was 0, with a range of 0–2. The median number of ties was 1 per variable, from a range of 0–5.
Differences between pre- and post-treatment scores are shown for the FBS group in Table
2 and for the LBP group in Table
3.
Table 2
Efficacy of intrathecal implants in failed back syndrome (n between 20 and 24)
Sensory | Pain | 9.50 (8.00, 10.00) | 5.00 (4.00, 6.00) | 4.22 | <0.00006*
|
| Pain Relief | 9.00 (8.00, 10.00) | 3.50 (2.75, 6.25) | 4.01 | <0.00006*
|
Psychological | Depression | 9.00 (7.00, 10.00) | 4.00 (0.00, 6.00) | 4.01 | <0.00006*
|
| Quality of Life | 10.00 (8.00, 10.00) | 5.00 (3.00, 7.75) | 3.79 | <0.00022*
|
| Coping | 8.00 (7.00, 10.00) | 5.00 (4.00, 7.00) | 3.68 | <0.00032*
|
| Dependency | 8.00 (6.00, 10.00) | 6.00 (3.00, 8.00) | 3.09 | <0.0027*
|
Sociological | Sleep | 9.50 (8.00, 10.00) | 6.00 (4.00, 9.00) | 3.06 | <0.0027*
|
| Work | 10.00 (9.75, 10.00) | 10.00 (8.25, 10.00) | 1.20 | 0.2301 |
| Social Life | 10.00 (9.00, 10.00) | 6.50 (4.00, 8.00) | 3.25 | <0.00137*
|
| Sex Life | 9.50 (8.25, 10.00) | 8.50 (5.00, 10.00) | 2.12 | 0.0340 |
| Driving | 5.00 (2.00, 9.00) | 2.00 (0.00, 6.00) | 3.32 | <0.00097*
|
| Housework | 10.00 (8.00, 10.00) | 6.00 (4.00, 8.00) | 3.83 | <0.00014*
|
| Mobility | 10.00 (9.00, 10.00) | 6.50 (5.25, 9.00) | 3.01 | <0.0027*
|
Table 3
Efficacy of intrathecal implants in low back pain with out prior surgery (n between 9 and 11)
Sensory | Pain | 9.00 (8.00, 10.00) | 6.00 (4.00, 6.00) | 2.87 | 0.0041*
|
| Pain Relief | 8.00 (6.50, 9.50) | 4.00 (1.50, 6.00) | 2.54 | 0.0111 |
Psychological | Depression | 8.00 (5.50, 10.00) | 5.00 (2.00, 6.00) | 2.37 | 0.0178 |
| Quality of Life | 9.50 (8.00, 10.00) | 6.50 (3.75, 7.25) | 2.68 | 0.0074 |
| Coping | 8.50 (7.75, 10.00) | 6.00 (2.50, 7.00) | 2.82 | 0.0048*
|
| Dependency | 8.00 (7.00, 9.00) | 6.00 (5.75, 6.50) | 2.72 | 0.0065 |
Sociological | Sleep | 10.00 (9.00, 10.00) | 7.50 (4.50, 9.00) | 2.68 | 0.0074 |
| Work | 10.00 (8.50, 10.00) | 9.00 (6.50, 10.00) | 1.84 | 0.0658 |
| Social Life | 10.00 (9.00, 10.00) | 8.00 (6.00, 8.00) | 2.71 | 0.0067 |
| Sex Life | 9.50 (7.25, 10.00) | 9.00 (4.75, 10.00) | 1.09 | 0.2757 |
| Driving | 7.00 (3.00, 8.00) | 7.00 (0.00, 8.00) | 0.37 | 0.7114 |
| Housework | 9.00 (7.00, 10.00) | 6.00 (5.00, 8.00) | 1.50 | 0.1336 |
| Mobility | 9.00 (7.00, 10.00) | 8.00 (6.00, 8.00) | 2.84 | 0.0045*
|
The FBS group showed significant improved on the majority of measures: pain score on the 11-point system reduced from a median of 9.50 to 5 (Wilcoxon W = 276.00, Z = 4.22, P < 0.00006). Furthermore, verbal assessment of pain most commonly changed from severe to moderate, and when these ratings were converted to a 4-point numerical system, the improvement was significant (Wilcoxon W = 136.00, Z = 3.64, P < 0.0003). Pain relief interruption on the 11-point system decreased from a median of 9 to 3.50 (Wilcoxon W = 251.50, Z = 4.07, P < 0.00006).
With respect to the psychological dimension of pain experience, for the FBS group the effect of pain on depression reduced from a median of 9 pre-treatment to 4 post-treatment (Wilcoxon W = 249, Z = 4.01, P < 0.00022); on quality of life from a median of 10 to 5 (Wilcoxon W = 189.00, Z = 3.79, P < 0.00022); on coping from a median of 8 to 5 (Wilcoxon W = 258.50, Z = 3.68, P < 0.00032); and on dependency from a median of 8 to 6 (Wilcoxon W = 171.50, Z = 3.09, P < 0.0027).
In the sociological dimension of pain experience, for the FBS group the effect of pain on sleep reduced from a median of 9.50 pre-treatment to 6 post-treatment (Wilcoxon W = 186.50, Z = 3.06, P < 0.0027); on work, there appeared to be no effect, with both medians being 10 (Wilcoxon W = 26.50, Z = 1.20, exact P = 0.2301); on social life, the effect reduced from a median of 10 to 6.50 (Wilcoxon W = 175.50, Z = 3.25, P < 0.00137); on sex life, there appeared to be no effect, with the median changing from 9.50 pre-treatment to 8.50 post-treatment (Wilcoxon W = 86.00, Z = 2.12, exact P = 0.034); on driving, the effect reduced from a median of 5 to 2 (Wilcoxon W = 105.00, Z = 3.32, P < 0.00097); on housework from a median of 10 to 6 (Wilcoxon W = 207.00, Z = 3.83, P < 0.00014); and on mobility from a median of 10 to 6.50 (Wilcoxon W = 201.00, Z = 3.01, P = 0.0027).
For the LBP group, there was a significant reduction in pain score with treatment from a median of 9 to 6 (Wilcoxan, Z = 2.87, p = 0.0041); however, although quality of life measurement changes were similar to the failed back syndrome cohort and showed a trend to improvement this was not statistically significant (Wilcoxan, p > 0.005).
Although the results for work disruption do not look as good as for the other aspects (due to the high number of ties (n = 19 of the 31 valid cases) on this variable), of the 15 patients less than 50 years of age, none were able to work before receiving the implant, but 4 (27%) were able to return to work after implantation.
For the FBS group, the number GP visits per month reduced significantly from 2.24 pre-treatment to 0.72 post-treatment (Wilcoxon W = 136.00, Z = 3.53, adjusted P < 0.05), whereas for the LBP group, the median number reduced from 2.07 pre-treatment to 0.90 post-treatment, but again this did not reach significance (Wilcoxon W = 6.00, Z = 1.60, exact P > 0.1).