5.4. Clinical efficacy of periradicular infiltration. Intention-to-treat analysis (IV)
In the final study population, 80 patients received saline and 80 received methylprednisolone-bupivacaine injection. The affected level on MRI was more often the L4-L5 disc in the methylprednisolone group and the L5-S1 disc in the saline group (p = 0.03). Days on sick leave before the intervention were significantly more in the saline group (p = 0.03), although number of patients on sick leave was similar between the groups. These differences were considered clinically important confounders, and the scores of the treatment effects were adjusted accordingly. For the days on sick leave, a categorical staging was used: 0 days, 1–30 days and over 30 days. For disc level, the L3-L4 discs were combined with the L4-L5 discs.
In each treatment group, follow-up information was obtained at 2 weeks for 79 patients, 4 weeks for 80 patients and 3 months for 79 patients. At the 6-month and 1-year follow-up assessments, information was obtained for 99% of the patients (n=158). Two drop-outs occurred in the steroid group: One patient moved away and the other lived in the remote countryside. A retroperitoneal hematoma developed in one patient on anticoagulant therapy as a complication of the injection (steroid group). The extra costs of the complication were not included in the economic analysis, and no further complications were encountered.
Information on the immediate effects of the intervention on leg and back pain was obtained for 78 patients in the saline group and 79 patients in the methylprednisolone-bupivacaine group. In the saline group, leg pain decreased by 44% and back pain by 53%, as compared with 61% and 52%, respectively, in the steroid group. The treatment effect in leg pain was significantly better in the steroid group (11.9; 95% CI, 2.0–21.8; p = 0.02), whereas no difference was observed for its effect on back pain (p = 0.36).
At the 2-week follow-up assessment, in both treatment groups, a significant improvement from baseline was observed in every outcome parameter except lumbar flexion (within-group data not shown). There was a significant between-group treatment effect in favor of methylprednisolone-bupivacaine for leg pain, SLR and lumbar flexion (Table 4). Leg pain decreased on the average by 24 % in the saline group and by 45 % in the steroid group (Figure 6A, p < 0.01). Patient satisfaction also was significantly greater in the steroid group (12.1; 95% CI, 1.2–23; p = 0.03). At the 4-week follow-up, there was no significant between-group treatment differences in favor of either treatment. At the 3-month follow-up assessment, a significant treatment effect in favor of the saline treatment for back pain was observed, whereas at 6 months, the treatment effects for both leg pain and back pain favored the saline treatment (Table 4). At the 1-year follow-up assessment, there were no treatment effects in favor of either treatment. Leg pain had decreased on average by 65% in both groups. No differences between the two treatments in the AUC-scores of evaluated outcomes were found.
Table 4. Between-groups treatment differences following periradicular infiltration with steroid or saline in the whole study population (total), and in subgroups of contained herniations, extrusions and disc levels L3–4–5. Positive treatment difference values indicate that the steroid treatment was superior to saline.§
| Characteristic | MRI-classification † | Disc level | Total | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Contained herniations | Extrusions | L3–4/L4–5 | |||||||||
| Difference (95% CI) | p | Difference (95% CI) | p | Difference (95% CI) | p | Difference (95% CI) | p | ||||
| Two weeks | |||||||||||
| Leg pain (100-mm VAS) | 24 (8 to 41) | 0.006 | 11 (–5 to 26) | NS | 25 (10 to 40) | 0.002 | 13 (2 to 23) | 0.02 | |||
| Disability (Oswestry %) | 8 (–0.3 to 16) | NS | 8 (–0.4 to 16) | NS | 10 (2 to 17) | 0.009 | 5 (–0.3 to 10) | NS | |||
| Straight leg raising (º) | 7 (–1 to 16) | NS | 6 (–3 to 15) | NS | 9 (0.3 to 18) | 0.043 | 6 (1 to 12) | 0.03 | |||
| Four weeks | |||||||||||
| Leg pain (100-mm VAS) | 19 (3 to 36) | 0.023 | 6 (–10 to 22) | NS | 20 (5 to 35) | 0.008 | 2 (–9 to 13) | NS | |||
| Disability (Oswestry %) | 3 (–5 to 10) | NS | 9 (–0.4 to 18) | NS | 9 (1 to 17) | 0.027 | 2 (–4 to 7) | NS | |||
| NHP pain | 13 (–9 to 35) | NS | 6 (–10 to 21) | NS | 13 (–3 to 29) | NS | –1 (–12 to 11) | NS | |||
| NHP emotional reactions | 5 (–6 to 16) | NS | 5 (–5 to 14) | NS | 7 (–2 to 16) | NS | 2 (–4 to 8) | NS | |||
| Straight leg raising (º) | 9 (–2 to 19) | NS | 5 (–5 to 14) | NS | 8 (4 to 22) | 0.006 | 5 (–1 to 11) | NS | |||
| Three months | |||||||||||
| Leg pain (100-mm VAS) | 1 (–20 to 23) | NS | –3 (–19 to 12) | NS | 3 (–14 to 19) | NS | –1 (–12 to 11) | NS | |||
| Disability (Oswestry %) | –2 (–13 to 9) | NS | 3 (–8 to 14) | NS | 3 (–7 to 13) | NS | –1 (–9 to 6) | NS | |||
| NHP pain | –5 (–27 to 17) | NS | 0 (–18 to 17) | NS | 0 (–19 to 19) | NS | –5 (–18 to 7) | NS | |||
| NHP emotional reactions | 13 (4 to 23) | 0.008 | –2 (–9 to 5) | NS | 5 (–0.6 to 14) | NS | 3 (–2 to 8) | NS | |||
| Straight leg raising (º) | –2 (–12 to 10) | NS | 3 (–8 to 13) | NS | 6 (–4 to 15) | NS | 2 (–5 to 9) | NS | |||
| Six months | |||||||||||
| Leg pain (100-mm VAS) | –23 (–40 to –5) | 0.014 | –17 (–32 to –1) | 0.033 | –8 (–23 to 6) | NS | –16 (–27 to –6) | 0.003 | |||
| Disability (Oswestry %) | –14 (–24 to –3) | 0.01 | –1 (–11 to 9) | NS | –2 (–10 to 7) | NS | –6 (–12 to 1) | NS | |||
| NHP pain | –22 (–43 to –0.3) | 0.047 | –8 (–25 to 9) | NS | –7 (–23 to 9) | NS | –12 (–24 to 0.03) | NS | |||
| NHP emotional reactions | –3 (–13 to 7) | NS | 3 (–5 to 10) | NS | 3 (–4 to 10) | NS | –2 (–7 to 3) | NS | |||
| Straight leg raising (º) | –9 (–21 to 3) | NS | –1 (–11 to 8) | NS | 1 (–9 to 10) | NS | –2 (–9 to 5) | NS | |||
| One year | |||||||||||
| Leg pain (100-mm VAS) | 0 (–16 to 16) | NS | –8 (–22 to 7) | NS | 7 (–7 to 20) | NS | –5 (–16 to 5) | NS | |||
| Disability (Oswestry %) | –1 (–12 to 9) | NS | 4 (–6 to 13) | NS | 4 (–4 to 13) | NS | 0 (–7 to 6) | NS | |||
| NHP pain | 0 (–22 to 22) | NS | –5 (–21 to 11) | NS | –1 (–17 to 15) | NS | –4 (–16 to 8) | NS | |||
| NHP emotional reactions | –3 (–13 to 7) | NS | 3 (–5 to 10) | NS | 2 (–4 to 8) | NS | –2 (–7 to 4) | NS | |||
| Straight leg raising (º) | 4 (–7 to 16) | NS | –1 (–10 to 8) | NS | 7 (–2 to 16) | NS | 5 (–2 to 11) | NS | |||
| § Numbers of patients at the 2-week, 4-week, 3-month, 6-month and 1-year follow-ups were 24/26, 23/26, 24/25, 24/25 and 24/25 (saline/steroid) for contained herniations; 38/43, 37/43, 38/42, 38/42 and 38/42; and 51/36, 51/36, 51/35, 51/35 and 51/35, respectively, for the combined L3–4 & L4–5 levels.†nd p-values are also presented). The values are adjusted to the level of the symptomatic disc and days on sick leave before the intervention.VAS = visual analog scale, MRI = magnetic resonance imaging, CI = confidence interval, NHP = Nottingham Health Profile, NS = not significant. | |||||||||||
Figure 6. Leg pain (mm on VAS, standard deviations indicated with vertical bars) at baseline and at each follow-up assessment after the nerve root infiltration with either methylprednisolone– bupivacaine ( • ) or saline (— • —). The upper box presents the number of patients at each follow-up assessment. A) intention-to-treat analysis, B) subgroup of contained herniations, C) subgroup of extrusions. * P-value of between-group treatment difference at the respective follow-up <0.05, **p<0.01.