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QUESTION: In patients with benign subacute and chronic low back pain, is injection treatment effective for relieving pain?
Studies were identified by searching Medline (1966–96), EMBASE/Excerpta Medica (to 1996), and bibliographies of relevant studies.
Studies published as full reports in English, French, German, Dutch, and Nordic languages were selected if they were randomised controlled trials (RCTs) of injection treatment for pain relief in patients who had benign chronic low back pain for ≥1 month.
Data were extracted on study methods, participants, interventions, outcome measures, timing of outcome measures, side effects, and main results. The primary outcome measure was the proportion of patients with pain relief. The quality of study methods was assessed (maximum score, 100 points).
21 RCTs met the selection criteria; 19 RCTs involving 1051 patients provided data on the proportion of patients with pain relief. Quality scores ranged from 23 to 83 points (mean 45 points). 11 RCTs compared injection treatment with placebo, and 10 RCTs compared different types of injection treatment. 1 RCT compared facet joint injections with placebo in 97 patients; no short term or long term difference in pain relief was seen between groups (table). Epidural injections and placebo led to similar results for short term (4 RCTs) and long term (3 RCTs) pain relief (table). When local injections were compared with placebo, 1 RCT showed greater long term pain relief for local injection than for placebo, and 3 RCTs showed no difference in short term pain relief (table). Only 1 RCT showed a difference when different types of injections were compared; morphine steroid injections provided more short term pain relief than did saline steroid injections.
In patients with benign subacute and chronic low back pain, injection treatment is not better than placebo for relieving pain. 1 study showed a long term benefit for local injections.
In 1994, the US Agency for Health Care Policy and Research concluded that injection treatment is infrequently indicated for acute low back pain.1 However, experts continue to recommend this intervention. 2 3
The meta-analysis by Nelemans et al is published in the Cochrane Library and conforms to the high standards of the international Cochrane Collaboration. The authors conclude that “convincing evidence is lacking on the effects of injection therapies” and that more research is needed. This statement infers lack of evidence rather than lack of efficacy.
One weakness of the meta-analysis is the uncertain date of the literature search. The review states that 1996 is the last year searched, but a study from 1997 is included. Pertinent trials may have been published more recently. I found results from only 1 trial done since 1997; they were negative and would not alter the conclusions stated in the meta-analysis. 4
However, a more important weakness is not the analysis itself but, as the authors indicate, the variable quality of the available studies. The authors located only 11 placebo controlled trials, which is an insufficient number to address the effects of combinations of type and location of injection in each patient population. Of the subgroups identified, the evidence supports, although not strongly, the use of local corticosteroid injections for trigger points. 2 small trials, including 1 study with a long follow up (6 weeks), reached statistically significant conclusions. 5 6
Source of funding: no external funding.
For correspondence: Dr P Nelemans, Epidemiology, University of Maastricht, Debyeplein 1, Maastricht, 6200 MD, The Netherlands. Fax +31 43 3884128.