In our study, we found that the homeopathic preparation Disci/Rhus toxicodendron compositum was not superior to placebo. Compared to no treatment the injection treatment resulted in significant and clinically relevant short-term chronic back pain relief and reduction of rescue medication. In addition, it was safe.
The main strengths of this trial are the double-blind randomized placebo controlled design with a multicenter approach, the inclusion of a no treatment group, the relatively large sample size for a trial on CAM, and the good compliance and follow-up rates. Concealed treatment allocation and sustained blinding in the treatment groups could be ensured for both doctors and patients. Patients were recruited and treated at very different study sites with different clinical settings such as university outpatient clinics, primary care practices, and orthopedic practices to ensure better external validity of the results. With the three armed design we were able to evaluate the impact of the whole intervention (verum group vs. no treatment group) as well as the specific effect of the drug alone (verum group vs. placebo group).
The primary outcome measure (VAS) is a validated and sensitive tool which is widely used to measure pain. The VAS was measured after eight weeks and displays the effect of the intervention at the end of a treatment phase. In addition we evaluated long term effects after 26 weeks. We included a number of secondary outcome measures such as medication intake, back function and quality of life. Those together with the sensitivity and per protocol analyses help to confirm the results.
The placebo control we used was an isotonic saline solution which could not be distinguished from the verum. Like in the verum group, at every treatment session the isotonic solution was injected subcutaneously into the lower back. One may argue that physiological effects caused by the insertion of the needle and the injection of a solution cannot be ruled out. For example, according to acupuncture research those effects could have been mediated by diffuse noxious inhibitory control 
. Thus, the injections themselves, even without an active ingredient, can affect pain perception. Consequently, according to Kaptchuk the placebo control we used can be described as very powerful 
. A recent study on acupuncture shows that pricking the skin without penetration can reduce pain in low back pain patients 
. Our study had the power to detect a clinically relevant difference on VAS between the verum and no treatment (according Ostelo 
around 15 mm). However, between the verum and the placebo group no significant difference was shown on the VAS which might only be statistically significant in a much larger sample.
Another limitation of this trial might be the therapy duration that we chose. We evaluated the effect of 12 therapy sessions within eight weeks. This duration of the therapy might be too short to cause substantial effects in patients with long term chronic low back pain of 15 years. Moreover, today a multimodal approach for patients with chronic low back pain without injection therapy is recommended 
As this was the first prospective study on Disci/Rhus toxicodendron compositum in patients with chronic low back pain we lack the possibility to compare our results with results from other studies. The effectiveness of injection therapy in treating low back pain independent of the injected solution was shown by a study with 110 patients who received either glucose-lignocaine or saline injections 
. And according to a Cochrane review on injection therapy for subacute and chronic low back pain there is no strong evidence for or against the use of any type of injection therapy 
. Another Cochrane review, on acupuncture and dry-needling for low back pain, concludes that acupuncture and dry-needling may be useful adjuncts to other therapies for chronic low-back pain 
. A systematic review 
from 2008 indicates that the injection of sterile water can be used as a treatment option for low back pain during labor. Sterile water seems to be more effective than isotonic solutions 
which might be explained by an osmotic irritation as well as mechanical stimulation in the injection area because of the increased local pressure in the tissue, a kind of sensory stimulation 
. Local anti-nociceptive effects mediated by adenosine A1 receptors as recently shown for acupuncture by Goldman et al. in Nature Neuroscience are also possible 
. This suggests that injections can have strong specific effects. Moreover, local subcutaneous injections of safe substances such as water and saline solution might have its role in the treatment of low back pain and further research would be helpful. We conclude that no superiority of Disci/Rhus toxicodendron compositum over placebo injections could be shown for patients with chronic low back pain. However, injection therapy was safe and a short term reduction of pain and rescue medication was achieved by subcutaneous injections of both verum and placebo when compared to no treatment. The role of local subcutaneous injections of safe substances such as water and saline solution for low back pain management should be further investigated.