Injection therapy is one of many treatments available for patients with subacute (longer than six weeks) and chronic (longer than 12 weeks) low-back pain. Where the injection is given, what drug is used and why the injection is given can all vary.
The injection can be given into different parts of the spine (the space between the vertebrae, around the nerve roots, or into the disc), ligaments, muscles or trigger points (spots in the muscles that when pressed firmly will produce pain). Drugs that reduce swelling (corticosteroids, non-steroidal anti-inflammatory (NSAIDs)) and pain (morphine, anaesthetics) are used. Injection therapy can be used for individuals with low-back pain with or without pain and other symptoms in the leg.
A number of electronic databases of healthcare articles were searched up to March 2007. This search identified 18 randomized controlled trials (RCTs; 1179 participants) that looked at injections with a variety of drugs compared to a placebo drug or other drugs. The injections were given into the epidural space (between the vertebrae of the back and outside the coverings that surround the spinal cord), the facet joints (the joints of two vertebrae), or tender spots in the ligaments or muscles.
The review authors rated ten of the 18 RCTs as having a low risk of bias in the way the trials were conducted and reported. They were unable to statistically pool the results because the injection sites, drugs used and outcomes measured were too varied. Only five of the 18 trials reported significant results in favour of one of the treatment arms. The reviewer authors considered the likely treatment benefits to be worth the potential harms in only two studies.
In nine out of the 18 studies, side effects such as headache, dizziness, transient local pain, tingling and numbness and nausea were reported in small numbers of patients. The use of morphine was more frequently associated with itching, nausea and vomiting. Rare but more serious complications of injection therapy have been mentioned in the literature, such as cauda equina syndrome, septic facet joint arthritis, discitis, paraplegia, paraspinal abscesses. Although the absolute frequency of these complications may be rare, these risks should be taken into consideration.
Based on these results, the review authors concluded that there is no strong evidence for or against the use of any type of injection therapy for individuals with subacute or chronic low-back pain.