Randomised and observational studies of the use of caudal epidural injections, with or without steroids, in patients with low back pain of at least three months duration were eligible for inclusion.
The primary outcome was pain relief which was classed as short term (less than six months) or long term (six months or more); secondary outcomes were functional and psychological improvement, return to work and opioid intake.
The included studies were mostly randomised double-blind trials, one was an equivalence trial, one a crossover trial, and the remaining studies were retrospective or prospective cohort studies. Caudal epidural injections varied but included lidocaine (0.5% or 1%), triamcinolone (40mg or 80mg), bupivacaine or prednisolone alone or in combination, compared with a placebo or different drug. Patients had pain resulting from disc herniation and radiculitis including sciatica with incapacitating chronic low back pain, lumbar nerve root; post-surgery syndrome after lumbar laminectomy or surgery, and surgery for a herniated disc; spinal or canal stenosis and discogenic pain (low back pain without disc herniation).
The authors did not report how many reviewers performed the study selection.