Overall immediate success rates of ESI vary from 25% to
89%,5–7 with long-term results
falling to a mean of 80% by 6 months8 and
56% by 2 years.9 Ryan and Taylor found
that 77% of their patients experiencing symptoms for less
than 2 weeks obtained complete relief from epidural steroid injection,
whereas response rates varied from 72%, 60%, and
43% for patients experiencing pain for 4 weeks, 6 weeks,
and >6 weeks, respectively.6 White
et al found that epidural steroid injections were most effective
in patients with nerve root irritation manifesting as radicular
pain, dermatomal hypesthesia, weakness of muscle groups innervated
by the affected nerve roots, decreased deep tendon reflexes, and
diminished straight leg raise. They noted success rates at 6 months
for 34% of their patients with acute pain and 12% of
their patients with chronic pain, whereas their patients’ overall
success rate at 2 years was 1.3%.10 More
recently, Koes and Scholten examined 12 randomized clinical trials
looking at the efficacy of ESIs for low back pain and sciatica.
They found that 50% of the trials reported positive outcomes
and the other half reported negative results. Additionally, they
found that most of the studies involved had significant design flaws
that consequently invalidated the outcomes. Subsequently, they called
for additional studies, taking into account methodologic shortcomings
and focusing on determining which patients would most likely respond
to epidural steroid injections.11 Watts and Silagy
performed a formal meta-analysis on the same literature and concluded
that there was evidence for efficacy and safety in the use of epidural
steroid treatment for sciatica while acknowledging the shortcomings
of meta-analysis reviews on small trials.12 Carette
et al reported a randomized, placebo-controlled trial of epidural
steroids in 58 patients with documented disc herniation and found significant
pain relief and improved functioning at longer follow-up intervals.
As in previous similar studies, however, significant methodologic
flaws, including noncomparable placebo control and inadequate study
group size, likely affected outcome.13